Department of Plant Biology, College of Biological Sciences, University of California, Davis, CA 95616, USA; State Key Laboratory of Crop Gene Exploration and Utilization in Southwest China, Sichuan Agricultural University, Chengdu, Sichuan 611130, China; Triticeae Research Institute, Sichuan Agricultural University, Chengdu 611130, China.
Department of Plant Biology, College of Biological Sciences, University of California, Davis, CA 95616, USA.
Curr Biol. 2024 Aug 19;34(16):3747-3762.e6. doi: 10.1016/j.cub.2024.07.020.
The acentrosomal spindle apparatus has kinetochore fibers organized and converged toward opposite poles; however, mechanisms underlying the organization of these microtubule fibers into an orchestrated bipolar array were largely unknown. Kinesin-14D is one of the four classes of Kinesin-14 motors that are conserved from green algae to flowering plants. In Arabidopsis thaliana, three Kinesin-14D members displayed distinct cell cycle-dependent localization patterns on spindle microtubules in mitosis. Notably, Kinesin-14D1 was enriched on the midzone microtubules of prophase and mitotic spindles and later persisted in the spindle and phragmoplast midzones. The kinesin-14d1 mutant had kinetochore fibers disengaged from each other during mitosis and exhibited hypersensitivity to the microtubule-depolymerizing herbicide oryzalin. Oryzalin-treated kinesin-14d1 mutant cells had kinetochore fibers tangled together in collapsed spindle microtubule arrays. Kinesin-14D1, unlike other Kinesin-14 motors, showed slow microtubule plus end-directed motility, and its localization and function were dependent on its motor activity and the novel malectin-like domain. Our findings revealed a Kinesin-14D1-dependent mechanism that employs interpolar microtubules to regulate the organization of kinetochore fibers for acentrosomal spindle morphogenesis.
无中心体纺锤体装置具有向相反两极组织和汇聚的动粒纤维；然而，将这些微管纤维组织成协调的双极阵列的机制在很大程度上是未知的。Kinesin-14D 是从绿藻到开花植物都保守的四种 Kinesin-14 马达之一。在拟南芥中，三个 Kinesin-14D 成员在有丝分裂的纺锤体微管上显示出不同的细胞周期依赖性定位模式。值得注意的是，Kinesin-14D1 在前期和有丝分裂纺锤体的中带微管上富集，并在纺锤体和胞质分裂中带中持续存在。kinesin-14d1 突变体的动粒纤维在有丝分裂期间彼此脱离，并对微管解聚除草剂草丁膦表现出超敏性。用草丁膦处理的 kinesin-14d1 突变体细胞的动粒纤维在塌陷的纺锤体微管阵列中缠结在一起。与其他 Kinesin-14 马达不同，Kinesin-14D1 显示出缓慢的微管正端定向运动，其定位和功能依赖于其马达活性和新型甘露糖结合样结构域。我们的发现揭示了一种 Kinesin-14D1 依赖性机制，该机制利用极间微管来调节动粒纤维的组织，以实现无中心体纺锤体形态发生。
