The MAP215 family of microtubule (MT) polymerase/nucleation factors and the MT severing enzyme katanin are widely conserved MT-associated proteins (MAPs) across the plant and animal kingdoms. However, how these two essential MAPs coordinate to regulate plant MT dynamics and development remains unknown. Here, we identified novel hypomorphic alleles of MICROTUBULE ORGANIZATION 1 (MOR1), encoding the Arabidopsis thaliana homolog of MAP215, in genetic screens for mutants oversensitive to the MT-destabilizing drug propyzamide. Live imaging in planta revealed that MOR1-green fluorescent protein predominantly tracks the plus-ends of cortical MTs (cMTs) in interphase cells and labels preprophase band, spindle and phragmoplast MT arrays in dividing cells. Remarkably, MOR1 and KATANIN 1 (KTN1), the p60 subunit of Arabidopsis katanin, act synergistically to control the proper formation of plant-specific MT arrays, and consequently, cell division and anisotropic cell expansion. Moreover, MOR1 physically interacts with KTN1 and promotes KTN1-mediated severing of cMTs. Our work establishes the Arabidopsis MOR1-KTN1 interaction as a central functional node dictating MT dynamics and plant growth and development.

中文翻译：

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MOR1/MAP215 与 katanin 协同作用以控制拟南芥中的细胞分裂和各向异性细胞伸长。

MAP215 微管 (MT) 聚合酶/成核因子家族和 MT 切断酶 katanin 是植物和动物界广泛保守的 MT 相关蛋白 (MAP)。然而，这两个基本 MAP 如何协调以调节植物 MT 动力学和发育仍然未知。在这里，我们鉴定了微管组织 1 (MOR1) 的新型亚形态等位基因，编码 MAP215 的拟南芥同系物，用于对 MT 去稳定药物丙嘧酰胺过度敏感的突变体的遗传筛选。足底活体成像显示，MOR1-绿色荧光蛋白主要跟踪间期细胞中皮质 MT (cMT) 的加端，并标记分裂细胞中的前期带、纺锤体和成膜体 MT 阵列。值得注意的是，拟南芥 katanin 的 p60 亚基 MOR1 和 KATANIN 1 (KTN1)，协同作用以控制植物特异性 MT 阵列的正确形成，从而控制细胞分裂和各向异性细胞扩张。此外，MOR1 与 KTN1 物理相互作用并促进 KTN1 介导的 cMT 切断。我们的工作将拟南芥 MOR1-KTN1 相互作用确立为控制 MT 动力学和植物生长发育的中心功能节点。