Enhanced β-glucosidase in Western flower thrips affects its interaction with the redox-based strategies of kidney beans under elevated CO 2 .

β-Glucosidase is validated as an elicitor for early immune responses in plants and it was detected in the salivary glands of Frankliniella occidentalis in previous research. Seven differentially expressed genes encoding β-glucosidase were obtained by comparing the transcriptomes of F. occidentalis adults grown under two different CO 2 concentrations (800 vs. 400 ppm), which might be associated with the differences in the interaction between F. occidentalis adults and its host plant, Phaseolus vulgaris under different CO 2 levels. To verify this speculation, changes in defense responses based on the production and elimination of reactive oxygen species (ROS) in P. vulgaris leaves treated with three levels of β-glucosidase activity under ambient CO 2 (aCO 2 ) and elevated CO 2 (eCO 2 ) were measured in this study. According to the results, significantly higher levels of ROS were noticed under eCO 2 compared to aCO 2 , which was caused by the increased β-glucosidase activity in thrips due to increased cellulose content in P. vulgaris leaves under eCO 2 . Together with the lower activities of superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) in injured leaves under eCO 2 , P. vulgaris leaves would be negatively affected on redox-based defense by eCO 2 , thus facilitating thrips damage under climate change.