Thèses : « Abiotic stresse »

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Feilke, Kathleen. « Biochemical characterization of the plastid terminal oxidase and its implication in photosynthesis ». Thesis, Université Paris-Saclay (ComUE), 2015. http://www.theses.fr/2015SACLS051/document.

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L'oxydase terminale plastidiale (PTOX) est présente uniquement chez les organismesphotosynthétiques. PTOX oxyde le plastoquinol (PQH2) et réduit l'oxygène en eau.PTOX est impliquée dans la synthèse des caroténoïdes, dans le transportphotosynthétique d'électrons et dans la chlororespiration. De plus, son activité estconsidérée comme pouvant jouer un rôle en tant que soupape de sécurité, permettant de maintenir oxydé le pool de plastoquinones (PQ) et d'éviter la surréduction duchloroplaste et ainsi la photoinhibition. Chez la majorité des plantes testées, les niveaux de PTOX sont plus élevés dans des conditions de stress (une exposition à forte intensité lumineuse, par exemple). D'autre part, la surexpression de PTOX chez Arabidopsis thaliana n'a pas rendu les plantes moins sensibles à la photoinhibition. Par ailleurs, il semble que PTOX surexprimée chez Nicotiana tabacum a induit la génération des espèces réactives de l'oxygène (ERO) et une photoinhibition importante sous forte lumière.Le but de cette thèse était la caractérisation de l'activité enzymatique de PTOX enutilisant la protéine purifiée et de comprendre pourquoi PTOX protège du stressphotooxydant dans certaines conditions et pourquoi elle augmente ce stress quand elle est surexprimée in planta.L'analyse biochimique de PTOX recombinante purifiée a démontré que l'enzymeexiste principalement sous forme tétramérique. Cette forme se dissocie partiellement,principalement en dimères. Le turnover maximal de l'enzyme purifié correspond à 320électrons par seconde et par molécule de PTOX. Nous avons démontré que PTOXgénère des ERO dans une réaction secondaire dépendante de la concentration dusubstrat (PQH2) et du pH de la solution. À pH 8 (représentant le pH du stroma deschloroplastes actifs), PTOX a une activité antioxydante quand la concentration de PQH2 est basse et prooxydante quand cette concentration est élevée.En mesurant la fluorescence de la chlorophylle a, nous avons démontré quePTOX est active lorsqu'elle est ajoutée aux membranes enrichies en PSII.L'attachement aux membranes dépend du pH et de cations de la solution: lorsque le pHdiminue ou lorsque la solution est riche en cations monovalents, la quantité de PTOXattachée à la membrane diminue.L'activité de PTOX in planta et son effet sur le transport des électronsphotosynthétiques ont été analysés en utilisant Arabidopsis thaliana surexprimant laphytoène désaturase bactérienne (CRTI) et Nicotiana tabacum surexprimant PTOX1 deChlamydomonas reinhardtii. Arabidopsis thaliana surexprimant CRTI a un niveau plusimportant de PTOX et de production d'ERO et le transport cyclique des électrons estsupprimé chez les transformants. Cela implique que PTOX est en compétition avec letransfert cyclique pour les électrons du pool PQ et que PTOX joue un rôle importantdans le contrôle de l'état rédox de ce pool. En utilisant Nicotiana tabacum surexprimant PTOX1, nous avons démontré que PTOX fait concurrence au transfert linéaire d'électrons photosynthétique, mais que PTOX est inactivée quand le pH du stroma est neutre. Grâce aux résultats obtenus, nous proposons un modèle où l'association de PTOX avec la membrane est contrôlée par le pH du stroma. Quand le pH est neutre, PTOX est soluble et n'est pas active, ce qui évite l'interférence avec le transfert linéaire d'électrons. Quand le pH du stroma est alcalin et la chaîne des transporteurs photosynthétiques est surréduite (lors des conditions du stress), PTOX s'attache à la membrane, devient active et joue le rôle de soupape de sécurité
The plastid terminal oxidase PTOX is encoded by higher plants, algae and some cyanobacteria. PTOX is a plastid-localized plastoquinol (PQH2) oxygen oxidoreductase. PTOX was shown to be implicated in plant carotenoid biosynthesis, photosynthetic electron transport and chlororespiration and may act as a safety valve protecting plants against photo-oxidative stress. PTOX protein levels increase during abiotic stress indicating a function in stress acclimation. But overexpression of PTOX in Arabidopsis did not attenuate the severity of photoinhibition or, when overexpressed in tobacco, even increased the production of reactive oxygen species (ROS) and exacerbated photoinhibition.Biochemical analysis of recombinant purified PTOX (PTOX from rice fused to the maltose-binding protein) showed that the enzyme exists mainly as a tetramer, which dissociated to a certain extent during electrophoresis, mainly into a dimeric form. The PTOX activity was 320 electrons s−1 PTOX−1. It was also shown that PTOX generates ROS in a side reaction in a substrate (decylPQH2) and pH-dependent manner when liposomes were used: at the basic stromal pH of photosynthetically active chloroplasts, PTOX was antioxidant at low decylPQH2 gaining prooxidant properties with increasing quinol concentrations. It is concluded that PTOX can act as a safety valve when the steady state [PQH2] is low while a certain amount of ROS is formed at high light intensities.It was shown by chlorophyll a fluorescence that recombinant purified PTOX is active when added to photosystem II (PSII)-enriched membrane fragments. PTOX attached tightly to the PSII-enriched membrane fragments. The amount of PTOX attaching to the membrane depended on pH and salts: an alkaline pH and monovalent compared to divalent cations increased PTOX attachment.PTOX activity in planta and its effect on photosynthetic electron transport were investigated using Arabidopsis expressing bacterial phytoene desaturase and tobacco expressing PTOX1 from Chlamydomonas. Arabidopsis expressing bacterial phytoene desaturase (CRTI lines) showed a higher PTOX content and increased PTOX related ROS generation. Furthermore, cyclic electron flow was suppressed in these lines. This implicates that PTOX competes efficiently with cyclic electron flow for PQH2 in the CRTI-expressing lines and that it plays a crucial role in the control of the reduction state of the plastoquinone pool. Using tobacco expressing PTOX1 from Chlamydomonas, it was shown that PTOX competes efficiently with photosynthetic electron flow, but gets inactive when the stromal pH is neutral. Based on the in vitro and in vivo results, a model is proposed, where the association of PTOX to the membrane is controlled by the stromal pH: When the stromal pH is neutral, PTOX exists as a soluble form and is enzymatically inactive avoiding the interference of PTOX with linear electron flow. When the stromal pH is alkaline and the photosynthetic electron chain is highly reduced under stress conditions as high light, PTOX binds to the membrane, gets enzymatically active and can serve as safety valve

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CAVALLARO, VIVIANA. « SULFUR NUTRITION AND PARTITIONING IN RICE UNDER DIFFERENT STRESS CONDITIONS ». Doctoral thesis, Università degli Studi di Milano, 2021. http://hdl.handle.net/2434/881847.

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Sulfur (S) is an essential macronutrient required by plants for their correct development. This element is fundamental for the biosynthesis of different compounds, such as the two amino acids, cysteine (Cys) and methionine (Met), vitamins (biotin and thiamine), peptides involved in the response to abiotic stresses (glutathione - GSH, and phytochelatines - PCs), lipids and co-factors. Sulfate (SO42-) is the main S form taken up from soil by root system and then assimilated inside the cells during the sulfur reductive pathway. The uptake and the systemic movements of this anion are accomplished by the SULfate TRansporter (SULTR) gene family, which encode for H+/SO42- membrane co-transporters with different localization, amino acidic sequences, and affinity to sulfate. Since has been demonstrated that S has a key role in the response to different abiotic stresses (such as sulfur deficiency, heavy metal exposure or salt stress), the expression of these genes must be finely regulated, according to the different environmental conditions and requests for S reduced compounds. The general aim of the present thesis is the description of S systemic fluxes in rice in different stress conditions, to obtain more information about the contribution of S in determining plant tolerance to abiotic stresses. To achieve the goal, we also took advantage of analysis performed with an elemental analyzer coupled with an isotope ratio mass spectrometer (EA-IRMS), a powerful instrument which utilizes stable isotopes of elements as tracers. The entire research has been divided in three different parts. In the first work, potential 32S/34S isotope effects occurring during SO42- uptake were investigated in a closed hydroponic system in which a limited amount of substrate (SO42- in the nutrient solution) was continuously removed from the solution by the activity of the sulfate transporters of the root and converted in a final product (total S of the plant). An isotope discrimination against 34S occurred during SO42- uptake: plants had a lighter S isotope composition, and the residual SO42- in the hydroponic solution was enriched in heavy stable isotope. Fractionation during uptake showed two phases characterized by different fractionation factors, reflecting changes in the expression of the OsSULTR deputed to the root uptake which may explain the different isotope phenotypes observed during plant sulfate acquisition. Moreover, the possible 32S/34S isotope effects associated to both S partitioning and metabolism were investigated by comparing plants pre-grown in complete nutrient solutions and then continuously maintained on media containing SO42- (steady-state) or deprived of SO42- for 72h. The SO42- pool of the steady-state shoot was significantly 32S depleted with respect to the SO42- pools of root, while the organic S (Sorg) pools were significantly depleted in 34S compared to both the SO42- pool of both the organs and the S source. These results suggested a higher S assimilation in the aerial part of plants which favor the lighter isotope. Under S starvation, S assimilation progressively enriched the Sorg pools in the lighter 32S isotope and the residual SO42- in both the organs in the heavier 34S isotope. Most pronounced isotope separations were again observed in the shoot, confirming the prominent role of this organ in SO42- assimilation and S allocation. No fractionation due to translocation activity was observed. In the second part of the work, to validate the results previously obtained, we performed a mass balance study in rice plants exposed for 72h to different Cd concentrations, to investigate possible changes in S stable isotope fractionation due to this stress: in fact, adaptation of S metabolism has a pivotal role in responses to heavy metal exposure. As expected, Cd treatment strongly enhanced SO42- uptake and assimilation, as indicated by the analyses of the S pools (Stot, SO42-, and Sorg). S isotope analyses performed on the whole plants revealed changes in the S metabolism associated to variations in the discrimination against 34S, which was less evident as Cd concentration in the external medium increased. Transcriptional analysis suggested again that change of the ratio between relative transcripts of OsSULTR1;1 and OsSULTR1;2, as observed for S starvation, may be responsible for the progressive decreased in 34S isotope discrimination. The important role of shoot in S assimilation was confirmed: isotope fractionation associated to sulfate assimilation was higher in shoot than in root, and progressively increased as Cd concentration did. The last part of work was focused on fully characterize, under hydroponics-controlled conditions in the absence or in the presence of salt stress (80 mM NaCl), the phenotypic behavior in the already available salt tolerant introgression line (IL) Onice 11 (O11), obtained by Marker-Assisted Back-Cross (MABC) selection starting from the cross between the Italian japonica elite cultivars Onice (sensitive recurrent parent) and the indica variety IR64-SalTol (tolerant), donor of the major QTL SalTol. Moreover, S acquisition and metabolism of O11 and both the parental lines were evaluated to investigate their possible implication in determining the different tolerance to salt stress. Results showed the beneficial effect of the introgression of the SalTol QTL from the indica variety into selected japonica rice line, based on different characteristics of selected phenotypic-biochemical-physiological parameters. However, salt stress strongly affected S uptake and assimilation, and we can reasonably suppose that these features do not justify the different salt tolerance in the considered IL O11. In conclusions, rice plants can discriminate against 34S during SO42- uptake and assimilation. Between plants organs, shoot represents the predominant one involved in S assimilation. Abiotic stresses, such as S starvation or Cd exposure, lead to changes in the ratio of relative transcripts between the OsSULTRs involved in the uptake of sulfate, and this may be the cause of the different isotope phenotypes observed. Finally, salt tolerance in the IL O11 appears to not be dependent on different S metabolism.

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Berenguer, Helder Duarte Paixão. « Eucalyptus predisposition to Neofusicoccum kwambonambiense under water stress ». Master's thesis, Universidade de Aveiro, 2016. http://hdl.handle.net/10773/22330.

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Mestrado em Biologia Molecular e Celular
In Portugal, Eucalyptus, particularly Eucalyptus globulus, occupies more than 800 000 ha and, due to being a major source of biomass for fiberboard, industrial charcoal, fuel wood and paper pulp, has become a key genus, with a considerable economic importance. However, E. globulus productivity faces new pressures, with climate change-driven drought as one of the most hostile ones. Drought can lead to growth impairment and yield reduction: directly; or indirectly, through the increase of plant susceptibility to pathogens by a predisposition mechanism. Neofusicoccum kwambonambiense is an endophytic opportunist phytopathogen known to severely affect E. globulus, whose incidence has already been reported in Portugal. Taking all in consideration, it is of major importance to assess the predisposition effect that drought may have on the N. kwambonambiense - E. globulus interaction. For such purpose, four treatment groups were established: E. globulus were firstly subjected to a 66-days acclimation period in which plants were periodically watered (80% of field capacity). After that, two groups were exposed to a progressive water supply restriction. The other two remained well-watered. Once water-stressed plants achieved 18% of field capacity (23 days), a well-watered and a water-stress group were inoculated with N. kwambonambiense. All treatments were kept in these conditions throughout a 65 days’ period, at which moment a set of morphological, physiological and biochemical parameters was obtained. Well-watered plants, despite being infected with N. kwambonambiense, presented an overall photosynthetic increase, which enabled plant defense through the production of sugars, proline and salicylic acid. Oxidative damages (partially observed through malondialdehyde content), were avoided in part due to proline and soluble sugars. Water stress lead to a direct growth impairment confirmed through an indole-acetic-acid content decrease. A water-potential reduction occurred, which, together with abscisic acid, lead to stomatal closure and overall photosynthetic efficiency decline. Oxidative damages weren’t properly managed and further affected E. globulus. Furthermore, N. kwambonambiense was found to promote a jasmonic acid content increase, typical of necrotrophic pathogens, which may suggest a lifestyle change from hemibiotrophic to necrotrophic as plant cells progressively degenerate. Ultimately, water-stressed E. globulus presented larger external lesion extensions and steam cankers and a superior internal fungi progression. Our results conclusively demonstrate that water stress created a better substrate for fungi development and decreased the plant’s ability to respond. Such resulted in higher susceptibility and disease severity confirming predisposition.
Em Portugal, o eucalipto, particularmente o Eucalyptus globulus, ocupa mais de 800 000 ha. Devido a ser uma importante fonte de biomassa para painéis de fibras, carvão industrial, lenha e pasta de papel, tornou-se um género chave de considerável importância económica. Contudo, a produtividade de E. globulus tem encontrado novas pressões, sendo a seca resultante das alterações climáticas, uma das mais hostis. A seca pode levar a uma diminuição do crescimento e produtividade: diretamente; ou indiretamente através do aumento da suscetibilidade a agentes patogénicos através da predisposição. O fungo ascomiceto Neofusicoccum kwambonambiense é um agente fitopatogénico endofítico oportunista que se sabe afetar severamente E. globulus, e cuja presença já fora confirmada em Portugal. Tomando tal em consideração, torna-se importante avaliar o efeito de predisposição que a seca poderá ter na interação N. kwambonambiense - E. globulus. Para tal foram criados quatro grupos de tratamento: E. globulus foram primeiramente sujeitos a um período de aclimatização de 66 dias no qual foram periodicamente irrigados (80% de capacidade de campo). Seguidamente, dois grupos foram sujeitos a uma diminuição progressiva da irrigação. Os outros dois grupos permaneceram bem regados. Uma vez que os tratamentos stressados atingiram 18% de capacidade de campo (23 dias), um grupo bem regado e um grupo stressado foram inoculados com N. kwambonambiense. Todas os tratamentos foram mantidos nestas condições durante um período de 66 dias, findo o qual foi obtido um conjunto de parâmetros morfológicos, fisiológicos e bioquímicos. As plantas bem regadas, apesar de terem sido inoculadas com N. kwambonambiense apresentaram um aumento dos parâmetros fotossintéticos o que terá permitido a defesa da planta através de uma produção amplificada de açúcares, prolina e ácido salicílico. Danos oxidativos (parcialmente observados através do conteúdo em malondialdeído) foram evitados, em parte, devido à ação da prolina e açúcares solúveis. O stress hídrico levou a uma diminuição do crescimento confirmado pela redução do conteúdo em ácido-indole-acético. Ocorreu uma diminuição do potencial hídrico, a qual, em conjunto com o aumento do ácido abscísico, levou ao fecho dos estomas e diminuição da fotossíntese. Os danos oxidativos não foram controlados, afetando o estado do E. globulus. Ademais, o N. kwambonambiense provocou um aumento do conteúdo em ácido jasmónico, típico de agentes patogénicos necrotróficos, o que poderá sugerir que o fungo passou de um estilo de vida hemibiotrófico para necrotrófico, à medida que as células degeneravam. Os E. globulus stressados apresentavam maiores lesões externas e cancros, conjuntamente com uma maior progressão interna do fungo. Os nossos resultados comprovam que a seca criou um melhor substrato para o desenvolvimento do fungo e diminuiu a capacidade de resposta da planta. Tal resultou num aumento da suscetibilidade e severidade da doença confirmando a predisposição.

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RICCI, SARA. « Study of biotic and abiotic stresses in Solanaceae by metabolic and proteomic approaches ». Doctoral thesis, Università di Foggia, 2017. http://hdl.handle.net/11369/363315.

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Malinoshevska, M. « Biofilm formation in abiotic stress environment ». Thesis, Київський національний університет технологій та дизайну, 2019. https://er.knutd.edu.ua/handle/123456789/13386.

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Silva, Ana Luísa Patrício. « Impact of natural and/or chemical stressors on the freeze-tolerant and euryhaline enchytraeid, Enchytraeus albidus ». Doctoral thesis, Universidade de Aveiro, 2015. http://hdl.handle.net/10773/16009.

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Doutoramento em Biologia
Rapid climatic changes are taking place in Arctic, subarctic and cold temperate regions, where predictions point to an increase in freeze-thaw events, changes in precipitation, evaporation and salinity patterns. Climate change may therefore result in large impacts in ecosystem functioning and dynamics, especially in the presence of contaminants due to intense anthropogenic activities. Even though multiple stress approaches have received increasing interest in the last decades, the number of such studies is limited. In particular, knowledge on the effect of freezethaw events and salinity fluctuations on ecotoxicology of soil invertebrates is lacking, especially important when considering supralittoral species. Therefore, the aim of this thesis was to investigate the effects of low temperature and salinity fluctuations, singly and in combination with contaminants, in the freeze-tolerant and euryhaline enchytraeid Enchytraeus albidus. The assessment of population level endpoints (survival and reproduction), along with physiological and biochemical parameters such as levels of cryoprotectants, ice/water content, oxidative stress biomarkers, cellular energy allocation, and tissue concentration of chemicals (when applied), provided new and valuable knowledge on the effects of selected physical and chemical stressors in E. albidus, and allowed the understanding of adjustments in the primary response mechanisms that enable worms to maintain homeostasis and survival in harsh environments such as polar and temperate-cold regions. The presence of moderate levels of salinity significantly increased freeze-tolerance (mainly evaluated as survival, cryoprotection and ice fraction) and reproduction of E. albidus. Moreover, it contributed to the readjustments of cryoprotectant levels, restoration of antioxidant levels and changed singnificantly the effect and uptake of chemicals (copper cadmium, carbendazim and 4-nonylphenol). Temperature fluctuations (simulated as daily freeze-thaw cycles, between -2ºC and -4ºC) caused substancial negative effect on survival of worms previsouly exposed to non-lethal concentrations of 4-nonylphenol, as compared with constant freezing (-4ºC) and control temperature (2ºC). The decrease in cryoprotectants, increase in energy consumption and the highest concentration of 4-nonylphenol in the tissues have highlighted the high energy requirements and level of toxicity experienced by worms exposed to the combined effect of contaminants and freezing-thawing events. The findings reported on this thesis demonstrate that natural (physical) and chemical stressors, singly or in combination, may alter the dynamics of E. albidus, affecting not only their survival and reproduction (and consequent presence/distribution) but also their physiological and biochemical adaptations. These alterations may lead to severe consequences for the functioning of the ecosystems along the Arctic, subarctic and cold temperate regions, where they play an important role for decomposition of dead organic matter. This thesis provides a scientific basis for improving the setting of safety factors for natural soil ecosystems, and to underline the integration of similar investigations in ecotoxicology, and eventually in risk assessment of contaminants.
As alterações climáticas estão a atingir rapidamente as regiões do Ártico, SubÁrtico e as regiões temperadas, apontando as previsões para um aumento de eventos de congelamento-descongelamento, bem como mudanças nos padrões de precipitação, evaporação e de salinidade. Estas alterações climáticas poderão resultar em impactos francamente negativos no funcionamento e dinâmica de ecossistemas, especialmente quando associados à presença de contaminantes resultantes da intensa atividade antropogénica. Embora a incorporação de stressores múltiplos em estudos de ecotoxicidade tenha recebido um crescente interesse pela comunidade científica, o seu número é ainda reduzido. Particularizando, o conhecimento dos efeitos de eventos de congelamento-descongelamento e de flutuações de salinidade permanecem desconhecidos, especialmente quando se consideram espécies supra-litorais. Neste contexto, o objetivo geral da presente tese consistiu em investigar os efeitos das flutuações de temperaturas e salinidade, individualmente ou em combinação com contaminantes, no enquitraídeo tolerante ao frio e eurialino - o Enchytraeus albidus. A avaliação de parâmetros populacionais (sobrevivência, reprodução e bioacumulação), fisiológicos (níveis de crioprotetores, conteúdo em gelo / água, temperatura de fusão e sobrecongelamento) e bioquímicos (biomarcadores de stress oxidativo, alocação de energia celular) permitiu compilar novas e valiosas informações sobre os efeitos dos stressores físicos e químicos selecionados no enquitraídeo e compreender quais os reajustes nos mecanismos de resposta primários que lhes permitem manter a homeostasia e sobrevivência em ambientes inóspitos como as regiões Polares e temperadas-frias. A presença de níveis moderados de salinidade aumentou significativamente a tolerância a temperaturas congelantes (essencialmente avaliada como sobrevivência, crioprotecção e fracção de gelo extracelular) e a reprodução do E. albidus. Além disso, contribuiu para a regulação de crioprotectores, restauração dos níveis de antioxidantes nestes organismos e alterou significativamente o efeito e a incorporação/absorção de substâncias químicas (cádmio, cobre carbendazim e 4-nonilfenol). As flutuações de temperatura (simuladas como ciclos diários de congelamento-descongelamento, com temperaturas entre 2ºC e -4ºC) causaram um efeito substancialmente negativo na sobrevivência de organismos previamente expostos a concentrações não letais de 4-nonilfenol, quando comparados com organismos expostos a uma temperatura congelante constante (-4ºC) ou à temperatura controlo (2ºC). A diminuição na crioproteção, o aumento no consumo de energia e a maior concentração de 4-nonilfenol nos tecidos vieram sublinhar o elevado gasto energético e o nível de toxicidade sofrido pelos organismos expostos à combinação de contaminantes e eventos de congelamento e descongelamento. Os resultados apresentados nesta tese demonstram, assim, que a presença de stressores naturais (físicos) e químicos, isoladamente ou em combinação, podem alterar a dinâmica do E. albidus, afetando não só a sua sobrevivência e reprodução (e consequente presença / distribuição), mas também as suas adaptações fisiológicas e bioquímicas. Essas alterações podem levar a consequências graves para o funcionamento dos ecossistemas do Ártico, subÁrtico e regiões temperadas-frias, uma vez que estes organismos desempenham um papel importante para a decomposição de matéria orgânica morta. Esta tese fornece ainda uma base científica para melhorar a atribuição de coeficientes de segurança para os ecossistemas naturais do solo, alertando para a integração de investigações semelhantes em ecotoxicologia, e, eventualmente, para a avaliação de risco ecológico de contaminantes.

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Escalante, Pérez María. « Poplar responses to biotic and abiotic stress ». kostenfrei, 2009. http://nbn-resolving.de/urn/resolver.pl?urn=nbn:de:bvb:20-opus-46893.

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Armeanu, Katrin. « Acclimation of cotton (gossypium) to abiotic stress ». Thesis, Bangor University, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.273551.

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Coelho, Susana. « Abiotic stress signalling in the fucus embryo ». Thesis, University of Plymouth, 2002. http://hdl.handle.net/10026.1/2762.

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Fucoid algae live in the intertidal region where they experience daily fluctuations in light and external osmotic environment. High light, especially in combination with ultraviolet (UV) radiation and hyper-osmotic stress affected the cellular physiology of Fucus embryos. Two photoinhibition responses were recognised. Firstly, a rapid decline of the photosystem II (PSII) efficiency, linked with the operation of the xanthophyl cycle, followed by a slower decline correlated with reactive oxygen species (ROS) production. As a result of enhanced ROS production, a slower repair of the PSII efficiency was observed, particularly with increased UV-B doses. Development of the embryos was transiently affected by UV-B. The cellular signal transduction pathway during hyper-osmotic stress was investigated. ROS production in response to hyperosmotic stress comprised two distinct components. The first ROS component coincided closely with the origin of a Ca2+ wave in the peripheral cytosol at the growing cell apex, had an extracellular origin, and was necessary for the Ca2+ wave. Patch clamp experiments showed that a non-selective cation channel was stimulated by H2O2, and may underlie the initial cytosolic Ca2+ elevation. The spatio-temporal pattern of the Ca2+ wave was thus determined by peripheral ROS production. The second, later ROS component localised to the mitochondria and was a direct consequence of the Ca2+ wave. The first, but not the second component was required for short-term adaptation to osmotic stress, probably through the activity of cell wall bromoperoxidases. Mitogen-activated protein kinases may be involved in the hyper-osmotic stress response downstream or independently of the mitochondrial ROS production.

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Karim, Sazzad. « Exploring plant tolerance to biotic and abiotic stresses / ». Uppsala : Dept. of Plant Biology and Forest Genetics, Swedish University of Agricultural Sciences, 2007. http://epsilon.slu.se/200758.pdf.

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Jain, Ritu Shree. « Rice response to simultaneous biotic and abiotic stresses ». Thesis, University of Leeds, 2013. http://etheses.whiterose.ac.uk/6415/.

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With the predicted climate change and an ever-growing population there is increasing pressure to develop crop plants with improved stress responses, increased yield and high nutritive value. We have explored transcriptomic changes in the leaves and roots of rice plants (Oryza sativa japonica cv Nipponbare) in response to drought and the root-knot nematode Meloidogyne graminicola. A glasshouse model was developed to mimic conditions experienced by rice plants in the field. The plant responses under simultaneous biotic and abiotic stress were dominated by the drought element accompanied by a unique set of genes that were only responsive to the simultaneous stress. Highlighted within this group were novel members of stress-responsive gene families for example cytochrome P450, wall-associated kinases, lipid transfer proteinlike proteins and new candidate genes that may play important roles in the response of rice to multiple stresses. The genes that were differentially regulated between the multiple and the drought stress treatment were explored using loss-of-function mutants. The loss-of-function mutant for peroxidase precursor gene (per) showed improved growth and yield compared to the wildtype Nipponbare plants. The experiments conducted in growth rooms were validated in a field study. Both Nipponbare rice plants, and the popular lowland indica rice cv IR64 were grown under prolonged vegetative drought stress accompanied by cyst nematode or root-knot nematode infection. Reduction of phytate, an anti-nutrient, has been adopted as a major strategy to improve the nutritional value of crop plants. Nematode susceptibility of low phytate Arabidopsis plants was studied to determine the effect of reduced phytate content on the plant’s defence response. The study has provided insight into the genome-wide transcriptional changes in rice under a combined biotic and abiotic stress. It has led to better understanding of the stress responses in plants that will be advantageous in developing crop varieties with improved yield and nutritive value.

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Amara, Imen. « Abiotic stress in plants : Late Embryogenesis Abundant proteins ». Doctoral thesis, Universitat de Barcelona, 2012. http://hdl.handle.net/10803/83820.

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In order to improve our understanding on LEA proteins and their molecular functions in drought tolerance, the present work analyzes in the first place, the composition of LEA subproteomes from Arabidopsis seeds and maize embryos; second, three maize embryo LEA proteins from groups 1, 2, and 3 are analyzed in order to detect functional differences among them and finally, transgenic maize plants over-expressing group 5 “rab28” lea gene are characterized. The following results are presented: - Chapter 1. Proteomic approach to analyze the composition of LEA subproteomes from Arabidopsis seeds by mass spectrometry. The main objective was the development and isolation method to obtain enriched LEA populations from Arabidopsis seeds. LEA subproteomes were obtained using an extraction procedure that combines heat stability and acid solubility of LEA proteins. To identify the protein content, we followed two approaches: first, a classical 1D (SDSPAGE) gel-based procedure associated with MS analysis using an electrospray ionization source coupled on-line to liquid chromatography (LC-ESI-MSMS) and second, a gel-free protocol associated with an off-line HPLC and analysis via matrix assisted laser desorption/ionization (LC-MALDI-MSMS). - Chapter 2. Proteomic analysis of LEA proteins accumulated in maize mature seeds. Identification of LEA protein content by mass spectrometry and selection of three LEA proteins, Emb564, Rab17 and Mlg3, as representatives of groups 1, 2 and 3 for further study. Comparative functional analysis covering different aspects of maize Emb564, Rab17 and Mlg3 proteins, posttranslational modifications, subcellular localization and their properties in in-vitro and in- vivo assays. - Chapter 3. Characterization of transgenic maize plants expressing maize group 5 rab28 LEA gene under the ubiquitin promoter. Evaluation of Rab28 transcripts and protein levels, phenotype and stress tolerance traits of transgenic plants under drought stress. Investigation of the subcellular localization of transgenic and wild-type Rab28 protein using immunocytochemical approaches.
Las proteínas LEA, originalmente fueron descritas en las semillas de algodón; se acumulan en grandes cantidades en estructuras tolerantes a la desecación (semillas, polen) y en tejidos vegetativos sometidos a estrés abiótico, sequía, salinidad y frío. También se hallan en organismos anidrobióticos, en plantas de resurrección, algunos invertebrados y microorganismos. La presencia de proteínas LEA se correlaciona con la adquisición de tolerancia a la desecación. Desde un principio se les atribuyó un papel en las respuestas de las plantas en la adaptación al estrés (revisado en Bartels and Salamini 2001, Tunnacliffe 2007, Shih et al. 2010, Tunnacliffe 2010, Hand et al. 2011). Las proteínas LEA se clasifican en diversos grupos en función de dominios y secuencias de aminoácidos específicos (Wise 2010, Batagglia et al 2008, Bies-Ethève et al 2008). Los grupos 1, 2 y 3 son los más relevantes ya que abarcan la mayoría de las proteínas de la familia LEA. Una característica general de estas proteínas es su elevada hidrofilicidad, alto contenido de aminoácidos cargados y su falta de estructura en estado hidratado. A pesar de encontrarse mayoritariamente en forma de “random coil”, algunas adquieren un cierto grado de estructura durante la deshidratación o en la presencia de agentes promotores de α-hélices (Shih et al. 2010, Hand et al. 2011). A nivel celular se han hallado en todas las localizaciones, citosol, núcleo, nucleolo, mitocondria, cloroplasto, vacuola, retículo endoplásmico, peroxisoma y membrana plasmática, donde se supone ejercen su función protectora frente al estrés (Tunnacliffe and Wise 2007, Hundertmark and Hincha 2008). En relación a las modificaciones post-traduccionales, algunas se hallan fosforiladas (Jiang and Wang 2004; Plana et al. 1991, Heyen et al. 2002, Rohrig et al. 2006). Los efectos protectores de las varias proteínas LEA se han demostrado mediante ensayos in vitro y en aproximaciones transgénicas que han dado lugar a fenotipos resistentes a la sequía, sal y frío. Por lo general, se considera que estas proteínas contribuyen a la protección y a la estabilización de macromoléculas y estructuras celulares en las respuestas de adaptación al estrés en plantas; sin embargo, sus funciones específicas aún no han sido esclarecidas. A nivel molecular se ha propuesto que las funciones de las proteínas LEA pueden ser variadas: estabilización y renaturalización de proteínas, mantenimiento de membranas, en combinación, o no, con azúcares, tampones de hidratación (substitución de moléculas de agua), afinidad por iones y función antioxidante (Tunnacliffe and Wise 2007, Shih et al. 2010, Batagglia et al. 2008). Para finalizar, diremos que los objetivos principales de esta tesis consisten en ampliar los conocimientos sobre las proteínas LEA y sus funciones relativas a la tolerancia a la sequía. Los resultados están presentados en forma de capítulos.

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Muilu-Mäkelä, R. (Riina). « Polyamine metabolism of Scots pine under abiotic stress ». Doctoral thesis, Oulun yliopisto, 2015. http://urn.fi/urn:isbn:9789526210582.

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Abstract Changes in climate will impose abiotic stress on plant species, and eventually affect their distributional range. This is a particular challenge especially to tree species with long generation times and slow rates of evolution. In the boreal zone, most of these species also hold high economic value. The aim of the study was to enhance understanding of the abiotic stress coping strategies of Scots pine (Pinus sylvestris L.) in its vulnerable early growth phase. In particular, the study evaluates the role of polyamine (PA) metabolism of Scots pine under abiotic stress. Polyamines (PAs) are small, ubiquitous nitrogenous compounds involved in fundamental biological processes of plants such as growth, organogenesis, embryogenesis and abiotic and biotic stress defence. The effects of different water availabilities and spring frost temperatures on shoots and roots of young seedlings were investigated in two growth chamber experiments. Proembryogenic liquid cell culture system was established and used as a controllable platform. Effects of polyethylene glycol (PEG) induced osmotic stress was investigated at the cellular level in liquid cultures. Responses to treatments were evaluated by quantifying changes in the expression of PA metabolism, stress, cell death and cell division -related genes, metabolite concentrations, as well as stress-induced physiology and morphology. The results revealed that PA metabolism is tissue specific and strictly regulated. Drought stress induced the accumulation of putrescine (Put) in photosynthesizing tissues, whereas the prime response to spring frost was a reorganization of root growth. Generally, drought and osmotic stress decreased the expression of PA catabolizing genes, leading to consistent PA levels in tissues even under severe stress. To conclude, PAs have a protective role in maintaining the growth and development of pine tissues subjected to abiotic stress
Tiivistelmä Ilmastonmuutos vaikuttaa eri kasvilajien levinneisyyteen. Nopeasti muuttuva ilmasto on haaste erityisesti metsäpuulajeille, jotka pitkän sukupolvenvälin takia kehittyvät evolutiivisesti hitaasti. Erilaisten ympäristötekijöiden aiheuttamien puolustusaineenvaihdunnan muutosten tunteminen metsäpuilla on tulevaisuuden kannalta myös taloudellisesti tärkeää. Työn tavoitteena oli selvittää millainen merkitys polyamiineilla on metsämännyn (Pinus sylvestris L.) abioottisessa stressivasteessa. Polyamiinit (PAt) ovat pienimolekyylisiä typpiyhdisteitä, joiden tiedetään olevan mukana solujen perusaineenvaihdunnassa, kasvien kasvussa ja kehityksessä ja stressivasteissa. Tutkimus koostuu kolmesta kokeesta, joissa selvitettiin PA aineenvaihduntaa osana männyn taimien ja erilaistumattomien somaattisista alkioista peräisin olevien soluviljelmien stressivasteita. Kahdessa kokeellisessa tutkimuksessa männyn sirkkataimia altistettiin erilaisille kasvualustan vesipitoisuuksille ja keväthallan lämpötilaolosuhteille. Kolmannessa kokeessa PA aineenvaihdunnan reagointia osmoottiseen stressiin tutkittiin erilaistumattomissa somaattisissa epäkypsissä männyn alkiosta peräisin olevissa solukoissa kontrolloidussa nesteviljely-ympäristössä. Tutkimuksessa tarkastelin PA aineenvaihduntaa säätelevien geenien ilmenemistä ja PA pitoisuuksien muutoksia suhteessa kasvuun, kehitykseen ja stressissä indusoituvien geenien ilmenemiseen. Tulokset osoittavat, että PA aineenvaihdunta on tiukasti säädeltyä erilaisissa solukoissa. Taimien yhteyttävät solukot kerryttivät putreskiinia (Put) kuivuudessa. Ensimmäiset vasteet keväthallaolosuhteisiin havaittiin muutoksena juurten kasvun säätelyssä. Sekä kuivuus että osmoottinen stressi laskevat PA hajottavien geenien ilmenemistä, mikä on metsämännyn tapa ylläpitää tasaiset PA pitoisuudet solukoissa stressitekijöistä huolimatta. Johtopäätöksenä voidaan todeta, että PA aineenvaihdunta on tärkeä metsämännyn kasvun ja kehityksen kannalta

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Nylander, Maria. « Molecular responses to abiotic stress in Arabidopsis thaliana / ». Uppsala : Swedish Univ. of Agricultural Sciences (Sveriges lantbruksuniv.), 2000. http://epsilon.slu.se/avh/2000/91-576-5766-1.pdf.

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Ali, Mohammed Shamsher. « Molecular analysis of plant acclimation to abiotic stress ». Thesis, University of Newcastle Upon Tyne, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.250106.

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Gonçalves, Nuno M. « Insights into the rice response to abiotic stress : ». Doctoral thesis, Universidade Nova de Lisboa, Instituto de Tecnologia Química e Biológica António Xavier, 2019. http://hdl.handle.net/10362/95814.

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"Abiotic stress is one of the biggest threats to food security worldwide, enhanced by a changing global climate and the alarming gap in crop productivity to face population growth. Rice (Oryza sativa) is one of the top staple food crops worldwide, along with wheat and maize, and is also one of the most susceptible monocots to abiotic stress, such as salinity, with moderate stress leading to up to 90% production losses."
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Abeykoon, Walawwe Sashila. « Regulation of photosynthesis in plants under abiotic stress ». Thesis, University of Manchester, 2014. https://www.research.manchester.ac.uk/portal/en/theses/regulation-of-photosynthesis-in-plants-under-abiotic-stress(25e36741-2b94-49e9-a660-487b913fd123).html.

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Most plants complete their life cycle in a single location and therefore are affected by the changing environment. As a result, plants have evolved physiological and developmental adaptations to overcome stress. The work presented in this thesis has examined the regulation of photosynthetic electron transport in barley, rice and Thellungiella salsuginea. Barley is considered as a crop which is comparatively tolerant to soil salinity. The focus of this study was to evaluate the physiological responses of photosynthesis in barley under salinity and to characterize traits responsible for the regulation of photosynthesis. At low salt concentrations, barley plants protect PSII centres from excitation pressure by down-regulating the electron transport chain and maintaining ΔpH, by cyclic electron transport associated with PSI, to support nonphotochemical quenching (NPQ). However, at the highest concentration of salt examined, this regulation starts to fail. The failure might result from a specific loss of PSI, resulting in reduced cyclic electron flow, or an increase in the leakiness of the thylakoid membranes, resulting in loss of ΔpH. The effects of salinity on the regulation of electron transport through Photosystem I and Photosystem II have been studied in two rice varieties from Sri Lanka. The regulation of photosynthesis in the salt-tolerant At-354 is more prominent than in the salt-sensitive Bg-352 when plants are exposed to salt. Exposure of Bg-352 to salt resulted in a substantial decrease in gas exchange, PSII photochemistry, leaf area and loss of chlorophylls. The decrease in the photosynthesis in AT-354 is caused by stomatal limitations, which restrict the CO2 entry into the plants, whereas the decrease of photosynthesis in Bg-352 is caused by non-stomatal limitations. Results suggest that At-354 protects PSII centres from excitation pressure by down-regulating the electron transport chain and maintaining ΔpH by cyclic electron transport associated with PSI to support NPQ. At high salt concentration, this regulation starts to fail in Bg-352.Tolerance to abiotic and biotic stress has evolved in many wild plant species, termed extremophiles. These plants contain essential genes which may used to improve crop production in changing environments. Thellungiella salsuginea is an extremophile, able to grow and reproduce in extreme environments. Stepien and Johnson (2009) identified a protein, known as the plastid terminal oxidase (PTOX) which acts as an alternative electron sink in T. salsuginea under salt stress. The current study showed that, in addition to salt, T. salsuginea showed increases in PTOX protein content and activity when exposed to drought, different growth irradiances and cold with high light. Semi-natural conditions also triggered the activity of PTOX. This study also showed that salt caused an up-regulation of PTOX gene transcripts in the leaves of salt treated T. salsuginea plants compared to control plants. Direct electron transport from PSII to PTOX and then to oxygen via the PQ pool accounted for up to 30% of total PSII electron flow in T. salsuginea (Stepien and Johnson, 2009). Efficient electron flow from PSII to PTOX would however, probably require co-location of these complexes in the same thylakoid fraction. To examine the location of PTOX in the thylakoid membrane, immunoblot analyses were performed, to test for changes in other protein complexes which may be associated with PTOX. In addition blue-native polyacrylamide gel electrophoresis and immunoblots were performed to isolate and detect the PTOX protein with any associated complexes. Although immunoblot analysis showed a prominent signal, mass spectrometry data did not allow identification of PTOX. This results suggests that further studies are needed to identify the precise localisation of the PTOX protein in the thylakoid membranes in T. salsuginea.

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Madeo, M. « MEDICINAL PLANT RESPONSE TO ABIOTIC AND BIOTIC STRESS ». Doctoral thesis, Università degli Studi di Milano, 2010. http://hdl.handle.net/2434/150114.

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Medicinal plants have always been considered a rich source of secondary metabolites that promote human health. Quality and property of medicinal plants strictly depend on secondary metabolites profile. They also play important roles in plant physiological processes and in ecological systems. The environment exerts a selective pressure on plants and these molecules actively participate to the plant response and adaptation. Amongst secondary metabolite, the phenolic compounds possess properties able to prevent oxidative stress. Therefore, an enhancement of the amount of phenolic compounds can be observed under different environmental factors. With this project we aimed to study the phenolic compounds of the medicinal plant Achillea collina Becker ex Rchb. cv “SPAK”, and their implication in physiological and biochemical response to abiotic and biotic stresses. We seek the possibility to increase the synthesis of phenolics with health properties or useful as potential control agents of insect pests. Abiotic stress. Hydroponic culture was used to evaluate the effect of long-term mineral, nitrogen starvation (abiotic stress) in A. collina. By means of HPLC-DAD-ESI/MS and NMR techniques, the content and the qualitative profile of A. collina methanol soluble phenolics, were evaluated. We concluded that the methanol extracts of A. collina leaves and roots are rich in hydroxycinnamic acids such as chlorogenic acid (2.33 ± 0.3 mg g-1 Dw), 3,5-di-O-caffeoylquinic acid (10.7 ± 4.2 mg g-1 Dw) and 4,5-di-O-caffeoylquinic acid (0.88 ± 0.24 mg g-1 Dw). The content of hydroxycinnamic acids significantly increased in plants growth under mineral nitrogen starvation, respect to the control plants. Chlorogenic acid increased by 2.5 and 3-fold and 3,5-di-O-caffeoylquinic acid increased by 8.5 and 35-fold in leaves and root, respectively. Biotic stress. A. collina plants cultivated in soil were infested with the phloem feeders aphids. We set up the system (e.g., age of plant, type of the cage, number of insects per plant, duration of infestation) to co-cultivated the plants with specialist (Macrosiphoniella millefolii) and generalist (Myzus persicae Sulzer) aphids. Plant growth, water and total protein content were evaluated. Based on a preliminary assessment of phenolic fingerprint, further extractions and separations were performed on A. collina leaves, to obtained soluble and cell wall-bound fractions and their sub-classes. Our results showed that A. collina plants were strongly affected by aphid infestation. Twenty days after infestation, the fresh weight was twenty-fold and seven-fold increased, in control and infested plants. Water and protein content, condensed tannins and methanol soluble phenolics content, were not affected by the aphid infestation. Cell wall-bound phenolics content increased in infested plants. The main phenolics were found to be chlorogenic acid and 3,5-di-O-caffeoylquinic in methanol soluble fraction, and caffeic acid in cell wall fraction. The chromatographic profiles showed that the main hydroxycinnamic acids were present in control and in both M. persicae and M. millefolli infested plants. The quantitative analysis indicated that the levels of chlorogenic acid and 3,5-di-O-caffeoylquinic acid, were 44% and 37% higher in M. persicae infested plants, respectively. The levels of chlorogenic acid and 3,5-di-O-caffeoylquinic acid, were 27% and 39% higher in M. millefolli infested plants, respectively. Twenty days after infestation the content of caffeic acid was resulted 43% and 34% higher in M. persicae and M. millefolli infested plants, respectively. These differences should indicate the different evolutionary interaction between plant and generalist/specialist aphid. We hypotheses that the increase of these molecules may represent a plant resistance mechanism against aphid attack. Finally, a chemometric approach, by means multivariate statistical analysis, was applied on chromatogram profiles to verify whether there is difference between methanol soluble fraction of infested and non infested A. collina plants. The discriminant analysis showed a significant effect of phloem feeders aphids on soluble phenolic compounds and indicated two peaks, not yet identified, that separate control from infested plants. In conclusion the model system developed to cultivate A. collina was useful to understand the metabolic basis of the environment interactions. The main hydroxycinnamic acids identified, were resulted increased in both abiotic and biotic stress, suggesting their implication in A. collina protection to environmental controversies.

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Rosa, Margarida T. Gomes. « Unveiling the regulatory mechanisms behind SUMOylation to improve rice abiotic stress response ». Doctoral thesis, Universidade Nova de Lisboa, Instituto de Tecnologia Química e Biológica António Xavier, 2019. http://hdl.handle.net/10362/97998.

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"Climate change is one of the biggest concerns worldwide due to its effect on many physical and biological systems. Intense episodes of drought, heat, cold, and high salinity are becoming more frequent, compromising crop productivity. Thus, it is crucial to equip the plants with tools that will allow them to grow in such erratic/sub-optimal climate conditions. In order to achieve these biotechnological improvements, it is of utmost importance to understand the molecular mechanisms governing stress tolerance in crops, such as rice.(...)"
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Green, Andrew Justin. « Abiotic stress tolerance from the tertiary gene pool of common wheat ». Diss., Kansas State University, 2016. http://hdl.handle.net/2097/32746.

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Doctor of Philosophy
Department of Agronomy
Allan K. Fritz
Heat and drought stress are two of the most significant abiotic stresses limiting wheat production in the Great Plains and worldwide. Introgression of novel tolerance genes from wild relatives is a strategy which presents promise. This study examined both heat and drought tolerance from the tetraploid species Aegilops geniculata (U[superscript g]U[superscript g]M[superscript g]M[superscript g]). Additional screening for heat tolerance was conducted with the US genome species Aegilops peregrina (Hack) and Aegilops kotschyi (Boiss). A comprehensive screening system for drought tolerance was also constructed to evaluate wheat and its wild relatives. Previous reports suggested that Ae. geniculata accession TA2899 was moderately tolerant to heat stress. It had also previously been used to develop a full set of wheat-Ae. geniculata chromosome addition lines in a Chinese Spring background. To identify the chromosome(s) carrying the heat tolerance, all addition lines, as well as wheat check genotypes, were screened for post-anthesis heat tolerance in two growth chamber experiments. No chromosome addition lines were significantly different (p<0.05) from Chinese Spring, and none were found to have superior performance to the positive check cultivars. Forty-five accessions of Ae. peregrina and its close relative, Ae. kotschyi were screened in a post-anthesis heat experiment. A follow-up experiment compared the genotypes in a split-plot temperature treatment with heat and optimal growth chambers. Many accessions were similar to the control genotypes for grain fill duration, and some exceeded the wheat controls for relative chlorophyll index values on Day 12 and Day 16. TA1889 and TA1904, both Ae. peregrina accessions originating from Israel, had a higher grain fill duration across experiments than the best wheat control, and warrant further investigation. Previous reports suggested drought tolerance in Ae. geniculata. After preliminary screenings, six genotypes were selected for advanced screening and compared with three wheat cultivars. The advanced greenhouse screening system was conducted in 152cm tall PVC growth tubes. The experiment measured multiple plant responses, and had a datalogging system automatically collecting water content and matric potential of the growth media. Multiple accessions warranted further investigation, and showed potentially different modes of drought tolerance, with varying levels of stomatal resistance, biomass, and osmotic adjustment.

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Balfagón, Sanmartín Damián. « High temperatures modified plant responses to abiotic stress situations ». Doctoral thesis, Universitat Jaume I, 2020. http://hdl.handle.net/10803/669627.

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Plants growing in the field are affected by several adverse environmental conditions at the same time. The simultaneity of abiotic factors affecting plants creates a new stress situation different from the individual ones. Global warming is increasing earth surface temperature, and this is accompanied by other environmental changes (soil degradation, increase of drought periods, changes in precipitation pattern). All these changes will affect the arable lands around the world and crop production will be reduced unless new cultivars capable to face the environmental changes are developed. Therefore, the main objective of this PhD is to study the impact of different abiotic stresses in combination with high temperatures on plant physiology. To achieve this objective, this work has focus in studying physiological, hormonal and transcriptomic responses to different stress situations in citrus and model plants to obtain a global view of plant mechanisms to tolerate complex abiotic stress situations.
Las plantas cultivadas se ven afectadas por numerosas condiciones ambientales adversas al mismo tiempo. Cuando dos o más factores abióticos afectan a las plantas de manera simultánea se crea una nueva condición de estrés, diferente a la provocada por los estreses individuales. La temperatura de la superficie terrestre está aumentando, y esto viene acompañado por otros cambios medioambientales. Todos estos cambios afectan a las zonas de cultivos de todo el mundo y a la producción agrícola. El objetivo principal de esta tesis es estudiar el impacto en la fisiología de las plantas de diversos estreses abióticos en combinación con las altas temperaturas. Para conseguir este propósito, este trabajo se ha enfocado en el estudio de las respuestas fisiológicas, hormonales y transcriptómicas de las plantas a diferentes condiciones de estrés para obtener una visión global del mecanismo de tolerancia de las plantas a situaciones complejas de estrés abiótico.

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Abwao, Stephen Indieka. « Translational control of abiotic stress responses in Arabidopsis thaliana ». Thesis, University of Glasgow, 2012. http://theses.gla.ac.uk/3502/.

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A detailed understanding of the mechanisms by which plants sense and respond to major environmental stress factors will significantly contribute towards the prospects of developing crops capable of yielding well over a wider geographical range, including marginalised lands. One of the important stress response mechanisms in eukaryotes is mediated through phosphorylation of the eIF2α-subunit (serine 51/56) by specific kinases, namely double stranded RNA activated protein kinase (PKR), General Control Non-repressible 2 protein kinase (GCN2), Pancreatic eIF2α kinase (PERK) and Heme-regulated inhibitor protein kinase (HRI). This mechanism is a highly conserved phenomenon in eukaryotes and occurs in response to various stress conditions. Unlike in yeast and mammals, the mechanism is however not well established in higher plants, although its components such as eIF2α and GCN2 kinase have been identified in plants. The objective of the study reported herein was therefore to elucidate this mechanism in Arabidopsis, a model plant species. Initially the presence of yeast GCN2 kinase (ScGCN2), human PKR (HsPKR), human HRI (HsHRI) and human PERK (HsPERK) kinase homologues in Arabidopsis and Viridiplantae (green plants and algae) was evaluated through homology and phylogenetic analysis using TAIR10 and NCBI protein sequences, respectively. Arabidopsis lacked homologues of HsPKR, HsHRI and HsPERK however the presence of ScGCN2 homologue, herein referred to as AtGCN2 (Arabidopsis GCN2 kinase), was confirmed. Further evaluation of translation control mechanism through phosphorylation of AteIF2α (Arabidopsis eukaryotic initiation factor 2 α-sub-unit) was conducted using Atgcn2-1 null mutant plants (plants expressing a copy of truncated non-functional AtGCN2 kinase). Unlike WT Col-0, the Atgcn2-1 seedlings failed to induce phosphorylation of AteIF2α after exposure to amino acid starvation (150 µM glyphosate), NaCl (50 and 100 mM), heat (37oC) and cold (4oC) acclimation. On the other hand no strong phenotype of Atgcn2-1 was observed under optimal growth conditions and NaCl stress, except seedlings had relatively shorter roots compared with WT Col-0 seedlings. Failure of Atgcn2-1 seedlings to induce phosphorylation of AteIF2α Ser 56, after exposure to various stress confirmed that Arabidopsis possesses only one GCN2 kinase, as is in the case of yeast, and unlike mammalian systems. Further characterisation was conducted by exposing WT Col-0, Atgcn2-1, jar-1 and NahG seedling to biotic stress; Cauliflower Mosaic Virus (CaMV) and Pseudomonas syringae DC3000 (P. syringae) and positive control treatment using 150 µM glyphosate. The jar-1 and NahG seedlings are mutants defective in jasmonate and salicylic pathways, respectively. Inoculation with CaMV and P. syringae failed to induce phosphorylation of AteIF2α, unlike glyphosate. These results suggested that activation of the AtGCN2 kinase may be independent of jasmonate and salicylic pathways. Due to lack of a strong Atgcn2-1 phenotype, two mutants expressing AtGCN2 under the control of a 35S promoter, namely p35S:AtGCN2 and p35S:GFP:AtGCN2 were generated for further characterisation and localisation of AtGCN2 kinase, respectively. For characterization experiments the p35S:AtGCN2 seedlings were subjected to salinity stress, osmotic stress and temperature shock. In localisation experiments, GFP activities were assessed in non-stressed 7-day old p35S:GFP:AtGCN2 seedlings. During characterisation, higher germination rates were generally obtained with p35S:AtGCN2 and Atgcn2-1 compared with WT Col-0 seeds on ½ MS media containing NaCl, KCl and mannitol. On media infused with PEG6000 however p35S:AtGCN2 had the lowest germination rates. There were also no strong p35S:AtGCN2 phenotypes observed, except for increased root growth compared with WT Col-0 and Atgcn2-1 seedlings. In contrast, Atgcn2-1 seedlings subjected to PEG6000 osmotic stress had the highest increase in root growth compared with both WT Col-0 and p35S:AtGCN2 seedlings. On the other hand localisation of the GFP:AtGCN2 fusion protein was observed in the root and shoot tip tissues of p35S:GFP:AtGCN2 seedlings. The results obtained with Atgcn2-1 and p35S:AtGCN2 seedlings suggested that mutation of Atgcn2 produced root phenotypes. There were no significant differences in the survival of all the three genotypes when seedlings were subjected to heat shock stress. In cold shock experiments however Atgcn2-1 survival was significantly (p<0.05) lower than that of WT Col-0 and p35S:AtGCN2 seedlings, thus suggesting that null mutation of Atgcn2 increased susceptibility of seedlings to cold shock. The homologues of the yeast General Control Non-repressible 4 (ScGCN4) and human Activating Transcriptional Factor 4 (HsATF4), that are activated, when yeast and mammalian eIF2α is phosphorylated, respectively are yet to be identified in plants. To identify putative Arabidopsis ScGCN4 and HsATF4 homologues both in vitro and in silico approaches were explored. In vitro translation experiments using Wheat Germ Lysate (WG) mimicking plant translation under stress (WGeIF2α-P) and non-stress (WGeIF2α) conditions were conducted. To mimic stress conditions mPKR kinase was added into the translation reaction and significantly inhibited protein synthesis compared to control treatment. However, due to technical difficulties it was not possible to identify all translated transcripts under stress conditions (WGeIF2α-P) thereby identifying potential Arabidopsis ScGCN4 and HsATF4 homologues. This prompted the use of in silico tools to identify putative Arabidopsis homologues of ScGCN4 and HsATF4 using the FivePrime Viewer programme (Webb, 2008). A total of 99 TAIR10 transcripts with 5′ upstream Open Reading Frames (uORFs) were identified and only two transcripts, AT4G31590.1 and AT1G58120.1, were identified as putative homologues of ScGCN4 and non for HsATF4. The AT4G31590.1 and AT1G58120.1 transcripts encode for proteins involved in cellulose synthase/ gylcosyl transferase and methyl transferase activities, respectively. Although these genes are involved in key plant growth and developmental activities, there is need to assess translation control of their main open reading frame (mORF) by uORFs through phosphorylation of AteIF2α. Overall the data presented in this study suggest that stress response translation regulation mechanism mediated by phosphorylation of eIF2α is present in Arabidopsis. Plants are known, however, to carry out unique biological processes such as photosynthesis and cellulose biosynthesis that other eukaryotes lack. It would therefore not be surprising for them to have translation regulation mechanisms like other eukaryotes but with unique differences.

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Dittami, Simon. « Abiotic Stress Response in Ectocarpus siliculosus : a global approach ». Rennes 1, 2009. http://www.theses.fr/2009REN1S179.

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Les algues brunes représentent une composante importante de l'écosystème côtier, au sein duquel elles ont développé des mécanismes uniques leur permettant de vivre dans la zone intertidale, habitat caractérisé par des fluctuations fréquentes des conditions environnementales (stress biotique et abiotique). L'objectif de cette thèse était l'exploration des mécanismes permettant l'acclimatation et l'adaptation des algues brunes à certains stress abiotiques, en utilisant le modèle génétique et génomique Ectocarpus siliculosus. Dans ce but, trois axes de recherche ont été suivis : le métabolisme primaire chez Ectocarpus, la réponse à court terme à des stress salins et oxydatifs, et l'adaptation à long terme d'une souche isolée dans de l'eau douce. Ils ont été abordés en combinant plusieurs approches : la détermination de paramètres physiologiques, des expériences de profilage métabolique et transcriptomique, et l'annotation du génome d'Ectocarpus. Les résultats obtenus démontrent une grande plasticité transcriptomique et métabolique chez Ectocarpus siliculosus, et mettent en évidence plusieurs caractéristiques intéressantes : l'absence probable d'un mécanisme classique de concentration du carbone, l'induction de la production de l'acide gamma-aminobutyrique (un neurotransmetteur chez les animaux et une hormone de stress chez les plantes) en condition de stress (malgré l'absence des enzymes du GABA shunt, sa voie principale de synthèse), la présence d'un groupe de FCP (fucoxanthin chlorophyll a/c binding protein) induit par les stress, et l'utilisation de NaC1 comme osmolyte primaire dans les conditions de stress salins
Brown algae are an important component of the coastal ecosystem and have developed unique mechanisms enabling them to inhabit the intertidal zone, an environment with high levels of abiotic stress. The primary objective of this thesis was to study the mechanisms underlying the abiotic stress tolerance of brown algae in the new genetic and genomic model Ectocarpus siliculosus. To reach this objective, efforts were concentrated on three sub-tasks : the study of primary metabolism in Ectocarpus, of the short term response to saline and oxidative stress, and of the long term adaptation in a strain isolated from freshwater. Each of these sub-tasks was addressed by a combination of several approaches, including physiological measurements, metabolite - and transcriptional profiling, and genome annotation. The results presented illustrate great transcriptomic and metabolic plasticity of Ectocarpus siliculosus, and highlight several interesting features, such as the probable absence of an efficient organic carbon concentrating mechanism, the stress induced production of the neurotransmitter and plant stress hormone gamma-aminobutyric acid (in spite of the absence of its primary biosynthetic pathway, i. E. The GABA shunt), the presence of a family of stress responsive fucoxanthin chlorophyll a/c binding proteins, and the use of NaC1 as primary osmolyte during salt stress

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South, Kaylee. « Improving abiotic and biotic stress tolerance in floriculture crops ». The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1595499762154056.

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Chemayek, Bosco. « Studies on Resistance to Biotic and Abiotic Stresses in Wheat ». Thesis, The University of Sydney, 2016. http://hdl.handle.net/2123/15362.

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This investigation was focused on the assessment of genetic diversity for resistance to stem rust and stripe rust in an international wheat nursery, genetic characterisation of adult plant stripe rust resistance in Australian wheat cultivar Sentinel, understanding of genetic relationship between two stem rust resistance genes (Sr36 and Sr39) located on chromosome 2B and assessment of genetic diversity for physiological traits among a set of wheat landraces. Ten seedling stem rust resistance genes (Sr8a, Sr8b, Sr9b, Sr12, Sr17, Sr23, Sr24, Sr30, Sr31 and Sr38) and seven stripe rust resistance genes (Yr3, Yr4, Yr6, Yr9, Yr17, Yr27 and Yr34) were postulated either singly or in combinations in an international wheat nursery. Genotypes carrying uncharacterised resistance for stem rust and stripe rust against the Australian rust flora were identified for genetic analysis. Three consistent QTL (QYr.sun-1BL, QYr.sun-2AS and QYr.sun-3BS) were demonstrated to condition high level of adult plant stripe rust resistance in Sentinel. QYr.sun-1BL, QYr.sun-2AS and QYr.sun-3BS explained on an average 18.0%, 15.6% and 10.6% variation in stripe rust response, respectively. Additive nature of three QTL to condition high level of stripe rust resistance was demonstrated through comparison of recombinant inbred lines (RILs) carrying these QTL in all different combinations. Detailed characterisation of these loci will be performed. Stem rust tests on F3 populations involving Sr39 on a large and a shortened Aegilops speltoides translocation with Sr36 on a Triticum timopheevi segment showed complete repulsion linkage. The molecular cytogenetic analysis however indicated that these can be recombined using large F2 population. Significant variation for water-use efficiency related physiological traits was observed among wheat landraces. Genotypes with low and high mesophyll conductance, stomatal conductance and other physiological attributes will be useful in designing crosses to achieve high water-use efficiency in future wheat cultivars.

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Farieri, Elisa. « Risposta di specie ornamentali a stress abiotici ». Doctoral thesis, Università di Catania, 2015. http://hdl.handle.net/10761/3862.

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Da tempo l attenzione della ricerca si è concentrata sugli stress abiotici (es. idrico, salino) a causa delle forti riduzioni che determinano sulle rese. Pochi studi, però, si sono occupati delle piante ornamentali utilizzate negli spazi a verde, nonostante gravi danni che subiscono per effetto di questi stress. In questo quadro, le prove condotte nell ambito della tesi hanno riguardato: - screening della risposta di diversi arbusti ornamentali allo spray marino; - risposta fisiologica e biochimica di Photinia ×fraseri Dress Red Robin ed Eugenia uniflora L. Etna Fire allo stress idrico; - effetti della differente temperatura dell acqua sulla conducibilità idraulica di sei specie di pini iberici; - risposta di Callistemon citrinus (Curtis) Skeels e Viburnum tinus L. Lucidum ad aerosol marino e surfactanti in condizioni ambientali differenziate; - risposta allo stress salino in rapporto alla modalità di somministrazione del sale in Photinia ×fraseri Dress Red Robin . In estrema sintesi le prove, diverse per obiettivi, metodi, materiali biologici, hanno consentito di stabilire che: - lo screening fra genotipi è uno strumento importante per valutare la risposta delle piante, che tuttavia si può modificare a livello intraspecifico; - nelle piante ornamentali è importante valutare il valore estetico; per tale motivo assumono interesse caratteri come peso secco della porzione epigea, area fogliare e soprattutto la percentuale di danno alle foglie; - le determinazioni fisiologiche (tasso di traspirazione, conduttanza stomatica e fotosintesi netta), soprattutto se correlate tra loro, forniscono utili informazioni sui meccanismi di azione; - le determinazioni biochimiche, anche se onerose, possono aiutare a capire la risposta delle piante; - le risposte sono influenzate dall interazione del genotipo con le condizioni ambientali; - l associazione fra stress diversi può talvolta intensificare i danni alle pianta, anche se non sempre si osservano effetti sinergici; - la risposta ad uno stress, come quello salino, si modifica in relazione alla modalità di applicazione della soluzione salina; in Photinia, ad esempio, i maggiori danni si sono avuto con la somministrazione di sale direttamente all apparato radicale; - l'analisi della concentrazione di ioni (Na+ e Cl-) nei diversi tessuti vegetali e lo studio della loro traslocazione/compartimentalizzazione consente di comprendere meglio la risposta della pianta allo stress salino; - lo studio dello stress può rappresentare un importante approccio per la valutazione degli effetti futuri del global change. In sintesi i risultati ottenuti indicano come la risposta agli stress abiotici dipenda in misura rilevante dal genotipo. Nelle piante ornamentali, in considerazione dell ampia articolazione biologica, questo aspetto certamente complica le indagini, per cui assume interesse la possibilità di individuare metodi non distruttivi di diagnosi precoce della tolleranza agli stress abiotici.

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Nohoesu, Oviavo Remi, Bal Krishna Chand Thakuri et Dhirendra Kumar. « Characterization of SIP428 : a NAD+-Dependent Deacetylase Enzyme, in Abiotic Stress ». Digital Commons @ East Tennessee State University, 2021. https://dc.etsu.edu/asrf/2021/presentations/38.

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SABP2-interacting protein 428(SIP428) is a SIR2-type deacetylase, also called sirtuins. The SIP428 proteins belong to a family of NAD+-dependent deacetylase enzyme that was identified in tobacco. SABP2 is an important methyl esterase enzyme that catalyzes the conversion of methyl salicylic acid (MeSA) into salicylic acid (SA) during the pathogenic challenge. Accumulation of SA induces systemic acquired resistance (SAR), a broad-spectrum defense mechanism in other uninfected distal parts of the plant. Sirtuins play diverse roles in DNA repair, apoptosis, and stress responses. Cellular proteins are known to undergo posttranslational modifications such as methylation, phosphorylation, and ubiquitination. A more recent addition to the list is acetylation. Protein acetylation is a reversible modification that plays role in regulating transcription, activation, and deactivation of certain pathways by transferring acetyl group to lysine residues. This change neutralizes the positive charge of the amino group thereby affecting the biological function of the affected proteins. Preliminary research has shown that SIP428 is a non-histone deacetylase. To understand better about the role of SIP-428 in plant physiology and how it plays a vital role in SABP2 signaling pathway we will be using transgenic tobacco plant in which the expression of SIP 428 has been silenced/knocked down.

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Stewart, Keith J. « Abiotic stress and mlo-resistance breakdown to barley powdery mildew ». Thesis, University of Oxford, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.400447.

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Moore, Thomas. « Are barley dwarfing genes important in tolerance to abiotic stress ? » Thesis, University of East Anglia, 2012. https://ueaeprints.uea.ac.uk/42362/.

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DELLA proteins are a highly conserved group of growth inhibitors, mutants of which were integral to the semi-dwarf, high yielding wheat lines of the Green Revolution. In addition to reducing plant growth, the gain of function (GoF) mutants in which DELLA protein is stabilised were shown to confer resistance to salt stress in the model species Arabidopsis. In order to determine whether these findings could be translated from Arabidopsis to monocot crop species, GoF and loss of function (LoF) mutants of the barley DELLA orthologue, Sln1, were characterised and growth and development assessed. By subjecting DELLA wild-type and mutant barley plants to abiotic stress conditions (salt stress and heat shock) it was established that the increased survival conferred by stabilised DELLA that was reported in Arabidopsis was also applicable to barley, and that survival of the LoF barley mutants was decreased. Further evidence for the importance of stabilised DELLA was obtained when additional mutants in the GA signalling pathway (gse1a,j,n; Gse1, GA receptor mutants) in which DELLA protein is predicted to accumulate, also showed increased tolerance to abiotic stress. These data suggest DELLA protein function is conserved between monocot (cereal) and dicot plants. Attempts to produce transgenic barley plants in which Sln1 was silenced were inconclusive, likely underlining the essential nature of the gene in growth, development and regeneration. The studies provide a basis for further work to investigate the mechanisms underlying DELLA function in cereals.

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Alzwiy, Ibrahim A. Mohamed. « The interaction between abiotic and biotic stress in Arabidopsis thaliana ». Thesis, University of Exeter, 2013. http://hdl.handle.net/10871/13946.

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Plants are continuously exposed to different abiotic and biotic stresses in their natural environment. Their capacity to survive depends on the capacity to perceive external signal and quality amount a defence response for protection from the stress perceived. The purpose of this project was to study the impact of combined abiotic stress and biotic stress on the outcome of the disease inducing Arabidopsis thaliana – Pseudomonas syringae interaction. This study included a focus on the role of ABA in these interactions and also whether 3´-O-β D- ribofuranosyl adenosine (hereafter it called ‘400’ compound), a novel adenosine derived compound induced during compatible interactions, was involved. The later involved the targetted disruption of a putative 400 biosynthetic pathway involving analysis of knockout mutants of enzymes; APD-ribose diphosphatase NAD binding / hydrolases of the NUDIX class, glucosyl transferases, ribosyltransferases, a ribose-phosphate pyrophosphokinase3 and galactosyltransferases. Unfortunately, none of these targeted interventions modified the host response to Pseudomonas infection, nor altered levels of 400 in challenged leaves. The primary research investigated the interaction between abiotic and biotic stresses in Arabidopsis plants focussing on the modulation of plant defence against multiple, and possibly antagonistic, stress responses and the role plant hormones play in this process. We showed that high light caused enhanced susceptibility to the already virulent Pseudomonas syringae DC3000pvsp61. The pathways contributing to this enhanced susceptibility were largely ABA independent. Subsequent characterization of transgenic lines expressing the soluble Arabidopsis abscisic acid receptors, PYRABACTIN RESISTANCE1-LIKE4-6 provided compelling evidence for a role for these receptors in DC3000 virulence strategies, but they contribute to a lesser extent to the enhanced susceptibility under high light. This was corroborated genetically by using mutants of the immediately downstream targets of PYLs, the type two protein phosphatase, specifically the triple mutant hab1-1/abi2-1/abi1-2. A number of epitope and fluorescent constructs were generated to facilitate future studies of the role of ABA signaling. Targetted profiling suggested that SA dynamics were altered under DC3000 challenged Arabidopsis grown under high light. Furthermore, differential accumulation of flavonoids suggested these may also play a role in attenuating host defences under high light. Finally we provide evidence based on comparative analysis of that the photoreceptors phytochrome double mutant phyA-211/phyB-9 and cry1/cry2 behave antagonistically in Arabidopsis response to DC3000. Overall our studies support the conclusion that plants abiotic stress (HL) response takes precedence over biotic stress (DC3000) responses and that abiotic stress is detrimental to plant immunity. The luciferase transgenic PYL lines showed high level of expression of ClucP::PYL5 plant tissues challenged 2hpi of DC3000 (OD600: 0.15) in comparison with C1lucP::PYL6. This result opposes to what RT-PCR reported; which was that three PYLs genes display similar expression level at 6hpi of hrpA or 18hpi of DC3000. The epitope tags of CaMV::HA transgenic plants showed HA-tagged signal with stunted phenotype in a range of PYL4, 5 and 6 plants but none of the plants displayed any differences in susceptibility to DC3000. Although, RT-PCR assay showed high levels of expression in the three PYLs, 6hpi of hrpA but no signal was detected in B8eGFP::PYL5 transgenic line either followed the DC3000 and hrpA infection or by examined plant seedlings at early stages under confocal microscopy.

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Rajab, Salem Mohamed Ahmed. « The role of HvBWMK1 in barley tolerance to abiotic stress ». Thesis, Heriot-Watt University, 2013. http://hdl.handle.net/10399/2830.

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Barley (Hordeum vulgare L.) is an important crop grown throughout the world. Quality and quantity of barley is compromised by abiotic stresses, salinity in particular which is already widespread in many regions. Mitogen Activated Protein Kinase (MAPK) cascades are signal transduction pathways involved in biotic and abiotic plant defence mechanisms. Here, the function of the barley gene HvBWMK1 has been investigated. Transgenic barley plants that overexpress HvBWMK1, or in which HvBWMK1 has been down-regulated by antisens, were generated, as well as empty vector control plants. The transformation efficiency using Agrobacterium was 10.4% independent transgenic plant per embryo. Northern blot analysis of HvBWMK1 primary overexpression lines showed up-regulation of mRNA level, conversely the antisense lines of HvBWMK1 showed clear down-regulation. Real-time PCR analysis in the T1 generation revealed that two over-expresser lines showed higher expression as compared with wild type (by 79% and 35%) while the HvBWMK1 antisense construct reduced endogenous gene expression partially (by 14%, 23% and 39% compared with wild type). Barley seedlings were subjected to two weeks of salt stress (150 mM NaCl) then biochemical and physiological parameters were measured. The overexpression lines showed an increase in tolerance to salinity stress compared to antisense lines and controls. Tolerance was accompanied with increasing endogenous proline and chlorophyll levels and a reduction in hydrogen peroxide content after salinity exposure. Overall these results suggest that the barley MAPK HvBWMK1 acts as a positive regulator in barley tolerance to salinity stress.

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Weerathunga, Arachchilage Achira S. « A Novel Transcription Factor in Arabidopsis thaliana Abiotic Stress Response ». ScholarWorks@UNO, 2015. http://scholarworks.uno.edu/td/2114.

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Plants respond to environmental stress by altering their gene expression. Under stress conditions some genes are activated and some genes are repressed. Even though a lot of work has been done to understand mechanisms of gene activation under abiotic stress very little information is available on how stress responsive genes are kept repressed under normal growth conditions. Recent work has revealed that plants use transcriptional repression as common mechanism of gene repression. Transcriptional repression is achieved by recruitment co-repressor complexes to the target genes. Recent studies have revealed that the co-repressor LUH complexes with SLK1 and SLK2 to silence Arabidopsis thaliana stress responsive genes. However, the transcription factors involved in the recruitment of this complex to its target genes are not known. In this study, we identified SLK2INT1, as a novel transcription factor that is involved in silencing of select Arabidopsis thaliana stress responsive genes by recruiting the LUH-SLK2 complex.

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Chambers, David L. « Abiotic Factors Underlying Stress Hormone Level Variation Among Larval Amphibians ». Diss., Virginia Tech, 2009. http://hdl.handle.net/10919/27817.

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Anthropogenic disturbances can alter the abiotic composition of freshwater systems. These compositional changes can act as physiological stressors towards system inhabitants. However, little is known about how these altered abiotic factors influence stress hormones (corticosterone) in larval amphibians. Throughout the following chapters, I examined the effects of several abiotic factors on baseline and stress-induced corticosterone levels in the larvae of four amphibian species: Jefferson salamander (Ambystoma jeffersonianum), spotted salamander (A. maculatum), wood frog (Rana sylvatica), and grey treefrog (Hyla versicolor). Chapter II examined corticosterone level differences throughout development in A. jeffersonianum and R. sylvatica larvae under field, mesocosm, and laboratory venues. Baseline corticosterone levels in R. sylvatica increased near metamorphic climax in all venues, but not in A. jeffersonianum. Rather, baseline corticosterone levels differed with respect to venue throughout development in A. jeffersonianum. Chapter III examined corticosterone level differences among free-living A. jeffersonianum populations and possible abiotic factors underlying these hormone differences. Corticosterone levels significantly differed across populations. Increased baseline corticosterone levels significantly correlated to low pH. There was also a trend for increased baseline corticosterone levels to be positively correlated with chloride levels and negatively correlated with conductivity. Chapter IV examined the effects of laboratory manipulated pH on corticosterone levels in A. jeffersonianum, A. maculatum, R. sylvatica, and H. versicolor. There was a significant correlation between increased baseline corticosterone levels to low pH in all four species. Prey consumption (in both Ambystoma species) and survival (in A. jeffersonianum, A. maculatum, and R. sylvatica) were also negatively correlated to low pH. Chapter V examined the effects of increased conductivity on corticosterone levels in A. jeffersonianum, R. sylvatica, and H. versicolor. Increased conductivity exposure significantly correlated to increased baseline corticosterone levels in A. jeffersonianum and R. sylvatica. Prey consumption in A. jeffersonianum was also negatively correlated to increased conductivity. My dissertation shows that abiotic factors, such as pH and conductivity, can influence corticosterone levels in larval amphibians. These results suggest that corticosterone levels in larval amphibians may be a suitable biomarker reflective of altered freshwater habitat quality. However, my results also suggest that one should use a high degree of caution when using corticosterone levels in larval amphibians as a means to infer the health status of a population.
Ph. D.

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Pham, Jasmine. « The role of AHK5 in abiotic and biotic stress signalling ». Thesis, Imperial College London, 2011. http://hdl.handle.net/10044/1/8959.

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In Arabidopsis thaliana, eight histidine kinases (HKs) have been identified which function in hormone signalling, stimuli perception, and plant development. To better elucidate HK roles in signalling, the function of the least characterised HK, AHK5, in stress tolerance was investigated using a T-DNA insertion knockout line (ahk5-1). Reduced inhibition of seedling root growth was seen in ahk5-1 in response to salinity when compared to wild-type Col-0 in tissue culture assays. In mature plants, ahk5-1 showed greater fresh weight gain under either salinity or drought stress. Loss of AHK5 function did not alter cold stress tolerance, nor basal and acquired heat stress tolerance in terms of seedling root elongation. Infection with the biotrophic pathogen Pseudomonas syringae pv. tomato DC3000 revealed ahk5-1 is compromised in disease resistance, exhibiting increased chlorosis and in planta bacterial growth. Levels of the plant hormones salicylic acid, jasmonic acid, and abscisic acid, alongside the bacterial phytotoxin coronatine, were lower in pathogen challenged ahk5-1 mutants compared to wild-type plants. The ahk5-1 mutant was also more susceptible to the necrotrophic pathogen Botrytis cinerea, supporting more fungal growth and displaying accelerated symptom development. Hydrogen peroxide production has been linked with both resistance and susceptibility towards B. cinerea; in ahk5-1, 3,3-diaminobenzidene (DAB) staining suggested reduced hydrogen peroxide production in response to infection. Complementation and expression of AHK5 with either full-length genomic AHK5 under the 35S CaMV promoter or full-length AHK5 cDNA under the native promoter rescued the ahk5-1 mutant stress response phenotypes. In summary, AHK5 was found to negatively regulate abiotic stress tolerance whilst positively contributing towards resistance against pathogens employing different lifestyles. To begin to establish an AHK5 signalling network, tandem affinity purification coupled with LC-MS/MS was employed for identification of possible AHK5 interacting proteins. Suggestions for further optimisation of the purification method are presented. The role of AHK5 in regulation of plant stress responses through modulation of reactive oxygen species and hormone signalling and through protein-protein interactions are reviewed. Suggestions for further investigation are also discussed.

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Endeshaw, Solomon Tadesse. « Grape and olive : physiological responses to biotic and abiotic stress ». Doctoral thesis, Università Politecnica delle Marche, 2013. http://hdl.handle.net/11566/242716.

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Le piante crescono in ambiente aperto in continuo cambiamento e sono sottoposte a stress. Gli stress possono essere classificati come interni e esterni. Lo stress interno porta a mutazioni o a abnormi divisioni cellulari e infine a una ripartizione anomala della crescita, dell’allocazione e della ripartizione del carbonio. Stress esterni possono essere abiotici o biotici. Siccità, freddo, caldo, alta salinità, fitotossine rilasciate da lettiere indecomposte o altri residui organici sono fra i fattori che più drasticamente riducono la crescita, lo sviluppo e la produzione delle piante. Fra gli stress biotici quelli da patogeni (batteri, funghi, fitoplasmi, virus) sono i più pericolosi per la produzione. Nei prossimi anni per consentire livelli elevati di produzione capaci di rispondere alla crescente domanda di olio e vino, ogni regione produttiva dovrà rispondere con un incremento delle superfici coltivate nelle zone agroecologiche in cui sono attualmente coltivate oppure dovrà espandersi in nuove zone. Questo richiederà in ogni caso un cambiamento di tecniche di coltivazione e di gestione degli impianti che dovranno di conseguenza fronteggiare maggiori stress biotici (nelle zone meno vocate) o stress dovuti al reimpianto (se impiantati negli stessi appezzamenti). Questo progetto ha lo scopo di valutare la risposta fisiologica della vite e dell’olivo a stress biotici e abiotici. In particolare sono oggetto stati di studio gli effetti del legno nero (fitoplasma) e del accartocciamento virale (GLRaV-3 virus) sugli scambi gassosi e sulla produzione di vite Chardonnay and Cabernet Franc, rispettivamente. Sono stati inoltre approfonditi gli effetti di residui colturali di olivo indecomposti e di sansa proveniente da un frantoio a due fasi su olivo cv. Arbequina and Frantoio. L’infezione con fitoplasmi e virus ha indotto una riduzione significativa della fotosintesi, della traspirazione e della conduttanza stomatica in entrambi i vitigni durante l’estate dopo l’allegagione. La riduzione degli scambi gassosi e del metabolismo ha indotto una riduzione della produzione, della crescita dei tralci e della loro lignificazione. In definitiva la riduzione della produzione è stata pari al 70 e 40% rispettivamente. L’applicazione di residui colturali di olivo e di sanse di olivo su piante in vaso ha ridotto la crescita radicale e dei germogli in funzione della dose applicata, mentre ha portato in proporzione ad un aumento del contenuto di sostanza organica nel substrato. In conclusione, nel caso di fitoplasmi e virus è necessaria un’attenta profilassi per evitare la diffusione attraverso il materiale di vivaio e una volta presenti in campo deve essere prevista una campagna di eradicazione delle piante infette che possono sopravvivere all’infezione e funzionare da inoculo. Nel caso dell’olivo si deve invece tenere conto che applicazioni localizzate di residui indecomposti e di sanse hanno un’azione temporanea fortemente tossica per le radici e quindi per poter sfruttare al meglio il miglioramento indotto del contenuto di sostanza organica e non avere ripercussioni negative sulle produzioni serve un’attenta programmazione delle dosi e del momento dell’intervento.
Plants grow and develop in an open field, with continuously changing weather condition that induces stress. Stress are broadly classified as external and internal. Internal stress is that drive from mutation or abnormal cell divisions and to unbalanced growth and carbon allocation and partitioning. External stress can have abiotic and biotic origin. Drought, cold, high-salinity, heat and phytotoxin released from undecomposed litter and manure are major abiotic stresses that severely reduce the plant growth, development and yield. Whereas, pathogen (bacteria, fungi, phytoplasma, virus) are the major biotic stress that severely reduce yield. To meet the current increase in global demand of agricultural good in general and olive oil and wine in particular, each growing region has to respond either by incorporating new olive and grape orchard in the existing agroecological zone and/or expanding to new agroecological zones or by changing mode of cultivation and orchard management, facing different biotic stress and external stress in replanting condition. This project aimed at evaluating the physiological responses of grape and olive to biotic and abiotic stress respectively. In particular, effect of Bios noir (BN, a phytoplama disease) and grapevine leafroll associated virus 3 (GLRaV-3, viral disease) on gas exchange and yield of Vitis vinifera cv. Chardonnay and Cabernet Franc respectively; and effect of undecomposed olive shoot residue (OSR, originated from pruning and leaf shedding) and fresh two-phase olive mill waste (TPOMW, coming from two-phase decanter) were studied on shoot growth, root proliferation and biomass partition of Olea eropaea L. cv. Arbequina and Frantoio. Biotic stress originated from BN and GLRAV-3 infection showed that Photosynthesis, stomatal conductance and transpiration were significantly reduced in the symptomatic Chardonnay and Cabernet Franc vines through the summer after the fruit set. The reduction in metabolism due to BN and GLRaV-3 infection in cv. Chardonnay and Cabernet Franc had a direct influence on the decrease in total berry production, vine size and cane lignifications of symptomativ vines. Indeed, they suffered a drastic decrease of about 70 and 40% in yield respectively. Whereas, application of OSR and TPOMW in the pot altered shoot and root growth, biomass partition and relative growth rate of fine root and shoot; while increasing soil total organic matter and carbon, total N and polyphenol content of the growing substrate. Hence there is no chemical spray develop to control the infection of BN and GLRaV-3 pathogens, planting phytoplasma and virus free root stocks during the vineyard establishment and uprooting the infected vine and replanting new to avoid spread during pruning and by insect vectors is the best way to minimize the adverse effect of BN and GLRaV-3 on quality and quantity yield. To avoid antagonistic effect of OSR and TPOMW on root and shoot growth and improve soil fertility knowing the exact quantity, for each types olive orchards, and when to apply in play major role.

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Gessese, Mesfin Kebede. « Characterization of wheat landraces for resistance to biotic and abiotic stresses ». Thesis, The University of Sydney, 2017. http://hdl.handle.net/2123/17198.

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This study covered genetic and molecular analyses of stripe rust and leaf rust resistance in common wheat landraces and investigation of response of drought and short term leaf temperature changes among a set of 20 durum wheat genotypes. Three all stage resistance genes (YrAW5 in Aus27430 and YrAW6 and YrAW7 in Aus27492) were identified. YrAW5 and YrAW7 were located on chromosomes 6AS and 5AL, respectively. The location of YrAW6 was inconclusive. While Aus27430 was concluded to carry Yr18, Aus27492 appears to carry an uncharacterized adult plant resistance gene. Four QTL for stripe rust resistance (QYr.sun-1BL, QYr.sun-2AL, QYr.sun-5AL and QYr.sun-3BS) were detected in Aus28166/AvS RIL population. QYr.sun-1BL and QYr.sun-5AL also conferred resistance to leaf rust in Aus28166. QYr.sun-1BL and QLr.sun-1BL corresponded to the pleiotropic locus Lr46/Yr29/Sr58/Pm39/Ltn. The co-located loci QYr.sun-5AL and QLr.sun-5AL appear to represent a new pleiotropic resistance locus. Durum wheat genotypes showed significant variation for mesophyll conductance in response to water stress and short-term variation of leaf temperature highlighting the potential for improving durum wheat for drought and heat stress.

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Lozano, Elena Fidel. « Control of abiotic stress responses by brassinosteroids receptors in Arabidopsis thaliana ». Doctoral thesis, Universitat Autònoma de Barcelona, 2019. http://hdl.handle.net/10803/669371.

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La presente tesis doctoral reporta nuevas funciones de los receptores de brassinosteroides (BRs) en el control de respuestas a estrés abiótico en la planta modelo Arabidopsis thaliana. Los BRs son hormonas esteroides que desempeñan roles esenciales en el crecimiento y desarrollo de la planta, así como en su adaptación al estrés ambiental. Se sabe que la aplicación exógena de BRs dota a los cultivos de protección frente a estreses abióticos, tales como estrés salino, frío o sequía, pero aún se desconocen los mecanismos que gobiernan estas respuestas. La activación de los componentes de la señalización mediada por BRs no han conseguido dotar de la resistencia observada con aplicaciones exógenas. Los roles putativos de los receptores de BRs bajo estrés arrojarian información clave para desentrañar los mecanismos de adaptación a estrés mediados por BRs, pero estos han permanecido inexplorados. Aquí, usamos un enfoque multidisciplinar, incluyendo genética, análisis multiómico y bioinformática, para descifrar los roles de los receptores de BR frente a estreses abióticos, tales como daño al ADN, estrés osmótico y sequía. Los resultados presentados en esta tesis desvelan el papel del control espacio-temporal de la señalización de BRs en respuesta a estrés abiótico. El análisis fisiológico de raíces de Arabidopsis reveló que los receptores de BRs son necesarios para la regeneración celular de las células madre de la raíz tras daño al ADN. Además el análisis multiómico de plantas expuestas a sequía mostró que la sobre expresión del receptor BRI1-like 3 (BRL3), específico de tejidos vasculares, promueve una firma transcriptomica y metabolómica alterada que alivia los efectos negativos de la sequía y los desacopla de la parada del crecimiento. La mayor parte de los distintivos ómicos encontrados en estas plantas son específicos de floema. El enfoque bioinformático usado para desgranar el control transcripcional específico de tejido, fue además implementado en una herramienta web extensible a cualquier otro organismo. Finalmente, mediante un enfoque de biología estructural, encontramos una pequeña Receptor-Like Kinase (RLK), cuya interacción con BRL3 es más favorable que con el correceptor canónico BAK1. De hecho, este candidato se ha implicado recientemente en la respuesta a estrés osmótico, lo que sugiere vías alternativas activadas por BRs que controlan la respuestas a estrés abiótico. En resumen, la presente tesis doctoral avanza sobre las funciones de los receptores de BRs que promueven el crecimiento y supervivencia de la planta bajo estrés abiótico. La señalización paracrina de los BRs en el nicho de células madre de la raíz y la adaptación metabólica dirigida desde los tejidos vasculares ilustran la importancia de analizar las respuestas específicas de tejidos. El presente estudio también arroja nuevas ideas para futuras investigaciones en los mecanismos mediados por los BRs que contribuyen a la adaptación de las plantas.
The present PhD thesis dissertation reports new functions for Brasssinosteroids receptors controlling abiotic stress responses in Arabidopsis thaliana. Brassinosteroids (BRs) are the steroid hormones of plants. BRs play essential roles in plant growth and development and plant adaptation to stress. In this direction, exogenous application of BRs provide crop protection against abiotic stresses, such as salt, cold or drought stress, yet the mechanisms governing these responses have remained unknown. Activation of signaling downstream components failed to provide the resistance observed with exogenous applications. The putative roles of BR receptors under stress stand out as key information for dissecting the BR-driven mechanism of stress adaptation but they have remained very unexplored. Here, we use an interdisciplinary approach, including genetics, multiomics analyses and bioinformatics, to decipher the roles of BR receptors in front of abiotic stresses such as DNA damage, osmotic stress and drought. The results presented in this thesis uncover a role for the spatiatiotemporal control of BR signaling in response to abiotic stress. Physiological analysis of Arabidopsis roots revealed that BR receptors are required for cellular regeneration of the root stem cells after DNA damage. Moreover, the multiomic analysis of plants exposed to drought showed that the overexpression of the vascular-specific BRI1-like 3 (BRL3) receptor lead to an altered transcriptional and metabolic signature that alleviate the detrimental effects of drought and decouple drought tolerance from growth arrest. A major part of omics hallmarks found in these plants are phloem-specific. The bioinformatic approach used to disentangle tissue-specific transcriptional control was further implemented in a web tool, expandable to any plant specie. Finally, through a structural biology approach we found a small Receptor-Like Kinase (RLK) whose interaction with BRL3 is more favorable than the canonical co-receptor BAK1. Indeed, this candidate has been recently involved in response to osmotic stress, which suggest alternative BR-activated pathways that control abiotic stress responses. Overall, the present PhD thesis advances the roles of BR receptors to support plant growth and survival under abiotic stress. BRs paracrine signaling at the root stem cell niche and the metabolic adaptation driven from vascular tissues illustrate the importance of dissecting plant tissue-specific responses. The study presented here also opens new windows for further investigation on mechanisms triggered by BR-receptor that contribute to plant adaptation.

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Al-Quraan, Nisreen Singh Narendra K. « Role of Arabidopsis thaliana calmodulin isoforms in tolerance to abiotic stress ». Auburn, Ala, 2008. http://repo.lib.auburn.edu/EtdRoot/2008/SUMMER/Biological_Sciences/Dissertation/Al-quraan_Nisreen_3.pdf.

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Migicovsky, Zoë. « Transgenerational inheritance of epigenetic response to abiotic stress in Arabidopsis thaliana ». Thesis, Lethbridge, Alta. : University of Lethbridge, Dept. of Biological Sciences, c2012, 2012. http://hdl.handle.net/10133/3311.

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Abiotic stresses are one of the major limiting factors of plant growth and thus crop productivity. Exposure to these stresses, including temperature and UV, cause physiological and epigenetic changes in plants. Such changes may be inherited in the progeny of stressed plants, and may change their ability to respond to stress. To understand the ability of plants to inherit an epigenetic stress memory as well as the physiological manifestations of such a memory, we propagated both stressed and control plants and compared the progeny under both normal and stressed conditions. In addition to wild-type plants we used Dicer-like mutants dcl2, dcl3 and dcl4, as Dicers have been linked to RNA-directed DNA methylation, a form of epigenetic memory. These studies revealed that leaf number decreases in the progeny of stressed plants, and bolting occurs earlier in the progeny of temperature stressed plants but later in the progeny of UV-C stressed plants. Transposons were also re-activated in the progeny of stressed plants. While heat shock transcription factor 2A increased expression in the progeny of heat stressed plants, many genes involved in DNA repair and histone modifications decreased. DCL2 and DCL3 appeared to be more important in transgenerational stress memory than DCL4. However, all dcl plants were generally not significantly different than wild-type plants, indicating that a single DCL deficiency may be compensated for by another DCL.
xiv, 246 leaves : ill. ; 29 cm

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Mendu, Venugopal. « ROLES OF MICRORNAS IN PLANT ABIOTIC STRESS, DEVELOPMENT AND VIRAL INFECTION ». UKnowledge, 2008. http://uknowledge.uky.edu/gradschool_diss/663.

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Plant microRNAs play important roles in plant growth and development. Here we investigated the roles of miRNAs in the plant abiotic stress, development and viral infection. MicroRNA membrane array analysis using five different abiotic stress treatments resulted in the identification of 8 novel stress inducible miRNA-families. Functional studies on novel stress inducible miR168 revealed its functional relation with abiotic stress. Over expression of miR168 in Arabidopsis showed upregulation of four stress related miRNAs (miR163, miR167, miR398 and miR408). Analysis of 9 independent transgenic lines showed induction of miR398, an oxidative stress responsive miRNA with a corresponding down regulation of its target genes. Heavy metal oxidative stress tolerance bioassays confirmed the susceptibility of transgenics compared to the wild types indicating the fact that the miR168 is indirectly involved in plant abiotic stress by inducing other stress responsive miRNAs. MicroRNAs are highly conserved across the plant kingdom. A miRNA atlas was drafted for different tomato organs and fruit stages using the known miRNA sequences from different plants species. A large variation in both number and level of miRNA expression pattern was observed among different organs as well as among fruit stages. In the present investigation, we have found a window of expression for different miRNAs during the fruit development. A gradual decrease in the expression levels of miR160h, miR167a and miR399d and a gradual increase in miR164a have been noticed towards the fruit maturation while miR398b showed dual peaks during fruit development indicating a potential role of various miRNAs in fruit development and maturation. Sonchus yellow net virus (SYNV) infected Nicotinana benthamiana leaves showed severe disease symptoms at two weeks post infection (WPI) and gradually recovered from the SYNV infection after 4-5 WPI correlating with the overall miRNA levels. The miRNA array and northern analysis showed an overall reduction of miRNA biogenesis during 2WPI followed by restoration to normal levels supporting the idea that the SYNV indeed interfered with the host miRNA levels which caused the symptoms and recovery phenotypes. Overall studies on plant abiotic stress, development and viral infection showed important roles of miRNAs in different aspects of plant life.

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Ahmad, Izhar. « The role of cation channels in abiotic stress resistance in rice ». Thesis, University of York, 2014. http://etheses.whiterose.ac.uk/8150/.

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The alarmingly increasing human population needs improved food production but this aim is hampered by different abiotic stresses. Osmotic stress and salt stress are the two prominent examples of abiotic stresses and affect up to 50% of the arable land. These stresses severely affect all plants, but glycophytes (e.g. rice) are especially sensitive. During stress, nutrient uptake, such as K+, is often disturbed. Thus, better K+ nutrition and distribution play a vital role in plant abiotic stress tolerance. To improve K+ nutrition, the role of K+ transporters is likely to be essential. Loss of function and gain of function approaches could help establish the exact function of transporters involved in K+ nutrition. Rice TPKs and AKT1 are K+ channels which are localised to the tonoplast and plasma membrane respectively. The two TPK isoforms, TPKa and TPKb, are localised to the tonoplast of LV and SV respectively. They were characterized in a variety of abiotic stress conditions. The data showed better growth and higher K+ concentration for the TPKa and TPKb transgenic lines when grown in zero K+ and osmotic stress conditions suggesting their role in improving in K+ nutrition. TPKs have no direct involvement in the K+ uptake, but somehow influence K+ uptake and improve K+ nutrition. The higher K+ concentration in the leaves of overexpressor plants suggested the involvement of TPKs in the distribution of K+ within the plant body. TPKs play a role in the guard cells' movements and affect the stomatal conductance and therefore showed a better response to the osmotic stress conditions. The role of rice AKT1 was tested by comparing the knockout and overexpressing lines of AKT1 with the wild type plants. The data suggested that AKT1 is involved in the K+ uptake in a range of external K+ concentrations and osmotic stress conditions. The role of AKT1 is obvious in the K+ deficient conditions where NH4+ is present. The leaf K+ concentration suggested that AKT1 influences K+ transport into the leaves. The K+ concentration in the leaf cells showed an effect on the stomatal conductance and in turn an effect on the growth phenotype under zero K+ and osmotic stress conditions. The data revealed that AKT1 is insensitive to NH4+ toxicity.

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Guragain, Bhuwan. « Transcriptional co-repressor response of Arabidopsis thaliana to different abiotic stress ». ScholarWorks@UNO, 2013. http://scholarworks.uno.edu/td/1738.

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Plants adapt to the complex environmental challenges by regulating their gene expression. Analyses of plant genomes have identified many genes that are either expressed or repressed during environmental stress. However we do not have much information on gene repression. Transcriptional repression in Arabidopsis thaliana is caused by co-repressors that lack the DNA binding domain and are recruited by transcription factors to regulate target gene expression. The Sridhar lab has identified co-repressors SLK1, SLK2, and LUH, which prevent the expression of stress response genes under non-stress conditions. Arabidopsis transgenic lines expressing the GUS under the control of co-repressor’s promoter were created, to determine the conditions during which the co-repressor are induced. In addition to that, transgenic plants expressing YFP fused with the co-repressor were created to study the sub-cellular localization of the co-repressor. I found that SLK1, SLK2, and LUH are expressed ubiquitously in most of the plants tissue evidenced by the promoter fusion to the GUS reporter. SLK1, SLK2, and LUH are induced by osmotic, cold and dehydration stress conditions. Furthermore, these proteins are localized in the nucleus of the cell. Key words: Arabidopsis thaliana, Co-repressor, SLK1, SLK2, LUH, Transcription factors, Trangenesis, Stress condition, GUS, GFP

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Foito, Alexandre. « A metabolomics-based approach to study abiotic stress in Lolium perenne ». Thesis, University of Dundee, 2010. https://discovery.dundee.ac.uk/en/studentTheses/897810b2-4b52-43a8-a687-d21fef3a6d1e.

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In the United Kingdom and Ireland, a major percentage of fertilized agricultural area is devoted to grasslands, which helps to support the associated milk and beef production industries. In temperate grasslands, perennial ryegrass (L. perenne) is the major forage grass and this species is particularly suitable as a forage grass due to its high yield and digestibility, when compared with other species. However, perennial ryegrass is not well adapted to abiotic stress conditions which are likely to occur in its natural environment. Some of the abiotic stress factors which have significant impacts on plant growth and development include water and nutrient availability. Therefore, this project set out to unravel some of the mechanisms involved in the adaptation of perennial ryegrass to limited water, phosphorous and nitrogen. In order to understand the metabolic mechanisms acting in response to these stresses, metabolite profiling was performed using GC-MS. Furthermore, for the water- and phosphorous-limitation studies this approach was complemented with transcript analysis.In order to study water-limitation a hydroponics system supplemented with polyethyleneglycol (PEG) was used to induce water-limitation for a period of one-week. A clear difference in the metabolic profiles of the leaves of plants grown under water stress was observed. Differences were principally due to a reduction in fatty acid levels in the more water stress-susceptible genotype Cashel and an increase in sugars and compatible solutes in the drought-tolerant PI 462336 genotype. Sugars exhibiting a significant increase included, raffinose, trehalose, glucose, fructose and maltose. Raffinose was identified as the metabolite exhibiting the largest accumulation under water-stress in the more tolerant genotype and may represent a target for engineering superior drought tolerance or form the basis of marker-assisted breeding in perennial ryegrass. The metabolomics approach was combined with a transcriptomics approach in the water stress tolerant genotype PI 462336 which identified genes in perennial ryegrass that were regulated by this stress.The characterization of the response to phosphorus-limitation was performed in a hydroponics system containing two solutions with different levels of phosphorus. Samples were collected from the roots and leaves of two genotypes 24 hours after being exposed to stress. Internal phosphate concentrations were reduced and significant alterations were detected in the metabolome and transcriptome of two perennial ryegrass genotypes. Results indicated a replacement of phospholipids with sulfolipids in response to P deficiency and that this occurs at the very early stages of P deficiency in perennial ryegrass. Additionally, the results suggested the role of glycolytic bypasses and the re-allocation of carbohydrates in response to P deficiency The characterization of the metabolic response of L. perenne leaves to different levels of nitrogen supply was performed for seven different genotypes with variability in the regrowth response rate to nitrogen supply in a hydroponics system. This facilitated the identification of common mechanisms of response between genotypes to nitrogen. The metabolic response observed included modifications of the lipid metabolism, as well as alterations of secondary aromatic metabolite precursors in plants exposed to nitrogendeficit. In contrast, plants grown in a nitrogen saturated media appeared to modify to some extent the metabolism of ascorbate. Additionally, it was found that amino acid levels increased with increasing concentrations of nitrogen supplied. This study suggested that the involvement of secondary metabolism, together with lipid and ascorbate metabolism, is of crucial importance in the early-adaptation of perennial ryegrass plants to different levels of nitrogen supply.

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Martins, Celia Marilia. « The expression of Bt Cry1Ac in transformed cotton under abiotic stress ». Pretoria : [s.n.], 2006. http://upetd.up.ac.za/thesis/available/etd-11032008-121447.

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Njokweni, Anathi Perseverence. « Comparative analysis of sugar-biosynthesis proteins of sorghum stems and the investigation of their role in hyperosmotic stress tolerance ». Thesis, University of the Western Cape, 2015. http://hdl.handle.net/11394/4110.

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Philosophiae Doctor - PhD
Sorghum bicolor (L.) Moench is an important cereal crop currently explored as a potential bio-energy crop due to its stress tolerance and ability to ferment soluble sugars. Physiological studies on sorghum varieties have demonstrated that part of drought tolerance is attributed to sugar accumulation in the sorghum stems. Despite the agronomic advantages of sorghum as a bio-energy crop, more research efforts towards the molecular elucidation of sorghum traits that confer drought tolerance are necessary. Particular focus on traits, which could potentially contribute to an efficient bio-energy production under environmental constraints, would be an added advantage. This study examined the role of sugar biosynthesis proteins in conferring tolerance to drought-induced hyperosmotic stress, and ultimately osmotic adjustment in sorghum varieties. Sorghum bicolor (L.) Moench varieties (ICSB338, ICSB73, ICSV213 and S35) with different levels of drought tolerance, were grown under watered conditions until early anthesis after which, a 10-day water deficit period was introduced

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Akhter, Sajjad Rabbani. « Molecular analysis of adsr36, a stress response gene in Poaceae ». Thesis, University of Newcastle Upon Tyne, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.341455.

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Duarte, Sierra Arturo. « Abiotic stress hormesis : hormetic stresses to maintain quality and enhance glucosinolates and phenolic compounds in broccoli (Brassica oleracea var. italica) during storage ». Doctoral thesis, Université Laval, 2015. http://hdl.handle.net/20.500.11794/26529.

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Le brocoli (Brassica oleracea var. italica) est un légume devenu populaire grâce à ses caractéristiques nutritionnelles et bioctives qui sont associées entre autres à la prévention de certaines maladies chroniques. L'utilisation de stress abiotiques tels que UV-C comme traitement de pré-entreposage a montré un grand potentiel pour l'induction de la résistance aux maladies et la préservation de la qualité des produits frais, et il est de plus en plus évident qu'il existe un potentiel pour améliorer les métabolites secondaires. L'objectif de ce travail a été, d'abord, d'établir si divers stress abiotiques, UV-B, UV-C, la chaleur, l'ozone, le peroxyde d'hydrogène, l'éthanol, et méthyl jasmonate (MeJA), induisent le phénomène d’hormèse. L'effect de ces traitements sur certains paramètres associés à la qualité des fleurons de brocoli tels que: la couleur, la perte de poids, la teneur en glucosinolates et en composés phénoliques. La chaleur et l'éthanol ont été les meilleurs traitements pour le retarder le jaunissement des fleurons, mais UV-C et UV-B étaient également efficaces pour maintenir la couleur verte de fleurons dans l’entreposage. D'autre part, la capacité antioxydant des fleurons a été principalement renforcée par les traitements d’UV-B et de chaleur. Le paramètre le plus important dans cette recherche était la teneur en glucosinolates de fleurons qui a été influencé positivement par le traitement à l’ozone et au peroxyde d'hydrogène, et dans une moindre mesure par le traitement d’UV-B. Il a été conclu que les stress abiotiques peuvent influencer favorablement soit la qualité ou l’augmentation de glucosinolates dans les fleurons pendant l’entreposage, mais pas le deux. Parmi les agents stressants utilisés, la lumière UV-B a été le plus efficace à maintenir la qualité et à induire une augmentation des composantes phytochimiques dans le broccoli.
Broccoli (Brassica oleracea var. Italica) has become popular thanks to its health properties that are associated with the prevention of certain chronic diseases. The use of abiotic stresses such as UV-C as pre-storage treatment has shown great potential for induction of disease resistance in and preservation of quality of fresh produce, and it is becoming increasingly clear that there is potential for enhancing secondary metabolites. The objective of this work was, first, to establish whether various abiotic stresses, UV-B UV-C, heat, ozone, hydrogen peroxide, ethanol, and the plant signalling molecule, methyl jasmonate (MeJA), may induce hormesis in broccoli florets on color retention response; and second, to determine the effect of various abiotic stresses on quality, mainly color retention and weight loss; the contents of glucosinolates and phenolic compounds in florets during storage. Heat and ethanol were the best treatments for delaying yellowing florets, but UV-C and UV-B were also effective at a lower extent. On the other hand, the antioxidant capacity of the florets was mostly enhanced by UV-B and heat treatments. The most important enquiry in this research was the augmentation of glucosinolates titers, which was influenced by the treatment with ozone and hydrogen peroxide, and to a less extent by UV-B. It was concluded that abiotic stresses could influence favourably either the quality or the enhancement of glucosinolates in broccoli during storage and not both. Among the considered stressing factors, UV-B was the most effective for maintenance of quality as well as to elevate the levels of phytochemicals in broccoli.

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Elhaj, Abobakir Ali. « Molecular and physiological investigations of arabidopsis insertional mutant lines under abiotic stresses ». Thesis, University of Newcastle Upon Tyne, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.578289.

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Salt, cold, and drought are major abiotic stresses that impact plants and agricultural crops. Many plants and crops are able to increase their ability to survive these and other stresses by altering gene expression. Using the Arabidopsis model plant in studying gene function and regulation is of crucial importance to plant genetics and biotechnology. Our objective was to study plant survival and stress tolerance in Arabidopsis T-DNA lines and, also chemically mutagenized and RNAi lines, for specific genes that are hypothesised or expected to have a role in at least one of the known abiotic stresses. The selection of genes was based on some previous research including QTL analysis. I included in my investigations OSMl, CHXl7, KUPl, bHLH033, CBF4, dreb2a and the NW20 and N163 lines of ERECTA. Other non-mutated genes such as COR 78, DREB2A, CBFl, CBF3, CBF4, and OSMl were used to study the specificity in gene expression in Arabidopsis leaf and epidermal tissues under a combination of cold and osmolytes. The insertional mutant analysis showed that T-DNA can be located in a different site than the one shown in database and sometimes parts of the T-DNA left-border-sequence were absent. Most of the targeted Arabidopsis mutants showed a normal Mendelian pattern of segregation with the one exception of the CBF4 insertional mutant population. RT-PCR transcript detection of bHLH and DREB2A indicated that wild-type Arabidopsis in our growth environment expressed only one splice form of each of these genes rather than the two described by the TAIR and MIPS databases. Stress results indicated that inserting T-DNA within the Arabidopsis genome for a specific gene can lead to negative or positive effects on the gene's expression and plant survival. Investigation of the role of OSMl in cold tolerance indicated that the mutant plants were more tolerant to cold as measured by plant survival and electrolyte leakage. The higher expression of OSMl gene in the mutant plants has driven me to search in the promoter region of OSMl at OSM1::T-DNA junction. The results revealed the presence of different known eis-acting elements which might have affected plant survival. Using RNAi lines for OSMl (gene expression was not tested) is also consistent with the idea that this gene has a role in cold stress. Even though the high transcripts accumulation of bHLH (lCE2) in the mutant line was discovered, there was only slight difference between homozygous and wild type plants in response to cold. DREB2A, which is well known for its dehydration involvement, was tested under cold. Using dreb2a mutant for cold stress revealed that Salt stress tolerance was obtained with osml, ehx17, and kupl mutants as measured by the high average of plant survival. Mineral content was measured in leaves and roots of CHX17 and KUP 1 mutant and wild type plants under salt conditions. The mutant plants accumulated less sodium and higher potassium especially in roots compared to wild type. Also, roots accumulated more calcium and magnesium than the wild type. These results are clearly consistent with the higher survival in kupl mutant and may indicate a correlation with the salt tolerance in ehx17. Also, the high sensitivity to salt stress was strongly linked to some phenotypic and developmental changes, such as leaf wilting, rolling, chlorosis, and desiccation. Mutant plants that had higher survival developed dark leaf colour which probably indicates anthocyanin accumulation. A higher level of expression of genes in some mutant lines than in the wild type lines, linked with higher plant survival indicated there might be some eis-acting elements in the inserted T-DNA that were influencing stress tolerance. Compared to NW20 Landsberg ereeta line, carrying the chemically produced mutant, N163 plants, which carry wild-type ERECT A gene, exhibited more plant survival under salt stress especially at an older growth stage. Abstract IV covering plants during cold acclimation increased plant's sensitivity to cold compared to uncovered plants. This suggests that the role of DREB2A in cold acclimation probably is not through water stress signalling per se but other signalling must be involved. Also, drought stress was studied and was limited to CBF4 gene. The gene expression of CBF4 in the mutant was greatly reduced. However, plant survival under drought was not affected by the mutation. Gene expression-specificity of some cold regulated genes in epidermis and leaves of Arabidopsis wild type was studied under sugar and sorbitol with or without minerals. COR 78, DREB2A, CBF1, Eli-l-o; ACT2, and ACT8 were more highly expressed under cold in epidermis than in leaves. This expression was often several-fold higher when sucrose at 90 mM with mineral salts was supplied. CBF3 also showed a higher level of transcript accumulation by cold in epidermis than in leaves but both tissues exhibited similar and higher expression with sucrose at 40mM than the control and 90mM of sucrose with minerals. It seemed that removing minerals from sugar solution reduced the gene expression but epidermal tissues conserved the preference of most genes to be expressed in higher level (relative to total RNA) than leaves. Sorbitol at 90mM with minerals highly affected the expression of CBFl and CBF3 apart from type of tissue and reduced the expression of DREB2A, CBF4, and ACT8 in both tissues. OSMl had differential gene expression by different treatments. It showed slightly higher expression in epidermis with cold treatment and its expression was completely diminished in leaves at 90mM of sorbitol with minerals. These results indicate the regulatory role of sugar in cold- induced gene expression of several genes in epidermis which reflects its importance in stress tolerance. Abstract v All in all, using T-DNA can affect plant survival and alter gene expression in ways which can be interpreted as a direct or non-direct link in the overall stress tolerance. These investigations have added new facts to understanding stress tolerance in plants but others remain to be more deeply tested. A novel observation was that the T-DNA in the promoter can increase the regulation of gene expression and stress tolerance and this may be due to stress response elements in the T-DNA. Abstract

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Condorelli, Giuseppe Emanuele <1987&gt. « Genetic dissection of resistance to abiotic and biotic stresses in durum wheat ». Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2020. http://amsdottorato.unibo.it/9223/1/Condorelli_Giuseppe%20Emanuele_tesi.pdf.

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This thesis was aimed to investigate the genetic response to abiotic and biotic stresses in durum wheat (Triticum turgidum L. var. durum), a cultivated tetraploid subspecies used for the production of pasta, couscous and various types of bread. Two research areas were focused: i) the high-throughput phenotyping (HTP) to detect novel drought tolerance quantitative trait loci (QTL) clusters and ii) the Kompetitive Allele Specific Polymerase chain reaction (KASP) marker development for the genetic dissection of Furarium head blight (FHB) resistance. Concerning the first area, I investigated drought adaptive traits on durum wheat elite accessions at Maricopa Agricultural Center (University of Arizona, US) which provided the experimental field and the high-throughput phenotyping platforms. The genome-wide association study (GWAS) detected thirty-one QTL clusters for two or more drought adaptive traits unrelated to the major loci responsible for phenology and plant height. Twelve of them overlapped with the major QTL for grain yield and related traits previously reported in studies carried out across a broad range of soil moisture availability and field drought conditions in wheat. Concerning the second area, I investigated two plant materials: i) 130 durum wheat accessions artificially inoculated with Fusarium culmorum and F. graminearum species and evaluated for incidence (INC), severity (SEV), FHB index, Fusarium-damaged kernels (FDK) and deoxynivalenol (DON) content; ii) 165 F6 recombinant inbred lines (RILs) from the cross between the cultivars Simeto and Levante evaluated for SEV using FG as inoculum. The genetic dissection led to sixteen QTL clusters, in part unrelated to the phenology and unknown in bread wheat, from which specific loci significantly influenced DON content. The haplotype analysis allowed me to validate KASP Single Nucleotide Polymorphisms (SNPs) suitable for marker-assisted selection (MAS) programs and to select cultivars for resistance/tolerance to DON content and other FHB traits.

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Peñalosa-Barbero, Andrés. « New signalling network in plant abiotic stress discovered through a genetic approach ». [S.l. : s.n.], 2004. http://deposit.ddb.de/cgi-bin/dokserv?idn=97211131X.

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