Characterization of carboxylesterase PxαE8 and its role in multi-insecticide resistance in Plutella xylostella (L.)

Abstract

Carboxylesterase (CarE) was considered as important phase-I detoxifying enzymes which participated in detoxification of different types of insecticides. Up-regulation of CarE genes has been proved playing a major role in insecticide resistance in many pest insects, but its involvement in resistance to insecticides in Plutella xylostella has been rarely reported. In this study, a CarE cDNA named PxαE8 was identified in P. xylostella, which has an open reading frame of 1 599 nucleotides and putatively encodes 532 amino acids. The investigation of spatial expression profiles of PxαE8 revealed that it was expressed in all developmental stages, especially in larvae and adults. The body part/tissue-specific expression profiles showed that the PxαE8 mainly expressed in fat body, malpighian tubule and hemolymph of larvae. Further, the relative expression of PxαE8 in two multi-resistant field populations, Hainan (HN) and Guangdong (GD) populations, was found 24.4- and 15.5-fold higher than that in susceptible population, respectively. Knockdown of PxαE8 by RNA interference dramatically increased the mortalities of larvae of HN population treated with LC50 of beta-cypermethrin and phoxim by 25.3 and 18.3%, respectively. These results suggested that up-regulation of PxαE8 was involved in resistance to both beta-cypermethrin and phoxim in P. xylostella, which shed light on further understanding of molecular mechanisms of multi-insecticide-resistance in P. xylostella and other pest insects.