Genome-Wide Identification of R2R3-MYB Transcription Factor Family in Tartary Buckwheat (Fagopyrum tataricum) Identifies a Member Involved in Anthocyanin Biosynthesis

Tartary buckwheat (Fagopyrum tataricum Gaertn.) belongs to the family of Polygonaceae and is used as a multi-functional plant. R2R3-MYB transcription factors play a crucial part in plant growth and are involved in many biological processes where they regulate their internal environment. To date, there is no documented systematic research on the R2R3-MYB gene family in Tartary buckwheat. Here, domain features, chromosomal location, motif prediction, gene structure, cis-acting elements, as well as the expression pattern of R2R3-MYB transcription factors were analyzed comprehensively in Tartary buckwheat using a bioinformatic approach. Additionally, one R2R3-MYB gene was verified by transgenic Arabidopsis. Results indicate that a total of 152 R2R3-MYB genes were identified with special R2R3 domains and were distributed on 8 chromosomes of Tartary buckwheat. They were further classified into 25 sub-categories via phylogenetic analysis in terms of the R2R3-MYB gene family classification principles of Arabidopsis thaliana. This classification was further supported by analysis of exon-intron structure, motif, and cis-elements. Tandem and segmental duplication existed among the R2R3-MYB gene family of Tartary buckwheat, and there were 5, 8, 27, and 36 FtR2R3-MYB homologous genes, respectively, when comparing with Zea mays, Oryza sativa, Arabidopsis thaliana, and Solanum melongena by synteny analysis. The expression pattern of FtR2R3-MYB genes in different tissue and under salt stress and different light condition showed that members had tissue-specific expression levels and that these members may play diverse functions in plant growth and adaptation to varying environments. In addition, one of the FtR2R3-MYB gene families, FtMYB43, a homologue of AtTT2, clustered with R2R3-MYB from other plant species, which were reported to be involved in the regulation of anthocyanin or proanthocyanidin biosynthesis. This gene was located in the nucleus, and had transcriptional activation activity, indicating that FtMYB43 may be a positive transcript factor of anthocyanin or proanthocyadin biosynthesis. Moreover, the function of FtMYB43 was further verified to improve the production of anthocyanin in transgenic Arabidopsis by overexpression, and qRT-PCR assay implied that FtMYB43 may regulate the expression levels of most structural genes of the anthocyanin biosynthesis pathway in Arabidopsis seedlings. These results provide more insights into the structure and function of the R2R3-MYB gene family and may accelerate the breeding of ornamental buckwheat cultivars.