Laboratoire Glycobiologie et Matrice Extracellulaire Végétale, Équipe d'Accueil 4358, Université de Rouen, 76821 Mont Saint Aignan, France.
Plant Physiol. 2012 Aug;159(4):1658-70. doi: 10.1104/pp.112.198507. Epub 2012 May 29.
Root tips of many plant species release a number of border, or border-like, cells that are thought to play a major role in the protection of root meristem. However, little is currently known on the structure and function of the cell wall components of such root cells. Here, we investigate the sugar composition of the cell wall of the root cap in two species: pea (Pisum sativum), which makes border cells, and Brassica napus, which makes border-like cells. We find that the cell walls are highly enriched in arabinose and galactose, two major residues of arabinogalactan proteins. We confirm the presence of arabinogalactan protein epitopes on root cap cell walls using immunofluorescence microscopy. We then focused on these proteoglycans by analyzing their carbohydrate moieties, linkages, and electrophoretic characteristics. The data reveal (1) significant structural differences between B. napus and pea root cap arabinogalactan proteins and (2) a cross-link between these proteoglycans and pectic polysaccharides. Finally, we assessed the impact of root cap arabinogalactan proteins on the behavior of zoospores of Aphanomyces euteiches, an oomycetous pathogen of pea roots. We find that although the arabinogalactan proteins of both species induce encystment and prevent germination, the effects of both species are similar. However, the arabinogalactan protein fraction from pea attracts zoospores far more effectively than that from B. napus. This suggests that root arabinogalactan proteins are involved in the control of early infection of roots and highlights a novel role for these proteoglycans in root-microbe interactions.
许多植物物种的根尖端会释放出许多边缘或类似边缘的细胞，这些细胞被认为在保护根分生组织方面起着重要作用。然而，目前对于这些根细胞的细胞壁成分的结构和功能知之甚少。在这里，我们研究了两种物种（豌豆（Pisum sativum）和油菜（Brassica napus））的根冠细胞的细胞壁的糖组成。豌豆产生边缘细胞，油菜产生类似边缘的细胞。我们发现细胞壁富含阿拉伯糖和半乳糖，这两种是阿拉伯半乳聚糖蛋白的主要残基。我们通过免疫荧光显微镜确认了根冠细胞壁上存在阿拉伯半乳聚糖蛋白表位。然后，我们通过分析其糖基部分、连接和电泳特性，重点研究这些糖蛋白。数据揭示了（1）油菜和豌豆根冠阿拉伯半乳聚糖蛋白之间存在显著的结构差异，（2）这些糖蛋白与果胶多糖之间存在交联。最后，我们评估了根冠阿拉伯半乳聚糖蛋白对豌豆根病原菌 Aphanomyces euteiches 游动孢子行为的影响。我们发现，尽管两种物种的阿拉伯半乳聚糖蛋白都诱导包囊形成并阻止萌发，但两种物种的效果相似。然而，豌豆的阿拉伯半乳聚糖蛋白片段比油菜的更有效地吸引游动孢子。这表明根阿拉伯半乳聚糖蛋白参与了对根部早期感染的控制，并突出了这些糖蛋白在根-微生物相互作用中的新作用。
