Structural and Functional Organization and Evolution of the WD40 Genes Involved in the Regulation of Flavonoid Biosynthesis in the Triticeae Tribe

Abstract

Flavonoid biosynthesis in plants is regulated by a specific MBW protein complex, which is formed by the interaction of the R2R3-Myb, bHLH, and WD40 transcription factors. The genomes of the representatives of the Triticeae tribe are characterized by the presence of orthologous and homeologous copies of the flavonoid biosynthesis regulatory genes. The structural and functional organization of the R2R3-Myb and bHLH gene families is already well studied, while the genes encoding the third component of the MBW complex in the representatives of Triticeae, the WD40 factor, remain scarcely studied. In the present study, the search and analysis of the WD40 genes in the representatives of Hordeum, Triticum, and Aegilops genera was carried out. Two paralogical groups of genes (WD40-1 and WD40-2), located on the long and short arms of the group 6 chromosomes, were identified. It was demonstrated that conservatism of the identified WD40 sequences was supported by natural selection. High levels of WD40-1 and WD40-2 expression were observed in different organs and tissues of wheat and barley, regardless of their pigmentation. It is suggested that these genes could participate in the biosynthesis of not only flavonoid pigments of anthocyanins but also colorless compounds.