No abstract

The mutant sigA allele of Bacilus subtilis DB1005 was confirmed to be temperature sensitive (ts) and transferable among strains of B. subtilis by chromosomal transformation and gene conversion. This ts sigA allele had a pleiotropic eflect on gene expression of DB1005. The induction of certain heat shock proteins in DB1005 was markedly less significant than that observed in the wild-type strain (DB2) under heat stress. In contrast, some proteins required for coping with oxidative stress and glucose starvation were induced abruptly in DB1005 but not in DB2. Heat induction of the groEL gene in vivo at both transcription and translation levels was much lower in DB1005 than in DB2. Besides, the putative cA-type promoter from the groESL operon of B. subtilis was able to be transcribed by the reconstituted or4 RNA polymerase in vitro at both 37 and 49°C. These results strongly suggest that the expression of the groEL gene of B. subtilis under heat stress is regulated at least in part by e at the level of transcription. Our results also showed that DB1005 did not respond too differently from the wild type to ethanol stress, except after a relatively long exposure.CA factor ofBacillus subtilis plays important roles both in the maintenance of vegetative growth and in the regulation of sporulation. To study the structural and functional properties as well as the roles of oA in the regulation of B. subtilis cell development, we constructed a temperature-sensitive (ts) sigA mutant named DB1005. Our data showed that the temperature sensitivity of this mutant did not result from a rapid degradation of the ts CA protein (8); other causes should be responsible for the defect. Therefore, the characterization of this mutant under heat stress becomes our main interest for the moment.It is known that a characteristic set of proteins is induced in nearly all organisms under heat shock and other forms of environmental stress (26,27,33). In Escherichia coli, the heat shock protein genes are under the control of a minor sigma factor, cr32 (18,43). The heat shock response of B. subtilis in several strains of bacilli has been studied (1, 30, 44); however, the mechanism of its regulation remains unclear. The q28 RNA polymerase was once thought to transcribe the heat shock genes of B. subtilis because of its overlapping promoter specificity with E. coli cr32 RNA polymerase (2). However, experiments which disrupted the structural gene of u28 demonstrated that this or affected only the transcription of flagellar and possibly other chemotaxis genes (20) but had nothing to do with heat shock. Recent studies indicated that the transcription starting sites of certain heat shock protein genes (groESL operon and dnaK locus) of B. subtilis were preceded by a ca'-type promoter, and no other promoter sequences recognizable by other sigma factors were identified (25,47