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 ppm 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. The results showed that both leaves infested with thrips and those sprayed with the pure β-glucosidase solution showed significant increases in ROS levels under aCO 2 and eCO 2 compared to the control leaves, and the activities of antioxidant enzymes including superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) were increased correspondingly; while in leaves infested with FoβGlu-1-silenced thrips, the ROS levels and activities of these enzymes did not change significantly during the first 12 hours of injury regardless of CO 2 level compared to the leaves infested with GFP-silenced thrips. Besides, 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 SOD, POD and 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. This article is protected by copyright. All rights reserved.