Abstract: Enhancement in cytochrome P450-catalyzed oxidative metabolism is a major factor responsible for pyrethroid resistance in cotton bollworm Helicoverpa armigera, and constitutive overexpression of CYP9A12 was associated with pyrethroid resistance. To examine the involvement of cytochrome P450 gene CYP9A12 in pyrethroid metabolism, we measured the metabolism of deltamethrin, cyhalothrin, fenpropathrin and bifenthrin by CYP9A12 expressed in Saccharomyces cerevisiae. The metabolism rates of heterologously expressed CYP9A12 against deltamethrin, cyhalothrin and fenpropathrin were 8.58, 5.85 and 3.94 pmol/min·mg protein, respectively. No fenpropathrin metabolism was detected in CYP9A12 containing yeast cell lysates. This study showed that CYP9A12 has the capacity to metabolize several pyrethroids, providing direct evidence for the involvement of CYP9A12 in pyrethroid resistance in H. armigera.

Key words: Helicoverpa armigera, cytochrome P450, CYP9A12, heterologous expression, Saccharomyces cerevisiae, pyrethroid metabolism