Regulation of the Transcription of a Cluster of Bacillus subtilis Spore Coat Genes

Abstract

The pattern of transcription has been examined for a cluster of genes encoding polypeptides some or all of which are assembled into a cross-linked component of the Bacillus subtilis spore coat. Three promoters, designated PVWX, PX, PYZ, were indicated by reverse transcriptase mapping. On the basis of Norther hybridization, it appeared that the cotV, W and X genes were transcribed as a polycistronic mRNA from PVWX as well as a monocistronic cotX mRNA from PX. The cotY and cotZ genes are cotranscribed from the PYZ promoter with a smaller cotY mRNA resulting from premature termination or RNA processing. All four transcripts were synthesized late during sporulation and were not produced in mutants lacking sigma K, which directs RNA polymerase to transcribe genes in the mother-cell compartment of sporulating cells. The DNA-binding protein GerE, which affects transcription of many genes in the mother cell during the late stages of sporulation, was also shown to be involved. There was essentially no cotX mRNA in a gerE mutant and the amounts of cotVWX, cotYZ and cotY mRNAs were somewhat reduced. In vitro run-off transcription studies with σK RNA polymerase and GerE confirmed the presence of the three promoters, and directly showed that GerE was necessary for transcription from PX as well as enhanced transcription from the PVWX and PYZ promoters. The DNase I footprints of GerE for all three promoters were immediate upstream of the -35 regions. These GerE binding sites were compared to those in other GerE-responsive promoters and a large consensus sequence for GerE binding was recognized. This complex transcriptional pattern of the cotVWXYZ cluster is probably necessary to ensure that an optimal amount of each protein is made for the assembly of the spore coat.