A 5-enolpyruvylshikimate 3-phosphate synthase functions as a transcriptional repressor in Populus

First author: Meng Xie; Affiliations: Oak Ridge National Laboratory (橡树岭国家实验室): Oak Ridge, USA

Corresponding author: Gerald A Tuskan

Long-lived perennial plants, with distinctive habits of inter-annual (年际) growth, defense, and physiology, are of great economic and ecological importance. However, some biological mechanisms resulting from genome duplication and functional divergence of genes in these systems remain poorly studied. Here, we discovered an association between a poplar (Populus trichocarpa) 5-enolpyruvylshikimate 3-phosphate synthase gene (PtrEPSP; 5-烯醇式丙酮酸莽草酸-3-磷酸合酶) and lignin biosynthesis. Functional characterization of PtrEPSP revealed that this isoform possesses a helix-turn-helix motif in the N-terminus and can function as a transcriptional repressor that regulates expression of genes in the phenylpropanoid pathway (苯丙烷途径) in addition to performing its canonical biosynthesis function in the shipmate pathway (莽草酸途径). We demonstrated that this isoform can localize in the nucleus and specifically binds to the promoter and represses the expression of a SLEEPER-like transcriptional regulator, which itself specifically binds to the promoter and represses the expression of PtrMYB021(known as MYB46in Arabidopsis thaliana), a master regulator of the phenylpropanoid pathway and lignin biosynthesis. Analyses of overexpression and RNAi lines targeting PtrEPSP confirmed the predicted changes in PtrMYB021expression patterns. These results demonstrate that PtrEPSP in its regulatory form and PtrhAT form a transcriptional hierarchy regulating phenylpropanoid pathway and lignin biosynthesis in Populus.

多年生的植物具有年际生长、抗性及生理的显著特征，并且具有巨大的经济和生态价重要性。然而，关于全基因组复制事件及随后基因的功能分化在这些植物系统中的生物学机制研究的还比较少。本文，作者鉴定了杨树中的5-烯醇式丙酮酸莽草酸-3-磷酸合酶PtrEPSP与木质素生物合成之间的关系。PtrEPSP蛋白的功能鉴定显示该异构体在N端具有一个螺旋-转角-螺旋的基序，使得其除了能够参与莽草酸途径，还能够起到对苯丙烷途径上某些基因的转录抑制因子的作用。研究显示PtrEPSP基因定位到核中，能够直接结合一个类SLEEPER转录调控因子的启动区，并抑制其的表达，而该转录调控因子能够结合到拟南芥MYB46基因在杨树中的同源基因PtrMYB021的启动区，并抑制PtrMYB021基因的表达，而PtrMYB021基因是苯丙烷途径和木质素生物合成的主要调控子。对于PtrEPSP过表达和RNAi干扰PtrEPSP的株系研究确认了PtrMYB021基因的表达模式。本文的结果揭示了杨树中的PtrEPSP与PtrhAT组成的转录层级调控了苯丙烷途径和木质素的生物合成。

通讯：Gerald A Tuskan(https://www.ornl.gov/staff-profile/gerald-tuskan)

个人简介：1978年，北亚利桑那大学，学士，专业：林业管理；1980年，密西西比州立大学，硕士，专业：林木遗传；1984年，德克萨斯A&M大学，博士，专业：遗传学。

doi: https://doi.org/10.1105/tpc.18.00168

Journal: Plant Cell

First Published: 11 June, 2018

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