Comparative transcriptomic analysis reveals the role of signal transduction and cell wall stabilization in cold tolerance of ‘Chamnok’ and ‘Keumsull’ tea plants

Tea plants (Camellia sinensis), cultivated in temperate regions, are vulnerable to cold stress, which can cause significant damage during winter. This study investigates the cold stress responses of two tea cultivars, ‘Chamnok’ and ‘Keumsull’, specifically bred for cultivation in these regions. Following exposure to -5 °C for 12 h, physiological responses were assessed through changes in leaf color, electrolyte leakage, and chlorophyll fluorescence. To elucidate the molecular responses, RNA-seq analysis was conducted to identify differentially expressed genes (DEGs). These DEGs were further explored using clustering analysis and KEGG annotation. ‘Keumsull’ exhibited lower stress-condition at leaf color and chlorophyll fluorescence than ‘Chamnok’. Less electrolyte leakage of ‘Keumsull’ are lower indicating cell structures would more stabilized. In transcriptome analysis, DEGs in the third cluster, associated with crucial pathways such as “MAPK signaling pathway – plant”, “plant hormone signal transduction”, and “alpha-linolenic acid metabolism”, were upregulated in ‘Keumsull’ and downregulated in ‘Chamnok’. Weighted gene co-expression network analysis corroborated the association of these DEGs with cell wall stabilization and signal transduction. These findings provide valuable insights into the cold-stress response mechanisms in tea cultivars developed for temperate regions, laying a theoretical groundwork for the future development of more cold-tolerant tea cultivars.