Abstract
Abamectin has been used to control the diamondback moth, Plutella xylostella (P. xylostella), which is a major agricultural pest that can rapidly develop resistance against insecticides including abamectin. Although cytochrome P450 has been confirmed to play an important role in resistance in P. xylostella, the specific P450 genes associated with the resistance are unclear. The full-length cDNA of the cytochrome P450 gene CYP340W1 was cloned and characterized in the present study. The cDNA assembly yielded a sequence of 1929 bp, containing the open reading frame (ORF) 1491 bp and encodes a 496-amino acid peptide. CYP340W1 was expressed in all P. xylostella developmental stages but its expression level was highest in larvae and especially in the heads of larvae. The expression of CYP340W1 was significantly higher in an abamectin-resistant strain (ABM-R) than in its susceptible counterpart (ABM-S). In addition, expression of CYP340W1 was increased when the ABM-R strain was exposed to abamectin. When injected into third-stage ABM-R larvae, CYP340W1 dsRNA significantly reduced CYP340W1 expression at 6 h and reduced expression by 83% at 12 h. As a consequence of RNAi, the mortality of the injected abamectin-resistant larvae increased after a 48-h exposure to abamectin. The results indicate that the overexpression of CYP340W1 plays an important role in abamectin resistance in P. xylostella.