Abstract
Anthocyanins and proanthocyanidins (PAs) are vital secondary metabolites in Tartary buckwheat because of their antioxidant capacities and radical scavenging functions. It has been demonstrated that R2R3-MYB transcription factors (TFs) are essential regulators of anthocyanin and PA biosynthesis in many plants. However, their regulatory mechanisms in Tartary buckwheat remain to be clarified. Here, we confirmed the role of FtMYB3 in anthocyanin and PA biosynthesis. FtMYB3, which belongs to the subgroup 4 R2R3 family was predominantly expressed in roots. The transcriptional expression of FtMYB3 increased significantly under hormone treatment with SA and MeJA and abiotic stresses including drought, salt, and cold at the seedling stage. Functional analyses showed that FtMYB3 negatively regulated anthocyanin and PA biosynthesis, primarily via downregulating the expression of the DFR, ANS, BAN, and TT13 in transgenic Arabidopsis thaliana, which may depend on the interaction between FtMYB3 and FtbHLH/FtWD40. Altogether, this study reveals that FtMYB3 is a negative regulatory transcription factor for anthocyanin and PA biosynthesis in Tartary buckwheat.
Highlights
Anthocyanins and proanthocyanidins (PAs) are derived from phenylalanine and mainly distributed in the fruit, bark, leaves and seeds of plants [1]
FtMYB3 had a relatively short C-terminal region with two conserved motifs C1 and C2. These results suggest FtMYB3 is an subgroup 4 (SG4) R2R3 MYB protein that may function as a transcriptional regulator in the flavonoid pathway
Only two MYB repressors involved in the anthocyanin and PA biosynthesis were identified in Tartary buckwheat
Summary
Anthocyanins and proanthocyanidins (PAs) are derived from phenylalanine and mainly distributed in the fruit, bark, leaves and seeds of plants [1]. PAs and anthocyanins show different health effects in vitro, such as anticancer and antiinflammatory activities, as well as antioxidation [4,5] Further exploring their synthesis and regulatory mechanisms is essential. An R2R3-MYB TF, VviMYB86 positively regulated PA biosynthesis by upregulating the LAR expression but repressed the anthocyanin biosynthesis with downregulation of the transcript levels of VviANS and VviUFGT [17]. These studies indicate that the molecular mechanism underlying anthocyanin and PA accumulation is complicated. Anthocyanin and PA biosynthesis are influenced by environmental signals such as phytohormone signals, UV radiation, cold, drought and light [22,23] This strongly suggests that MYB TFs play a central role in anthocyanin and PA synthesis
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