背景回顾：The formation of cell polarity is essential for many developmental processes such as polar cell growth and spatial patterning of cell division. A plant-specific ROP (Rho-like GTPases from Plants) subfamily of conserved Rho GTPase plays a crucial role in the regulation of cell polarity. 

提出问题：However, the functional study of ROPs in angiosperm is challenging because of their functional redundancy. 

主要发现：The Marchantia polymorpha genome encodes a single ROP gene, MpROP, providing an excellent genetic system to study ROP-dependent signaling pathways. 

结果1-极性细胞生长：Mprop knockout mutants exhibited rhizoid growth defects, and MpROP was localized at the tip of elongating rhizoids, establishing a role for MpROP in the control of polar cell growth and its functional conservation in plants.  

结果2-分生组织特化：Furthermore, the Mprop knockout mutant showed defects in the formation of meristem notches associated with disorganized cell division patterns. These results reveal a critical function of MpROP in the regulation of plant development.

结果3-功能保守性：Interestingly, these phenotypes were complemented not only by MpROP but also Arabidopsis AtROP2, supporting the conservation of ROP’s function among land plants. 

结论：Our results demonstrate a great potential for M. polymorpha as a powerful genetic system for functional and mechanistic elucidation of ROP signaling pathways during plant development.

The function of ROP is conserved between M. polymorpha and Arabidopsis.

细胞极性的形成对于许多发育进程都是必须的，比如说极性细胞生长和细胞分裂的空间模式建成。一个植物特异性的Rho GTPase亚家族ROP在细胞极性调控方面发挥重要作用。但是，由于功能冗余的影响，被子植物中有关ROPs的功能研究比较难以展开。地钱基因组中只有一个ROP基因，即MpROP，因此为植物中研究ROP依赖性的信号转导途径提供了一个理想材料。Mprop敲除突变体存在假根生长缺陷，并且MpROP定位于伸长中假根的生长顶端，说明MpROP控制了极性的细胞生长且在植物中的功能是保守的。此外，Mprop敲除突变体表现出分生组织缺口形成的缺陷，主要是与异常的细胞分裂模式有关。这些结果表明了MpROP在调控植物发育方面的重要作用。有趣的是，Mprop敲除突变体的缺陷表型能够被MpROP和AtROP2拯救，说明了ROP功能在陆地植物中的保守性。本文的研究结果揭示了地钱作为理想的研究材料，可用于阐释ROP信号转导在植物发育过程中的功能和机制。

** 山室千鹤子 **