A Bacillus subtilis secA mutant, secA12, which is blocked at an early stage of sporulation, is able to grow as well as the wild-type strain at all temperatures tested. Experiments with lacZ fusion genes showed that the induction of kinA expression, as well as the sporulation-specific transcription of the spo0A gene, was not observed in the secA12 mutant. However, transcription of the spo0H gene (coding for sigmaH, which is required for the transcription of kinA and spo0A) and accumulation of the sigmaH protein were not affected in secA12. These results suggested that mutations in secA affect a factor required for efficient transcription of kinA as well as for the activation of the phosphorelay pathway.