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.
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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