Spraying double-stranded RNA targets UDP-N-acetylglucosamine pyrophosphorylase in the control of Nilaparvata lugens

The rice pest Nilaparvata lugens (the brown planthopper, BPH) has developed different levels of resistance to at least 11 chemical pesticides. RNAi technology has contributed to the development of environmentally friendly RNA biopesticides designed to reduce chemical use. Consequently, more precise targets need to be identified and characterized, and efficient dsRNA delivery methods are necessary for effective field pest control. In this study, a low off-target risk dsNlUAP fragment (166 bp) was designed in silico to minimize the potential adverse effects on non-target organisms. Knockdown of NlUAP via microinjection significantly decreased the content of UDP-Nacetylglucosamine and chitin, causing chitinous structural disorder and abnormal phenotypes in wing and body wall, reduced fertility, and resulted in pest mortality up to 100 %. Furthermore, dsNlUAP was loaded with ROPE@C, a chitosan-modified nanomaterial for spray application, which significantly downregulated the expression of NlUAP, led to 48.9 % pest mortality, and was confirmed to have no adverse effects on Cyrtorhinus lividipennis, an important natural enemy of BPH. These findings will contribute to the development of safer biopesticides for the control of N. lugens.