Analysis and Verification of the Conserved MYB Binding Element in the DFR Promoter in Compositae

Anthocyanins, ubiquitous in the Compositae family, are regulated by MYB (v-myb avian myeloblastosis viral oncogene homolog), playing an important role in anthocyanin synthesis. In this study, we analyzed the regulation pathway in which the MYB protein of subgroup 6 promotes dihydroflavonol reductase (DFR) expression in Compositae, and validated this law in Saussurea medusa through yeast one-hybrid experiments. Our results showed that MYB and DFR underwent purification selection, DFR promoter analysis revealed the presence of MYB binding site (GAGTTGAATGG) and bHLH binding site (CANNTG) at the sense strand of 84–116 nucleotide residues from the start codon. These two motifs were separated by 9–10 nucleotide residues, as existed in the DFR promoters of many Compositae plants. Furthermore, the yeast one-hybrid experiment demonstrated that SmMYB1 can activate the promoter of SmDFR. Our results provide a reference for further functional study of DFR in Compositae.