Transcriptional regulation of the Bacillus thuringiensis subsp. thompsoni crystal protein gene operon.

The two predominant polypeptides of the Bacillus thuringiensis subsp. thompsoni crystal are encoded by the cry40 and cry34 genes. These crystal protein genes are located in an operon. Western analysis (immunoblotting) demonstrated that the operon promoter activity was located in the region upstream of the cry40 gene. The Cry34 protein was expressed only when the upstream promoter region was present. The crystal protein genes are the only cistrons in the operon, and they are expressed during sporulation, with the highest transcript levels detected early in sporulation (1.5 to 3 h after the onset of sporulation). Transcription initiates from two adjacent sites located 84 and 85 bases upstream of the cry40 translational start codon. The B. thuringiensis subsp. thompsoni crystal protein gene operon promoter aligned with other crystal protein gene promoters, which are activated from early to midsporulation and transcribed in vitro by the B. thuringiensis RNA polymerase E sigma 35.