Bacterial-mediated induced resistance in cucumber:: Beneficial effect of the endophytic bacterium Serratia plymuthica on the protection against infection by Pythium ultimum
Bacterial-mediated induced resistance in cucumber:: Beneficial effect of the endophytic bacterium Serratia plymuthica on the protection against infection by Pythium ultimum
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DOI：
10.1094/phyto.2000.90.1.45
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发表时间：
2000-01-01
期刊：
影响因子：
3.2
通讯作者：
Dehbi, L
中科院分区：
文献类型：
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作者：
Benhamou, N;Gagné, S;Dehbi, L
在细胞水平上探讨了内生细菌增厚沙雷氏菌RIGC4在黄瓜幼苗接种土传病原菌末毒霉（Pythium ultimum）后刺激防御反应的潜力。与未处理对照植株相比，接种前进行细菌处理的植株幼苗病害发展较少，在接种病原菌3天后就可以看到典型的根系症状。根样品的组织学调查显示，在植物防御反应的程度显著差异之间的细菌和非细菌的植物。这些观察结果在超微结构水平上得到了进一步的证实，证明真菌定植在被细菌感染的幼苗最外层根组织的限制，与潜在病原体渗透部位的增大的富含胼胝质的壁面沉积和定植区域的亲锇物质积累有关。病原体的菌丝被这种电子不透明的物质包围，表现出相当大的变化，包括细胞质的破坏，在许多情况下，原生质的丧失。然而，用β -1,4-外葡聚糖酶标记导致了对python细胞壁的规则标记，即使这些细胞壁完全被亲锇物质覆盖。这种物质也被发现渗透到入侵的菌丝中，形成细胞壁的内部涂层或在先前被细胞质占据的区域形成多形性液滴网络。细胞化学研究表明，胼胝质、果胶和纤维素出现在细胞壁上。此外，糖苷、脂质和酚类物质在构成大多数壁面排列核心的电子密集聚集体中被检测到。最后，半乳糖残基是在壁面上检测到的少量多糖化合物之一。本研究提供的证据表明，通过在潜在真菌进入的部位形成物理和化学屏障，用S. plymuthica处理敏感黄瓜植株，使其对Pythium的攻击反应更快、更有效。
The potential of the endophytic bacterium Serratia plymuthica strain RIGC4 in stimulating defense reactions in cucumber (Cucumis sativus) seedlings inoculated with the soilborne pathogen Pythium ultimum was explored at the cellular level. Bacterial treatment prior to Pythium inoculation resulted in less seedling disease development as compared with that in nontreated control plants, in which typical root symptoms were visible by 3 days after inoculation with the pathogen. Histological investigations of root samples revealed striking differences in the extent of plant defense reactions between bacterized and nonbacterized plants. These observations were further confirmed at the ultrastructural level with the demonstration that restriction of fungal colonization to the outermost root tissues of bacterized seedlings correlated with the deposition of enlarged callose-enriched wall appositions at sites of potential pathogen penetration and the accumulation of an osmiophilic material in the colonized areas. Hyphae of the pathogen, surrounded by this electron-opaque material, exhibited considerable changes including cytoplasm disorganization and, in many cases, loss of the protoplasm. However, labeling with the beta-1,4-exoglucanase resulted in a regular labeling of Pythium cell walls, even at a time when these walls were entirely coated by the osmiophilic material. This material was also found to infiltrate into the invading hyphae to form either an internal coating of the cell wall or a network of polymorphic droplets in the area previously occupied by the cytoplasm. Cytochemical investigations revealed that callose, pectin, and cellulose appeared in the wall appositions. In addition, glucosides, lipids, and phenolics were detected in the electron-dense aggregates forming the core of most wall appositions. Finally, galactose residues were among the minor polysaccharidic compounds detected in the wall appositions. Evidence is provided in this study showing that treatment with S. plymuthica sensitizes susceptible cucumber plants to react more rapidly and more efficiently to Pythium attack through the formation of physical and chemical barriers at sites of potential fungal entry.