Project description:Azoarcus sp. BH72 is known to express nitrogenase genes endophytically in rice seedlings in gnotobiotic culture. Availability of fixed nitrogen is one of the important signals regulating the transcription of nitrogenase genes and hence nitrogen fixing activity. NifA is the essential transcription activator of nif genes. RNA isolated from the nifA knockout mutant of strain BH72 was compared with the transcriptome of wild type under nitrogen fixing condition using a global genome wide microarray approach and the differences in the gene expression profile were monitered.
Project description:Casuarina glauca belongs to a family of angiosperms called actinorhizal plants because they can develop nitrogen-fixing nodules in association with the soil bacteria Frankia. The aim of this transcriptomic study was to get a global view of the plant symbiotic genetic program and to identify new key plant genes that control nodulation during symbiosis in C. glauca. Symbiosis between C. glauca and Frankia was obtained after inoculation of young plant with a concentrated culture of the bacteria. Inoculation was performed in a medium depleted in nitrogen which favors the induction of nitrogen fixing symbiosis. For this study we considered two stages of symbiosis: - an early stage where inoculated roots were harvested 7 days after inoculation with the bacteria and compared to two controls (non-inoculated roots grown with or without nitrogen and harvested at the same time) - a late stage where nodules (nitrogen-fixing specific organs) were harvested 21 days after inoculation and compared to non-inoculated roots harvested on the day of inoculation (which is our reference time 0d). Three biological replicates were used for each condition.
Project description:Alnus glutinosa belongs to a family of angiosperms called actinorhizal plants because they can develop nitrogen-fixing nodules in association with the soil bacteria Frankia. The aim of this transcriptomic study was to get a global view of the plant symbiotic genetic program and to identify new key plant genes that control nodulation during symbiosis in A. glutinosa. Symbiosis between A. glutinosa and Frankia was obtained after inoculation of young plant with a concentrated culture of the bacteria. Inoculation was performed in a medium depleted in nitrogen which favors the induction of nitrogen fixing symbiosis. For this study we considered two stages of symbiosis: - an early stage where inoculated roots were harvested 7 days after inoculation with the bacteria and compared to two controls (non-inoculated roots grown with or without nitrogen and harvested at the same time) - a late stage where nodules (nitrogen-fixing specific organs) were harvested 21 days after inoculation and compared to non-inoculated roots harvested on the day of inoculation (which is our reference time 0d). Three biological replicates were used for each condition.
Project description:During the legume-rhizobium symbiosis, free-living soil bacteria known as rhizobia trigger the formation of root nodules. The rhizobia infect these organs and adopt an intracellular lifestyle within the symbiotic nodule cells where they become nitrogen-fixing bacteroids. Several legume lineages enforce their symbionts into an extreme cellular differentiation, comprising cell enlargement and genome endoreduplication. The antimicrobial peptide transporter BclA is a major determinant of this differentiation process in Bradyrhizobium sp. ORS285, a symbiont of Aeschynomene spp.. In the absence of BclA, Bradyrhizobium sp. ORS285 proceeds until the intracellular infection of nodule cells but the bacteria cannot differentiate into enlarged polyploid bacteroids and fix nitrogen. The nodule bacteria of the bclA mutant constitute thus an intermediate stage between the free-living soil bacteria and the intracellular nitrogen-fixing bacteroids. Metabolomics on whole nodules of Aeschynomene afraspera and Aeschynomene indica infected with the ORS285 wild type or the bclA mutant revealed 47 metabolites that differentially accumulated concomitantly with bacteroid differentiation. Bacterial transcriptome analysis of these nodules discriminated nodule-induced genes that are specific to differentiated and nitrogen-fixing bacteroids and others that are activated in the host microenvironment irrespective of bacterial differentiation and nitrogen fixation. These analyses demonstrated that the intracellular settling of the rhizobia in the symbiotic nodule cells is accompanied with a first transcriptome switch involving several hundreds of upregulated and downregulated genes and a second switch accompanying the bacteroid differentiation, involving less genes but that are expressed to extremely elevated levels. The transcriptomes further highlighted the dynamics of oxygen and redox regulation of gene expression during nodule formation and we discovered that bclA represses the expression of non-ribosomal peptide synthetase gene clusters suggesting a non-symbiotic function of BclA. Together, our data uncover the metabolic and gene expression changes that accompany the transition from intracellular bacteria into differentiated nitrogen-fixing bacteroids.
Project description:Model endophyte Azoarcus sp. BH72 is known to contribute fixed nitrogen to its host Kallar grass by nitrogen fixation and also expresses nitrogenase genes endophytically in rice seedlings in gnotobiotic culture. Availability of fixed nitrogen is one of the important signals regulating the transcription of nitrogenase genes and hence nitrogen fixing activity. Therefore, we analysed global transcription in response to differences in the nitrogen source. Transcription profiles of cells grown microaerobically (0.6% oxygen) on minimal medium with nitrogen (N2-fixing) versus ammonium (combined nitrogen) were compared using a genome-wide microarray approach and differences in the gene expression profile were monitored.
Project description:The aim of this study was to investigate the expressional changes profiles of the wildtype and recombinant Escherichia coli strain which contains an non-coding RNA nfiS from the nitrogen-fixing Pseudomonas stutzeri A1501 after hydrogen peroxide shock, so as to lay a theoretical foundation for further clarifying the mechanism of this ncRNA to enhance the resistance ability of E.coli to oxidative stress. In our early research, an ncRNA named NfiS from the nitrogen fixing bacteria Pseudomonas stutzeri A1501 was identified to play an important role in the response to oxidative as well as osmotic stress. In this work, the nifS gene was transferred to E. coli Trans10. Heterologous expression of the nfiS in Trans10 enhanced its tolerance to salt stress and oxidative stress. To further study the effect of nfiS on gene expression in E. coli, microarray assay was performed to delineate the transcriptome difference between nfiS-expressing strain and wild type under H2O2 shock treatment.
Project description:To circumvent the paucity of nitrogen sources in the soil Legume plants evolved a symbiotic interaction with nitrogen-fixing soil bacteria called rhizobia. During symbiosis, legumes form root organs called nodules, where bacteria are housed intracellularly and become active nitrogen fixers known as bacteroids. Depending on their host plant, bacteroids can adopt different morphotypes, being either unmodified (U), elongated (E) or spherical (S). E- and S-typr bacteroids undergo a terminal differentiation leading to irreversible morphological changes and DNA endoreduplication. Previous studies suggest that differentiated bacteroids display an increased symbiotic efficiency (E>U & S>U). In this study, we used a combination of Aeschynomene species inducing E- and S-type bacteroids in symbiosis with Bradyrhizobium sp. ORS285 to show that S- performed better than E-type bacteroids. Thus, we performed a transcriptomic analysis on E- and S-type bacteroids to identify the bacterial functions involved in each bacteroid type.
Project description:Root nodule symbiosis (RNS) represents a significant phenotypic adaptation in plants to thrive in nitrogen-deficient environments. Recent findings propose a single gain of RNS at the crown of the nitrogen-fixing clade (NF clade). However, the genetic mechanisms underlying the origin and subsequent evolution of RNS remain largely unexplored. Here, we newly sequenced and assembled eleven genomes from the NF clade and studied genetic change along the evolution of RNS. Our results elucidated three key evolutionary stages leading to the formation of stable RNS between plants and symbiotic nitrogen-fixing bacteria.