Metabolomics,Unknown,Transcriptomics,Genomics,Proteomics

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SRNAs in Rhizobium etli differentially expressed during free-living and host-associated growth

ABSTRACT: 89 small non-coding RNAs (ncRNAs) were identified in the soil-dwelling alpha-proteobacterium Rhizobium etli by comparing an extensive compilation of ncRNA predictions to intergenic expression data of a whole-genome tiling array. The differential expression levels of some of these ncRNAs during free-living growth and during interaction with the eukaryotic host plant may indicate a role in adaptation to changing environmental conditions. In order to study expression in the free-living state, wild-type R. etli CFN42 was grown at 30ËC in acid minimal salts medium supplied with 10 mM NH4Cl and 10 mM succinate while monitoring the optical density (OD) of the culture. Samples were taken at OD600 = 0.3, 0.7 and 6 hours after reaching the maximum OD, representing early/late exponential and stationary phase, respectively. In order to study gene expression during host-associated growth, common bean plants (Phaseolus vulgaris cv. Limburgse vroege) were cultivated and inoculated as described previously. Nodules were harvested 2 and 3 weeks after inoculation and the bacteroids were purified by differential centrifugation.

ORGANISM(S): Rhizobium etli CFN 42

SUBMITTER: Lore Cloots

PROVIDER: E-GEOD-18580 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:A core component of the M-NM-1-proteobacterial general stress response is the extracytoplasmic function (ECF) sigma factor EcfG, exclusively present in this taxonomic class. Half of the completed M-NM-1-proteobacterial genome sequences contain two or more copies of genes encoding M-OM-^CEcfG-like sigma factors, with the primary copy typically located adjacent to genes coding for a cognate anti-sigma factor (NepR) and two-component response regulator (PhyR). So far, the widespread occurrence of additional, non-canonical M-OM-^CEcfG copies has not satisfactorily been explained. This work explores the hierarchical relation between Rhizobium etli M-OM-^CEcfG1 and M-OM-^CEcfG2, canonical and non-canonical M-OM-^CEcfG proteins, respectively. Contrary to reports in other species, we find that M-OM-^CEcfG1 and M-OM-^CEcfG2 act in parallel, as nodes of a complex regulatory network, rather than in series, as elements of a linear regulatory cascade. We demonstrate that both sigma factors control unique yet also shared target genes, corroborating phenotypic evidence. M-OM-^CEcfG1 drives expression of rpoH2, explaining the increased heat sensitivity of an ecfG1 mutant, while katG is under control of M-OM-^CEcfG2, accounting for reduced oxidative stress resistance of an ecfG2 mutant. We also identify non-coding RNA genes as novel M-OM-^CEcfG targets. We propose a modified model for general stress response regulation in R. etli, in which M-OM-^CEcfG1 and M-OM-^CEcfG2 function largely independently. Based on a phylogenetic analysis and considering the prevalence of M-NM-1-proteobacterial genomes with multiple M-OM-^CEcfG copies, this model may also be applicable to numerous other species. In this study, we investigate to which degree R. etli EcfG1 and EcfG2 regulation is interdependent. Furthermore, we demonstrate that both sigma factors control distinct regulons and pinpoint unique EcfG2 target genes. We also identify non-coding RNAs (ncRNAs) as novel targets of EcfG1 and EcfG2 and show that expression of at least one of these ncRNAs is under direct EcfG control. The presence of ncRNAs in the regulon of an EcfG type sigma factor has not been described previously and adds an extra level of complexity to the regulation of the general stress response in Alpha-proteobacteria. Moreover, considering the widespread existence of Alpha-proteobacterial genomes with multiple EcfG copies, the here presented results not only lead to a better understanding of the general stress response in R. etli, but also contribute to a conceptual paradigm for general stress response regulation by multiple EcfG proteins in Alpha-proteobacteria. Comparative transcriptome analyses were carried out on four samples: the parental strain (WT) and mutants in either sigma factor gene ecfG1, sigma factor gene ecfG2, and both genes combined.

Project description:Longevity mechanisms increase lifespan by counteracting the effects of aging. However, whether longevity mechanisms counteract the effects of aging continually throughout life, or whether they act during specific periods of life, preventing changes that precede mortality is unclear. Here, we uncover transcriptional drift, a phenomenon that describes how aging causes genes within functional groups to change expression in opposing directions. These changes cause a transcriptome-wide loss in mRNA stoichiometry and loss of co-expression patterns in aging animals, as compared to young adults. Using Caenorhabditis elegans as a model, we show that extending lifespan by inhibiting serotonergic signals by the antidepressant mianserin attenuates transcriptional drift, allowing the preservation of a younger transcriptome into an older age. Our data are consistent with a model in which inhibition of serotonergic signals slows age-dependent physiological decline and the associated rise in mortality levels exclusively in young adults, thereby postponing the onset of major mortality. In this study set out to measure aging in the transcriptome by determining drift-variance changes with age in C.elegans. We set up three different cohorts of water or mianserin treated animals. The title of each cohort indicates the treatment (e.g. h2o or mia), the concentration (mia2, mia10, mia50), the day when the treatment was started (e.g. d1= day 1 of adulthood) and the day when the sample was collected (e.g. d10= day 10 of adulthood). cohort #1: Celegans was treated with water or mianserin (50uM) on day 1 and RNA was harvested on day1 (water only), d3, d5 and day 10 (file titles: h2o d1/d1, h2o d1/d3, h2o d1/d5, h2o d1/d10, mia50 d1/d3, mia50 d1/d5, mia50 d1/d10) cohort #2: Celegans was treated with mianserin (50uM) starting on day 3, and day 5, RNA was harvested on day 5 or 10 (file titles: mia50 d3/d10, mia50 d5/d10, mia50 d3/d5) cohort #3: Celegans was treated with mianserin 2 uM and 10 uM Mianserin on day 1 and Rna harvested on day 5 (file titles: mia2 d1/d5, mia10 d1/d5)

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SRNAs in Rhizobium etli differentially expressed during free-living and host-associated growth

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