A master regulator sigmaB governs osmotic and oxidative response as well as differentiation via a network of sigma factors in Streptomyces coelicolor.
The differentiating bacterium Streptomyces coelicolor harbours some 66 sigma factors, which support its complex life cycle. sigma(B), a functional homologue of sigma(S) from Escherichia coli, controls both osmoprotection and differentiation in S. coelicolor A3(2). Microarray analysis revealed sigma(B)-dependent induction of more than 280 genes by 0.2 M KCl. These genes encode several sigma factors, oxidative defence proteins, chaperones, systems to provide osmolytes, cysteine, mycothiol, and gas vesicle. sigma(B) controlled induction of itself and its two paralogues (sigma(L) and sigma(M)) in a hierarchical order of sigma(B)-->sigma(L)-->sigma(M), as revealed by S1 mapping and Western blot analyses. The phenotype of each sigma mutant suggested a sequential action in morphological differentiation; sigma(B) in forming aerial mycelium, sigma(L) in forming spores and sigma(M) for efficient sporulation. sigma(B) was also responsible for the increase in cysteine and mycothiol, the major thiol buffer in actinomycetes, upon osmotic shock, revealing an overlap between protections against osmotic and oxidative stresses. Proteins in sigB mutant were more oxidized (carbonylated) than the wild type. These results support a hypothesis that sigma(B) serves as a master regulator that triggers other related sigma factors in a cascade, and thus regulates differentiation and osmotic and oxidative response in S. coelicolor.
Lee
Eun-Jin
EJ
School of Biological Sciences and Institute of Microbiology, Seoul National University, Seoul 151-742, Korea.
Karoonuthaisiri
Nitsara
N
Kim
Hyo-Sub
HS
Park
Joo-Hong
JH
Cha
Chang-Jun
CJ
Kao
Camilla M
CM
Roe
Jung-Hye
JH
D001426:Bacterial Proteins / Q000235:genetics / Q000502:physiology*; D015870:Gene Expression / Q000187:drug effects; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial / Q000235:genetics; D020411:Oligonucleotide Array Sequence Analysis; D009997:Osmotic Pressure; D010084:Oxidation-Reduction; D018384:Oxidative Stress / Q000235:genetics*; D010641:Phenotype; D011189:Potassium Chloride / Q000494:pharmacology; D012808:Sigma Factor / Q000235:genetics / Q000502:physiology*; D048372:Streptomyces coelicolor / Q000235:genetics* / Q000254:growth & development*
D001426:Bacterial Proteins; C079011:SigB protein, Bacteria; D012808:Sigma Factor; D011189:Potassium Chloride