FtMYB18 acts as a negative regulator of anthocyanin/proanthocyanidin biosynthesis in Tartary buckwheat
FtMYB18 acts as a negative regulator of anthocyanin/proanthocyanidin biosynthesis in Tartary buckwheat
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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
DOI：
10.1007/s11103-020-01044-5
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发表时间：
2020-08-24
影响因子：
5.1
通讯作者：
Wu, Qi
中科院分区：
文献类型：
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作者：
Dong, Qixin;Zhao, Haixia;Wu, Qi
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，而 C5 基序在此过程中发挥着重要作用。花青素和原花青素（PA）是苦荞（Fagopyrum tataricumGaertn.）中重要的黄酮类化合物，可提供各种鲜艳的颜色并增强非生物胁迫抵抗力。它们的合成通常受MYB转录因子在转录水平的调节。然而，人们对 MYB 的负调控及其对黄酮醇代谢的影响知之甚少。从苦荞中鉴定出包含 C5 基序的 SG4 样 MYB 亚家族 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有强烈的响应。就FtMYB18过表达转基因株系而言，通过下调烟草中NtCHS和NtDFR、拟南芥中AtDFR和AtTT12、苦荞毛状根中FtCHS、FtDFR和FtANS的表达水平，分别降低花青素和PAs的积累。而FtMYB18对FLS基因表达和黄酮醇合成分支中的代谢物含量没有影响。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C5基序缺失的FtMYB18突变系（FtMYB18-C）中，花青素和PAs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FtMYB18 Delta C5与FtJAZ3/-4之间的分子相互作用缺陷。结果表明，FtMYB18可以通过C5基序与苦荞中其他蛋白质的特异性相互作用，在转录水平上抑制花青素和PAs的合成。
Key message FtMYB18 plays a role in the repression of anthocyanins and proanthocyanidins accumulation by strongly down-regulating theCHSandDFRgenes in Tartary buckwheat, and the C5 motif plays an important role in this process. Anthocyanins and proanthocyanidins (PAs) are important flavonoids in Tartary buckwheat (Fagopyrum tataricumGaertn.), 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 ofFtMYB18was 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 withFtMYB18overexpression, anthocyanins and PAs accumulations were decreased through down-regulating expression levels ofNtCHSandNtDFRin tobacco,AtDFRandAtTT12in Arabidopsis,FtCHS,FtDFRandFtANSin Tartary buckwheat hairy roots, respectively. However,FtMYB18showed no effect on theFLSgene 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 FtMYB18 Delta C5 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.