LAUSR

BACKGROUND Recent work has shown that two codling moth (Cydia pomonella) glutathione S-transferase genes (GSTs), CpGSTd1 and CpGSTd3, can metabolize λ-cyhalothrin, one of the recommended insecticides for C. pomonella control worldwide. However, systematical characterization of delta and epsilon GSTs, especially their potential contributions in metabolism of λ-cyhalothrin is currently still lacking in C. pomonella. RESULTS In this study, a total of nine cDNA sequences were identified in C. pomonella, including 4 in the delta, 5 in epsilon subclasses. RT-qPCR showed that 7 GSTs were ubiquitously expressed at all developmental stages, and CpGSTe2, CpGSTe3, and CpGSTe4 were mainly expressed in larvae. The mRNA levels of CpGSTd2, CpGSTd4 and CpGSTe5 were significantly higher in male than in female adults. Tissue-specific expression analysis revealed that the CpGSTe2, CpGSTe3, and CpGSTe4 were highly expressed in the midgut while CpGSTd2 and CpGSTd4 were predominantly expressed in the Malpighian tubules. The transcripts of these GSTs (except CpGSTe1) were co-expressed following exposure to LD10 of λ-cyhalothrin for 3 h. Recombinant CpGSTd4, CpGSTe2, and CpGSTe3 proteins expressed in Escherichia coli displayed glutathione-conjugating activity towards 1-chloro-2,4-dinitrobenzene (CDNB). In addition, λ-cyhalothrin could inhibit the activity of recombinant CpGSTd4, CpGSTe2, and CpGSTe3 enzymes, but only recombinant CpGSTe3 showed λ-cyhalothrin metabolic capacity, with 21.88±1.09 % of parental compound being depleted within 1 h. CONCLUSION These data show that CpGSTe3 is a third GST gene, encoding an enzyme that metabolizes λ-cyhalothrin in C. pomonella. This article is protected by copyright. All rights reserved.