Abstract: 【Aim】 To study the molecular characterization and biological function of the cytochrome P450 gene LmCYP6FD3 from the migratory locust, Locusta migratoria. 【Methods】 The cytochrome P450 gene sequences were searched from the transcriptome database of L. migratoria, the cDNA fragment of the target gene was cloned using RT-PCR, and its expression patterns in various tissues (gastric caeca, foregut, midgut, hindgut, integument, testis, ovary, muscles, hemolymph, fat body and Malpighian tubules) of the 5th instar nymphs and different developmental stages (egg, 1st-5th instar nymph and adult) were analyzed using real-time quantitative PCR (RT-qPCR). The target gene was silenced by RNA interference (RNAi), the silence efficiency was evaluated by injecting dsRNA to the 2nd instar nymphs， and the susceptibility of the nymphs to three insecticides (malathion, carbaryl and deltamethrin) was assessed. 【Results】 The full-length cDNA of cytochrome P450 gene was cloned (GenBank accession no.: KT316378) and named LmCYP6FD3. Its length is 1 563 bp, encoding 521 amino acids. The expression level of LmCYP6FD3 was the highest in the Malpighian tubules of the 5th instar nymphs, moderate in the hindgut and fat body, and lower in other tissues. LmCYP6FD3 was expressed during the whole developmental period and had relatively higher expression level in the nymphal stage. Insecticide bioassay in combination with RNAi showed that the highest silence efficiency of LmCYP6FD3 was achieved at 24 h after RNAi, and the mortality of the 2nd instar nymphs of L. migratoria in the RNAi treatment group (injection with dsLmCYP6FD3) increased by 32% as compared with that of the control group (injection with dsGFP) after exposure to carbaryl by dipping method. 【Conclusion】 In this study, the full-length of cDNA sequence of LmCYP6FD3 was cloned. This gene has the highest expression level in the Malpighian tubules of L. migratoria and might play a significant role in the detoxification of carbaryl in this locust.

Key words: Cytochrome P450, Locusta migratoria, gene expression, RNA interference, insecticide