Wampee (Clausena lansium) is a tropical and southern subtropical fruit tree whose productivity is limited by low-temperature stress (LTS). This study investigated the physiochemical and molecular mechanisms by which melatonin (MLT) enhances chilling tolerance in wampee. MLT treatment improved membrane stability and reduced oxidative damage by enhancing antioxidant capacity and osmotic adjustment. Metabolomic and transcriptomic analyses revealed that differentially expressed genes and metabolites were primarily associated with flavonoid biosynthesis and starch and sucrose metabolism pathways. Eleven key candidate genes were identified, including sucrose synthase, granule-bound starch synthase, trehalose-6-phosphate synthase, chalcone-flavonone isomerase, flavonoid 3',5'-hydroxylase, and UDP-glycosyltransferase. MLT treatment also increased soluble carbohydrate levels, such as sucrose and fructose, and enhanced sucrose phosphate synthase activity. Transcription factors ClbHLH2 and ClNAC1 enhanced wampee's cold tolerance by activating the sucrose-biosynthetic genes ClSUS2 and ClSPS1, respectively. These findings provide insights into the molecular and physiological mechanisms underlying wampee adaptation to LTS and highlight MLT as a potential tool to improve wampee's cold tolerance.
Peng et al. (Fri,) studied this question.