Arabidopsis Myosin XI: A Motor Rules the Tracks
Arabidopsis Myosin XI: A Motor Rules the Tracks
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DOI：
10.1104/pp.114.244335
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发表时间：
2014-11-01
期刊：
影响因子：
7.4
通讯作者：
Staiger, Christopher J.
中科院分区：
文献类型：
--
作者：
Cai, Chao;Henty-Ridilla, Jessica L.;Staiger, Christopher J.
植物细胞扩增依赖于囊泡和大分子的细胞内运输，这需要肌球蛋白马达和动态肌动蛋白网络。拟南芥 (Arabidopsis thaliana) 肌球蛋白 XI 为多种细胞器的运动提供动力，包括内质网、高尔基体、内膜囊泡、过氧化物酶体和线粒体。最近的几项研究表明，肌球蛋白 xi 突变体的肌动蛋白组织和动力学发生了变化，表明马达影响它们用于运输的分子轨道。然而，肌球蛋白 XI 调节肌动蛋白组织和动力学的机制有待进一步详细研究。在这里，我们利用活细胞的高时空成像，定量评估了三个肌球蛋白 XI（XI-1、XI-2 和 XI-K）基因敲除 (xi3KO) 的突变体中皮质肌动蛋白阵列的结构和动态行为。除了器官和细胞尺寸明显减小之外，突变体在表皮细胞中还表现出密度较低且更成束的肌动蛋白丝阵列。此外，xi3KO 突变体的整体肌动蛋白动态性受到显着抑制。由于细胞骨架重塑主要是由丝组装/拆卸和易位/屈曲引起的，因此我们还检查了单个肌动蛋白丝的动态行为。我们发现 xi3KO 突变体显着降低了肌动蛋白周转率，丝断裂频率降低了 2 倍。此外，对肌动蛋白丝形状随时间变化的定量分析表明，肌球蛋白 XI 产生使单肌动蛋白丝和肌动蛋白束弯曲和伸直的力。因此，我们的数据提供了遗传证据，表明三种拟南芥 XI 类肌球蛋白通过刺激周转和产生丝状形状变化的力来促进肌动蛋白重塑。
Plant cell expansion relies on intracellular trafficking of vesicles and macromolecules, which requires myosin motors and a dynamic actin network. Arabidopsis (Arabidopsis thaliana) myosin XI powers the motility of diverse cellular organelles, including endoplasmic reticulum, Golgi, endomembrane vesicles, peroxisomes, and mitochondria. Several recent studies show that there are changes in actin organization and dynamics in myosin xi mutants, indicating that motors influence the molecular tracks they use for transport. However, the mechanism by which actin organization and dynamics are regulated by myosin XI awaits further detailed investigation. Here, using high spatiotemporal imaging of living cells, we quantitatively assessed the architecture and dynamic behavior of cortical actin arrays in a mutant with three Myosin XI (XI-1, XI-2, and XI-K) genes knocked out (xi3KO). In addition to apparent reduction of organ and cell size, the mutant showed less dense and more bundled actin filament arrays in epidermal cells. Furthermore, the overall actin dynamicity was significantly inhibited in the xi3KO mutant. Because cytoskeletal remodeling is contributed mainly by filament assembly/disassembly and translocation/buckling, we also examined the dynamic behavior of individual actin filaments. We found that the xi3KO mutant had significantly decreased actin turnover, with a 2-fold reduction in filament severing frequency. Moreover, quantitative analysis of filament shape change over time revealed that myosin XI generates the force for buckling and straightening of both single actin filaments and actin bundles. Thus, our data provide genetic evidence that three Arabidopsis class XI myosins contribute to actin remodeling by stimulating turnover and generating the force for filament shape change.