Identification and functional analysis of a cytochrome P450 gene involved in imidacloprid resistance in Bradysia odoriphaga Yang et Zhang.

Insect cytochrome P450 monooxygenases played an important role in detoxifying insecticides which potentially contributed to the metabolic resistance to insecticides. Bradysia odoriphaga, as a major pest of Chinese chive, was reported to be highly tolerant to neonicotinoid insecticides imidacloprid. In this study, a novel P450 gene, CYP6FV12, was cloned from B. odoriphaga. The full-length cDNA sequence of CYP6FV12 is 2520 bp long and its open reading frame (ORF) encodes 519 amino acids. Quantitative real-time PCR showed that the highest expression of CYP6FV12 was observed in fourth-instar larvae, which is 154.32-fold higher than that of eggs. Highest expression of CYP6FV12 was observed in the midgut, followed by fat body, which was 13.67 and 5.42-fold higher than that in cuticle, respectively. The expression of CYP6FV12 was significantly up-regulated in B. odoriphaga larvae after exposed to imidacloprid at the concentrations of 10, 30, 50, and 70 mg/L. Moreover, RNAi mediated silencing of CYP6FV12 increased mortality by 28.62% when the fourth-instar larvae were treated with imidacloprid. This is the first systematic study on isolated P450s gene involved in imidacloprid resistance in B. odoriphaga and increased our understanding of the molecular mechanisms of insecticide detoxification in this pest insect.