Elevated CO₂ aggravates invasive thrip damage by altering its host plant nutrient and secondary metabolism

As atmospheric CO₂ concentration continues to increase, plants using CO₂ as raw materials for photosynthesis will inevitably be affected, which in turn affects the life history and behavior of herbivorous insects. Our previous research has shown increased food intake and aggravated damage of western flower thrips, Frankliniella occidentalis to kidney bean (Phaseolus vulgaris) caused by elevated CO₂ (eCO₂), however the molecular mechanism of this phenomenon is unclear. In this study, the comparative transcriptome analysis combined with corresponding phenotypic changes were studied to reveal the molecular mechanism of interaction between F. occidentalis and P. vulgaris under eCO₂. Inferred from the results, eCO₂ had different degrees of inhibition to the defense responses caused by thrips infestation in P. vulgaris leaf sap based on nutrients, plant hormones and secondary metabolites, making P. vulgaris leaves less resistant to thrips under eCO₂ compared to ambient CO₂ (aCO₂). Besides, the contents of glucose, trehalose, triglycerides and free fatty acids in F. occidentalis adults increased significantly after feeding on the P. vulgaris leaf sap with significantly increased soluble sugars content under eCO₂, which might lead to glucolipid metabolic disorders and increased food intake of F. occidentalis adults. The results indicated that decreased plant defense of P. vulgaris and increased food intake of F. occidentalis adults were combined to aggravate the thrips damage under eCO₂, providing a theoretical basis for future occurrence trend of thrips under eCO₂.