State Key Laboratory of Plant Cell and Chromosome Engineering, Institute of Genetics and Developmental Biology, Innovation Academy for Seed Design, Chinese Academy of Sciences, 100101 Beijing, China.
College of Advanced Agricultural Sciences, University of the Chinese Academy of Sciences, 100049 Beijing, China.
Proc Natl Acad Sci U S A. 2021 May 18;118(20). doi: 10.1073/pnas.2022357118.
The Knl1-Mis12-Ndc80 (KMN) network is an essential component of the kinetochore-microtubule attachment interface, which is required for genomic stability in eukaryotes. However, little is known about plant Knl1 proteins because of their complex evolutionary history. Here, we cloned the homolog from maize () and confirmed it as a constitutive central kinetochore component. Functional assays demonstrated their conserved role in chromosomal congression and segregation during nuclear division, thus causing defective cell division during kernel development when Knl1 transcript was depleted. A 145 aa region in the middle of maize Knl1, that did not involve the MELT repeats, was associated with the interaction of spindle assembly checkpoint (SAC) components Bub1/Mad3 family proteins 1 and 2 (Bmf1/2) but not with the Bmf3 protein. They may form a helical conformation with a hydrophobic interface with the TPR domain of Bmf1/2, which is similar to that of vertebrates. However, this region detected in monocots shows extensive divergence in eudicots, suggesting that distinct modes of the SAC to kinetochore connection are present within plant lineages. These findings elucidate the conserved role of the KMN network in cell division and a striking dynamic of evolutionary patterns in the SAC signaling and kinetochore network.
Knl1-Mis12-Ndc80 (KMN) 网络是动粒-微管附着界面的一个重要组成部分，对于真核生物的基因组稳定性是必需的。然而，由于植物 Knl1 蛋白的复杂进化历史，对其知之甚少。在这里，我们从玉米中克隆了同源物（），并证实它是一个组成性的着丝粒中心成分。功能分析表明，它们在核分裂过程中染色体向心性和分离过程中具有保守作用，因此当 Knl1 转录本耗尽时，导致核发育过程中的细胞分裂缺陷。玉米 Knl1 中间的 145 个氨基酸区域不涉及 MELT 重复序列，与纺锤体组装检查点（SAC）组件 Bub1/Mad3 家族蛋白 1 和 2（Bmf1/2）的相互作用有关，但与 Bmf3 蛋白无关。它们可能与 Bmf1/2 的 TPR 结构域形成一个螺旋构象，具有疏水面，类似于脊椎动物。然而，单子叶植物中检测到的这个区域在双子叶植物中表现出广泛的分化，这表明植物谱系中存在不同的 SAC 与动粒连接模式。这些发现阐明了 KMN 网络在细胞分裂中的保守作用，以及 SAC 信号和动粒网络进化模式的惊人动态。
