Cytochrome P450 monooxygenases (P450s) play important roles in the detoxification metabolism of xenobiotics and are involved in the resistance of insects to many insecticides. In this study, piperonyl butoxide (PBO), an inhibitor of P450 enzyme activity, significantly increased the toxicity of clothianidin in the clothianidin-resistant (CL-R) population of Bradysia odoriphaga. The enzyme activity of P450 in the CL-R population was significantly higher than that in the SS population. Furthermore, four P450 genes were found to be significantly overexpressed in the CL-R population. Tissue-specific expression analysis indicates that CYP9J57, CYP3828A1, CYP6SX1, and CYP6QE1 were most highly expressed in the midgut and/or Malpighian tubules. After exposure to LC 30 of clothianidin, the expression levels of the four P450 genes were significantly upregulated. The RNAi-mediated knockdown of CYP9J57, CYP3828A1, and CYP6QE1 significantly increased the susceptibility of B. odoriphaga to clothianidin. These results suggest that P450 genes are involved in clothianidin resistance in B. odoriphaga. This provides a better understanding of P450-mediated clothianidin resistance in B. odoriphaga and will contribute to the management of insect resistance to insecticides.
Carboxylesterases
(CarEs) are a multigene superfamily of metabolic
enzymes involved in metabolic detoxification of xenobiotics. In this
study, an α-esterase gene (BoαE1) was identified from Bradysia odoriphaga. Phylogenetic
analysis classified BoαE1 into the α-esterase clade. Developmental expression analysis
indicated that BoαE1 was significantly expressed
in the second to fourth larval stages. Tissue-specific expression
analysis indicated that BoαE1 was highly expressed
in the larval midgut. After exposure to LC30 of malathion,
the CarE activity of B. odoriphaga was induced and
the transcriptional level of BoαE1 was significantly
up-regulated. Silencing of BoαE1 significantly
increased the susceptibility of B. odoriphaga larvae
to malathion. Inhibition assays in vitro indicated
that malathion significantly inhibited BoαE1 activity. GC-MS
assay showed that BoαE1 possesses hydrolase activity toward
malathion and participates in the detoxification of malathion. These
results strongly suggest that BoαE1 plays a
crucial role in detoxification of malathion in B. odoriphaga.
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