PMID:20506020
| Citation |
Chiang, SM and Schellhorn, HE (2010) Evolution of the RpoS regulon: origin of RpoS and the conservation of RpoS-dependent regulation in bacteria. J. Mol. Evol. 70:557-71 |
|---|---|
| Abstract |
The RpoS sigma factor in proteobacteria regulates genes in stationary phase and in response to stress. Although of conserved function, the RpoS regulon may have different gene composition across species due to high genomic diversity and to known environmental conditions that select for RpoS mutants. In this study, the distribution of RpoS homologs in prokaryotes and the differential dependence of regulon members on RpoS for expression in two gamma-proteobacteria (Escherichia coli and Pseudomonas aeruginosa) were examined. Using a maximum-likelihood phylogeny and reciprocal best hits analysis, we show that the RpoS sigma factor is conserved within gamma-, beta-, and delta-proteobacteria. Annotated RpoS of Borrelia and the enteric RpoS are postulated to have separate evolutionary origins. To determine the conservation of RpoS-dependent gene expression across species, reciprocal best hits analysis was used to identify orthologs of the E. coli RpoS regulon in the RpoS regulon of P. aeruginosa. Of the 186 RpoS-dependent genes of E. coli, 50 proteins have an ortholog within the P. aeruginosa genome. Twelve genes of the 50 orthologs are RpoS-dependent in both species, and at least four genes are regulated by RpoS in other gamma-proteobacteria. Despite RpoS conservation in gamma-, beta-, and delta-proteobacteria, RpoS regulon composition is subject to modification between species. Environmental selection for RpoS mutants likely contributes to the evolutionary divergence and specialization of the RpoS regulon within different bacterial genomes. |
| Links |
PubMed Online version:10.1007/s00239-010-9352-0 |
| Keywords |
Bacterial Proteins/classification; Bacterial Proteins/genetics; Escherichia coli/genetics; Escherichia coli/metabolism; Evolution, Molecular; Gene Expression Regulation, Bacterial; Likelihood Functions; Phylogeny; Proteobacteria/genetics; Proteobacteria/metabolism; Pseudomonas aeruginosa/genetics; Pseudomonas aeruginosa/metabolism; Regulon/genetics; Regulon/physiology; Sigma Factor/classification; Sigma Factor/genetics |
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The RpoS sigma factor regulates stationary phase and stress-related genes in many bacteria. Although studied in several different bacterial species for its role in cell survival under adverse conditions, the distribution of RpoS orthologs and the conservation of RpoS regulon composition across bacterial species were not previously well-defined. In this paper, the RpoS sigma factor was found to be conserved within gamma-, beta-, and delta-proteobacteria using a maximum-likelihood phylogeny and a reciprocal best hits analysis. Annotated RpoS sigma factors in other species are postulated to have separate evolutionary origins. As well, RpoS regulon composition between two gamma-proteobacteria, E. coli and P. aeruginosa, are compared and shown to be subject to frequent modification.
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