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The brown planthopper, Nilapavata lugens, is one of the most serious rice plant pests, which causes extensive rice losses in Asia countries. Wide use of insecticides has resulted in increased insecticide resistance in this pest. Cytochrome P450monooxygenase is a superfamily of heme proteins, which partipicates in oxidative metabolism of endogenous and exogenous compounds. In insects, a substantial amount of research has indicated that cytochrome P450enzyme system plays important roles in detoxifying metabolism of insecticides and plant toxins. Carboxylesterase belongs to α/β hydrolase fold protein family, which comprises of a multigene family and can effectively hydrolyze the endogenous and exogenous compounds containing carboxylester, amide, and thioester bonds. In insects, the research related to carboxylesterase is mainly focused on its involvement in insecticide resistance. Currently, the N. lugens genomic sequencing project has been accomplished. A great number of genomic as well as transcriptomic sequences provided the great convenience to study novel genes and their biological functions. The clarification of the molecular mechanisms of the cytochrome P450and carboxylesterase family genes will facilitate the understanding about the physiological functions of the two enzyme families, which will provide the valuable clues for controlling this pest. In this study, a total of41cytochrome P450and23carboxylesterase genes were identified in N. lugens by using bioinformatic and molecular biological approaches. The evolutionary relationships between these genes were analyzed at the gene level. The effects of sevral insecticides including imidacloprid, triazophas and deltamethrin on N. lugens detoxifying enzyme genes were studied. Among them, the expressions of nine cytochrome P450genes, which are NLU028704(CYP4), CYP6ER1, CYP4CE1, CYP4C61, CYP417A1, CYP6CW1, CYP6CS1, CYP18a1, NLU022549(CYP4), were significantly up-regulated when exposure to the imidacloprid treatment. Functions of NLU028704(CYP4) and CYP6ER1genes were studied using the RNA interference method. The susceptibility of N. lugens nymphs to the imidacloprid treatment was increased after dsCYP6ERl injection, but there was no significant difference after dsCYP4injection, implying that CYP6ER1gene palys an important role in imidacloprid metabolism.
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