Long Yun, Schiefelbein John
Maize Research Institute, Sichuan Agricultural University, Chengdu, China.
Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI, United States.
Front Plant Sci. 2020 Apr 7;11:383. doi: 10.3389/fpls.2020.00383. eCollection 2020.
The patterning of root-hair and non-hair epidermal cells in the Arabidopsis root is governed by a network of transcriptional regulators. The central MYB-bHLH-WD40 (MBW) transcriptional complex includes the WD40-repeat protein TRANSPARENT TESTA GLABRA1 (TTG1). To clarify the role of TTG1, we describe the identification and analysis of two new mutants. Each of these mutants contains a single nucleotide change in the gene, which causes a single amino-acid substitution in the predicted TTG1 protein and alters root-hair pattern formation. Surprisingly, these new mutants exhibit decreased root-hair formation, particularly in the mutant background, rather than increased root-hair formation as reported for strong mutants. We show that the unique phenotype of these mutants is due to differential effects of the altered TTG1 proteins on target gene expression, associated with a weakened ability to interact with its GLABRA3 bHLH partner. These findings demonstrate the crucial role of TTG1 for the appropriate balance of target gene activation to achieve the proper pattern of epidermal cell types during Arabidopsis root development.
拟南芥根中根毛和非根毛表皮细胞的模式形成受转录调节因子网络的控制。核心的MYB-bHLH-WD40（MBW）转录复合体包括WD40重复蛋白透明种皮光滑1（TTG1）。为了阐明TTG1的作用，我们描述了两个新突变体的鉴定和分析。这些突变体中的每一个在基因中都有一个单核苷酸变化，这导致预测的TTG1蛋白中有一个单氨基酸替换，并改变根毛模式形成。令人惊讶的是，这些新突变体表现出根毛形成减少，特别是在突变体背景中，而不是像报道的强突变体那样根毛形成增加。我们表明，这些突变体的独特表型是由于改变的TTG1蛋白对靶基因表达的不同影响，这与它与GLABRA3 bHLH伙伴相互作用的能力减弱有关。这些发现证明了TTG1在拟南芥根发育过程中对靶基因激活的适当平衡以实现表皮细胞类型的正确模式的关键作用。
