Nanocarrier-mediated transdermal dsRNA-NPF1 delivery system contributes to pest control via inhibiting feeding behavior in Grapholita molesta

Grapholita molesta, a worldwide fruit-boring pest, is difficult to be effectively controlled due to the larvae feeding habit inside fruits. Neuropeptide F (NPF) is the crucial molecule modulating feeding behavior of insects. Herein, two genes, NPF1 and NPF2, were identified and cloned from G. molesta. GmolNPF1 had a higher expression in newly hatched larvae than in other developmental stages and mainly in the midgut (major expressive organ). Coincidentally, the stage of newly hatched larvae was the best control period to prevent larvae from entering the fruits. Further study demonstrated that only GmolNPF1 expression increased significantly after starvation and declined after refeeding. After GmolNPF1 knockdown by RNA interference (RNAi), the feeding amount, weight, body size and drill holes rate of larvae decreased significantly, and the number of larvae that ate food within 5 min declined significantly. The pET30-NPF1-BL21(DE3) RNase III system was successful constructed and produced large batch dsRNA (double stranded, ds) of GmolNPF1. The nanocarrier-mediated transdermal dsRNA delivery system enhanced the RNAi efficiency of dsNPF1, significantly decreased the fruit damage and increased the mortality of newly hatched larvae via spraying method. Our research not only revealed the regulation function of GmolNPF1 involved in the feeding behavior of G. molesta, but also showed the NPF1 as a molecular target combined the transdermal dsRNA delivery system will a potential control strategy for pest management in the field.