Abstract: 【Aim】 This study aims to understand the induction of chlorantranilprole, a novel diamide insecticide, on the expression of cytochrome P450 genes in the midgut of Spodoptera exigua (Hübner) larvae. 【Methods】 The 4th instar larvae of S. exigua were fed on artificial diets containing 0.01 and 0.02 mg/kg of chlorantraniliprole, respectively, until their molting, and the activities of O-deethylase of P450 and the mRNA expression levels of four P450 genes (CYP9A9, CYP4G37,CYP4S11 and CYP6B) and one NADPH cytochrome P450 reductase gene (HQ852049) in the midgut of the 5th instar larvae in 6 to 36 h post treatment were detected by assaying O-deethylation of ethoxyresorufin and quantitative real-time PCR, respectively. 【Results】 The cytochrome P450 ethoxycoumarin-O-deethylase activity in the 0.02 mg/kg treatment group increased to 1.90－2.92-fold as high as the untreated control, while that in 0.01 mg/kg treatment group was only 1.11－1.62fold as high as that of the control. The relative expression levels of CYP9A9, CYP4G37and CYP6B  induced by 0.02 mg/kg chlorantraniliprole were 1.97-3.95, 2.46-4.29 and 1.53-4.48-fold as high as the control, respectively, and 0.02 mg/kg chlorantraniliprole also induced the expression of HQ852049, with the relative expression level of 1.85-4.08-fold as high as the control. 【Conclusion】 The results suggest that the up-regulated expression of three P450 genes and NADPH cytochrome P450 reductase gene  HQ852049 induced by chlorantraniliprole can enhance the activities of P450s in the midgut of S. exigua larvae.

Key words: Spodoptera exigua, cytochrome P450, NADPH cytochrome P450 reductase, chlorantraniliprole, gene induction