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Nodulation and nitrogen fixation

Sadam D V Satyanarayana, M S R Krishna, Pindi Pavan Kumar, Sirisha Jeereddy
Symbiosis is a complex genetic regulatory biological evolution which is highly specific pertaining to plant species and microbial strains. Biological nitrogen fixation in legumes is a functional combination of nodulation by nod genes and regulation by nif, fix genes. Three rhizobial strains ( Rhizobium leguminosarum , Bradyrhizobium japonicum , and Mesorhizobium ciceri ) that we considered for in silico analysis of nif A are proved to be the best isolates with respect to N2 fixing for ground nut, chick pea and soya bean (in vitro) out of 47 forest soil samples...
December 2018: Journal, Genetic Engineering & Biotechnology
Małgorzata Marczak, Kamil Żebracki, Piotr Koper, Anna Turska-Szewczuk, Andrzej Mazur, Jerzy Wydrych, Magdalena Wójcik, Anna Skorupska
In this study, functional characterization of the mgl2 gene located closely to the Pss-I exopolysaccharide biosynthesis region in Rhizobium leguminosarum bv. trifolii TA1 was described. The hypothetical protein encoded by the mgl2 gene was found to be similar to methyltransferases. Protein homology/template-based modeling facilitated prediction of the Mgl2 structure, which vastly resembled class I methyltransferases with a SAM-binding cleft. The Mgl2 protein was engaged in exopolysaccharide but not lipopolysaccharide synthesis...
January 25, 2019: Molecular Plant-microbe Interactions: MPMI
Aaron J Ogden, Jacqueline M McAleer, Michael L Kahn
Symbiotic nitrogen fixation (SNF) in the interaction between the soil bacteria Sinorhizobium meliloti and legume plant Medicago sativa is carried out in specialized root organs called nodules. During nodule development, each symbiont must drastically alter their proteins, transcripts and metabolites in order to support nitrogen fixation. Moreover, bacteria within the nodules are under stress, including challenges by plant antimicrobial peptides, low pH, limited oxygen availability, and strongly reducing conditions, all of which challenge proteome integrity...
January 22, 2019: Journal of Bacteriology
Diana I Trujillo, Kevin A T Silverstein, Nevin D Young
Symbiotic nitrogen fixation in legumes is mediated by an interplay of signaling processes between plant hosts and rhizobial symbionts. In legumes, several secreted protein families have undergone expansions and play key roles in nodulation. Thus, identifying lineage-specific expansions (LSEs) of nodulation-associated genes can be a strategy to discover candidate gene families. Using bioinformatic tools, we identified 13 LSEs of nodulation-related secreted protein families, each unique to either Glycine, Arachis or Medicago lineages...
January 21, 2019: New Phytologist
Katherine E Muller, R Ford Denison
Resources that microbial symbionts obtain from hosts may enhance fitness during free-living stages when resources are comparatively scarce. For rhizobia in legume root nodules, diverting resources from nitrogen fixation to polyhydroxybutyrate (PHB) has been discussed as a source of host-symbiont conflict. Yet, little is known about natural variation in PHB storage and its implications for rhizobial evolution. We therefore measured phenotypic variation in natural rhizobia populations and investigated how PHB might contribute to fitness in the free-living stage...
December 2018: Royal Society Open Science
Darian N Smercina, Sarah E Evans, Maren L Friesen, Lisa K Tiemann
Free-living nitrogen-fixation (FLNF) in the rhizosphere, or N-fixation by heterotrophic bacteria living on/near root surfaces, is ubiquitous and a significant source of N in some terrestrial systems. FLNF is also of interest in crop production as an alternative to chemical fertilizer, potentially reducing production costs and ameliorating negative environmental impacts of fertilizer N additions. Despite this interest, a mechanistic understanding of controls (e.g. carbon, oxygen, nitrogen, and nutrient availability) on FLNF in the rhizosphere is lacking, but necessary...
January 18, 2019: Applied and Environmental Microbiology
Gaofei Jiang, Juan Yang, Xingjuan Li, Yajun Cao, Xiaomeng Liu, Jun Ling, Hui Wang, Zengtao Zhong, Jun Zhu
Reactive oxygen species (ROS) are not only toxic products of oxygen from aerobic metabolism or stress but also signalling molecules involved in the development of the legume-Rhizobium symbiosis. To assess the importance of alkyl hydroperoxide reductase (AhpCD) in the nitrogen-fixating bacterium Azorhizobium caulinodans, we investigated the phenotypes of the ∆ahpCD strain with regards to ROS resistance and symbiotic interactions with Sesbania rostrata. The ∆ahpCD strain was notably more sensitive than its parent strain to hydrogen peroxide (H2O2) but not to two organic peroxides, in the early log phase...
January 17, 2019: FEMS Microbiology Letters
Yali Sun, Zefeng Wu, Yujie Wang, Jieyu Yang, Gehong Wei, Minxia Chou
The establishment of symbiosis between legume and rhizobium results in the formation of nodule. Phytocyanins (PCs) are a class of plant specific blue copper proteins, playing critical roles in plant development including nodule formation. Although a few PC genes have been isolated from nodules, their functions are still unclear. Here, we performed a genome-wide identification of PC family in seven sequenced legume species (Medicago truncatula, Glycine max, Cicer arietinum, Cajanus cajan, Lotus japonicus, Vigna angularis and Phaseolus vulgaris) and found PCs experienced a remarkable expansion in M...
January 15, 2019: Plant & Cell Physiology
Francisco X Nascimento, Maria J Tavares, Márcio J Rossi, Bernard R Glick
Ethylene plays an important role in regulating the rhizobial nodulation process. Consequently, numerous strains of rhizobia possess the ability to decrease plant ethylene levels by the expression of the enzyme 1-aminocyclopropane-1-carboxylate (ACC) deaminase or via the production of rhizobitoxine, thus, leading to an increased ability to nodulate leguminous plants. Nevertheless, not much is understood about the prevalence of these ethylene modulation genes in different rhizobial groups nor their role in the evolution of the symbiotic process...
December 2018: Heliyon
Kathrin Wippel, Sharon R Long
Host specificity in the root nodule symbiosis between legumes and rhizobia is crucial for the establishment of a successful interaction and ammonia provision to the plant. The specificity is mediated by plant-bacterial signal exchange during early stages of interaction. We observed that a Sinorhizobium meliloti mutant ∆relA, which is deficient in initiating the bacterial stringent response, fails to nodulate Medicago sativa (alfalfa), but successfully infects Medicago truncatula. We used biochemical, histological, transcriptomic, and imaging approaches to compare the behavior of the S...
December 21, 2018: Molecular Plant-microbe Interactions: MPMI
Kent N Strodtman, Sooyoung Frank, Severin Stevenson, Jay J Thelen, David W Emerich
The form and physiology of Bradyrhizobium diazoefficiens after the decline of symbiotic nitrogen fixation has been characterized. Proteomic analyses showed that post-symbiotic B. diazoefficiens underwent metabolic remodeling as well-defined groups of proteins declined, increased or remained unchanged from 56 to 119 days after planting, suggesting a transition to a hemibiotrophic-like lifestyle. Enzymatic analysis showed distinct patterns in both the cytoplasm and the periplasm. Similar to the bacteroid, the post-symbiotic bacteria rely on a non-citric acid cycle supply of succinate and, although viable, they did not demonstrate the ability to grow within the senescent nodule...
December 8, 2018: International Journal of Molecular Sciences
Juan Liang, Anne Hoffrichter, Andreas Brachmann, Macarena Marín
Rhizobia bacteria engage in nitrogen-fixing root nodule symbiosis, a mutualistic interaction with legume plants in which a bidirectional nutrient exchange takes place. Occasionally, this interaction is suboptimal resulting in the formation of ineffective nodules in which little or no atmospheric nitrogen fixation occurs. Rhizobium leguminosarum Norway induces ineffective nodules in a wide range of Lotus hosts. To investigate the basis of this phenotype, we sequenced the complete genome of Rl Norway and compared it to the genome of the closely related strain R...
2018: Standards in Genomic Sciences
Hai D T Nguyen, Sylvie Cloutier, Eden S P Bromfield
We present the complete genome sequence of Bradyrhizobium ottawaense strain OO99T , a nitrogen-fixing bacterium from root nodules of soybean. The genome consists of a single 8.6-Mb chromosome and includes a symbiosis island. Genes involved in symbiotic nitrogen fixation, stress response, resistance to antibiotics, and toxic compounds were detected.
November 2018: Microbiology resource announcements
Alejandrina Hernández-López, Mauricio Díaz, Jonathan Rodríguez-López, Gabriel Guillén, Federico Sánchez, Claudia Díaz-Camino
Bax-inhibitor 1 (BI-1) is a cell death suppressor conserved in all eukaryotes that modulates cell death in response to abiotic stress and pathogen attack in plants. Thus far nothing is known about its role in the establishment of symbiotic interactions. Here, we demonstrate the functional relevance of an Arabidopsisthaliana BI-1 homolog (PvBI-1a) to symbiosis between the common bean (Phaseolus vulgaris) and Rhizobium tropici. We show that the PvBI-1a expression changes observed during early symbiosis resemble those of some defence-response related proteins...
November 21, 2018: Journal of Experimental Botany
Sebastian Schneider, Arno Schintlmeister, Manuel Becana, Michael Wagner, Dagmar Woebken, Stefanie Wienkoop
Legume-rhizobia symbioses play a major role in food production for an ever growing human population. In this symbiosis, dinitrogen is reduced ('fixed') to ammonia by the rhizobial nitrogenase enzyme complex and is secreted to the plant host cells, while dicarboxylic acids derived from photosynthetically-produced sucrose are transported into the symbiosomes and serve as respiratory substrates for the bacteroids. The symbiosome membrane contains high levels of SST1 protein, a sulfate transporter. Sulfate is an essential nutrient for all living organisms, but its importance for symbiotic nitrogen fixation and nodule metabolism has long been underestimated...
November 15, 2018: Plant, Cell & Environment
Manisha Shrestha, Karl K Compton, Jordan Mancl, Benjamin Webb, Anne Brown, Birgit Scharf, Florian D Schubot
The alpha-proteobacterium Sinorhizobium meliloti can live freely in the soil or engage in a symbiosis with its legume host.  S. meliloti facilitates nitrogen-fixation in root nodules, thus providing pivotal, utilizable nitrogen to the host.  The organism has eight chemoreceptors, namely McpT to McpZ and IcpA that facilitate chemotaxis.  McpX is the first known bacterial sensor of quaternary amine compounds (QACs) such as choline and betaines.  Because QACs are exuded at chemotaxis-relevant concentrations by germinating alfalfa seeds, McpX has been proposed to contribute to host-specific chemotaxis...
November 15, 2018: Biochemical Journal
Fanuel Kawaka, Huxley Makonde, Mathews Dida, Peter Opala, Omwoyo Ombori, John Maingi, John Muoma
Biological nitrogen fixation (BNF) in legumes plays a critical role in improving soil fertility. Despite this vital role, there is limited information on the genetic diversity and BNF of bacteria nodulating common bean (Phaseolus vulgaris L.). This study evaluated the genetic diversity and symbiotic nitrogen fixation of bacteria nodulating common bean in soils of Western Kenya. The genetic diversity was determined using 16S rRNA gene partial sequences while BNF was estimated in a greenhouse experiment. The sequences of the native isolates were closely affiliated with members from the genera Pantoea, Klebsiella, Rhizobium, Enterobacter and Bacillus...
2018: PloS One
Drishti Mandal, Senjuti Sinharoy
Mesorhizobium sp. produces root nodules in chickpea. Chickpea and model legume Medicago truncatula are members of inverted repeat lacking clade (IRLC). The rhizobia after internalization into the plant cell are called 'bacteroid'. Nodule Specific Cysteine-rich (NCR) peptides in IRLC legumes guide bacteroids to a 'terminally differentiated swollen (TDS)' form. Bacteroids in chickpea are less TDS than those in Medicago. Nodule development in chickpea indicates recent evolutionary diversification and merits further study...
November 6, 2018: Molecular Plant-microbe Interactions: MPMI
Manuel Becana, Stefanie Wienkoop, Manuel A Matamoros
Sulfur is an essential nutrient in plants as a constituent element of some amino acids, metal cofactors, coenzymes, and secondary metabolites. Not surprisingly, sulfur deficiency decreases plant growth, photosynthesis, and seed yield in both legumes and non-legumes. In nodulated legumes, sulfur supply is positively linked to symbiotic nitrogen fixation (SNF) and sulfur starvation causes three additional major effects: decrease of nodulation, inhibition of SNF, and slowing down of nodule metabolism. These effects are due, at least in part, to the impairment of nitrogenase biosynthesis and activity, the accumulation of nitrogen-rich amino acids, and the decline in leghemoglobin, ferredoxin, ATP, and glucose in nodules...
2018: Frontiers in Plant Science
K S Antonets, O P Onishchuk, O N Kurchak, K V Volkov, A N Lykholay, E A Andreeva, E E Andronov, A G Pinaev, N A Provorov, A A Nizhnikov
The importance of root nodule bacteria in biotechnology is determined by their distinctive feature: symbiotic nitrogen fixation resulting in the production of organic nitrogen-containing compounds. While interacting with host legume plants, the cells of these bacteria undergo global changes at all levels of expression of genetic information leading to the formation in root nodules of so-called bacteroids functioning as nitrogen fixation factories. The molecular mechanisms underlying plant-microbial symbiosis are actively investigated, and one of the most interesting and poorly studied aspects of this problem is the species-specificity of interaction between root nodule bacteria and host plants...
September 2018: Molekuliarnaia Biologiia
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