Genetic analysis of the Bacillus subtilis sigG promoter, which controls the sporulation-specific transcription factor σ G

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Abstract
At the onset of sporulation inBacillus subtilis, an asymmetric cell division gives rise to two unequal-sized compartments with distinct developmental fates. The smaller compartment, or prespore, becomes the spore, whilst the larger compartment, or mother cell, eventually lyses after contributing to spore maturation. The fate of each compartment is determined by differential gene expression, controlled by the activation of four compartment-specificσ-factors. The expression and activity of all fourσ-factors are tightly regulated to ensure the correct sequence of morphological events. Prespore-specific genes are transcribed by twoσ-factors,σFfollowed byσG. The gene encodingσG(sigG) is transcribed byσF, but also requires the activity of one of the mother-cell-specificσ-factors,σE, for its expression. The minimal promoter required for dependence onσEwas found to stretch to just upstream of the −35 site. Analysis of mutantsigGpromoters generated by site-directed mutagenesis andsigGpromoters from other species suggests the presence of a binding site for a transcriptional repressor within thesigGpromoter region. Replacement of the wild-type promoter withσE-independent promoters resulted in impairment of sporulation. These data support the idea thatσEactivity is required for the transcription ofsigG.