Knockdown of cadherin genes decreases susceptibility of Chilo suppressalis larvae to Bacillus thuringiensis produced Crystal toxins

The striped rice stem borer, Chilo suppressalis Walker, is one of the most destructive rice pests in Asia. Insecticidal crystal proteins (Cry toxins) produced by Bacillus thuringiensis are widely used as biopesticides or in developing transgenic crops for pest management. In this study, we tested the involvement of two newly cloned C. suppressalis cadherins (CsCAD3 and CsCAD4) in the toxicity of Cry1Ab/Ac, Cry2Aa and Cry1Ca. Our results showed that CsCAD4 was expressed highest in the midgut, whereas CsCAD3 was expressed highest in the epidermis. The feeding of double-stranded RNA specific to CsCAD3 and CsCAD4 respectively significantly suppressed the expressions of target gene. The knockdown of CsCAD3 significantly reduced the mortality of larvae to Cry1Ab/Ac, whereas knockdown of CsCAD4 significantly decreased the larval susceptibility to Cry2Aa. In contrast, reduced expressions of CsCAD3 or CsCAD4 were not interacted with larval susceptibility to Cry1Ca. Our results suggest that CsCAD3 and CsCAD4 function in Cry toxin toxicity and these findings will help us to better understand the action mechanism of Cry toxins in C. suppressalis.