Genetic evidence for interaction of σ(E) with the spoIIID promoter in Bacillus subtilis

Abstract

During sporulation in Bacillus subtilis, new RNA polymerase sigma factors are produced. These sigma factors direct the transcription of genes that are required for this cellular differentiation. In order to determine the role of each sigma factor in this process, it is necessary to know which promoters are recognized by each sigma factor. The spoIIID gene product plays an important role in the establishment of mother cell-specific gene expression during sporulation. We found that substitution of an alanine at position 124 of the sporulation-specific sigma factor σ(E) suppressed the effect of a single-base-pair transition at position -13 of the spoIIID promoter. This alanine substitution in σ(E) did not suppress the effect of a transversion at position -12 of the spoIIID promoter. The allele specificity of the interaction between σ(E) and the spoIIID promoter is strong evidence that σ(E) directs transcription from the spoIIID promoter during sporulation. Position 124 in σ(E) is located within a region that is highly conserved among the regions in other sigma factors that probably interact with the -10 regions of their cognate promoters.