Transcriptomic Analyses Reveal the Mechanism by Which Different Light Qualities and Light Duration Induce Anthocyanin Biosynthesis in ‘Kyoho’ Grapes

Abstract

The light plays a key role in regulating anthocyanin biosynthesis in plants. However, the molecular basis of anthocyanin synthesis in grape skins irradiated at night with supplemental white light (W), red light (R), blue light (B), and blue light for 3 h, 6 h, 9 h, and 12 h (B3, B6, B9, and B12) is not known. In the present study, the total anthocyanin content in grape skins was significant under different light (DL) and blue-light time (DT) treatments, and the best result was obtained with B9. Analysis of RNA-seq data determined that the key genes in the anthocyanin synthesis pathway, PAL, CHS, DFR, GT, CFIP, VIT_14s0068g00920, VIT_06s0009g02860, and VIT_06s0004g08150, were significantly up-regulated under night-time supplemental light treatments, which led to the significant expression of the phenylpropanoid biosynthesis, phenylalanine metabolism, flavonoid biosynthesis, flavone and flavonol biosynthesis, and the anthocyanin biosynthesis pathway, which were significantly expressed, promoting the accumulation of anthocyanin. The B caused significant expression of PAL (VIT_08s0040g01710), CFIP (VIT_13s0067g03820, VIT_13s0067g02870) and DFR (VIT_18s0001g12800), which may be one of the reasons for the better effect of B compared to W anthocyanin enrichment in grape skins. The DT treatment resulted in significant expression of GT (VIT_11s0052g01600), Peroxidase, VIT_09s0018g01190, and VIT_11s0037g00570. In addition, many TFs such as bHLH, MYB, ERF, WRKY, C2H2, MYB-related, and NAC were found to be involved in the synthesis of anthocyanins under light regulation. These results provide new insights into plants’ nocturnal supplemental-light regulation of anthocyanin accumulation.