Integrated physiological, biochemical, and transcriptomic analysis of the cold-sensitive response in Mussaenda anomala.

Mussaenda anomala exhibits high sensitivity to low-temperature stress, but its molecular adaptation mechanisms remain poorly understood. In this study, tissue-cultured seedlings were exposed to temperature gradients (25 °C as control, 12 °C, 4 °C, and 0 °C) to investigate cold-stress responses. Physiological analyses revealed increased oxidative damage (increased levels of H₂O₂, relative electrolyte conductivity (REC) and malondialdehyde (MDA)) and chloroplast/mitochondrial impairment, accompanied by downregulation of photosynthetic genes (Psb/Psa/LHCA/LHCB). The plants activated multi-level defenses, including stomatal closure, palisade tissue thickening, starch accumulation, and upregulation of starch/sucrose metabolism genes (SS/Amy). Antioxidant systems (SOD/POD/CAT) were enhanced, alongside hormonal reprogramming (ABA/JA accumulation with auxin suppression). Weighted gene co-expression network analysis (WGCNA) revealed three co-expression modules containing 12 hub genes (BKI1-like, PAO2-like, CDPK1 etc.) potentially regulating cold adaptation. These findings provide the first comprehensive molecular characterization of M. anomala's cold stress response, offering valuable targets for breeding cold-tolerant ornamental plants.