Laboratoire de Phytopathologie, Institut Français de Recherche Scientifique pour le Développement en Coopération, B.P. 5045, 34000 Montpellier, France, and Forestry Canada, Quebec Region, Sainte-Foy, Quebec GIV 4C7, Canada.
Appl Environ Microbiol. 1993 Aug;59(8):2578-88. doi: 10.1128/aem.59.8.2578-2588.1993.
An ultrastructural and cytochemical investigation of the development of Rigidoporus lignosus, a white-rot fungus inoculated into wood blocks, was carried out to gain better insight into the structure and role of the extracellular sheaths produced by this fungus during wood degradation. Fungal sheaths had a dense or loose fibrillar appearance and were differentiated from the fungal cell wall early after wood inoculation. Close association between extracellular fibrils and wood cell walls was observed at both early and advanced stages of wood alteration. Fungal sheaths were often seen deep in host cell walls, sometimes enclosing residual wood fragments. Specific gold probes were used to investigate the chemical nature of R. lignosus sheaths. While labeling of chitin, pectin, beta-1,4- and beta-1,3-glucans, beta-glucosides, galactosamine, mannose, sialic acid, RNA, fucose, and fimbrial proteins over fungal sheaths did not succeed, galactose residues and laccase (a fungal phenoloxidase) were found to be present. The positive reaction of sheaths with the PATAg test indicates that polysaccharides such as beta-1,6-glucans are important components. Our data suggest that extracellular sheaths produced by R. lignosus during host cell colonization play an important role in wood degradation. Transportation of lignin-degrading enzymes by extracellular fibrils indicates that alteration of plant polymers may occur within fungal sheaths. It is also proposed that R. lignosus sheaths may be involved in recognition mechanisms in fungal cell-wood surface interactions.
为了更深入地了解 Rigidoporus lignosus（一种白腐真菌）在木质素降解过程中产生的胞外鞘的结构和功能，我们对其进行了超微结构和细胞化学研究。该真菌的胞外鞘呈密集或疏松的纤维状，在木质素接种后早期与真菌细胞壁区分开来。在木质素改变的早期和晚期阶段，都观察到了胞外纤维与木质素细胞壁之间的密切联系。胞外鞘经常在宿主细胞壁深处出现，有时包围残余的木质素碎片。我们使用特定的金探针来研究 R. lignosus 胞外鞘的化学性质。虽然未能成功标记几丁质、果胶、β-1,4-和β-1,3-葡聚糖、β-葡萄糖苷、半乳糖胺、甘露糖、唾液酸、RNA、岩藻糖和菌毛蛋白，但发现存在半乳糖残基和漆酶（一种真菌酚氧化酶）。胞外鞘与 PATAg 测试的阳性反应表明，β-1,6-葡聚糖等多糖是重要成分。我们的数据表明，R. lignosus 在宿主细胞定殖过程中产生的胞外鞘在木质素降解中发挥重要作用。胞外纤维运输木质素降解酶表明，植物聚合物的改变可能发生在真菌胞外鞘内。此外，还提出 R. lignosus 胞外鞘可能参与真菌细胞与木质素表面相互作用中的识别机制。
