Microtubule and katanin-dependent dynamics of microtubule nucleation complexes in the acentrosomal Arabidopsis cortical array
Microtubule and katanin-dependent dynamics of microtubule nucleation complexes in the acentrosomal Arabidopsis cortical array
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DOI：
10.1038/ncb2110
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发表时间：
2010-11-01
影响因子：
21.3
通讯作者：
Hashimoto, Takashi
中科院分区：
文献类型：
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作者：
Nakamura, Masayoshi;Ehrhardt, David W.;Hashimoto, Takashi
间期植物细胞中的微管成核主要是通过细胞皮层分散位点上预先存在的微管的分支发生的(1,2,3)。新微管的负端通常从成核位点释放，然后通过聚合物跑步机将游离微管转移到新位置(1)。这些成核和释放事件是间期细胞中植物阵列的特征，但人们对成核蛋白复合物对这些事件的时空控制知之甚少。我们对拟南芥中两种荧光标记的 γ-微管蛋白复合蛋白 GCP2 和 GCP3 的动态进行了可视化。这些探针标记了细胞质中的运动复合物，该复合物瞬时稳定在细胞皮层的固定位置。标记复合物的募集优先发生在现有的皮质微管上，新的微管以分支方式合成，或者与现有的微管平行。定位于微管的复合物显示成核的可能性比募集到其他位置的复合物高大约 10 倍。成核复合物保持稳定，直到子微管从正端完全解聚或通过剑蛋白依赖性切断活性释放。这些观察结果表明，成核复合物主要在与微管晶格的关联上被激活，并且成核复合物的稳定性取决于与子微管的关联，并且部分地受到剑蛋白活性的调节。
Microtubule nucleation in interphase plant cells primarily occurs through branching from pre-existing microtubules at dispersed sites in the cell cortex(1,2,3). The minus ends of new microtubules are often released from the sites of nucleation, and the free microtubules are then transported to new locations by polymer treadmilling(1). These nucleation-and-release events are characteristic features of plant arrays in interphase cells, but little is known about the spatiotemporal control of these events by nucleating protein complexes. We visualized the dynamics of two fluorescently-tagged gamma-tubulin complex proteins, GCP2 and GCP3, in Arabidopsis thaliana. These probes labelled motile complexes in the cytosol that transiently stabilized at fixed locations in the cell cortex. Recruitment of labelled complexes occurred preferentially along existing cortical microtubules, from which new microtubule was synthesized in a branching manner, or in parallel to the existing microtubule. Complexes localized to microtubules were approximately 10-fold more likely to display nucleation than were complexes recruited to other locations. Nucleating complexes remained stable until daughter microtubules were either completely depolymerized from their plus ends or released by katanin-dependent severing activity. These observations suggest that the nucleation complexes are primarily activated on association with microtubule lattices, and that nucleation complex stability depends on association with daughter microtubules and is regulated in part by katanin activity.