Spray method application of transdermal dsRNA delivery system for efficient gene silencing and pest control on soybean aphid Aphis glycines

RNA interference (RNAi) has been recognized as a novel and safe strategy in pest management due to its high sequence-dependent specificity. However, the existing dsRNA delivery methods largely restrict the application of the RNAi-based pest management strategy; thus, we previously constructed a nanocarrier-based transdermal dsRNA delivery system on the soybean aphid Aphis glycines with the help of nanocarrier and detergent. In the current study, we improved our transdermal dsRNA delivery system with a smaller and cheaper nanocarrier to investigate the efficacy of spraying aphid-infested soybean seedlings to apply our RNA pesticide. A dsRNA/nanocarrier/detergent formulation was performed, and the dsRNA could penetrate the aphid body wall within 4 h with the help of nanocarrier through the topical application. Four potential RNAi target genes (TREH, ATPD, ATPE and CHS1) were selected and cloned, and their dsRNA fragments were synthesized and tested through the transdermal dsRNA delivery system. The delivered dsRNA efficiently silenced the target gene expression with the knockdown effects ranging from 86.86 to 58.87% and resulted in a high mortality up to 81.67% (dsATPD + dsATPE) through the topical application, when through the spray method, with the highest percent mortality of 78.50% (dsATPD + dsCHS1). Our novel transdermal dsRNA delivery system not only provides a powerful tool for gene functional analysis in laboratory, but also shows a great potential for the pest management in the field, which will promote the practice and development of RNAi-based pest management.