CRISPR/Cas9-mediated D472N substitution in the Rdl1 of Plutella xylostella confers low resistance to abamectin.

Abstract

Abamectin is one of the main insecticides used for the control of Plutella xylostella, a destructive pest of cruciferous crops. Target-site mutation plays an important role in insecticide resistance. A point mutation (D472N) has been reported in the Rdl1 γ-aminobutyric acid receptor (GABAR) in P. xylostella, but its roles in insecticide resistance remain unknown. In this study, the D472N mutation of the Rdl1 GABAR was detected in several field populations of P. xylostella and showed a positive correlation with abamectin resistance. A knock-in homozygous mutation strain (D472N-KI) of P. xylostella was successfully constructed using CRISPR/Cas9 coupled with homology-directed repair, and the bioassay results demonstrated that compared with the susceptible strain, the D472N-KI strain had 11.1- and 3.7-fold increased resistance to abamectin and endosulfan, respectively. There was no difference in resistance to fipronil, broflanilide or isocycloseram, which also target the GABAR. In addition, the total fecundity of the D472N-KI strain was significantly reduced by 50.0%. Our results suggest that the homozygous D472N mutation in Rdl1 confers a low level of resistance to abamectin in P. xylostella but causes significant fecundity disadvantages, which may delay the development of resistance to some extent. These results lay a foundation for further understanding the mechanisms of abamectin resistance in insect pests. © 2022 Society of Chemical Industry.