Overproducing the Bacillus subtilis mother cell sigma factor precursor, Pro-sigma K, uncouples sigma K-dependent gene expression from dependence on intercompartmental communication.
During sporulation of Bacillus subtilis, proteolytic activation of pro-sigma K and ensuing sigma K-dependent gene expression normally require the activity of many sporulation gene products. We report here that overproducing pro-sigma K at the onset of sporulation substantially uncouples sigma K-dependent gene expression from its normal dependency. Overproducing pro-sigma K in strains with a mutation in spoIIIG, spoIIIA, spoIIIE, or spoIVB partially restored sigma K-dependent gene expression in the mother cell and resulted in accumulation of a small amount of polypeptide that comigrated with sigma K, but these mutants still failed to form spores. In contrast, sporulation of spoIVF mutants was greatly enhanced by pro-sigma K overproduction. The products of the spoIVF operon are made in the mother cell and normally govern pro-sigma K processing, but overproduction of pro-sigma K appears to allow accumulation of a small amount of sigma K, which is sufficient to partially restore mother cell gene expression and spore formation. This spoIVF-independent mechanism for processing pro-sigma K depends on sigma E, an earlier-acting mother cell-specific sigma factor. The spoIIID gene, which encodes a mother cell-specific DNA-binding protein that is normally required for pro-sigma K production, was shown to be required for efficient pro-sigma K processing as well. bof (bypass of forespore) mutations bypassed this requirement for spoIIID, suggesting that SpoIIID is less directly involved in pro-sigma K processing than are spoIVF gene products. However, bof spoIIID double mutants overproducing pro-sigma K still failed to sporulate, indicating that SpoIIID serves another essential role(s) in sporulation in addition to its multiple roles in the production of sigma K.
Department of Biochemistry, Michigan State University, East Lansing 48824.
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D001412:Bacillus subtilis / Q000502:physiology*; D001426:Bacterial Proteins / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D002450:Cell Communication / Q000235:genetics / Q000502:physiology*; D015964:Gene Expression Regulation, Bacterial; D011498:Protein Precursors / Q000235:genetics / Q000378:metabolism*; D011499:Protein Processing, Post-Translational; D011994:Recombinant Proteins / Q000096:biosynthesis; D012808:Sigma Factor; D013171:Spores, Bacterial / Q000502:physiology*; D014157:Transcription Factors / Q000096:biosynthesis* / Q000235:genetics
D001426:Bacterial Proteins; D011498:Protein Precursors; D011994:Recombinant Proteins; D012808:Sigma Factor; D014157:Transcription Factors; C084190:sigma K; C092468:spoIIR protein, Bacillus subtilis; C030069:spore-specific proteins, Bacillus