Key message

FtMYB18 plays a role in the repression of anthocyanins and proanthocyanidins accumulation by strongly down-regulating the CHS and DFR genes in Tartary buckwheat, and the C5 motif plays an important role in this process.

Abstract

Anthocyanins and proanthocyanidins (PAs) are important flavonoids in Tartary buckwheat (Fagopyrum tataricum Gaertn.), which provides various vibrant color and stronge abiotic stress resistance. Their synthesis is generally regulated by MYB transcription factors at transcription level. However, the negative regulations of MYB and their effects on flavonol metabolism are poorly understood. A SG4-like MYB subfamily TF, FtMYB18, containing C5 motif was identified from Tartary buckwheat. The expression of FtMYB18 was not only showed a negative correlation with anthocyanins and PAs content but also strongly respond to MeJA and ABA. As far as the transgenic lines with FtMYB18 overexpression, anthocyanins and PAs accumulations were decreased through down-regulating expression levels of NtCHS and NtDFR in tobacco, AtDFR and AtTT12 in Arabidopsis, FtCHS, FtDFR and FtANS in Tartary buckwheat hairy roots, respectively. However, FtMYB18 showed no effect on the FLS gene expression and the metabolites content in flavonol synthesis branch. The further molecular interaction analysis indicated FtMYB18 could mediate the inhibition of anthocyanins and PAs synthesis by forming MBW transcriptional complex with FtTT8 and FtTTG1, or MYB-JAZ complex with FtJAZ1/-3/-4/-7. Importantly, in FtMYB18 mutant lines with C5 motif deletion (FtMYB18-C), both of anthocyanins and PAs accumulations had recovered to the similar level as that in wild type, which was attributed to the weakened MBW complex activity or the deficient molecular interaction between FtMYB18ΔC5 with FtJAZ3/-4. The results showed that FtMYB18 could suppress anthocyanins and PAs synthesis at transcription level through the specific interaction of C5 motif with other proteins in Tartary buckwheat.

中文翻译：

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FtMYB18 作为苦荞中花青素/原花青素生物合成的负调节剂。

关键信息

FtMYB18通过强烈下调苦荞中的CHS和DFR基因在抑制花青素和原花青素积累中发挥作用，C5基序在此过程中起重要作用。

抽象的

花青素和原花青素(PAs)是苦荞( Fagopyrum tataricum Gaertn . )中重要的黄酮类化合物，能提供多种鲜艳的颜色，增强抗非生物胁迫的能力。它们的合成通常在转录水平受 MYB 转录因子的调节。然而，人们对 MYB 的负面调节及其对黄酮醇代谢的影响知之甚少。从苦荞中鉴定出含有 C5 基序的 SG4 样 MYB 亚科 TF，FtMYB18。FtMYB18的表达不仅与花青素和PAs含量呈负相关，而且对MeJA和ABA有强烈反应。至于带有FtMYB18的转基因系通过分别下调烟草中NtCHS和NtDFR、拟南芥中AtDFR和AtTT12、苦荞毛根中FtCHS、FtDFR和FtANS的表达水平，过表达，花青素和 PAs 积累减少。然而，FtMYB18对FLS没有影响黄酮醇合成分支的基因表达和代谢物含量。进一步的分子相互作用分析表明，FtMYB18可以通过与FtTT8和FtTTG1形成MBW转录复合物，或与FtJAZ1/-3/-4/-7形成MYB-JAZ复合物来介导花青素和PAs合成的抑制。重要的是，在具有 C5 基序缺失的 FtMYB18 突变株系（FtMYB18-C）中，花青素和 PAs 的积累都恢复到与野生型相似的水平，这归因于 MBW 复合物活性减弱或 FtMYB18ΔC5 之间的分子相互作用不足。与 FtJAZ3/-4。结果表明，FtMYB18可通过C5基序与苦荞中其他蛋白质的特异性相互作用，在转录水平抑制花青素和PAs的合成。