Expression of the genes for insecticidal crystal proteins inBacillus thuringiensis: cryIVA, notcryIVB, is transcribed by RNA polymerase containingσHand that containingσE

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Abstract
To investigate the mechanism of transcriptional regulation of cryIVA and ctyIVB, encoding 130-kDa dipteran-active crystal proteins, in Bacillus thuringiensis subsp. israelensis, we introduced each gene into several sporulation mutants of Bacillus sub tills. A spoIIG mutation, the wild-type gene of which encodes σE precursor, completely blocked the cryIVB transcription. In contrast, low but detectable transcription of cryIVA was observed in the spoIIG mutant. In the wild-type B. subtilis, no transcription of cryIVB was detected before T2 (2 h after the onset of stationary phase), while the cryIVA transcription started at the late exponential phase at low levels. Furthermore, in a wild-type strain of B. thuringiensis subsp. israelensis, transcription of cryIVA began earlier than that of genes encoding other crystal components, cryIVB and cytA. A consensus sequence recognized by an RNA polymerase containing σH of B. subtilis was found upstream of the transcription start point of cryIVA, which overlapped with that recognized by σE.