Indexed on: 03 Mar '19Published on: 03 Mar '19Published in: International journal of molecular sciences
Flower color is a charming phenotype with very important ornamental and commercial values. Anthocyanins play a critical role in determining flower color pattern formation, and their biosynthesis is typically regulated by R2R3-MYB transcription factors (TFs). is a famous ornamental plant with colorful flowers. However, little is known about the R2R3-MYB TFs that regulate anthocyanin accumulation in . In the present study, two R2R3-MYB TFs, namely, and , were isolated from the petals of 'Shima Nishiki' and functionally characterized. Sequence analysis suggested that contained a bHLH-interaction motif, whereas contained two flavonol-specific motifs (SG7 and SG7-2). Subsequently, the in vivo function of and was investigated by their heterologous expression in and apple calli. In transgenic plants, overexpression of and of caused a significantly higher accumulation of anthocyanins, resulting in purple-red leaves. Transgenic apple calli overexpressing and also significantly enhanced the anthocyanins content and resulted in a change in the callus color to red. Meanwhile, gene expression analysis in and apple calli suggested that the expression levels of the flavonol synthase () and anthocyanidin reductase () genes were significantly downregulated and the dihydroflavonol 4-reductase () and anthocyanin synthase () genes were significantly upregulated in transgenic lines of . Moreover, the expression level of the gene () was significantly downregulated and the (/) and (/) genes were all significantly upregulated in transgenic lines plants of . These results indicate that and both enhance anthocyanin accumulation by specifically regulating the expression of some anthocyanin biosynthesis-related genes in different plant species. Together, these results provide a valuable resource with which to further study the regulatory mechanism of anthocyanin biosynthesis in and for the breeding of tree peony cultivars with novel and charming flower colors.