Upregulation of cytochrome p450s following exposure of the silkmoth, Bombyx mori to insecticides

The cytochrome P450 (CYP) superfamily is a highly diversified set of heme-containing proteins that is found in all domains of life, including bacteria, fungi, plants, and animals (Werck-Reichhart and Feyereisen, 2000). CYPs are associated with the catalysis of hydroxylation, dealkylation, and epoxidation (Guengerich, 2001). Through these reactions, CYPs play an important role in the metabolism of xenobiotics, such as pesticides, drugs, pollutants, and naturally occurring toxins, as well as endogenous compounds, including vitamins and steroids (Inouye and Sakaki, 2001; Nebert and Russell, 2002). In insects, CYPs are also involved in the metabolism of hormones and a wide variety of chemicals of natural or synthetic origin, such as plant secondary metabolites and insecticides (Capdevila and Falck, 2001; Capdevila et al., 2002; Kikuta et al., 2002; Oyekan et al., 1998). However, there is little information on the molecular characteristics of CYPs in Lepidoptera, and the relationship between CYPs and insecticide metabolism in the silkmoth has not yet been elucidated. During the course of our studies to identify insecticideinduced mRNAs in the silkmoth, we revealed the mRNA levels of the CYPs that were expressed following the exposure of the silkmoth to insecticides. Previously, we characterized the CYP mRNAs (cyp4M5, cyp6AB4, cyp9A20, and cyp9A22) induced with chemical exposure using microarray experiments (Yamamoto et al., 2010). In this study, we further investigated the different CYPs induced in the silkmoth, Bombyx mori. The expression patterns of CYP mRNAs were examined in response to insecticide treatments by quantitative PCR (qPCR). Many insect pests of agricultural importance are lepidopterans. As the silkmoth is a model animal for lepidopteran insects, it is important to understand its capacity for detoxification, and also the role played by the induced CYPs in the current study. This knowledge can then be applied to other pests.