EXPRESSION OF MOSQUITOCIDAL CRYSTAL PROTEIN GENES IN NONINSECTICIDAL BACILLUS-THURINGIENSIS SUBSP ISRAELENSIS

Bacillus thuringiensis NTB-1 isolated from soil samples in Korea produ ces ovoidal parasporal inclusions with proteins of approximately 2-40 kDa in size. Although serological study indicated that the isolate has a flagella (H) antigen identical with subsp. israelensis, it seemed t o be non-insecticidal against Lepidoptera and Coleoptera as well as Di ptera. To investigate the activity of non-insecticidal B. thuringiensi s transformed with insecticidal crystal protein genes, cryIVD and cytA genes of B. thuringiensis subsp. morrisoni PG-14, highly toxic to mos quito larvae, were introduced into the isolate NTB-1. The expression o f mosquitocidal crystal protein genes in NTB-1 was characterized by SD S-PAGE analysis and electron microscopy. The results showed that cryst alline inclusions of host, CryIVD and CytA were stably expressed in th e transformant. However, the mosquitocidal activity of transformant wa s similar to that of B. thuringiensis subsp. kurstaki Cry(-) B harbour ing cryIVD and cytA genes, demonstrating that a synergistic effect by an interaction of both introduced insecticidal and resident non-insect icidal crystal proteins was not observed.