Integrated Metabolomic\nand Transcriptomic Profiling\nReveals the Defense Response of Tea Plants (Camellia\nsinensis) to Toxoptera aurantii

The tea plant (Camellia sinensis) is a unique beverage crop worldwide, but its yield and quality\nare adversely affected by Toxoptera aurantii. However, the response mechanisms of tea plants to T. aurantii stress remain poorly known. Herein, we\npresent the life table of T. aurantii on resistant (W016) and susceptible (HJY) tea cultivars, demonstrating\nthat the fitness of T. aurantii on\nW016 was lower than that on HJY. Integrated metabolic and transcriptomic\nanalyses revealed that T. aurantii feeding\nactivated pathways associated with phenylpropanoid biosynthesis, plant\nhormone signal transduction, and ATP-binding cassette (ABC) transporters.\nNotably, T. aurantii feeding significantly\nupregulated the levels of brassinolide and <i>p</i>-coumaryl\nalcohol in W016 but not in HJY. Furthermore, <i>in vitro</i> enzymatic assays indicated that C. sinensis cinnamyl alcohol dehydrogenase (CsCAD1) catalyzes the formation\nof <i>p</i>-coumaryl alcohol participation in lignin synthesis.\nOur findings highlight the role of brassinolide-mediated lignin biosynthesis\nof the tea plant in response to T. aurantii feeding.