Stahl Yvonne, Wink René H, Ingram Gwyneth C, Simon Rüdiger
Institut für Genetik, Heinrich-Heine Universität, Universitätsstrasse 1, D-40225 Düsseldorf, Germany.
Curr Biol. 2009 Jun 9;19(11):909-14. doi: 10.1016/j.cub.2009.03.060. Epub 2009 Apr 23.
The niches of the Arabidopsis shoot and root meristems, the organizing center (OC) and the quiescent center (QC), orchestrate the fine balance of stem cell maintenance and the provision of differentiating descendants. They express the functionally related homeobox genes WUSCHEL (WUS) and WOX5, respectively, that promote stem cell fate in adjacent cells. Shoot stem cells signal back to the OC by secreting the CLAVATA3 (CLV3) dodecapeptide, which represses WUS expression. However, the signals controlling homeostasis of the root stem cell system are not identified to date. Here we show that the differentiating descendants of distal root stem cells express CLE40, a peptide closely related to CLV3. Reducing CLE40 levels delays differentiation and allows stem cell proliferation. Conversely, increased CLE40 levels drastically alter the expression domain of WOX5 and promote stem cell differentiation. We report that the receptor kinase ACR4, previously shown to control cell proliferation, is an essential component, and also a target, of CLE40 signaling. Our results reveal how, in contrast to the shoot system, signals originating from differentiated cells, but not the stem cells, determine the size and position of the root niche.
拟南芥地上部和根分生组织的生态位，即组织中心（OC）和静止中心（QC），协调着干细胞维持和分化后代供应之间的精细平衡。它们分别表达功能相关的同源异型盒基因WUSCHEL（WUS）和WOX5，这些基因促进相邻细胞中的干细胞命运。地上部干细胞通过分泌CLAVATA3（CLV3）十二肽向组织中心发出信号，该十二肽可抑制WUS表达。然而，迄今为止，尚未确定控制根干细胞系统稳态的信号。在这里，我们表明，远基根干细胞的分化后代表达CLE40，这是一种与CLV3密切相关的肽。降低CLE40水平会延迟分化并允许干细胞增殖。相反，增加CLE40水平会极大地改变WOX5的表达域并促进干细胞分化。我们报道，先前显示可控制细胞增殖的受体激酶ACR4是CLE40信号传导的重要组成部分，也是其作用靶点。我们的结果揭示了与地上部系统不同，源自分化细胞而非干细胞的信号如何决定根生态位的大小和位置。
