Lysine positively regulates cold tolerance in tea plants through the induction of CsCDF1 transcription factor

Cold stress is a major abiotic factor that severely impairs the yield and quality of spring tea. Therefore, investigating potential cold protectants becomes a necessary strategy to support the sustainable development of the tea industry. Lysine is an essential amino acid that has recently been recognized as a key modulator of plant stress adaptation. Here, we identified a significant accumulation of lysine under cold stress by integrating multi-metabolomic analysis and UPLC detection. Exogenous lysine application strongly enhances the cold tolerance of tea plants by improving their antioxidant capacity and alleviating cold-induced membrane peroxidation and photosynthetic damage. Transcriptome analysis further demonstrated that lysine comprehensively activated cold-adaptive programs, including oxidative defense and hormone signaling pathways, along with core cold-responsive transcriptional networks. The circadian rhythm-related transcription factor CsCDF1 was strongly induced by low temperature and exogenous lysine, and its induction level was positively correlated with lysine concentration. Combined transient silencing and overexpression experiments indicated that CsCDF1 functions as a positive regulator of cold tolerance in tea plants. These findings support a potential working model whereby lysine integrates antioxidant defense, hormone signaling, and CsCDF1 -associated transcriptional reprogramming to reinforce cold tolerance in tea plants.