Metabolic functional redundancy of the CYP9A subfamily members leads to P450-mediated lambda-cyhalothrin resistance in Cydia pomonella

Abstract

BACKGROUND: The evolution of insect resistance to pesticides poses a continuing threat to sustainable pest management. While much is known about the molecular mechanisms that confer resistance in model insects and few agricultural pests, far less is known about fruit pests. RESULTS: Here we found that functional redundancy and preference of metabolism by cytochrome P450 monooxygenases (P450s) genes in the CYP9A subfamily confer resistance to lambda-cyhalothrin in Cydia pomonella, a major invasive pest of pome fruit. A total of four CYP9A genes, including CYP9A61, CYP9A120, CYP9A121, and CYP9A122, were identified from C. pomonella. Among these, CYP9A120, CYP9A121, and CYP9A122 were predominantly expressed in the midgut of larvae. The expression levels of these P450 genes were significantly induced by LD10 of lambda-cyhalothrin and were overexpressed in a field-evolved lambda-cyhalothrin resistant population. Knockdown of CYP9A120 and CYP9A121 by RNA-mediated interference (RNAi) increased the susceptibility of larvae to lambda-cyhalothrin. In vitro assays demonstrated that recombinant P450s expressed in Sf9 cells can metabolize lambda-cyhalothrin, but with functional redundancy and divergence through regioselectivity of metabolism. CYP9A121 preferred to convert lambda-cyhalothrin to 2′-hydroxy-lambda-cyhalothrin, whereas CYP9A122 only generated 4′-hydroxy metabolite of lambda-cyhalothrin. Although possesses a relatively low metabolic capability, CYP9A120 balanced catalytic competence to generate both 2′- and 4′-metabolites. CONCLUSION: Collectively, these results reveal that metabolic functional redundancy of three members of the CYP9A subfamily leads to P450-mediated lambda-cyhalothrin resistance in C. pomonella, thus representing a potential adaptive evolutionary strategy during its worldwide expansion.

Transcription Factor AhR Regulates Glutathione S-Transferases Conferring Resistance to lambda-Cyhalothrin in Cydia pomonella

“…Among these, the expression of CpGSTe3 was downregulated by 58.56%, which was significantly higher than those of CpCYP9A121 and CpCYP9A122. In addition, inconsistent with our previous findings that the knockdown of CpCYP9A120 and CpCY-P9A121 reduced the total activity of P450, 9 downregulation of CpCYP9A121 and CpCYP9A122 by silencing of CpAhR did not reduce the activity of P450 in this study. These results imply that CpGSTe3 was more likely to be regulated by AhR than CYP9A genes.…”

“…52 Interestingly, in this study, we found that CpAhR co-regulated the expression of GST and P450 genes in C. pomonella. The mRNA levels of CpGSTe3, CpCYP9A121, and CpCYP9A122 were significantly decreased after injection of dsCpAhR, indicating that the expression of these previously documented lambda-cyhalothrin resistancerelated genes 8,9 is likely cis-regulated by CpAhR. Among these, the expression of CpGSTe3 was downregulated by 58.56%, which was significantly higher than those of CpCYP9A121 and CpCYP9A122.…”

“…RNA interference (RNAi) has been established with robust interference efficiency targeting CYP9A genes in C. pomonella . In this study, the mRNA level of CpAhR was knockdown via RNAi and with the highest interference efficiency (49.11%) after the injection of dsCpAhR for 36 h. Therefore, this time point was selected to determine the change of tolerance of larvae to lambda -cyhalothrin, and the result implied that CpAhR is involved in the regulation of tolerance to lambda -cyhalothrin because larval mortality increased when challenging with LD 50 of lambda -cyhalothrin after injection of dsCpAhR.…”

“…RNA interference (RNAi) has been established with robust interference efficiency targeting CYP9A genes in C. pomonella. 9 In this study, the mRNA level of CpAhR was knockdown via RNAi and with the highest interference efficiency (49.11%) after the injection of dsCpAhR for 36 h. Therefore, this time point was selected to determine the change of tolerance of larvae to lambda-cyhalothrin, and the result implied that CpAhR is involved in the regulation of tolerance to lambdacyhalothrin because larval mortality increased when challenging with LD 50 of lambda-cyhalothrin after injection of dsCpAhR. We further found that silencing of CpAhR reduced the total activity of GST, whereas the activity of P450 did not change significantly, indicating that CpAhR enhances the tolerance of C. pomonella larvae to lambda-cyhalothrin by increasing the activity of the GST enzyme, implying that CpAhR probably regulates the expression of GST genes involved in lambda-cyhalothrin resistance and further affects the activity of the enzyme they encoded.…”

Transcription factor AhR regulates glutathione S-transferases (GSTs) conferring resistance tolambda-cyhalothrin inCydia pomonella

“…Recently, the recombinant proteins of CpGSTd1, CpGSTd3, CpGSTe3, and CpGSTs2 were found to be able to metabolize lambda -cyhalothrin via sequestration, implying that GSTs may be involved in the resistance of lambda -cyhalothrin [8]. In addition, it is confirmed that the metabolic functional redundancy of three P450 genes in the CYP9A subfamily leads to P450-mediated lambda -cyhalothrin resistance in C. pomonella [9]. However, the transcriptional regulation mechanism of insecticide resistance genes is unclear in C. pomonella .…”