IDENTIFICATION OF A BACILLUS-THURINGIENSIS GENE THAT POSITIVELY REGULATES TRANSCRIPTION OF THE PHOSPHATIDYLINOSITOL-SPECIFIC PHOSPHOLIPASE-C GENE AT THE ONSET OF THE STATIONARY-PHASE

A transcriptional analysis of the phosphatidylinositol-specific phosph olipase C (plcA) gene of Bacillus thuringiensis indicated that its tra nscription was activated at the onset of the stationary phase in B. th uringiensis but was not activated in B. subtilis. The B. thuringiensis gene encoding a transcriptional activator required for plcA expressio n was cloned by using a B. subtilis strain carrying a chromosomal plcA '-'lacZ fusion as a heterologous host for selection. This trans activa tor (designated PlcR) is a protein of a calculated molecular weight of 33,762 which appears to be distantly related to PreL and NprA, regula tor proteins enhancing transcription of neutral protease genes during the stationary phase of a Lactobacillus sp. and B. stearothermophilus, respectively. plcR gene transcription was analyzed in B. thuringiensi s and in B. subtilis. PlcR positively regulated its own transcription at the onset of the stationary phase. There is a highly conserved DNA sequence (17 bp) 34 nucleotides upstream from the plcR transcriptional start site and 49 nucleotides upstream from the plcA transcriptional start site. As PlcR positively regulates its own transcription and plc A transcription, this conserved DNA sequence may be the specific recog nition target for PlcR activation.