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Dissertations / Theses on the topic 'Nitrogen-fixing plants'
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Cho, Hyojin. "A study of transcript profiling of soybean roots during nitrogen fixing symbiosis." Diss., Columbia, Mo. : University of Missouri-Columbia, 2006. http://hdl.handle.net/10355/5915.
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Thesis (M.S.)--University of Missouri-Columbia, 2006.The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on May 7, 2009) Includes bibliographical references.
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Devkota, Dibya. "Habitat, isolation, identification and nitrogen fixation of Rhizobiaceae associated with rangeland legumes from Wyoming, USA." Laramie, Wyo. : University of Wyoming, 2007. http://proquest.umi.com/pqdweb?did=1313917311&sid=1&Fmt=2&clientId=18949&RQT=309&VName=PQD.
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He, Xinhua. "Nitrogen exchange between plants through common mycorrhizal networks /." [St. Lucia, Qld.], 2002. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe18272.pdf.
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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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Rana, Debashis. "The nitrogen-fixing symbiosis between Rhizobium sp. sin-1 and Sesbania spp. /." free to MU campus, to others for purchase, 1997. http://wwwlib.umi.com/cr/mo/fullcit?p9842559.
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Miller, Simon Hugh, and n/a. "Genetic basis for the host-specific nitrogen fixation phenotype of Caucasian clover rhizobia." University of Otago. Department of Microbiology, 2006. http://adt.otago.ac.nz./public/adt-NZDU20070306.155157.
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Trifolium ambiguum (Caucasian clover) is being released in New Zealand for use in areas where growth of T. repens (white clover) is marginal. Although closely related to T. repens, T. ambiguum has unique and highly specific nodulation requirements and as rhizobial strains capable of effectively nodulating T. ambiguum are not naturally found in New Zealand soils, they must be introduced with the seed. Rhizobium leguminosarum bv. trifolii strains such as ICC105 form effective nodules on T. ambiguum but ineffective (Fix⁻) nodules on T. repens. The T. repens nodules nevertheless develop normally and contain bacteroids. R. l. bv. trifolii strains that are effective on T. repens such as NZP561, fail to nodulate T. ambiguum. As the host-specific nitrogen fixation defect of Caucasian clover rhizobia on T. repens has potentially adverse agronomic implications, the genetic basis for this Fix⁻ phenotype was investigated.
Rhizobium leguminosarum bv. trifolii strain ICC105 was converted to Fix⁺ on T. repens by the introduction of an 18-kb fragment of DNA from a white clover rhizobial strain (NZP514) symbiotic plasmid. This fragment contained several nif and fix genes, including nifHDKEN, fixABCX, nifA, nifB, fdxN and fixU. Tn5 mutation of these white clover rhizobial genes demonstrated that most were required to impart the Fix⁺ phenotype on T. repens to ICC105, with the exception of nifA. Mutagenesis of the ICC105 nifA gene and subsequent complementation with various combinations of the white clover rhizobia nif/fix genes as well as transcriptional lacZ fusion studies of the ICC105 nifA and nifH genes demonstrated that ICC105 nifA is expressed and functional during the ineffective nodulation of T. repens and able to activate expression of nifHDKEN and fixABCX operons derived from white clover rhizobium but not from ICC105.
Sequence analysis and comparison of the intergenic region between the divergently transcribed nif/fix operons revealed a conserved 111-bp region found between the nifH/fixA promoters of Caucasian clover rhizobia, but not in white clover rhizobia. Attempts to modify this region in ICC105 failed in creating a strain which was Fix⁺ on T. repens; however recombination of the nifHD/fixAB region from a white clover rhizobium into the ICC105 genome produced several strains with a �swapped� nitrogen fixation phenotype (i.e. Fix⁺ on T. repens and Fix⁻ on T. ambiguum). A hypothesis was therefore proposed by which differences in the nifH/fixA promoter regions of Caucasian clover rhizobia and white clover rhizobia modulate the expression of the upstream genes in response to the particular plant host they are nodulating.
The incompatibility between the symbiotic plasmid of R. l. bv. trifolii ICC105 and the white clover rhizobium symbiotic plasmid cointegrate, pPN1, was also investigated and potential regions of each plasmid involved in this incompatibility were identified.
The research presented in this thesis has contributed to the genetic knowledge of the nitrogen fixation genes, and regulation of these genes in R. l. bv. trifolii. It has also provided progress towards the goal of creating a suitable inoculant strain for T. ambiguum that is able to fix nitrogen in symbiosis with both T. repens and T. ambiguum.
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Abi-Ghanem, Rita. "Optimizing biological nitrogen fixation and evaluating Iraqi extension education." Pullman, Wash. : Washington State University, 2009. http://www.dissertations.wsu.edu/Dissertations/Summer2009/R_Abi-Ghanem_070909.pdf.
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Thorne, Stephen Howard. "Stationary phase survival of Rhizobium leguminosarum." Thesis, Imperial College London, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.265401.
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Burgoyne, Tricia A. "Free living nitrogen-fixation in ponderosa pine/Douglas-fir forests of western Montana." Connect to this title online, 2007. http://etd.lib.umt.edu/theses/available/etd-05302007-085002/.
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Riffkin, Penelope A. "An assessment of white clover nitrogen fixation in grazed dairy pastures of South-Western Victoria /." [Richmond, N.S.W.] : University of Western Sydney, Hawkesbury, 1999. http://library.uws.edu.au/adt-NUWS/public/adt-NUWS20030528.152118/index.html.
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Shah, Ritu. "Role of bacterial NADP dependent isocitrate dehydrogenase in the Bradyrhizobium japonicum and soybean symbiosis /." free to MU campus, to others for purchase, 2003. http://wwwlib.umi.com/cr/mo/fullcit?p3115604.
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Ditsch, David C. "Fate of ¹⁵N-depleted fertilizer N in a corn-rye cropping sequence: plant uptake and soil distribution." Diss., Virginia Tech, 1991. http://hdl.handle.net/10919/37238.
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Mirza, Babur S. "Saprophytic growth and fate of Frankia strains in soil /." View online, 2009. http://ecommons.txstate.edu/dissertations/AAI3384734/.
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Riffkin, Penelope A., of Western Sydney Hawkesbury University, and Faculty of Science and Technology. "An assessment of white clover nitrogen fixation in grazed dairy pastures of south-western Victoria." THESIS_FST_xxx_Riffkin_P.xml, 1999. http://handle.uws.edu.au:8081/1959.7/31.
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Australia is amongst the more efficient milk producers in the world.Milk production in the region of south-western Victoria relies mainly on rainfed white clover/perennial ryegrass pastures.As the demand for efficient and competitive milk production increases, the value of N2 fixation must be maximised. The objective of this thesis was to assess N2 fixation in grazed dairy pastures in south-western Victoria. Several tests and experiments were conducted and results noted. Studies revealed low white clover yields to be the major factor limiting N2 fixation in the region. For N2 fixation to have a significant impact on pasture quality and production, problems associated with legume persistence need to be addressed. Strategies may include the breeding of white clover cultivars with greater tolerance to water stress, improved winter production and increased competitiveness with companion species. Alternatively, the introduction of different legume species, better suited to the environment, may be appropriate. Where N2 fixation is unlikely to satisfy N demands, it may be necessary to introduce the strategic use of supplementary feeds or nitrogenous fertilisers. However, this would need to be carefully considered to ensure high input costs did not jeopardise the competitive advantage of low input pasture-based systemsMasters Thesis
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Berdugo, Silvia Eugenia Barrera. "Fixação biológica de N2 e diversidade de bactérias diazotroficas numa Floresta de Restinga." Universidade de São Paulo, 2012. http://www.teses.usp.br/teses/disponiveis/11/11140/tde-20092012-101012/.
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Diazotróficos de vida-livre podem ser encontradas associadas à filosfera, dermosfera e rizosfera das espécies vegetais. Alguns dados sugerem que a fixação biológica de N2 (FBN) por bactérias assimbióticas representa uma entrada importante de nitrogênio nos ecossistemas tropicais, variando com as espécies vegetais e nas diferentes partes da planta. O presente trabalho teve como objetivos estimar a quantidade de N2 fixado de forma assimbiótica na filosfera, dermosfera e rizosfera sobre a copa das espécies vegetais Guapira oposita e Euterpe edulis, e avaliar a diversidade das bactérias assimbióticas, através da análise do gene rRNA 16S, em uma Restinga ,em Ubatuba, SP. O estudo foi realizado no Parque Estadual da Serra do Mar, Núcleo Picinguaba, em épocas de baixa e alta pluviosidade. A atividade da nitrogenase foi determinada pela técnica de redução do acetileno e as concentrações de etileno foram determinadas por cromatografia gasosa. A diversidade de bactérias que habitam filosfera, dermosfera e solo foi acessada por pirosequenciamento da região V4 do gene rRNA 16S. A maior fixação de N foi observada na dermosfera de E. edulis nas duas épocas de coleta (175,1± 53,4 ng cm-2 h-1; 97,2 ± 21 ng cm-2 h-1), as taxas de fixação de N mais baixas foram observadas no solo. Na época de alta pluviosidade, a FBN na filosfera de G. oposita (52,0 ± 12 ng cm-2 h-1) foi significativamente maior do que a filosfera de E. edulis (3,6 ± 06 ng cm-2. h-1) e do que no mesmo compartimento mas em diferentes épocas de coleta (7,5 ± 1,3 ng cm-2 h-1). O valor do 15N foi maior no solo onde a fixação de N foi mais baixa. Na filosfera e na dermosfera, a relação C/N foi mais baixa quando a FBN foi mais alta. A FBN no solo e serrapilheira de restinga apresentou grande variação espacial, com locais de alta atividade. As 188629 sequências obtidas foram agrupadas em 16727 Unidades Taxonômicas Operacionais (UTOs), distribuídos em 35 filos. Os principais filos detectados foram Proteobacteria (38%) e Acidobacteria (12%). As classes Alphaproteobacteria e Gammaproteobacteria foram as mais abundantes nos três compartimentos. Potenciais fixadores de N foram detectados nas classes Alpha Beta e Gammaproteobacteria. A abundância de cianobacterias fixadoras de N na filosfera e na dermosfera foi baixa, indicando que outros diazotróficos também colonizam esses ambientes e contribuem com a FBN.Free-living N2 fixing bacteria can be found associated with the phyllosphere, bark and rizosphere of the diferent plant species. Some data suggest that biological N2 fixation (BNF) by free-living bacteria represents an important input of nitrogen in tropical ecosystem, varying with the plant species and in different parts of the plant. This study aimed to estimate the amount of N2 fixed in the phyllosphere, bark and soil under the canopy of Guapira opposite and Euterpe edullis, and evaluate the diversity of bacteria through the sequencing of the 16S rRNA gene analysis, the phyllosphere, bark and soil in a Restinga area, Ubatuba, SP. The study was conducted in the Parque Estadual da Serra do Mar, Núcleo Picinguaba in seasons of low and high rainfall. Nitrogenase activity was determined by the acetylene reduction assay (ARA) and ethylene concentrations were determined by gas chromatography. The diversity of bacteria in the phyllosphere, bark and soil was accesed using pyrosequencing of the 16S rRNA V4 region. The bark of Euterpe edullis was higher at both sampling times (175,1±53,4 ng. cm-2. h-1, 97,2±21 ng. cm-2. h-1). The BNF rates were lower in soil. In high rainfall conditions, the BNF in the phyllosphere of Guapira opposite increased significantly (52,0±12 ng. cm-2. h-1) when compared with Euterpe edullis (3,6 ± 06 ng. cm-2. h-1) and Guapira opposite (7,5 ± 1,3 ng. cm-2. h-1) phyllosphere. The value of 15N was higher in the soil where the rates of FBN was lower. In the phyllosphere and bark, C/N was lower when BNF was higher. BNF in soil great spatial variation with areas of high activity. The 18.629 sequences obtained were grouped into 16.727 Operational Taxonomic Units (OTUs) distributed in 35 phyla. The main phyla Proteobacteria represented 38% of the OTUs and Acidobacteria 12% of the UTOs. The classes Alphaproteobacteria and Gammaproteobacteria were the most abundant in the three compartmens. Alphaproteobacteria, Betaproteobacteria and Gammaproteobacteria were the main potential N-fixers. The abundance of nitrogen-fixing Cyanobacteria in the phyllosphere and bark was low, indicating that others diazotrophics also colonize these environments and contribute with BNF.
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Tufail, Muhammad Aammar. "Use of plant growth promoting endophytic bacteria to alleviate the effects of individual and combined abiotic stresses on plants as an innovative approach to discover new delivery strategies for bacterial bio-stimulants." Doctoral thesis, Università degli studi di Trento, 2021. http://hdl.handle.net/11572/305571.
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Bacterial endophytes are the organisms that live inside the plant for a full or a part of their life cycle. Endophytic bacteria have captured the interest of agriculture industry due to their plant beneficial properties, such as synthesis of phytohormones, solubilization of soil nutrients, and alleviation of biotic and abiotic stresses. Several studies have reported that stress tolerant endophytic bacteria can work with a similar performance as non-stressed conditions when inoculated to the plants under stressed conditions. Combination of abiotic stresses such as salinity, drought and low nitrogen stress can have additive or agonistic effects on bacterial and plant growth, and their interactions. However, very few studies have reported the impact of combined stress on endophytic bacterial assisted plant growth promotion. Therefore, understanding the underlying mechanisms of endophytic bacterial assisted plant’s tolerance abiotic stresses may provide the means of better exploiting the beneficial abilities of endophytic bacteria in agricultural production. Thus, the aim of this thesis was to study the stress tolerance mechanisms, beneficial characteristics, and plant growth promotion characteristics of endophytic bacteria under individual and combined abiotic stresses. Transcriptome analysis of endophytic bacteria revealed that tolerance mechanisms to deal with one kind of stress is different than concurrent stresses. Salinity and drought stress largely modulated the genes involved in flagellar assembly and membrane transport, showing reduced motility under stress conditions to preserve the energy. Additionally, bacterial endophyte that can fix nitrogen was studied with maize plant growth promotion under drought and low nitrogen stress conditions. The results suggested that diazotrophic bacterial endophyte can promote plant growth under moderate individual and combined stress conditions. Plant growth promoting endophytic bacteria can be utilized as an efficient tool to increase crop production under individual and concurrent abiotic stresses.
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Godschalx, Adrienne Louise. "Symbiosis with Nitrogen-fixing Rhizobia Influences Plant Defense Strategy and Plant-predator Interactions." PDXScholar, 2017. https://pdxscholar.library.pdx.edu/open_access_etds/3644.
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As sessile organisms, plants evolved a plethora of defenses against their attackers. Given the role of plants as a primary food source for many organisms, plant defense has important implications for community ecology. Surprisingly, despite the potential to alter entire food webs and communities, the factors determining plant investment in defense are not well-understood, and are even less understood considering the numerous symbiotic interactions in the same plant. Legume-rhizobia symbioses engineer ecosystems by fixing nitrogen from the atmosphere in trade for plant photosynthates, yet connecting symbiotic resource exchange to food web interactions has yet to be established. Here I test how rhizobia influence plant defense and tritrophic interactions in lima bean (Fabaceae - Phaseolus lunatus L.): a model plant in chemical ecology research characterized by a broad range of different defenses. Examining suites of traits among lima bean genotypes, highly cyanogenic cultivars and wild type plants (high cyanotypes) produce more hook-shaped trichomes, as a putative combined approach of chemical and mechanical defenses, forming defense syndromes to protect against multiple feeding guilds (Chapter 2). Testing costs that may have contributed to forming tradeoffs among strategies, high cyanotypes show reduced fitness under plant-plant competition relative to low cyanotypes, but when challenged with herbivory, high cyanotypes fitness reductions are no longer evident (Chapter 3). Young leaves, not reproductive organs, are the most cyanogenic lima bean organ, and removal quantitatively decreases fitness, supporting assumptions that the most valuable tissues will be most highly defended (Chapter 4). Testing the degree to which nitrogen-fixing rhizobia contribute to cyanogenesis, high cyanotypes form more nodules than low cyanotypes. Quantitative relationships between nodule number and plant traits highlight the role symbiotic investment plays a role in plant defense and nutritive phenotype, while simultaneously, genotypically-determined levels of defense shape plant investment in symbiosis (Chapter 5). Interestingly, traits that trade off by cyanotype (i.e. high cyanogenesis but low indirect defense) reflect the patterns in plants with nitrogen-fixing rhizobia. Rhizobia-inoculated lima beans show reduced indirect defenses, recruiting fewer parasitoid wasps (Chapter 6) and predatory ants (Chapter 7). Examining plant-ant attraction in greater detail, ants prefer headspace regions above EFN droplets, corresponding with species-specific differences in suites of volatiles, indicating EFN, like floral nectar, can be scented to manipulate insect behavior (Chapter 8). Overall, understanding when investing in traits to recruit predators is more effective than investing in defensive chemistry, and how particular ecological contexts, such as symbioses can influence the outcome of defense allocation strategies remains a fascinating area of research. Determining the mechanisms underlying why rhizobia and other belowground microbial symbionts influence their host plants' above ground interactions, whether plants traits affected by symbiotic microbes are simply a function of the costs and benefits from resource exchange, or whether symbionts can influence the success of primarily direct versus indirectly defended plants is an important question for understanding complex trophic systems and connecting to agricultural implications for more effective biological pest control.
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Dahiya, Preeti. "Plant glycoproteins as markers for symbiosome development in pea root nodules." Thesis, University of East Anglia, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.267321.
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Ruggles, Thomas Alan. "Plant communities on reclaimed surface mines in Northeast Ohio: Effects of succession and nitrogen-fixing autumn olive." Kent State University / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=kent1574681631819824.
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Sevilla, Myrna Quijano, and Myrna Quijano Sevilla. "Acetobacter diazotrophicus, a nitrogen-fixing bacterial endophyte of sugarcane: Analysis of nifHDK genes, plant colonization, and growth promotion." Diss., The University of Arizona, 1999. http://hdl.handle.net/10150/284150.
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Acetobacter diazotrophicus, a nitrogen-fixing bacterial endophyte, is believed to be responsible for biological nitrogen fixation (BNF) in sugarcane. However, no monocot has yet been unequivocally shown to receive fixed N through BNF. The main question addressed in this dissertation is whether A. diazotrophicus promotes plant growth, and if so, whether growth promotion is via BNF. Another question is whether the growth benefits can be extended to other grasses. To answer these questions, the nifHDK genes encoding the protein subunits of the nitrogenase enzyme were first isolated and sequenced. Secondly, Nif⁻ mutant strains were constructed by inserting a gene cassette in nifD. The growth of sugarcane plants inoculated with A. diazotrophicus wild type and Nif⁻ mutant strains were compared in growth chamber, greenhouse, and field experiments. A. diazotrophicus was also tagged with marker genes to investigate the colonization process in sugarcane and other grasses. The effect of A. diazotrophicus on the growth of other grasses was also determined. Analysis of the A. diazotrophicus NifHDK sequence revealed features typical of proteobacterial nifHDK genes and gene products. Phylogenetic analysis established the close relationship of A. diazotrophicus with the α-proteobacteria and the β-proteobacterium, Herbaspirillum seropedicae, another sugarcane endophyte. Nif⁻ mutant strains established endophytically in sugarcane plants equally well as wild type strains. ¹⁵N₂ incorporation experiments demonstrated that wild type strains but not the Nif⁻ mutants fixed N inside sugarcane plants with decreased fixation when plants were grown in medium with fixed N. In N-deficient conditions, sugarcane inoculated with wild type strains grew better and had higher total N content than either uninoculated or plants inoculated with Nif⁻ mutants. When N was not limiting, growth enhancement was observed in plants inoculated with either wild type or the Nif⁻ mutants. These results suggest that depending on the nitrogen condition, A. diazotrophicus promotes sugarcane growth via nitrogen fixation and other growth promoting factor. The results also indicated a possible strain-cultivar specificity in growth promotion. A. diazotrophicus colonized other grasses through different entry sites but was limited in the root. Under N-deficient conditions, wild type strain but not the Nif-- mutant promoted rice seedling growth indicating the beneficial effects of A. diazotrophicus to other grasses.
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Pan, Bo 1963. "Mineral nitrogen inhibition and signal production in soybean-B. japonicum symbiosis." Thesis, McGill University, 1999. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=36670.
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In the N2 fixing legume symbiosis, mineral nitrogen (N) not only decreases N2 fixation, but also delays and inhibits the formation and development of nodules. The purposes of this thesis were to elucidate the role of signaling in the mineral N effects on nodulation and nitrogen fixation in soybean [Glycine max (L.) Merr.] and to attempt to find ways to overcome this inhibition. The responses of soybean plants, in terms of daidzein and genistein synthesis and exudation, to different mineral N levels were studied. Daidzein and genistein distribution patterns varied with plant organs, mineral N levels, and plant development stages. Mineral N inhibited daidzein and genistein contents and concentrations in soybean root and shoot extracts, but did not affect root daidzein and genistein excretion in the same way. In both synthesis and excretion, daidzein and genistein were not affected equally by mineral N treatments. Variability existed among soybean cultivars in the responses of root daidzein and genistein contents and concentrations to mineral N levels. The amount of daidzein and genistein excreted by soybean roots did not always correspond to the daidzein and genistein contents and concentrations inside the roots. On the Bradyrhizobium japonicum side, nod gene expression was inhibited by mineral nitrogen. Genistein was used to pre-incubate B. japonicum cells or was applied directly into the plant growing medium. The results showed that genistein manipulation increased nodule weight and nodule nitrogen fixation under greenhouse conditions, but interactions existed among soybean cultivars, genistein concentrations and nitrate levels. Similar results were found under field conditions. Soybean yield was increased on sandy-loam soil by preincubation of B. japonicum cells with genistein. Addition of genistein beginning at the onset of nitrogen fixation also improved soybean nodulation and nitrogen fixation. Soybean cultivars had different sensitivities to genistein additiOther studies also show that temperature affected genistein and daidzein content and concentration in soybean roots. The effect of temperature varied among soybean cultivars. Some PGPR strains can mitigate the negative effects of nitrate on soybean nodulation and nitrogen fixation, however, this is influenced by soybean genotype. Applying PGPR together with genistein preincubation of B. japonicum cells improved soybean nodulation and increased yield. The level of improvement varied among soybean cultivars and PGPR strains. Preincubation of B. japonicum cells with genistein improved strain competitiveness under greenhouse, but not field conditions.
Overall, these findings suggested that both plant-to-Bradyrhizobium and Bradyrhizobium-to-plant signals play important roles in the effects of mineral N on nodulation and N fixation. Signal manipulation could partially overcome the inhibitory effects of mineral N on soybean- B. japonicum N fixation symbiosis.
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Sassi, Giovanna. "Evolutionary History Of The Angiosperm Npf1 Gene Subfamily: Duplications, Retention And Functional Implications For Root Symbioses And Development." ScholarWorks @ UVM, 2019. https://scholarworks.uvm.edu/graddis/1142.
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ABSTRACT
The success of land plants can be attributed to the evolution of beneficial associations between plant roots and soil microbes. Root-microbe mutualisms extend the range of plant nutrient acquisition delivered through the hyphal network of mycorrhiza, an ancient and widespread plant symbiosis, or by the more recent adaptive innovation of nitrogen-fixing nodule symbioses. A plant’s genetic toolkit governs its selection of beneficial symbionts and the developmental extent of these intimate interactions. However, the evolutionary origins and function for only a few symbiotic signaling components have been explored. The central aim of this dissertation is to resolve the evolutionary events that contributed two, novel genetic components for establishing root symbioses, NPF1B and NPF1C.
The Medicago truncatula (Mt) LATD/NIP/NPF1.7C transporter functions in root and nodule meristems and is a member of the large NPF1 gene subfamily. Here, I propose that LATD/NIP’s role in establishing nitrogen-fixing symbioses is derived from the ancient mycorrhizal signaling pathway. I used a comparative phylogenomic approach to investigate the evolutionary origins of the NPF1 gene across flowering plants and then asked whether diversifying or purifying selection forces influenced NPF1 gene retention. I postulated that such gene retention correlates with the adaptive traits of mycorrhizal or nitrogen-fixing root nodule symbiosis; to test this I measured trait correlation within my dataset. I found that the NPF1 phylogeny is comprised of five well-supported angiosperm clades, A, B, C, D1 and D2, that arose by successive duplications and have unequal gene retention. NPF1B is present as a single copy gene or lost entirely, while the other major NPF1 clades expanded to multiple genes within angiosperms. The NPF1A, B and C genes are under strong purifying selection while the NPF1D genes display positive, diversifying selection. My data revealed a statistically significant correlation of NPF1A, B, C, and D2, but not NPF1D1, gene retention with the ability of a species to form mycorrhizal associations. Additionally, the retention of the NPF1B, C, D1, D2, but not NPF1A, genes within a species is statistically correlated with its ability to form nitrogen-fixing symbiosis. Supporting this correlation, NPF1B genes are expressed in plant root tissues with and without mycorrhizal fungi yet available datasets failed to detect NPF1B expression in nodule tissues whereas the NPF1C genes are expressed in both symbiotic and non-symbiotic plant root tissues. In support of functional conservation, expression of legume LATD/NIP cDNAs from Cicer arietinum (Ca) and Lotus japonicus (Lj) restored, in part, the root and nodule defects of the Mtlatd mutant and resulted in the formation of peculiar hybrid lateral root-nodule structures while, in wild-type M. truncatula, significantly augmented root development. In L. japonicus, the disruption of LATD/NIP alters the number of lateral roots and nodules
My thesis data support the hypothesis for an ancestral NPF1 gene function in establishing mycorrhizal associations in angiosperms and, consequent to the monocot-eudicot divergence, co-opted this function for accommodating nitrogen-fixing symbioses in eudicots. Successive duplications then yielded the NPF1B and NPF1C genes that, by neofunctionalization and natural selection, further refined their roles in root organogenesis and symbiosis; a prerequisite for the evolution of nodule organs.
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Carlsson, Georg. "The importance of N₂ fixation in northern grasslands /." Umeå : Swedish Univ. of Agricultural Sciences, 2003. http://epsilon.slu.se/avh/2003/8858229.pdf.
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Carvalho, Adriana Macedo de. "Interações entre calos de cana-de-açucar e bactérias diazotróficas endofíticas isoladas de cana-de-açúcar." Universidade de São Paulo, 2013. http://www.teses.usp.br/teses/disponiveis/87/87131/tde-06062013-171124/.
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A cana-de-açúcar tem elevada importância econômica e agrícola. Bactérias diazotróficas possuem importante papel nos níveis de nitrogênio combinado no solo. Tornando estas bactérias as maiores fontes naturais de nitrogênio reduzido. Os gêneros bacterianos escolhidos são endofíticos, diazotróficos, isolados de cana-de-açúcar. Utilizou-se células de cana-de-açúcar na forma de calo como um modelo da interação bactéria-planta. Os experimentos com misturas bacterianas, avaliaram se dois gêneros seriam capazes de interagir, e nas contribuições às células vegetais. Pseudomonas sp. e Pantoea sp., sofreram inibição do crescimento e Enterobacter sp. foi estimulado. Pseudomonas sp. mostrou ser uma fraca competidora. Quando associadas, a morte de Pseudomonas sp. foi estimulada por Pantoea sp.. Os efeitos do calo na nitrogenase foram observados pontualmente e os no crescimento por períodos maiores. Conteúdos de EROs auxiliaram nos resultados de patogenicidade das linhagens.The sugarcane has a high economic and agricultural importance. Diazotrophs play an important role in combined nitrogen levels in the soil. Making these bacteria the highest natural sources of reduced nitrogen. The bacterial genera chosen were endophytic diazotroph isolated from sugarcane. Was used cell sugarcane in the form callus as a template of the bacteria-plant interaction. The experiments with bacterial mixtures, evaluated whether two genres would be able to interact, and contributions to plant cells. Pseudomonas sp. and Pantoea sp. suffered growth inhibition and Enterobacter sp. was stimulated. Pseudomonas sp. proved to be a weak competitor. When attached, the death of Pseudomonas sp. was stimulated by Pantoea sp .. The effects of nitrogenase were observed in callus punctually and growth for longer periods. Contents of ROS helped for the pathogenicity of strains.
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Fonouni-Farde, Camille. "Le rôle des gibbérellines dans la régulation de l’architecture racinaire chez la légumineuse modèle Medicago truncatula." Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLS079.
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L’architecture du système racinaire des légumineuses est déterminée par la croissance des racines et leur capacité à former des racines latérales et des nodosités symbiotiques fixatrices d’azote en fonction des conditions environnementales. Chez la légumineuse modèle Medicago truncatula, nous avons mis en évidence que les phytohormones gibbérellines (GAs) et leur voie de signalisation – médiée par trois protéines MtDELLAs présentant des profils d’expression redondants – jouent un rôle clé dans la régulation du développement du système racinaire. En conditions non-symbiotiques, les GAs régulent négativement la croissance racinaire en réprimant l’activité méristématique et l’élongation cellulaire, et inhibent la formation des racines latérales. En conditions symbiotiques, le rôle des GAs et de leur voie de signalisation est double : au niveau de l’épiderme, les protéines MtDELLAs régulent positivement l’infection par les bactéries symbiotiques Rhizobia en interagissant de façon directe avec la voie de signalisation des facteurs Nod bactériens. Au niveau du cortex, les GAs régulent négativement l’organogénèse des nodosités. Les phytohormones cytokinines (CKs) et leur récepteur MtCRE1 étant essentiels pour initier la nodulation, l’interaction entre les voies de signalisation GA et CK a été analysée en parallèle. Les CKs régulent le niveau de GAs bioactives en modulant l’expression des gènes de leur métabolisme de manière dépendante du récepteur aux CKs MtCRE1. Réciproquement, les GAs régulent les gènes du métabolisme CK et le niveau de CKs bioactives de manière dépendante des MtDELLAs. Par ailleurs, une forme activée de MtDELLA complémente partiellement le phénotype de nodulation du mutant cre1 et lie le promoteur de MtCRE1, indiquant que les voies de signalisation GA et CK régulent la nodulation en étroite associationLegume root system architecture is determined by both root growth and their ability to form lateral roots and nitrogen-fixing symbiotic nodules, depending on environmental soil conditions. In the model legume Medicago truncatula, we have shown that the phytohormones gibberellins (GAs) and their signaling – involving three MtDELLA proteins with redundant expression patterns – play a crucial role in the regulation of the root system development. In non-symbiotic conditions, GAs negatively regulate root growth through the repression of meristematic activity and cell elongation, and inhibit lateral root formation. In symbiotic conditions, GA and their signaling pathway play a dual role: in the root epidermis, MtDELLA proteins positively regulate infection by symbiotic bacteria Rhizobia, by directly interacting with the bacterial Nod factor signaling pathway. In the root cortex, GAs negatively regulate nodule organogenesis. The phytohormones cytokinins (CKs) and their receptor MtCRE1 being essential for the initiation of nodulation, we additionally analyzed the crosstalk between GA and CK signaling. CKs regulate the bioactive GA pool, controlling the expression of GA-metabolic genes, depending on the MtCRE1 receptor. In turn, GAs regulate CK-metabolic genes and the bioactive CK pool, depending on MtDELLAs. In addition, a dominant version of a MtDELLA partially complements the nodulation phenotype of the cre1 mutant and binds to the MtCRE1 promoter. These results indicate that GA and CK signaling pathways closely interact to regulate nodulation
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Dias, Márcio de Souza. "Diversidade e potencial de utilização de bactérias fixadoras de N2 em Brachiaria brizantha." Universidade Jose do Rosario Vellano, 2015. http://tede2.unifenas.br:8080/jspui/handle/jspui/103.
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The objective of this research was to analyze the diversity of nitrogen fixing bacteria associated and endophytic B. brizantha, study the potential the solubility of inorganic phosphates of iron and aluminum, produce acid-3-indole acetic (AIA) and to evaluate the effect of inoculation of these isolates in Brachiaria brizantha cv MG 05 Victoria. The bacteria were isolated from soil samples grown under Brachiaria and parts of plant tissue this grass, the dry and wet periods in the municipalities of Alfenas and Machado, southern Minas Gerais. Five semisolid culture media and semi-selective were used: FAM (Azospirillum amazonense), JMV (Burkholderia sp.), JNFb (Herbaspirillum spp.), LGI (A. amazonense) and NFb (Azospirillum spp.). The phosphate solubilization tests and AIA production were performed in vitro and were used as of 22 bacterial isolates selection criteria used in the inoculation of B. brizantha cv MG 5 Victoria, grown in pots containing 20 dm3 of soil. There were two cuts, in what form evaluated the following parameters: height (Al), width (LF) and leaf length (CF), number of tillers (NP), length (CR) and root dry mass (MSR) dry matter (DM), dry matter yield (PMS), neutral detergent fiber (NDF) and acid (ADF) and crude protein in dry matter (PBMS). A total of 332 isolates were obtained, most endophytic. The greatest number and diversity were from the city of Alfenas. During the rainy season was verified greater number and diversity of isolates in both municipalities, when compared to the dry season. Thirty-five isolates solubilized iron phosphate and 78 produced AIA, especially the isolated UNIFENAS 100-17, 21, 40 and 78, able to do both simultaneously. The inoculation of nitrogen fixing strains of endophytic origin and rhizospheric influenced the development of B. brizantha cv MG 5 victory, contributing to the production of MS, PMS and PBMS in the two cutting heights highlighting the UNIFENAS-100-16 isolated, 21, PBMS 78 whose content was more than 7%.
O objetivo desta pesquisa foi analisar a diversidade de bactérias diazotróficas associadas e endofíticas de Brachiaria brizantha, estudar o potencial destas em solubilizar fosfatos inorgânicos de ferro e alumínio, produzir ácido-3-indolacético (AIA) e avaliar o efeito da inoculação destes isolados em Brachiaria brizantha cv MG 05 Vitória. As bactérias foram isoladas de amostras de solos cultivados sob B. brizantha e partes de tecido vegetal desta gramínea, nos períodos seco e chuvoso, nos municípios de Alfenas e Machado, Sul de Minas Gerais. Foram utilizados cinco meios de cultura semissólidos e semisseletivos: FAM (Azospirillum amazonense), JMV (Burkholderia sp.), JNFb (Herbaspirillum spp.), LGI (A. amazonense) e NFb (Azospirillum spp.). Os testes de solubilização de fosfato e produção de AIA foram realizados in vitro e foram utilizados como critério de seleção dos 22 isolados bacterianos utilizados na inoculação de B. brizantha cv MG 5 Vitória, cultivada em vasos contendo 20 dm3 de solo. Foram realizados dois cortes, em que foram avaliados os seguintes parâmetros: altura (Al), largura (LF) e comprimento da folha (CF), número de perfilhos (NP), comprimento (CR) e massa seca da raiz (MSR), matéria seca (MS), produtividade de matéria seca (PMS), fibra em detergente neutro (FDN) e ácido (FDA) e a proteína bruta na matéria seca (PBMS). Foi obtido um total de 332 isolados, sendo a maioria endofíticos. O maior número e diversidade foram provenientes do município de Alfenas. No período chuvoso foi verificado maior número e diversidade de isolados em ambos os Municípios, quando comparado ao período da seca. Trinta e cinco isolados solubilizaram fosfato de ferro e 78 produziram AIA, destacando-se os isolados UNIFENAS 100-17, 21, 40 e 78, capazes de desempenhar ambas as funções simultaneamente. A inoculação de estirpes diazotróficas de origem endofíticas e rizosféricas influenciaram no desenvolvimento de B. brizantha cv MG 5 Vitória, contribuindo para a produção de MS, PMS e PBMS nas duas alturas de corte destacando-se os isolados UNIFENAS-100-16, 21, 78 cujo teor de PBMS foi superior a 7%.
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Keller, Jean. "La symbiose fixatrice d'azote au sein du genre Lupinus : histoire évolutive, aspects fonctionnels et gènes symbiotiques dans un contexte de spécificité hôte-symbiote." Thesis, Rennes 1, 2017. http://www.theses.fr/2017REN1B036.
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La symbiose entre les légumineuses et les Rhizobiacées est la source d’azote fixé la plus importante pour le bon fonctionnement des écosystèmes naturels et agricoles. Très étudiée chez des légumineuses modèles, certains aspects de cette interaction restent peu connus ; c’est le cas des mécanismes génétiques et fonctionnels qui contrôlent la spécificité hôte-symbiote. Il n’y a que peu d’études globales consacrées à ce phénomène, et les gènes symbiotiques sont très peu connus chez les espèces non-modèles. Dans ce contexte, nous avons étudié un cas de changement de spécificité symbiotique remarquable chez des espèces phylogénétiquement proches du genre Lupinus (Fabacées). Tout d’abord, la reconstruction et l’analyse de génomes chloroplastiques complets a permis de camper le cadre évolutif de la symbiose en générant de nouveaux marqueurs d’intérêt pour clarifier la phylogénie et l’évolution des lupins. A partir d’une expérimentation d’inoculation croisée impliquant trois espèces de lupins méditerranéens et deux souches compatibles et incompatibles de Bradyrhizobium, une approche RNA-Seq a permis de produire les premiers nodulomes de lupin et d’identifier les gènes symbiotiques. L’analyse des gènes différentiellement exprimés a montré que la spécificité symbiotique affecte non seulement la voie de signalisation et de régulation de la symbiose, mais également une diversité de voies métaboliques associées. Enfin, l’étude de la dynamique évolutive et fonctionnelle de quelques gènes a mis en évidence l’impact et l’importance des phénomènes de duplication aux différents niveaux de la cascade génétique symbiotiqueLegumes-Rhizobia symbiosis is the most important fixing nitrogen source for the good functioning of both natural and agricultural ecosystems. Although, it is extensively studied in model legumes, some aspects of this interaction remain unclear, such as the genetic and functional mechanisms controlling the host-symbiont specificity. Large scale studies of this process are scarce and symbiotic genes are not well described in non-model species. In this context, the effect of symbiotic specificity was investigated in phylogenetically close relative species belonging to the Lupinus genus (Fabaceae). First, the reconstruction and analysis of complete chloroplast genomes allowed us to generate new and useful markers for clarifying the Lupinus phylogeny in order to lighten the evolutionary context of the symbiosis. Following a cross-inoculation experiment of three Mediterranean lupine species with two compatible or incompatible Bradyrhizobium strains, a RNA-Seq approach allowed the reconstruction of the first lupine nodulomes and the identification of lupine symbiotic genes. The analysis of differentially expressed genes revealed that the symbiotic specificity affects not only the signalling and regulatory symbiotic pathways, but also diverse associated metabolic pathways. Finally, evaluating the evolutionary and functional dynamics of genes highlighted the importance of gene and genome duplication events at different steps of the symbiotic genetic pathway
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Liu, Shengbin. "The roles of the NOOT-BOP-COCH-LIKE genes in plant development and in the symbiotic organ identity." Thesis, université Paris-Saclay, 2020. http://www.theses.fr/2020UPASB005.
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Les gènes NODULE-ROOT de Medicago truncatula, BLADE-ON-PETIOLE d’Arabidopsis thaliana et COCHLEATA de Pisum sativum font partie d'un clade spécifique NOOT-BOP-COCH-LIKE1 (NBCL1) hautement conservé et qui appartient à la famille de gènes NON-EXPRESSOR OF PATHOGENESIS RELATED PROTEIN1 LIKE. Chez les légumineuses, les membres du clade NBCL1 sont connus comme les principaux régulateurs de l'identité des organes symbiotiques (nodules). Les membres du clade NBCL2 (MtNOOT2) jouent également un rôle clé dans l'établissement et le maintien de l'identité de l’organe symbiotique, en redondance avec les gènes NBCL1. Il a également été démontré que ces gènes végétaux NBCL sont impliqués dans l'abscission. Les gènes NBCL sont également conservés chez les plantes monocotylédones chez lesquelles ils contrôlent différents aspects du développement. Ce travail de thèse vise à mieux comprendre les rôles des gènes NBCL1 et NBCL2 dans le développement des plantes légumineuses et chez Brachypodium et à découvrir de nouveaux acteurs moléculaires impliqués dans la régulation de l'identité des nodules dépendante de NBCL1, en utilisant de nouveaux mutants d'insertion TILLING et Tnt1 chez deux espèces de légumineuses (Medicago et Pisum). En outre, nous avons utilisé les mutations KO CRISPR chez Brachypodium pour mieux comprendre leur rôle chez les plantes monocotylédones. Ce travail de thèse a permis d'élucider les nouvelles fonctions des gènes NBCL1 dans le développement des tiges et l'architecture des plantes. Nous avons également révélé que les membres du clade NBCL2, spécifique aux légumineuses, fonctionnent de manière redondante avec le clade NBCL1 et jouent des rôles importants dans le développement des feuilles, des stipules, des inflorescences et des fleurs. De plus, nous avons montré un rôle dans le développement, l'établissement et le maintien de l'identité des nodosités, et par conséquent dans le succès et l'efficacité de l'association symbiotique. Dans cette thèse, nous avons également exploré les rôles des gènes NBCL BdUNICULME4 et BdLAXATUM-A, dans le développement de B. distachyon à l'aide de doubles mutants. Nous avons confirmé les résultats précédents et révélé une nouvelle fonction pour ces deux gènes dans l'architecture des plantes, la formation des ligules et des inflorescences, ainsi que dans la teneur en lignine. Ce travail de thèse a finalement permis l'identification et la caractérisation de nouveaux mutants pour les gènes de M. truncatula ALOG (Arabidopsis LSH1 et Oryza G1). Les protéines ALOG sont des partenaires d'interaction potentiels pour les NBCLs. Nous avons montré que certains membres ALOG jouent un rôle important dans le développement des nodules et des organes aériens. Dans l'ensemble, ce travail de thèse suggère qu'au cours de l'évolution, le programme de développement des nodules a été recruté à partir de programmes de régulation préexistants pour le développement et l'identité des nodositésThe Medicago truncatula NODULE-ROOT, the Arabidopsis thaliana BLADE-ON-PETIOLE, and the Pisum sativum COCHLEATA genes are members of a highly conserved NOOT-BOP-COCH-LIKE1 (NBCL1) specific clade that belongs to the NON-EXPRESSOR OF PATHOGENESIS RELATED PROTEIN1 LIKE gene family. In legumes, the members of this NBCL1 clade are known as key regulators of the symbiotic organ identity. The members of the NBCL2 clade (MtNOOT2) also play a key role in the establishment and maintenance of the symbiotic nodule identity, redundantly with NBCL1 while without significant phenotype alone. These NBCL plant genes were also shown to be involved in abscission. In addition, NBCL genes are also conserved in monocotyledon plants in which they also control different aspects of development. The present thesis work aims to better understand the roles of the NBCL1 and NBCL2 genes in development in both legume and Brachypodium plants and to discover new molecular actors involved in the NBCL1-dependent regulation of the nodule identity using novel TILLING and Tnt1 insertional mutants in two legume species, Medicago, and Pisum. In addition we used CRISPR knock-out mutations in Brachypodium to better understand their roles in monocotyledon plants. This thesis work unraveled new functions of the NBCL1 genes in plant shoot development and plant architecture. We also revealed that the members of the legume-specific NBCL2 redundantly function with NBCL1 sub-clade and play important roles in leaf, stipule, inflorescence and flower development. In addition we showed a role in nodule development, identity establishment and maintenance, and consequently in the success and efficiency of the symbiotic association. In this thesis, we also explored the roles of the highly conserved NBCL genes, BdUNICULME4 and BdLAXATUM-A, in the development of B. distachyon using double mutants. We confirmed previous results and reveal a new function for these two genes in plant architecture, ligule and inflorescence formation, and also lignin content. This thesis work has finally allowed the identification and the characterization of new mutants for M. truncatula ALOG (Arabidopsis LSH1 and Oryza G1) genes. ALOG proteins are potential interacting partners for NBCL. We showed that some ALOG members play important roles in nodule and aerial organ development. Altogether, this thesis work suggests that during evolution, the nodule developmental program was recruited from pre-existing regulatory programs for nodule development and identity
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Magne, Kévin. "The roles of the NOOT-BOP-COCH-LIKE genes in the symbiotic organ identity and in plant development." Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLS482/document.
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L’association symbiotique entre les légumineuses et les rhizobia aboutit à la formation de la nodosité fixatrice d’azote. Cet organe symbiotique généré de-novo permet l’hébergement intracellulaire des rhizobia qui, grâce à leurs activités nitrogénase,réduisent l’azote atmosphérique en ammonium, une forme de l’azote directement assimilable par la plante hôte.Les mécanismes moléculaires sous-jacents à la reconnaissance entre les deux partenaires symbiotiques, au processus d’infection et à l’organogénèse de la nodosité sont bien décrits, cependantl’établissement et la maintenance de l’identité de cet unique organe souterrain restent incompris.Les gènes NODULE-ROOT de Medicago truncatula, BLADEON-PETIOLE d’Arabidopsis thaliana et COCHLEATA de Pisumsativum sont membres du clade spécifique très conservé NOOTBOP-COCH-LIKE1 (NBCL1) qui fait partie de la famille des gènesNON-EXPRESSOR OF PATHOGENESIS RELATED PROTEIN1-LIKE. Chez les légumineuses, les membres de ce clade NBCL1 sont connus comme étant des régulateurs clés de l’identité de l’organe symbiotique.Mon travail de thèse a eu pour but d’améliorer la compréhension des rôles des gènes NBCL1, à la fois chez des espèces formant des nodosités indéterminées et déterminées, ainsi que de découvrir de nouveaux acteurs moléculaires impliqués dans l’identité de la nodosité dont la régulation est dépendante des gènesNBCL1, essentiellement par l’utilisation de mutants TILLING, Tnt1et LORE1 originaux chez trois espèces de légumineuses: la luzerne tronquée, le petit pois et le lotier.Ce travail rapporte essentiellement l’identification et la caractérisation de nouveaux mutants affectés dans des gènes qui font partie d’un second sous-clade NBCL2 spécifique des légumineuses.Nous avons révélé que les membres de ce sous-clade spécifique des légumineuses NBCL2 jouent d’importants rôles dans le développement de la nodosité, dans l’établissement et la maintenance de l’identité de la nodosité et par conséquence dans le succès et l’efficacité de l’association symbiotique.Ce travail suggère aussi qu’au cours de l’évolution, le programme de développement de la nodosité a recruté des mécanismes de régulations préexistants afin de réguler le développement de la nodosité et son identité, tel que le module de régulation impliquant des interactions entre des protéines NBCL et des facteurs de transcriptions basic leucine zipper de type TGACG. Nous avons identifié le facteur de transcription MtPERIANTHIA-LIKE, comme un premier partenaire protéique interagissant avec des protéines NBLC dans un contexte de nodosité symbiotique. Les gènes NBCL sont aussi impliqués dans les réseaux de régulations qui contrôlent le développement et le déterminisme de nombreux organes végétatifs et reproductifs aériens et sont également impliqués dans la capacité d’abscission de ces organes.Finalement, ce travail thèse a eu pour objectif d’explorer les rôles de ces gènes NBCL très conservés, dans le développement de la graminée non-domestiquée, Brachypodium distachyonThe symbiotic interaction between legumes andrhizobia results in the formation of a symbiotic nitrogen fixingnodule.This de-novo generated symbiotic organ allows the intracellularaccommodation of the rhizobia which reduces through theirnitrogenase activity the atmospheric nitrogen in ammonium, anitrogen form usable by the host plant.The molecular mechanisms underlying the symbiotic partnersrecognition, the infection process and the nodule organogenesis arewell described, however the identity establishment and maintenanceof this unique underground organ remain mis-understood.The Medicago truncatula NODULE-ROOT, the Arabidopsisthaliana BLADE-ON-PETIOLE and the Pisum sativumCOCHLEATA genes are members of a highly conserved NOOTBOP-COCH-LIKE1 (NBCL1) specific clade that belongs to theNON-EXPRESSOR OF PATHOGENESIS RELATED PROTEIN1-LIKE gene family. In legumes, the members of this NBCL1 cladeare known as key regulators of the symbiotic nodule identity.The present thesis work aims to better understand the roles of theNBCL1 genes, in both indeterminate and determinate nodule formingspecies and to discover new molecular actors involved in theNBCL1-dependent regulation of the nodule identity essentially usingnovel TILLING, Tnt1 and LORE1 insertional mutants in three legumespecies, Medicago, Pisum and Lotus.This thesis work has allowed the identification and thecharacterization of new mutants for genes belonging to a secondarylegume-specific NBCL2 sub-clade. We revealed that the members ofthis legume-specific NBCL2 sub-clade play important roles in noduledevelopment, identity establishment and maintenance, andconsequently in the success and in the efficiency of the symbioticassociation.This thesis work also shows that during evolution, the noduledevelopmental program has recruited pre-existing regulatorymechanisms for the nodule development and identity, such as theregulatory module involving interactions between NBCL proteins andTGACG type basic leucine zipper transcription factors. We identifiedthe transcription factor, MtPERIANTHIA-LIKE, as a first interactingpartner of NBCL proteins in a context of root nodule symbiosis.NBCL genes are also involved in the regulatory networks thatcontrol the development and the determinacy of many abovegroundvegetative and reproductive organs and were also shown as involvedin their abscission ability.In this thesis we also explored the roles of these highly conservedNBCL genes in the development of the non-domesticated grass,Brachypodium distachyon
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Aït-Salem, Elhosseyn. "Etude de la signalisation contrôlant l’accommodation intracellulaire au cours de la symbiose Medicago/Sinorhizobium The Multiple Faces of the Medicago-Sinorhizobium Symbiosis Control of the ethylene signaling pathway prevents plant defenses during intracellular accommodation of the rhizobia." Thesis, université Paris-Saclay, 2020. http://www.theses.fr/2020UPASS096.
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Les légumineuses en milieu carencé en azote, établissent une relation symbiotique avec les bactéries du sol appelées rhizobia. Cette interaction conduit à la formation d’un nouvel organe racinaire, la nodosité. Au sein de celle-ci, les rhizobia se différencient en bactéroïdes fixant l’azote atmosphérique au profit de la plante. La colonisation massive et chronique des cellules symbiotiques de nodosités par les rhizobia ne déclenche aucune réaction de défense visible. Au laboratoire nous avons isolé deux mutants symbiotiques développant des réactions de défense dans les nodosités de Medicago truncatula indiquant qu’il existe un contrôle strict de l’immunité dans cet organe. L’objectif de cette thèse est de comprendre comment l’immunité symbiotique contrôle les voies de signalisation hormonales de défense afin d’héberger le partenaire symbiotique et de trouver de nouveaux outils pour mieux comprendre les mécanismes de défense. Pour cela, des approches moléculaires, pharmacologiques et génétiques sont utilisées. Les résultats obtenus dans cette thèse suggèrent que les mécanismes de défense adoptés par M. truncatula varient en fonction de l’écotype de la plante. L’écotype A17 exploite deux voies de résistance : la voie de la sénescence et la voie des réactions de défense. Cependant, l’écotype R108 n’exploite que la voie des réactions de défense. Ce travail suggère également que chez M. truncatula A17, la protéine SymCRK réprime la voie de signalisation de l’acide jasmonique qui conduit au déclenchement de la sénescence, tandis que la protéine DNF2 réprime principalement la voie de signalisation de l’acide salicylique qui conduit au déclenchement des réactions de défense et aussi réprime secondairement la voie acide jasmonique. Chez M. truncatula R108, les deux protéines SymCRK et DNF2 contrôlent les voies de signalisation de l’acide salicylique et de l’éthylène, avec DNF2 contrôlant préférentiellement la voie acide salicylique et SymCRK contrôlant préférentiellement la voie éthylène. Cette thèse suggère aussi l’implication des protéines R dans le contrôle de l’accommodation intracellulaire des rhizobia. Un gène CNL-5 semble être impliqué dans le contrôle de l’infection des cellules symbiotiques, et deux autres gènes CNL-4 et TNL-2 semblent être impliqués dans le contrôle de l’efficacité de l’infection. Finalement, cette thèse a permis d’isoler une souche bactérienne E. adhaerens, capable se comporter comme un symbiote ou comme un pathogène pour plusieurs espèces de MedicagoWhen grown under limited nitrogen resources, legumes establish a symbiotic relationship with soil bacteria called rhizobia. This interaction leads to the formation of a new root organ, the nodules. Within nodules, rhizobia differentiate into bacteroids and fix atmospheric nitrogen for the plant. The massive and chronic colonization of nodule symbiotic cells by the rhizobia does not trigger any visible defense reactions. In the laboratory, we previously isolated two symbiotic mutants developing defense reactions in Medicago truncatula nodules, indicating a strict control of the nodule immunity. The thesis project aimed first to understand the relationship between symbiotic genes and immunity mediated by defense hormones and second to find new tools to help to better understand nodules defense mechanisms. For this, molecular, pharmacological and genetic approaches were used. The results obtained in this thesis suggest that the defense mechanisms adopted by M. truncatula vary depending on the plant ecotypes. The A17 ecotype uses two resistance pathways; senescence and defense reactions. While, the R108 ecotype uses defense reactions pathway to fight against rhizobia. This work also suggests that in M. truncatula A17, the SymCRK protein represses jasmonic acid signalling. This work also suggests that in M. truncatula A17, the SymCRK protein represses the jasmonic acid signaling pathway involved in senescence triggering. In contrast, the DNF2 protein mainly represses the salicylic acid signaling pathway involved in defense reactions and also represses the JA pathway. In M. truncatula R108, the two proteins SymCRK and DNF2 control salicylic acid and ethylene signaling pathways involved in triggering defense reactions. DNF2 controls the salicylic acid pathway more than the ethylene signaling pathway, while, SymCRK controls more the ethylene pathway than the salicylic acid signaling pathway in nodules. This thesis also suggests the involvement of R proteins in the control of intracellular accommodation of rhizobia. The intracellular receptor CNL-5 appears to be involved in controlling the infection of symbiotic cells and the receptors CNL-4 and TNL-2 genes appear to be involved in controlling the infection efficacy of the symbiotic cells. Finally, this thesis allowed the identification of a new bacterial strain E. adhaerens, capable of behaving as a symbiont or as a pathogen for several Medicago species. This can be used as a tool to study the nodules defense induction and to understand the rhizobia intracellular accommodation in symbiotic cells
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Tozer, Wade. "Nitrogen isotope variation in the environment : implications for interpretation /." 2006. http://adt.waikato.ac.nz/public/adt-uow20070124.124737/index.html.
Full text
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Ndiaye, Aissatou. "Impact of a red clover winter cover crop on carbon and nitrogen mineralization by microorganisms in soil aggregates." Thesis, 1998. http://hdl.handle.net/1957/33785.
Full textAbstract:
Although legumes have been widely studied for their nitrogen-fixing ability, it
is uncertain to what extent legume cover crops achieve their nitrogen-fixing potential
under the climatic conditions encountered in western Oregon. Furthermore, it is
unknown what factors control the proportions of legume cover crop N that are either
sequestered into soil organic matter, or that contribute to the N requirements of the
following summer crop. Soil was sampled in mid-September 1997, after harvest of a
summer broccoli crop, from plots located at the North Willamette Research and
Extension Center, Aurora, Oregon. Soil was sampled from main plots that had been
either winter cover cropped with red clover (LN��� and LN���) or fallowed during the
winter period (FN��� and FN���), and specifically from sub-plots in which the following
summer crop had received either zero (N���) or an intermediate (N���) rate of N fertilizer
as urea. Levels of total organic carbon (TOC), total Kjeldahl nitrogen (TKN), and
readily mineralizable C and N were measured in both whole soil samples and in
different aggregate-size classes (<0.25, 0.25-0.5
0.5-1.0, 1.0-2.0, and 2-5mm) prepared by dry sieving the soil. Aggregate size-class
distribution was not affected by the cover crop treatment. Although there was no significant effect of cover crop treatment on either TKN or TOC levels in whole soil samples, TOC levels were consistently higher in the small aggregate size-classes <1 mm of the fallow than the legume treatment. There was a significantly higher level of mineralizable C in the <0.25 mm size class of the legume than the fallow treatment. There was a trend for the level of mineralizable N to be greater in soil from the legume than the fallow treatment. However, N fertilizer had a significant positive effect on the level of readily mineralizable N in both fallow and legume cover-cropped treatments, it had a negative effect on TKN levels among all aggregate-size classes. There were differences in the levels of mineralizable N measured among the aggregate-size classes, and immobilization of N between 20 and 40 days of incubation also differed among the aggregate-size classes.Graduation date: 1999
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Kifle, Medhin Hadish. "Development of free-living diazotrophic (FLD) inoculants and their effects on crop growth." Thesis, 2008. http://hdl.handle.net/10413/5277.
Full textAbstract:
In this study several free-living diazotrophs (FLD) were isolated and screened for their
nitrogen fixing ability on a range of crops grown in greenhouse, hydroponics and field trials. Rhizosphere isolates of free-living diazotrophs (FLD) may be effective biofertilizer inoculants, and may improve plant health where crops are grown with little or no fertilizer, as is the case in the Developing World. FLD isolates from rhizospheric soils in KwaZulu-Natal were assessed by growing them on N-free media, which is a key isolation method. They were then evaluated for their nitrogenase activity by quantifying ethylene production from acetylene by gas chromatography (GC). The free living isolates that produced greater quantities of ethylene were detected by an acetylene reduction assay (ARA). These were
further assessed for colony formation on N-free media with different carbon sources, and at a range of temperatures (20, 25 and 300C) and pH values (6.0, 7.0 and 8.0). Isolates G3 and L1 were identified using DNA sequencing by Inqaba Biotechnical Industries (Pty) Ltd as Burkholderia ambifaria Coenye et al, and Bacillus cereus Frankland, respectively. These isolates grew significantly better on an ethanol medium, at temperatures of 20, 25 and 300C and pHs of 6.0, 7.0 and 8.0. Isolates B3 (Burkholderia sp.) and D6 (Bacillus cereus Frankland) also grew well on an ethanol medium, but only at 200C and at a pH of 6.0 and 7.0, respectively, while Isolate E9 (Burkholderia cepacia Frankland) grew well on an ethanol medium only at 300C, and pH 6.0 and 7.0. Temperature and pH strongly influence FLD growth on N-free media using different carbon sources. Further trials were conducted to screen the best isolates under greenhouse condition, using both seed treatments and drenching application techniques onto several crops. The drenching application resulted in an increase in the growth and N-total of all the evaluated crops, relative to an unfertilized control. Growth and N-total of maize and sorghum increased with seed treatments, but did not increase the growth of lettuce and zucchini. Drenching of FLD isolates at 106cfu ml-1, applied on weekly basis, resulted in an increase in the growth of lettuce. Increased doses and frequency of application of the FLD bacteria resulted in a decrease in lettuce growth. This led to the conclusion that application of FLD bacteria at high doses and short intervals may create a situation where the applied FLD
bacteria and the resident rhizosphere microbes compete for root exudates. High doses at low frequencies and low doses at high frequencies may be more effective on lettuce.
Inoculation of Isolate L1 (B. cereus) at 106cfu ml-1 or in combination with Eco-T®
(Trichoderma harzianum Rifai), significantly increased growth of lettuce. This result may
have been due to nitrogen fixation, or to secretion of growth promoting substances by both
the FLD and T. harzianum, and to biocontrol effects of Eco-T®. Application of Isolate L1
(B. cereus) at 106cfu ml-1 with or without Eco-T® was an effective tool for enhancing plant
growth and nitrogen fixation. An FLD, Isolate L1 (B. cereus), was applied to lettuce plants together with a complete
hydroponics fertilizer at 25% strength (Ocean Agriculture 3:1:3 (38) Complete), with the N level at 25mg l-1. These plants grew significantly better than the control plants grown on 25%
of normal NPK fertilization, or with an inoculation of L1 alone. This indicates that it may be
possible to integrate FLD applications with the application of low levels of commercial
fertilizers, which is what resource poor farmers can afford.Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2008.
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"Disruption of nitrogen fixing symbiosis by pesticides and endocrine disrupting chemicals." Tulane University, 2002.
Find full textAbstract:
A subset of synthetic chemicals present in the environment, such as organochlorine pesticides and plastics by-products, are able to mimic endogenous estrogen-induced signaling in representatives of each vertebrate class; as such, they are termed endocrine disrupting chemicals (EDCs). Similarly, estrogen-like signaling has also been observed when vertebrates are exposed to plant products called phytoestrogens. Previous research has focused on what effects synthetic and plant estrogens may have on estrogen receptor (ER) function and estrogenic signaling in humans and wildlife, while the evolutionary signaling targets of phytoestrogens, namely soil bacteria capable of nitrogen-fixing symbiosis with leguminous plants, had not been studied to determine if EDCs may interfere with crucial phytoestrogen-bacterial signaling Here I show that, in much the same way estrogen signaling with ERs is disrupted by the presence of EDCs, phytoestrogen signaling with its natural target, soil bacterial nodulation D (NodD) transcriptional activator proteins, is also disrupted by a similar profile of endocrine disrupting pesticides and pollutants. The similarities between ERs and NodD proteins may be explained by convergent evolution in which both NodD and ER separately evolved to adapt to the presence of natural estrogenic ligands, both vertebrate estrogens and phytoestrogens, as well as synthetic chemicals found in the environment that are able to mimic the natural ligands of both ER and NodD. I hypothesize that synthetic environmental compounds with similar structural properties to phytoestrogens, such as EDCs, may disrupt phytoestrogen-NodD signaling My studies herein show that the presence of a subset of EDCs: (1) inhibit phytoestrogen-NodD signaling and reduce the activation of key nod genes as measured in vitro, (2) the same EDCs tested in an in vivo plant-bacterial ecosystem inhibit symbiosis, nitrogen fixation, and adversely affect crop yield in treated plants. I demonstrate that both estrogenic and NodD signaling systems are adversely affected by the presence of a similar profile of EDCs at environmentally relevant concentrations. Therefore, I conclude that signaling components used by plants and pathways present in bacteria may have previously unrecognized similarities to those present in animals, and both of these systems are vulnerable to endocrine disruptors present in the environmentacase@tulane.edu
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Wiebkin, Suzanne Constance. "The enhancement of wheat growth after inoculation with free-living nitrogen-fixing bacteria." Thesis, 2003. http://hdl.handle.net/2440/115252.
Full textAbstract:
Focuses on the selection of bacteria for use as inoculants to assist in early establishment of whet in environments where winter rainfall is variable. This evokes the concept of early development of root growth. The beneficial effects on plants of mixed N₂ -fixing bacteria from 3 local soils were compared to identify soils from which to identify potential inoculants. Experiments to identify dominant bacterial species within the mixed N₂-fixing assemblage were carried out using fatty acid profiles from fatty acid methyl ester analysis (GC-FAME) and 3 were selected to be co-inoculated onto wheat. Results of inoculation indicated that raised levels of plant N in the inoculated treatments could be attributed to N2 fixation by the bacteria.Thesis (Ph.D.) -- University of Adelaide, Dept. of Soil and Water, 2003
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Rambau, Mashudu Daniel. "The effects of fertilization with bio-digester slurry and the inclusion of carbohydrate additives at ensiling on the nutritive value of Napier grass (pennisetum purpureum) silage." Diss., 2016. http://hdl.handle.net/11602/696.
Full textAbstract:
MSCAGR (Animal Science)Department of Animal Science
The objective of the study was to determine the effects of fertilisation with bio-digester slurry and the inclusion of carbohydrate additives at ensiling on the fermentation characteristics, chemical composition, ruminal degradability, and in vitro digestibility of Napier grass silage. Napier grass planted at the School of Agriculture Experimental Farm, University of Venda in 5 m x 4 m plots replicated three times in a completely randomised design and was irrigated with either biodigester slurry or no bio-digester slurry (tap water) for a period of 12 weeks. After 12 weeks, the Napier was freshly cut and ensiled for 90 days in 1 litre glass jars in a 2 (Control - tap water and slurry irrigation) x 4 (No additive, molasses, maize meal and brown sugar) factorial arrangement. Fermentation quality and nutritive composition were determined using standard protocols. The dry matter (DM) and crude protein (CP) ruminal degradability was determined in sacco by incubating feed samples in nylon bags (external dimension: 6 × 12 cm, pore size of 46 μm) in the rumen in three Bonsmara steers fitted with rumen cannulae for 0, 6, 12, 24, 48, 72, 96 and 120 hours (h). Parameters to describe the dynamics of ruminal degradability of DM and CP were obtained by fitting the data on the exponential equation P = a + b (1 - e-ct) using the NEWAY computer program, where “a” is the rapidly degradable fraction, “b” is the slowly degradable fraction and “c” is the outflow rate. The in vitro DM and CP degradability of rumen undegradable residue collected after 12, 24 and 48 h incubation was determined by sequential digestion in pepsin (abomasal) and pancreatin (small intestine) solutions. Fertilisation with bio-digester slurry increased (P <0.05) CP content of fresh cut Napier grass pre-ensilage. Bio-digester slurry fertilisation with molasses inclusion improved (P <0.05) the silage DM content which improved (P >0.05) fermentation characteristics with pH of 4.2 and lowest NH3-N of 13.3 g/kg. Other chemical compositions and fermentation characteristics were not affected (P >0.05) due to fertilisation x additives treatment combinations. No bio-digester slurry fertilisation with maize meal inclusion increased (P <0.01) DM degradability at 0 h incubation. As time progressed to 24 h, no biodigester slurry fertilisation with no additive included reduced (P <0.01) DM degradability with no difference (P >0.05) on other treatments. Potential DM degradability (a + b) of no bio-digester slurry fertilisation with no additive inclusion silage was reduced (P <0.01). The reduction was associated with low levels (P <0.01) of slowly degradable fraction “b”. In vitro DM and CP digestibility were not affected (P >0.05) due to fertilisation x additives treatment combinations. In conclusion, bio-digester slurry application improved the quality of fresh cut Napier grass, with the combination of bio-digester slurry fertilisation and molasses addition yielding the best silage quality.