Plant growth and development relies on the accurate positioning of the cell plate between dividing cells during cytokinesis. The cell plate is synthetized by a specialized structure called the phragmoplast, which contains bipolar microtubules that polymerize to form a framework with the plus ends at or near the division site. This allows the transport of Golgi-derived vesicles toward the plus ends to form and expand the cell plate. Actin filaments play important roles in cell plate expansion and guidance in plant cytokinesis at the late phase, but whether they are involved at the early phase is unknown. To investigate this further, we disrupted the actin filaments in cell cycle-synchronized tobacco BY-2 cells with latrunculin B (LatB), an actin polymerization inhibitor. We observed the cells under a transmission electron microscope or a spinning-disk confocal laser scanning microscope. We found that disruption of actin filaments by LatB caused the membrane vesicles at the equatorial plane of the cell plate to be dispersed rather than form clusters as they did in the untreated cells. The midzone constriction of phragmoplast microtubules also was perturbed in LatB-treated cells. The live cell imaging and kymograph analysis showed that disruption of actin filaments also changed the accumulation timing of NACK1 kinesin, which plays a crucial role in cell plate expansion. This suggests that there are two functionally different types of microtubules in the phragmoplast. Together, our results show that actin filaments regulate phragmoplast microtubules at the initial phase of plant cytokinesis.

中文翻译：

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肌动蛋白丝断裂改变植物细胞分裂初始阶段的成膜体微管动力学。


植物的生长和发育依赖于胞质分裂过程中分裂细胞之间细胞板的准确定位。细胞板是由一种称为成膜体的特殊结构合成的，它含有双极微管，这些微管聚合形成一个框架，其正端位于或靠近分裂位点。这允许高尔基体衍生的囊泡向正端运输，以形成和扩张细胞板。肌动蛋白丝在细胞板扩张和植物胞质分裂后期的指导中发挥重要作用，但它们是否参与早期阶段尚不清楚。为了进一步研究这一点，我们用肌动蛋白聚合抑制剂 latrunculin B (LatB) 破坏了细胞周期同步的烟草 BY-2 细胞中的肌动蛋白丝。我们在透射电子显微镜或转盘共焦激光扫描显微镜下观察细胞。我们发现，LatB 对肌动蛋白丝的破坏导致细胞板赤道面的膜囊泡分散，而不是像未处理的细胞中那样形成簇。 LatB 处理的细胞中成膜体微管的中区收缩也受到干扰。活细胞成像和 kymograph 分析表明，肌动蛋白丝的破坏也改变了 NACK1 驱动蛋白的积累时间，这在细胞板扩张中起着至关重要的作用。这表明成膜体中有两种功能不同类型的微管。总之，我们的结果表明，肌动蛋白丝在植物胞质分裂的初始阶段调节成膜体微管。