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1
Boland, Holly Terry. "Grazing Behavior of Beef Steers Grazing Endophyte-Infected, Endophyte-Free, and Novel Endophyte Infected Tall Fescue, and Lakota Prairie Grass". Thesis, Virginia Tech, 2005. http://hdl.handle.net/10919/34557.
Testo completoAbstract (sommario):
Endophyte infected Tall fescue (Festuca arundinacea Schreb.) is the most dominant grass used for pasture in the Southeastern U.S. As a result, fescue toxicosis is a major concern. Producers need alternative forages for grazing cattle that do not have this negative aspect. The objective of this experiment was to determine the grazing behavior of cattle grazing Lakota (L) prairie grass (Bromus catharticus Vahl.), endophyte infected (E+), endophyte free (E-), and novel endophyte (Q) tall fescues. Angus-crossbred steers (279±8 kg) steers wore electronic behavior data recorders in four sampling periods, and direct visual appraisals of behavior were taken in five sampling periods during the months of May to September, 2004. Overall, during the visual appraisal phase steers grazing L spent most time (P<0.05) grazing while E+ spent the least time grazing. Overall, steers grazing E+ spent more time (P<0.05) idling than those on L, E-, or Q. Steers grazing E+ spent more time (P<0.05) standing than steers grazing Q. Steers grazing Q and E- spent more time (P<0.05) lying than those grazing E+. During the data recorder phase there were no significant differences between treatments for time spent grazing. Steers grazing E+ spent less time (P<0.05) lying and ruminating than steers grazing Q or L. Conversely, time spent standing and idling for steers grazing E+ was higher (P<0.05) than for steers grazing Q or L. These results indicate that L, E-, and Q may offer benefits to producers due to more time spent in productive activities during summer months.Master of Science
2
Holmes, Amanda Christine. "Host-endophyte interactions in Zantedeschia aethiopica". Thesis, University of the West of England, Bristol, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.389513.
Testo completo
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Reivant, Munters Arielle. "The foliar bacterial endophyte community in native Pinus radiata: a role for protection against fungal disease?" Thesis, Uppsala universitet, Institutionen för biologisk grundutbildning, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-234871.
Testo completoAbstract (sommario):
Pinus radiata is the most planted tree in the southern hemisphere. The planted trees are especially susceptible to pathogens, but even the native population, nowadays limited tomerely five locations, are threatened by diseases caused by arthropods, fungi and dehydration. Endophytes are bacteria or fungi that reside inside healthy plant tissue, and often have a beneficial effect on their hosts. Endophytes can help plants adapt to abiotic stress such as drought and protect them against pathogens and insect pests. Given the roles that endophytes play in host stress responses, it is possible that without studying endophytes we may not fully understand a plant’s response to increased temperatures and climate-induced disease.Using Illumina-sequencing of the 16S rRNA-gene the bacterial endophyte community in 15 trees from three of the remaining native populations were studied. By investigating trees from several sites geographical community differences were discovered. The three overall most dominating bacterial taxa can all be connected with genera known to contain members withanti-fungal properties.
4
Al-Nahidh, S. I. "Host-endophyte compatibility in mycorrhizal crop plants". Thesis, University of Leeds, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.354035.
Testo completo
5
King, Eoghan. "Caractérisation phénotypique et moléculaire de la réponse du riz au cours de l’interaction avec des espèces de Burkholderia s.l". Thesis, Montpellier, 2019. http://www.theses.fr/2019MONTG079.
Testo completoAbstract (sommario):
Dans les conditions naturelles, les plantes interagissent avec une grande diversité de microorganismes, entretenant avec elles des types d’interactions variées allant du mutualisme à la pathogénie. Quelque soit le type d’interaction mis en place, les plantes sont capables de reconnaitre des motifs moléculaires microbiens conservés qui induisent l’activation d’une réponse immunitaire dite « non-hôte ». Cette réponse immunitaire basale a largement été étudiée dans le cas des interactions avec des microorganismes mutualistes et pathogènes. Cependant, dans le cas des « symbioses associatives » avec des rhizobactéries ou des bactéries endophytes bénéfiques, regroupées sous le terme de Plant Growth-Promoting Rhizobacteria (PGPR), les réponses immunitaires et physiologiques des plantes ont très peu été décrites. Dans ce contexte, ce projet de thèse a eu pour objectif de décrire les régulations transcriptionnelles de la monocotylédone modèle, le riz, en réponse à l’interaction avec des bactéries bénéfiques -rhizosphériques ou endophytes- et pathogènes du genre Burkholderia sensu lato (s.l.). Ce genre ubiquiste de béta-protéobactéries a la particularité d'avoir été subdivisé en deux genres aux écologies distinctes : le genre Paraburkholderia regroupant des espèces environnementales et bénéfiques des plantes, et le genre Burkholderia sensu stricto (s.s.) qui regroupe des espèces opportunistes et pathogènes de l'homme ainsi que des pathogènes de plantes, mais aussi des espèces phytobénéfiques (comme B. vietnamiensis). L’analyse par RNA-Seq de la réponse transcriptomique du riz à trois souches endophytes, Paraburkholderia kururiensis M130, Burkholderia vietnamiensis TVV75 et Paraburkholderia phytofirmans PsJN, ont permis de mettre en évidence des régulations physiologiques contrastées en fonction de la souche inoculée. De plus, des analyses comparatives de la colonisation des tissus racinaires par ces souches ont pu associer certaines de ces régulations à différents modes de colonisation. Enfin, l’expression de gènes impliqués dans la réponse immunitaire des plantes, identifiés par l’analyse fonctionnelle des transcriptomes, a été mesurée au cours de cinétiques d’interaction avec une plus large diversité de souches. Pour cela, dix souches de Burkholderia s.l., comprenant trois souches pathogènes, ainsi que trois souches PGPR modèles du riz des genres Azospirillum, Herbaspirillum et Pseudomonas ont été choisies. Cette dernière approche a permis de mettre en évidence des régulations transcriptionnelles associées à des types de colonisation, rhizosphérique et endophytique, ou d’interactions, bénéfiques et délétères. Ces travaux s’intègrent dans la caractérisation des bases moléculaires de la réponse des plantes aux microorganismes bénéfiques qui représentent un potentiel important pour le développement de solutions agronomiques durables favorisant la nutrition et la résistance des plantes aux maladiesIn natural conditions, plants interact with a large diversity of microorganisms maintaining with them various types of interaction ranging from mutualism to pathogenesis. Whatever the type of interaction established, the plants are able to recognize conserved microbial molecular motifs which trigger a so-called “non-host” immune response when perceived. This basal immune response has been extensively studied in the case of interactions with mutualistic and pathogenic microorganisms. However, in the case of “associative symbiosis” with beneficial rhizobacteria or bacterial endophytes, grouped under the term Plant Growth-Promoting Rhizobacteria (PGPR), the immune and physiological responses of plants have been scarcely described. In this context, this thesis project aimed at describing the transcriptional regulations of the model monocotyledonous rice, in response to the interaction with beneficial -rhizospheric or endophytic- and pathogenic bacteria of the genus Burkholderia sensu lato (s.l.). This ubiquitous genus of beta-proteobacteria has the particularity of having been subdivided into two genera with distinct ecologies: the genus Paraburkholderia, which groups together environmental and plant-associated species, and the genus Burkholderia sensu stricto (s.s.), which groups together human opportunistic and pathogenic species but also phytobeneficial species such as B. vietnamiensis. RNA-Seq analysis of the transcriptomic response of rice to three endophytic strains, Paraburkholderia kururiensis M130, Burkholderia vietnamiensis TVV75 and Paraburkholderia phytofirmans PsJN, revealed contrasting physiological regulations depending on the inoculated strain; in addition, comparative analyses of root tissue colonization by these strains enabled to associate some of these regulations with different colonization patterns. Finally, the expression of genes involved in the immune response of plants, identified by the functional analysis of transcriptomes, was measured during interaction kinetics with a wider diversity of strains. For this, ten strains of Burkholderia s.l., comprising three pathogenic strains, as well as three model rice PGPR strains of the genera Azospirillum, Herbaspirillum and Pseudomonas were selected. This last approach highlighted transcriptional regulations associated with the types of colonization, rhizospheric and endophytic, or interaction, beneficial and deleterious.This work is part of the characterization of the molecular bases of plants’ response to beneficial microorganisms which represent an important potential for the development of sustainable agronomic solutions favoring nutrition and plant resistance to diseases
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Barenstrauch, Margot. "Characterization of oxylipin signaling in the chemical interaction between the endophyte Paraconiothyrium variabile and the phytopathogen Fusarium oxysporum". Thesis, Paris, Muséum national d'histoire naturelle, 2018. http://www.theses.fr/2018MNHN0010/document.
Testo completoAbstract (sommario):
Les champignons endophytes sont des microorganismes non-pathogènes impliqués dans des associations mutualistes avec les plantes. Les endophytes foliaires, en particulier, représentent un groupe très divers, mais leurs interactions avec la plante hôte et ses micro-organismes associés sont peu connues. Des travaux préliminaires initiés par notre équipe, explorant la diversité microbienne foliaire du conifère Cephalotaxus harringtonia, ont permis d’isoler la souche fongique Paraconiothyrium variabile (Ascomycota), un antagoniste du phytopathogène Fusarium oxysporum. Au cours de leur interaction, on détecte des quantités moindres de beauvéricine, une mycotoxine synthétisée par F. oxysporum. En parallèle, on observe une augmentation de la synthèse de deux oxylipines, l’acide 13-hydroperoxyoctadécadiénoïque (13-HPODE) et l’acide 13-oxo-octadécadiénoïque (13-oxo-ODE), dans la zone de confrontation. L'objectif de ce travail était de comprendre les mécanismes conduisant à la diminution de la beauvéricine au cours de l'interaction et d'explorer le rôle des oxylipines dans la régulation de cette dernière. Dans mon travail de thèse, je montre la présence de deux gènes lox chez P. variabile (pvlox1 et pvlox2) codant tous deux pour des manganèse lipoxygénases, potentiellement à l'origine des acides 13-HPODE et 13-oxo-ODE. Pvlox2 est spécifiquement induit pendant l'interaction, et ces résultats sont corroborés par une synthèse accrue de 13-HPODE chez P. variabile. Par ailleurs, l'interaction avec l’endophyte, ainsi que l'ajout de l’oxylipine 13-HPODE, régulent positivement la voie de biosynthèse de la beauvéricine, comme l’indiquent les teneurs plus élevées en mycotoxines observées chez F. oxysporum. Enfin, nous avons montré que la beauvéricine inhibait la croissance de l’endophyte, mais que ce dernier était capable de dégrader la mycotoxine, expliquant ainsi les faibles quantités de beauvericine observées initialement dans la zone de compétition. Ce travail contribue à la compréhension du rôle des oxylipines dans la communication inter-microbienneEndophytic fungi are non-pathogenic microorganisms involved in mutualistic associations with their host. Foliar endophytes, in particular, represent a very diverse group but little is known about their interactions with the host and its associated micro-organisms. In preliminary work, exploring the leaf microbial diversity of the conifer Cephalotaxus harringtonia, our team isolated the fungal strain Paraconiothyrium variabile (Ascomycota), an antagonist of the phytopathogen Fusarium oxysporum. During their interaction, decreased amounts of the F. oxysporum mycotoxin beauvericin, and higher amounts of the two oxylipins, 13-hydroperoxyoctadecadienoic acid (13-HPODE) and 13-oxo-octadecadienoic acid (13-oxo-ODE), were observed in the confrontation zone. The objective of the present work was to understand the mechanisms leading to beauvericin decrease during the interaction and to explore the role of oxylipins in beauvericin regulation. In my thesis work I show the presence of two lox genes in P. variabile (pvlox1 and pvlox2) coding both for manganese lipoxygenases, potentially at the origin of 13-HPODE and 13-oxo-ODE. Pvlox2 is specifically induced during the interaction, which lead to an increased synthesis of 13-HPODE in P. variabile. The endophyte itself, as well as the oxylipin 13-HPODE, up-regulated the beauvericin biosynthesis gene beas, which was paralleled by higher mycotoxin content in the mycelium of F. oxysporum. Finally, we showed that beauvericin inhibited the endophyte’s growth, but the latter was capable to degrade the mycotoxin, which explains the lower amounts of beauvericin found in the competition zone. This work presents pioneer undertaking to elucidate the role of oxylipins in inter-microbial crosstalk
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Athman, Shahasi Yusuf. "Host-endophyte-pest interactions of endophytic Fusarium oxysporum antagonistic to Radopholus similis in banana (Musa spp.)". Thesis, Pretoria : [s.n.], 2006. http://upetd.up.ac.za/thesis/available/etd-12072006-105803.
Testo completo
8
Wäli, P. (Piippa). "Environment and genetic background affecting endophyte-grass symbiosis". Doctoral thesis, University of Oulu, 2006. http://urn.fi/urn:isbn:9514281632.
Testo completoAbstract (sommario):
Abstract
Mutualism is often conditional and the associations vary from antagonism to mutualism along environmental conditions and genotypes of interacting species. I studied antagonism-mutualism continuum hypothesis of symbiosis experimentally using two different Epichloë/Neotyphodium endophytes and their host grasses, agricultural meadow fescues and natural fine fescue, as study systems. These systemic fungal endophytes live asymptomatically within aerial tissues of grasses, and are vertically transmitted to the next grass generation via seeds. Thus, asexual endophyte strains are dependent on the growth, survival and reproduction of their hosts. Epichloë/Neotyphodium endophytes are considered plant mutualists, because they improve the resistance of the host against various stresses, e.g. herbivores. In addition to experimental approach, I examined prevalence and genetic structure of Epichloë festucae in natural grass populations. Finally, current knowledge concerning grass endophytes was reviewed and the effects of variable environment and genetic background on the ecology and the evolution of grass-endophyte symbiosis were discussed.
The endophyte improved the performance of the agronomic meadow fescues, but the beneficial effects were dependent on the grass cultivar and the growth environment. The endophyte-infected (E+) meadow fescues were more susceptible to the pathogenic snow molds and they suffered increased winter damage compared to the endophyte-free (E-) plants. Many natural Festuca rubra and F. ovina populations were either endophyte-free or had low infection frequency. The highest infection frequencies were found in subarctic areas where the infection incidence differed between habitats. Twenty out of the 25 E. festucae genotypes detected were carrying multiple alleles in microsatellite loci indicating multiple infections or vegetative hybridization of the fungus. A dominant genotype (63.5% of all isolates) occurred in all populations suggesting that this fungus is mainly asexual. E+ F. ovina seedlings performed worse than endophyte-free E- seedlings. In F. rubra, the river bank originated E+ seedlings allocated fewer, but longer and heavier tillers than the other seedlings indicating possible improved performance of the endophyte infected grasses in harsh river bank conditions.
In short, I detected both positive and negative effects of endophyte infection on grasses varying along species, environment and genotypic background of study subjects. The results support the antagonism-mutualism continuum hypothesis.
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Babu, Jacob. "Bioactive Chemicals of Importance in Endophyte-Infected Grasses". The University of Waikato, 2009. http://hdl.handle.net/10289/2608.
Testo completoAbstract (sommario):
Janthitrems are believed to be involved in the observed sporadic cases of AR37- infected perennial ryegrass staggers. Investigations into the role of janthitrems in perennial ryegrass staggers are difficult as isolation of the compounds from the ryegrass is hindered by the inherent instability of these compounds. Therefore attempts were made to isolate janthitrems from an alternative source, allowing these janthitrem analogues to be used as surrogates for endophyte produced janthitrems. Analysis of a series of Penicillium janthinellum cultures revealed the presence of janthitrems in a number of strains, including janthitrem B, janthitrem C and two novel janthitrem compounds. Detailed one- and two-dimensional NMR and mass spectral techniques identified the two novel compounds as 11,12- epoxyjanthitrems B and C, which were subsequently given the trivial names janthitrems A and D, respectively. Janthitrems B and C were isolated and identified by NMR and revisions of some previously reported chemical shift assignments were proposed. In addition to the janthitrems, penitrems were also identified in two strains of P. janthinellum. The isolated janthitrem B was utilised for the development of efficient extraction procedures, and for the determination of ideal storage conditions for janthitrem compounds. A method for the extraction and isolation of janthitrem B from a P. janthinellum culture was developed and optimised to yield 6 mg of janthitrem B from 900 mL of fungal culture in two days. Stability studies of janthitrem B indicated the ideal storage condition which minimised degradation was dry at −80 C where only 7% sample loss was observed over 300 days. Bioactivity studies of janthitrems A and B found these compounds to be tremorgenic to mice, with janthitrem A (an epoxyjanthitrem) inducing more severe tremors than janthitrem B. Insect testing also showed that both janthitrems A and B displayed anti-insect activity to porina larvae. Since the epoxyjanthitrems, which are associated with AR37 endophyte-infected ryegrass, were also shown to be tremorgenic and to display anti-insect activity, the insect resistance and the sporadic cases of ryegrass staggers displayed by AR37 may be related to the presence of epoxyjanthitrem compounds. LC-UV-MS analysis of janthitrems A-D, penitrems A-F, lolitrem B, paspalinine, paxilline and terpendole C found these indole-diterpenoids to be more sensitive by analysis using an APCI source as opposed to an ESI source. APCI negative ion LC-UV-MS required source induced dissociation in combination with increased collision energy to suppress an acetate adduct peak, sourced from the acetic acid buffer. Negative ion MS2 and MS3 data produced more informative fragments compared to the conventional positive ion MS2 and MS3 data. The availability of both positive and negative ion LC-UV-MS methodologies will allow future endophyte products to be more thoroughly screened for different classes of secondary metabolites. Extracts of mouldy walnuts were analysed for the presence of tremorgenic mycotoxins after a dog was found to exhibit symptoms characteristic of tremorgenic mycotoxicosis. LC-UV-MS analysis of the mouldy walnuts identified the tremorgenic mycotoxins penitrems A-F, thus confirming the veterinarian's tentative diagnosis of canine tremorgenic mycotoxicosis the first reported case in New Zealand.
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Craven, Kelly D. "COEVOLUTION AND GENETIC DIVERSITY IN GRASS-ENDOPHYTE SYMBIOSES". UKnowledge, 2003. http://uknowledge.uky.edu/gradschool_diss/431.
Testo completoAbstract (sommario):
Symbioses between cool-season grasses (Subfamily Pooideae) and endophytic fungi in the genera Epichlo and Neotyphodium straddle a continuum of interactions from antagonistic to highly mutualistic. Although these two genera of endophytes are closely related, Neotyphodium endophytes are strictly seed-transmitted and provide many physiological and defensive benefits to their hosts, while Epichlo spp. have an obligately sexual contagious stage wherein host inflorescences are replaced by fungal sexual structures (stromata), effectively sterilizing the plant. Between these two extremes of interactions are Epichlo spp. with a mixed strategy, where some grass tillers are sterilized while others develop normally and yield healthy endophyte-infected seeds. These symbioses offer a unique opportunity to dissect evolutionary mechanisms that may drive movement along this continuum. The research presented characterizes distinct hybridization processes in endophytes and grasses that result in the generation of astounding genetic diversity for the symbiosis. Interspecific hybridization via hyphal anatomosis is a common feature of Neotyphodium endophytes, and may promote mutualism by combining suites of defensive alkaloid genes and ameliorating the adverse evolutionary effects of an asexual lifestyle. My results demonstrate that several genetically distinct hybrid endophytes infect grass species in tribe Poeae. Further, I show that a highly mutualistic asexual endophyte infecting tall fescue (=Festuca arundinaceum Schreb.), Neotyphodium coenophialum, also infects two closely related and interfertile relatives of this host. My findings suggest that this seed-borne endophyte may have been introgressed into these grasses through sexual grass hybridization events. These findings highlight interspecific hybridization as a means of generating tremendous genetic variability in both endophytes and their hosts, thus magnifying the adaptive evolutionary potential of these symbioses. Further, I establish a phylogenetic framework for grasses naturally harboring Epichlo and Neotyphodium endophytes. I show that patterns of genetic divergence among grass lineages are emulated by those of their fungal symbionts. These results suggest that endophytes have co-evolved with grasses in subfamily Pooideae, and may have played a critical role in the evolutionary success and radiation of this group of grasses.
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Bailes, Graham. "Drivers of endophyte communities in Pacific Northwest prairies". Thesis, University of Oregon, 2017. http://hdl.handle.net/1794/22783.
Testo completoAbstract (sommario):
Prairies of the Pacific Northwest are threatened systems, with only ~2% of historic land remaining. The combined risk of global climate change and land use change make these systems a high conservation priority. However, little attention has been paid to the microbiota. Fungal endophytes are ubiquitous in plants and are important in ecosystem functioning and host dynamics. To understand fungal community assembly, we used high-throughput sequencing to investigate the composition of fungal foliar endophyte communities in two native, cool-season (C3) bunchgrasses along a natural latitudinal gradient. We quantified the importance of host, host traits, climate, edaphic factors, and spatial distance in microbial community composition. We found that spatial distance was the strongest predictors of endophyte community, while host traits (e.g., plant size, density) and abiotic environment were less important for community structure. These findings underline the importance of dispersal in shaping microbial communities.
This thesis includes previously unpublished, co-authored material.
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Barakat, Fatima. "Etude mycochimique et activités leishmanicides de composés issus de Botryosphaeria mamane, un champignon endophyte isolé de Bixa orellana L". Thesis, Toulouse 3, 2018. http://www.theses.fr/2018TOU30227.
Testo completoAbstract (sommario):
Les maladies tropicales négligées, telle que la leishmaniose, constituent un problème majeur de santé publique, en particulier dans les pays à faible revenu où cette maladie sévit. Le nombre limité des médicaments disponibles, leurs coûts, leurs effets indésirables et l’émergence de résistances, exige la recherche de nouveaux agents thérapeutiques. Les champignons endophytes constituent une source prometteuse de nouvelles molécules bioactives. Dans ce contexte, une étude mycochimique a été menée sur une souche endophyte de Botryosphaeria mamane, un micromycète relativement peu étudié, isolée des feuilles de Bixa orellana. Cette souche a été sélectionnée suite à un criblage préliminaire mené contre un modèle d’amastigotes axéniques de Leishmania infantum. Les études chimiques sur ce champignon ont permis d’isoler 9 molécules pures (BM1-BM9), dont 6 de structures nouvelles (BM1-BM4, BM8, BM9) et deux mélanges BM10 et BM11. Les molécules BM1-BM4 appartiennent à la famille des cyclopeptides de type thiodicétopipérazines que nous avons nommés botryosulfuranols A-D. Ils possèdent un squelette original caractérisé par deux centres spirocycliques. BM5-BM7 se sont révélés être des isocoumarines dérivés de la mélleine (cis-4-hydroxymélleine, trans-4-hydroxymélleine et 5-hydroxymélleine). BM8 et BM9 sont deux polycétides de structure nouvelle. Enfin, BM10 et BM11, sont des mélanges de cyclopentapeptides. L’évaluation de leur activité biologique sur amastigotes axéniques de Leishmania infantum a révélé que les thiodicétopipérazines avaient les meilleures activités. Le composé BM4 est le plus actif (CI50 = 0.03 µM) mais également le plus sélectif (IS = 190) de L. infantum par comparaison avec sa cytotoxicité sur des macrophages. BM1 et BM3 sont aussi actifs mais peu sélectifs (CI50 = 0.69 et 0.44 µM, IS = 3 et 15, respectivement) en raison de leur toxicité sur macrophages, et BM2 (CI50 = 3.88 µM) n’a montré aucune sélectivité. Les composés BM8 et BM9, bien que non cytotoxiques sur macrophages, ont montré une activité plus modérée contre L. infantum. Les composés BM5-BM7, et les mélanges BM10, BM11 n’ont présenté aucune activité leishmanicide. L'ensemble de ce travail souligne ainsi l'intérêt des endophytes fongiques comme sources de nouveaux composés leishmanicidesNeglected tropical diseases, such as leishmaniasis, are a major public health problem, especially in the poorest countries of the world. The limited number of drugs available, their costs, adverse effects and the emergence of resistances, require the search for new therapeutic agents. Endophytic fungi are a promising source of new bioactive molecules. In this context, a mycochemical study was carried out on an endophytic strain of Botryosphaeria mamane, a relatively poorly studied micromycete, isolated from Bixa orellana leaves. This strain was selected from a preliminary screening for its good activity against Leishmania infantum axenic amastigotes. Chemical investigations on this fungus led to the isolation of 9 pure molecules (BM1-BM9), 6 of which are new structures (BM1-BM4, and BM8, BM9) and two mixtures BM10 and BM11. BM1-BM4 belong to the family of cyclodipeptides and are thiodiketopiperazines derivatives that we called botryosulfuranols A-D. The latter possess an unprecedent skeleton characterized by two spirocyclic centers. BM5-BM7 are isocoumarins derived from mellein (cis-4-hydroxymellein, trans-4-hydroxymellein and 5-hydroxymellein). BM8 and BM9 are two new polyketides. Finally, BM10 and BM11 are mixtures of cyclopentapeptides. Evaluation of leishmanicidal activities of these 9 compounds and the two mixtures on axenic amastigotes of Leishmania infantum showed that thiodiketopiperazines possessed the highest activities. BM4 was the most active (IC50 = 0.03 μM) and the most selective (IS = 190) when compared to its cytotoxicity on macrophages. The other thiodiketopiperazines BM1 and BM3 were active but less selective (IC50 = 0.69 and 0.44 μM, SI = 3 and 15, respectively), whereas BM2 was moderately active (IC50 = 3.88 μM) and not selective. BM8 and BM9, despite their absence of cytotoxicity against macrophages, were also moderately active against L. infantum (IC50 = 13.35 and 4.53 μM respectively). Compounds BM5-BM7, and the mixtures BM10 and BM11 did not show any leishmanicidal activities. This work highlights the interest of fungal endophytes as sources of new leishmanicidal compounds
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Grünig, Christoph. "Population biology of the tree-root endophyte Phialocephala fortinii /". [Zürich], 2003. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=15313.
Testo completo
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Hunt, Matthew. "Effects of environmental change on endophyte-plant-insect relationships". Thesis, University of Oxford, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.275301.
Testo completo
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Triastuti, Asih. "Exploration de la diversité chimique dans les endophytes fongiques : influence de l'addition des modificateurs épigénétiques et des co-cultures fongiques sur le métabolome de Botryosphaeria mamane". Thesis, Toulouse 3, 2018. http://www.theses.fr/2018TOU30228.
Testo completoAbstract (sommario):
Ce travail porte sur l'étude chimique d'une souche endophyte de Botryosphaeria mamane, un micromycète relativement peu étudié, isolée des feuilles de Bixa orellana. Des travaux préliminaires portant sur le screening de 409 souches de champignons isolés à partir de plantes médicinales d'Amérique du Sud a révélé que parmi celles-ci, B. mamane E224 était l'une des souches les plus actives in vitro sur un modèle de Leishmania infantum. L'objectif de ce travail a consisté en l'induction de la production de nouveaux métabolites secondaires produits par B. mamane via l'optimisation des conditions de culture de cette souche, la mise en place de méthodes de co-cultures et l'ajout de modificateurs épigénétiques. Une analyse des métabolomes dans les différentes conditions a été réalisée à travers une approche métabolomique, utilisant un couplage UHPLC-HRMS, ainsi que grâce à différents outils statistiques. Deux grandes classes de composés ont ainsi été détectées dans les cultures axéniques de B. mamane. Premièrement, la famille des cyclopeptides, incluant les cyclodipeptides soufrés avec en particulier trois nouveaux composés, les botryosulfuranols A-C. Puis la famille des isocoumarines, avec des dérivés de la melleine (trans-4-hydroxymelleine, 4-hydroxymelleine et 5-hydroxymellein). A travers l'ajout de modificateurs épigénétiques à la culture de B. mamane, nous avons pu étudier les effets de deux inhibiteurs d'histone désacétylases (HDACis), l'acide suberoylanilidehydroxamique (SAHA) et le valproate sodique, ajoutés à deux stades différents de la culture fongique. L'ajout de HDACi dans la culture de B. mamane a entraîné des changements importants dans la production de métabolites secondaires. En effet, une induction de certains métabolites mais également une réduction et l'inactivation de la production d'autres métabolites, ont été observés, et ceci selon la nature du modificateur épigénétique ajouté. Cette étude illustre l'importance du choix des HDACis pour l'induction de la production de métabolites spécifiques. Concernant l'optimisation de la co-culture de B.[...]This study focused on the strain of a poorly studied fungal endophyte Botryosphaeria mamane E224, isolated from Bixa orellana leaves. Our previous screening involving 409 fungal strains isolated from medicinal plants from South America revealed that among all these strains, B. mamane was shown to be the most bioactive on in vitro model against Leishmania infantum. The objectives of this work consisted in the introduction of new metabolite production by B. mamane by optimizing the fungal culture conditions, and by using co-cultivation methods and addition of epigenetic modifiers. This work was followed by an analysis of the different metabolomes via a metabolomics approach using UHPLC-HRMS and integration of informatics and statistical tools for metabolomics. Two major compound classes were detected in B. mamane. First, the cyclopeptide family including the thiodiketopiperazines (TDKPs) alkaloids with three new compounds proposed as botryosulfuranols A-C; and the isocoumarin family, with the mellein derivatives, trans-4-hydroxymellein, 4-hydroxymellein, and 5-hydroxymellein. Regarding the exploration of B. mamane metabolome cultured in the presence of epigenetic modifier, the effects of two different histone deacetylase inhibitors (HDACis), suberoylanilidehydroxamic acid (SAHA) and valproate sodium added in two different stages of fungal growth, were investigated. As expected, HDACis addition in the culture of B. mamane led to significant changes in the secondary metabolite production. Addition of modifier not only induced metabolites production but also reduced and may inactivate metabolite production in fungi, depending on the nature of the epigenetic modifier added. This study illustrates the importance in the choice of HDACis to fungal culture in order to induce specific metabolite productions. In the study of B. mamane and C. albicans co-cultivation in different culture conditions, we showed the influence of the conditions (static versus agitation) on the metabolome of the fungi. However, the co-culture with yeast did not induce any modification in the fungal metabolome. The investigation of fungal interactions between B. mamane, Fusarium solani, and Colletotrichum linicola in 6-multi well plates in time-series based analysis has been carried out. [...]
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Oliver, Katherine Rene. "Consumption of Endophyte Infected Fescue During Gestation in Beef Cows". Thesis, Virginia Tech, 2016. http://hdl.handle.net/10919/81478.
Testo completoAbstract (sommario):
Tall fescue is a widely grown, cool season grass prevalent in the eastern United States that is known for its resistance to abiotic and biotic stresses. A main reason for tall fescue's resistance to these stresses is attributed to the presence of a fungal endophyte. Unfortunately, this endophyte also adversely affects cattle production. Cows consuming the ergot alkaloids produced by these endophytes can exhibit decreased feed intake, growth performance, organ vasoconstriction, and increased rectal temperature. This work is interested in examining how endophyte toxin exposure impacts pregnancy in cattle. Reduced blood flow to the fetus and inadequate maternal nutrition contributes to intra uterine growth restriction (IUGR), and this work proposed that fescue endophyte toxicity affects the gestating cow and fetus. Three studies were completed.
In experiment 1, gestating cows grazed high or low endophyte fescue pastures during late gestation to determine if exposure to ergot alkaloids in utero results in IUGR and if calves from these pregnancies have altered growth performance. Creep feeding was evaluated as a mitigation strategy for impaired calf growth due to fescue toxicity, and feedlot performance was evaluated to determine if consuming fescue during gestation and creep feeding would affect feedlot performance. Calf BW was different (P < 0.01) by treatment x time. Birth weights of calves were similar , prior to creep feeding calves exposed to high endophyte fescue were lower, and post-supplementation creep fed calves had increased BW. Days on feed and dressing percentage were decreased in the supplemented group, and marbling score was decreased for both the supplemented and unsupplemented groups following the completion of the feedlot phase (P < 0.05). The second study was setup similar to study one, however cows were exposed to fescue pastures from d 170 of gestation until calving. Calf birth weights did not differ, but weights were increased in the supplemented group post creep feeding (P < 0.05). Average daily gains (ADG) of supplemented calves were greater during the supplementation period (P < 0.01). In the third study, indwelling vaginal temperature probes were used to evaluate differences in body temperature of cows fed fescue seed with high or low levels of ergot alkaloids during early gestation, and in varying environmental conditions. In the winter trial, body temperature was measured hourly from days 0-14 of gestation. In the summer trial, body temperature was measured hourly from days 0-32 of gestation. Body temperatures were different (P < 0.01) between treatments during both trials.Master of Science
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Owens, Herbert Troye III. "BEEF CATTLE GRAZING PREFERENCE OF TALL FESCUE AS AFFECTED BY ENDOPHYTE". UKnowledge, 2011. http://uknowledge.uky.edu/gradschool_theses/88.
Testo completoAbstract (sommario):
Many factors control, contribute to, stimulate and limit forage selection. It is apparent that cattle prefer certain cultivars compared to others. This study sought to test if cattle displayed preferences for certain cultivars over a two-year period in 2008 and 2009. Determining the effect of endophyte status on preference was another objective. Previous research showed rapid increase in the selection of preferred cultivars, i.e., diet learning. We attempted to replicate those results. Forty cultivars (34 tall fescue (Lolium arundinaceum (Schreb.) Darbysh.) cultivars), two festuloliums (Festuca pratensis x Lolium perenne), two meadow fescue (Lolium pratense) and one meadow brome (Bromus biebersteinii), and one orchard grass (Dactylis glomerta L.)) were used to determine preference and to investigate factors contributing to preference. From this two-year study, we observed that cattle preferred certain cultivars compared to others, e.g. KYFA9819 > Latar-OG > Barfest-FL and AU-Triumph < 97TF1-EF < Seine, the most and least preferred cultivars, respectively. During drought conditions, both novel and toxic endophyte cultivars were preferred significantly (P < 0.05) to endophyte free counterparts. The cattle showed rejection of unpalatable grasses but did not clearly show learning to increase selection of desired cultivars.
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Rickly, Zinner Rachel Ann. "ADAPTATION OF LAMBS TO AN ENDOPHYTE INFECTED TALL FESCUE SEED DIET". UKnowledge, 2011. http://uknowledge.uky.edu/animalsci_etds/3.
Testo completoAbstract (sommario):
Ten wether lambs were used to determine the effects of ergovaline consumption from endophyte infected tall fescue, on nutrient utilization and metabolism. Lambs were fed a diet of 23% endophyte free tall fescue seed (E-) and 77% concentrate from d -14 to -1 (adaptation phase). On d 0, five lambs were switched to an endophyte infected seed diet (E+) where they remained through d 14. Nutrient digestibilities tended to increase from adaptation through the acute (d 1 to 4) to subacute (d 10 to 14) phases when E- was fed. E+ digestibilities were highest (P < 0.05) in the acute phase. Lambs fed E+ had higher rectal temperatures in the acute (P < 0.01) and subacute phases (P < 0.05). Fecal recovery of ergovaline increased as day of collection increased in the acute and subacute phases. Lysergic acid fecal recovery increased with day of collection in the acute phase, but no effect was found in the subacute phase. Serum enzyme analyses did not indicate tissue damage from alkaloid consumption. These results demonstrate lambs try to adapt to endophyte infected fescue seed consumption through increased nutrient digestibilities and increased ergovaline and lysergic acid excretion.
19
Bagherzadeh, Mahtaab. "CAN INCREASING GRASS-FUNGAL ENDOPHYTE SYMBIOTIC DIVERSITY ENHANCE GRASSLAND ECOSYSTEM FUNCTIONING?" UKnowledge, 2018. https://uknowledge.uky.edu/pss_etds/105.
Testo completoAbstract (sommario):
The relationship between biodiversity and ecosystem functioning is important in maintaining agroecosystem sustainability. Plant-microbe symbioses, such as exists between the grass tall fescue (Schedonorus arundinaceum) and the asexual fungal endophyte Epichloë coenophiala, can be utilized to enhance agroecosystem functions, such as herbivore resistance. “Novel” E. coenophiala strains that vary in the production of mammal- and insect-toxic compounds have been identified, inserted into tall fescue cultivars, and are planted in pastures globally. Novel fungal endophyte-tall fescue associations may have divergent ecosystem function effects. This study assessed effects of different fescue-endophyte symbiotic combinations on pasture ecosystem function, including aboveground (fescue biomass, plant species richness, alkaloid synthesis, arthropod abundance) and belowground (soil microbial biomass, soil enzyme activity, trace gas fluxes) parameters. Results showed no significant effects of increasing symbiotic diversity within a fescue stand on aboveground measurements, bar arthropod abundance and alkaloid synthesis. Most soil parameters quantified had significant symbiotic diversity effects. For example, soil microbial biomass decreased whereas soil enzyme activity increased with increasing symbiotic diversity. Overall, our results suggested that increasing symbiotic diversity had weak to moderate effects on aboveground processes and stronger effects on certain belowground processes, indicating that symbiotic diversity can impact ecosystem functions and warrants further research.
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O'Callaghan, Kenneth John. "Interactions of rhizobia with Sesbania rostrata, wheat and oilseed rape : a comparative study". Thesis, University of Nottingham, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.285558.
Testo completo
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Brosi, Glade Blythe. "THE RESPONSE OF TALL FESCUE AND ITS FUNGAL ENDOPHYTE TO CLIMATE CHANGE". UKnowledge, 2011. http://uknowledge.uky.edu/gradschool_theses/126.
Testo completoAbstract (sommario):
Tall fescue is the most common cool-season grass in the eastern USA, with broad economic and ecological importance to the region. Tall fescue is known to associate with a fungal endophyte, Neotyphodium coenophialum, whose presence can decrease biotic and abiotic stress experienced by the plant. This thesis evaluates the response of tall fescue and the fungal endophyte symbiosis to predicted climate change. I participated in two multi-factor climate change projects where I investigated the response of tall fescue tissue chemistry and growth to various climate change factors. Endophyte-infected (E+) tall fescue had decreased alkaloid production under elevated CO2 but increased alkaloid production under elevated temperatures. Significant differences between E+ and E- (endophyte-free) tall fescue tissue chemistry were also found, suggesting the endophyte interacts with the plant response to abiotic stress. Although several studies have reported benefits of endophyte infection for tall fescue growing under drought stress, my research found no differences between E+ and E- total growth and surprisingly showed increased mortality of E+ individuals under elevated temperature. Taken together, my research indicates that this grass-fungal relationship will respond to climate change, and may produce dramatic and unforeseen results that question the widely believed mutualistic nature of the symbiosis.
22
Bourguignon, Marie. "Ecophysiological Responses of Tall Fescue Genotypes to Endophyte Infection and Climate Change". UKnowledge, 2013. http://uknowledge.uky.edu/pss_etds/28.
Testo completoAbstract (sommario):
Tall fescue is a widely used forage grass in the eastern USA and can form a symbiosis with a fungal endophyte, which can be beneficial for the plant but can cause livestock health issues. Little is known regarding the symbiotic response to predicted climate change. To address this knowledge gap, I analyzed tall fescue variety trial data collected throughout the U.S., exploring relationships between climate variables and yield for two different fescue cultivars that were either endophyte-free or infected. This study showed no endophyte or cultivar effect on fescue yield, but identified temperature, precipitation and location as significant predictors of yield, suggesting that local conditions were more important than endophyte presence or fescue genotype for this dataset. Using a field experiment located in central Kentucky, I quantified the ecophysiological responses of four tall fescue genotypes to endophyte presence, elevated temperature and increased growing season precipitation. In this study, tall fescue genotype was as important as endophyte presence in determining ecophysiological responses to climate change treatments. My thesis illustrates that tall fescue response to climate change will depend on host genetics, the presence and genetics of the fungal endophyte symbiont, and the specific changes to the environment experienced at a site.
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Ben, Chobba Kadri Inès. "Élaboration et mise en oeuvre d'une approche de caractérisation systémique d'un agent étiologique émergent à fort impact économique et de moyens de lutte biologique : application à la maladie de la feuille cassante du palmier dattier (Phoenix dactylifera L.)". Thesis, Montpellier 2, 2013. http://www.theses.fr/2013MON20077.
Testo completoAbstract (sommario):
La Maladie de la Feuille Cassante du Palmier dattier (Phoenix dactylifera L.) constitue un cas d'émergence d'une maladie à fort impact économique causée par un agent étiologique inconnu. Notre stratégie a visé à élaborer une approche sans à priori de l'émergence pouvant être transposée à n'importe quelle situation de ce type. En nous appuyant sur des caractérisations successives des compartiments viraux, bactériens et fongiques de tissus sains et malades, nous avons cherché à mettre en évidence des différences de composition spécifiques et de distribution de ces flores sur 2 campagnes de prélèvements réalisées en 2010 et 2012. Alors que la microscopie électronique à transmission nous a permis de visualiser des structures d'origine virale probable au niveau des chloroplastes du parenchyme chlorophyllien, une étude moléculaire de séquençage de gènes ribosomaux nous a permis de corréler l'apparition de ces structures a de profondes modifications qualitative et quantitative de la microflore endophyte. Ainsi il nous est apparu que la symptomologie de la maladie était corrélée à une modification profonde de la distribution spécifique de la microflore endophyte, visible à la fois au niveau du compartiment fongique et bactérien, suggérant la complète disparition de la pression de sélection exercée par le palmier sain sur sa flore et mise en évidence dans les 2 cas, par un shift d'une répartition de type Poisson vers une répartition normale. Dans le compartiment fongique, une claire déplétion des Pleosporaceae, associées à la plante saine pouvait ainsi être liée à une apparition de nouvelles familles (Trichocomaceae et Mycosphaerellaceae). De même, parmi les bactéries, une disparition des Rhizobium et Ensifer sp associés au compartiment racinaire de la plante saine a ainsi pu être mise en évidence, ces espèces pouvant servir ultérieurement d'indicatrices de bonne santé des palmiers. Dans une deuxième partie de notre travail nous avons cherché à utiliser des éléments de la flore endophyte mais également de substances naturelles dans la lutte biologique contre d'autres pathogènes du palmier. Ainsi, un antagonisme a été mis en évidence entre une souche endophyte d'Arthrobacter agilis et un pathogène majeur, Fusarium oxysporum sp AlbedinisThe Brittle Leaf Disease of the Date Palm Tree (Phoenix dactylifera L.) constitutes a case study of an emerging disease of economic impact caused by a yet uncharacterized etiologic agent. Our strategy was to develop an approach that could be indistinctly transposed to any situation of this type. While basing our investigations on the successive characterization of the diversity of viral, bacterial and fungal endophytic compartments of healthy and diseased Palm trees, we aimed at enlightening differences in species composition but also distribution over two sampling campaigns performed in 2010 and 2012. While transmission electronic microscopy allowed us to visualize structures of probable viral origin affecting chloroplasts of the chlorophyllic cell layer, a molecular approach based on ribosomal gene sequencing allowed us to evidence correlations between the occurrence of such structures and deep modifications of the structure of the palm date tree associated endophytic flora suggesting a strong depletion of the ability of the palm to control its associated endophytes. This was evidenced in both fungal and bacterial compartments by a shift from a Poisson like diversity distribution towards a Gaussian distribution in the flora associated to MFC affected palms. In the fungal compartment, Pleosporaceae, that dominated in healthy palms were replaced by an opportunistic flora of Trichocomaceae and Mycosphaerellaceae. Among bacteria, the disappearance of Rhizobium and Ensifer species, typically associated to the root compartment of healthy palms was enlighten, suggesting that these species could indeed be used as biomarkers of healthy plant status. In a second part of this study, we investigated the potential use of cultivable palm endophytes, but also natural compounds for biocontrol applications. In particular, we evidence the antagonistic potential of Arthrobacter agilis, a palm endophyte, against a major palm date disease agent, Fusarium oxysporum sp. Albedinis
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Weedon, C. M. "Biosynthesis of indole-diterpenoids and other isoprenoids by the ryegrass endophyte, Acremonium loliae". Thesis, Imperial College London, 1988. http://hdl.handle.net/10044/1/47298.
Testo completo
25
Ndoye, Idrissa. "Isolement et approche synthétique de produits naturels issus du champignon endophyte Paraconiothyrium variabile". Paris 6, 2012. http://www.theses.fr/2012PA066314.
Testo completoAbstract (sommario):
Paraconiothyrium variabile est un champignon endophyte isolé du conifère Cephalotaxus harringtonia et a révélé un antagonisme significatif contre des phytopathogènes communs. Nous avons entrepris la caractérisation chimique des métabolites fongiques impliqués dans la relation mutualiste entre cette plante hôte et le champignon endophyte afin d'étudier leur rôle éventuel dans cet antagonisme. Le fractionnement de l'extrait AcOEt du filtrat de culture de P. Variabile a révélé quatre principales familles de métabolites : α-tétralones, isocoumarines, isobenzofuranes et cyclodipeptides dans des conditions de culture différentes. La configuration absolue des trois α-tétralones portant un hydroxyle en C-4 a été déterminée comme S par analyse de leurs spectres de dichroïsme circulaire. La biotransformation de la juglone et de l'isosclérone par P. Variabile a permis d’augmenter les quantités d'isosclérone et d’obtenir des analogues structuraux, respectivement. Des essais de dimérisation de l'isosclérone en milieu acide ont été réalisées vers le squelette naturel spirobisnaphtalène de type palmarumycine. Par ailleurs, un travail annexe apporte une contribution supplémentaire à la synthèse du précurseur linéaire des hirsutellonesParaconiothyrium variabile is an endophytic fungus isolated from the conifer Cephalotaxus harringtonia and displayed a significant antagonism against common plant pathogens. We undertook the chemical characterization of the fungal metabolites implied in the mutualistic relationship between the host plant and the endophyte in order to study their role in the observed antagonism. The analysis of the AcOEt extract of the culture filtrate of P. Variabile revealed four main families of metabolites: α-tetralones, isocoumarin, isobenzofuran, and a cyclodipeptide obtained in different culture conditions. The absolute configuration of three α-tetralones with a hydroxyl at C-4 was determined S by analysis of their circular dichroism spectra. The biotransformation of juglone and isosclerone led to increased amount of isosclerone and structural analogues, respectively. Dimerization of isosclerone under acidic conditions gave the best results towards the natural spirobisnaphtalene skeleton of palmarumycins. Additionally, a contribution to the synthesis of a biomimetic linear precursor of hirsutellones was done
26
Vazquez, Ana M. "Possible Drivers in Endophyte Diversity and Transmission in the Tomato Plant Bacterial Microbiome". The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1594918263597025.
Testo completo
27
Huang, Yu-Ling, e Yu-Ling Huang. "An Integrative Study of Endophyte Symbioses: Environmental Change, Evolutionary Dynamics, and Leaf Colonization". Diss., The University of Arizona, 2017. http://hdl.handle.net/10150/625616.
Testo completoAbstract (sommario):
Fungi have evolved to encompass a diversity of strategies that collectively allow them to occupy the majority of earth’s ecosystems. Among these, endophytism is one of the most widespread and yet least well understood. Endophytes are fungi that live in plants without causing disease. These fungal symbionts are highly diverse and have been found in plants from tropical forests to hot deserts and arctic tundra. Even though endophytes are globally distributed as a whole, it is clear that environmental factors, interactions with potential hosts, and a variety of evolutionary processes together determine the content of endophyte communities at various geographic scales. Fragmentary sampling provides useful but limited information to our understanding of endophyte diversity, such that large-scale surveys that take into account major environmental factors are needed. Such work is urgent for documenting biodiversity in the context of climate change and other environmental shifts. At the same time, examining endophyte communities in the context of such shifts helps clarify how environmental factors shape endophyte assemblages, and how fungal lineages that contain endophytes arise and diversify relative to environment-driven selection. These broader dynamics of endophyte ecology and evolution reflect the foundational process of leaf colonization by fungi –– yet colonization has not been studied extensively nor visualized carefully in the most diverse and abundant plant lineages. In this dissertation, I used the dynamic history of wildfire in the southwestern USA to understand how endophyte communities differ as a function of time since pervasive environmental change. I then conducted a case study using exhaustive collections of endophytes to discover the biogeography and environmental factors relevant to endophyte community structure. To place these studies in an evolutionary context, I reconstructed ancestral states to understand the evolution of ecological modes in a focal class of fungi in which evolutionary processes of diversification appear to be particularly dynamic and endophytes are phylogenetically diverse. Finally, I used microscopy and inoculation experiments to observe the process of leaf colonization by endophytes, with a special focus on a model woody plant and members of three classes of Ascomycota. Together these studies reveal that pervasive environmental changes have significant and lasting effects on the diversity and community structure of endophytes; that endophyte community structure at a regional scale tracks the biogeographic structure of plant communities; that endophytes in a focal class have multiple origins from different ancestral states, consistent with their tremendous biodiversity and diversity of function; and that focal endophytes that sporulate prodigiously appear to colonize leaves and persist at low biomass by opportunistically entering leaf tissue and growing intercellularly. This integrative study extends our understanding of endophytes in terms of plant biology, forest ecology, community ecology, and evolution, and provides a perspective on one of the most widespread and important symbioses between plants and fungi.
28
Al-Busaidi, Harith N. K. "Secondary metabolites from Xylaria endophytes : the isolation and structure elucidation of secondary metabolites from Xylaria endophytes by chemical and spectroscopic methods". Thesis, University of Bradford, 2011. http://hdl.handle.net/10454/5266.
Testo completo
29
Blankenship, Jimmy Douglas. "LOLINE ALKALOID BIOSYNTHESIS IN NEOTYPHODIUM UNCINATUM, A FUNGAL ENDOPHYTE OF LOLIUM PRATENSE". Lexington, Ky. : [University of Kentucky Libraries], 2004. http://lib.uky.edu/ETD/ukyplpa2004d00157/JDB2004.pdf.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--University of Kentucky, 2004.Title from document title page (viewed Sept. 14, 2004). Document formatted into pages; contains ix, 97 p. : ill. Includes abstract and vita. Includes bibliographical references (p. 86-96).
30
CONCAS, JONATHAN. "Spatial Distribution of Grapevine Esca Disease in Vineyards of the Marche Region and Study of Fungal Endophytic Communities". Doctoral thesis, Università Politecnica delle Marche, 2019. http://hdl.handle.net/11566/263846.
Testo completoAbstract (sommario):
Il mal dell’esca è una malattia complessa, determinata da diversi agenti fungini, che ha attualmente un importante impatto economico sulla viticoltura mondiale. I principali obiettivi della ricerca sono stati i) l’analisi spaziale delle viti con sintomi di mal dell’esca e ii) lo studio delle comunità fungine in viti sintomatiche e asintomatiche. Per quanto riguarda il primo obiettivo, è stato condotto uno studio sulla diffusione del mal dell’esca in tre vigneti commerciali nelle Marche, in modo da poter comprendere meglio come l’infezione evolve nel tempo e nello spazio. Dall’elaborazione dei dati è stato possibile verificare che i) nel 2017 e 2018, in nessuno dei vigneti è presente un gradiente di malattia tra le file, ii) è presente un gradiente di malattia in direzione Est-Ovest nel vigneto OS1 mentre nel vigneto OS2 è presente una concentrazione di piante sintomatiche nella parte centrale rispetto ai bordi, iii) è stata registrata una significativa correlazione tra incidenza della malattia e portinnesto nel vigneto OS1. Il secondo obiettivo ha riguardato le popolazioni di funghi endofiti in presenza o assenza di sintomi di mal dell’esca. Trentaquattro specie fungine sono state identificate su base morfologica e utilizzando tecniche molecolari e il sequenziamento della regione ITS. In particolare, Phaeoacremonium sp., Fomitiporia mediterranea e Phaeomoniella chlamydospora sono stati isolati da piante sintomatiche. Inoltre, diversi funghi endofiti non patogeni, di cui è noto il loro ruolo come agenti di biocontrollo, sono stati isolati da piante sintomatiche ed asintomatiche. Ulteriori studi saranno necessari per migliorare le conoscenze circa il ruolo della micoflora nell’espressione dei sintomi di mal dell’esca, usando tecnologie innovative (Next Generation Sequencing) e considerando non solo le comunità fungine, ma l’intero microbioma.The disease currently known as esca is a multiple fungal syndrome. It is considered to be a complex disease that has heavy impact on viticulture around the World. This study focuses on the spatial distribution of grapevine esca, and the ecological significance and role of the fungal endophyte communities in symptomatic and asymptomatic grapevines. For the first aspect, three commercial vineyards in the Marche region (central Italy) have been examined as part of a study of the spread of esca. This is designed to determine the dissemination patterns that provide indications of both directionality and evolution of infection over time. The data collected and analysed demonstrated that in 2017 and 2018: (i) none of the vineyards showed any gradient of infection among the rows; (ii) there was a west-east gradient of infection in vineyard OS1, and in vineyard OS2 there was greater concentration of disease in the centre than at the edges; and (iii) there was significant correlation between esca incidence and rootstock for vineyard OS1. The second aspect to this study was to establish how the population structure of fungal endophytes changed according to presence of esca-related pathogens. Thirty-four fungal species were isolated and identified by morphological and molecular tools. In particular, Phaeoacremonium sp., Fomitiporia mediterranea, and Phaeomoniella chlamydospora were mainly isolated from symptomatic plants. Moreover, several non-pathogenic and endophytic fungal species were isolated from asymptomatic and symptomatic grapevines, for which they might represent biocontrol agents. Further studies using innovative technologies will be carried out to improve our knowledge of the role of the mycoflora in suppressing esca symptoms (e.g., next-generation sequencing). These will not only consider the endophytic fungal communities, but also the whole microbiome.
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Nebert, Lucas. "On Germs and Germination: Uncovering the Hidden Ecology of Seedborne Bacteria and Fungi in Open-Pollinated Maize". Thesis, University of Oregon, 2018. http://hdl.handle.net/1794/23909.
Testo completoAbstract (sommario):
Plants are inhabited by diverse species of bacteria and fungi, which affect plant health and fitness. Endophytes are bacteria or fungi that live within plant host tissues without causing symptoms of disease, and mediate important plant traits in agriculture, such as nutrient acquisition, disease resistance, and abiotic stress tolerance. However, we know little about the general ecology of endophytes, including which factors determine their compositions within plants. Seedborne transmission may represent an important source of bacterial and fungal endophytes, which can significantly impact the plant microbiome and plant traits. However, seeds are also a vehicle for transmission of plant pathogens. Seeds are commonly treated to control against seedborne pathogens, and increasingly bacteria and fungi are inoculated onto seeds to serve as biological control against pathogens. My dissertation explores the theoretical and applied ecology of seedborne endophytes of maize, including their interactions with pathogenic Fusarium fungi, and with seed treatments designed to control Fusarium.
In Chapter II, I examine factors that affect the transmission of seedborne fungal endophytes and Fusarium into maize seedlings, including the influence of soil microbiota, and the impact of disinfection and biological control seed treatments. In Chapter III, I determine the long-term effects of seed disinfection and biological control inoculants on maize bacterial and fungal endophytes and Fusarium pathogenicity across three different farms. In Chapter IV, I recruit maize seed growers across the Pacific Northwest and U.S. to participate in a broadscale study of seedborne endophytes. Across submitted seed samples, I find commonly occurring seedborne endophyte taxa, and delineate how maize varieties interact with environmental factors to affect the composition and diversity of seed-associated endophytes in seeds. Throughout these chapters, I explore the potential applications of seedborne endophytes in agriculture, particularly as a source for biological control against Fusarium in maize, and speculate how seed treatments can have significant, lasting impacts on the plant microbiome.
32
Johnson, Jennifer Michelle. "GRAZING EVALUATION OF A NOVEL ENDOPHYTE TALL FESCUE DEVELOPED FOR THE UPPER TRANSITION ZONE". UKnowledge, 2010. http://uknowledge.uky.edu/gradschool_diss/111.
Testo completoAbstract (sommario):
A wild-type endophyte (Neotyphodium coenophialum [(Morgan-Jones & Gams) Glen Bacon & Hanlin]) that infects tall fescue [Lolium arundinaceum (Schreb.) Darbysh. = Schedonorous arundinaceum (Schreb.) Dumort.] imparts tolerances to moisture, heat, and grazing stresses, but also produces ergot alkaloids that adversely affect performance and physiology of cattle. Novel endophytes, developed by AgResearch Ltd. NZ, can sustain fescue persistence and productivity, but do not produce toxic ergot alkaloids. University of Kentucky Plant Breeder, T. D. Phillips Ph.D, developed a tall fescue experimental population (KYFA9301) for the upper transition zone. A 2-yr grazing experiment was conducted with steers to evaluate steer performance and physiology, and forage quality and productivity of KYFA9301 infected with AR584 novel endophyte (AR584) compared with KY31 wild-type endophyte (KY31), endophyte-free KYFA9301 (EF9301) and AR542-‘Jesup’ (MaxQ). Fescue-endophyte combinations were assigned to 1.0-ha pastures in a randomized complete block design with three replications. Pastures were grazed with variable stocking (four testers) from 6 May to 23 July 2008 (76 d), and 2 April to 25 June 2009 (84 d). Shrunk bodyweights were taken at initiation and termination of grazing each year. Average daily gains among MaxQ, AR584, and EF9301 were similar and were greater (P < 0.10) than KY31. Rectal and skin temperatures were collected three times each year at approximately days 28, 56, and study completion, along with blood collection for serum prolactin assay. Rectal and skin temperatures among AR584, MaxQ, and EF9301 were similar and were lower (P < 0.10) than KY31. Serum prolactin concentrations were similar among the three nontoxic varieties and higher (P < 0.10) than KY31. Forage collections were taken at 2 week intervals throughout the study each year and nutritive quality analysis were conducted through wet chemistry to determine forage acid detergent fiber (ADF), neutral detergent fiber (NDF), crude protein (CP), and In-Vitro Dry Matter Digestibility (IVDMD). Nutritive analyses indicated no differences between fescue-endophyte combinations with the exception of EF9301 having higher ADF concentrations (P = 0.031) than KY31 during the dry year of 2008. Results indicated steer performance and physiological responses for KYFA9301, with and without AR584 were enhanced compared to KY31 and similar to those for MaxQ.
33
Bussard, Jessica R. "Evaluation of vascular changes in cattle relative to time-off endophyte-infected tall fescue". UKnowledge, 2012. http://uknowledge.uky.edu/pss_etds/7.
Testo completoAbstract (sommario):
Twenty-four steers were grazed on endophyte (Neotyphodium coenophialum)-infected [[Lolium arundinaceum (Schreb.) Darbysh]; E+] tall fescue (TF) and exposed to ergot alkaloids for an 106-d grazing period. Cattle were removed from pasture, placed in dry lots, and fed a non-toxic diet to evaluate changes in vascular contraction relative to time-off E+ TF pasture. Lateral saphenous veins (SV) were biopsied from steers at 0-, 21-, 42-, and 63-d off TF pasture and from 6 control steers at 0- and 63-d off bermudagrass (BG) pasture. To evaluate contractile response, biopsied SV were exposed to increasing concentrations of ergotamine in a multimyograph. Cross-sectional scans of the caudal artery were taken using color Doppler ultrasonography on 0-, 8-, 15-, 21-, 29-, 36-, 42-, and 45-d to determine artery luminal area. Contractility of SV was less for TF than BG steers on d 0, but was similar between the two treatments by d 63. Luminal areas of the caudal arteries in E+ TF steers relaxed over time and were similar to BG steers by 36 d off pastures. Results indicated that alkaloid-induced vasoconstriction in cattle grazed on E+ TF can be relaxed in 5 to 6 weeks after they are placed on non-toxic diets.
34
Al-Busaidi, Harith. "Secondary Metabolites from Xylaria Endophytes: The isolation and structure elucidation of secondary metabolites from Xylaria endophytes by chemical and spectroscopic methods". Thesis, University of Bradford, 2011. http://hdl.handle.net/10454/17479.
Testo completoAbstract (sommario):
This thesis describes the isolation and structure elucidation of secondary metabolites from a number of endophytic Xylaria fungi. Six Xylaria endophytes were surface cultured on an aqueous malt extract-glucose medium. The fungus A311R, from a palm tree in Thailand, produced nonane-1,2,3-tricarboxylic acid, which was isolated for the first time as a natural product. Also isolated from the same fungus was spiculisporic acid; the first instance of isolation from a Xylaria fungus. The fungus 6RD12 produced cycloepoxydon, which was isolated for the first time from a Xylaria fungus, and 4,5,6-trihydroxy-3-propyl-3,4,6,7-tetrahydro-l//-isochromen- 8(5//)-one, which is a novel compound. The fungi A217R and A517R produced cytochalasin D, (S)-mellein and (3S,4S)-4-hydroxymellein as main secondary metabolites suggesting that the two fungi are the same species. The fungus X04 (Xylaria cf. juruensis) produced 2-Hydroxy-5-ethoxy-3-methylcyclohexa-2,5-dien- 1,4-dione as a novel compound, coriloxin as the main secondary metabolite in addition to (R)-mellein and a mixture of two stereoisomers of the 4-Hydroxymellein. The fungus 6RD8 produced (S)-Omethylmellein as the main secondary metabolite.
l
35
ZHANG, DONG-XIU. "LOLINE ALKALOID BIOSYNTHESIS GENE EXPRESSION IN EPICHLOE ENDOPHYTES OF GRASSES". UKnowledge, 2008. http://uknowledge.uky.edu/gradschool_diss/592.
Testo completoAbstract (sommario):
Loline alkaloids (LA) are secondary metabolites produced by Epichloandamp;euml; (anamorph, Neotyphodium) grass endophytes. They are toxic and deterrent to a broad range of herbivorous insects but not to livestock. This protective bioactivity has spurred considerable research into the LA biosynthetic pathway. LOL, the gene cluster containing nine genes, is required for LA biosynthesis. The regulation of LOL genes during LA production in culture and in symbio is of interest. In this study, coordinate regulation between LOL gene expression and LA production level was investigated in both MM culture and symbiota. Results showed that expression of LOL genes in N. uncinatum MM culture were tightly correlated with each other (p andamp;lt; 0.0005), and all presented a significant temporal quadratic pattern during LA production. Gene expression started before LA were detectable, and increased while LA accumulated. The highest gene expression level was reached before the highest amounts of LA were detected, and gene expression level declined to a very low level after amounts of LA plateaued. Observations suggested that the hierarchical clusters based on the correlation coefficient could help to predict the roles of LOL genes in the LA pathway. In symbiota, coordinate coregulation of LOL gene expression with LA was found in E. festucae-meadow fescue inflorescences and stromata, whereby lower LOL gene expression corresponded with the lower LA level in stromata. In N. uncinatum (or N. siegelii)-meadow fescue vegetative tissues, dramatically higher LA levels were found in younger leaf tissue than in older leaf tissue, yet no evidence was found to relate this difference to LOL gene expression differences. Instead, substrate availability may regulate the LA level. In particular, asparagine was more than 10-fold higher in young leaf tissue than in old tissue, although proline was significantly lower in young tissue. Therefore, different regulatory mechanisms underlie LOL gene expression and LA production in different circumstances. The GUS activity of Pro-lolC2-GUS and Pro-lolA2-GUS in Neotyphodium species was almost undetectable in culture, though the activity could be detected in symbiota. The mRNA of GUS did not exhibit the same pattern as lolC2 or lolA2 in culture during LA production time course. A Pro-lolC2-cre transgene was expressed in complex medium, in which lolC2 mRNA was not detectable. These results suggest that proper regulation of LOL genes in culture or symbiota is dependent on the LOL cluster.
36
Arriola, Apelo Sebastian I. "Influence of forage characteristics on grazing behavior of weaned steers". Thesis, Virginia Tech, 2009. http://hdl.handle.net/10919/33311.
Testo completoAbstract (sommario):
For Virginia, the primary forage base is endophyte-infected tall fescue (Schedonorus phoenix (Scop.) Holub). However, the decreased animal performance and disorders caused by the presence of the fungal endophyte Neotyphodium coenophialum reduces its suitability for many forage-livestock producers. The endophyte, which is found in the inter-cellular space of tall fescue tissues, forms a mutalistic relationship with the plant and helps the fescue tolerate drought, insect predation, and grazing pressure. The production of toxic ergot alkaloids by the endophyte is associated with decreased performance of animals that graze endophyte infected tall fescue. The objective of the current experiment was to determine how tall fescue type (endophyte free vs novel endophyte) and orchardgrass-legume (alfalfa vs clover) mixture affect grazing behavior of weaned steers. Forty-eight weaned steers (218 ± 18 kg) were blocked by frame score (medium and large), and randomly assigned within block to four treatments with three replications in a 2x2 factorial design. Each treatment consisted of 2 paddocks with the combination of tall fescue and legume-orchardgrass mixture as follow: alfalfa-orchardgrass mixture (A)/E-, clover-orchardgrass mixture (C)/E- , A/E++ and C/E++. Each group of 4 steers had 24 h access to both tall fescue stand and legume-orchardgrass mixture. Botanical composition of paddocks was determined on d 0, and forage mass, sward height and nutritive value were determined on d 0, 17 and 33. Behavior of steers was scanned every 5 min on d 24 and 25 from 0700 to 1900. The proportion of legumes was higher (P = 0.001) in A paddocks(37 %) compared to C paddocks (6%), while the percent orchardgrass was lower (P = 0.040) in A (33 %) than C (53 %). The proportion of broadleaf and grassy weeds was higher (P = 0.013) in E- paddocks (11 %) as compared with E++ paddocks (3 %). Sward height and herbage mass were similar between treatments during the experiment (P > 0.05). Nutritive value (CP, NDF and ADF) did not differ between fescue paddocks (P > 0.05). However, within mixed swards, CP was higher and NDF was lower in A compared with C (P < 0.05). Acid detergent fiber was (P < 0.05) lower in A than C only on d 0 and 17. Average daily gain did not differ between treatments (P > 0.05). Steers spent higher (P = 0.002) proportion of the daylight time grazing in treatments with C (56 %) as compared with A (50 %), and in treatments (P = 0.023) with E++ (55 %) compared with E- (52 %). Time spent ruminating, idling and lying, as well as steps taken per day, did not differ between treatments (P > 0.05). Regardless of differences in weeds between E- and E++, these results indicate that fescue type affected grazing behavior of calves. Difference between mixed swards in proportion of ground cover with legumes and orchardgrass, as differences in nutritive value between A and C may have affected grazing behavior of calves between mixed swards, instead of a legume species effect within mixtures.Master of Science
37
Hoffman, Michele Therese. "Bacterial Endosymbionts of Endophytic Fungi: Diversity, Phylogenetic Structure, and Biotic Interactions". Diss., The University of Arizona, 2010. http://hdl.handle.net/10150/196079.
Testo completoAbstract (sommario):
This dissertation comprises a series of studies designed to explore the associations between plants and the endophytic fungi they harbor in their above-ground tissues. By viewing endophyte diversity in ecologically and economically important hosts through the lenses of phylogenetic biology, microbiology, and biotechnology, this body of work links plant ecology with newly discovered symbiotic units comprised of endophytic fungi and the bacteria that inhabit them.This work begins with a large-scale survey of endophytic fungi from native and non-native Cupressaceae in Arizona and North Carolina. After isolating over 400 strains of endophytes, I inferred the evolutionary relationships among these fungi using both Bayesian and parsimony analyses. In addition to showing that native and introduced plants contained different endophytes, I found that the endophytes themselves harbor additional microbial symbionts, recovering members of the beta- and gamma-proteobacterial orders Burkholderiales, Xanthomonadales, and Enterobacteriales and numerous novel, previously uncultured bacteria. This work finds that phylogenetically diverse bacterial endosymbionts occur within living hyphae of multiple major lineages of ascomycetous endophytes.A focus on 29 fungal/bacterial associations revealed that bacterial and fungal phylogenies are incongruent with each other and did not reflect the phylogenetic relationships of host plants. Instead, both endophyte and bacterial assemblages were strongly structured by geography, consistent with local horizontal transmission. Endophytes could be cured of their bacterial endosymbionts using antibiotics, providing a tractable experimental system for comparisons of growth and metabolite production under varying conditions. Studies of seven focal fungal/bacterial pairs showed that bacteria could significantly alter growth of fungi at different nutrient and temperature levels in vitro, and that different members of the same bacterial lineages interact with different fungi in different ways.Focusing on one isolate, I then describe for the first time the production of indole-3-acetic acid (IAA) by a non-pathogenic, foliar endophytic fungus (Pestalotiopsis neglecta), suggesting a potential benefit to the host plant harboring this fungus. I show that this fungus is inhabited by an endohyphal bacterium (Luteibacter sp.) and demonstrate that mycelium containing this bacterium produces significantly more IAA in vitro than the fungus alone. I predict that the general biochemical pathway used by the fungal-endohyphal complex is L-tryptophan-dependent and measure effects of IAA production in vivo, focusing on root and shoot growth in tomato seedlings.
38
Al, Rashed Hussain Ali. "EVALUATION OF A NOVEL ENDOPHYTE-INFECTED TALL FESCUE CULTIVAR AS A SAFE FORAGE FOR PREGNANT MARES". MSSTATE, 2009. http://sun.library.msstate.edu/ETD-db/theses/available/etd-11062009-132030/.
Testo completoAbstract (sommario):
Fescue toxicosis is a condition that afflicts livestock grazing endophyte-infected tall fescue and is particularly detrimental to pregnant mares. A two year evaluation study of a novel endophtye-infected cultivar, AGRFA-144 (A-144), did not induce fescue toxicosis in late-term pregnant mares. All mares delivered viable foals except in E+ group which had two viable foals, one stillborn-dystocia and one compromised foal which was euthanized at 72 h pp. Serum P4 concentrations were similar among A-144, NE+, and E- mares (p>0.05). Foal BW and foal/placental weight ratios were similar for A-144, NE+, and E- (p>0.05). Foal serum P4 was similar on 1 d and 2 d in all groups, but was lower (p = 0.049) in the A-144 group than the E- foals on day 0. Neutrophil/lymphocyte ratios were similar (~5:1) in all foals on d 0 and 2. IgG values were similar (p>0.05) among A-144, NE+, and E-.
39
McClanahan, Linda Kay. "Hair coat and steroidal implant effects on steers grazing endophyte-infected tall fescue during the summer". Lexington, Ky. : [University of Kentucky Libraries], 2007. http://lib.uky.edu/ETD/ukycrsc2007t00580/Thesis.pdf.
Testo completoAbstract (sommario):
Thesis (M.S.)--University of Kentucky, 2007.Title from document title page (viewed on June 14, 2007). Document formatted into pages; contains: vii, 57 p. : ill. Includes abstract and vita. Includes bibliographical references (p. 48-56).
40
Guo, Jingqi. "THE INFLUENCE OF TALL FESCUE CULTIVAR AND ENDOPHYTE STATUS ON ROOT EXUDATE CHEMISTRY AND RHIZOSPHERE PROCESSES". UKnowledge, 2014. http://uknowledge.uky.edu/pss_etds/50.
Testo completoAbstract (sommario):
Tall fescue (Lolium arundinaceum (Schreb.) Darbysh.) is a cool-season perennial grass used in pastures throughout the Southeastern United States. The grass can harbor a fungal endophyte (Epichloë coenophiala) thought to provide the plant with enhanced resistance to biotic and abiotic stress. However, the alkaloids produced by the common variety of the endophyte cause severe animal health issues resulting in a considerable amount of research focused on eliminating the toxic class of alkaloids while retaining the positive abiotic and biotic stress tolerance attributes of the other alkaloids. In doing so, very little attention has been paid to the direct influence the fungal-plant symbiosis has on rhizosphere processes. Therefore, my objectives were to study the influence of this relationship on plant biomass production, root exudate composition, and soil biogeochemical processes using tall fescue cultivars PDF and 97TF1 without an endophyte (E-), or infected with the common toxic endophyte (CTE+), or with two novel endophytes (AR542E+, AR584E+). I found that root exudate composition and plant biomass production were influenced by endophyte status, tall fescue cultivar, and the interaction of cultivar and endophyte. Cluster analysis showed that the interaction between endophyte and cultivar results in a unique exudate profile. These interactions had a small but perceptible impact on soil microbial community structure and function with an equally small and perceptible impact on carbon and nitrogen cycling in soils from rhizobox and field sites. These studies represent the first comprehensive analysis of root exudate chemistry from common toxic and novel endophyte infected tall fescue cultivars and can be used to help explain in part the observed changes in C and N cycling and storage in pastures throughout the Southeast U.S..
41
Jia, Yang. "INTERACTION OF ISOFLAVONES AND ENDOPHYTE-INFECTED TALL FESCUE SEED EXTRACT ON VASOACTIVITY OF BOVINE MESENTERIC VASCULATURE". UKnowledge, 2014. http://uknowledge.uky.edu/animalsci_etds/41.
Testo completoAbstract (sommario):
Endophyte-infected tall fescue produces many ergot alkaloids, which have been shown to be vasoconstrictive in various vessel types of bovine. On the other hand, substantial evidence has been reported on the vasodilative effects of formononetin and biochanin A in different vessel types in humans and rats. So, a study was conducted using mesenteric vasculature collected from heifers shortly after slaughter. After 2-h incubation with formononetin (F), biochanin A (B), or an ergovaline-containing tall fescue seed extract (EXT) and their combinations, vessels were mounted in a multi-myograph to determine their ergotamine-induced contractility. Results indicated that F and B at 1 × 10-6 M and their combination did not impact the contractile response to ergotamine in mesenteric vasculature. The pre-myograph incubation of mesenteric vasculature with EXT altered the contractile response manner to ergotamine. However, at higher concentration, F and B may alleviate the reduction of vasoconstriction caused by prior exposure to EXT. To our knowledge, this study was the first to investigate the interaction of ergot alkaloids and isoflavones on in vitro bovine mesenteric vasculature. However, further investigations are necessary to understand the mechanism behind the interaction of ergot alkaloids and isoflavones on vasoactivity.
42
Zylka, Christine A. "Composition and nutrient utilization by sheep of ensiled tall fescue with different levels of endophyte infection". Thesis, Virginia Polytechnic Institute and State University, 1989. http://hdl.handle.net/10919/52098.
Testo completoAbstract (sommario):
Low and high endophyte infected stockpiled tall fescue was harvested, chopped and ensiled in 210 liter metal drums, double lined with polyethylene bags. Endophyte infection averaged 4 and 70%, respectively, for the low- and high-endophyte fescue. A metabolism trial was conducted with 24 wethers fed diets consisting of 100% low-endophyte fescue silage, 50% low-endophyte and 50% high-endophyte fescue silage, and 100% high-endophyte fescue silage. Chopped alfalfa hay was used as a control forage. Single samples were analyzed, so statistical treatment of chemical composition was not possible. However, certain numerical differences were recorded. Lignin was higher for the high-endophyte than the low-endophyte fescue. Dry matter, CP, and ash were similar for the fescue silages. The high-endophyte fescue silage was lower in P, Mg, S, K, Fe, Cu, Mn, Zn, and Al than the low-endophyte silage. Digestibilities of DM, NDF, and cellulose were higher (P<.01) for fescue silages than alfalfa hay. Level of endophyte infection did not affect digestibility of DM, NDF or cellulose. Among silage treatments, apparent absorption of N, expressed as g/d, showed a linear effect (P<.05), with the lowest value obtained for sheep fed 100% high-endophyte fescue silage. Apparent absorption and retention of Ca were higher for silages than alfalfa. Among the silage diets, apparent absorption of P decreased linearly (P<.01) with increased endophyte level. Apparent absorption of K decreased linearly (P<.01) with increased endophyte level, but the effect was related to intake. Serum prolactin concentrations of the wethers fed fescue silage showed a linear decrease (P<.05) with increased proportion of endophyte-infected fescue. Endophyte infection of fescue appears to affect N and mineral metabolism.Master of Science
43
Hanneman, Jessica Marie. "EFFECTS OF ENDOPHYTE-INFECTED TALL FESCUE SEED AND BROMOCRIPTINE ON ENDOCRINE AND IMMUNE FUNCTION IN HORSES". UKnowledge, 2018. https://uknowledge.uky.edu/gluck_etds/38.
Testo completoAbstract (sommario):
Consumption of endophyte-infected (E+) grasses has long been associated with health problems in animals. In cattle E+ tall fescue consumption leads to fescue toxicosis, and in horses it leads reproductive problems. The health-related issues associated with endophyte consumption have been attributed to the effects caused by the ergot alkaloids produced by the fungus. These ergot alkaloids are considered D2-like receptor agonists, and 5-HT2 serotonin and α-adrenergic receptor partial agonists. Many studies in humans, swine, cattle, and horses have identified that ergopeptines cause a decrease in prolactin production due to their dopaminergic activities. Additionally, these molecules have been found to cause vasoconstriction in cattle and horses through their other agonistic activities. Furthermore, dopamine agonists are currently being used to treat pituitary pars intermedia dysfunction (PPID) in horses, a condition in which the horse lacks sufficient dopamine. However, the ergot alkaloids found in E+ tall fescue had not previously been investigated for their potential benefits in treating PPID horses. Moreover, little research has investigated the effects of ergot alkaloids and dopamine agonists on the immune system of horses, even though many health problems associated with E+ tall fescue consumption suggest there to be an elicited inflammatory response. Thus, the primary objective of this study was to establish an understanding of immune and hormone responses to ergot alkaloids and dopamine agonists in the horse. The hypothesis of this body of research was that ergot alkaloids and bromocriptine both would elicit inflammatory and hormone responses in the horse. Specifically, this research was conducted to determine the effects of E+ tall fescue seed consumption on immune, hormone, and vasoconstrictive responses, in both non-PPID and PPID horses. In addition, both the in vitro and in vivo effects of bromocriptine on cytokine production from equine peripheral blood mononuclear cells (PBMCs) were investigated. In the first study, there were no significant changes in body morphometrics, vasoconstriction, hormone responses or cytokine expression due to the consumption of ergot alkaloids in non-PPID and PPID horses. The second study was an in vitrostudy in which PBMCs were exposed to varying concentrations of either bromocriptine, a D2-like receptor agonist that is used as a model for ergot alkaloid consumption, or dopamine. This experiment demonstrated that exposure to dopamine or a dopamine agonist at a concentration greater than 10-5M is toxic to PBMCs, and that bromocriptine elicits an anti-inflammatory effect at concentrations less than 10-5M. Concentrations of dopamine less than 10-5M, on the other hand, did not cause any significant changes in cytokine expression. A third study was conducted that evaluated the effects of an intravenous injection of bromocriptine on hormone and immune responses in the aged mare. This study identified that bromocriptine maximally reduced prolactin levels 12 hours post-injection and prolactin returned to baseline levels approximately 56 hours post-injection. Additionally, only a significant increase in IL-1β was detected 12 hours post-injection, which suggests bromocriptine was activating an innate immune response. Overall, the body weights and rectal temperatures of horses did not significantly change in any of the experiments, which indicated that aged non-pregnant horses are able to tolerate E+ tall fescue. In addition, this body of research identified that intravenous delivery of a semi-synthetic dopamine agonist, bromocriptine, and not an oral delivery of an E+ tall fescue seed derived dopamine agonist, caused a decrease in prolactin concentrations, but revealed conflicting results regarding inflammatory responses. In summary, further research is warranted to determine the mechanism of action that dopamine agonists have on the immune system of horses.
44
Schwob, Guillaume. "Rôle écologique de la sporulation in-planta dans les symbioses actinorhiziennes : cas de la symbiose Alnus - Frankia". Thesis, Lyon, 2018. http://www.theses.fr/2018LYSE1037/document.
Testo completoAbstract (sommario):
Les patrons de distribution chez les micro-organismes reposeraient sur leurs capacités à disperser dans le temps et dans l'espace, en lien avec des facteurs abiotiques comme les propriétés du sol, le climat, et des interactions biotiques, notamment avec l'hôte dans le cas des symbiontes, mais aussi sur les traits d'histoire de vie propres aux micro-organismes, telle que la capacité à sporuler. Frankia sp. est une actinobactérie sporulante et fixatrice d'azote à la biogéographie complexe, car vivant à la fois de façon saprophytique dans le sol, en symbiose racinaire (nodosité) avec les plantes actinorhiziennes dont les aulnes (Alnus, Betulaceae). Deux types de souches de Frankia génétiquement différentes ont été décrites dont la distinction phénotypique majeure réside dans la capacité à maintenir (Sp+) ou non (Sp-) leur sporulation in planta. Cette sporulation endophytique est à notre connaissance unique dans un contexte symbiotique et son implication dans la biogéographie de Frankia, reste peu connue. Ces travaux de thèse intègrent à la fois des approches descriptives et expérimentales, sur le terrain et au laboratoire, afin d'accroître la compréhension du rôle écologique de la sporulation in planta de Frankia. Dans un premier temps, nous avons étendu la description de la phylobiogéographie des souches de Frankia Sp+ afin de tester la validité du patron de distribution centré sur les milieux froids des zones de haute altitude et de haute latitude de l'hémisphère nord. Un intérêt tout particulier a été porté sur les aires géographiques où une plus forte diversité de Frankia était attendue, dans la zone d'origine de l'aulne et ses refuges glaciaires. Dans un second temps, nous avons étudié l'influence du partenaire végétal dans la distribution observée des Frankia Sp+ et l'implication du trait Sp+ dans la capacité d'association à l'hôte. Des croisements expérimentaux ont été réalisés au laboratoire afin de découpler les effets de l'espèce-hôte et du climat, et tester les implications du trait Sp+ en termes d'infectivité, compétitivité et spectre d'hôte. Enfin, nous avons étudié les conséquences écosystémiques de l'expansion subalpine du complexe symbiotique Alnus/Frankia, au niveau de la diversité microbienne et du fonctionnement du cycle de l'azote, en fonction du phénotype de sporulation des souches associées. Des analyses pédologiques, en association avec des mesures de nitrification, dénitrification et fixation d'azote, ainsi que des analyses de diversité microbienne (globale et fonctionnelle), ont été réalisées dans différentes aulnaies Sp+, Sp- ou mixte, à différents stades de colonisation de l'aulne. Les résultats obtenus démontrent une prédominance des souches Sp+ associées aux espèces d'aulne des milieux froids sur les 3 continents de la zone Holarctique, avec une diversité nouvelle dans l'aire d'origine et les zones refuges de l'aulne. Les croisements effectués révèlent une infectivité et compétitivité plus forte des Sp+ par rapport aux Sp-. De plus, contrairement aux Sp- à spectre d'hôte très large, les Sp+ présentent un spectre limité entraînant des incompatibilités d'association suggérant une dépendance forte à une espèce-hôte donnée. Les modifications des communautés microbiennes du sol en réponse à l'expansion du complexe symbiotique Alnus/Frankia ont été démontrées, en lien avec la stimulation du cycle de l'azote dans les milieux sub-/alpins. Les premiers résultats sur l'efficience comparée de la fixation d'azote in natura des souches Sp- par rapport aux Sp+ suggèrent que 100% de l'azote de l'aulne est obtenu par le biais de la fixation. Aucun patron n'est mis en évidence entre souches Sp+ et Sp-, suggérant un effet plus complexe de la saisonnalité, de l'âge de l'arbre et de celui de la nodosité. Les résultats obtenus nous permettent de mieux appréhender les facteurs guidant la biogéographie de Frankia et de discuter de l'évolution de ces patrons de distribution en réponse au réchauffement climatiqueMicrobial biogeography would be based on the ability of microorganisms to disperse across time and space, as a function of abiotic factors such as soil properties, climate, and of biotic interactions, in particular with the host in the case of symbionts, but also on life history traits such as the ability to sporulate. Frankia sp. is a spore-forming and nitrogen-fixing actinobacterium that has a complex biogeography given its abilities for both saprophytic life and root symbiotic interaction with actinorhizal plants such as alders (Alnus, Betulaceae). Two distinct groups of Frankia lineages have been described according to a major phenotypic divergence, based on the presence (Sp+) or the absence (Sp-) of spores in planta.. To the best of our knowledge, this endophytic sporulation is an original trait in a symbiotic context and very little is known about its incidence in Frankia biogeography. This work integrates descriptive and experimental approaches on both field and laboratory areas, in order to improve the understanding of the ecological role of Frankia in planta sporulation. First, we have extended the description of the phylobiogeography of Sp+ Frankia strains to validate the previously proposed distribution pattern focused on cold environements at high altitude or high latitude. A phylogeny has been computed using a large number of nodular strains coming from the 3 continents of the Northern Hemisphere and 10 different Alnus species. Special attention was paid to geographic areas where a higher diversity was expected, in Asia, and in its glacial refuges. Second, we studied the influence of the host-plant on the distribution of Fankia Sp+ and the incidence of Sp+ in the symbiotic interaction. Experimental crosses have been performed to disentangle host and climate effects and to test the incidence of the Sp+ trait in terms of infectivity, competitiveness and host-range. Finally, we studied the ecological consequences of the Alnus/Frankia symbiotic complex, on the microbial diversity and on the nitrogen cycle functionning, with respect to the sporulation of Frankia and to the Alnus expansion on sub-/alpine grasslands. Soils analyses were performed in association with measures of nitrification and denitrification, as well as global and functional microbial diversity analyses, in Sp+, Sp- or mixed alder stands and at different colonization stages. In each part of this work, alder ectomycorhizae were analyzed to compare the distribution pattern between the two symbionts and to highlight potential interactions with the Sp+ trait of Frankia. Our results show the dominance of Sp+ strains in nodules of alder species from cold environments over the 3 continents of the Holarctic zone, with original diversity patterns in alder area of origin and in glacial refuges. Even if these strains are genetically homogenous, host-specific clusters were observed in the phylogeny. Crosses revealed that Sp+ strains were more infective and competitive than Sp- strains. Moreover, unlike Sp- strains that harbor a wide host-range, Sp+ strains have a narrower specificity leading to association’s incompatibilities and suggesting strong host dependence. For the first time, modifications of microbial communities were revealed in response to the Alnus-Frankia symbiotic complex colonization and were linked to a stimulation of the nitrogen cycle in the sub-/alpine grasslands. The first comparative results of nitrogen fixation between Sp+ and Sp- strains in natura suggest a maximal efficiency of fixation, representing almost 100% of the alder nitrogen. However, unlike previous reports in literature, no pattern was observed between Sp+ and Sp- strains, suggesting a complex effect of seasonality, alder age as well as that of nodules. Altogether, the previous results contribute to a better understanding of the Frankia biogeography drivers and allow us to discuss the expected evolution of distribution pattern in response to the global warming
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Rotz, Jonathan Daniel. "Comparison of techniques for estimating pasture herbage mass and productive ground cover for Lakota prairie grass, Kentucky 31 endophyte free tall fescue, Kentucky 31 endophyte infected tall fescue and Quantum 542 tall fescue grazed by stocker steers". Thesis, Virginia Tech, 2006. http://hdl.handle.net/10919/42188.
Testo completoAbstract (sommario):
In terms of acreage, forage is the number one crop in Virginia. The backbone of these forages has long been tall fescue (Lolium arundinaceum (Schreb.) S.J. Darbyshire). Knowledge of the plant species that make up a pasture and the relative amounts of each species present is important for interpreting potential animal performance. It is also important to know the relative amounts and types of weeds present and to monitor for the presence of poisonous plants or noxious weeds. An experiment was conducted in 2003 through 2005 to investigate botanical composition and yield of â Lakotaâ prairie grass (Bromus catharticus Vahl.), â Kentucky 31â endophyte-infected (KY31 E+), endophyte-free (KY31 E-), and â Quantumâ tall fescue (non toxic endophyte infected) under grazing by stocker steers. Forage botanical composition and yield were determined by clipping three 0.25-m2 areas per treatment replicate. Prior to harvesting, the canopy height within each quadrate was measured with a disc meter. In 2005, productive ground cover was assessed using visual evaluation techniques, point quadrat method, and digital imagery quantified with terrestrial remote sensing. Forages were established September 2002 and grazing was initiated in July of 2003. Experimental design was a randomized complete block with four replications. Averaged over the three years the yield of KY31E+ was higher (p<0.05) than all other treatments. Lakota prairie grass had lower (p<0.05) yields than both KY31 E+ and Quantum tall fescue, however no yields did not differ between Lakota prairie grass and KY31 E-. Our results showed a typical forage distribution curve for all the treatments. Early spring, summer, and fall productivity of Lakota prairie grass was less than all the fescues, thus did not extend the grazing season. Forage persistence was greatest for KY31 E+ and Quantum and lowest for Lakota when averaged over all years. Among sampling methods for ground cover, terrestrial remote sensing was the most accurate, compared with visual evaluation and point quadrat methods. For estimates of all yield indirect methods of assessment had high errors; however the plate meter calibrated by sward density seemed the least variable of the methods tested.Master of Science
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Kuntz, Veronica L. "The relationship between Sarracenia oreophila and an endophytic Burkholderia". Thesis, Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/41094.
Testo completoAbstract (sommario):
Plant growth-promoting bacteria (PGPB) have been studied in many agriculturally interesting plants, but never in pitcher plants.
Sarracenia oreophila (the green pitcher plant) is an endangered species in Georgia, Alabama, and North Carolina (Rice 2010). With the help of Dr. Jim Spain's lab, a previous student in Dr. Gerald Pullman's lab discovered evidence that nitrogen-fixing bacteria (Burkholderia spp.) live within these pitcher plants. This study aims to determine whether these nitrogen-fixing bacteria confer a benefit to their host plants by providing fixed nitrogen.
To do this, pitcher plants were inoculated with the Burkholderia and grown on a control medium, a medium without sugar (as the sugar causes the bacteria to grow until they hinder the plants), various media that are missing nitrogen-containing compounds usually provided in growth media, and a medium completely lacking nitrogen. These plants were compared to control plants on the same media that had not been inoculated with Burkholderia. The plants' biomass and root growth were measured.
The data suggest that Burkholderia may stimulate plant biomass growth when sufficient nitrogen is present and there may be a nitrogen-threshold that needs to be met in order to sustain the Burkholderia-Sarracenia symbiosis. Also, the Burkholderia has a negative effect on roots grown in high-nitrogen media, possibly due to competition for nutrients.
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Grancher, Denis. "Extraction, purification, toxicocinétique chez la chèvre et toxicologie clinique d'une toxine de champignon endophyte : le lolitrème B". Clermont-Ferrand 2, 2007. http://www.theses.fr/2007CLF21744.
Testo completoAbstract (sommario):
Le lolitrème B est une mycotoxine d'un champignon endophyte du genre Neotyphodium qui provoque des symptômes nerveux. L'objectif était de mesurer l'importance épidémiologique de cette intoxication et d'étudier son impact en santé publique vétérinaire (toxicocinétique, passage dans le lait). L'étude de cas cliniques a montré une relation entre la létalité et les teneurs relatives en lolitrème B et ergovaline. En France, les cas observés étaient dus à des pailles de Raygrass-semences. La toxicocinétique a nécessité l'extraction et la purification de lolitrème B. La chromatographie à contre courant couplée à la chromatographie en couche mince puis sur colonne, plus économe en solvants et plus rapide, a permis d'obtenir 28 mg de lolitrème B purifié à 96 %. La toxicocinétique chez la chèvre montre un passage de lolitrème B libre dans le lait de 3 % en 32 h après une injection intraveineuse, de 0,19 % en 75 h après administration intraruminale. Le risque en santé publique est négligeable
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MICELI, Elisangela. "Bacterial Endophytes: Unexplored Sources Of Biotechnologically Relevant Molecules". Doctoral thesis, Università degli studi di Ferrara, 2019. http://hdl.handle.net/11392/2488023.
Testo completoAbstract (sommario):
Endophytes are microorganisms which colonize the internal tissues of the plants without causing any harm. Generally, endophytes are described as presenting beneficial functions to the plant host, such as plant growth promoting activity and protection against pathogens. The interaction between endophytes and plants is so close, that the term holobiont has been proposed to define the plant and its microbiome, as if they formed a unique organism. In the last decades, endophytes have gained more attention since there is growing evidence of their capacity to influence the plant’s physiology and to produce bioactive compounds. For example, it has been suggested that endophytes could synthesize compounds similar to the ones produced by the plant host, and modulate the production of plants secondary metabolites. In this context, endophytes appear as a powerful tool. On one hand, the exploration of endophytes allows to deepen our knowledge on the plant-microbiome interaction; on the other hand, the better comprehension of the holobiont can lead to a biotechnological application of endophytes.
Thus, we decided to explore bacterial endophytes from different plants, to better comprehend the structure of their communities, to explore their phenotypic features, prospecting a possible biotechnological application.
In this work, we have analyzed bacterial endophytes from medicinal plants tissues and seeds, and hyperaccumulator plants.
Bacterial communities associated to the medicinal plants Echinacea purpurea and E. angustifolia were already described in our laboratory and showed very specific communities in association to different tissues of the plants (stem/leaves, roots) and rhizosphere. Then, we decided to furtherly explore such communities, mainly focusing on the possible forces that could determine the presence of different communities in different districts of the plants. The performed analysis indicated that bacterial strains themselves could be implied in determining the structure of their own community by means of antimicrobial production, which in turn determine the colonization by adaptive phenotypes.
Endophytes exhibiting intriguing phenotypes, such as the inhibition of human opportunistic pathogens, were furtherly analyzed, by determining their genome sequences. The analysis of such sequences showed that the endophytic strains harbor many gene cluster which might be implied in inhibitory activities, confirming that endophytic bacterial strains are a promising field to investigate.
Endophytic bacterial strains were also analyzed within E. purpurea seeds. In this case, endophytes were observed within the plant’s seeds, extracted, taxonomically and phenotypically characterized.
More recently, we decided to explore endophytes which live in association with Phragmites australis plants, which are largely used in phytodepuration constructed wetlands. This part of the work was possible thanks to the collaboration with G.I.D.A. S.p.A., Gestione Impianti Depurazione Acque. The characterization of such endophytes has shown that they are able to grow in presence of critical elements for wastewater treatment, suggesting their possible application to obtain an enhancement of phytodepuration efficiency.
Overall, the analyses performed in this work increased our knowledge on bacterial endophytes from different sources, their communities structure, and interaction with the host. As a consequence, it represents the starting point to a possible biotechnological application of endophytes, in order to address issues, such as antibiotic resistance and environmental cleanup.Gli endofiti sono microrganismi che colonizzano i tessuti interni delle piante senza causare nessun danno. Generalmente, gli endofiti sono in grado di compiere funzioni come la promozione della crescita della pianta e la protezione contro patogeni. Il termine olobionte indica l’insieme costituito dalla pianta e dal suo microbiota, come se questi costituissero un unico grande organismo. Nelle ultime decadi, gli endofiti sono stati sempre più studiati, poiché è diventata sempre più evidente la loro capacità di influenzare la fisiologia della pianta e la produzione di molecole bioattive. Per esempio, è stato proposto che gli endofiti possono sintetizzare composti simili a quelli sintetizzati dalla pianta ospite e che possono modulare la produzione dei metaboliti secondari della pianta. In questo contesto, gli endofiti appaiono come strumenti di grande potenziale in campo biotecnologico. Per questi motivi, abbiamo deciso di analizzare batteri endofiti da piante diverse, allo scopo di capire meglio la struttura delle loro comunità e di esplorare le loro caratteristiche fenotipiche, prospettando così una possibile applicazione in campo biotecnologico. In questo lavoro, sono state analizzati batteri endofiti da piante medicinali, da semi di piante medicinali e da piante iperaccumulatrici di sostanze tossiche. Recentemente, comunità batteriche associate alle piante medicinali Echinacea purpurea and E. angustifolia sono state analizzate nel nostro laboratorio e hanno mostrato una struttura e composizione molto specifica nei vari tessuti delle piante (foglie/stelo, radici) e nella rizosfera. Successivamente, abbiamo deciso di studiare in modo più approfondito tali comunità, concentrandoci soprattutto nei fattori che potrebbero determinare la presenza di comunità così specifiche in diversi compartimenti delle piante. Le analisi effettuate hanno mostrato che le comunità batteriche stesse potrebbero prendere parte nella strutturazione delle proprie comunità, attraverso la produzione di molecule antimicrobiche, che determinano a loro volta la colonizzazione da parte di ceppi resistenti. Inoltre, alcuni ceppi batterici estratti da Echinacea purpurea e E. angustifolia sono stati ulteriormente analizzati dal punto di vista genetico, attraverso il sequenziamento dei loro genomi. Lo studio delle sequenze ha mostrato che i ceppi endofiti presentano diversi cluster genici presumibilmente coinvolti in attività antibiotica, confermando che tali ceppi potrebbero trovare un’applicazione in campo biotecnologico. Ceppi batterici endofiti sono stati analizzati anche all’interno di semi di E. purpurea. In questo caso, oltre ad osservare la presenza di endofiti all’interno dei semi, endofiti batterici sono stati estratti dai semi e caratterizzati dal punto di vista tassonomico e fenotipico. Recentemente, la nostra analisi degli endofiti si è estesa verso le piante iperaccumulatrici. Sono stati analizzati batteri endofiti in associazione alle piante di Phragmites australis, largamente utilizzate in impianti di fitodepurazione. Questa parte del lavoro è stata possibile grazie alla collaborazione con G.I.D.A. S.p.A, Gestione Impianti Depurazione Acque. La caratterizzazione di tali endofiti ha evidenziato la loro capacità di crescita in presenza di elementi, quali ferro, boro e selenio, che sono critici nel processo di depurazione delle acque. Queste evidenze rendono possibile ipotizzare l’applicazione di tali ceppi per un incremento dell’efficienza depurativa. In conclusione, le analisi effettuate in questo lavoro di tesi hanno permesso di appronfondire le nostre conoscenze riguardo batteri endofiti provenienti da diverse fonti. Questo lavoro rappresenta, inoltre, il punto d’inizio per un possibile utilizzo di tali batteri in campo biotecnologico, al fine di rispondere a precise richieste, quali la resistenza agli antibiotici e la necessità di diminuire l’inquinamento ambientale.
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Saliba, Sahar. "Nouvelles approches biotechnologiques pour l’obtention d’alcaloïdes : culture in vitro de Leucojum aestivum L. et isolement d’endophytes bactériens d’Amaryllidaceae". Thesis, Université de Lorraine, 2015. http://www.theses.fr/2015LORR0107/document.
Testo completoAbstract (sommario):
Plus de 300 alcaloïdes d’Amaryllidaceae doués d’activités biologiques ont été isolés à partir des plantes appartenant à cette famille. De nos jours, seule la galanthamine, utilisée pour le traitement palliatif de la maladie d’Alzheimer, est commercialisée. L’accumulation de ces alcaloïdes dans les plantes est limitée. La culture in vitro est une méthode alternative intéressante pour l’obtention plus aisée de ces alcaloïdes à haute valeur ajoutée. Le premier objectif de ce travail vise à développer une méthode de purification efficace, simple et rapide des extraits de plantes préalablement à leur analyse en LCMS et GCMS. Le second objectif est d’étudier l’effet de plusieurs facteurs exogènes, ajoutés au milieu de culture de bulbilles de Leucojum aestivum et de sa variété Gravety Giant en bioréacteurs RITA®, sur les voies de biosynthèse de la galanthamine et de la lycorine. La variation des paramètres exogènes a permis une accumulation accrue en galanthamine et en lycorine (0,814 mg/g et 1,54 mg/g de matière sèche respectivement) dans les bulbilles. Le troisième objectif porte sur l’isolement et l’identification d’endophytes à partir de bulbes in vivo et in vitro de trois espèces d’Amaryllidaceae (L. aestivum, Narcissus pseudonarcissus et Galanthus elwesii). Des bactéries endophytes du genre Bacillus ont été identifiées. Un nouvel alcaloïde a été isolé à partir des cultures bactériennesOver 300 Amaryllidaceae alkaloids possessing a wide range of biological activities have been isolated from plants belonging to this family. Galanthamine, used for the palliative treatment of Alzheimer’s disease, is the only one commercialized. The biodisponiblity of these alkaloids is low. In vitro culture offers an alternative yet interesting approach for the biotechnological production of these valuable alkaloids. The aim of this work was, first, to develop a fast, efficient and easy purification method of plant extracts prior to their phytochemical analysis both in LCMS and GCMS. Second, the combined effects of bioreactor RITA® culture and feeding with different exogenous factors on the biosynthetic pathway of both galanthamine and lycorine were studied. The experiments were conducted both with Leucojum aestivum and L. aestivum ‘Gravety Giant’ bulblets. The variation of several exogenous parameters resulted in a better accumulation of galanthamine and lycorine (0.814 mg/g and 1.54 mg/g dry weight respectively) in the bulblets. The third aim was to isolate and identify alkaloid producing endophytes from in vivo and in vitro bulbs of three Amaryllidaceae species (L. aestivum, Narcissus pseudonarcissus and Galanthus elwesii). Bacterial endophtes belonging to the Bacillus genus were identified. A new alkaloid was isolated from bacterial liquid cultures
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Florea, Simona. "TOWARDS ELIMINATION AND GENETIC MANIPULATION OF ERGOT ALKALOID PRODUCTION IN FUNGAL ENDOPHYTES". UKnowledge, 2009. http://uknowledge.uky.edu/gradschool_diss/803.
Testo completoAbstract (sommario):
Clavicipitaceous fungal endophytes provide several ecological benefits to their hosts. Besides improving host’s growth characteristics, Neotyphodium coenophialum, the endophyte of tall fescue (Lolium arundinaceum), produces ergot alkaloids that have been proposed to be involved in fescue toxicosis. One approach to address the toxicosis problem is to genetically manipulate and modify N. coenophialum by knocking out a pair of homologous genes, (dmaW1 and dmaW2), encoding dimethylallyltryptophan synthase, the enzyme for the first and determinant step in ergot-alkaloid biosynthesis. In this study, disruption of dmaW2 was attempted using several disruption methods. Out of 1522 transformants screened, three putative knockouts were identified. Southern blot analysis of digested genomic DNA indicated that homologous gene replacement at dmaW2 locus took place while dmaW1 was still present. Chromosome separation followed by Southern-blot hybridization showed that the dmaW genes in N. coenophialum are located on different chromosomes.
The aim of this study was to obtain a nontoxic endophyte free of marker genes that could be used to inoculate popular tall fescue cultivars. Therefore the Cre/loxP system developed in this study allows reusing the marker gene for sequential transformations. Protoplasts from Neotyphodium coenophialum, Neotyphodium uncinatum, or Epichloë festucae isolates, containing a floxed hygromycin phosphotransferase (hph) gene (loxP::hph::loxP), were transfected with a Crerecombinase expression plasmid and then cultured without selection. The marker was excised in 0.5-2% of the colonies, leaving a single loxP sequence. This strategy will help to reduce the concerns related to field release or commercialization of economically important grasses associated with manipulated fungal strains. It is expected that the technology will likely be adapted and applied in other fungal species.
Manipulation of the ergot alkaloid (EA) gene cluster from C. purpurea and C. fusiformis by introducing and expressing its genes in different fungal-grass symbionts was also investigated.
Heterologous expression of the ergot alkaloid cluster could result either in the synthesis of compounds similar to the ones produced by the host or in synthesis of novel compounds with new modes of action. Even though the results indicated that several EA genes were expressed in the new symbiota, none of the ergot alkaloids intermediates were detected.