Wan Shuzhen, Li Chaofeng, Ma Xiaodong, Luo Keming
Key Laboratory of Adaptation and Evolution of Plateau Biota, Northwest Institute of Plateau Biology, Chinese Academy of Sciences, Xining, 810008, China.
University of the Chinese Academy of Sciences, 19 A Yuquan Rd, Shijingshan District, Beijing, 100049, China.
Plant Cell Rep. 2017 Aug;36(8):1263-1276. doi: 10.1007/s00299-017-2151-y. Epub 2017 May 18.
A novel R2R3 MYB transcription factor PtrMYB57 interacted with bHLH131 and PtrTTG1 to form the MBW complex and negatively regulated the biosynthesis of both anthocyanins and PAs in poplar. R2R3-MYB transcription factors (TFs) are important regulators of secondary metabolite biosynthesis in woody species. A series of R2R3-MYB TFs involved in anthocyanin and proanthocyanidin (PA) biosynthesis have been identified in poplar. In this study, we report the identification and characterization of a subgroup 4 MYB member PtrMYB57, which contains a repressor domain (LxLxL) at the C-terminal end. PtrMYB57 encodes an R2R3 MYB protein localized in the nucleus and is predominantly expressed in mature leaves. Transgenic poplar overexpressing PtrMYB57 showed a reduction in anthocyanin and PA accumulation compared to wild-type plants. By contrast, a high anthocyanin and PA phenotype was observed in Ptrmyb57 mutants generated by the CRISPR/Cas9 system. Furthermore, transient expression assays revealed that PtrMYB57 interacted with bHLH131 (bHLH) and PtrTTG1 (WDR) to form the MBW complex and bound to the flavonoid gene promoters, leading to inhibition of these promoters. Taken together, our results suggest that PtrMYB57 plays a negative role in the regulation of anthocyanin and PA biosynthesis in poplar.
一种新型的R2R3 MYB转录因子PtrMYB57与bHLH131和PtrTTG1相互作用形成MBW复合体，并对杨树中花青素和原花青素的生物合成起负调控作用。R2R3-MYB转录因子是木本植物次生代谢物生物合成的重要调节因子。在杨树中已经鉴定出一系列参与花青素和原花青素（PA）生物合成的R2R3-MYB转录因子。在本研究中，我们报道了一个第4亚组成员MYB成员PtrMYB57的鉴定和特征，其在C末端含有一个阻遏结构域（LxLxL）。PtrMYB57编码一种定位于细胞核的R2R3 MYB蛋白，主要在成熟叶片中表达。与野生型植物相比，过表达PtrMYB57的转基因杨树中花青素和PA的积累减少。相比之下，在通过CRISPR/Cas9系统产生的Ptrmyb57突变体中观察到高花青素和PA表型。此外，瞬时表达分析表明，PtrMYB57与bHLH131（bHLH）和PtrTTG1（WDR）相互作用形成MBW复合体，并与类黄酮基因启动子结合，导致这些启动子受到抑制。综上所述，我们的结果表明PtrMYB57在杨树花青素和PA生物合成的调控中起负作用。
