A stress-responsive R2R3-MYB transcription factor, EpMYB1 is involved in the regulation of anthocyanin biosynthesis in purple coneflower

Purple coneflower (Echinacea purpurea (L.) Menoch), a North American native and world-popular medicinal and horticultural plant, has been named after its beautiful purple petals due to the accumulation of anthocyanins. However, so far the biosynthesis of anthocyanin and its regulation in purple coneflower remain elusive. In this study, the total anthocyanin contents of eight different purple coneflower tissues were measured, and anthocyanin biosynthetic genes were identified from the multi-tissue transcriptome. Using co-expression, phylogenetic screening, and transient functional verification, EpMYB1 was identified as a potential anthocyanin biosynthesis regulator. EpMYB1 is an R2R3-MYB TF and co-expressed with anthocyanin biosynthetic genes. When EpMYB1 was over-expressed in purple coneflower calli, it positively promoted anthocyanin biosynthesis by upregulating the anthocyanin-specific biosynthetic genes. Dual-luciferase reporter assay indicated that EpMYB1 could significantly activate anthocyanin biosynthetic gene expression by directly binding to the promoters. Moreover, EpMYB1 is a stress-responsive TF involved in the ultraviolet-induced anthocyanin biosynthesis in purple coneflower. The present study identifies an MYB TF that participated in anthocyanin biosynthesis and bridged the gap between environmental stress and anthocyanin biosynthesis in purple coneflower. It provides valuable insights into the anthocyanin biosynthesis in purple coneflower and will significantly improve the development of purple coneflower as an ornament plant.