A mutation in MRH2 kinesin enhances the root hair tip growth defect caused by constitutively activated ROP2 small GTPase in Arabidopsis.
A mutation in MRH2 kinesin enhances the root hair tip growth defect caused by constitutively activated ROP2 small GTPase in Arabidopsis.
复制标题
MRH2驱动蛋白中的突变会增强拟南芥中组成型活化的ROP2小GTPase引起的根尖端生长缺陷。
DOI：
10.1371/journal.pone.0001074
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发表时间：
2007-10-24
期刊：
影响因子：
3.7
通讯作者：
Zheng, Zhi-Liang
中科院分区：
文献类型：
--
作者：
Yang, Guohua;Gao, Peng;Zhang, Hua;Huang, Shanjin;Zheng, Zhi-Liang
根尖的生长为植物细胞极性的研究提供了一个独特的模型系统。表达组成型活性（CA）形式的ROP（Rho-of-plants）GTP酶的转基因植物已被证明可能由于肌动蛋白丝（AF）和微管（MT）组织的改变而引起根毛极性的破坏。为了理解ROP控制根尖生长过程中细胞骨架组织的机制，我们使用CA 1 -1筛选了CA-rop 2抑制剂或增强剂，CA 1 -1是一种表达CA-rop 2的转基因株系，仅显示出对根尖生长的轻度破坏。在这里，我们报告的CA-rop 2增强子（cae 1 -1 CA 1 -1），表现出球根状根毛的表征。cae 1 -1突变本身引起了波浪状和分支状根毛表型。CAE 1编码与根毛生长相关的、含有ARM结构域的驱动蛋白样蛋白MRH 2（因此，CAE 1 -1被重新命名为mrh 2 -3）。皮层MT显示碎片和随机取向的mrh 2根毛。因此，MT稳定药物紫杉醇可以部分挽救mrh 2 -3的波浪状根毛表型，而MT解聚药物Oryzalin轻微地增强了CA 1 -1的根毛尖端生长缺陷。有趣的是，加入肌动蛋白解聚药物Latrunculin B进一步增强了Oryzalin的作用。这表明MT和AF组织的串扰对于mrh 2 -3 CA 1 -1表型是重要的。虽然我们没有观察到MRH 2突变在AF组织中的明显作用，但我们发现mrh 2 -3根毛生长对Latrunculin B更敏感。此外，含有ARM结构域的MRH 2片段可以在体外与聚合的肌动蛋白结合。因此，我们的遗传分析，细胞生物学和药理学证据表明，植物特异性驱动蛋白相关蛋白MRH 2是一个重要的组成部分，控制MT组织，并可能参与ROP 2 GTP酶控制的AF和MT的协调极化生长的根毛。
Root hair tip growth provides a unique model system for the study of plant cell polarity. Transgenic plants expressing constitutively active (CA) forms of ROP (Rho-of-plants) GTPases have been shown to cause the disruption of root hair polarity likely as a result of the alteration of actin filaments (AF) and microtubules (MT) organization. Towards understanding the mechanism by which ROP controls the cytoskeletal organization during root hair tip growth, we have screened for CA-rop2 suppressors or enhancers using CA1-1, a transgenic line that expresses CA-rop2 and shows only mild disruption of tip growth. Here, we report the characterization of a CA-rop2 enhancer (cae1-1 CA1-1) that exhibits bulbous root hairs. The cae1-1 mutation on its own caused a waving and branching root hair phenotype. CAE1 encodes the root hair growth-related, ARM domain-containing kinesin-like protein MRH2 (and thus cae1-1 was renamed to mrh2-3). Cortical MT displayed fragmentation and random orientation in mrh2 root hairs. Consistently, the MT-stabilizing drug taxol could partially rescue the wavy root hair phenotype of mrh2-3, and the MT-depolymerizing drug Oryzalin slightly enhanced the root hair tip growth defect in CA1-1. Interestingly, the addition of the actin-depolymerizing drug Latrunculin B further enhanced the Oryzalin effect. This indicates that the cross-talk of MT and AF organization is important for the mrh2-3 CA1-1 phenotype. Although we did not observe an apparent effect of the MRH2 mutation in AF organization, we found that mrh2-3 root hair growth was more sensitive to Latrunculin B. Moreover, an ARM domain-containing MRH2 fragment could bind to the polymerized actin in vitro. Therefore, our genetic analyses, together with cell biological and pharmacological evidence, suggest that the plant-specific kinesin-related protein MRH2 is an important component that controls MT organization and is likely involved in the ROP2 GTPase-controlled coordination of AF and MT during polarized growth of root hairs.
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