Thèses : « Plant development and stress response »

1

Cao, Jingyi. « CELL TYPE-SPECIFIC ALTERNATIVE POLYADENYLATION IN ARABIDOPSIS DURING DEVELOPMENT AND STRESS RESPONSE ». Miami University / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=miami1492702815819455.

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O'Hara, L. E. « The role of trehalose 6-phosphate in the regulation of plant development and stress response ». Thesis, University College London (University of London), 2014. http://discovery.ucl.ac.uk/1427275/.

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Prevailing environmental conditions impose limitations on the availability nutrients and photosynthetic rate of plants. Therefore, plants possess an array of mechanisms to sense and signal endogenous energy and nutrient availability in order to coordinate growth and development appropriately. Trehalose 6-phosphate (T6P) has emerged as an important molecule with a role in signalling carbon availability for the regulation of plant growth and development. This thesis aimed to investigate the extent to which T6P contributes to the regulation of growth over the course of plant development, and also during environmental stress. Plants expressing bacterial trehalose 6-phosphophate synthase (TPS) or trehalose 6-phosphate phosphatase enzymes were used to investigate the effects of increased or decreased T6P contents on growth and development, respectively. It was shown that T6P is required for the normal growth rate and the response to increased carbon availability in early development. Additionally, evidence is provided to implicate T6P in a further role in the crosstalk between sucrose and light- and auxin-mediated growth. T6P was found to be necessary for the acceleration of senescence in response to increased carbon availability and it was shown that sugar signals were sensed during early development. The importance of carbon availability during and after cold stress was demonstrated: sucrose alleviated the damage to the photosynthetic apparatus in mutants of starch synthesis and cold acclimation. It was also shown that T6P, via its effect on sucrose non-fermenting-1-related kinase-1 (SnRK1), is important in the growth recovery following cold stress which provokes sink limitation. A construct was created for the seed-specific over-expression of TPS behind the OLEOSIN1 promoter to alter levels of T6P in developing seeds. This approach may offer an effective method for improving seed yield and quality.

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Pirone, Claudia <1987&gt. « Disentangling the Role of Transitory Starch Storages in Plant Development and in Osmotic Stress Response ». Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2016. http://amsdottorato.unibo.it/7580/1/TESI_DOTTORATO_Claudia_Pirone.pdf.

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Starch is a polymer of D-glucose that plants accumulate as semi-crystalline and osmotically inert granules. Besides being the major energy storage in plants, starch is of primary importance also in human and animal diet, industry and biofuels production. Two kinds of starch, structurally indistinguishable, but different for location and rates of synthesis and degradation are found in plants: secondary starch (characterized by long term-accumulation and found in storage organs) and transitory starch (mainly located in chloroplasts, produced during the day and degraded the subsequent night to meet the energy demand of the plant). Due to its structure, several enzymes are required in starch biosynthesis and degradation, controlling distinct features of starch granules and conferring different physical-chemical properties. Here, the TILLING approach was used on the barley TILLMore population to identify new alleles in five genes related to secondary starch metabolism and known to be expressed in barley seeds. Moreover, the role in Arabidopsis development of the (phospho)glucan, water dikinase proteins (GWD1, GWD2, PWD), known to be involved in nighttime transitory starch degradation, was investigated. Other enzymes, such as β-amylase 1 (BAM1) and α-amylase 3 (AMY3), were demonstrated to be involved in diurnal transitory starch degradation in specialized cells or under stress conditions. Here, we demonstrated that carbon skeletons deriving from BAM1 diurnal degradation of transitory starch support the biosynthesis of proline, a compatible solute, required to face osmotic stress. Moreover, the behaviour of Arabidopsis BAM1 and AMY3 enzymes under oxidative treatments and the possible role of glutathionylation, a redox post-translational modification occurring mainly under stress conditions and promoted by ROS, were investigated. AtBAM1 and AtAMY3 were found to be sensitive to oxidants and glutathionylated, with a modulatory and protective effect on protein activity.

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Pirone, Claudia <1987&gt. « Disentangling the Role of Transitory Starch Storages in Plant Development and in Osmotic Stress Response ». Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2016. http://amsdottorato.unibo.it/7580/.

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Starch is a polymer of D-glucose that plants accumulate as semi-crystalline and osmotically inert granules. Besides being the major energy storage in plants, starch is of primary importance also in human and animal diet, industry and biofuels production. Two kinds of starch, structurally indistinguishable, but different for location and rates of synthesis and degradation are found in plants: secondary starch (characterized by long term-accumulation and found in storage organs) and transitory starch (mainly located in chloroplasts, produced during the day and degraded the subsequent night to meet the energy demand of the plant). Due to its structure, several enzymes are required in starch biosynthesis and degradation, controlling distinct features of starch granules and conferring different physical-chemical properties. Here, the TILLING approach was used on the barley TILLMore population to identify new alleles in five genes related to secondary starch metabolism and known to be expressed in barley seeds. Moreover, the role in Arabidopsis development of the (phospho)glucan, water dikinase proteins (GWD1, GWD2, PWD), known to be involved in nighttime transitory starch degradation, was investigated. Other enzymes, such as β-amylase 1 (BAM1) and α-amylase 3 (AMY3), were demonstrated to be involved in diurnal transitory starch degradation in specialized cells or under stress conditions. Here, we demonstrated that carbon skeletons deriving from BAM1 diurnal degradation of transitory starch support the biosynthesis of proline, a compatible solute, required to face osmotic stress. Moreover, the behaviour of Arabidopsis BAM1 and AMY3 enzymes under oxidative treatments and the possible role of glutathionylation, a redox post-translational modification occurring mainly under stress conditions and promoted by ROS, were investigated. AtBAM1 and AtAMY3 were found to be sensitive to oxidants and glutathionylated, with a modulatory and protective effect on protein activity.

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Chávez, Martínez Ángel de Jesús. « Altered Levels of Glycosylated Sterols Affect Tomato Development and Stress Response ». Doctoral thesis, Universitat de Barcelona, 2020. http://hdl.handle.net/10803/673610.

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Los esteroles son una familia de compuestos triterpénicos que se presentan en forma libre (FS, por sus siglas en inglés) o conjugada, como ésteres (SE), glicósidos (SG) y acilglicósidos de esteroles (ASG). Los esteroles glicosilados (SG y ASG) y los FS son componentes de la membrana celular, donde en combinación con otros lípidos unidos a la membrana juegan un papel clave en la modulación de sus propiedades y función. Las esterol glicosiltransferasas (SGT) catalizan la glicosilación del grupo hidroxilo en la posición C-3 de los FS para producir SGs. Trabajos previos realizados en nuestro grupo de investigación han demostrado que la familia de genes SGT en tomate consta de 4 miembros (SlSGT1-4) los cuales se expresan diferencialmente. Siendo SlSGT1 el gen más expresado en los diferentes órganos del tomate, mientras que la expresión del gen SlSGT4 es apenas detectable en condiciones basales, pero se regula positivamente en respuesta a diferentes estímulos de estrés. Aunque las cuatro SlSGT codifican enzimas SlSGT funcionales, la contribución individual de cada isoforma al perfil de esteroles glicosilados, así como el impacto de una composición alterada de estos esteroles conjugados en plantas de tomate, están lejos de comprenderse. En este proyecto de tesis investigamos como los niveles alterados de esteroles glicosilados, obtenidos por silenciamiento de la expresión de SlSGT1 mediada por microARN artificial o sobreexpresión de SlSGT4 afectan el crecimiento y desarrollo del tomate y su respuesta al estrés. En el estado vegetativo, el silenciamiento de SlSGT1 dio como resultado un fenotipo pleiotrópico caracterizado por plantas más cortas y con menor área foliar. También se observó una deducción del tamaño de los frutos. En ambos casos, las alteraciones fenotípicas se asociaron a una disminución en el contenido de esteroles glicosilados, debido principalmente a una disminución en los niveles de SG, la cual fue paralela a una acumulación de FS. Por otro lado, los resultados obtenidos sugieren cierta preferencia de SlSGT1 por el estigmasterol como sustrato para la glicosilación, y demuestran que está isoforma de SGT de tomate no está involucrada en la síntesis de glicoalcaloides esteroideos (SGA), un tipo de metabolitos especializados que participan en la respuesta de defensa de las plantas. También se estudió la respuesta de las plantas silenciadas SlSGT1 al estrés biótico (infección por Botrytis cinerea) y abiótico (frio), y se observó una mayor resistencia a la infección por B. cinera, pero una menor tolerancia al estrés por frio. Estos resultados demuestran que los SG juegan un papel en el desarrollo de las plantas y frutos de tomate, así como en la respuesta al estrés. Para entender mejor los mecanismos moleculares que conllevan a estos efectos fisiológicos, se realizaron experimentos de secuenciación de ARN (RNA-seq) en hojas y frutos de las líneas silenciadas SlSGT1, los resultados de este análisis muestran una regulación negativa de varios genes involucrados en los procesos de desarrollo y respuesta a diferentes estímulos que podrían ayudar a explicar algunos de los fenotipos observados. Además, generamos plantas transgénicas de tomate sobreexpresando constitutivamente SlSGT4. Sorprendentemente, los niveles de esteroles glicosilados en estas líneas transgénicas fueron más bajos que en las plantas de tipo silvestre, probablemente como resultado de una reducción en los niveles de SlSGT1 concomitantes detectados en estas líneas. La caracterización fenotípica de estas plantas mostró que los cambios en la expresión de SlSGT4, como los observados en el silenciamiento de SlSGT1, afectan el crecimiento de las plantas y frutos de tomate, pero también la producción y germinación de semillas. En conjunto los resultados obtenidos en este trabajo muestran evidencias contundentes del importante papel que juegan los esteroles glicosilados en el crecimiento y desarrollo de las plantas y los frutos de tomate, así como en la respuesta de las plantas a estreses bióticos y abióticos, y sienta las bases para futuros estudios dirigidos a comprender con más detalle los mecanismos moleculares por los cuales los esteroles glicosilados afectan estos procesos fisiológicos.

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Pomeranz, Marcelo Christian. « The Role of the AtTZF1 Tandem CCCH Zinc Finger Gene in Plant Growth, Development, and Stress Response ». The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1299525118.

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Litholdo, Junior Celso Gaspar. « Characterisation of microRNA gene families in Arabidopsis ». Thesis, The University of Sydney, 2014. http://hdl.handle.net/2123/12056.

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MicroRNAs (miRNAs) are a class of small non-coding RNA, that guide RNA silencing of a complementary target mRNA. MiRNAs have been shown to act as post-transcriptional regulators, directing several essential processes in the plant. Despite the importance of miRNAs, the functions of many remain poorly characterized. During my research, two uncharacterised MIR gene families, one conserved and one non-conserved, were investigated. The hypothesis that highly conserved miRNAs regulate architectural and developmental processes while newly evolving miRNAs regulate temporal responses to environmental stresses is examined. The non-conserved MICRORNA163 (MIR163) has recently evolved by gene duplication events in the genus Arabidopsis. It was shown that miR163 regulates the expression of the S-ADENOSYL-METHYLTRANSFERASE (SAMT) family. Hormone treatment, fungal infection, wounding and herbivory each resulted in changes in miR163 and SAMT gene expression, indicating that this miRNA/target association is involved in stress adaptation responses. The highly conserved MIR394 family regulates the F-box protein gene LEAF CURLING RESPONSIVENESS (LCR) and disruption in the miR394/LCR association leads to developmental alterations in leaf polarity and shoot apical meristem organisation. Proteomic analyses identified MAJOR LATEX PROTEINS (MLPs) as probable targets of LCR F-box regulation, suggesting that the biological role of miR394 is to ensure de-repressed expression of MLPs in the shoot apical meristem, and that this is required for the stem cell homeostasis during normal development.

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Prenger, Jessica J. « Development of a Plant Response Feedback Irrigation Control System Based on Crop Water Stress Index and Evapotranspiration Modeling ». The Ohio State University, 2003. http://rave.ohiolink.edu/etdc/view?acc_num=osu1419601844.

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Frietsch, Sabine. « The role of Cyclic Nucleotide-Gated Channels (CNGC) in plant development and stress responses in Arabidopsis thaliana ». [S.l. : s.n.], 2006.

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Davies, Huw Alun. « A family of glycoproteins from the petioles of Brassica campestris with potential roles in plant development and stress responses ». Thesis, University of East Anglia, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.317996.

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11

Zheng, Bo. « Characterisation of the Clp Proteins in Arabidopsis thaliana ». Doctoral thesis, Umeå : Department of Plant Physiology, Umeå Plant Science Centre, Umeå University, 2003. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-99.

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Steinebrunner, Iris, Uta Gey, Manuela Andres, Lucila Garcia et Daniel H. Gonzalez. « Divergent functions of the Arabidopsis mitochondrial SCO proteins : HCC1 is essential for COX activity while HCC2 is involved in the UV-B stress response ». Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2014. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-147367.

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The two related putative cytochrome c oxidase (COX) assembly factors HCC1 and HCC2 from Arabidopsis thaliana are Homologs of the yeast Copper Chaperones Sco1p and Sco2p. The hcc1 null mutation was previously shown to be embryo lethal while the disruption of the HCC2 gene function had no obvious effect on plant development, but increased the expression of stress-responsive genes. Both HCC1 and HCC2 contain a thioredoxin domain, but only HCC1 carries a Cu-binding motif also found in Sco1p and Sco2p. In order to investigate the physiological implications suggested by this difference, various hcc1 and hcc2 mutants were generated and analyzed. The lethality of the hcc1 knockout mutation was rescued by complementation with the HCC1 gene under the control of the embryo-specific promoter ABSCISIC ACID INSENSITIVE 3. However, the complemented seedlings did not grow into mature plants, underscoring the general importance of HCC1 for plant growth. The HCC2 homolog was shown to localize to mitochondria like HCC1, yet the function of HCC2 is evidently different, because two hcc2 knockout lines developed normally and exhibited only mild growth suppression compared with the wild type (WT). However, hcc2 knockouts were more sensitive to UV-B treatment than the WT. Complementation of the hcc2 knockout with HCC2 rescued the UV-B-sensitive phenotype. In agreement with this, exposure of wild-type plants to UV-B led to an increase of HCC2 transcripts. In order to corroborate a function of HCC1 and HCC2 in COX biogenesis, COX activity of hcc1 and hcc2 mutants was compared. While the loss of HCC2 function had no significant effect on COX activity, the disruption of one HCC1 gene copy was enough to suppress respiration by more than half compared with the WT. Therefore, we conclude that HCC1 is essential for COX function, most likely by delivering Cu to the catalytic center. HCC2, on the other hand, seems to be involved directly or indirectly in UV-B-stress responses.

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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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Hernández, García Jorge. « Ancestral Functions of DELLA Proteins ». Doctoral thesis, Universitat Politècnica de València, 2021. http://hdl.handle.net/10251/169370.

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[ES] Las plantas necesitan acomodar su crecimiento a las condiciones ambientales. Con el objetivo de ajustar su desarrollo a las señales externas, usan una serie de mecanismos moleculares. Uno de estos son las rutas de señalización hormonal, que participan en integrar la información externa con programas de desarrollo propios. Una de las hormonas más relevantes en la biología vegetal son las giberelinas (GAs). La señalización por GAs se inicia con la percepción de la hormona a través del receptor GID1, y continúa por la degradación de las reguladoras transcripcionales DELLA. Sin embargo, solo las plantas vasculares tienen un sistema de percepción de GAs completo. Entender la relevancia de la señalización por GAs requiere estudiar cómo se ensambló la ruta y qué funciones atribuidas a las GAs estaban ya codificadas en las proteínas DELLA ancestrales. Aquí mostramos mediante análisis filogenéticos y bioquímicos que las proteínas DELLA emergieron inequívocamente en un ancestro común de las plantas terrestres, y que el reclutamiento de las DELLAs al módulo de percepción de GAs depende de la presencia de un dominio de transactivación conservado que fue co-optado por el receptor GID1 ancestral para actuar como un degrón dependiente de GAs. Este dominio de transactivación parece regular la co-activación transcripcional de genes concretos por las DELLAs en todas las plantas terrestres mediante el reclutamiento de complejos Mediator a través de su subunidad MED15. Por último, nos hemos centrado en entender las funciones de las proteínas DELLA en briófitas, un clado sin señalización por GAs. Hemos descubierto el rol de la DELLA de Marchantia polymorpha como coordinadora entre las respuestas de crecimiento y estrés, sugiriendo que dicha función estaba ya codificada en proteínas DELLA del ancestro común de plantas terrestres y se ha mantenido durante más de 450 millones de años.
[CA] Les plantes necessiten acomodar el seu creixement a les condicions ambientals. Amb l'objectiu d'ajustar el seu desenvolupament als senyals externs, usen una sèrie de mecanismes moleculars. Un d'aquests són les rutes de senyalització hormonal, que participen en integrar la informació externa amb programes de desenvolupament propis. Una de les hormones més rellevants en la biologia vegetal són les giberel·lines (GAs). La senyalització per GAs s'inicia amb la percepció de l'hormona a través del receptor GID1, i continua per la degradació de les reguladores transcripcionals DELLA. No obstant això, només les plantes vasculars tenen un sistema complet de percepció de GAs. Entendre la rellevància de la senyalització per GAs requereix estudiar com es va assemblar la ruta i quines funcions atribuïdes a les GAs estaven ja codificades en les proteïnes DELLA ancestrals. Ací mostrem mitjançant anàlisis filogenètiques i bioquímiques que les proteïnes DELLA van emergir inequívocament en un ancestre comú de les plantes terrestres, i que el reclutament de les DELLAs al mòdul de percepció de GAs depén de la presència d'un domini de transactivació conservat que va ser co-optat pel receptor GID1 ancestral per a actuar com un degró dependent de GAs. Aquest domini de transactivació sembla regular la co-activació transcripcional de gens concrets per les DELLAs en totes les plantes terrestres mitjançant el reclutament de complexos Mediator a través de la seua subunitat MED15. Finalment, ens hem centrat en entendre les funcions de les proteïnes DELLA en briòfites, un clade sense senyalització per GAs. Hem descobert el rol de la DELLA de Marchantia polymorpha com a coordinadora entre les respostes de creixement i estrés, suggerint que aquesta funció estava ja codificada en proteïnes DELLA de l'ancestre comú de plantes terrestres i s'ha mantingut durant més de 450 milions d'anys.
[EN] Plants need to accommodate their growth habits to environmental conditions. For this aim, several mechanisms are used to adjust developmental responses to exogenous signals. Among them, hormonal signalling pathways participate by integrating external information with endogenous programs. One of the most relevant hormones in plant biology are gibberellins (GAs). GA signalling involves perception of the hormone by the GA receptor GID1 and subsequent degradation of the DELLA transcriptional regulators. However, only vascular plants possess a full GA perception system. Understanding the relevance of GA signalling requires elucidating how this pathway was assembled and which of the functions attributed to GAs were encoded in the ancestral DELLA proteins. Here we show by phylogenetic and biochemical analyses that DELLA proteins emerged unequivocally in a land plant common ancestor and that their recruitment into the GA-perception module relies in the presence of a conserved transactivation domain co-opted by an ancestral GID1 receptor to act as a GA-dependent degron. Moreover, this transactivation domain seems to regulate DELLA-dependent transcriptional co-activation of selected target genes by recruitment of Mediator complexes through the MED15 subunit in all land plants. Finally, we have focused on understanding the functions of DELLA proteins in bryophytes, a clade with no GA signalling. We have uncovered the role of Marchantia polymorpha DELLA protein as a coordinator between growth and stress responses, suggesting that this function was already present in the DELLA protein of a land plant common ancestor and has been maintained for over 450 millions of years.
La realización de esta tesis doctoral ha sido posible gracias a una ayuda para contratos predoctorales FPU (FPU15/01756), dos Ayudas para Estancias Breves FPU (EST17/00237, IPS2, París; EST18/00400, WUR, Wageningen), una ayuda EMBO Short-Term (ASTF 8239, WUR, Wageningen), y la financiación MSCA H2020 RISE para desplazamientos en el contexto del proyecto SIGNAT (RISE Action 644435, PUC, Santiago). Así mismo, el grueso del trabajo experimental incluido ha sido financiado por el proyecto HUBFUN del MINECO (BFU2016-80621-P)
Hernández García, J. (2021). Ancestral Functions of DELLA Proteins [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/169370
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Atkinson, Nicola Jane. « Plant molecular response to combined drought and nematode stress ». Thesis, University of Leeds, 2011. http://etheses.whiterose.ac.uk/2131/.

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Plants are adapted to respond to precise environmental stress conditions, activating specific molecular and physiological changes in order to minimise damage. Response to multiple stresses is therefore different to that to individual stresses. Simultaneous biotic and abiotic stress conditions are of particular interest, as the molecular signalling pathways controlling each interact and antagonise one another. Understanding such processes is crucial for developing broad-spectrum stress-tolerant crops. This study characterised the molecular response of plants to the concurrent stresses of drought (abiotic stress) and infection with plant-parasitic nematodes (biotic stress). Drought stress increased susceptibility to infection with Heterodera schachtii in Arabidopsis thaliana. The whole-genome transcriptome response to these stresses was analysed using microarrays. Each stress induced a particular subset of differentially expressed genes. A novel programme of gene expression was activated specifically in response to a combination of drought and nematode stress, involving 2394 differentially regulated genes. A diverse range of processes was found to be important in the response to multiple stresses, including plant hormone signalling, activation of transcription factors, cell wall modification, production of secondary metabolites, amino acid metabolism and pathogen defence signalling. Ten multiple stress-induced candidate genes were selected and their functions investigated using over-expression lines and loss-of-function mutants. Altered susceptibility to drought stress (TCP9, AZI1, RALFL8) and nematode infection (TCP9, RALFL8, ATMGL, AZI1) was observed in several of these lines. The effect of combined drought and nematode infection on nutritional parameters of tomato fruits was analysed. Drought stress lengthened flowering time and negatively affected carotenoid accumulation. Infection with Meloidogyne incognita reduced yield and ripening time and had a positive effect on the accumulation of phenolic compounds. The stresses in combination increased fruit sugar content. This work comprises the first whole-genome transcriptome study into combined abiotic and biotic stress. The results highlight the importance of studying stress factors in combination.

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Nalam, Vamsi J. « 9-Lipoxygenase Oxylipin Pathway in Plant Response to Biotic Stress ». Thesis, University of North Texas, 2012. https://digital.library.unt.edu/ark:/67531/metadc115127/.

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The activity of plant 9-lipoxygenases (LOXs) influences the outcome of Arabidopsis thaliana interaction with pathogen and insects. Evidence provided here indicates that in Arabidopsis, 9-LOXs facilitate infestation by Myzus persicae, commonly known as the green peach aphid (GPA), a sap-sucking insect, and infection by the fungal pathogen Fusarium graminearum. in comparison to the wild-type plant, lox5 mutants, which are deficient in a 9-lipoxygenase, GPA population was smaller and the insect spent less time feeding from sieve elements and xylem, thus resulting in reduced water content and fecundity of GPA. LOX5 expression is induced rapidly in roots of GPA-infested plants. This increase in LOX5 expression is paralleled by an increase in LOX5-synthesized oxylipins in the root and petiole exudates of GPA-infested plants. Micrografting experiments demonstrated that GPA population size was smaller on plants in which the roots were of the lox5 mutant genotype. Exogenous treatment of lox5 mutant roots with 9-hydroxyoctadecanoic acid restored water content and population size of GPA on lox5 mutants. Together, these results suggest that LOX5 genotype in roots is critical for facilitating insect infestation of Arabidopsis. in Arabidopsis, 9-LOX function is also required for facilitating infection by F. graminearum, which is a leading cause of Fusarium head blight (FHB) disease in wheat and other small grain crops. Loss of LOX1 and LOX5 function resulted in enhanced resistance to F. graminearum infection. Similarly in wheat, RNA interference mediated silencing of the 9-LOX homolog TaLpx1, resulted in enhanced resistance to F. graminearum. Experiments in Arabidopsis indicate that 9-LOXs promote susceptibility to this fungus by suppressing the activation of salicylic acid-mediated defense responses that are important for basal resistance to this fungus. the lox1 and lox5 mutants were also compromised for systemic acquired resistance (SAR), an inducible defense mechanism that is systemically activated throughout a plant in response to a localized infection. the lox1 and lox5 mutants exhibited reduced cell death and delayed hypersensitive response when challenged with an avirulent strain of the bacterial pathogen Pseudomonas syringae pv tomato. LOX1 and LOX5 functions were further required for the synthesis as well as perception of a SAR-inducing activity present in petiole exudates collected from wild-type avirulent pathogen-challenged leaves. Taken together, results presented here demonstrate that 9-LOX contribute to host susceptibility as well as defense against different biotic stressors.

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Wang, Lijun. « Physiological response of Kentucky bluegrass under salinity stress ». DigitalCommons@USU, 2013. https://digitalcommons.usu.edu/etd/1492.

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Salinity is a major abiotic stress in plant agriculture which reduces seed germination, vegetative growth, and flowering, and limits crop productivity world-wide. Salinity causes water deficit, ion toxicity, and nutrient deficiency in plants, which can result in cellular damage, growth reduction, and even death. Kentucky bluegrass (Poa pratensis L.) is the most widely used cool-season species in cool-arid climates; however it has relatively poor salt-tolerance. Thus the development of Kentucky bluegrass genotypes with increased salt tolerance is of interest to turf breeders. One impediment to selection towards this goal is finding an efficient and accurate method to evaluate the salt tolerance. The objective of this study was to examine physiological responses to salt stress and to evaluate the genetic diversity among the accessions used in the research. Salt-tolerant accessions PI371768 (768) and PI440603 (603) and salt-sensitive varieties Midnight and Baron were exposed to four levels of salinity imposed by irrigating with salt solutions of 0 dS m-1 (control), 6 dS m-1, 12 dS m-1, and 18 dS m-1 or 24 dS m-1. Soil salinity was measured using Acclima Digital TDT sensors and grass response to the stress was measured using turf quality ratings, stomatal conductance, leaf water potential and electrolyte leakage. In general, turfgrass quality, stomatal conductance, and leaf water potential decreased while electrolyte leakage increased under salinity stress. Midnight and Baron exhibited greater changes in these measurements, indicating more sensitivity compared to 768 and 603. The 6 dS m-1 treatment had little effect on the salt-tolerant accessions. Salt tolerance of 603 and 768 was confirmed and likewise, salt sensitivity of Baron and Midnight was confirmed. The genetic similarity of all cultivars used in this study was very high. All of the evaluation measurements were highly correlated, with water potential and electrolyte leakage being the most reliable and accurate methods due to the low standard deviations. Due to more repeatable methods and less user error, electrolyte leakage and turfgrass quality are recommended methods for screening salt tolerance of turfgrasses.

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Del, Bianco Marta. « Context specificity of auxin response in plant development ». Thesis, University of Leeds, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.610902.

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The shoot apical meristem (SAM) is the source of all above ground organs in the plant. It can be divided into a central zone (CZ) and a surrounding ring region called peripheral zone (PZ). The CZ contains the stem cells, the organizing centre and undifferentiated stem cell daughters. In the peripheral zone, in response to auxin accumulation, cells begin to differentiate to give rise to lateral organs. Application of auxin to other parts of the SAM does not lead to the formation of leaves or flowers and, in fact, the CZ seems to be insensitive to auxin. These differences in responsiveness and output in the meristem zones can be attributed to differences in the auxin signalling network. To allow the identification and sampling of small and inaccessible tissues such as the meristem zones, protocols for the use of fluorescent and histochemical markers to guide Laser Capture Microdissection were developed. These new methods allowed the precise capture of specific plant cell-types in a manner that was compatible with subsequent extraction and amplification of RNA for RNA-Seq analysis. These novel tools together represent a valuable technology platform for future cell-type-specific analysis in other plant developmental contexts. In this work, these sampling techniques have lead to new insight into both meristem . regulation and auxin function in the SAM. Most interestingly, in terms of auxin signalling, it appears that the negative regulators of auxin response, JAAI2 and IAAI8, arc expressed specifically in the PZ and, unexpectedly y, their expression is down-regulated by auxin. Moreover, the gem: ontology analysis of the genes obtained by RNA-seq revealed an enrichment of genes involved in DNA synthesis and response to external stimuli in the PZ. This is consistent with the higher proliferation rate of the PZ cells and might suggest that environmental inputs are perceived in the PZ. which then affects the identity of the entire SAM. These data, together with detailed phenotypic analysis of multiple mutants involved in auxin signalling and meristem function, provide a framework for understanding the complex role of auxin in the regulation of lateral organ formation through the life of a plant.

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WANG, DAN. « Effects of CO2 and Nitrogen on Plant Response to Heat Stress ». University of Toledo / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1225299873.

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Wang, Dan. « Effects of CO₂ and nitrogen on plant response to heat stress / ». Connect to full text in OhioLINK ETD Center, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1225299873.

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Dissertation (Ph.D.)--University of Toledo, 2008.
Typescript. "Submitted as partial fulfillment of the requirements for The Doctor of Philosophy Degree in Biology (Ecology-track)." Bibliography: leaves 6-9, 29-35, 71-78, 111-118, 149-153.

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Milani, Manuela. « Cell stress response and hypoxia in breast cancer ». Thesis, University of Oxford, 2011. http://ora.ox.ac.uk/objects/uuid:74d3bf91-9888-4e9e-b5e1-7d5d2d476174.

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During severe hypoxia (<0.01% oxygen) the protein folding machinery becomes dysfunctional, resulting in the accumulation of unfolded proteins with consequent endoplasmic reticulum (ER) stress and activation of the unfolded protein response (UPR) and autophagy, a process involved in the physiological turnover of cytoplasmic components. The link between the UPR and autophagy is not clearly defined. The aim of this thesis is to investigate the role of the induction of UPR under severe hypoxia in tumour survival and resistance to therapy. The results of this research suggest that the activating transcription factor 4 (ATF4), a component of the PKR-like ER kinase (PERK) pathway, fundamental in the UPR, is required for the ER-stress induced upregulation of autophagy. Mechanisms other than hypoxia for UPR induction were investigated, using the proteasome inhibitor bortezomib (BZ). BZ treatment increased ATF4 protein levels in MCF7 cells, even transfected with short-interference RNA (siRNA) against the classical UPR activator PERK, suggesting that the proteasomal stabilization is likely the main mechanism for ATF4 protein accumulation. The induction of autophagy by BZ is dependent upon the upregulation of the microtubule-associated protein 1 light chain 3B (LC3B), an autophagy marker, by ATF4 and acts as a survival mechanism. Hypoxia, UPR and autophagy markers (such as Pimonidazole, carbonic anhydrases IX (CAIX), C/EBP homologous protein (CHOP) and LC3B) were evaluated by immunohistochemical approach in spheroids, xenografts models and breast cancer samples. CHOP immunohistochemical staining was performed in breast cancer sections from a series of patients. CHOP was expressed in cells surrounding necrotic areas. No correlation were found with clinical outcome and further studies are needed.

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Sun, Hong. « The effect of hydrodynamic stress on plant embryo development ». Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/33945.

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The effect of steady shear stress on somatic embryos were investigated in a flow chamber and evaluated at different time intervals using microscopy technique. The development of meristematic cell clusters, i.e. the immature embryos, into a polarized somatic embryo, and the effect on the localization of the suspensor cells that form during development of the immature embryos, were studied as a function of shear stresses. With the distribution and growth rate of the meristematic and suspensor cells, the effect of stress on the embryo development was established. Furthermore, the effect of shear stress on the cells at molecular level, the reaction of integrin-like proteins, the production of reactive oxygen species and the pore size of the cell walls involved in the shear stress responses, were investigated with molecular techniques. In general, shear stress inhibits meristematic cells growth. Meristematic cells grow fastest at shear rate of 86 s-1 among all the tested shear stress conditions. By combining the results of meristematic cells growth and suspensor cells formation, it suggests that there is a critical shear rate between 86 and 140 s-1, at which no suspensor cells form. The unidirectional flow with different shear stresses helps the polarized growth and the unidirectional alignment of suspensor cells. Reactive oxygen species and integrin-like protein are detected in the stressed cells as cellular responses to shear stresses. By monitoring the pore size and uptake time of cells to macromolecules with solute-exclusive experiments, it suggests that the stressed cells expedite the response to plasmolyzing components that are used to induce maturation treatment thus affect the response to maturation stimuli.

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Li, Xiaoqing. « Plant root development and hormone signalling during drought stress ». Thesis, Lancaster University, 2016. http://eprints.lancs.ac.uk/79357/.

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The plant root system is crucial for plant survival, growth and development, and it plays an important role in plant resistance to drought stress. Drought is one of the primary factors that restrict plant growth and yield, and its threat to crop yields will increase along with the growing food demand by the population of a world experiencing a changing climate. In response to drought in plants, various hormones are vital regulators, because they are able to manipulate plant development and in some cases minimise the adverse impact of drought. Therefore, understanding how the plant root system will adapt to a soil drying challenge is crucial. Of particular importance is the plant response to a non-lethal drought stress, which is often encountered in the field. Elucidation of the mechanisms underlying such responses, including hormonal regulations, may help crop scientists improve the plant performance under drought. A six-day progressive soil drying pot experiment was designed to examine the synchronisation of physiological responses in maize (Zea mays L.) roots and leaves during soil drying. It was found that maize roots showed earlier responses to soil drying than leaves in changing growth rates, water potentials and hormone levels. Root growth was stimulated at soil water content of 25−32% (ca. 41% in well-watered pots), while both root growth and leaf elongation were inhibited when soil water content was below 20%. Root abscisic acid (ABA) level gradually increased when soil water content was lower than 32% during soil drying. The stimulation and inhibition of root growth during soil drying may be regulated by root ABA, depending on the degree of the concentration increase. The ethylene release rates from leaves and roots were inhibited during soil drying, which occurred later than the increase in ABA levels. In a subsequent root phenotyping study on 14 maize genotypes, significant genetic variation was observed in root angle and size (root length, surface area and dry weight), and in the plasticity of these traits under mild and severe drought stress. Genotypes with a steeper root angle under well-watered conditions tended to display more promotion or less inhibition in root size under drought. Further analysis showed that combined traits of maize root angle, its plasticity and the root size plasticity under drought may be a better predictor for maize drought resistance than a single one of these traits. Moreover, root angle was found positively related to the leaf and root ABA levels and negatively related to the root tZ (a cytokinin) level under well-watered conditions. In another study on the crosstalk of drought-related hormones using the model plant Arabidopsis thaliana L., the biphasic responses of root elongation to ABA were confirmed, i.e. low external ABA concentrations stimulated root growth while high ABA concentrations inhibited it. Furthermore, ethylene and auxin were found to be involved in these responses. The inhibitory effect of high ABA levels on root growth was reduced or even eliminated when Arabidopsis was chemically treated to inhibit the ethylene biosynthesis or signalling, or to block auxin influx carriers. This was confirmed using mutants with blocked ethylene or auxin signalling, or a defect in the auxin influx carrier AUX1. On the other hand, the stimulatory effect of low ABA levels on root growth was lost when Arabidopsis seedlings were chemically treated to inhibit the auxin efflux carriers, and in mutants with blocked auxin signalling or with a defect in the PIN2/EIR1 auxin efflux carrier. These results indicate that ABA regulates root growth through two distinct pathways. The inhibitory effect that operates at high ABA concentrations is via an ethylene-dependent pathway and requires auxin signalling and auxin influx through AUX1. The stimulatory effect that operates at low ABA concentrations is via an ethylene-independent pathway and also requires auxin signalling and auxin efflux through PIN2/EIR1. This research contributes to our understanding of the responses of plant root system to different degrees of non-lethal drought stress, and it highlights the importance of root traits that may be important to plant drought resistance. The potential involvement of hormones (ABA, ethylene, auxin and cytokinin) in these processes is clarified. The knowledge gained may be integrated in novel crop management strategies to plan irrigation and help in the development of drought resistant crop varieties.

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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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Cook, Ritchard Matthew. « Changes in gene expression in response to abscisic acid and environmental stress ». Thesis, University of the West of England, Bristol, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.293362.

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Karunaratne, Asha Sajeewani. « Modelling the response of Bambara groundnut (Vigna subterranea (L.) Verdc) for abiotic stress ». Thesis, University of Nottingham, 2009. http://eprints.nottingham.ac.uk/10840/.

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Bambara groundnut (Vigna subterranea (L.) Verdc) is an indigenous legume that is still cultivated in subsistence agricultural systems in sub-Saharan Africa, despite the lack of any major research effort until recently. The crop is cultivated from local landraces as there are no true varieties of the species bred for specific traits. The variable and hostile climates in the region mean that annual yields of most rainfed crops including bambara groundnut are far below their agronomic or genetic potential. The lack of quantitative information on the eco-physiological responses of the crop to various abiotic factors has resulted in poor decision making on crop management practices especially in relation to sowing date and the selection of appropriate landraces for different locations. Modelling of bambara groundnut was initiated previously but there is still insufficient understanding of how growth and developmental processes can be simulated under abiotic stress and different photoperiods. The aim of this study was to develop a crop simulation model for bambara groundnut to predict growth, development and yield under drought, heat and cold stress and different daylengths. The present model (BAMGRO) is an adaptation of the established CROPGRO and previous bambara groundnut models; BAMnut and BAMFOOD project model. It uses climate data, landrace specific parameters and soil characteristics and runs on a daily time-step to determine the canopy development, biomass production and yield of a landrace in a specific environment. The parameters of the model have been determined with glasshouses data (TCRU, University of Nottingham) and published information. BAMGRO is capable of describing differences between landraces, and the influence of drought, temperature and photoperiod using a simplified approach. The present modelling approaches with BAMGRO model provide useful predictive information on canopy development, biomass production and yield formation of bambara groundnut landraces under contrasting environments. Two contrasting landraces; Uniswa Red (Swaziland) and S19-3 (Namibia) were used in the present study to evaluate the growth and yield performances under drought, heat and cold stress. BAMGRO has been primarily validated against independent data sets of two years glasshouse for two contrasting landraces; Uniswa Red and S19-3 grown under two temperatures (23 ± 5 0C, 33 ± 5 0C) with drought. Further, it was validated for field data in Botswana with two sowing dates (January 18, February 1) during the 2007 season and for Swaziland for three landraces; Uniswa Red, DipC, OM1. The model achieves a good fit between observed and predicted data for LAI (Nash and Sutcliffe (N-S), 0.78-0.98; Mean Absolute Error, ± 0.14-0.57) for tested four landraces. Pod yield simulation was correlated well with measured values especially for Uniswa Red and S19-3 (N-S 0.73-0.87; Mean Absolute Error ± 16 g m-2) while it was poor for DipC and OM1 (N-S, 0.46-0.50; Mean Absolute Error, ± 15.6-17.7 g m-2). Further, the comparison of simulated and measured data of TDM reported lower correlation compared to LAI and yield. (N-S, 0.59-0.79; Mean Absolute Error ± 48-100 g m-2) indicating overall underestimation. The performance of the BAMGRO-soil water module was tested by validating the available soil moisture and results indicating that it over estimated for upper layers while deeper layers showed lower prediction. The possible reasons for the discrepancies in measured and simulated data are differences in quality and quantity of solar radiation in UK summer and Semi-arid Africa, intra-landrace variability and poor calibration of soil water module. Four potential applications of BAMGRO and three future developments are presented in this thesis.

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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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Moody, Steven James. « MAP kinase activity in the wound response of tomato ». Thesis, University of York, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.325646.

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Doroodian, Paymon. « Overexpression of Differentiation and Greening-Like Alters Stress Response of Arabidopsis thaliana ». Ohio University / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1596227767908937.

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Dong, Shaowei. « Expression of duplicated genes in a polyploid plant in response to abiotic stress ». Thesis, University of British Columbia, 2009. http://hdl.handle.net/2429/13465.

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Polyploidy, or genome doubling, is an important process in plant evolution that has effects on phenotypes, such as changes in flowering time. Allopolyploidy can result in considerable genetic changes including alterations to genome structure, DNA methylation patterns, and gene expression. Although the expression of duplicated genes in polyploid plants has been extensively studied, little is known about the effects of abiotic stress conditions on homeologous gene expression. In this thesis, I examined the expression of 30 homeologous gene pairs in response to five abiotic stress treatments, using a single strand conformation polymorphism (SSCP) assay in allotetraploid Gossypium hirsutum. Twenty-two genes showed stress-induced changes in the expression ratio of the two homeologs, and eight genes showed reciprocal expression changes in response to different abiotic stress treatments, suggesting quantitative subfunctionalization. I also examined the expression of ten homeologous gene pairs in response to three abiotic stress treatments in a synthetic Gossypium allotetraploid. Eight genes showed stress-induced expression changes. Comparison of the expression changes showed that there was little correspondence in the stress-induced homeolog expression patterns between the natural and synthetic Gossypium polyploids. The results of this study indicate that abiotic stress conditions can have considerable effects on expression of homeologous genes. Some of those expression changes might help plants survive abiotic stresses.

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Rouse, Joshua Hatley. « Measurements of plant stress in response to CO2 using a three-CCD imager ». Thesis, Montana State University, 2008. http://etd.lib.montana.edu/etd/2008/rouse/RouseJ1208.pdf.

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Njaci, Isaac. « The role of MicroRNAs in stress response in the resurrection plant Tripogon loliiformis ». Thesis, Queensland University of Technology, 2016. https://eprints.qut.edu.au/93740/1/Isaac_Njaci_Thesis.pdf.

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Research in this thesis focussed on the improvement of agricultural crops in increasing water use efficiency that impacts global crop productivity. The study identified key genetic regulatory mechanisms that the resurrection plant Tripogon loliiformis utilises to tolerate desiccation. Due to the conserved nature of the pathways involved, this information can be transferred for the enhancement of drought tolerance and water use efficiency in agricultural crops. Specifically this study used high throughput sequencing, microscopy and plant transformation to further the understanding of post-transcriptional regulatory mechanisms. It was shown that T. loliiformis uses microRNAs to regulate pro-survival autophagy pathways to tolerate desiccation.

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Curtis, Steven. « The Development of the Stress-Response Scale for Adolescents ». DigitalCommons@USU, 1989. https://digitalcommons.usu.edu/etd/5990.

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Adolescence is an important period in the life cycle for which to study stress, due to the many involved developmental changes that require adaptation. This adaptation can be very stressful and result in pathology. Stress is defined as a "process" involving a continual transaction between stressors in the environment, mediating variables, and stress responses. The Stress-Response Scale for Adolescents (SRSA) was developed to measure self-perceived stress responses of those between the ages of 14 to 20. The SRSA's development involved three studies. Study 1 involved item selection, scale construction, item reduction, and estimations of internal consistency and validity. Truthfulness items were developed to determine the honesty of responses. Study 2 tested the ability of the SRSA, through roe-enactment methodology, to distinguish those in a high-stress condition versus those in a low-stress condition. Study 3, again with the use of role-enactment methodology, tested the potential of the SRSA to detect changes in stress-response levels when individuals were taken from a low-stress to a high-stress condition and vice versa. The final SRSA includes 32 stress-response and six truthfulness items. Initially, factor analysis of the SRSA revealed a high loading of gender on the primary factor. Separate forms were created for males and females. Repeat factor analyses of items in the two forms revealed four factors each for males and females but were of questionable utility due to high intercorrelations. All sections of the SRSA should be used for most purposes. Internal consistency estimates of the SRSA are .96 (2 < .05) for females and .94 (2 < .05) for males. Validity estimates are all in the expected direction and range from .25 to .79 for both males and females. The truthfulness items have a coefficient alpha of .82 for females and .77 for males, with validity estimates ranging from .34 for females to .14 (25 < .05) for males. Studies 2 and 3 revealed that the SRSA does have the potential of differentiating between those in different stress conditions and also of detecting stress-response changes. It was concluded that the SRSA, although in preliminary form, has the potential of assessing the stress response in adolescents as long as the discussed weaknesses, such as small sample size and nonrandomization, are taken into account.

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Khan, Masud Ahmad. « The Effects of Calcium on the Response of Snapbean to Sodium-Induced Stress ». DigitalCommons@USU, 1991. https://digitalcommons.usu.edu/etd/3486.

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Soil salinity is a major concern to agriculture in arid and semiarid regions, where evapotranspiration causes salts originating from irrigation water (or sometimes naturally from the soil) to become concentrated in the rooting zone. In some areas, with good management, it has been economically feasible to ameliorate a sodic soil with Ca. The objective of this study was to investigate the effects of Ca amelioration of salinity (sodicity) on biomass, number of nodules, number of pods, weight of pods, ion uptake, and photosynthesis of Phaseolus vulgaris L. Pl ants were grown in one liter styrofoam pots under greenhouse conditions. In the first experiment, Na stress was accomplished by adding NaCl and Na2S04 at concentrations of 0, 20, 40, 60 , and 80 mmolcfl. The second and third experiments used concentrations of 0, 15, 30, 45, and 60 mmolc/1 NaCl or Na2S04 , combined with two levels of 15 and 30 rnrnolc/1 of either caso4 or cac12. Each styrofoam pot was irrigated with 300 ml of salt solution with a 0.25 leaching fraction on every fourth day for four weeks. Increasing Na concentration decreased biomass, number of nodules, number of pods, and weight of pods but increased ion uptake. Addition of NaCl in the substrate increased shoot Na, Ca, and Cl content, while Na2SO4 increased shoot S content. The photosynthesis rate was affected by all levels and types of sodium salts. Calcium sulfate treatments had a greater ameliorating effect than CaCL2 on Na induced salinity in snapbeans.

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Martinho, Cláudia Sofia dos Santos. « Regulation of gene expression by SnRK1 kinases and miRNAs during the plant stress response ». Doctoral thesis, Universidade Nova de Lisboa. Instituto de Tecnologia Química e Biológica, 2013. http://hdl.handle.net/10362/12032.

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Dissertation presented to obtain the Ph.D degree in Plant Physiology
Plants are constantly challenged by unfavorable conditions like water scarcity, extreme temperatures and salinity that constrain their growth. One of the established consequences of such environmental stress is a decrease in cellular energy levels. This energy deficit activates the SnRK1 (Snf1-Related protein Kinase1) kinase, which thereby triggers a major transcriptional reprogramming aimed at restoring homeostasis. Plants deficient in the SnRK1 pathway are more susceptible to stress, highlighting the importance of this kinase for acclimation and survival.(...)

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Song, Yang. « Analysis of heat stress on pollen development in Arabidopsis thaliana ». Thesis, University of Nottingham, 2017. http://eprints.nottingham.ac.uk/39826/.

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High temperature can have a serious impact on plant development; rising temperatures and environmental fluctuations mean that this is becoming an increasing problem for sustainable agriculture. Many studies have indicated that pollen development is very susceptible to high temperature (HT) stress, particularly during early development, and that the anther tapetum cell layer is extremely vulnerable, resulting in reduced fertility or complete male sterility (MS). In this project, Arabidopsis plants were stressed with 32°C HT during flowering and then assessed by microscopy for phenotypic changes to anther and pollen development, and subsequent reproductive development. The results indicate that the HT had a significant negative impact on plant reproduction, particularly during the stress treatment, with some recovery of fertility post HT. Samples of plant buds were divided into different growth stages and collected for analysis of fertility and for gene expression analysis. Several genes, which appear from available microarray data to be associated with HT stress and are also specifically expressed during tapetum development, were chosen to test for expression changes associated with temperature stress, both during and after HT stress. Phenotype analysis of insertional knockout mutants of these genes, both with and without HT stress, was used to assess their potential impact on resilience to temperature stress. Transcriptomic analysis of whole genome was conducted by RNA-seq in young (prior to polarized microspore stage) and old buds (from polarized microspore stage to pollen mitosis) isolated from HT-stressed and non-stressed Arabidopsis Ler plants. This has identified a set of HT specific genes that are differentially expressed in different HT period treated plants. The anther tapetum serves to regulate pollen development and is critical in the production of the pollen wall. It goes through a defined process of programmed cell death (PCD) to facilitate transfer of pollen wall materials onto the developing pollen grains. Disturbance of the timing or progression of this PCD process, for example by heat stress frequently results in male sterility. Four GFP reporter constructs that have been used as markers during ovule PCD analysis were tested for expression during pollen development and particularly focusing upon the stages of tapetal PCD. These reporter genes showed different stage specific expression during anther development. They have now been introgressed into a number of Arabidopsis male sterile mutants that show PCD-related defects, including ms1, ams and myb26 male sterile mutants. The F1 generation of these showed similar GFP expression to the parent plants, however the homozygous male sterile F2 generation plants appeared to show different patterns of GFP expression. Two of them (BFN1 and CEP1) are expressed in the anther tapetum during the stages of tapetum PCD. Expression analysis suggests that HT-stress affects the expression of BFN1 and CEP1, which may be linked to abnormal degeneration of the tapetum under HT-stress.

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Aghdaei, Seyed Reza Tabaei. « Studies of stress responses in Gramineae (Poaceae) using biotechnological methods ». Thesis, University of Newcastle Upon Tyne, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.336753.

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Robertson, Marta. « Epigenetic Response to Challenging Environmental Conditions ». Scholar Commons, 2017. http://scholarcommons.usf.edu/etd/6939.

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The discovery of epigenetic mechanisms has ignited speculation into their role in ecological and evolutionary processes. In particular, the contribution of epigenetic variation to adaptation or phenotypic plasticity that is distinct from genetic variation would be an important addition to existing evolutionary mechanisms. Although the research of epigenetic mechanisms from an ecological and evolutionary (or eco-evolutionary) perspective has been growing, it is still unclear how epigenetic variation might function in natural populations and settings and to what extent it might serve to mediate population response to changing environmental conditions over time. Over the course of my dissertation, I explored the importance of DNA methylation in population response to a variety of environmental conditions. In the first chapter of my dissertation, I reviewed existing literature on the relationship between DNA methylation and environmental response. I argued that given the weight of current evidence, DNA methylation, in addition to other epigenetic mechanisms, needs to be included the evolutionary synthesis. Additionally, I identified a number of outstanding questions and outlined research directions that would help elucidate the role of epigenetic mechanisms in evolution. In my second chapter, I studied the genetic and epigenetic composition of populations of Spartina alterniflora that were impacted by the Deepwater Horizon oil spill in 2010. Current evolutionary theory predicts that following a severe environmental stressor, populations may experience a bottleneck effect, in which one or only a few genotypes survive to reproduce in subsequent generations. However, it is unclear whether these patterns are reflected in epigenetic variation as well, because novel environmental perturbations may serve to induce epigenetic variation rather than diminish it. We found a significant genetic signature of oil exposure in exposed populations, but did not see a similar effect in the epigenetic composition of exposed populations. These data suggest that epigenetic modifications, such as DNA methylation, may not always increase in number during stressful episodes, but may instead follow genetic variation. These results provide valuable information for the development of nascent population epigenetic theory, and may help parameterize expectations about conditions that provoke epigenetic variation, particularly when genetic variation may be limited. In addition to strong, unpredictable stressors, populations also respond via phenotypic changes over time through developmental stages and life histories that coincide with seasonal, regular environmental cues. Epigenetic mechanisms influence these regulatory and developmental changes that occur within an individual over time. In my third chapter, I examined the epigenetic response to seasonality in multiple coastal plant species. We found a weak signature of single methylation polymorphisms that was associated with seasonal environmental change within the studied species, as well as global patterns of methylation that were consistent across species. The results of this study indicate the possibility of conservation of methylation patterns across phylogenetic histories. In my fourth chapter, I explored in detail how the ability to maintain methylation might affect stress response. We compared individuals of the model plant Arabidopsis thaliana that were deficient in maintenance methylation machinery to control genotypes under both abiotic and biotic stresses, and then studied the growth of their offspring in the absence of stress. We found inherited phenotypic signatures of parental stress in the offspring generation and interactive effects of parental stress and genotype. This study not only reinforces the correlations that we observed in our field studies, but adds to the growing body of literature highlighting the importance of DNA methylation both in immediate environmental response and as a mechanism for heritability. Overall, this dissertation demonstrates that DNA methylation is highly abundant in natural populations and may be part of the response to various stressors at a number of time scales. The integration of DNA methylation in the evolutionary synthesis will aid in the explanation of phenomena such as phenotypic plasticity or adaptation, and will be an important contribution to the existing body of evolutionary mechanisms.

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Tao, Kin-pong, et 涂健邦. « Tspyl2 is involved in cellular stress response and neuronal development ». Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2010. http://hub.hku.hk/bib/B44531527.

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Choudhury, Feroza Kaneez. « Rapid Metabolic Response of Plants Exposed to Light Stress ». Thesis, University of North Texas, 2018. https://digital.library.unt.edu/ark:/67531/metadc1157543/.

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Environmental stress conditions can drastically affect plant growth and productivity. In contrast to soil moisture or salinity that can gradually change over a period of days or weeks, changes in light intensity or temperature can occur very rapidly, sometimes over the course of minutes or seconds. So, in our study we have taken an metabolomics approach to identify the rapid response of plants to light stress. In the first part we have focused on the ultrafast (0-90 sec) metabolic response of local tissues to light stress and in the second part we analyzed the metabolic response associated with rapid systemic signaling (0-12 min). Analysis of the rapid response of Arabidopsis to light stress has revealed 111 metabolites that significantly alter in their level during the first 90 sec of light stress exposure. We further show that the levels of free and total glutathione accumulate rapidly during light stress in Arabidopsis and that the accumulation of total glutathione during light stress is dependent on an increase in nitric oxide (NO) levels. We further suggest that the increase in precursors for glutathione biosynthesis could be linked to alterations in photorespiration, and that phosphoenolpyruvate could represent a major energy and carbon source for rapid metabolic responses. Taken together, our analysis could be used as an initial road map for the identification of different pathways that could be used to augment the rapid response of plants to abiotic stress. In addition, it highlights the important role of glutathione in initial stage of light stress response. Light-induced rapid systemic signaling and systemic acquired acclimation (SAA) are thought to play an important role in the response of plants to different abiotic stresses. Although molecular and metabolic responses to light stress have been extensively studied in local leaves, and to a lesser degree in systemic leaves, very little is known about the metabolic responses that occur in the different tissues that connect the local to the systemic leaves. These could be important in defining the specificity of the systemic response as well as in supporting the propagation of different systemic signals, such as the reactive oxygen species (ROS) wave. Here we report that local application of light stress to one rosette leaf resulted in a metabolic response that encompassed local, systemic and transport tissues (tissues that connect the local and systemic tissues), demonstrating a high degree of physical and metabolic continuity between different tissues throughout the plant. We further show that the response of many of the systemically altered metabolites could be associated with the function of the ROS wave, and that the level of eight different metabolites is altered in a similar way in all tissues tested (local, systemic, and transport tissues). These compounds could define a core metabolic signature for light stress that propagates from the local to the systemic leaves. Taken together, our findings suggest that metabolic changes occurring in cells that connect the local and systemic tissues could play an important role in mediating rapid systemic signaling and systemic acquired acclimation to light stress.

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Kaspar, Kerrie L. « Pigmented potatoes on health : effect on oxidative stress, inflammatory damage and immune response in humans, sensory attributes, and nutrient retention during processing ». Pullman, Wash. : Washington State University, 2009. http://www.dissertations.wsu.edu/Dissertations/Spring2009/K_Kaspar_040809.pdf.

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Gouws, Liezel Michelle, et Jens Kossmann. « The molecular analysis of the effects of lumichrome as a plant growth promoting substance ». Thesis, Stellenbosch : University Stellenbosch, 2009. http://hdl.handle.net/10019.1/4825.

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PhD
Dissertation presented for the degree of Doctor of Philosophy at Stellenbosch University
Embargo(30)lift date 2009-12-31 plt 2010
ENGLISH ABSTRACT: Through powerful signal molecules, rhizobacteria affect fundamental processes in plants. In recent years, a number of novel rhizobial molecules have been identified that positively affect plant growth and development. Previous studies have shown that Sinorhizobium meliloti, which form symbiotic relationships with leguminous plants, increases CO2 availability by enhancing root respiration in alfalfa. The active compound was identified as lumichrome, a previously unrecognized rhizosphere signal molecule that has been shown to promote plant growth in various studies. Lumichrome is a common breakdown product of riboflavin and produced by both chemical and biological factors. Various studies on lumichrome have proven its growth promoting effect in the interaction with plants. The mechanism through which lumichrome increases plant growth remains to be clarified. This study provides new insight into the molecular effects of the plant growth promoter lumichrome on the root metabolism of plants. The main aim of the work presented in this thesis was to investigate the molecular mechanism of the plant growth promoting substance lumichrome in the roots of the model plants Lotus japonicus and Solanum lycopersicon (tomato). To asses the impact of lumichrome on the root metabolism of Lotus japonicus and tomato and identify key genes involved in the growth stimulation, a comprehensive profile of differentially expressed genes, proteins and metabolites was compiled. As the effects of lumichrome as a plant growth promoter have not previously been tested on Lotus japonicus and tomato, basic growth studies were completed to determine if lumichrome indeed elicits plant growth at nanomolar concentrations, as was proven in numerous previous studies. Both Lotus japonicus and tomato showed significant increases in root biomass when treated with 5 nM of lumichrome. The treatment with lumichrome caused complex changes in gene expression. Generally, transcript profiling showed that the categories that were predominantly affected by lumichrome in both Lotus and tomato, were genes associated with RNA regulation of transcription and signaling, protein synthesis/degradation/modification and stress and defence. Proteomic studies revealed that the majority of the differentially expressed proteins were down-regulated. Lumichrome seems to largely influence proteins involved in protein folding and down-regulate proteins involved in glycolysis. Proteomics studies revealed that GS1 (Lotus) and GAPDH (Lotus and tomato) were present in lower abundance in lumichrome treated roots, therefore targeted analysis utilizing northern blots, western blots and the measurement of enzyme activities were completed to determine and verify their specific role in the lumichrome mediated growth promotion. The results indicated that GAPDH and GS1 seem to be under post-translational modification. The influence of lumichrome on the metabolome of Lotus roots was immense, however minute in tomato roots. The knowledge gained in the parallel analyses of both Lotus japonicus and tomato aided us in finding key genes involved in the growth stimulation. Overall, one of the most significant observations was that for the first time to our knowledge, six genes related to defence and pathogen responses were identified that are concurrently expressed in both Lotus and tomato. Through identifying a small number of genes involved in mediating the growth stimulation, these can be used for their functional analysis in the future, using reverse genetics to provide more insight into the molecular mechanisms that are triggered by lumichrome as a plant growth promoter.
AFRIKAANSE OPSOMMING: Deur kragtige sein-molekules, beïnvloed rhizobakterieë basiese prosesse in plante. In die laaste jare is ŉ aantal nuwe molekules, afkomstig van rhizobakterieë, geidentifiseer wat plantgroei en ontwikkeling positief beïnvloed. Voorafgaande studies het bewys dat Sinorhizobium meliloti, wat simbiotiese verhoudings met peulplante aangaan, die beskikbaarheid van CO2 vermeerder deur wortel respirasie in alfalfa te verhoog. Die aktiewe komponent is as lumikroom geidentifiseer, 'n vroeë onerkenbare risosfeer sein-molekule, wat deur vorige studies bewys is dat dit plantgroei stimuleer. Lumikroom is ŉ algemene afbreekproduk van riboflavin en word geproduseer deur chemiese en biologiese faktore. Verskeie studies op lumikroom het bewys dat dit 'n groei stimuleerende effek het op die groei van plante as dit daarmee in wisselwerking tree. Die meganisme waarmee lumikroom plante groei verhoog, is nog nie opgeklaar nie. Hierdie studie verleen nuwe insigte in die molekulêre effekte van die plantgroei stimuleerende molekuul lumikroom op die wortel metabolisme van plante. Die hoofdoel van die werk wat voorgestel word in hierdie tesis, was om die molekulêre meganisme van die plantgroei stimuleerende stof, genaamd lumikroom, in die wortels van die model plante Lotus japonicus en Solanum lycopersicon (tamatie), te ondersoek. Om die uitwerking van lumikroom op die wortel metabolisme van Lotus japonicus en tamatie te bepaal, asook sleutelgene wat betrokke is by die groei stimulasie te identifiseer, is 'n breedvoerige profiel van differensiële uitgedrukte gene, proteïne en metaboliete saamgestel. Die effekte van lumikroom as 'n plantgroei stimuleerende stof is nog nooit op Lotus japonicus en tamatie getoets nie. Om díe rede is eers basiese plantgroei studies gedoen, om vas te stel of lumikroom inderdaad plantgroei teen nanomolare konsentrasies stimuleer, soos in vele voorafgaande studies bevestig is. Beide Lotus japonicus en tamatie het aansienlike verhogings in wortel biomassa getoon as dit met 5 nM lumikroom behandel is. Die behandeling van plante met lumikroom het komplekse veranderinge in geen-uitdrukking veroorsaak. Oor die algemeen het die transkrip-profiele gewys dat die kategorieë wat die meeste geraak is deur lumikroom behandeling, in beide Lotus en tamatie, gene was wat geassosieer word met RNS regulasie van transkripsie en sein-netwerke, proteïen sintese/degradasie/wysiging en stres en verdedigings prosesse in plante. Proteïen studies het gewys dat daar 'n daling in die meerderheid van die proteïen vlakke was wat differensieël uitgedruk was. Dit blyk dat lumikroom in 'n groot mate proteïene beïnvloed wat betrokke is by proteïen-vouing en veroorsaak dat proteïen vlakke van glikolitiese ensieme daal. Proteïen studies het gewys dat GS1 en GAPDH in laer vlakke teenwoordig was in lumikroom behandelde plante en daarom is 'n meer doelgerigte analiese gedoen deur gebruik te maak van "northern blot", "western blot" en deur die ensiem aktiwiteite te meet om hulle spesifieke rol in die lumikroom bemiddelde groei vas te stel. Die resultate wys daarop dat GAPDH en GS1 mag onder die invloed van na-translasionele verandering wees. Die invloed van lumikroom op die metabolietvlakke was groot in Lotus wortels, maar dit het minder van 'n effek gehad op tamatie wortels. Die kennis wat opgedoen is deur die paralelle analiese van beide Lotus japonicus en tamatie plante help ons om sleutel gene wat betrokke is by groeistimulasie te identifiseer. Een van die betekenisvolste waarnemings van hierdie studie was dat vir die eerste keer, sover ons kennis strek, ses gene wat almal betrekking het tot verdediging en patogene-reaksies, geidentifiseer is wat gelyktydig in beide Lotus en tamatie uitgedruk word. Deur 'n klein aantal gene te identifiseer, wat betrokke is by groeistimulasie, kan die gene in die toekoms vir funksionele analieses gebruik word deur van keerkoppeling-genetika gebruik te maak. Daardeur sal meer insig verkry word in die molekulêre meganisme wat deur lumikroom as 'n plantgroei stof veroorsaak word.

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Schäfer, Heinrich [Verfasser]. « The role of the stringent response and Spx in stress response and thermotolerance development / Heinrich Schäfer ». Hannover : Gottfried Wilhelm Leibniz Universität Hannover, 2019. http://d-nb.info/1204459150/34.

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Jaafar, Hawa Zulkifli. « Impact of environmental stress on reproductive development in sweet pepper (Capsicum annuum L.) ». Thesis, University of Nottingham, 1995. http://eprints.nottingham.ac.uk/11690/.

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This investigation was aimed at determining the impact of environmental stresses such as high temperature, low irradiance and drought on reproductive development in sweet pepper, particularly var. Blue Star. Special attention was given to abscission of the primary and secondary flowers. The role of assimilate accumulation and partitioning and the endogenous growth regulator ethylene in mediating stress effects on flower abscission were investigated. The hypothesis that flower abscission is promoted by these stress factors and that abscission is mediated by increased ethylene production and reduced assimilate partitioning to the flowers was tested. Imposition of a mean daily temperature (26 °C) from the third true leaf stage accelerated the development of the first primary flowers to anthesis when combined with high irradiance (4.9 MJ m-² d-¹). However, abscission was increased by 17 % as compared to lower temperature treatments at the same irradiance. The combination of high temperature and low irradiance (2.4 MJ m-² d-¹) induced complete abscission of the primary flowers. Although flower abscission was reduced at the lowest temperature examined (14 °C), development of the primary flowers to anthesis was slower than at higher temperatures. Both varieties, Blue Star and Bell Boy, were able to grow over a wide range of temperatures, as indicated by the large difference (c. 35 °C) between the base and maximum temperatures for growth indicated by a germination trial. In Blue Star, the base (Tb), optimum (To) and maximum (Tm) temperatures were 6.0, 27.5 and 41.5 °C respectively, whereas in Bell Boy, the corresponding values were 8.5, 23.0 and 44.0 °C. Severe water stress imposed progressively after the appearance of the first flower bud promoted the initial development of the primary, but not the secondary flowers to anthesis, but induced early and increased abscission of both primary and secondary flowers shortly afterwards. The high percentage abscission of the primary flowers was partially offset by the lower abscission of secondary flowers. Percentage abscission increased as the severity and duration of water stress increased. However, short exposures to stress did not reduce abscission, or advance anthesis. A more advanced stage of flower development (4.0 mm diameter) proved more susceptible to early abscission than younger flower buds (1.0 mm) when exposed to severe stress. Temporary osmotic adjustment occurred soon after the imposition of water stress, during which osmotic potential decreased sharply from -1.15 to -1.80 MPa, and noticeable reductions in turgor were observed in all treatments between 11 - 22 d after the imposition of stress. Although water stress reduced vegetative growth under low irradiance, complete flower abscission occurred after anthesis. The advancement of anthesis in stressed plants was associated with a decrease in dry matter accumulation in the leaves and stems. However, at the onset of flower abscission, assimilate accumulation and partitioning were not significantly affected by water stress, and flower abscission was not directly related to any reduction in assimilate production or its distribution within the shoot. Instead, prior to flower abscission in severely stressed plants, ethylene evolution in the flowers increased by 8-fold as compared to unstressed plants, and by 40-fold relative to severely stressed plants measured just before anthesis. The application of the ethylene releasing substance, 2 chloroethylphosphonic acid (CEPA), mimicked the effects of severe water stress, as reflected by a surge in ethylene evolution prior to abscission, followed by increased bud abscission. Sweet pepper flowers were also capable of forming abscission zones at the base of their pedicels in response to elevated ethylene production, whilst mature leaves were apparently incapable of this response. Foliar application of silver thiosulphate (STS) to water stressed plants and STS pre-treatment of plants subsequently sprayed with CEPA blocked the action of elevated ethylene resulting from severe stress or CEPA application in inducing flower abscission.

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Audley, Matthew David. « Understanding the role of gibberellin signalling in wheat anther development during heat stress ». Thesis, University of Nottingham, 2017. http://eprints.nottingham.ac.uk/39335/.

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High temperature (HT) stress during wheat male reproductive development causes irreversible damage to the anther tapetum layer and the developing microspores it supports, resulting in reduced yield. With the frequency of pre-flowing temperature stress events likely to increase, a better understanding of the effects of high temperature stress on anther developmental regulation is required. Gibberellin (GA) signalling has been shown to regulate tapetum programmed cell death (PCD) and pollen coat formation via the transcription factor (TF) GAMYB. This project aimed to investigate the function of two putative GA-signalling components in wheat anther development and characterise the global hormonal and transcriptional anther responses to HT. RNAi and TILLInG mutants for TaGAMYB and a putative orthologue of a rice tapetum PCD component, TabHLH141, revealed that both are required for male fertility. Tagamyb mutants displayed stunted anther development with irregular tapetum vacuolisation and reduced pollen viability. An interaction between RHT-D1 and TabHLH141 suggests that GA may mediate anther development through regulation of DELLA-TF interactions. Having characterised and developed a non-destructive staging method for wheat anther development, RNA-Seq and global hormone analysis was used to investigate the response to HT stress around pollen mother cell meiosis. Significant changes in expression of tapetum metabolism and PCD annotated transcripts and anther GA, auxin and jasmonate concentrations indicates that hormonal regulation of HT-responsive transcription may contribute to defective anther development. The work in this project demonstrates that advanced functional genomics techniques can be now be applied to the dissection of complex signalling pathways in hexaploid wheat.

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Liang, Mingxiang. « Physiological and Molecular Function of HAP3b in Flowering Time Regulation and Cold Stress Response ». DigitalCommons@USU, 2010. https://digitalcommons.usu.edu/etd/575.

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Heme-activated proteins (HAPs) are transcription factors that have multiple roles in plant growth and development, such as embryogenesis, flowering time control, and drought tolerance. In the present study I found that HAP3b was also involved in controlling response to cold stress. Transcript profiling and gene expression analyses indicated that HAP3b repressed the CBF3 regulon under normal growth conditions. As a result, plants with HAP3b-overexpressed showed decreased survival rates while plants homozygous for the null allele hap3b showed an improved freezing tolerance compared to wild-type plants. To understand the mechanism of HAP3b in Arabidopsis, i.e. whether it also acts through forming a heterotrimer, the yeast two-hybrid system and the protein coimmunoprecipitation method were used to identify the proteins that could interact with HAP3b. From yeast two-hybrid analyses, it was found that HAP3b could interact with one (At3g14020) of ten HAP2s and all ten HAP5s tested. Further analyses showed that the newly identified HAP2 protein could only interact with two HAP5 proteins, those encoded by At5g63470 and At1g56170. To address whether HAPs also play important roles in major crop plants, HAP3 genes in barley (Hordeum vulgare L.) were identified and characterized. From database sequence analyses, cloning, and sequencing, it was found that barley plants have at least six full-length members in the HAP3 family. Phylogenetic analyses showed that each barley HAP3 was different, forming its own cluster with the HAP3s from other plant species. Each barley HAP3 also showed its own expression pattern in different tissues, at different developmental stages and under various environmental stresses. In particular, TC176294 showed the highest sequence similarity to HAP3b in Arabidopsis and its high expression was associated with flowering. In addition, TC176294 was upregulated by various abiotic stresses and by abscisic acid (ABA). Thus, TC176294 might be a barley ortholog of HAP3b. TC191694 showed the highest sequence similarity to HAP3c and might be a barley ortholog of HAP3c. TC191694 overexpression plants were early flowering compared to HAP3b-overexpression and wild-type plants while overexpression of TC176294 plants were not.

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Sanford, Sarah Grace. « Heterogeneous Stress Response in a Clonal Invader (Imperata cylindrica) : Implications for Management ». Scholar Commons, 2011. http://scholarcommons.usf.edu/etd/3330.

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Life history traits such as growth, survival, and clonality can vary within a population. When such variation exists in a population of an invasive species, it can affect population dynamics, and if any part of the variation has a genetic basis the population can evolve in response to control regimes. Evolutionary responses to control efforts may shift the population towards a few more resilient genotypes, or towards different types in different microenvironments, depending on the scale of gene flow with respect to the patchiness of the environment. The purpose of this study is to examine whether the application of stress similar to control efforts (light level manipulation and biomass removal) results in varying emergence, growth, and survival rates between samples taken from spatially separated patches of the invasive clonal grass Imperata cylindrica. Accelerated Failure Time (AFT) and logistic regression models were fit to survival, emergence and growth data collected from two experiments in which samples collected from four spatially separated Imperata cylindrica patches were exposed to light level manipulation and biomass removal. Patch identity plays a large role in explaining variation in time-to-emergence, time-to-death, and probabilities of emergence and survival, especially under stressed conditions. Rhizome and above ground biomass characteristics also play substantial roles in explaining variation in emergence, survival, and growth, though more so under non-stressed conditions. Our results warrant further study of heterogeneous responses to stressful conditions, especially those imposed under control and management regimes. This heterogeneity may have important impacts on population processes such as maintenance, expansion, and gene flow.

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CARAMANICO, LEILA. « STUDY OF GRAPEVINE ROOTSTOCK RESPONSE TO WATER STRESS ». Doctoral thesis, Università degli Studi di Milano, 2020. http://hdl.handle.net/2434/707586.

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More than 80% of vineyards around the world use grafted plants: a scion of Vitis vinifera grafted onto a rootstock of single or interspecific hybrids of American Vitis species, resistant or partially resistant to Phylloxera (Daktulosphaira vitifoliae (Fitch, 1856)). The genetic variability of grapevine rootstocks plays a fundamental role in their adaptation to the environment (Serra et al., 2013). In the climate change scenario, predicting an increase of aridity in the near future (Dai, 2013), the more frequent and severe drought events may represent the major constrain for the future of viticulture (IPCC, 2018; Schultz, 2000). Therefore, the selection of new rootstocks able to cope with unfavourable environmental condition is a key asset, as well as a strategy to improve crop yield/vegetative growth balance on scion behaviour (Corso and Bonghi, 2014). So far, the influence of rootstock on scion physiological performance during water stress has always aroused great interest. On the contrary, the scion impact on rootstock response is still less debated. Therefore, the effect of grafting on rootstock behaviour have been investigated. Phenotypical and large-scale whole transcriptome analyses on two genotypes, a drought-susceptible (101-14) and a drought-tolerant (1103 P), own-rooted and grafted with Cabernet Sauvignon, subjected to a gradual water shortage in semi-controlled environmental conditions have been performed. The ungrafted condition affected photosynthesis and transpiration, meaning the decisive role of scion in modulation of gas exchanges and in general in plant adaptation. Molecular evidence highlighted that the scion delays the stimulus perception and rootstock reactivity to drought. Since 1985, the DiSAA research group operating at the University of Milan is carrying on a rootstock crossbreeding program which has led to the release of four genotypes: M1, M2, M3 and M4. They show from moderate to high tolerance to drought (M4 > M1 = M3 > M2). In order to characterize their performance during water stress, their physiological (gas exchanges and stem water potential) and transcriptome response (genes involved in ABA-synthesis and ABA-mediated responses to drought) under well-watered and water stress conditions were examined. The behaviour of M-rootstocks (M1, M2 and M3) was compared with that of other commercial genotypes largely used in viticulture, either tolerant (140 Ru, 41 B, 110 R, 1103 P), less tolerant (SO 4, K 5BB) and susceptible (420 A and Schwarzman). Discriminant analysis (DA) showed that when water availability starts to decrease, rootstocks firstly perceives the stress activating a transcriptome response, consequently physiological changes have been observed. It also demonstrated that the three M-rootstocks were clearly discriminated: M4 was grouped with the most tolerant genotypes while M3 with the less tolerant or susceptible ones from a physiological standpoint, confirming their different attitude to tolerate water stress. M4 has proven to be a promising rootstock due to its ability to adapt to drought conditions. Considering the constant great demand for vine planting materials, the obtainment of genetically homogeneous populations (i.e. clones) from elite individuals through micropropagation represents a rapid alternative to conventional multiplication. For this reason, an efficient high-throughput protocol for M4 in vitro propagation was set up. Its attitude to shooting, root development and callus proliferation was compared to that of other rootstocks largely used in viticulture (K5BB, 1103P, 101-14 and 3309C). Moreover, pro-embryogenic and embryogenic callus from bud explants were also produced, representing a cellular material manipulable with the genetic engineering techniques. In water scarcity condition, among the mechanisms activated by M4, the great ability to scavenge ROS, related to the increased accumulation of stilbenes and flavonoids, may be such as to give it tolerance to the stress. In particular, the higher levels of trans-resveratrol were correlated with the up-regulation of some stilbene synthase genes, mainly VvSTS16, VvSTS18, VvSTS27 and VvSTS29. The over expression of these genes was linked to a structural variation in their promoter region. To confirm that VvSTSs genes may be considered putative factors of M4 better adaptation to water stress, a genome editing protocol based on the CRISPR/Cas9 system, aimed at knock-out the genes, was performed. For testing the gRNAs functionality, a transient assay on in vitro micropropagated plantlets of M4 and 101-14 was performed. The positive results obtained by this experiment will lead to the transformation of somatic embryos and regeneration of whole-edited plants using the vectors developed.

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Kornfeld, Ari. « The Role of Alternative Oxidase (AOX) in Plant Stress : do Plants Increase the Activity of AOX in Response to Nutrient Stress Under Field Conditions ? » Thesis, University of Canterbury. School of Biological Sciences, 2012. http://hdl.handle.net/10092/7009.

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RATIONALE: Recent studies indicate that plants can partition electron transport through alternative oxidase (AOX) and cytochrome c oxidase (COX) in response to environmental cues, thus modulating respiratory efficiency. The ¹⁸O discrimination method necessary for measuring electron partitioning in vivo, however, has been restricted to laboratory settings due to equipment constraints. Since plants grown in more natural and variable environments may not respond as predicted by laboratory experiments, I developed a new field-compatible analytical method and then applied it to three ecophysiological studies. METHODS: To address these needs, I developed a field-compatible method in which plant tissue was incubated in 12 mL septum-capped vials for 0.5 – 3 h, after which the incubation air was transferred to 3.7 mL storage vials for subsequent measurement by mass spectrometry. I also developed mathematical tools to correct for unavoidable contamination, and to detect and address curvature in the data – whether intrinsic to the respiration or due to contamination, – and to extend the usable dynamic range of the mass spectrometer. These methods were used to investigate respiratory responses (1) in canopy trees growing across a soil nutrient gradient at the Franz Josef chronosequence, New Zealand; (2) in a nutrient manipulation experiment of Griselinea littoralis; and (3) in a long-term nutrient-, temperature-, and light manipulation at Toolik, Alaska, USA. Leaf dry matter content, specific leaf area, nitrogen (N), phosphorus (P), sugars, starch, and AOX/COX protein concentrations were also measured as explanatory variables. (Leaf Cu and Fe were measured at the Franz Josef chronosequence.) RESULTS: Discrimination values computed using my methods replicated previously reported results over a range of 10 – 31‰, with precision generally better than ±0.5‰, thus demonstrating its validity as tool for measuring respiratory electron partitioning. Foliar respiration declined with site age across the soil chronosequence, increasing with leaf N levels, r² = 0.8, but electron partitioning declined with increasing N/P, r² = 0.23. AP activity was positively correlated with leaf P, Cu, and starch, r² = 0.71. In younger soils, however, declines in respiration were attributed to declines in cytochrome pathway (CP) activity, whereas across the older sites respiration declined due to a reduction in AOX pathway (AP) activity. The Griselinia nutrient-manipulation experiment partially confirmed these results: AOX protein levels were highest in N-deficient plants rather than in plants deficient in both N and P. AP activity was very low in all leaves, however, possibly due to low illumination. In support of this claim, leaves that had developed in the sun had higher AOX/COX protein ratios than those that had developed in the greenhouse. In Griselinia roots, CP activity declined by more than half in response to nutrient deficiency, whereas AP activity was unchanged. At the Arctic site, only one species changed electron partitioning in response to nutrient addition. Betula nana, the most successful adapter to improved mineral nutrition, doubled leaf CP activity without changing AP activity. Species grown in full sun at that site also had higher AOX/COX protein ratios than those that grew in enclosures. CONCLUSIONS: This is the first study of how engagement of terminal respiratory oxidases in plants responds to multiple nutrient deficiencies, both in nature and in a controlled environment. I have uncovered some intriguing relationships, including the possible importance of N/P to electron partitioning, as well as a role for Cu. The results also suggest that electron partitioning is sensitive to plant energy balance, as suggested by the low AP activities and low AOX/COX protein ratios in shaded plants. Perhaps most significantly, the AP and CP appeared to act independently of each other, rather than through a concerted “partitioning” process. In addition to their own scientific merit, these results illustrate the value of using the new field-compatible method to conduct ecophysiological investigations of plant respiratory electron partitioning on a much large scale, and under more realistic conditions, than has been previously possible.

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Segu, Rifai. « Demand-Response Management of a District Cooling Plant of a Mixed Use City Development ». Thesis, KTH, Kraft- och värmeteknologi, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-96539.

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Demand for cooling has been increasing around the world for the last couple of decades due to various reasons, and it will continue to increase in the future particularly in developing countries. Traditionally, cooling demand is met by decentralised electrically driven appliances which affect energy, economy and environment as well. District Cooling Plant (DCP) is an innovative alternative means of providing comfort cooling. DCP is becoming an essential infrastructure in modern city development owning to many benefits compared to decentralized cooling technology. Demand Response Management (DRM) is largely applied for Demand Side management of electrical grid. Demand of electrical energy is closely connected with the demand of alternative form of energy such as heating, cooling and mechanical energy. Therefore, application of DR concept should be applied beyond the electrical grid; in particular, it could be applied to any interconnected district energy systems. District Cooling Plant is one of a potential candidate and Demand Response management solutions can be applied to DCP for sustainable operation. The study of demand response and its applicability has not been attempted previously for district cooling systems. To our knowledge, this is the first attempt to evaluate its applicability and economical feasibility. This thesis focused on some of the DR objectives which have the potential to implement for DCP of a mixed-use city. General published data on mixed use city developments and a specific city in Dubai was taken as a case study to show the usefulness on DRM objectives. This study primarily addressed the issues related to load management. The findings are: DRM creates greater flexibility in demand management without compromising service levels. Also it reduces the operation cost and impact to environment. However implementation is a big challenge. Therefore implementation strategies are also proposed as a part of recommendation which includes a generic model for demand response management. Moreover, a review is provided on key enabling technologies that are needed for effective demand response management. Finally this thesis concludes with recommendations for prospective applications and potential future works.

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Thèses sur le sujet « Plant development and stress response »

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