Restricted Transcription from Sigma H or Phosphorylated Spo0A Dependent Promoters in the Temperature-sensitive secA341 Mutant of Bacillus subtilis

The temperature-sensitive secA341 mutation of Bacillus subtilis affects sporulation and sporulation-associated events as well as protein secretion and cell septation. With lacZ or bgaB fusion genes, we examined the expression of the early sporulation genes in the mutant strain. Transcriptional expression of σH dependent kinA, spo0A (Ps), phrC, spoVG, and citG (p2) genes was blocked by the secA341 mutation at 37°C. On the other hand, neither repression of the abrB gene nor induction of the spo0H (σH) gene was affected. Active RNA polymerase containing σH was, however, found to be produced in the mutant cells. Expression of the phosphorylated Spo0A dependent spoIIG operon was also blocked. Thus the secA341 mutation blocks some step(s) or factor(s) required for σH-dependent transcription in vivo.