LAUSR

Insecticidal crystal (Cry) proteins produced by the bacterium Bacillus thuringiensis (Bt) are toxic to a diverse range of insects. Transgenic rice expressing Cry1A, Cry2A and Cry1C toxins have been developed that are lethal to Chilo suppressalis, a devastating insect pest of rice in China. Identifying the mechanisms underlying the interactions of Cry toxins with susceptible hosts will improve both our understanding of Cry protein toxicology and long‐term efficacy of Bt crops. In this study, we tested the hypothesis that V‐ATPase subunit A contributes to the action of Cry1Ab/1Ac, Cry2Aa and Cry1Ca toxins in C. suppressalis. The full‐length V‐ATPase subunit A transcript was initially cloned from the C. suppressalis larval midgut and then used to generate double‐stranded RNA (dsRNA)‐producing bacteria. Toxicity assays using transgenic rice lines TT51 (Cry1Ab and Cry1Ac fusion genes), T2A‐1 (Cry2Aa), and T1C‐19 (Cry1Ca) in conjunction with V‐ATPase subunit A dsRNA‐treated C. suppressalis larvae revealed significantly reduced larval susceptibility to T2A‐1 and T1C‐19 transgenic rice, but not to TT51 rice. These results suggest that the V‐ATPase subunit A plays a crucial role in mediating Cry2Aa and Cry1Ca toxicity in C. suppressalis. These findings will have significant implications on the development of future resistance management tools.