Metabolomics,Unknown,Transcriptomics,Genomics,Proteomics

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Comparative transcriptomics of 5 Mesorhizobium strains (ORS3324, ORS3359, ORS3356, ORS3365, STM8773) under salt stress

ABSTRACT: We analysed the transcriptomic response by RNAseq of 5 Mesorhizobium strains with different tolerance to the presence of salt (NaCl) in their liquid culture medium (medium used TY- Tryptone Yeast Extract).

INSTRUMENT(S): Illumina HiSeq 2000

ORGANISM(S): Mesorhizobium plurifarium

SUBMITTER: Lionel Moulin

PROVIDER: E-MTAB-4148 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:The M-NM-1-proteobacterium Sinorhizobium fredii NGR234 has an exceptionally wide host range as it forms nitrogen-fixing nodules with more legumes than any other known microsymbiont. Within its 6.9 Mbp genome it encodes two N-acyl-homoserine-lactone synthase genes (i.e. traI and ngrI) involved in the biosynthesis of two distinct autoinducer I-type molecules. Here we report on the construction of a NGR234-M-NM-^TtraI and a NGR234-M-NM-^TngrI mutant and the genome wide RNA-seq-based transcriptome analysis in the parent strain and in the two constructed mutants. A high-resolution RNA-seq analysis of early stationary phase cultures in the background of NGR234-M-NM-^TtraI suggested that up to 316 genes (4.9% of all predicted genes) were differentially expressed in the mutant vs. the parent strain. Similarly, in the background of NGR234-M-NM-^TngrI 466 differentially regulated genes (7.3% of all predicted genes) were identified. A considerable overlap in the gene expression pattern was uncovered between both mutants resulting in a common set of 186 genes which were almost identically regulated. Co-regulated genes that were linked to the ngrI- and the traI-dependent autoinducer regulatory circuits included 53 flagella biosynthesis genes and genes linked to EPS succinoglycan biosynthesis. Among the genes and ORFs that were differentially regulated in NGR234-M-NM-^TtraI were those linked to replication of the pNGR234a symbiotic plasmid and cytochrome c-related genes. In the NGR234-M-NM-^TngrI mutant biotin and pyrroloquinoline quinone (PQQ) biosynthesis genes were differentially expressed as well as the entire cluster of 21 genes linked to assembly of the NGR234 type three secretion system II (T3SS-II). We also discovered that genes responsible for octopine catabolism in NGR234 are strongly repressed in the presence of high levels of N-acyl-homoserine-lactones (AHLs). Surprisingly, only few truly symbiosis-related genes were identified that appeared to be quorum sensing regulated. Together with nodulation assays, the RNAseq-based findings suggested that QS-dependent gene regulation appears to be of higher relevance during non-symbiotic growth rather than for life within root nodules. In total 12 samples were analyzed (six different treatments with two independent samples), treatment A: NGR234 wild type strain in stationary phase, treatment B: NGR234 traI-mutant strain in stationary phase, treatment C: NGR234 ngrI-mutant strain in stationary phase, treatment D: NGR234 wild type strain in exponential phase, treatment E: NGR234 wild type supplemented with 0.05 M-BM-5M AHLs in exponential phase, treatment F: NGR234 wild type supplemented with 50 M-BM-5M AHLs in exponential phase

Project description:Xanthomonas is one important model microbe to study the molecular determinants of virulence and host range of pathogens since Xanthomonas is capable of infecting numerous monocotyledonous and dicotyledonous plants. Among the plant diseases caused by Xanthomonas, X. citri subsp. citri (Xcc) causes citrus canker, which has significant impact on citrus production. Xcc is classified into different strains primarily by host range including A and Aw. The A (Asiatic) strain (XccA) has a wide host range and is most virulent, whereas Aw (Wellington) strain has restricted host range including Key or Mexican lime and alemow. We hypothesized that not only gene content but also gene expression contributes to the difference in virulence and host range of closely related strains. To test our hypothesis, comparative genomic and transcriptome analyses were conducted to study the two closely related Xcc A and Aw strains. The genome of X. citri subsp. citri strain Aw12879 (Xcaw) was completely sequenced using 454 Pyrosequencing, Illumina sequencing and Optical mapping. The finished genome (5.3 Mb chromosome and two plasmids pXcaw19 and pXcaw58) of Xcaw was annotated, curated and compared with XccA genome. Protein blast revealed multiple genes including type III secretion system (TIIISS) effectors xopAF and xopAG are present in Xcaw but absent in XccA. Comparative genomic analysis showed various changes in genes encoding LPS and type IV secretion system. Furthermore, RNA-Seq was used to compare expression profile of Xcaw and XccA in nutrient rich (NB) medium and XVM2 medium which is known to mimic the intercellular space of plant cells using Illumina sequencing. Multiple avirulence/effector genes were over-expressed in Xcaw compared to XccA which might contribute to the limited host range of Xcaw compared to XccA. The overexpression of genes involved in cell wall degradation, attachment, ROS (reactive oxygen species) scavenging, nutrient transportation in XccA might contribute to its expanding of host range. Our data suggest that both gene content and gene expression contribute to difference in virulence and host range of bacterial pathogens. This study lays the foundation to further characterize the mechanisms for virulence and host range of strains of X. citri subsp. citri and other bacterial pathogens. mRNA expression profiles of Xcc strain A and Aw were generated in 2 media: NB and XVM2 by deep sequencing, in triplicate, using Illumina GAII.

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Comparative transcriptomics of 5 Mesorhizobium strains (ORS3324, ORS3359, ORS3356, ORS3365, STM8773) under salt stress

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