DhMYB2 and DhbHLH1 regulates anthocyanin accumulation activation of late biosynthesis genes in -type .

-type is a popular orchid with good ornamental and market value. Despite their popularity, molecular regulation of anthocyanin biosynthesis during flower development remains poorly understood. In this study, we systematically investigated the regulatory roles of the transcription factors DhMYB2 and DhbHLH1 in anthocyanins biosynthesis. Gene expression analyses indicated that both and are specifically expressed in flowers and have similar expression patterns, showing high expression in purple floral tissues with anthocyanin accumulation. Transcriptomic analyses showed 29 differentially expressed genes corresponding to eight enzymes in anthocyanin biosynthesis pathway have similar expression patterns to and , with higher expression in the purple lips than the yellow petals and sepals of 'Suriya Gold'. Further gene expression analyses and Pearson correlation matrix analyses of hybrid progenies revealed expression profiles of and were positively correlated with the structural genes , , , , and . Yeast one-hybrid and dual-luciferase reporter assays revealed and can bind to promoter regions of , , , and , suggesting a role as transcriptional activators. These results provide new evidence of the molecular mechanisms of DhMYB2 and DhbHLH1 in anthocyanin biosynthesis in -type .