TRANSCRIPTIONAL REGULATION OF THE CRYIVD GENE OPERON FROM BACILLUS-THURINGIENSIS SUBSP ISRAELENSIS

The CryIVD protein is involved in the overall toxicity of the Bacillus thuringiensis subsp. israelensis parasporal inclusions and is one of the four major components of the crystals. Determination of the DNA se quence indicated that the cryIVD gene is the second gene of an operon which includes three genes. The first one encodes a 19-kDa polypeptide and has sequence homology with the orf1 gene of the Bacillus thuringi ensis cryIIA and cryIIC operons. The second and third genes have alrea dy been identified and encode the CryIVD crystal protein and the P20 p olypeptide, respectively. The promoter region was located by deletion analysis, and the 5' end of the mRNA was determined by primer extensio n mapping. Transcription of the cryIVD gene in B. thuringiensis subsp. israelensis strains is induced 9 h after the beginning of sporulation . Sequence analysis indicated two potential promoters, a strong one an d a weak one, recognized respectively by the RNA polymerase associated with the sigma(35) Or the sigma(28) factor of B. thuringiensis (sigma (E) and sigma(K) of Bacillus subtilis, respectively). Transcriptional lacZ fusion integrated in single copy into the chromosome of various B . subtilis sporulation mutants confirmed the sigma(E) dependence of cr yIVD gene transcription.