Loss of pectin is an early event during infection of cocoyam roots by Pythium myriotylum
Loss of pectin is an early event during infection of cocoyam roots by Pythium myriotylum
复制标题
DOI：
10.1007/s00425-005-0090-2
复制
发表时间：
2006-01-01
期刊：
影响因子：
4.3
通讯作者：
Driouich, A
中科院分区：
文献类型：
--
作者：
Boudjeko, T;Andème-Onzighi, C;Driouich, A
椰子（Xanthosoma sagittifolium）是非洲和美洲热带地区重要的块茎作物。在喀麦隆，它的种植受到一种土传真菌Pythium myriotylum的阻碍，这种真菌是导致根腐病的原因。真菌在根部定殖的机制尚未阐明。在这项研究中，使用显微镜和免疫细胞化学方法，我们提供了一个新的证据，关于真菌的作用方式，我们描述了植物的反应真菌入侵的早期阶段。我们发现，真菌的攻击开始与根尖的外周和表皮细胞的殖民化。这些细胞在感染后迅速丧失，而皮层细胞和中柱细胞则不会。标记的阳离子金，结合到带负电荷的壁聚合物，如果胶，是不存在的皮层细胞和感染的根的界面区，而它是丰富的中柱细胞的细胞壁。当使用抗果胶单克隆抗体JIM 5时，也发现了类似的标记模式，但使用抗木葡聚糖抗体时则没有。这表明，在感染早期，真菌可能通过水解酶的降解导致果胶的显著损失，水解酶在远离攻击部位的地方扩散和起作用。果胶损失的额外支持是通过糖分析证明，在受感染的根细胞壁中发生半乳糖醛酸含量的显著降低。此外，我们还证明了X.慈菇对真菌入侵的抑制作用是形成富含胼胝质和纤维素的细胞壁附着体。
Cocoyam (Xanthosoma sagittifolium) is an important tuber crop in most tropical zones of Africa and America. In Cameroon, its cultivation is hampered by a soil-borne fungus Pythium myriotylum which is responsible for root rot disease. The mechanism of root colonisation by the fungus has yet to be elucidated. In this study, using microscopical and immunocytochemical methods, we provide a new evidence regarding the mode of action of the fungus and we describe the reaction of the plant to the early stages of fungal invasion. We show that the fungal attack begins with the colonisation of the peripheral and epidermal cells of the root apex. These cells are rapidly lost upon infection, while cortical and stele cells are not. Labelling with the cationic gold, which binds to negatively charged wall polymers such as pectins, is absent in cortical cells and in the interfacial zone of the infected roots while it is abundant in the cell walls of stele cells. A similar pattern of labelling is also found when using the anti-pectin monoclonal antibody JIM5, but not with anti-xyloglucan antibodies. This suggests that early during infection, the fungus causes a significant loss of pectin probably via degradation by hydrolytic enzymes that diffuse and act away from the site of attack. Additional support for pectin loss is the demonstration, via sugar analysis, that a significant decrease in galacturonic acid content occurred in infected root cell walls. In addition, we demonstrate that one of the early reactions of X. sagittifolium to the fungal invasion is the formation of wall appositions that are rich in callose and cellulose.