Stem cells in plants and animals are maintained pluripotent by signals from adjacent niche cells. In plants, WUSCHEL HOMEOBOX (WOX) transcription factors are central regulators of stem cell maintenance in different meristem types, yet their molecular mode of action has remained elusive. Here we show that in the Arabidopsis root meristem, the WOX5 protein moves from the root niche organizer, the quiescent center, into the columella stem cells, where it directly represses the transcription factor gene CDF4. This creates a gradient of CDF4 transcription, which promotes differentiation opposite to the WOX5 gradient, allowing stem cell daughter cells to exit the stem cell state. We further show that WOX5 represses CDF4 transcription by recruiting TPL/TPR co-repressors and the histone deacetylase HDA19, which consequently induces histone deacetylation at the CDF4 regulatory region. Our results show that chromatin-mediated repression of differentiation programs is a common strategy in plant and animal stem cell niches.

植物和动物中的干细胞通过相邻小生境细胞的信号保持多能。在植物中，WUSCHEL HOMEOBOX（WOX）转录因子是不同分生组织类型中干细胞维持的主要调节剂，但它们的分子作用方式仍然难以捉摸。在这里，我们显示在拟南芥根分生组织中，WOX5蛋白从根生态位组织者（静止中心）移动到小肠干细胞中，在那里它直接抑制转录因子基因CDF4。这产生了CDF4转录梯度，该梯度促进了与WOX5梯度相反的分化，从而允许干细胞子细胞退出干细胞状态。我们进一步证明WOX5抑制CDF4通过招募TPL / TPR共同阻遏物和组蛋白脱乙酰基酶HDA19进行转录，从而在CDF4调节区诱导组蛋白脱乙酰基化。我们的结果表明，染色质介导的分化程序抑制是植物和动物干细胞生态位中的常见策略。