title: RsbV-independent induction of the SigB-dependent general stress regulon of Bacillus subtilis during growth at high temperature.
abstract: General stress proteins protect Bacillus subtilis cells against a variety of environmental insults. This adaptive response is particularly important for nongrowing cells, to which it confers a multiple, nonspecific, and preemptive stress resistance. Induction of the general stress response relies on the alternative transcription factor, SigB, whose activity is controlled by a partner switching mechanism that also involves the anti-sigma factor, RsbW, and the antagonist protein, RsbV. Recently, the SigB regulon has been shown to be continuously induced and functionally important in cells actively growing at low temperature. With the exception of this chill induction, all SigB-activating stimuli identified so far trigger a transient expression of the SigB regulon that depends on RsbV. Through a proteome analysis and Northern blot and gene fusion experiments, we now show that the SigB regulon is continuously induced in cells growing actively at 51 degrees C, close to the upper growth limit of B. subtilis. This heat induction of SigB-dependent genes requires the environmental stress-responsive phosphatase RsbU, but not the metabolic stress-responsive phosphatase RsbP. RsbU dependence of SigB activation by heat is overcome in mutants that lack RsbV. In addition, loss of RsbV alone or in combination with RsbU triggers a hyperactivation of the general stress regulon exclusively at high temperatures detrimental for cell growth. These new facets of heat induction of the SigB regulon indicate that the current view of the complex genetic and biochemical regulation of SigB activity is still incomplete and that SigB perceives signals independent of the RsbV-mediated signal transduction pathways under heat stress conditions.
authors.affiliation: Laboratory for Microbiology, Department of Biology, Philipps-University Marburg, Karl-von-Frisch-Str., D-35032 Marburg, Federal Republic of Germany.
authors.forename: Gudrun
authors.initials: G
authors.lastname: Holtmann
authors.forename: Matthias
authors.initials: M
authors.lastname: Brigulla
authors.forename: Leif
authors.initials: L
authors.lastname: Steil
authors.forename: Alexandra
authors.initials: A
authors.lastname: Schütz
authors.forename: Karsta
authors.initials: K
authors.lastname: Barnekow
authors.forename: Uwe
authors.initials: U
authors.lastname: Völker
authors.forename: Erhard
authors.initials: E
authors.lastname: Bremer
mesh_terms: D000222:Adaptation, Physiological; D019677:Artificial Gene Fusion; D001412:Bacillus subtilis / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D001426:Bacterial Proteins / Q000032:analysis / Q000235:genetics / Q000378:metabolism* / Q000502:physiology*; D015152:Blotting, Northern; D015964:Gene Expression Regulation, Bacterial; D017930:Genes, Reporter; D006358:Hot Temperature; D010744:Phosphoric Monoester Hydrolases / Q000235:genetics / Q000502:physiology; D020543:Proteome / Q000032:analysis; D012329:RNA, Bacterial / Q000032:analysis; D012333:RNA, Messenger / Q000032:analysis; D018085:Regulon / Q000502:physiology; D012808:Sigma Factor / Q000502:physiology*; D015398:Signal Transduction; D014158:Transcription, Genetic; D001616:beta-Galactosidase / Q000235:genetics / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D020543:Proteome; D012329:RNA, Bacterial; D012333:RNA, Messenger; C086522:RsbV protein, Bacteria; C079011:SigB protein, Bacteria; D012808:Sigma Factor; D010744:Phosphoric Monoester Hydrolases; C091162:RsbU protein, Bacillus subtilis; D001616:beta-Galactosidase