Department of Biology, Hamilton College, Clinton, NY 13323, USA.
Department of Genetics, University of Georgia, Athens, GA 30602, USA.
Int J Mol Sci. 2022 Apr 13;23(8):4293. doi: 10.3390/ijms23084293.
The success of an organism is contingent upon its ability to faithfully pass on its genetic material. In the meiosis of many species, the process of chromosome segregation requires that bipolar spindles be formed without the aid of dedicated microtubule organizing centers, such as centrosomes. Here, we describe detailed analyses of acentrosomal spindle assembly and disassembly in time-lapse images, from live meiotic cells of . Microtubules organized on the nuclear envelope with a perinuclear ring structure until nuclear envelope breakdown, at which point microtubules began bundling into a bipolar form. However, the process and timing of spindle assembly was highly variable, with frequent assembly errors in both meiosis I and II. Approximately 61% of cells formed incorrect spindle morphologies, with the most prevalent being tripolar spindles. The erroneous spindles were actively rearranged to bipolar through a coalescence of poles before proceeding to anaphase. Spindle disassembly occurred as a two-state process with a slow depolymerization, followed by a quick collapse. The results demonstrate that maize meiosis I and II spindle assembly is remarkably fluid in the early assembly stages, but otherwise proceeds through a predictable series of events.
生物体的成功取决于其忠实传递遗传物质的能力。在许多物种的减数分裂中，染色体分离的过程需要形成没有专门微管组织中心（如中心体）帮助的两极纺锤体。在这里，我们描述了对活减数分裂细胞中无中心体纺锤体组装和拆卸的详细分析。微管在核膜上组织成核周环结构，直到核膜破裂，此时微管开始聚集成两极形式。然而，纺锤体组装的过程和时间高度可变，在减数分裂 I 和 II 中经常出现组装错误。大约 61%的细胞形成了不正确的纺锤体形态，最常见的是三极纺锤体。错误的纺锤体通过极的合并被积极地重新排列成两极，然后进入后期。纺锤体的拆卸是一个双态过程，缓慢解聚，然后迅速崩溃。结果表明，玉米减数分裂 I 和 II 的纺锤体组装在早期组装阶段非常不稳定，但除此之外，它还通过一系列可预测的事件进行。
