Characterization and potential mechanism of resistance to double-stranded RNA in willow leaf beetle, Plagiodera versicolora

RNAi-based pesticides have emerged gradually in recent decades and are believed to be the next generation of pesticides. Although resistance to RNA pesticides has been developed and selected in the laboratory in western corn rootworm and Colorado potato beetle, whether RNAi resistance is a general phenomenon in other coleopteran insects and the underlying mechanism of resistance to RNA pesticides are still unclear. Here, we report the development of a highly dsRNA-resistant (> 4110-fold) population (Pv-30R) of Plagiodera versicolora after seven episodes of selection by feeding a laboratory-reared susceptible population (Pv-S) with the leaves of willow plants coated with dsRNA targeting a signal recognition particle protein 54 k (Srp54k) gene. We showed that Pv-30R was cross-resistant to other dsRNAs (dsActin and dsSnap) but susceptible to the Cry3Bb protein from Bacillus thuringiensis, and the resistance was an autosomal and recessive trait. Although no significant differences of the dsRNA stability in the midgut of larvae between Pv-S and Pv-30R were observed, uptake of dsRNA in the midgut tissue of larvae from Pv-30R was disrupted. Overall, these results demonstrate that high levels of resistance to RNA pesticides can developed quickly in P. versicolora in laboratory condition as observed before for other coleopterans, and possibly sharing similar mechanisms of resistance to dsRNA.