Transcriptomic Analysis Reveals the Regulation Function of Calcium Ions Regarding Anthocyanin Biosynthesis in Lonicera japonica Under Cold Stress

Lonicera japonica is a widely utilized medicinal and ornamental plant. Its secondary metabolism is highly sensitive to cold stress. Previous studies have demonstrated how L. japonica accumulates anthocyanin in response to cold stress, with calcium ions playing a potential role in the regulation. To further clarify the regulatory function of calcium ions regarding pigment formation under cold stress, transcriptomic analysis was conducted on exogenous calcium ions and calcium chelator EGTA-treated L. japonica under cold stress. The CaCl2 treatment markedly delayed changes in the pigmentation, and the plant maintained a higher chlorophyll content, whereas EGTA treatment enhanced anthocyanin accumulation and induced earlier and more intense leaf coloration. A total of 17,296 differentially expressed genes were co-expressed during cold stress, and calcium-responsive genes were predominantly enriched in phenylpropanoid biosynthesis, hormone signaling, and stress response pathways. Notably, key transcription factors such as MYBS3 and BRH1 were identified with expression patterns that closely correlated with pigment changes and stress adaptation. These results indicate the deep involvement of molecular mechanisms of calcium signaling in modulating pigment accumulation in response to cold stress, providing a theoretical foundation for improving both the ornamental and medicinal value of L. japonica under adverse environmental conditions.