Direct visualization of cross-links in the primary plant cell wall
Direct visualization of cross-links in the primary plant cell wall
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发表时间：
1990-06
影响因子：
4
通讯作者：
M. McCann;B. Wells;K. Roberts
中科院分区：
文献类型：
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作者：
M. McCann;B. Wells;K. Roberts
我们在高分辨率下研究了洋葱原代细胞壁的结构，使用快速冷冻的深蚀刻标本的阴影复制品。我们依次从壁上提取聚合物，并在每个提取步骤中可视化这些和剩余的结构。通过观察尽可能接近其原始状态的结构，通过观察立体成对的显微照片，可以组装出一幅精确的墙壁结构的三维图像。我们的观察表明，我们在完整壁上观察到的纤维素微原纤维之间的物理连接通常比我们提取的分离分子（30- 100 - 700纳米）短（20-40纳米），这表明在muro中，连接聚合物和纤维素之间必须发生横向相互作用。这些交联是半纤维素的，我们认为它们是木葡聚糖：它们的去除增加了微原纤维的横向结合。na2co3可提取的果胶组分形成一个单独的共延伸网络，其去除不影响基本纤维素/半纤维素的结构。已经获得了墙体结构的层状模型的初步证据。此外，我们提出了半纤维素在维持纤维素微丝有序间距方面的积极作用，可能调节壁孔隙率和强度。我们推导出的基本细胞壁参数对可能的细胞壁模型施加了约束。
We have investigated the structure of the onion primary cell wall at high resolution, using shadowed replicas of rapidly frozen deep-etched specimens. We have sequentially extracted polymers from the wall and have visualized both these and the remaining structures at each extraction step. By viewing the structures in as near their native state as possible, an accurate three-dimensional picture of wall construction has been assembled, facilitated by viewing stereo pairs of micrographs. Our observations show that the physical links between cellulose microfibrils that we observe in the intact wall are generally shorter (20–40 nm) than the isolated molecules we extract (30->700nm), suggesting that lateral interactions must occur between linking polymers and cellulose in muro . These cross-links are hemicellulosic and we believe them to be xyloglucans: their removal allows increased lateral association of microfibrils. Na2CO3-extractable pectic fractions form a separate coextensive network, the removal of which does not affect basic cellulose/ hemicellulose architecture. Preliminary evidence for a lamellate model of wall construction has been obtained. In addition, we propose a positive role for hemicellulose in maintaining the ordered spacing of cellulose micronbrils, perhaps regulating wall porosity and strength. The basic wall parameters that we derive impose constraints on possible cell wall models.