Validamycin affects the development and chitin metabolism in Spodoptera frugiperda by inhibiting trehalase activity

The fall armyworm (FAW) Spodoptera frugiperda is a major polyphagous pest that feeds mainly on food crops, such as corn and rice, posing a serious threat to the safety of food crops worldwide. Trehalase, can degrade trehalose and the resulting products participate in the synthesis of chitin, one of the main components of outer epidermis in insects. Therefore, trehalase inhibitors have been identified as novel agents for pest control. We report the insecticidal potential of a trehalase inhibitor validamycin against FAW. Validamycin (1 mu g/mu L) when injected in FAW using microinjection could significantly reduce trehalase activity 48 h later, especially, the activity of soluble trehalase, then the glucose content and glycogen content also decrease. In addition, the deaths of larvae in validamycin treated group at each instar stage were higher than those in the control group, moreover, validamycin treatment increased the pupal weight and prolonged pest development. Similarly, validamycin also significantly inhibited the chitinase activity and caused the accumulation of chitin in FAW. Results of qRT-PCR showed that the expression levels of two trehalose genes (SfTRE1 and SfTRE2), which encode key enzymes in chitin biosynthesis pathway, were significantly reduced, while the expression levels of fructose-6-phosphate transaminase, glucosamine-phosphate N-acetyltransferase and chitinase genes were significantly increased. It is obvious that validamycin has an influence on physiological metabolism and development of FAW, the results obtained will be conducive to the prevention and control of FAW in the future.

Automated summary

It has been found that the trehalase inhibitor validamycin can significantly reduce trehalase activity in fall armyworms, leading to a decrease in glucose and glycogen content. Additionally, it affects the physiological metabolism and development of fall armyworms, increasing larval mortality rate and pupal weight.