Graduate School of Biological Sciences, Nara Institute of Science and Technology, 8916-5 Takayama, Ikoma, Nara 630-0192, Japan.
Department of Applied Biological Science, Faculty of Science and Technology, Tokyo University of Science, 2641 Yamazaki, Noda, Chiba 278-8510, Japan.
J Cell Sci. 2018 Jan 29;131(2):jcs203778. doi: 10.1242/jcs.203778.
Plant microtubules (MTs) are nucleated from the γ-tubulin-containing ring complex (γTuRC). In cortical MT arrays of interphase plant cells, γTuRC is preferentially recruited to the lattice of preexisting MTs, where it initiates MT nucleation in either a branch- or bundle-forming manner, or dissociates without mediating nucleation. In this study, we analyzed how γTuRCs influence MT nucleation and dynamics in cotyledon pavement cells of We found that γTuRC nucleated MTs at angles of ∼40° toward the plus-ends of existing MTs, or in predominantly antiparallel bundles. A small fraction of γTuRCs was motile and tracked MT ends. When γTuRCs decorated the depolymerizing MT end, they reduced the depolymerization rate. Non-nucleating γTuRCs associated with the MT lattice promoted MT regrowth after a depolymerization phase. These results suggest that γTuRCs not only nucleate MT growth but also regulate MT dynamics by stabilizing MT ends. On rare occasions, a non-MT-associated γTuRC was pushed in the direction of the MT minus-end, while nucleating a new MT, suggesting that the polymerizing plus-end is anchored to the plasma membrane.
植物微管（MTs）从含有γ-微管蛋白的环复合物（γTuRC）中起始。在植物细胞的间期中皮层 MT 阵列中，γTuRC 优先招募到预先存在的 MT 晶格上，在那里它以分支或束状形成方式起始 MT 起始，或者在不介导起始的情况下解离。在这项研究中，我们分析了 γTuRC 如何影响 cotyledon 铺板细胞中的 MT 起始和动力学。我们发现，γTuRC 在与现有 MT 加端成约 40°的角度处起始 MT，或者在主要的反平行束中起始 MT。一小部分 γTuRC 是运动的并跟踪 MT 末端。当 γTuRC 装饰正在去聚合的 MT 末端时，它们降低了去聚合速率。与 MT 晶格结合的非起始 γTuRC 促进了去聚合阶段后的 MT 再生。这些结果表明，γTuRC 不仅起始 MT 生长，而且通过稳定 MT 末端来调节 MT 动力学。在极少数情况下，一个非 MT 相关的 γTuRC 被推向 MT 负端的方向，同时起始一个新的 MT，这表明聚合的正端被锚定在质膜上。
