Schmit A C, Lambert A M
Université Louis Pasteur, Institut de Botanique, Strasbourg, France.
J Cell Biol. 1987 Nov;105(5):2157-66. doi: 10.1083/jcb.105.5.2157.
We have identified an F-actin cytoskeletal network that remains throughout interphase, mitosis, and cytokinesis of higher plant endosperm cells. Fluorescent labeling was obtained using actin monoclonal antibodies and/or rhodamine-phalloidin. Video-enhanced microscopy and ultrastructural observations of immunogold-labeled preparations illustrated microfilament-microtubule co-distribution and interactions. Actin was also identified in cell crude extract with Western blotting. During interphase, microfilament and microtubule arrays formed two distinct networks that intermingled. At the onset of mitosis, when microtubules rearranged into the mitotic spindle, microfilaments were redistributed to the cell cortex, while few microfilaments remained in the spindle. During mitosis, the cortical actin network remained as an elastic cage around the mitotic apparatus and was stretched parallel to the spindle axis during poleward movement of chromosomes. This suggested the presence of dynamic cross-links that rearrange when they are submitted to slow and regular mitotic forces. At the poles, the regular network is maintained. After midanaphase, new, short microfilaments invaded the equator when interzonal vesicles were transported along the phragmoplast microtubules. Colchicine did not affect actin distribution, and cytochalasin B or D did not inhibit chromosome transport. Our data on endosperm cells suggested that plant cytoplasmic actin has an important role in the cell cortex integrity and in the structural dynamics of the poorly understood cytoplasm-mitotic spindle interface. F-actin may contribute to the regulatory mechanisms of microtubule-dependent or guided transport of vesicles during mitosis and cytokinesis in higher plant cells.
我们已经鉴定出一种贯穿高等植物胚乳细胞间期、有丝分裂期和胞质分裂期的F-肌动蛋白细胞骨架网络。使用肌动蛋白单克隆抗体和/或罗丹明-鬼笔环肽进行荧光标记。对免疫金标记制剂的视频增强显微镜观察和超微结构观察显示了微丝与微管的共分布及相互作用。通过蛋白质免疫印迹法也在细胞粗提物中鉴定出了肌动蛋白。在间期，微丝和微管阵列形成两个相互交织的不同网络。在有丝分裂开始时，当微管重排形成有丝分裂纺锤体时，微丝重新分布到细胞皮层，而纺锤体中仅残留少量微丝。在有丝分裂期间，皮层肌动蛋白网络作为围绕有丝分裂装置的弹性笼而保留，并在染色体向极移动期间沿纺锤体轴平行伸展。这表明存在动态交联，当它们受到缓慢且规则的有丝分裂力作用时会重新排列。在两极，规则网络得以维持。在中期之后，当区间小泡沿成膜体微管运输时，新的短微丝侵入赤道区。秋水仙素不影响肌动蛋白分布，细胞松弛素B或D也不抑制染色体运输。我们关于胚乳细胞的数据表明，植物细胞质肌动蛋白在细胞皮层完整性以及对细胞质-有丝分裂纺锤体界面了解甚少的结构动力学中发挥重要作用。F-肌动蛋白可能有助于高等植物细胞有丝分裂和胞质分裂期间微管依赖性或引导性小泡运输的调节机制。
