Natural variation of <i>CsUGT71A60</i> determines growth and cold tolerance via regulating cytokinin glycosylation in <i>Camellia sinensis</i>

Cold stress severely limits tea plant (Camellia sinensis) productivity, yet the molecular mechanisms underlying cold adaptation remain elusive. Here, we identified a cold-inducible glycosyltransferase, CsUGT71A60, through integrative genome-wide association studies (GWAS) and proteomic profiling. Natural variation in CsUGT71A60 was strongly associated with cold tolerance, as evidenced by linkage disequilibrium analysis of flanking SNPs. Functional characterization revealed that CsUGT71A60 specifically catalyses the glycosylation of cis-zeatin to form cis-zeatin 9-O-glucoside in vitro and in vivo. Overexpression of CsUGT71A60 in Arabidopsis enhanced cold tolerance and agronomic traits, including germination rate, tiller number and seed weight, while delaying flowering. Transient silencing of CsUGT71A60 in tea plants disrupted cis-zeatin homoeostasis, impairing antioxidant defences and osmotic regulation under cold stress. Mechanistically, the transcription factor ARR (TEA021099) directly binds to CRM elements in the CsUGT71A60 promoter, activating its expression to fine-tune cytokinin signalling. This study unveils a dual-function glycosyltransferase that orchestrates stress tolerance and developmental plasticity, offering a strategic target for breeding climate-tolerance crops without yield penalties.