Genome-Wide Identification of R2R3-MYB Gene Family in Fagopyrum dibotrys and Functional Characterization of FdMYB7 and FdMYB23.

Fagopyrum dibotrys, an important medicinal and edible plant, is abundant in flavonoids, proanthocyanidins (PAs), and other bioactive substances showing a variety of pharmacological effects. The MYB transcription factors are involved in the biosynthesis regulation of various secondary metabolites. However, the knowledge of their biological functions in F. dibotrys is still very limited. In this study, a total of 112 FdR2R3-MYBs were identified, and the evolutionary relationships, chromosomal locations, conserved motifs, and protein structures were systematically analyzed. Tandem and segmental duplication facilitated the expansion of FdR2R3-MYB genes, in which segmental duplication played a major role. According to phylogenetic analysis and expression analysis, FdMYB7 and FdMYB23 were selected for further functional research. Transient expression analysis of tobacco leaf mesophyll cells showed that FdMYB7 and FdMYB23 proteins were located to the nucleus. The contents of total flavonoids and PA in Arabidopsis thaliana overexpressing FdMYB7 and FdMYB23 genes increased significantly. Moreover, several key genes involved in flavonoid and PA biosynthesis were significantly up-regulated. These findings contribute to understanding the biological activities of the FdR2R3-MYBs in the synthesis of flavonoids and PAs in F. dibotrys.