Functional analysis of a carboxylesterase gene involved in beta‐cypermethrin and phoxim resistance in Plutella xylostella (L.)

Abstract

BACKGROUND Carboxylesterases (CarEs) are associated with detoxification of xenobiotics, including insecticides, in organism bodies. Overexpression of CarE genes is considered to have an important role in insecticide resistance in insects, however its involvement in multi‐insecticide resistance has rarely been reported. This study aimed to assess the function of a CarE gene (PxαE8) in resistance to five insecticides in Plutella xylostella. RESULTS Relative expression of PxαE8 in three multi‐insecticide‐resistant Plutella xylostella populations, GD‐2017, GD‐2019 and HN, was14.8‐, 19.5‐ and 28.0‐fold higher than that in the susceptible population. Exposure to lethal concentrations associated with 25% mortality (LC₂₅) of beta‐cypermethrin, chlorantraniliprole, metaflumizone, phoxim and tebufenozide could induce the specific activity of CarEs and increase the relative expression of PxαE8. By contrast, knockdown of PxαE8 expression dramatically reduced the activity of CarEs and increased the resistance of P. xylostella (GD‐2019) larvae to beta‐cypermethrin and phoxim by 47.4% and 45.5%, respectively. Further, a transgenic line of Drosophila melanogaster overexpressing PxαE8 was constructed and the bioassay results showed that the tolerance of transgenic Drosophila to beta‐cypermethrin and phoxim was 3.93‐ and 3.98‐fold higher than that of the untransgenic line. CONCLUSION These results provide evidence that overexpression of PxαE8 is involved in resistance, at least to beta‐cypermethrin and phoxim, in multi‐insecticide‐resistant P. xylostella populations, which could help in further understanding the molecular mechanisms of multi‐insecticide resistance in this pest.