Transcriptomic Analysis of Anthocyanin Degradation in Salix alba Bark: Insights into Seasonal Adaptation and Forestry Applications

Anthocyanins, key flavonoid-derived secondary metabolites, not only confer diverse pigmentation but also function in photoprotection, antioxidative defense, and cold acclimation. In woody species, bark anthocyanin turnover is tightly linked to environmental adaptation, stress resilience, and ornamental traits, yet its molecular regulation remains largely unresolved. Here, we investigated Salix alba L. bark by integrating anthocyanin quantification, transcriptome profiling, and weighted gene co-expression network analysis (WGCNA) to dissect the temporal dynamics and regulatory architecture of anthocyanin degradation. Anthocyanin content peaked at D2 (late December 2024), declined through D3 (mid-January 2025) and D4 (mid-February 2025), and partially rebounded at D5 (early March 2025), coinciding with peak expression of structural genes LAC1/2, POD1/2, and BGLU10. These enzymes co-expressed with multiple transcription factors, including MYB, bHLH, and WRKY families, forming putative core modules. Functional enrichment indicated that differentially expressed genes were enriched in redox processes, glycoside hydrolysis, flavonoid metabolism, and hormone signaling, suggesting a degradation mechanism mediated by reactive oxygen species, glycosidic cleavage, and hormone–transcription factor interplay. This study provides the first comprehensive framework of bark anthocyanin degradation in white willow, advancing the understanding of pigment dynamics, gene–environment crosstalk, and breeding strategies for ornamental woody plants.