Environmental RNAi-based reverse genetics in the predatory mite Neoseiulus californicus: towards improved methods of biological control

The predatory mite Neoseiulus californicus (McGregor) (Mesostigmata: Phytoseiidae) has been commercialized by manufacturers in the pest control industry and is used worldwide as a natural enemy of spider mites. However, because its genome has not been sequenced, reverse genetics techniques that could be used to analyze gene function have not been established. Here we partially sequenced the gene that encodes the vacuolar-type H+-ATPase (V-ATPase), an ATP-dependent proton pump, in N. californicus (NcVATPase) and then conducted a functional analysis using environmental RNA interference (eRNAi) by orally administering sequence-specific exogenous dsRNA (dsRNA-NcVATPase) to larvae and adult females. The larvae treated with dsRNA-NcVATPase took longer to develop and had lower survivorship, fecundity, and offspring viability at the adult stage than those treated with a control dsRNA. Adult females treated with dsRNA-NcVATPase showed significant reductions in survival, fecundity, and prey consumption, and their endogenous gene expression level of NcVATPase was reduced by approximately 65% compared with the control. Our findings suggest that the NcVATPase gene, silencing of which inhibits feeding and reproduction, is an excellent biomarker for investigating the eRNAi mechanism in N. californicus. The highly efficient experimental system of eRNAi established in this study paves the way for applied research using eRNAi to enhance the predatory ability of N. californicus. Key messageO_LIEnvironmental RNAi-inducing double-stranded RNAs have the potential to improve biological control as well as biopesticide applications. C_LIO_LIWe investigated the efficacy of eRNAi against the predatory mite Neoseiulus californicus, a major natural enemy of spider mites. C_LIO_LIOral administration of dsRNA targeting NcVATPase decreased the gene expression level, developmental time, survival, fecundity, and prey consumption. C_LIO_LINeoseiulus californicus, which was found to have the high eRNAi effects, can be used as a model for the study on eRNAi-mediated improvement of biological control. C_LI