Functional Analysis of Two Carboxylesterase Genes AsCarE13 and AsCarE15 Associated with Lambda-Cyhalothrin Resistance in Aphis spiraecola.

Carboxylesterases (CarEs) are critical enzymes involved in insecticide resistance, yet their specific roles in pyrethroid resistance of Aphis spiraecola remain unclear. In this study, enzymatic activity and synergism bioassays initially implicated CarE involvement in lambda-cyhalothrin resistance of A. spiraecola. RT-qPCR revealed that AsCarE13 and AsCarE15 were significantly upregulated in the lambda-cyhalothrin resistant strain (LC-R), with predominant expression in the gut and hemolymph, and marked inducibility upon insecticide exposure. RNAi of AsCarE13 and AsCarE15 significantly increased the susceptibility of A. spiraecola to lambda-cyhalothrin by 45.99% and 29.86%, respectively. In contrast to AsCarE15, recombinant AsCarE13 displayed strong α-NA hydrolytic activity and was competitively inhibited by lambda-cyhalothrin. HPLC and GC-MS/MS analyses further confirmed that AsCarE13 efficiently hydrolyzed lambda-cyhalothrin to yield 3-phenoxybenzaldehyde, whereas no obvious metabolism was detected for AsCarE15. These results suggest that AsCarE13 plays a key role in the metabolic detoxification of lambda-cyhalothrin in A. spiraecola.