Novel Insights into the Control of Sitophilus zeamais in Grain by Chitosan-Nanoparticle-Contained dsSzCOX

Sitophilus zeamais is a highly destructive pest of stored grains worldwide. To develop novel RNA insecticides, the double-stranded RNA of S. zeamais cytochrome c oxidase (dsSzCOXs: dsSzCOXI, dsSzCOXII, and dsSzCOXIII) was successfully expressed in the pET28a-BL21(DE3)-RNaseIII^- system and remarkably downregulated the expression level of SzCOXs in S. zeamais through injection or feeding methods, leading to high mortalities in both larvae and adults. Under their optimal expression conditions (isopropyl β-d-thiogalactoside, 0.6 mM), the yields of dsSzCOXI (at 28 °C for 4 h), dsSzCOXII (at 37 °C for 6 h), and dsSzCOXIII (at 37 °C for 6 h) were 8.49, 5.80, and 6.04 μg/mL respectively. The chitosan-based gene delivery system composed of dsSzCOXs (CS@dsSzCOXs) was established for the insecticidal effect of S. zeamais adults via mixing wheat seeds, with the mortality reaching 50% on day ten. Consequently, this nanoparticle-mediated gene delivery system is expected to be an effective approach for S. zeamais control.