Dissertations / Theses on the topic 'Nodulation'
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1
Guan, Dian. "Rhizobial infection in nodulation." Thesis, University of East Anglia, 2012. https://ueaeprints.uea.ac.uk/42403/.
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Nodulation is a symbiosis between plants and bacteria called rhizobia which leads to the formation of a lateral organ called a nodule where nitrogen fixation occurs. Nodulation can be divided into two developmental programmes, rhizobial infection, and nodule organogenesis, both of which are required for nitrogen fixation. In my PhD studies, I focused on the study of rhizobial infection using the Medicago truncatula-Sinorhizobium meliloti model system. NIN is an important transcription factor in the nodulation signalling pathway that functions both in rhizobial infection and nodule organogenesis. Gene expression profiling of nin during rhizobial infection has enabled me to identify its potential downstream targets including several NIN-dependent infection-related genes and, surprisingly, genes involved in mycorrhization that are apparently repressed by NIN. The identification of these genes has provided insight into how NIN functions in rhizobial infection and revealed potential cross-talk between nodulation and mycorrhization pathways. In the course of this work I discovered two infection mutants. One of the mutants, cbs1, was cloned in collaboration with a colleague in the lab. It encodes a Cystathionine Beta-Synthase domain containing protein with a potential role in reactive oxygen species homeostasis. The other mutant, which I named knocks but can’t enter (kce), is blocked at an early stage of infection. I used conventional mapping and next-generation sequencing technologies to genetically map kce to a known rhizobial infection gene LIN. The kce mutant developed nodules with central rather than peripheral vascular bundles resembling nodules from the more ancient Frankia-actinorhizal symbiosis. Using kce and other infection mutants I demonstrate that this abnormal nodule architecture results from a failure of infection to reach the nodule cortex. Based on this finding, I predict that Nod factor activated signalling in the nodule cortex plays a role in determining nodule structure.
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Stokkermans, Thomas Jan Willem. "Bradyrhizobium elkanii signals in nodulation /." The Ohio State University, 1994. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487849696964735.
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Buzas, Diana M. "Molecular genetic analysis of legume nodulation /." [St. Lucia, Qld.], 2005. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe19380.pdf.
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Miwa, Hiroki. "Calcium signalling in nodulation and mycorrhization." Thesis, University of East Anglia, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.423392.
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Hogg, Bridget V. "Competitive nodulation blocking in cv. Afghanistan pea." Thesis, University of East Anglia, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.365074.
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Alazard, Didier. "La nodulation caulinaire dans le genre Aeschynomène." Lyon 1, 1991. http://www.theses.fr/1991LYO10080.
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Plusieurs especes de legumineuses tropicales appartenant au genre aeschynomene portent des nodules fixateurs d'azote a la fois sur leurs racines et sur leur tige. Ces especes peuvent etre classees en trois groupes d'inoculation croisee. L'infection de la tige d'a. Afraspera a lieu au niveau de sites de nodulation predetermines selon un processus d'infection directement intracellulaire qui ne fait intervenir ni poils absorbants, ni cordons d'infection. La plupart des rhizobia isoles des nodules caulinaires sont capables de fixer l'azote moleculaire en cultures pures. L'etude taxonomique de ces rhizobia a permis de les classer dans le genre bradyrhizobium. Sur le plan des applications agronomiques, les potentialites de fixation d'azote considerables de ces plantes permettent leur utilisation comme engrais vert en riziculture irriguee. Les rendements en riz ont pu etre doubles dans des essais en microparcelles. De plus, la fixation d'azote par les nodules caulinaires n'est pas inhibee par l'azote combine du sol
7
Gresshoff, Peter M. "Plant genetic control of nodulation in legumes." Thesis, Canberra, ACT : The Australian National University, 1988. http://hdl.handle.net/1885/140284.
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8
Kim, Sung-Yong Stacey Gary. "Extracellular ATP, apyrase and nodulation of non-legumes." Diss., Columbia, Mo. : University of Missouri--Columbia, 2008. http://hdl.handle.net/10355/7189.
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Title from PDF of title page (University of Missouri--Columbia, viewed on February 24, 2010). The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file; a non-technical public abstract appears in the public.pdf file. Dissertation advisor: Dr. Gary Stacey. Vita. Includes bibliographical references.
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Sista, Prakash Rao. "Characterization of nodulation defective mutants of Bradyrhizobium japonicum." Thesis, McGill University, 1987. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=75665.
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The Rhizobium-legume symbiosis is an opportunistic association between two symbiotic partners that results in the formation of the root nodule. The process depends on the expression of a number of plant and bacterial genes that are considered critical for the establishment and maintainance of the symbiotic state. The merits of a mutational approach to the analysis of symbiosis have been recognized for several years and transposon Tn5 mutagenesis of Rhizobium has led to the identification of several symbiotic genes. This study describes the use of Tn5 mutagenesis for the isolation of symbiotically defective mutants of Bradyrhizobium japonicum. Two classes, auxotrophic and cell surface-altered mutants defective in nodule formation, have been characterized. In B. japonicum USDA 122, histidine auxotrophs that are defective in nodulation have been studied. The mutagenized DNA region has been cloned and the wild-type DNA region isolated by hybridization and complementation. In B. japonicum 61A76, Tn5-induced cell surface-altered mutants have been isolated by selecting for bacteriophage resistance. Several parameters have been used to demonstrate alterations in cell surface components. It has been shown that the Tn5 insertion is not the primary cause of the mutation in two of the characterized mutants. Complementation tests have led to the isolation of a wild-type DNA-containing cosmid, pPS23A, that overcomes the symbiotic defect in one of the mutants. Analysis of the cell surface showed a partial restoration of surface components in the complemented mutant.
10
Clark, Sonya A. "Herbicide effects on white clover growth and nodulation." Thesis, University of Canterbury. Microbiology, 1987. http://hdl.handle.net/10092/6909.
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Five herbicides commonly used for suppression of weed growth in white clover seed crops were tested for toxicity against white clover (Trifolium repens), Rhizobium trifolii and the nitrogen fixing symbiosis formed between these two organisms. Trials were carried out on R.trifolii on solid and in liquid media to determine if growth of this bacterium was affected by the presence of the 5 herbicides. Paraquat and MCPB substantially inhibited bacterial growth on solid medium. Bentazone, fusilade and kerb caused very small zones of growth inhibition of R.trifolii on solid agar at high concentrations. None of the herbicides tested affected growth of R.trifolii in liquid culture.
In vitro studies of herbicide toxicity toward white clover were carried out to identify interactions of herbicide activity with rhizobial inoculation and supplied nitrogen, and to attempt to identify the targets of herbicide activity. Nodules grown under in vitro conditions were excised and used for ultrastructural examination.
Herbicides were applied to plants grown in vitro at two different stages of plant growth. White clover proved to be very sensitive to all herbicides at the early seedling stage. Three week old plants were more tolerant.
Pot experiments in a glasshouse environment indicated the relevance of in vitro experiments of herbicide toxicity against plants and gave information on the effect of soil water levels on herbicide activity.
Paraquat was extremely toxic to white clover both in vitro and in pot experiments. Nodulation is affected to some extent directly by this herbicide although dessication of foliage probably has some role in halting activity of the nitrogenise enzyme. MCPB caused severe deformation of root tissue both in vitro and in pot experiments. It must be either contaminated with the active form of this herbicide, MCPA, or is being broken down to the active form by bacterial or chemical action. Bentazone did not damage white clover or nodule activity in a consistent way in vitro. However this herbicide did have a deleterious effect on both plant weight and nodulation when applied to white clover grown in soil, particularly under conditions of low soil moisture. Fusilade showed a direct effect on the activity of nitrogenase in vitro. Fusilade also acted more severely against plants of higher nutritional status, and appeared to affect nodule activity directly rather than affecting nodules via damage to other plant parts. Kerb was very toxic to seedling white clover in vitro although older plants were not as susceptible and were stimulated by high concentration of kerb. In pots white clover was slightly inhibited by kerb at recommended concentration while 10 x this concentration did not cause any inhibition of nodulation or plant growth.
Differences in results between in vitro and pot studies of toxicity of these herbicides to white clover appear to be due to the different application methods used. In vitro herbicides were applied to the whole plant while in pot experiments herbicides were foliarly applied, hence more uptake by roots would be expected.
Pot experiments indicated that changes in nodulation generally reflected changes in plant growth rather than an independent activity of the herbicide on nodulation.
11
CHARON, CELINE. "Action du gene enod40 lors de la nodulation." Paris 11, 1999. http://www.theses.fr/1999PA112174.
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La symbiose qui s'etablit entre les legumineuses et les rhizobia conduit au developpement d'un nouvel organe racinaire, la nodosite, dont la morphogenese necessite l'expression de genes vegetaux specifiques. Le gene enod40 s'exprime dans les cellules corticales en division des l'initiation du primordium nodulaire et code pour un arn a petites orf. Ce travail de these contribue a l'analyse de l'action du gene enod40 lors de la nodulation. Nous avons montre qu'en situation de carence azotee et en absence de rhizobia, la surexpression d'enod40 induisait la dedifferenciation et la division des cellules du cortex racinaire. De plus, les plantes transgeniques m. Truncatula surexprimant enod40 ont presente, lors de leur interaction avec les bacteries rhizobia, une acceleration de leur cinetique de nodulation, et lors de leur interaction avec le champignon glomus mosseae, un nombre accru de mycorhizes. L'analyse de deux lignees transgeniques presentant de la cosuppression a montre une correlation entre la non-expression d'enod40 et une reduction du nombre de nodosites par plante ainsi qu'une perturbation de leur developpement. Nous avons aussi cherche a determiner la forme moleculaire du produit du gene et a analyser les mecanismes moleculaires mis en jeu lors de son action. Par microbombardement et par fusions traductionnelles, nous avons montre que l'arn enod40 possedait au moins 2 regions biologiquement actives. L'activite de la region 5 de l'arn enod40 serait liee a la traduction d'une petite orf de 13 acides aminees, tandis que l'activite de la region 3 serait liee a la traduction d'une autre orf de 27 acides aminees chez m. Truncatula. Enod40 participerait donc au controle de la formation et de la differenciation des organes symbiotiques au sein du cortex racinaire. Il ferait partie d'une nouvelle classe de regulateurs de croissance chez les plantes. La caracterisation d'un tel gene ouvre de nouvelles perspectives sur la signalisation chez les vegetaux.
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Donaldson, Pauline A. (Pauline Alison) Carleton University Dissertation Biology. "Nodulation and tumorgenesis by Agrobacterium carrying Rhizobium plasmids." Ottawa, 1985.
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13
Hayashi, Satomi. "Molecular characterisation of early nodulation events in soybean." Thesis, The University of Queensland, 2014.
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Legumes include some of the most economically important crops and are characterised by their ability to form a symbiotic relationship with nitrogen fixing rhizobia bacteria. Effective legume-rhizobia symbioses result in the formation of a wart-like structure on the root called the nodule. In this nodule, the rhizobia provide nitrogen to the host plant in exchange for energy and shelter. Nodulation is induced by the recognition of a rhizobia derived, strain specific signal, called Nod factor. Recognition of Nod factor from compatible rhizobia leads to complex signalling within and between the epidermis and the cortical cells of the root. Concomitantly, the rhizobia infect the young root hair cells, which are strictly located on the part of the root where the root hairs emerge, a region called the Zone Of Nodulation (ZON). Only when the plant’s Nod factor signalling and the rhizobia infection event in the ZON are in complete synchronicity, do nodules form.
Nodulation research in the last few decades has identified a large number of genes associated with, or required for, the formation and development of nodules. These genes today form the foundation of our understanding of the early nodulation signalling pathway. However, there are a number of novel nodulation signalling components still to be discovered, which may hold the key to the missing links in our current knowledge on this signalling pathway.
The work reported in this thesis aimed to identify novel components of the early nodulation signalling pathway using modern RNA-seq technology. Approximately 3,000 genes were identified as differentially regulated between roots inoculated with compatible, or a Nod factor-deficient mutant, rhizobia (nodC-). Targeting only the ZON to isolate the transcriptome allowed for the identification of genes having little and/or transient expression in the ZON, which would otherwise have been masked by other dominating transcripts. Gene ontology analysis identified both individual genes and molecular pathways that are likely regulated during early nodulation. Detailed expression analysis of selected candidate genes revealed that some of these genes, including two gibberellin (GA) biosynthesis genes and a TIR-NBS-LRR encoding a putative resistance gene, are specifically expressed in tissue responding to compatible rhizobia inoculation (ZON and nodules).
Previous studies utilising mutant and pharmacological analyses have indicated that GA plays an important role in nodule development. However, its precise action, including the location and timing in which GA acts during nodulation, is yet to be determined. To better understand the role of GA in nodulation, follow up studies were conducted for two candidate GA biosynthesis genes identified here, GmGA20ox a and GmGA3ox 1a. Histochemical analysis revealed cell-type specific activation of the GmGA20ox a promoter during nodulation, which changed in localisation at different stages of nodule organogenesis. However, silencing of this gene had no effect on nodule number or appearance.
Similarly, follow-up studies were conducted for the TIR-NBS-LRR coding gene, GmTIR-NBS-LRR. Unlike many TIR-NBS-LRR genes which are associated with pathogen-related effector molecule perception, this gene was up-regulated by the symbiotic bacteria, specifically in response to rhizobia-derived Nod factor. Silencing and over-expression of GmTIR-NBS-LRR both resulted in reduced, although not significantly, nodule numbers. However, the complex regulation of the TIR-NBS-LRR gene family makes the interpretation of these results difficult.
Based on recent findings, including those reported in this thesis, updated models and predictions relating to the early nodulation pathway are presented and discussed. This includes outlining potential role(s) for the candidate genes identified here in the ZON transcriptome. The mechanistic action of GA and the TIR-NBS-LRR candidate as they relate to nodule formation are also discussed.
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Gautrat, Pierre. "Régulation de la nodulation symbiotique fixatrice d’azote par des peptides de signalisation chez Medicago truncatula Compact Root Architecture 2 Promotes Root Competence for Nodulation through the miR2111 Systemic Effector Independent Regulation of Symbiotic Nodulation by the SUNN Negative and CRA2 Positive Systemic Pathways Unraveling new molecular players involved in the autoregulation of nodulation in Medicago truncatula." Thesis, université Paris-Saclay, 2020. http://www.theses.fr/2020UPASB033.
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Les plantes bénéficient d’une plasticité développementale assurée par des zones méristématiques actives tout au long de leur cycle de vie afin de s’adapter aux contraintes environnementales. Les parties aériennes et les racines sont chacune soumises à des stimuli environnementaux indépendants qui doivent être intégrés au niveau de la plante entière afin d’assurer une coordination du développement de ces différents organes, impliquant des échanges de signaux à longue distance, dits systémiques. Chez les légumineuses, le système racinaire est non seulement capable de se ramifier en racines latérales, mais est aussi capable de former de nouveaux organes, les nodules fixateurs d’azote atmosphérique, grâce à une symbiose avec des bactéries, appelées rhizobia, lorsque le sol est pauvre en azote minéral. La formation et le maintien de ces nodules sont cependant couteux en énergie et doivent donc être strictement régulés par la plante via des signalisations hormonales afin d’inhiber ou de favoriser la nodulation selon ses besoins. Des hormones peptidiques de la famille CLE (« Clavata3 (CLV3)/Embryo Surrounding Region ») et CEP (« C-terminally Encoded Peptide »), produites dans les racines, ont notamment été identifiées comme jouant respectivement un rôle systémique négatif ou positif sur la nodulation, de manière dépendante des récepteurs SUNN (« Super Numeric Nodules ») et CRA2 (« Compact Root Architecture 2 ») dans les parties aériennes, respectivement. La problématique de cette thèse était donc de comprendre comment des peptides de signalisation régulent à la fois localement et systémiquement la nodulation. A cette fin, deux objectifs ont été définis : 1) identifier des mécanismes moléculaires associés aux voies de signalisation systémiques CLE/SUNN et CEP/CRA2 régulant la nodulation ; 2) caractériser de nouveaux peptides CLE régulant la nodulation. Dans un premier temps, j’ai participé à démontrer que les voies systémiques CLE/SUNN et CEP/CRA2 agissent indépendamment pour réguler de manière antagoniste la nodulation. Dans un second temps, des acteurs racinaires en aval de la voie CLE/SUNN ont été identifiés, révélant un lien avec les récepteurs des molécules signales des rhizobia, les NFs (« Nod Factors »), ainsi qu’avec des protéines à « F-box » nommées TML1 (« Too Much Love 1 ») et TML2, et un rôle négatif de ces protéines TML sur la nodulation a pu être caractérisé. Enfin, un acteur commun agissant en aval des voies CLE/SUNN et CEP/CRA2 a été identifié : le miR2111. Ce microARN produit dans les parties aériennes est régulé de manière opposée par les deux voies systémiques, et clive les transcrits des gènes TMLs dans les racines, contrôlant ainsi le nombre de nodules formés en fonction de la disponibilité en azote et de la préexistence de nodules. Le deuxième objectif de thèse a permis de révéler l’existence d’un peptide CLE dont l’expression est induite dans l’épiderme racinaire en conditions symbiotiques, CLE37. Ce gène code pour un peptide TDIF (« Tracheary Element Differentiation Inhibitory Factor »), et des approches par ARN interférence et de mutagénèse ont révélé que ce gène est requis pour moduler la croissance racinaire en réponse aux rhizobia, inhibant la croissance des racines principales et augmentant le diamètre racinaire. Ainsi, le recrutement de ce peptide de signalisation pourrait permettre d’accommoder le développement racinaire pour soutenir les besoins de la symbiose fixatrice d’azoteAs sessile organisms, plants benefit of a high developmental plasticity through the maintenance of active meristems during their whole life cycle to adapt to environmental constraints. Shoots and roots are subjected to independent environmental stimuli that must be integrated at the whole plant level to coordinate growth and development of these different organs, implying the existence of endogenous systemic (long-distance) signals. Legume plants besides forming lateral roots, are also able to form new root organs, the nitrogen-fixing nodules, thanks to a symbiotic interaction with bacteria called rhizobia when mineral nitrogen availability is limited in the soil. However, formation and maintenance of nodules is energetically costly and must be tightly controlled by the host plant through hormonal signalling pathways in order to inhibit or to promote nodulation depending on its needs. Peptide hormones from the CLE (Clavata3 (CLV3)/Embryo Surrounding Region) and CEP (C-terminally Encoded Peptide) families, produced in roots, were notably identified as regulating systemically nodulation, respectively negatively and positively, depending on the SUNN (Super Numeric Nodules) and CRA2 (Compact Root Architecture 2) receptors in shoots, respectively. The problematic of this Ph.D. thesis was therefore to investigate how signalling peptides regulate nodulation locally and systemically. To this end, two objectives were defined: 1) to identify molecular mechanisms linked to the CLE/SUNN and CEP/CRA2 systemic pathways; 2) to characterize new CLE peptides regulating nodulation. First, I participated in demonstrating that the CLE/SUNN and CEP/CRA2 systemic pathways act independently to regulate antagonistically nodulation. Then, molecular effectors acting in roots downstream of the CLE/SUNN pathway were identified, revealing a link with NFs (Nod Factors) receptors and with F-box proteins called TML1 (Too Much Love 1) and TML2, and both TML proteins were shown to regulate negatively nodulation. Finally, a shared downstream actor of the CLE/SUNN and CEP/CRA2 pathway was identified: the miR2111. This microRNA, produced in shoots, is regulated antagonistically by the two systemic pathways, and cleaves TML transcripts in roots, therefore controlling nodule number depending on nitrogen and rhizobial cues. The second Ph.D. thesis objective allowed highlighting a CLE peptide which expression is induced in the root epidermis by symbiotic conditions: CLE37. This gene encodes a TDIF (Tracheary Element Differentiation Inhibitory Factor) peptide, and RNA silencing as well as mutagenesis approaches revealed that it is required to modulate root development in response to rhizobia, inhibiting primary root growth and enhancing stele root diameter. The recruitment of the CLE37 signalling peptide could thus allow accommodating root development to support symbiotic nitrogen fixation needs
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Loureiro, Morais Latino. "Synthèse de thiooligosaccharides, précurseurs d'analogues de facteurs de nodulation." Phd thesis, Université Blaise Pascal - Clermont-Ferrand II, 2004. http://tel.archives-ouvertes.fr/tel-00662408.
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Nous avons réalisé la synthèse de précurseurs d'analogues sulfures de facteurs NOD, messagers chimiques intervenant lors du phénomène de nodulation rencontré dans l'association symbiotique entre certaines plantes légumineuses et des bactéries de la famille rhizobium. Cette association permet à la plante de fixer l'azote atmosphérique préalablement métabolisé par les bactéries. Ces analogues devraient permettre de mieux comprendre les différents processus intervenant au cours de la symbiose plante/ bactérie ainsi qu'étudier l'hydrolyse des facteurs NOD par des enzymes, les chitinases. Nous avons choisi de préparer des analogues fonctionnalisés pour lersquels seule la liaison O-glycosidique entre deux unités serait remplacée par une liaison thioglycosidique. Grâce à l'utilisation de donneurs de glycosyle sous la forme de trichloroacétimidate, nous avons réalisé la synthèse d'un thiotrisaccharide ainsi que celle d'un thiotétrasaccharide, précurseur d'analogues de facteurs NOD, dont les unités réductrices et non réductrices sont potentiellement différenciées en vue de leur fonctionnalisation. Par ailleurs, le transfert d'une unité de glucosamine sur un thiodisaccharide, à l'aide de la bétâ-1,4-galactosyltranférase, a conduit à la préparation d'un thiotrisaccharide. Cette dernière étape a permis d'envisager la synthèse d'un thiotétrasaccharide par voie chimio-enzymatique. Ces précurseurs devraient conduire à de nouveaux analogues sulfures de facteurs NOD sur lesquels des tests biologiques pourraient être réalisés afin d'évaluer l'activité de nodulation ainsi que la résistance aux chitinases
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Rossen, L. "Molecular analysis of the nodulation genes of Rhizobium leguminosarum." Thesis, University of East Anglia, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.370396.
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Dean, Gregory. "Analysis of NodO : a secreted protein involved in nodulation." Thesis, University of East Anglia, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.361482.
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Riva-Grenouillat, Nathalie. "Synthèse d'analogues bioactifs de facteurs de nodulation des légumineuses." Paris 11, 2001. http://www.theses.fr/2001PA112237.
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Afin de mieux comprendre le mécanisme de reconnaissance des facteurs de nodulation par les légumineuses, événement déclencheur du processus de fixation de l’azote, une série d’analogues des facteurs de nodulation associés à la luzerne et à la vesce a été préparée. Ces analogues sont préparés en utilisant une méthode chimioenzymatique, qui consiste à produire le squelette oligosaccharidique par des cellules E. Coli recombinantes et à venir fixer la chaîne lipidique par voie chimique. Dans un premier temps, des analogues non hydrolysables par les amidases du sol ont été synthétisés en remplaçant la fonction amide par une fonction amine. Les produits présentent une activité en nodulation, laissant penser qu'il ne se produit pas un clivage entre la chaîne lipidique et le sucre lors du processus de reconnaissance. Cependant, la perte d'activité observée suggère que la fonction amide interagit d'une façon ou d'une autre avec un éventuel récepteur. Dans un deuxième temps, nous nous sommes orientés vers une méthode plus systématique pour l'étude du rôle de la structure de la chaîne, en utilisant les réactions à multi-composants de type Ugi ou Passerini. Celles-ci feraient intervenir l'isonitrile du squelette oligosaccharidique, un aldéhyde, un acide et, dans le cas de la réaction d'Ugi, une amine. En faisant varier la nature de ces trois derniers composés, on devrait pouvoir arriver rapidement à un grand échantillonnage d’analogues. Les essais de couplage réalisés sur la glucosamine se sont révélés encourageants laissant prévoir la possible extrapolation au tétramèreThe process of nitrogen fixation by leguminous plants is initiated by the exchange of signal compounds: flavonoids secreted by the plant and nodulation factors (Nod factors) secreted by the bacterium. Nod factors consist in a short chitin oligosaccharidic backbone (typically tetra or pentameric) that is N-acylated at the non-reducing end by a fatty acid. Ln order to understand the role of the structural elements of the bacterial molecule (the nodulation factor) that are involved in the nodulation induction, we have prepared analogs able to trigger the organogenesis in the plant. The focus is on the symbiotic relationship between alfalfa or vetch and their specific rhizobia. The tetrameric backbone was produced by the appropriate E. Coli recombinant cells. The first type of analogs are lipo-chitooligosaccharides in which the fatty-acid is fixed on the sugar via an amine. The sulfated compounds were tested on alfalfa and proved to be still active in nodulation induction, suggesting that there is no cleavage of the fatty-acid during the recognition process. However a decrease of activity seems to prove the influence of the amide group in the recognition process. In a second time, we considered the synthesis of various analogs with modified lipid chains by a method using multi-component reactions such as Passerini and Ugi reactions. Preliminary experiments with glucosamine derivatives are very promising and extrapolation to the tetrameric compounds are in progress
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Shearman, C. A. "Structure, function and regulation of nodulation genes of Rhizobium leguminosarum." Thesis, University of East Anglia, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.376087.
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Searle, Iain Robert. "Towards the map-based cloning of nodulation genes from soybean /." St. Lucia, Qld, 2001. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe17650.pdf.
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Lombardo, Fabien. "Nodulation mutants of Lotus japonicus defective for infection thread growth." Thesis, University of East Anglia, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.426571.
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Burn, Joanne Elizabeth. "Analysis of the regulatory nodulation gene nodD of rhizobium leguminosarum." Thesis, University of East Anglia, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.329095.
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Klein, Shoshana. "The role of rhizobium meliloti exopolysaccharide in nodulation of alfalfa." Thesis, Massachusetts Institute of Technology, 1987. http://hdl.handle.net/1721.1/14626.
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Lestari, Yulin. "Nodulation and nitrogen fixation in Medicago species at low pH." Title page, contents and summary only, 1993. http://web4.library.adelaide.edu.au/theses/09PH/09phl6418.pdf.
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Gardner, Chris. "Promotion and prevention of infection thread development in the Rhizobium-legume symbiosis." Thesis, University of East Anglia, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.338246.
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Tawfiq-Alkafaf, Najlaa. "Molecular genetics of glutathione S-transferase production in Rhizobium." Thesis, University of East Anglia, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.338245.
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Zhao, Lihan. "Genetic modification of nodulation and N2 fixation in soybean / Lihan Zhao." [St. Lucia, Qld.], 2004. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe18398.pdf.
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Haage, Kristina. "The lotus japonicus temperature-sensitive root development and nodulation mutant brush." Diss., Ludwig-Maximilians-Universität München, 2012. http://nbn-resolving.de/urn:nbn:de:bvb:19-164274.
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Heckmann, Anne B. "Lotus japonicus nodulation requires two GRAS-domain regulators, NSP1 and NSP2." Thesis, University of East Anglia, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.441605.
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Salo, Lucinda Faith. "COMPETITION BETWEEN STRAINS OF RHIZOBIA FOR NODULATION OF LEUCAENA LEUCOCEPHALA (LEGUME)." Thesis, The University of Arizona, 1985. http://hdl.handle.net/10150/275326.
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Bonaldi, Katia. "Caractérisation de la symbiose Nod-indépendante entre les Bradyrhizobium photosynthétiques et les légumineuses tropicales du genre Aeschynomene." Thesis, Montpellier 2, 2010. http://www.theses.fr/2010MON20185.
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Les Bradyrhizobium photosynthétiques sont capables d'induire la formation de nodules fixateurs d'azote chez certaines légumineuses du genre Aeschynomene. La découverte récente que certaines de ces souches ne possèdent pas les gènes canoniques nodABC indique l'existence d'un nouveau processus symbiotique rhizobium-légumineuse indépendant des facteurs Nod. L'objectif de ce travail de thèse a consisté à avancer dans la compréhension des mécanismes mis en jeu lors de cette nouvelle interaction. Dans un premier temps, à travers différentes approches cytologiques, le processus par lequel la bactérie infecte la plante en l'absence de facteurs Nod a été décrit. Dans un deuxième temps, afin de mettre en évidence les bases moléculaires de cette interaction, une banque de 15 000 mutants Tn5 de la souche ORS278 a été criblée sur plante. Ce criblage a permit l'identification de plus d'une centaine de gènes bactériens intervenant durant le processus symbiotique. Les résultats obtenus nous ont conduits à proposer un modèle dans lequel la mise en place de la symbiose Nod-indépendante impliquerait, d'une part, la synthèse bactérienne d'une cytokinine permettant le déclenchement de l'organogenèse nodulaire, et d'autre part, d'autres signaux bactériens intervenant dans l'étape de reconnaissance avec la plante hôte. Enfin, nous avons mis en place une technique de transformation génétique d'Aeschynomene et validé cet outil à travers l'étude de l'expression hétérologue de la noduline précoce MtENOD11. Il peut à présent être envisagé de conduire des études fonctionnelles sur Aeschynomene en vue de caractériser la voie de signalisation Nod-indépendanteThe photosynthetic Bradyrhizobium are able to induce the formation of nitrogen-fixing nodules in some legumes of the Aeschynomene genus. The recent discovery that some of these strains lack the canonical nodABC genes indicates the existence of a new symbiotic rhizobium-legume process that is independent of Nod factors. The aim of this work was to improve our understanding of the mechanisms involved in this new interaction. First, through various cytological approaches, the process by which the bacterium infects the plant in the absence of Nod factors has been described. Second, in order to decipher the molecular basis of this interaction, a library of 15,000 Tn5 mutants of the ORS278 strain was screened on plant. This screening allowed the identification of about one hundred bacterial genes involved in this symbiotic process. These results led us to propose a model in which the establishment of the Nod-independent symbiosis involves, on one han d, the synthesis of a bacterial cytokinin that triggers nodule organogenesis, and on the other hand, others bacterial signals that permit the recognition with the host plant. Finally, we developed a genetic transformation procedure of Aeschynomene and we validated this tool by studying the heterologous expression of the early nodulin MtENOD11. Now, functional studies on Aeschynomene are possible to permit the characterization of the Nod-independent signaling pathway
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Mutch, Lesley Anne. "Molecular ecology of rhizobia isolated from native and cultivated Vicieae." Thesis, University of York, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.313847.
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Lemes, Hamawaki Raphael. "EVALUATION OF DI-NITROGEN FIXATION IN EARLY AND LATE DEVELOPMENTAL STAGES OF SOYBEAN (Glycine max [L.] Merr.)." OpenSIUC, 2018. https://opensiuc.lib.siu.edu/dissertations/1592.
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Nitrogen (N) is present in proteins, enzymes, cell structures, purines and pyrimidines in DNA and RNA molecules, photosynthetic pigments, and several other types of molecules in all living organisms. Nonetheless, even though N makes up more than 78% of the atmosphere, it is reported to be the most frequent deficient nutrient in plants. Nitrate (NO3-) and ammonium (NH4+) are the N forms absorbed by plants from soil, but legume crops can establish symbiotic relationships with rhizobia bacteria, and fix N2 from the atmosphere. In soybean, increasing yield and protein content are raising the crop's N requirement; therefore, enhanced N2 fixation is seen as a reliable path to avoid the use of N fertilizers. In this study, the objective was to perform a comprehensive screening in greenhouse and field conditions of soybean genotypes for traits related to N2 fixation. The purpose was to identify among the soybean genotypes different N2 fixation profiles at early and late stages, as well as to investigate their capacity to accumulate above-ground N and supply carry-over N to following crops. The results showed different profiles among the soybean genotypes for early and late N2 fixation capacity, both in greenhouse and field evaluations. Different traits were correlated to either early or late N2 fixation activity. Soybean and winter-rye shoot dry mass were evaluated in the field to assess above-ground N accumulation and carry-over N, respectively. Soybean genotypes were identified with specific capacities to accumulate N in above-ground biomass or supply N to winter-rye. The patterns of N2 fixation identified in this study, as well as the different abilities to accumulate N above-ground or supply N to following crops, could assist in the selection of superior lines with improved N2 fixation capacity.
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Tan, Sovanna. "Caractérisation fonctionnelle de facteurs de transcription associés à la signalisation des cytokinines et impliqués dans la nodulation symbiotique chez Medicago truncatula." Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLS044.
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L’interaction symbiotique légumineuses-rhizobium nécessite l'infection des racines de la plante par les bactéries et l’initiation de divisions cellulaires dans le cortex racinaire.Les cytokinines sont des hormones végétales agissant via une signalisation par phosphotransfert qui conduit à l’activation de Régulateurs de Réponse de type B (RRBs), des facteurs de transcription régulant l'expression des gènes de réponse primaire aux cytokinines. Une étude phylogénétique menée sur plusieurs espèces de légumineuses a révélé une expansion génique de la famille des RRBs et l’apparition de formes non-canoniques de ces facteurs de transcription. Chez Medicago truncatula,MtRRB3 est le RRB le plus fortement exprimé dans les racines et les nodosités et est impliqué dans la nodulation. En effet, les plantes dont l’expression de MtRRB3 a été réduite par ARNi ainsi que des mutants rrb3 présentent une diminution significative du nombre de nodosités formées. De plus, l’expression de gènes associés à la nodulation, tels que "Nodulation Signalling Pathway 2" (MtNSP2) et "Cell Cycle Switch 52A"(MtCCS52A), est réduite en réponse aux cytokinines dans ces mutants. Des fusions transcriptionnelles avec le rapporteur GUS montrent que MtRRB3, MtNSP2 et MtCCS52Aprésentent un profil d’expression spatiale largement chevauchant dans les racines et lesnodosités. Des expériences de ChIP-qPCR et de trans-activation en protoplastes indiquent par ailleurs que MtRRB3 peut respectivement interagir avec et activer les promoteurs des gènesMtNSP2 et MtCCS52A. Cette thèse a donc permis d’établir des mécanismes moléculaires impliqués dans les régulations transcriptionnelles médiées par les cytokinines lors de la mise en place des nodosités symbiotiques fixatrices d’azoteThe legume-rhizobium interaction requires the infection of plant roots by rhizobia and the initiation of cell divisions in the root cortex. Cytokinins, a class of plant hormones acts trough a phosphotranfert signalling leading to the activation of Type-B Response Regulators(RRBs) which are transcription factors regulating the expression of cytokinins primary response genes. Phylogenetic analyses carried out indifferent legume species genomes showed anexpansion of the RRB genes family associated toan increase in non-canonical RRBs. In Medicago truncatula nodules, MtRRB3 is the most expressed RRB in roots and nodules. MtRRB3 islinked to nodulation as MtRRB3 RNAi silencedplants as well as rrb3 mutants display asignificant decrease of nodule number. Inaddition, the expression of the nodulation related genes Nodulation Signalling Pathway 2(MtNSP2) and Cell Cycle Switch 52A(MtCCS52A) is reduced in response to cytokininsin rrb3 mutants. The expression pattern of apMtRRB3-GUS fusion overlaps with thepMtNSP2-GUS and pMtCCS52A-GUS fusions in roots and nodules. Finally, ChIP-qPCR and protoplast trans-activation experiments showed that MtRRB3 can respectively interacts with and activate MtNSP2 and MtCCS52A promoters. This thesis have thus established molecular mechanisms associated to transcriptional regulations mediated by cytokinins during the legume symbiotic nitrogen-fixing nodulation
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Sutton, J. Mark. "Analysis of the function and secretion of the nodulation signalling protein, NodO." Thesis, University of East Anglia, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.359325.
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Ramon Fernandez, un des plus eminents critiques franc;ais de I' entre-deuxgue~ es, revient a. I 'actualite apres une eclipse de trente-cinq ans. Et en m~me temps revient Ie souvenir d 'une carriere commencee avec eclat sous Ie signe de I 'humanisme de Ia personnalite et terminee prematurement par la mort au moment ou s'effondrait autour de Fernandez Ie nouvel ordre europeen dont il etait devenu un des principaux porte-paroles. Comment expliquer la trajectoire qui Ie mena du socialisme au fascisme, de I 'extr~me-gauche en 1934 a. la Collaboration en 19401 Pourquoi Ie decalage, sensible a. ses contemporains, entre Ia promesse de I'CEuvre et l'apparent echec de l'homme? D'aucuns en ont cherche la clef dans Ie conflit d'heritages spirituels ou dans Ie sentiment de declassement social d'un homme ne d'une mere franc;aise d'origine bourgeoise et d'un aristocrate mexicain. Et qui pour comble de difficulte se sentait different de sa generation pour ne pas avoir fait la guerre de 1914-1918. Nous croyons que les racines du drame sont ailleurs, dans Ie bouleversement subi par un enfant accidentellement prive de son pere a. I 'age de onze ans, traumatisme qui rencontrant dans Ie psychisme les traces du fantasme parricidaire, devint Ie mobile profond de sa vocation. Dans la premiere partie de notre these, nous ex ami nons Ies faits de la jeunesse de Fernandez et Ies traits de sa personnalite a. la lumiere des concepts psychanalytiques. Dans la deuxieme partie, nous montrons comment les themes, I 'organisation et Ie langage de sa pensee prennent leur sens dans des idees inconscientes se referant a. Ia mort du pere, problematique que Fernandez essaya d'explorer imaginativement dans ses romans, auxquels nous consacrons la section suivante. Nous montrons enfin comment ses ouvrages critiques successifs reposent sur une identification de caractere paternel avec I' auteur qui evolue selon des modalites psychiques.
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Rabah, Nasser Rima. "Physiological aspects of the response to elevated CO₂ in lentils (Lens culinaris Medic)." Thesis, University of Plymouth, 2009. http://hdl.handle.net/10026.1/253.
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This study examined the effects of elevated CO2 and its interaction with drought and nitrogen fertilizer on the growth, production and nodulation of the leguminous crop lentil (Lens culinaris Medic) cultivars ILL7979 and ILL6994 (Idlib 3). Plants were grown under ambient and elevated CO2 at full and limited irrigation conditions in both open top chambers, which were later proven to be unreliable because of CO2 leakage, and tightly sealed and ventilated chambers which were reliable. Destructive harvests at anthesis and at maturity were conducted and results from sealed chambers at maturity showed that above ground dry weight was increased by an average of 12% under elevated CO2, but this increase was not statistically significant.
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Castaneda, Saldana Rafael. "Characterization of the Sinorhizobum Meliloti Chotaxis System." Thesis, Virginia Tech, 2019. http://hdl.handle.net/10919/96148.
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Increasing awareness to global climate change has drastically focused attention on finding solutions to reduce environmental impacts while still providing sufficient food for the increasing world population. Beneficial Nitrogen Fixing (BNF) microbes provide a possible solution by delivering biological nitrogen to plants resulting in reduced environmental impacts due to fertilizer runoff and eutrophication. One well studied model is that of Sinorhizobium meliloti and its legume host Medicago sativa (alfalfa), the fourth largest USA crop used for animal feed. Advancing research for this symbiosis model can provide solutions to enhance yield while minimizing environmental impacts.
Chapter 2 focuses on the deviation of the S. meliloti chemotaxis system from the enteric paradigm. Quantitative immunoblots determined the cellular amounts of chemotaxis proteins. Overall, chemotaxis protein levels were approximately 10-fold lower in S. meliloti compared to B. subtilis and E. coli. Focusing on cellular stoichiometric ratios, S. meliloti generally exhibits drastically higher values for CheB, CheR, and CheY to the histidine kinase CheA monomer compared to E. coli and B. subtilis.
Chapter 3 characterizes the role of McpX to quaternary ammonium compound (QAC) sensing. QACs are exuded by germinating alfalfa seeds. In vitro binding assays were performed to determine ligand binding characteristics. S. meliloti chemotaxis behavior to QACs was analyzed in in vivo capillary assays under real-time imaging.
These studies strengthen our knowledge of the chemotaxis system in the symbiosis model of S. meliloti and alfalfa. The data can further be used to create a mathematical model of the dynamics of bacteria-host interaction. The results can be used to optimize chemotaxis to host plants to improve crop yield and protect watersheds.Master of Science
Increasing awareness of global climate change has drastically focused attention on finding solutions to reduce environmental impacts while still providing sufficient food for the increasing world population. Beneficial Nitrogen Fixing (BNF) microbes may offer a feasible solution in reducing environmental impacts by supplying biological nitrogen to plants, which reduces fertilizer use and ultimately runoff. One-well studied beneficial microbial model is that of Sinorhizobium meliloti and its legume host Medicago sativa (alfalfa), the fourth most cultivated USA crop used for animal feed. Advancing research for this symbiosis model can provide solutions to enhance crop yield while diminishing environmental impacts.
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Rodpothong, Patsarin, and n/a. "Host-specific Nod factor requirements for nodulation of Lotus species by Mesorhizobium loti." University of Otago. Department of Microbiology & Immunology, 2008. http://adt.otago.ac.nz./public/adt-NZDU20080910.113419.
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Mesorhizobium loti possesses a symbiosis island (ICEMlSym[R7A]) that confers upon the bacterium the ability to form a symbiotic association with legumes of the genus Lotus. Nodulation (nod, nol and noe) genes located on the ICEMlSym[R7A] encode enzymes that are responsible for the production of a species-specific signaling molecule, named Nod factor. Perception of Nod factors by plant receptors triggers several plant responses and facilitates bacterial invasion, leading to the formation of root nodules. The studies in this thesis aimed to examine the impact of various structural components of the M. loti Nod factor on host specificity and recognition within Lotus species. The minimal gene requirement for eliciting nodule development on Lotus plants was also determined.
The M. loti strain R7A Nod factor has a backbone of five N-acetyl-D-glucosamine (GlcNAc) residues. The non-reducing terminal GlcNAc residue carries an acyl chain of either a vaccenic acid (C[18:1]) or palmitic acid (C[16:0]), a carbamoyl group and a methyl group, while an acetylfucose is present at the reducing terminus. Analysis of loss-of-function [Delta]nodZ and [Delta]nolL mutants showed that the acetylfucose at the reducing terminus was required for efficient nodulation of Lotus species, especially during the initiation of infection threads and for induction of symbiotic gene, NIN. Upon inoculation with R7A[Delta]nodZ, nodulation of Lotus corniculatus and L. filicaulis was significantly delayed and reduced, while only a delay in the onset of nodulation was observed with L. japonicus. Interestingly, nodulation of L. burttii induced by R7A[Delta]nodZ was as efficient as that induced by R7A. Hence, the absolute requirement for the acetylfucose during nodulation was host-dependent.
In planta complementation and domain swap experiments using transgenic L. japonicus nfr1 and nfr5 mutants were employed to investigate the role of the reducing terminal acetylfucose in the perception of Nod factor. Nodulation of complemented L. japonicus nfr1 and nfr5 mutants inoculated with R7A[Delta]nodZ was poor, whereas similar plants inoculated with R7A nodulated well. This suggests that the in planta complementation was inefficient and as a result accentuated the effect of the acetylfucose on the Nod factor recognition. The responses of recombinant inbred lines (RILs) derived from a cross between L. filicaulis and L. japonicus to inoculation with strain R7A[Delta]nodZ suggested that at least two genetic loci on chromosome 4, in addition to the Nfr1 and Nfr5 genes, contribute to Nod factor perception and in particular the host-specific recognition of the acetylfucose, This suggests the involvement of multiple receptors or a receptor with multiple components in the perception of Nod factors.
A gain-of-function study demonstrated that the presence of nodulation genes alone in nonsymbiotic mesorhizobia was sufficient to induce nodulation and bacteroid formation on Lotus plants, indicating that no other ICEMlSym[R7A] genes were required for infection thread formation or bacterial release. Nodulation assays of four Lotus species indicated host-specific requirements for nodulation genes. The presence of the nodA, nodC, nodD1, nodD2, nodZ, noeL and nolK genes was sufficient to permit nodulation of L. burttii, but was insufficient to induce nodulation of L. japonicus, L. corniculatus and L. filicaulis. The importance of the carbamoyl and methyl groups, and the influence of Nod factor concentration during nodulation were also implicated in this study. A model for the Nod factor perception in Lotus was proposed.
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Zhang, Feng 1962 Aug 29. "Soybean symbiotic signal exchange, nodulation, and nitrogen fixation under suboptimal root zone temperatures." Thesis, McGill University, 1996. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=40295.
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In the N$ sb2$ fixing legume symbiosis, suboptimal root zone temperatures (RZTs) not only decrease N$ sb2$ fixation. but reduce the formation and development of nodules. The purpose of this thesis was to elucidate the mechanism by which suboptimal RZTs affect nodulation and nodule development in legumes, such as soybean (Glycine max (L.) Merr.) and to attempt to find ways to overcome this inhibition. Initial studies characterized the RZT response in soybean plants inoculated with Bradyrhizobium japonicum. In plants grown at RZTs from 25 to 17$ sp circ$C, the time between soybean inoculation with B. japonicum and the beginning of N$ sb2$ fixation increased by 2.5 days for every $ sp circ$C decrease, whereas below 17$ sp circ$C RZT each $ sp circ$C appeared to delay the onset of N$ sb2$ fixation by 7 days. RZTs less than 17$ sp circ$C strongly inhibited the nodulation process and, as a result also sharply decreased N$ sb2$ fixation per plant. The greater sensitivity below 17$ sp circ$C is due to events related to, or occurring before infection initiation. Coinoculation of soybean with B. japonicum and other microorganisms beneficial to legumes, either vesicular-arbuscular (VA) mycorrhizae or plant growth promoting rhizobacteria (PGPR), increased soybean nodulation and N$ sb2$ fixation, but these increases were temperature dependent. Vesicular-arbuscular mycorrhizal colonization had a negative effect on nodule establishment below 18.5$ sp circ$C RZT, but a positive one above this RZT. At each temperature tested some PGPR increased the amount of fixed N and number of nodules formed, whereas some decreased the level of these variables. The most stimulatory strain at each temperature was: 15$ sp circ$C-Serratia proteamaculans 1-102, 17.5$ sp circ$C - S. proteamaculans 1-102 and Aeromonas hydrophila P73, and 25$ sp circ$C - S. liquefaciens 2-68.Because our research indicated that an event before infection thread initiation was most sensitive, and because the first known step in establishment of the symbiosis is production of a plant-to-bacterial signal molecules. I tested whether the poor nodulation at suboptimal RZTs was related to disruption of plant-to-bacterium signalling. Inocula bacteria were preincubated with genistein, a major isoflavonoid signal molecule in soybean. This shortened the period between inoculation and root hair curling, and hastened the onset of N$ sb2$ fixation under both controlled environment and field conditions. At 15 and 17.5$ sp circ$C RZTs, 20 and 15 $ mu$M genistein was found to reduce the inhibition of suboptimal RZTs, increase nodulation, and accelerate the onset of ${ rm N} sb2$ fixation. When applied to the plant rhizosphere in the field, genistein also reduced the inhibitory effects of cold spring soils on nodulation and N$ sb2$ fixation. Direct measurements of genistein accumulation in soybean roots indicated that, with decreasing RZTs, genistein accumulation decreased. B. japonicum USDA110 containing plasmid ZB977 with nodY-lacZ fusion genes incubated with genistein under different temperatures indicated that higher genistein concentrations and longer incubation times were required to activate the lacZ gene to a maximum level under low incubation temperature. Overall, these findings suggested that plant-to-bacteria signal molecules such as genistein may be an important limiting factor in the nodulation of legume plants at low RZT.
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Middleton, Patrick Henry. "Identification of a gene essential for nodulation in the model legume Medicago truncatula." Thesis, University of East Anglia, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.441614.
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Bec-Ferté, Marie-Pierre. "Facteurs de nodulation de Rhizobium fredii : mise en évidence de nouvelles variations structurales." Toulouse 3, 1995. http://www.theses.fr/1995TOU30230.
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Les bacteries du genre rhizobium infectent de maniere specifique les plantes appartenant a la famille des legumineuses et induisent la formation d'un nouvel organe vegetal, le nodule, a l'interieur duquel les bacteries vont reduire l'azote atmospherique en ammoniac directement assimilable par la plante. Les flavonoides, presents dans les exsudats racinaires, induisent la transcription de genes bacteriens controlant la biosynthese et le transport de facteurs extracellulaires, les facteurs nod, lipo-chitooligosaccharides capables d'induire de facon specifique l'organogenese nodulaire. Rhizobium fredii usda257, a large spectre d'hote, ne nodule que certains cultivars de soja dits primitifs. Les cultivars de soja americains dits ameliores, nodules par les souches de bradyrhizobium japonicum, ne sont infectes que par la souche r. Fredii usda191. La specificite d'hote etant principalement liee a la structure des facteurs nod, nous avons caracterise ceux produits par deux souches de r. Fredii, usda257 et usda191. La souche usda257 produit des facteurs constitues d'un enchainement de 3 a 5 residus de glucosamine, n-acyles cote terminal non reducteur par l'acide vaccenique, n-acetyles sur les autres residus et substitues par un derive de fucose en o6 de la glucosamine reductrice. . . .
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Debelle, Frédéric. "Etude de genes de rhizobium meliloti controlant la nodulation specifique de medicago sativa." Toulouse 3, 1988. http://www.theses.fr/1988TOU30194.
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La mutagenese par le transposon tn5 d'un fragment de 30 kb du megaplasmide psym de r. Meliloti, a permis de mettre en evidence 3 regions portant des genes de nodulation dont on etudie les proteines correspondantes. Le transfert a r. Trifolii d'un plasmide portant les genes nodfeg et nodh de r. Meliloti rend la souche hybride capable de noduler la luzerne mais inapte a noduler le trefle
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Debelle, Frédéric. "Etude de gènes de Rhizobium meliloti contrôlant la nodulation spécifique de Medicago sativa." Grenoble 2 : ANRT, 1988. http://catalogue.bnf.fr/ark:/12148/cb37613006c.
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Zatakia, Hardik M. "Characterization of symbiotically important processes in Sinorhizobium meliloti." Diss., Virginia Tech, 2015. http://hdl.handle.net/10919/56652.
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Bacteria perform biological nitrogen fixation (BNF) which leads to conversion of N2 to ammonia. One of the best studied models of BNF is the symbiotic association of Sinorhizobium meliloti - Medicago sativa (alfalfa). Since alfalfa is a major source of animal feed and the fourth largest crop grown in the USA, enhanced understanding of this symbiosis can have implications for increasing crop yields, reducing environmental contamination and food costs. Studies discussed here focus on two symbiotically important bacterial traits, type IVb pili and chemotaxis.
Chapter 2 characterizes S. meliloti type IVb pili encoded by flp-1 and establishes their role in nodulation. Bundle-forming pili were visualized in wild-type cells, while cells lacking pilA1, the pilin-encoding gene, showed an absence of pili. Competitive nodulation assays with alfalfa concluded that cells lacking pili had a significant nodulation defect. Regulation of pilA1 expression via a quorum sensing regulator, ExpR, was confirmed.
Chapter 3 describes the role of the flp-2 cluster in establishing symbiosis. PilA2 is a pilin subunit encoded from flp-2. The pilA2 deletion strain was defective in nodulation by 31% as compared to the wild type. A non-significant change in nodulation was seen in pilA1pilA2 strain. Thus, both flp-1 and flp-2 have a significant role in establishing symbiosis.
Chapter 4 focuses on the deviations of S. meliloti chemotaxis from the enterobacterial paradigm. Transcriptional fusions showed that S. meliloti chemoreceptors (MCPs) are class III genes and regulated by FlbT. Quantitative immunoblots determined the cellular amounts of chemoreceptors. Chemoreceptors were grouped in three classes; high, low, and extremely-low
abundance, similar to the high and low abundance chemoreceptors of Escherichia coli. Importantly, the MCP:CheA ratio in an S. meliloti cell was observed to be 37:1, similar to that in Bacillus subtilis of 24:1, but quite different from that in E. coli of 3.4:1. In conclusion, our data indicates that soil bacteria may have optimized their chemotaxis system based on their milieu, which is different from enteric bacteria.
These studies have enhanced our understanding of two symbiotically important processes in S. meliloti, and pave the way for future manipulations of the system to increase symbiosis and reduce our dependence on synthetic fertilizers.Ph. D.
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Bélanger, Elaine. "Purification et caractérisation des facteurs de nodulation de Rhizobium sp., Oxytropis arctobia, souche N33." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp01/MQ38014.pdf.
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Bai, Yuming 1953. "Enhanced soybean nodulation and nitrogen fixation via modifications of Bradyrhizobial inoculant and culture technologies." Thesis, McGill University, 2002. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=38147.
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Soybean (Glycine max L. Merr.) and Bradyrhizobium japonicum can form a nitrogen fixing symbiosis. This symbiosis is important for most sustainable agriculture systems. This thesis examines two ways to enhance nodulation and nitrogen fixation by this symbiosis: coinoculation of plant growth promoting bacteria (PGPB) with B. japonicum, and addition of RNA to a bradyrhizobial culture medium. The optimal coinoculation dose of Serratia proteamaculans 1--102 and S. liquefaciens 2--68 was determined as 108 cells per plant under both optimal and suboptimal root zone temperatures (RZTs). Nodulation dynamics studies indicated that coinoculation of these two PGPB caused earlier nodule initiation and a higher nodulation rate, contributing to the higher nodule number and nodule weight. The coinoculation also increased nitrogen fixation efficiency under both optimal and suboptimal RZTs. A novel inducible activator only produced by the bacteria after addition of flavonoids to the culture system was prepared and evaluated in greenhouse and field experiments. Fourteen non-bradyrhizobial endophytic bacteria (NEB) were isolated from the surface sterilized root nodules, and three of these, designated NEB4, NEW and NEB17, showed soybean plant growth promotion under both greenhouse (with controlled RZTs) and field conditions. Alone, they were neither nodule inducers nor nitrogen fixers. Biolog tests and partial 16S rRNA gene sequence analyses placed the three strains in genus Bacillus: NEB4 and NEB5 are B. subtilis and NEB17 B. thuringiensis. Bradyrhizobium species grow slowly, making the culture process long and the cost of inoculant production higher. Addition of commercial yeast RNA to the bacterial culture medium accelerated the bacterial growth rate, shortened the culture time and increased the lipo-chitooligosaccharide (LCO) yield in flask cultures. Inoculation experiments in the greenhouse also showed that bradyrhizobial inoculant produced in the presence of RNA had better symb
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Larson, Kim. "Evaluation of soybean inoculant products and techniques to address soybean nodulation problems in Kansas." Thesis, Kansas State University, 2013. http://hdl.handle.net/2097/16303.
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Master of ScienceDepartment of Agronomy
Kraig Roozeboom
Nitrogen fixation by Bradyrhizobium japonicum in soybean [Glycine max] is highly beneficial in soybean crop production. Nodulation issues have been encountered on fields new to growing soybeans in recent years in Kansas. The purpose of this research was to evaluate soybean nodulation performance under various situations and seed handling practices in order to educate producers on how to achieve reliable nodulation consistency in the field. The objectives of the study were to: 1) compare inoculant products using single and double rates and in combination with one another on fields with varying soybean history; 2) determine if there was a negative interaction between inoculant products and common seed treatments; and 3) discover the influence of inoculated seed storage conditions before planting on the rhizobia’s ability to successfully nodulate soybean roots. Field experiments were conducted on diverse Kansas sites in 2011 and 2012. Inoculant treatment and seed treatment interaction trials had ten and seven experimental sites respectively. Inoculated seed storage conditions were evaluated in a greenhouse experiment during the spring of 2013. All studies used a randomized complete block design with four replications. The Novozymes inoculant products generally provided superior nodulation performance over other company products in the study where soybean had not been in recent rotation with an average increase of 167% in nodule number verses the control. The combination of dry and liquid inoculant products provided a significant increase in root nodule number at five of the environments out of recent rotation with a 76% increase over single inoculant rates. Although there were early season nodulation differences between treatments in new soybean ground, these did not carry through to seed yield differences in the majority of research sites. Hot and dry summer conditions reduced yields, making detection of treatment differences difficult. There were no negative effects on nodulation performance with any of the seed treatments. Although soybean seed yield was 634 kg ha[superscript]-[superscript]1 greater for the Novozyme combination treatment compared to the check at one location in 2011, the control yielded as well or better than all other treatment/inoculant combinations, implying that yield differences were likely not related to inoculant treatments. At other sites, yield was not influenced by seed treatment and inoculant combinations. Results indicate that seed treatment formulations did not significantly impact bacterial inoculant product performance, soybean nodulation, or yield. Storage conditions had no effect on nodulation performance in the greenhouse study, likely due to survival of Bradyrhizobium japonicum in the heat-treated growth medium.
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Bashore, Sarah L. aity. "Characterization of a Spontaneous Phaseolus Vulgaris Mutant with the Ability to Selectively Restrict Nodulation." Ohio University / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1155747948.
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Dashti, Narjes. "Plant growth promoting rhizobacteria and soybean nodulation, and nitrogen fixation under suboptimal root zone temperatures." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape15/PQDD_0027/NQ29918.pdf.
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Lira, Junior Mario de Andrade. "Environmental factors and plant-to-bacteria signals effects on nodulation and nodule development of pea." Thesis, McGill University, 2001. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=38075.
Full textAbstract:
With the projected increase in global population, unprecedented increases in crop production will be needed and legume crops are one of the primary means of achieving these increases. The legume-Rhizobium symbiosis is the single most important source of biologically fixed nitrogen in agricultural systems but, as a biological system it is complex, and very sensitive to environmental effects, such as available soil nitrogen, soil pH (both high and low), soil salinity and extremes of soil temperature. Each of these may affect the delicate signal exchange process that occurs during symbiosis establishment. To better understand the effect of environmental factors on signal exchange and nodulation, we conducted four experiments, under controlled-environment conditions, with pea (Pisum sativum) as the model legume. The first experiment studied the effects of available nitrogen, the second the effects of low soil pH, the third the effect of soil salinity and the fourth the effects of low soil temperature. In all experiments the plants were inoculated with Rhizobium leguminosarum bv. viceae cells previously treated with 10 x 10-3 M of hesperitin or naringenin, or not treated (control). In all experiments plants were destructively sampled at 10, 20, 30 and 40 days after inoculation (in two experiments samplings were also conducted at 15 DAI), and data on plant and nodule variables were collected. To allow for a better understanding of the effects of flavonoids on nodule development an image analysis technique was developed that permitted us to measure every individual nodule at each sampling. This provided a more precise picture of nodule development over time than would have been possible with previous methods. Our results indicated that addition of flavonoids had positive effects on nodulation, both in number and size of nodules produced, and that the positive effects were greatest at the most inhibitory levels of the environmental factors tested, and at earlier sampling