QUANTITATIVE ANALYSIS OF CHANGE IN GEOMETRY OF MICROTUBULES IN PLANT CYTOKINESIS

这个子项目是许多研究子项目中利用 资源由NIH/NCRR资助的中心拨款提供。子项目和 调查员(PI)可能从NIH的另一个来源获得了主要资金， 并因此可以在其他清晰的条目中表示。列出的机构是 该中心不一定是调查人员的机构。 用高压冷冻/冷冻替代样品的电子断层扫描研究了拟南芥分生组织细胞的胞质分裂，其三维分辨率约为7 nm。我们的数据表明，细胞板由三种不同的结构组成：成膜体首字母、实心成膜体和环状成膜体。成膜体起始于细胞中面的一簇团极微管(MT)，形成于细胞后期。细胞板组装部位起源于不含核糖体的细胞板组装基质(CPAM)和高尔基体衍生的小泡。CPAM似乎既负责调节细胞板的生长，又负责锚定MT(+)末端。这种结合将囊泡导向CPAM，从而导向正在生长的细胞板。在囊泡在CPAM内积累后，细胞板的形成始于囊泡被胞外囊状复合体捆绑在一起。囊泡融合产生沙漏状的囊泡，这些囊泡通过动力弹簧扩张而伸展成哑铃。同时，成膜体的首字母和它们的CPAM横向膨胀，形成固体成膜体。稍后到达的囊泡与哑铃的球状末端融合，形成管泡膜网(TVN)。在TVN完成后，CPAM和MTS拆卸，然后在外围环中重新组合。这产生了离心式扩张的外围细胞板生长区，导致细胞板与细胞壁融合。同时，中央TVN成熟为管状网络(TN)，并最终通过网状蛋白包裹的囊泡去除膜和通过老茧的合成最终形成平面开窗薄片(PFS)。锚定了MTS的小型二级CPAM在大型隔板上从头开始，将局部增长集中在这些地区。当所有的隔板都关闭时，新的细胞壁就完成了。 Sgui-Simarro，J.M.，J.R.Austin II，E.A.White和L.A.Staehelin(2004)植物细胞16：836-856。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Cytokinesis in Arabidopsis meristem cells has been investigated with a 3D resolution of about 7nm by electron tomography of high-pressure frozen/freeze-substituted samples. Our data demonstrate that cell plates assemble from three distinct structures: phragmoplast initials, a solid phragmoplast, and a ring-shaped phragmoplast. Phragmoplast initials arise during late anaphase from clusters of polar microtubules (MTs) at the cell's midplane. Cell plate assembly sites initiate from a ribosome-excluding, cell plate assembly matrix (CPAM) and Golgi derived vesicles. The CPAM seems to be responsible for both regulating cell plate growth and anchoring MT (+) ends. This association directs vesicles to the CPAM, and thereby to the growing cell plate. After vesicles accumulate within the CPAM, cell plate formation starts with the tethering of vesicles by exocyst-like complexes. Vesicle fusion produces hourglass-shaped vesicles that are stretched to dumbbells by dynamin spring expansion. At the same time, phragmoplast initials and their CPAMs expand laterally to make the solid phragmoplast. Later arriving vesicles fuse with the bulbous ends of the dumbbells, producing a tubulo-vesicular membrane network (TVN). Upon completion of the TVN, the CPAM and MTs disassemble and then reform in a peripheral ring. This creates the centrifugally expanding peripheral cell plate growth zone, which leads to cell plate fusion with the cell wall. Simultaneously, the central TVN matures into a tubular network (TN), and ultimately into a planar fenestrated sheet (PFS), through the removal of membrane via clathrin-coated vesicles and by callose synthesis. Small secondary CPAMs with anchored MTs arise de novo over large fenestrae to focus local growth to these regions. When all of the fenestrae are closed, the new cell wall is complete. Segui-Simarro, J.M., J.R. Austin II, E.A. White and L.A. Staehelin (2004) Plant Cell 16:836-856.