Self-assembly of the plant cell wall requires an extensin scaffold
Self-assembly of the plant cell wall requires an extensin scaffold
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DOI：
10.1073/pnas.0711980105
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发表时间：
2008-02-12
影响因子：
11.1
通讯作者：
Kieliszewski, Marcia J.
中科院分区：
文献类型：
--
作者：
Cannon, Maura C.;Terneus, Kimberly;Kieliszewski, Marcia J.
细胞分裂在动物中通过卵裂沟分隔细胞，但在植物中通过新的横壁分隔细胞。这种新壁如何在分子水平上组装并与母细胞壁连接仍不清楚。一种被称为根、芽、下胚轴缺陷 (rsh) 的致命拟南芥胚胎发生突变体提供了一些线索：RSH 编码延伸蛋白 AtEXT3，这是一种位于新生横壁或“细胞板”以及成熟细胞壁中的结构糖蛋白。在这里，我们报告缺乏 RSH 延伸蛋白的 rsh 突变细胞的电子显微照片对应于以不完整的跨壁组装为代表的壁表型。从野生型拟南芥细胞培养物中分离出来的纯化 RSH 糖蛋白的生化特征证实了其与 AtEXT3 的身份：一种富含 (羟基) 脯氨酸的糖蛋白，包含 11 个相同的两亲性肽重复序列，具有 28 个残基周期：SOOOOKKHYVYKSOOOOVKHYSOOOVYH (O = Hyp)，每个重复序列包含一个 疏水性异二酪氨酸交联基序（YVY，下划线）。 RSH 糖蛋白的原子力显微镜对其自组装成树突状支架的倾向进行了成像。延伸蛋白过氧化物酶在体外催化不溶性 RSH 凝胶的形成，并伴随酪氨酸交联，因此在 muro 中存在这种可能性。我们得出结论，富含赖氨酸的 RSH 延伸蛋白的自组装两亲物在细胞板中形成带正电荷的支架。它们与带负电的果胶反应，产生延伸蛋白果胶酸凝聚层，可以在胞质分裂时进一步有序沉积新的横壁。
Cytokinesis partitions the cell by a cleavage furrow in animals but by a new cross wall in plants. How this new wall assembles at the molecular level and connects with the mother cell wall remains unclear. A lethal Arabidopsis embryogenesis mutant designated root-, shoot-, hypocotyl-defective (rsh) provides some clues: RSH encodes extensin AtEXT3, a structural glycoprotein located in the nascent cross wall or "cell plate" and also in mature cell walls. Here we report that electron micrographs of rsh mutant cells lacking RSH extensin correspond to a wall phenotype typified by incomplete cross wall assembly. Biochemical characterization of the purified RSH glycoprotein isolated from wild-type Arabidopsis cell cultures confirmed its identity as AtEXT3: a (hydroxy)proline-rich glycoprotein comprising 11 identical amphiphilic peptide repeats with a 28-residue periodicity: SOOOOKKHYVYKSOOOOVKHYSOOOVYH (O = Hyp), each repeat containing a hydrophobic isodityrosine cross-link motif (YVY, underlined). Atomic force microscopy of RSH glycoprotein imaged its propensity for self-assembly into a dendritic scaffold. Extensin peroxidase catalyzed in vitro formation of insoluble RSH gels with concomitant tyrosine cross-linking, hence this likelihood in muro. We conclude that self-assembling amphiphiles of lysine-rich RSH extensin form positively charged scaffolds in the cell plate. These react with negatively charged pectin to create an extensin pectate coacervate that may template further orderly deposition of the new cross wall at cytokinesis.