Pectin Metabolism and Assembly in the Cell Wall of the Charophyte Green Alga Penium margaritaceum
Pectin Metabolism and Assembly in the Cell Wall of the Charophyte Green Alga Penium margaritaceum
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DOI：
10.1104/pp.114.236257
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发表时间：
2014-05-01
期刊：
影响因子：
7.4
通讯作者：
Rose, Jocelyn K. C.
中科院分区：
文献类型：
--
作者：
Domozych, David S.;Sorensen, Iben;Rose, Jocelyn K. C.
果胶聚合物同型半乳糖醛酸 (HG) 是陆地植物细胞壁的主要成分，在中层中含量尤其丰富。目前的模型表明，HG 作为高度甲基酯化的聚合物沉积在壁中，通过果胶甲基酯酶去甲基酯化并通过钙离子交联形成凝胶。然而，这个想法主要基于间接证据和体外研究。我们利用单细胞藻类 Penium margaritaceum 的壁结构来测试该模型和果胶动力学的其他方面，该藻类在其细胞表面形成了精致的钙交联的富含 HG 的晶格。对活细胞和壁域显微成像的研究证实，甲基酯化程度和足够水平的钙对于体内晶格形成至关重要。活细胞的果胶酶处理和免疫学研究表明存在另一类果胶聚合物，鼠李糖半乳糖醛酸 I，并表明其与 HG 的共定位和结构关联。对 P. margaritaceum、Physcomitrella patens 和拟南芥 (Arabidopsis thaliana) 壁的碳水化合物微阵列分析进一步表明绿色植物壁中果胶组织和互聚物缔合的保存。 HG 聚合物的各个组成部分也具有与有胚植物相似的大小和支化结构。 P. margaritaceum 富含 HG 的晶格是轮藻绿藻的一种，是陆地植物的直接祖先，已被证明对细胞粘附很重要。因此，细胞表面的钙-HG 凝胶可能代表了早期的进化创新，为多细胞陆地植物中的粘合中层铺平了道路。
The pectin polymer homogalacturonan (HG) is a major component of land plant cell walls and is especially abundant in the middle lamella. Current models suggest that HG is deposited into the wall as a highly methylesterified polymer, demethylesterified by pectin methylesterase enzymes and cross-linked by calcium ions to form a gel. However, this idea is based largely on indirect evidence and in vitro studies. We took advantage of the wall architecture of the unicellular alga Penium margaritaceum, which forms an elaborate calcium cross-linked HG-rich lattice on its cell surface, to test this model and other aspects of pectin dynamics. Studies of live cells and microscopic imaging of wall domains confirmed that the degree of methylesterification and sufficient levels of calcium are critical for lattice formation in vivo. Pectinase treatments of live cells and immunological studies suggested the presence of another class of pectin polymer, rhamnogalacturonan I, and indicated its colocalization and structural association with HG. Carbohydrate microarray analysis of the walls of P. margaritaceum, Physcomitrella patens, and Arabidopsis (Arabidopsis thaliana) further suggested the conservation of pectin organization and interpolymer associations in the walls of green plants. The individual constituent HG polymers also have a similar size and branched structure to those of embryophytes. The HG-rich lattice of P. margaritaceum, a member of the charophyte green algae, the immediate ancestors of land plants, was shown to be important for cell adhesion. Therefore, the calcium-HG gel at the cell surface may represent an early evolutionary innovation that paved the way for an adhesive middle lamella in multicellular land plants.