A nanocarrier-mediated dsRNA oral delivery enhances RNAi efficiency in thrips

Thrips pests are causing increasing damage to many crops, including vegetables, fruits, and ornamental plants. RNA interference (RNAi) has been recognized as a potential approach for thrips control. However, the RNAi of thrips is often restricted by the lack of efficient dsRNA delivery method. Here, we developed a nanocarrier-mediated dsRNA oral delivery system for efficient RNAi in the melon thrips, Thrips palmi. We first determined RPL17 and EF1 alpha as the optimal reference genes among different developmental stages, tissues, adult ages, and starvation treatments. Two aminopeptidase N genes, TpAPN2 and TpAPN3, expressed at a relatively high level in the midgut, were selected as target genes for RNAi. In our delivery system, dsRNA solutions were absorbed by cucumber leaves and delivered to thrips by feeding. Naked dsRNAs exhibited no RNAi effect, whereas the nanocarrier SPc (star polycation)-loaded dsRNAs induced a 43.7% and 48.9% decrease in the expression levels of TpAPN2 and TpAPN3, respectively. Inhibited functions of TpAPN2 and TpAPN3 resulted in 36.0% and 53.9% reduction in the feeding amount and 28.5% and 35.5% decrease in egg production, respectively. Co -silencing of TpAPN2 and TpAPN3 led to a mortality of 48.3%, higher than the single-RNAi of TpAPN2 (23.3%) and TpAPN3 (30%). The newly developed dsRNA delivery system is easy to manipulate with improved RNAi efficacy, providing a powerful tool for gene functional study of thrips.