CtDREB52 transcription factor regulates UV-B-induced flavonoid biosynthesis by transactivating CtMYB and CtF3′H in Safflower (Carthamus tinctorius L.)

Abstract

The APETALA2/ethylene-responsive element binding protein (AP2/ERF) is a highly conserved transcription factors family, involved in plant growth, development, and response to diverse stress conditions. Until recently, the AP2/ERF family has not been functionally characterized in safflower. In total, 187 AP2/ERF genes were identified from safflower genome. Phylogenetic analysis divided these CtAP2/ERFs into four distinct groups: DREB, ERFs, AP2s, and RAV genes. Furthermore, conserved protein motifs, gene structure, and cis-regulatory elements suggested important evolutionary insights into the potential role of these CtAP2/ERFs. Moreover, a comprehensive gene expression analysis conducted across various flowering stages demonstrated a consistent expression pattern of CtDREB52, which exhibited a significant correlation with alterations in the total flavonoid content. Importantly, CtDREB52 was found to be responsive to UV-B stress, and its overexpression in safflower not only promoted flavonoid accumulation but also induced an early flowering phenotype and up-regulated key genes of flavonoid pathway, while its silencing showed the opposite effect. Further, the interaction between CtDREB52 and CtDFR and CtMYB enzymes was confirmed through yeast two-hybrid and BiFC analysis. These findings provide important insights into CtDREB52-mediated regulation of flavonoid biosynthesis under UV-B stress by interacting with CtDFR and CtMYB in safflower.

Keywords

• Carthamus tinctorius
• AP2/ERF gene family
• CtDREB52
• Flavonoid biosynthesis
• UV-B stress