Yeast-mediated RNAi of selected lethal genes for mosquito control

RNAi is a post-transcription mechanism for gene regulation in living cells. Upon its ability to down-regulate genes in insect cells, RNAi was suggested as a new tool for pest control. Selection of lethal target gene and suitable delivery method are two key factors for successful RNAi. For this reason, we started a program for selection of lethal genes from Culex quinquefasiatus as targets for RNAi and we tested different delivery methods. In this study, we show the effect of down-regulation of four selected genes (Dynamin, Syntaxin binding protein, JHAMT and HMG-CoA reductase) on the survival and adult emergence of C. quinquefasiatus. Soaking first instar C. quinquefasiatus larvae in target genes dsRNA solution resulted in a larval mortality of 60-90% after 8 days, and adult emergence of less than 35%. DsRNA delivery through chitosan nanoparticles (CNPs) resulted in 65-87% larval mortality and less than 35% adult emergence. We produced genetically modified yeast expressing dsRNA of the four selected genes and assayed its activity against C. quinquefasiatus larvae. Feeding first instar larvae on genetically modified dried inactivated yeast resulted in 66-78% mortality after 8 days, and less than 13% adult emergence. Assaying target gene expression through qRT-PCR showed 30-50% reduction of target gene expression on day 6 post-feeding on genetically modified yeast. In conclusion, we show the high activity of selected target genes against Culex mosquito. Also, genetically modified yeast cells expressing dsRNA gave promising results and have a potential use in future mosquito control programs using RNAi-mediated strategies.