Sporulation regulatory protein SpoIIID from Bacillus subtilis activates and represses transcription by both mother-cell-specific forms of RNA polymerase.

Mother-cell-specific gene expression during sporulation of Bacillus subtilis is controlled by sigma E and sigma K RNA polymerases. sigma E is required for the expression of genes during stage III (engulfment of the forespore), while sigma K is required for the expression of genes during stage IV (formation of the spore cortex) and stage V (formation of the spore coat). Previous studies indicated that SpoIIID could influence transcription by sigma K RNA polymerase in vitro. We demonstrate here that SpoIIID is a DNA-binding protein that recognizes specific sequences in the promoter regions and open reading frames of both sigma E- and sigma K-dependent genes. We also show that SpoIIID can activate or repress transcription by both forms of RNA polymerase. These results support the idea that the appearance and subsequent disappearance of SpoIIID plays a major role in controlling the mother-cell pattern fo gene expression during stages III to V of sporulation.