Transcriptomic Insights into Anthocyanin Biosynthesis in Aronia melanocarpa Callus Under Different Light Conditions

Aronia melanocarpa is rich in anthocyanins, compounds with significant medicinal and industrial value, making it an attractive species for enhanced production. Compared with fruits or intact plants, callus tissue offers a uniform, controllable in vitro system that is particularly suitable for dissecting regulatory mechanisms under defined environmental conditions. Although light quality is known to influence anthocyanin biosynthesis, its specific regulatory mechanisms in A. melanocarpa remain unclear. In this study, callus tissues were cultured under six light regimes: full-spectrum LED, blue:red (5:1), red:blue (5:1), red:blue:white (1:1:1), red:white (5:1), and pure blue light. Anthocyanin content was quantified using the pH differential method, and the results showed that the blue:red (5:1) treatment produced the highest accumulation, reaching 14.06 mg/100 g. Transcriptome sequencing was then performed to compare the gene expression profiles between calli cultured under blue:red (5:1) light and those maintained in darkness. A total of 10,547 differentially expressed genes (DEGs) were identified, including 6134 upregulated and 4413 downregulated genes. Functional enrichment analysis indicated that these DEGs were mainly involved in anthocyanin biosynthesis and transport. Importantly, key structural genes such as PAL, C4H, 4CL, CHS, ANS, UFGT, and GST were significantly upregulated under blue:red (5:1) light, as further validated by qRT-PCR. Overall, our findings demonstrate that a blue:red (5:1) light ratio enhances anthocyanin accumulation by promoting the expression of biosynthetic and transport-related genes. This study not only provides new transcriptomic insights into the light-mediated regulation of secondary metabolism in A. melanocarpa callus, but also establishes a foundation for optimizing in vitro culture systems for sustainable anthocyanin production.