Comprehensive analysis of safflower R2R3-MYBs reveals the regulation mechanism of CtMYB76 on flavonol biosynthesis

Abstract

The safflower (Carthamus tinctorius) is an important plant used for medicine and food. R2R3-MYB transcription factors play vital roles in regulating plant biological processes. In this study, we identified 102 R2R3-MYBs in the C. tinctorius genome. Phylogenetic analysis indicated 36 combined clades, and one independent Carthamus clade. Flower color, tissue and developmental specific expression patterns of R2R3-MYB genes were observed in C. tinctorius. Almost all R2R3-MYBs contained some cis-acting elements that associated with abiotic and biotic responses. Twelve R2R3-MYB genes contained the LTR, MBS and MeJA elements were selected to test their expressional responses under drought, cold and MeJA conditions. Results show all these treatments induced large scale upregulation in most of these genes, with drought stress inducing the highest changes. Overexpression of CtMYB76 in tobacco significantly induced the upregulation of flavonoid biosynthesis structural genes, accompanied by accumulation of flavonols. Dual-luciferase reporter and yeast one-hybridization analyses confirmed that CtMYB76 can bind with the promoter of structural genes and activate their expression. This study not only provided an in-depth understanding of the molecular basis of R2R3-MYB TFs in safflower but also highlighted their potential applications in agriculture.