Comprehensive metabolomics and transcriptomics analysis reveal the regulatory mechanism of StHY5 on anthocyanin accumulation in potato tubers.

Light is a key factor for inducing anthocyanin biosynthesis; however, its regulatory mode in potato anthocyanin biosynthesis remains unclear. Previous research identified a specific genotype that causes the tuber skin to gradually turn purple when exposed to light of different wavelengths. In the present study, we conducted metabolome and transcriptome analyses on tuber samples during anthocyanin accumulation. The metabolome data showed that the contents of naringenin chalcone, naringenin, dihydrokaempferol, and cyanidin gradually increased during anthocyanin accumulation. The transcriptome data showed that the expression levels of most structural genes increased gradually during anthocyanin accumulation, especially the StF3'H gene that promotes cyanidin formation. Moreover, the photo-responsive transcription factor StHY5 was specifically expressed at high levels before anthocyanin accumulation, occurring 2 h after light induction. Establishment of transgenic lines demonstrated that StHY5 overexpression could promote the accumulation of anthocyanin in potato tubers, along with a parallel increase in the transcription levels of StAN2, StMYBA1, StCHI, StF3H, StF3'H, and StDFR. Electrophoretic mobility shift and dual luciferase assays showed that StHY5 can enhance the promoter activity of the MYB transcription factors StAN2 and StMYBA1 as well as the structural genes StCHI and StF3H through binding to the G-box motif. StAN2 activated the expression of StF3'H (a newly identified purple gene locus in potato) and StDFR by binding to the MYB-binding site in the promoters, thereby promoting anthocyanin biosynthesis. This study provides a theoretical basis for revealing the molecular mechanism of light-regulated anthocyanin biosynthesis in potatoes.