Soybean Kunitz trypsin inhibitor (SKTI) confers resistance to the brown planthopper (Nilaparvata lugens Stal) in transgenic rice

Proteinase inhibitors are widely distributed in animals, plants and microorganisms and their roles in plants are associated with defense against pests. The utilization of proteinase inhibitors for crop protection has been actively investigated with a variety of proteinase inhibitors. Soybean Kunitz trypsin inhibitor (SKTI), one of the major seed storage protein, is synthesized for a short period during seed development. To investigate the role of SKTI in a plant's defense system against insect predation, a recombinant plasmid containing the full-length cDNA of SKTI under control of the CaMV 35S promoter was introduced into rice protoplasts by using the PEG direct gene transfer method and a large number of transgenic rice plants were regenerated. The integration, expression, and inheritance of this gene was demonstrated in R₁ and R₂ generations by Southern, northern, and western analyses. Accumulation levels (0.05-2.5% of soluble proteins) of SKTI protein were detected in R₁ and R₂ plants. Bioassay with R₁ and R₂ transgenic plants revealed that transgenic plants are more resistant to destructive insect pest of rice, brown planthopper (Nilaparvata lugens Stal), than the control plants. Thus, introduction of SKTI into rice plants can be used to control insect pests.