Abstract

Simple SummaryThe efficiency of Lepidoptera RNA interference (RNAi) is highly varied among different species, different periods, and different genes. The stability of dsRNA is one of the important factors. DsRNA-degrading enzymes (dsRNases) are the key factors affecting the stability of dsRNA in insects. The efficiency of RNAi in diamondback moths was low and unstable. Furthermore, in vitro experiments, we found that dsRNA was completely degraded when incubated with the hemolymph or gut fluid of diamondback moths. Therefore, we hypothesized that the efficiency of RNAi in diamondback moths was decreased predominantly due to degradation of dsRNA by dsRNase. In this study, we identified four dsRNases in diamondback moths:PxdsRNase1was mainly expressed in the hemolymph; andPxdsRNase2andPxdsRNase3were mainly expressed in the intestinal tract. PxdsRNase1, PxdsRNase2, and PxdsRNase3 were verified to be involved in the RNAi process in diamondback moths. In vitro, the recombinant protein of PxdsRNase1 degraded dsRNA completely and PxdsRNase3 cleaved dsRNA without complete degradation. Overall, our findings provided a fundamental basis for understanding the mechanism of dsRNase involvement in the RNAi process and using RNAi to control diamondback moths in the future.AbstractDsRNA-degrading enzymes (dsRNases) have been recognized as important factors in reducing RNA interference (RNAi) efficiency in different insect species. However, dsRNases inPlutella xylostellaare still unknown. We identified the full-length cDNAs ofPxdsRNase1,PxdsRNase2,PxdsRNase3, andPxdsRNase4. Gene expression profile showed thatPxdsRNase1was mainly expressed in the hemolymph; and thatPxdsRNase2andPxdsRNase3were mainly expressed in the intestinal tract. The expression ofPxCht(ChitinaseofP. xylostella) inP. xylostellalarvae injected with the mixture of dsPxCht (dsRNA ofPxCht) and dsPxdsRNase1 (dsRNA ofPxdsRNase1), dsPxdsRNase2 (dsRNA ofPxdsRNase2), or dsPxdsRNase3 (dsRNA ofPxdsRNase3) was significantly h