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:Rhizobia are soil bacteria that can associate with some legumes and participate in symbiotic nitrogen fixation. Bacterial CspA family members are small, single stranded nucleic acid binding proteins. Differentiation of rhizobial bacteria from a free-living to symbiotic state within legume root nodules follows a massive re-programming of bacterial gene expression. Here, the role of Sinorhizobium meliloti CspA family members in symbiotic development with Medicago sativa (alfalfa) was investigated. We defined expression patterns of CspA family members, identified CspA interacting RNAs, and investigated phenotypes and transcriptional defects associated with cspA deletion strains. We propose that these proteins affect rhizobial physiology through their global control of the cellular RNA secondary structure strength environment and through specific modulation of small non-coding RNA (sRNA) structures involved in cis-regulation of stress responsive sigma factor expression. This work describes an RNA structure mediated mechanism important for bacterial stress adaptation and symbiotic development within a plant host.
Project description:Rhizobia are soil bacteria that can associate with some legumes and participate in symbiotic nitrogen fixation. Bacterial CspA family members are small, single stranded nucleic acid binding proteins. Differentiation of rhizobial bacteria from a free-living to symbiotic state within legume root nodules follows a massive re-programming of bacterial gene expression. Here, the role of Sinorhizobium meliloti CspA family members in symbiotic development with Medicago sativa (alfalfa) was investigated. We defined expression patterns of CspA family members, identified CspA interacting RNAs, and investigated phenotypes and transcriptional defects associated with cspA deletion strains. We propose that these proteins affect rhizobial physiology through their global control of the cellular RNA secondary structure strength environment and through specific modulation of small non-coding RNA (sRNA) structures involved in cis-regulation of stress responsive sigma factor expression. This work describes an RNA structure mediated mechanism important for bacterial stress adaptation and symbiotic development within a plant host.
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. They can also develop arbuscular mycorrhizae (AM) while associated with Glomeromycota fungi. The aim of this transcriptomic study was to get a global view of the plant symbiotic genetic program in AM and to identify new key plant genes involved in endosymbioses.
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:It is well-known that individual pea (Pisum sativum L.) cultivars differ in their symbiotic responsivity. This trait is typically manifested with an increase in seed weights due to inoculation with rhizobial bacteria and arbuscular mycorrhizal fungi. The aim of this work was to characterize the alterations in root proteome of highly responsive pea genotype k-8274 and low-responsive genotype k-3358 grown in non-sterile soil, which were associated with root colonization with rhizobial bacteria and arbuscular mycorrhiza fungi in comparison to proteome shifts caused by soil supplementation with mineral nitrogen salts. Our results clearly indicate that supplementation of the soil with mineral nitrogen-containing salts switched the root proteome of both genotypes to assimilation of the available nitrogen, whereas the processes associated with nitrogen fixation were suppressed. Surprisingly, inoculation with rhizobial bacteria had only a minor effect on root proteomes of the both genotypes. The most pronounced response was observed for highly responsive k-8274 genotype inoculated simultaneously with rhizobial bacteria and arbuscular mycorrhizal fungi. This response involved activation of the proteins related to redox metabolism and suppression of excessive nodule formation. In turn, the low-responsive genotype k-3358 demonstrated a pronounced inoculation-induced suppression of protein metabolism and enhanced diverse defense reactions in pea roots under the same soil conditions. The results of the study shed light on the molecular basis of differential symbiotic responsivity in different pea cultivars.
Project description:This SuperSeries is composed of the following subset Series: GSE25572: Depolymerization of plant cell wall glycans by symbiotic human gut bacteria (Bacteroides thetaiotaomicron) GSE25575: Depolymerization of plant cell wall glycans by symbiotic human gut bacteria (Bacteroides ovatus) Refer to individual Series
Project description:Rhizobia are soil bacteria that can enter into complex symbiotic relationships with legumes, where rhizobia induce the formation of nodules on the plant root. Inside nodules, rhizobia differentiate into nitrogen-fixing bacteroids that reduce atmospheric nitrogen into ammonia, secreting it to the plant host in exchange for carbon. During the transition from free-living bacteria to bacteroids, rhizobial metabolism undergoes major changes. To investigate the metabolism of bacteroids and contrast it with the free-living state, we quantified the proteome of unlabelled bacteroids relative to 15N-labelled free-living rhizobia. The data were used to build a core metabolic model of pea bacteroids for the strain Rhizobium leguminosarum bv. viciae 3841.
Project description:In this pioneering study, we present the first comprehensive catalog of 683 small non-coding miRNAs for Astyanax mexicanus. Focusing on an early developmental stage, miRNAs were extracted and sequenced from 24hpf embryos of surface fish and three distinct cavefish morphs (Pachón, Tinaja, and Molino). We utilized in silico analyses to predict putative 3’UTR targets of these miRNAs, revealing a unique and extensive miRNA landscape in cavefish. Small RNA sequencing identified over 100 differentially expressed miRNAs in each cave morph compared to surface fish at 24hpf, suggesting early activation of miRNA-mediated silencing pathways. Notably, a subset of miRNAs was common across all three cave morphs, constituting cave-specific miRNAs potentially instrumental in cave adaptation. To unravel the functional implications of these cave-specific miRNAs, we analyzed their predicted target genes. Gene Ontology (GO) term analysis unveiled pathways which align with known adaptations in cavefish, primarily affecting development and metabolism. Further, cross-validating with a sample mRNAseq data from Pachón and surface fish also strongly suggested impact of these miRNAs on cave adaptation associated pathways. This study establishes a foundation for exploring miRNA-mediated gene regulation in cavefish, shedding light on their potential role in regulating early developmental and metabolic adaptations crucial for troglomorphic features. The comprehensive miRNA catalog provided will also guide future investigations into the intricate world of miRNA-mediated evolution in cave-adapted species.
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.