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Next Generation Annotation of prokarotic genomes with EuGene-P: application to Sinorhizobium meliloti 2011

ABSTRACT: With a view to re-annotate the genome sequence of the nitrogen fixing bacterium Sinorhizobium meliloti, we generated oriented sequences of transcripts. To cover a large number of expressed genes we prepared RNA from bacteria grown in three very different physiological conditions including bacteria grown in liquid cultures (in both exponential and stationary growth phases) and from 10-day-old nodules in which bacteria were differentiated in nitrogen fixing bacteroids. The transcripts sequences were then integrated into EuGene-P, a new prokaryotic genome annotation tool able to integrate high throughput data including oriented RNA-Seq data directly into the prediction process, which led to the production of an accurate and complete annotation of the genome of S. meliloti strain 2011.

OTHER RELATED OMICS DATASETS IN: PRJNA187276PRJNA188524

ORGANISM(S): Medicago truncatula Sinorhizobium meliloti

PROVIDER: GSE44083 | GEO | 2013/04/01

SECONDARY ACCESSION(S): PRJNA188524

REPOSITORIES: GEO

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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.

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Next Generation Annotation of prokarotic genomes with EuGene-P: application to Sinorhizobium meliloti 2011

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