McFarlane Heather E, Young Robin E, Wasteneys Geoffrey O, Samuels A Lacey
Department of Botany, University of British Columbia, Vancouver, BC, Canada.
Planta. 2008 May;227(6):1363-75. doi: 10.1007/s00425-008-0708-2. Epub 2008 Feb 29.
During their differentiation Arabidopsis thaliana seed coat cells undergo a brief but intense period of secretory activity that leads to dramatic morphological changes. Pectic mucilage is secreted to one domain of the plasma membrane and accumulates under the primary cell wall in a ring-shaped moat around an anticlinal cytoplasmic column. Using cryofixation/transmission electron microscopy and immunofluorescence, the cytoskeletal architecture of seed coat cells was explored, with emphasis on its organization, function and the large amount of pectin secretion at 7 days post-anthesis. The specific domain of the plasma membrane where mucilage secretion is targeted was lined by abundant cortical microtubules while the rest of the cortical cytoplasm contained few microtubules. Actin microfilaments, in contrast, were evenly distributed around the cell. Disruption of the microtubules in the temperature-sensitive mor1-1 mutant affected the eventual release of mucilage from mature seeds but did not appear to alter the targeted secretion of vesicles to the mucilage pocket, the shape of seed coat cells or their secondary cell wall deposition. The concentration of cortical microtubules at the site of high vesicle secretion in the seed coat may utilize the same mechanisms required for the formation of preprophase bands or the bands of microtubules associated with spiral secondary cell wall thickening during protoxylem development.
在拟南芥种皮细胞分化过程中，会经历一段短暂但强烈的分泌活动期，这会导致显著的形态变化。果胶黏液被分泌到质膜的一个区域，并在初生细胞壁下围绕一个垂周细胞质柱的环形沟中积累。利用冷冻固定/透射电子显微镜和免疫荧光技术，研究了种皮细胞的细胞骨架结构，重点关注其在花后7天的组织、功能以及大量果胶分泌情况。黏液分泌所靶向的质膜特定区域排列着丰富的皮层微管，而皮层细胞质的其余部分微管较少。相比之下，肌动蛋白微丝在细胞周围均匀分布。温度敏感型mor1-1突变体中微管的破坏影响了成熟种子中黏液的最终释放，但似乎并未改变囊泡向黏液囊的靶向分泌、种皮细胞的形状或其次生细胞壁的沉积。种皮中高囊泡分泌部位皮层微管的集中可能利用了原形成层发育过程中前期带或与螺旋次生细胞壁加厚相关的微管带形成所需的相同机制。
