Transcriptomic analysis reveals the differences in cold tolerance among mei varieties and overexpression of PmWRKY18 enhances cold tolerance in tobacco

Prunus mume (mei) is widely cultivated as an ornamental and fruit tree in temperate regions, but its expansion into colder areas is limited by freezing intolerance. Interspecific hybrids between mei and apricot (apricot‑mei) generally exhibit enhanced cold tolerance, yet the underlying molecular mechanisms remain unclear. In this study, we combined physiological profiling and comparative transcriptomics to explore cold tolerance strategies in the apricot-mei ‘Dan Fenghou’ (DFH), the cold-sensitive mei ‘Beijing Yudie’ (BJYD), and their hybrid offspring ‘Xiang Ruibai’ (XRB). A comprehensive evaluation of these parameters revealed that DFH possesses the highest cold resistance, followed by XRB, while BJYD was the most susceptible. Transcriptome sequencing across multiple stress and recovery stages revealed that DFH and XRB shared robust induction of oxidative phosphorylation and membrane-repair pathways during cold acclimation, whereas BJYD showed a markedly attenuated transcriptional response. Weighted gene co-expression network (WGCNA) identified a module highly correlated with EL, within which PmWRKY18 emerged as a central hub gene. Its expression was markedly upregulated under cold stress and abscisic acid (ABA), suggesting a potential role in the cold response pathway. Heterologous overexpression of PmWRKY18 in tobacco significantly enhanced freezing tolerance, associated with improved membrane integrity, elevated antioxidant capacity, and upregulation of endogenous cold-responsive genes. Our study offers valuable insights into the molecular mechanisms governing cold tolerance in apricot mei, emphasizing the importance of specific genes and regulatory networks in mediating low-temperature stress responses, and identifies PmWRKY18 as a key regulator contributing to the superior cold tolerance in mei. • Cold acclimation boosts antioxidant enzymes & membrane stability. • True mei's insensitivity to cold acclimatization may be the reason for its low cold tolerance. • PmWRKY18 is a key regulator in ABA-dependent cold signaling. • Oxidative phosphorylation provides energy for cold adaptation of P. mume .