title: Role of the stress sigma factor RpoS in GacA/RsmA-controlled secondary metabolism and resistance to oxidative stress in Pseudomonas fluorescens CHA0.
abstract: In Pseudomonas fluorescens biocontrol strain CHA0, the two-component system GacS/GacA positively controls the synthesis of extracellular products such as hydrogen cyanide, protease, and 2,4-diacetylphloroglucinol, by upregulating the transcription of small regulatory RNAs which relieve RsmA-mediated translational repression of target genes. The expression of the stress sigma factor sigmaS (RpoS) was controlled positively by GacA and negatively by RsmA. By comparison with the wild-type CHA0, both a gacS and an rpoS null mutant were more sensitive to H2O2 in stationary phase. Overexpression of rpoS or of rsmZ, encoding a small RNA antagonistic to RsmA, restored peroxide resistance to a gacS mutant. By contrast, the rpoS mutant showed a slight increase in the expression of the hcnA (HCN synthase subunit) gene and of the aprA (major exoprotease) gene, whereas overexpression of sigmaS strongly reduced the expression of these genes. These results suggest that in strain CHA0, regulation of exoproduct synthesis does not involve sigmaS as an intermediate in the Gac/Rsm signal transduction pathway whereas sigmaS participates in Gac/Rsm-mediated resistance to oxidative stress.
authors.affiliation: Département de Microbiologie Fondamentale, Université de Lausanne, CH-1015 Lausanne, Switzerland. stephan.heep@nottingham.ac.uk
authors.forename: Stephan
authors.initials: S
authors.lastname: Heeb
authors.forename: Claudio
authors.initials: C
authors.lastname: Valverde
authors.forename: Cécile
authors.initials: C
authors.lastname: Gigot-Bonnefoy
authors.forename: Dieter
authors.initials: D
authors.lastname: Haas
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D020689:Exopeptidases / Q000235:genetics / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D006861:Hydrogen Peroxide / Q000494:pharmacology; D009097:Multienzyme Complexes / Q000235:genetics / Q000378:metabolism; D018384:Oxidative Stress; D010088:Oxidoreductases / Q000235:genetics / Q000378:metabolism; D050891:Oxidoreductases Acting on CH-NH2 Group Donors; D011551:Pseudomonas fluorescens / Q000235:genetics / Q000254:growth & development / Q000378:metabolism / Q000502:physiology*; D016601:RNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D012808:Sigma Factor / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction
chemical_list: D001426:Bacterial Proteins; C091100:GacA protein, Bacteria; D009097:Multienzyme Complexes; D016601:RNA-Binding Proteins; D012097:Repressor Proteins; C095468:RsmA protein, Erwinia carotovora; D012808:Sigma Factor; C069567:sigma factor KatF protein, Bacteria; D006861:Hydrogen Peroxide; D010088:Oxidoreductases; D050891:Oxidoreductases Acting on CH-NH2 Group Donors; C112800:glycine dehydrogenase (cyanide-forming); C449646:AprA protein, Pseudomonas fluorescens; D020689:Exopeptidases