Insect-Resistant Rice Generated By Introduction Of A Modified δ-Endotoxin Gene Of Bacillus Thuringiensis

Insect pests cause severe damage to rice production in many regions of the world. As a first step towards development of insect-resistant rice, we introduced into japonica rice a truncated δ-endotoxin gene, cryIA(b) of Bacillus thuringiensis (Bt), which has specific biological activity against lepidopteran insects. For high expression of the cryIA(b) gene in rice, the coding sequence was extensively modified, based on the codon usage of rice genes. Transgenic rice plants efficiently expressed the modified cryIA(b) gene at the levels of mRNA and protein. Bioassays of transgenic rice plants, using R2 generation plants with two major rice insect pests, striped stemborer (Chile suppressalis) and leaf folder (Cnaphalocrosis medinalis), indicated that the transgenic plants are more resistant to the pests than are untransformed plants. Our results suggest that Bt toxin genes are useful for the development of new rice varieties resistant to major insect pests by genetic engineering.