Characterization of cysteine protease-like genes in the striped rice stem borer, Chilo suppressalis

The striped rice stem borer, Chilo suppressalis (Walker), is a major pest for rice production in China and the rest of Southeast Asia. Chemical control is the main means to alleviate losses due to this pest, which causes serious environmental pollution. An effective and environmentally friendly approach is needed for the management of the striped rice stem borer. Cysteine proteases in insects could be useful targets for pest management either through engineering plant protease inhibitors, targeting insect digestive cysteine proteases, or through RNA interference-based silencing of cysteine proteases, disrupting developmental regulation of insects. In this study, eight cysteine protease-like genes were identified and partially characterized. The genes CCO2 and CCL4 were exclusively expressed in the larval gut, and their expression was affected by the state of nutrition in the insect. The expression of CCL2, CCL3, and CCO1 was significantly affected by the type of host plant, suggesting a role in host plant - insect interactions. Our initial characterization of the striped rice stem borer cysteine protease-like genes provides a foundation for further research on this important group of genes in this major insect pest of rice.