Cloning and expression of the crystal protein genes from Bacillus thuringiensis strain berliner 1715

Abstract

From a clone bank of the entire genome of Bacillus thuringiensis, one clone that contains a plasmid ( pBT 15-88) harboring a sporulation gene was identified by molecular hybridization. This gene, identified as the crystal protein gene, occurs both on a large host plasmid DNA and in the chromosomal DNA in B. thuringiensis strain berliner 1715. The inserted sequence of pBT 15-88, which corresponds to the chromosomal sequence, was not expressed in Escherichia coli. In B. thuringiensis (kurstaki), the crystal gene was found only on a large host plasmid while in B. thuringiensis ( dendrolimus ), it is only on the chromosomal DNA. The plasmid crystal gene was cloned by ligation of a 14-kb BamHI fragment of a host plasmid DNA of 42 megadaltons from strain berliner 1715 into the BamHI site of the bifunctional vector pHV33 . In E. coli and in sporulating B. subtilis the plasmid pBT 42-1 coded for a polypeptide, detected by antibodies against the crystal protein, with the same electrophoretic mobility as the crystal protein of B. thuringiensis. The crystal gene was not expressed in vegetative cells of B. subtilis, suggesting that the control at the transcriptional level is the same in B. subtilis and in B. thuringiensis. Protein extracts from the clones harboring the hybrid plasmid are toxic for the larvae of Pierris brassicae and the protein antigen forms cytoplasmic inclusion bodies in E. coli and B. subtilis, which are visible under the light microscope.