Abstract: Two novel P450 genes (CYP9A18 and CYP6AE12) from the insecticide-resistant strain (YS-FP) of Helicoverpa armigera (Hübner) were cloned with RT-PCR and RACE. The coding region of CYP6AE12 cDNA is 1 569 bp, encoding a protein of 523 amino acids, while that of CYP9A18 cDNA is 1 590 bp, encoding a protein of 530 amino acids. Using real-time quantitative PCR, mRNA expression levels of CYP6AE12 and CYP9A18 were compared between the resistant strain YS-FP (derived from a susceptible strain YS through laboratory selection) and the YS strain respectively. The results showed that the expression of CYP6AE12 was higher in fat body than in midgut in the 6th instar larvae of both strains, whereas the expression of CYP9A18 was higher in midgut than in fat body. Compared with the YS strain, CYP6AE12 in fat body and midgut of the YS-FP strain was 1.3- and 3.6 fold over-expressed respectively, while CYP9A18 was not over-expressed in both midgut and fat body of the YS-FP strain. The results suggested that CYP6AE12 was probably involved in pyrethroid resistance in the resistant YS-FP strain of H. armigera.

Key words: Helicoverpa armigera, cytochrome P450, real-time PCR, P450 genes