Candidate detoxification-related genes in brown planthopper, Nilaparvata lugens, in response to β-asarone based on transcriptomic analysis

Nilaparvata lugens (Stal) is a serious pest of rice and has evolved different levels of resistance against most chemical pesticides. beta-asarone is the main bioactive insecticidal compound of Acorus calamus L. that shows strong insecticidal activity against pests. In this study, we conducted a bioassay experiment to determine the contact toxicity of beta-asarone to N. lugens nymphs. The LD30 sublethal dose was 0.106 mu g per nymph, with 95% confidence limits of 0.070-0.140 mu g. We applied the LD30 concentration of beta-asarone to nymphs for 24 h or 72 h and then performed a transcriptome sequence analysis by referencing the N. lugens genome to characterize the variation. The transcriptomic analysis showed that several GO terms and KEGG pathways presented significant changes. Individually, 126 differentially expressed genes (DEGs), including 72 upregulated and 54 down regulated genes, were identified at 24 h, and 1771 DEGs, including 882 upregulated and 889 downregulated genes, were identified at 72 h. From the DEGs, we identified a total of 40 detoxification-related genes, including eighteen Cytochrome P450 monooxygenase genes (P450s), three Glutathione S-transferase genes, one Carboxylesterase gene, twelve UDP-glucosyltransferases and six ATP-binding cassette genes. We selected the eighteen P450s for subsequent verification by quantitative PCR. These findings indicated that beta-asarone presented strong contact toxicity to N. lugens nymphs and induced obvious variation of detoxification-related genes that may be involved in the response to beta-asarone.