title: Two-stage regulation of an anti-sigma factor determines developmental fate during bacterial endospore formation.
abstract: During endospore formation in Bacillus subtilis an asymmetric division produces two cells, forespore and mother cell, which follow different developmental paths. Commitment to the forespore-specific developmental path is controlled in part by the activation of the forespore-specific RNA polymerase sigma factor, sigma F. Activity of sigma F is inhibited in the mother cell by the anti-sigma factor SpoIIAB. In the forespore, sigma F directs transcription of the structural gene for sigma G. However, sigma G does not become active until after engulfment of the forespore is complete. This sigma G activity is dependent upon the products of the spoIIIA operon. We showed that sigma G is present but mostly inactive in a spoIIIA mutant. We also demonstrated that the anti-sigma factor SpoIIAB can bind to sigma G in vitro. Moreover, a mutant form of sigma G that binds SpoIIAB inefficiently in vitro was shown to function independently of SpoIIIA during sporulation. These and previously reported results support a model in which SpoIIAB functions as an inhibitor of sigma G activity during sporulation. Therefore, we propose that the anti-sigma factor SpoIIAB antagonizes both sigma F and sigma G activities, and that this antagonism is relieved in the forespore in two stages. In the first stage, which follows septation, a SpoIIAA-dependent mechanism partially relieves SpoIIAB inhibition of sigma F activity in the forespore. In the second stage, which follows forespore engulfment, a SpoIIIA-dependent process inactivates SpoIIAB in the forespore, resulting in the activation of sigma G.
authors.affiliation: Department of Microbiology and Immunology, Emory University School of Medicine, Atlanta, Georgia 30322, USA.
authors.forename: E M
authors.initials: EM
authors.lastname: Kellner
authors.forename: A
authors.initials: A
authors.lastname: Decatur
authors.forename: C P
authors.initials: CP
authors.lastname: Moran
mesh_terms: D000227:Adenine Nucleotides / Q000378:metabolism; D001412:Bacillus subtilis / Q000502:physiology*; D001426:Bacterial Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D012321:DNA-Directed RNA Polymerases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D009154:Mutation; D011485:Protein Binding; D012808:Sigma Factor / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism*; D013171:Spores, Bacterial / Q000502:physiology; D014157:Transcription Factors; D014158:Transcription, Genetic
chemical_list: D000227:Adenine Nucleotides; D001426:Bacterial Proteins; C064971:FliA protein, Bacteria; D012808:Sigma Factor; D014157:Transcription Factors; C092468:spoIIR protein, Bacillus subtilis; C030069:spore-specific proteins, Bacillus; C079274:RNA polymerase sigma G; D012321:DNA-Directed RNA Polymerases