Gursanscky Nial Rau, Jouannet Virginie, Grünwald Karin, Sanchez Pablo, Laaber-Schwarz Martina, Greb Thomas
Gregor Mendel Institute (GMI), Austrian Academy of Sciences, Vienna Biocenter (VBC), Dr. Bohr-Gasse 3, 1030, Vienna, Austria.
Centre for Organismal Studies (COS), Heidelberg University, Im Neuenheimer Feld 230, 69120, Heidelberg, Germany.
Plant J. 2016 May;86(3):210-20. doi: 10.1111/tpj.13169. Epub 2016 Apr 14.
Plants maintain pools of pluripotent stem cells which allow them to constantly produce new tissues and organs. Stem cell homeostasis in shoot and root tips depends on negative regulation by ligand-receptor pairs of the CLE peptide and leucine-rich repeat receptor-like kinase (LRR-RLK) families. However, regulation of the cambium, the stem cell niche required for lateral growth of shoots and roots, is poorly characterized. Here we show that the LRR-RLK MOL1 is necessary for cambium homeostasis in Arabidopsis thaliana. By employing promoter reporter lines, we reveal that MOL1 is active in a domain that is distinct from the domain of the positively acting CLE41/PXY signaling module. In particular, we show that MOL1 acts in an opposing manner to the CLE41/PXY module and that changing the domain or level of MOL1 expression both result in disturbed cambium organization. Underlining discrete roles of MOL1 and PXY, both LRR-RLKs are not able to replace each other when their expression domains are interchanged. Furthermore, MOL1 but not PXY is able to rescue CLV1 deficiency in the shoot apical meristem. By identifying genes mis-expressed in mol1 mutants, we demonstrate that MOL1 represses genes associated with stress-related ethylene and jasmonic acid hormone signaling pathways which have known roles in coordinating lateral growth of the Arabidopsis stem. Our findings provide evidence that common regulatory mechanisms in different plant stem cell niches are adapted to specific niche anatomies and emphasize the importance of a complex spatial organization of intercellular signaling cascades for a strictly bidirectional tissue production.
植物拥有多能干细胞库，这使它们能够不断产生新的组织和器官。茎尖和根尖的干细胞稳态依赖于CLE肽和富含亮氨酸重复序列的受体样激酶（LRR-RLK）家族的配体-受体对的负调控。然而，形成层（茎和根横向生长所需的干细胞微环境）的调控机制却鲜为人知。在这里，我们表明LRR-RLK MOL1对拟南芥形成层的稳态是必需的。通过使用启动子报告株系，我们发现MOL1在一个与起正向作用的CLE41/PXY信号模块的结构域不同的结构域中具有活性。特别是，我们表明MOL1与CLE41/PXY模块的作用方式相反，并且改变MOL1表达的结构域或水平都会导致形成层组织紊乱。MOL1和PXY具有不同的作用，当它们的表达结构域互换时，这两个LRR-RLK都不能相互替代。此外，MOL1而非PXY能够挽救茎尖分生组织中的CLV1缺陷。通过鉴定在mol1突变体中错误表达的基因，我们证明MOL1抑制与应激相关的乙烯和茉莉酸激素信号通路相关的基因，这些信号通路在协调拟南芥茎的横向生长中具有已知作用。我们的研究结果提供了证据，表明不同植物干细胞微环境中的共同调控机制适应于特定的微环境解剖结构，并强调了细胞间信号级联复杂的空间组织对于严格双向组织产生的重要性。
