Song Sang-Kee, Lee Myeong Min, Clark Steven E
Department of Molecular, Cellular and Developmental Biology, University of Michigan, Ann Arbor, MI 48109-1048, USA.
Development. 2006 Dec;133(23):4691-8. doi: 10.1242/dev.02652. Epub 2006 Nov 1.
The post-embryonic development of above-ground tissues in plants is dependent upon the maintenance and differentiation of stem cells at the shoot meristem. The Arabidopsis WUSCHEL (WUS) transcription factor establishes an organizing center within the shoot meristem that is essential for specification of stem-cell identity in overlying cells. The CLAVATA (CLV) signaling pathway, including the CLV1 receptor-kinase, promotes the differentiation of stem cells by limiting the WUS expression domain, yet the mechanism of CLV signaling is largely unknown. Previously, we have shown that mutations in two protein phosphatases, POLTERGEIST (POL) and PLL1, partially suppress clv mutant phenotypes. Here, we demonstrate that POL and PLL1 are integral components of the CLV1 signaling pathway. POL and PLL1 are essential for stem-cell specification, and can also block stem-cell differentiation when overexpressed. We provide extensive evidence that POL and PLL1 act downstream of CLV signaling to maintain WUS expression and that they regulate WUS at a transcriptional level. Our findings suggest that POL and PLL1 are central players in regulating the balance between stem-cell maintenance and differentiation, and are the closest known factors to WUS regulation in the shoot meristem.
植物地上组织的胚后发育依赖于茎尖分生组织中干细胞的维持和分化。拟南芥的WUSCHEL（WUS）转录因子在茎尖分生组织内建立了一个组织中心，这对于确定上层细胞中的干细胞身份至关重要。包括CLV1受体激酶在内的CLAVATA（CLV）信号通路通过限制WUS表达域来促进干细胞的分化，然而CLV信号传导的机制在很大程度上尚不清楚。此前，我们已经表明，两种蛋白磷酸酶POLTERGEIST（POL）和PLL1的突变部分抑制了clv突变体表型。在这里，我们证明POL和PLL1是CLV1信号通路的组成部分。POL和PLL1对于干细胞的特化至关重要，并且在过表达时也可以阻止干细胞分化。我们提供了大量证据表明，POL和PLL1在CLV信号传导的下游起作用以维持WUS表达，并且它们在转录水平上调节WUS。我们的研究结果表明，POL和PLL1是调节干细胞维持和分化之间平衡的核心因子，并且是茎尖分生组织中已知最接近WUS调控的因子。
