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Insect cytochrome P450 monooxygenase (CYP) plays a key role in the detoxification of insecticides. In this study, four cDNA sequences of CYP6 genes were identified and characterized. Transcription levels of LmCYP6HC1 and LmCYP6HCL1 were high in first- and fourth-instar nymph stages, respectively. LmCYP6HN1 was primarily expressed in the egg to third-instar nymph stages, while LmCYP6HQ1 was predominantly expressed in the stages from fourth-instar nymph to the adult. The four CYP6 genes were predominantly distributed in the antenna, brain, fat body, integument, and hemolymph. Piperonyl butoxide exposure inhibited total CYP activity and synergized the toxicity of carbamates and pyrethroids. Knockdown of LmCYP6HL1, LmCYP6HN1, and LmCYP6HQ1 increased nymph mortality following exposure to carbaryl, and silencing of LmCYP6HC1, LmCYP6HL1, LmCYP6HN1, and LmCYP6HQ1 comprehensively raised nymph mortality following exposure to fluvalinate. Knockdown of LmCYP6HL1 or LmCYP6HN1 significantly increased nymph mortality following exposure to cypermethrin or fenvalerate, respectively. These results suggest that the CYP6 family plays a key role in determining the susceptibility of Locusta migratoria to both carbamates and pyrethroids., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Cytochrome P450 monooxygenases (P450s) are important enzymes for biotransformations of various endogenous and xenobiotic substances in various organisms. In this study, we examined microsomal P450 protein content and enzymatic activity in four major detoxification tissues dissected from fifth-instar nymphs of the migratory locust (Locusta migratoria). The highest microsomal P450 protein content was found in the gastric caeca (a part of the midgut), followed by the midgut, Malpighian tubules and fat bodies. Microsomal P450s showed the highest aromatic hydroxylation, O-dealkylation and O-dearylation activities towards six of the seven model substrates examined in the fat bodies. Although the gastric caeca showed the highest P450 protein content, the enzymatic activities towards six of the seven model substrates were the lowest in this tissue. Further, the midgut, gastric caeca and fat bodies showed significant metabolic activities towards two pyrethroid insecticides (deltamethrin and fluvalinate), but no significant activities towards the other four insecticides (malathion, chlorpyrifos, carbaryl and methoprene). These results support our conclusions: 1) total P450 protein content alone cannot be reliably used to predict its enzymatic activity, and 2) insect P450 enzymatic activity is both tissue and substrate dependent., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Background: NADPH-cytochrome P450 reductase (CPR) plays important roles in cytochrome P450-mediated metabolism of endogenous and exogenous compounds, and participates in cytochrome P450-related detoxification of insecticides. However, the CPR from Locusta migratoria has not been well characterized and its function is still undescribed., Results: The full-length of CPR gene from Locusta migratoria (LmCPR) was cloned by RT-PCR based on transcriptome information. The membrane anchor region, and 3 conserved domains (FMN binding domain, connecting domain, FAD/NADPH binding domain) were analyzed by bioinformatics analysis. Phylogenetic analysis showed that LmCPR was grouped in the Orthoptera branch and was more closely related to the CPRs from hemimetabolous insects. The LmCPR gene was ubiquitously expressed at all developmental stages and was the most abundant in the fourth-instar nymphs and the lowest in the egg stage. Tissue-specific expression analysis showed that LmCPR was higher expressed in ovary, hindgut, and integument. The CPR activity was relatively higher in Malpighian tubules and integument. Silencing of LmCPR obviously reduced the enzymatic activity of LmCPR, and enhanced the susceptibility of Locusta migratoria to carbaryl., Conclusion: These results suggest that LmCPR contributes to the susceptibility of L. migratoria to carbaryl and could be considered as a novel target for pest control., (Copyright © 2017 Elsevier Ltd. All rights reserved.)