Bajer A S, Smirnova E A
Biology Department, University of Oregon, Eugene, Oregon, 97403-1210, USA.
Cell Motil Cytoskeleton. 1999 Oct;44(2):96-109. doi: 10.1002/(SICI)1097-0169(199910)44:2<96::AID-CM2>3.0.CO;2-T.
We followed time-dependent post-telophase reorganization of the microtubule cytoskeleton on immunostained preparations of endosperm of the higher plant Haemanthus. After completion of mitosis, the phragmoplast continued to reorganize for several hours. This prompted the formation of phragmoplast-like derivatives (secondary and accessory phragmoplasts and peripheral microtubular ring). Next, elongated cellular protrusions (processes) appeared at the cell periphery. These processes contained long microtubule bundles and disorderly arranged actin filaments. Microtubule converging centers or accessory phragmoplasts were often present at the tips of the processes. Observation in vivo demonstrated that processes were formed at the cell periphery as extensions of lammelipodia or filopodia-type protrusions that commonly terminated with cytoplasmic blobs. We suggest that processes are derivatives of a peripheral microtubular ring that reorganizes gradually into cellular protrusions. Endosperm processes have several features of neuronal cells, or animal somatic cells with overexpressed MAPs. Since microtubule-containing processes were never detected shortly after extrusion of the cells from the embryo sac, this course of events might be restricted specifically to extruded endosperm and triggered either by removal of cells, their placement in monolayer on agar substrate, or both. Thus, post telophase behavior of endosperm cells offers a novel experimental system for studies of cytoskeleton in higher plants.
我们在高等植物海葱胚乳的免疫染色制剂上追踪了微管细胞骨架在末期后随时间的重组情况。有丝分裂完成后，成膜体持续重组了数小时。这促使形成了成膜体样衍生物（次生和辅助成膜体以及外周微管环）。接下来，细长的细胞突起（细胞突）出现在细胞周边。这些细胞突包含长的微管束和排列无序的肌动蛋白丝。微管汇聚中心或辅助成膜体常出现在细胞突的顶端。体内观察表明，细胞突是在细胞周边作为片状伪足或丝状伪足型突起的延伸形成的，这些突起通常以细胞质小滴结束。我们认为细胞突是外周微管环的衍生物，它逐渐重组为细胞突起。胚乳细胞突具有神经元细胞或过表达微管相关蛋白（MAPs）的动物体细胞的若干特征。由于在细胞从胚囊挤出后不久从未检测到含微管的细胞突，这一系列事件可能专门局限于挤出的胚乳，并由细胞的移除、它们在琼脂底物上单层的放置或两者共同触发。因此，胚乳细胞的末期后行为为高等植物细胞骨架的研究提供了一个新的实验系统。
