Vos Jan W, Dogterom Marileen, Emons Anne Mie C
Laboratory of Plant Cell Biology, Wageningen University, Wageningen, The Netherlands.
Cell Motil Cytoskeleton. 2004 Apr;57(4):246-58. doi: 10.1002/cm.10169.
The dynamic behavior of the microtubule cytoskeleton plays a crucial role in cellular organization, but the physical mechanisms underlying microtubule (re)organization in plant cells are poorly understood. We investigated microtubule dynamics in tobacco BY-2 suspension cells during interphase and during the formation of the preprophase band (PPB), the cytoskeletal structure that defines the site of cytokinesis. Here we show that after 2 h of microtubule accumulation in the PPB and concurrent disappearance elsewhere in the cortex, the PPB is completed and starts to breakdown exponentially already 20 min before the onset of prometaphase. During formation of the PPB, the dynamic instability, i.e., the stochastic alternating between growing and shrinking phases, of the cortical microtubules outside the PPB increases significantly, but the microtubules do not become shorter. Based on this, as well as on the cross-linking of microtubules in the PPB and the lack of evidence for motor involvement, we propose a "search-and-capture" mechanism for PPB formation, in which the regulation of dynamic instability causes the cortical microtubules to become more dynamic and possibly longer, while the microtubule cross-linking activity of the developing PPB preferentially stabilizes these "searching" microtubules. Thus, microtubules gradually disappear from the cortex outside the PPB and aggregate to the forming PPB.
微管细胞骨架的动态行为在细胞组织中起着至关重要的作用，但植物细胞中微管（重新）组织的物理机制却鲜为人知。我们研究了烟草BY-2悬浮细胞在间期和前期带（PPB）形成过程中的微管动态，前期带是定义胞质分裂位点的细胞骨架结构。在这里，我们表明，在微管在PPB中积累2小时并同时在皮层其他部位消失后，PPB完成并在有丝分裂前期开始前20分钟就已经开始指数级解体。在PPB形成过程中，PPB外皮层微管的动态不稳定性，即生长和收缩阶段之间的随机交替，显著增加，但微管并没有变短。基于此，以及PPB中微管的交联和缺乏动力参与的证据，我们提出了一种PPB形成的“搜索与捕获”机制，其中动态不稳定性的调节导致皮层微管变得更具动态性且可能更长，而发育中的PPB的微管交联活性优先稳定这些“搜索”微管。因此，微管逐渐从PPB外的皮层消失并聚集到形成中的PPB。
