Drosophila X virus-like particles as efficient dsRNA carriers for improved RNAi against the invasive species, Drosophila suzukii

RNA interference (RNAi) has been exploited as a promising strategy for pest control and also has great potential against the spotted wing drosophila (SWD) Drosophila suzukii. However, since RNAi is poorly induced in D. suzukii through the oral intake of unprotected double-stranded RNA (dsRNA), establishing a potent strategy for dsRNA delivery remains essential. In this study, we developed novel virus-like particles (VLPs) derived from the Drosophila X virus (DXV) and investigated their capability to deliver dsRNA in vitro in cultured insect cells and in vivo in live insects. First, the polyproteins of DXV fused at the C-terminus with eGFP or Myc-tag were able to self-assemble into VLPs, in a spherical shape similar to authentic virions. Then, dsRNA molecules were loaded into the DXV-VLPs by a dis-/reassembly strategy and were demonstrated to be partly sheltered from degradation in body fluids from D. suzukii. Furthermore, DXV-VLPs were able to carry the dsRNA efficiently into Drosophila S2 cells and D. suzukii adults. By targeting the essential vha26 gene in D. suzukii adult, DXV-VLP proportion dsvha26 complexes could induce higher mortality (46%) and gene silencing (36%) compared with the DXV-VLP proportion dsGFP, and unprotected dsvha26 (less than 17% mortality and no silencing). Taken together, as a proof-of-concept, this study suggests that insect virus-based VLPs can function as nano-vehicles for dsRNA delivery into insects and provide a tool to improve RNAi for fundamental studies and pest control.