Identification and Functional Characterization of a Sigma Glutathione S-Transferase Involved in λ-Cyhalothrin Resistance in the Codling Moth .

The codling moth, (L.), is a quarantine pest of global significance impacting pome fruits and walnuts. It has evolved resistance to many commonly used insecticides including λ-cyhalothrin. Glutathione S-transferases (GSTs) are multifunctional enzymes playing a crucial role in the detoxification of insecticides in insects. However, the role of specific GST gene in λ-cyhalothrin resistance in is unclear. In this study, we identified three sigma-class genes (, , and ). These genes were ubiquitously expressed at all developmental stages, and of these, the expression level of in the larval stage was significantly higher than in the egg, pupal, and adult stages. Moreover, was predominantly expressed in the fat body while lower levels in the cuticle. In addition to exposure of larvae to LD of λ-cyhalothrin elevating the expression level of , mRNA levels of in a field population (ZW_R) from northeast China, which has developed moderate level resistance to λ-cyhalothrin, was significantly higher than that of susceptible strains. In vitro inhibition assays demonstrated that λ-cyhalothrin inhibited the conjugating activities of recombinant CpGSTs2, and metabolic assays indicated that λ-cyhalothrin could be depleted by recombinant . These results bring evidence for the involvement of in in resistance to λ-cyhalothrin.