Highly insect-resistant transgenic tobacco plants containing both B.t. and CpTI genes

The cowpea trypsin inhibitor (CpTI) gene was synthesized according to its cDNA sequence using DNA synthesizer and confirmed by DNA sequencing. The CpTI gene and modified Bacillus thuringiensis (B.t.) delta-endotoxin gene were cotransformed to tobacco explants mediated by Agrobacterium tumefaciens. The integrations of B.t and CpTI genes were confirmed by PCR and Southern hybridization. Three kinds of transgenic plants were obtained: (1) containing CpTI gene, (2) containing B.t gene, (3) containing both CpTI and B.t genes. Bioassays showed that all these transgenic plants were toxic to the larvae of Heliothis armigera and that the tobacco plants containing both genes had enhanced toxicity to larvae by comparison with plants containing only CpTI or B.t gene.