University of Tübingen, Center for Plant Molecular Biology - Developmental Genetics, Auf der Morgenstelle 32, 72076 Tübingen, Germany.
Plant Cell. 2021 Mar 22;33(1):27-43. doi: 10.1093/plcell/koaa003.
The bipolar mitotic spindle is a highly conserved structure among eukaryotes that mediates chromosome alignment and segregation. Spindle assembly and size control are facilitated by force-generating microtubule-dependent motor proteins known as kinesins. In animals, kinesin-12 cooperates with kinesin-5 to produce outward-directed forces necessary for spindle assembly. In plants, the relevant molecular mechanisms for spindle formation are poorly defined. While an Arabidopsis thaliana kinesin-5 ortholog has been identified, the kinesin-12 ortholog in plants remains elusive. In this study, we provide experimental evidence for the function of Arabidopsis KINESIN-12E in spindle assembly. In kinesin-12e mutants, a delay in spindle assembly is accompanied by the reduction of spindle size, demonstrating that KINESIN-12E contributes to mitotic spindle architecture. Kinesin-12E localization is mitosis-stage specific, beginning with its perinuclear accumulation during prophase. Upon nuclear envelope breakdown, KINESIN-12E decorates subpopulations of microtubules in the spindle and becomes progressively enriched in the spindle midzone. Furthermore, during cytokinesis, KINESIN-12E shares its localization at the phragmoplast midzone with several functionally diversified Arabidopsis KINESIN-12 members. Changes in the kinetochore and in prophase and metaphase spindle dynamics occur in the absence of KINESIN-12E, suggest it might play an evolutionarily conserved role during spindle formation similar to its spindle-localized animal kinesin-12 orthologs.
双极有丝分裂纺锤体是真核生物中高度保守的结构，介导染色体的排列和分离。纺锤体的组装和大小控制是通过称为驱动蛋白的产生力的微管依赖性马达蛋白来促进的。在动物中，驱动蛋白-12 与驱动蛋白-5 合作，产生向外的力，这对于纺锤体的组装是必要的。在植物中，纺锤体形成的相关分子机制尚未得到明确定义。虽然已经鉴定出拟南芥的驱动蛋白-5 同源物，但植物中的驱动蛋白-12 同源物仍然难以捉摸。在这项研究中，我们提供了实验证据，证明拟南芥 KINESIN-12E 在纺锤体组装中的功能。在驱动蛋白-12e 突变体中，纺锤体组装的延迟伴随着纺锤体大小的减小，表明 KINESIN-12E 有助于有丝分裂纺锤体结构。驱动蛋白-12E 的定位是有丝分裂阶段特异性的，从前期的核周积累开始。核膜破裂后，KINESIN-12E 装饰纺锤体中的微管亚群，并逐渐富集在纺锤体中部区。此外，在胞质分裂期间，KINESIN-12E 与其在赤道板中期区的定位与几个功能多样化的拟南芥 KINESIN-12 成员共享。在没有 KINESIN-12E 的情况下，动粒和前期和中期纺锤体动力学发生变化，表明它可能在纺锤体形成中发挥类似其纺锤体定位的动物驱动蛋白-12 同源物的保守作用。
