The DoMYB102–DoUGT71K2 Regulatory Module Mediates Heat-Induced Flavonoid Glycosylation in Dendrobium officinale

Dendrobium officinale, a perennial medicinal herb rich in flavonoids, exhibits multiple pharmacological properties including antioxidant and hypoglycemic effects. However, its medicinal quality is compromised by various abiotic stresses, such as heat, cold, and osmotic stresses. UDP-glycosyltransferases play critical roles in both flavonoid glycosylation and plant stress tolerance. Here, we report the identification of a heat-responsive glycosyltransferase gene, DoUGT71K2, from D. officinale transcriptomes, and a characterization of its stress-induced expression and transcriptional regulatory mechanisms. Quantitative real-time PCR (qRT-PCR) showed that DoUGT71K2 exhibits tissue-specific high expression in flowers, and its transcript abundance is strongly elevated in response to heat, cold, and abscisic acid (ABA) treatment. The direct promoter-binding and trans-activating function of DoMYB102 on DoUGT71K2 was confirmed via dual-luciferase reporter and yeast one-hybrid (Y1H) assays. These results establish a DoMYB102–DoUGT71K2 regulatory module that couples heat stress response with flavonoid biosynthesis, which provides a molecular basis for improving stress tolerance and medicinal quality in D. officinale through molecular breeding.