QUANTITATIVE ANALYSIS OF CHANGE IN GEOMETRY OF MICROTUBULES IN PLANT CYTOKINESIS

这个子项目是许多利用 由NIH/NCRR资助的中心赠款提供的资源。子项目和 研究者（PI）可能从另一个NIH来源获得了主要资金， 因此可在其他CRISP条目中表示。所列机构为 研究中心，而研究中心不一定是研究者所在的机构。 利用高压冷冻/冷冻置换样品的电子断层扫描技术，在7 nm左右的三维分辨率下研究了拟南芥分生组织细胞的胞质分裂过程。 我们的数据表明，细胞板组装从三个不同的结构：成膜体初始，固体成膜体，和环形成膜体。 成膜体的原始细胞出现在后期的极微管（MT）在细胞的中平面的集群。 细胞板组装位点起始于核糖体排斥的细胞板组装基质（CPAM）和高尔基体衍生的囊泡。 CPAM似乎负责调节细胞板生长和锚定MT（+）末端。 这种结合将囊泡导向CPAM，从而导向生长的细胞板。 在囊泡在CPAM内积累之后，细胞板形成开始于由外囊样复合物束缚囊泡。 囊泡融合产生沙漏形囊泡，这些囊泡通过发动蛋白弹簧扩张而拉伸成哑铃状。同时成膜体原始细胞和它们的CPAM侧向扩展，形成固体成膜体。 随后到达的囊泡与哑铃的球状末端融合，产生管状囊泡膜网络（TVN）。 在完成TVN后，CPAM和MT分解，然后在外围环中改革。 这产生了离心扩张的外周细胞板生长区，这导致细胞板与细胞壁融合。 同时，中央TVN成熟为管状网络（TN），并最终成为一个平面的穿孔片（PFS），通过网格蛋白包被的囊泡和胼胝质合成的膜的去除。 锚定MT的小型二级CPM在大窗孔上方重新出现，以将局部生长集中在这些区域。 当所有的窗孔都关闭时，新的细胞壁就完成了。 Segui-Simarro，J.M.，J.R. Austin II，E.A.白色和洛杉矶。Staehelin（2004）Plant Cell 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.