Elevated CO 2 leads to thick-skinned thrips by altering trehalose and chitin metabolisms

Elevated CO 2 (eCO 2 ) can affect the environmental adaptability of herbivorous insects by affecting the quality and quantity of host plants’ nutrients under climate change. In this study, the impacts of eCO 2 on carbohydrate metabolism, chitin synthesis and cuticle thickness of western flower thrips ( Frankliniella occidentalis ) fed on kidney bean ( Phaseolus vulgaris ) leaves were studied to elucidate the physiological responses of F. occidentalis to eCO 2 and provide a theoretical basis for the occurrence trend of thrips under future climate change. The results indicated that the trehalose and glycogen contents in F. occidentalis adults significantly increased with corresponding regulation of key genes related to carbohydrate metabolism under eCO 2 compared to ambient CO 2 (aCO 2 ), which was closely related to the increased foliar contents of starch and soluble sugars in P. vulgaris grown under eCO 2 . Subsequently, since trehalose is a precursor of chitin, changes in its content would further affect the chitin synthesis. With the up-regulation of genes related to chitin synthesis and the down-regulation of most genes related to chitin hydrolysis, the chitin content in F. occidentalis adults significantly increased resulting in their increased cuticle thickness and layers, which might enhance their resistance under eCO 2 and become “thick-skinned thrips” under climate change condition.