PRESPORE-SPECIFIC GENE-EXPRESSION IN BACILLUS-SUBTILIS IS DRIVEN BY SEQUESTRATION OF SPOIIE PHOSPHATASE TO THE PRESPORE SIDE OF THE ASYMMETRIC SEPTUM

The spoIIE gene is essential for the compartment-specific activation o f transcription factor sigma(F) during sporulation in Bacillus subtili s. SpoIIE is a membrane protein that is targeted to the potential site s of asymmetric septation near each pole of the sporulating cell. The cytoplasmic carboxy-terminal domain of SpoIIE contains a serine phosph atase that triggers the release of sigma(F) in the prespore compartmen t after septation. To understand how septum-located SpoIIE is activate d selectively in the prespore, we examined the distribution of a SpoII E-GFP fusion protein. We show that the polar bands of SpoIIE protein a ctually form sequentially and that the most prominent band develops at the pole where the prespore forms. We also show that the protein is s equestered to the prespore side of the asymmetric septum. Sequestratio n of SpoIIE into the prespore compartment provides a mechanism that co uld explain the cell specificity of sigma(F) activation.