Macromolecular differentiation of Golgi stacks in root tips ofArabidopsis andNicotiana seedlings as visualized in high pressure frozen and freeze-substituted samples
Macromolecular differentiation of Golgi stacks in root tips ofArabidopsis andNicotiana seedlings as visualized in high pressure frozen and freeze-substituted samples
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DOI：
10.1007/bf01322640
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发表时间：
2005
期刊：
影响因子：
2.9
通讯作者：
L. Staehelin;T. Giddings;J. Kiss;F. Sack
中科院分区：
文献类型：
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作者：
L. Staehelin;T. Giddings;J. Kiss;F. Sack
植物根尖是研究高尔基体结构变化的一个有趣的模型系统，高尔基体结构变化与分生细胞向重力感知小柱细胞的发育过程有关，最后是“年轻”和“年老”，分泌多糖的外周细胞。为此，我们使用高压冷冻结合冷冻替代技术来跟踪拟南芥和烟叶根尖高尔基堆大分子组织的发育变化。由于所研究的所有细胞的结构保存得到了很大的改善，我们的电子显微照片揭示了所有高尔基体堆共同的几个新的结构特征，以及不同细胞类型的高尔基体堆之间形态学的特征差异。所有高尔基池的共同点是在染色模式和顺式、内侧和反式池的宽度上有明显而离散的差异。顺式池具有最宽的发光（~ 30 nm），并且染色最少。内侧池更窄（约20 nm），充满更多深色染色产物。大多数反式池在其中心区域具有完全塌陷的管腔，在横断面视图中产生4-6纳米宽的暗线。与池缘相关的许多囊泡具有非网格蛋白类型的被膜。具有网格蛋白包被囊泡的反式高尔基网络与所有的高尔基堆积有关，除了老的外周细胞。通过其泡状形态和染色模式很容易与反式池区分。核糖体排斥区既包括高尔基堆，也包括反高尔基网络。池间元件仅位于小柱跨池和外周细胞之间，而不位于分生细胞之间。在较老的外周细胞中，只有反池呈黏液相关染色。具有贮池间元素的高尔基堆在其跨贮池膜中也包含平行的冷冻断裂颗粒行。我们提出池间元素作为参与多糖黏液分子合成的酶复合物的锚点，以防止复合物被非常大的黏液分子拖入形成分泌囊泡。此外，我们还注意到木葡聚糖和黏液分子在组成和表观合成位点上的相似性。
The plant root tip represents a fascinating model system for studying changes in Golgi stack architecture associated with the developmental progression of meristematic cells to gravity sensing columella cells, and finally to “young” and “old”, polysaccharideslime secreting peripheral cells. To this end we have used high pressure freezing in conjunction with freeze-substitution techniques to follow developmental changes in the macromolecular organization of Golgi stacks in root tips ofArabidopsisandNicotiana. Due to the much improved structural preservation of all cells under investigation, our electron micrographs reveal both several novel structural features common to all Golgi stacks, as well as characteristic differences in morphology between Golgi stacks of different cell types.Common to all Golgi stacks are clear and discrete differences in staining patterns and width of cis, medial and trans cisternae. Cis cisternae have the widest lumina (∼30 nm) and are the least stained. Medial cisternae are narrower (∼20 nm) and filled with more darkly staining products. Most trans cisternae possess a completely collapsed lumen in their central domain, giving rise to a 4–6 nm wide dark line in cross-sectional views. Numerous vesicles associated with the cisternal margins carry a non-clathrin type of coat. A trans Golgi network with clathrin coated vesicles is associated with all Golgi stacks except those of old peripheral cells. It is easily distinguished from trans cisternae by its blebbing morphology and staining pattern. The zone of ribosome exclusion includes both the Golgi stack and the trans Golgi network.Intercisternal elements are located exclusively between trans cisternae of columella and peripheral cells, but not meristematic cells. In older peripheral cells only trans cisternae exhibit slime-related staining. Golgi stacks possessing intercisternal elements also contain parallel rows of freeze-fracture particles in their trans cisternal membranes. We propose that intercisternal elements serve as anchors of enzyme complexes involved in the synthesis of polysaccharide slime molecules to prevent the complexes from being dragged into the forming secretory vesicles by the very large slime molecules. In addition, we draw attention to the similarities in composition and apparent site of synthesis of xyloglucans and slime molecules.