Exploration In Novel Strategies To Control Helicoverpa Armigera Using Sterol-absorbing Gene NPC1b As The Target

Helicoverpa armigera is an important agricultural pest,feeding on lots of economic crops.This pest has developed strong resistance to many pesticides.Therefore,it is urgent to develop new methods to control them effectively.Sterols,mostly cholesterol,are essential nutrient but insects cannot synthesize them.Therefore,the absorption and transport of dietary sterols is critical for the growth of insects.In this study,a preliminary exploration in novel strategies to control H.armigera using sterol-absorbing gene NPC1b as the target was conducted.The study includes three major contents.1)The function of NPC1b in sterol absorption in H.armigera.CRISPR/Cas9 editing technology can be used in studying the function of the genes participating in sterol transport and NPC1b is important for the absorption of dietary sterols.Insects died in short of cholesterol when NPC1b cannot function.NPC1b expression is regulated by the concentration of cholesterol in the diet and the low dietary sterol concentration can upregulate NPC1b expression presumably to promote sterol absorption.2)RNAi technology cannot be used to control H.armigera with NPC1b as the target.Many studies have shown that RNAi can be directly used in controlling pests.However,we tried different methods of delivering ds RNA to the insects such as feeding assay and injection assay.Neither of the results showed that ds RNA can significantly inhibit the expression of NPC1b.Nanoparticle-vectored ds RNA did not help either.3)Developing NPC1b inhibitors is potentially a good way to control H.armigera.We collected several field populations of H.armigera and sequenced NPC1b in these insects.We found that NPC1b was highly conserved between field populations and no substitution was identified among the predicted sterol binding sites.This indicates that the insects have no resistance to NPC1b inhibitors.Overall,our studies suggest that NPC1b can be good target to control H.armigera and the inhibitors targeting NPC1b are promising.