Okinaka Y, Mimori K, Takeo K, Kitamura S, Takeuchi Y, Yamaoka N, Yoshikawa M
Department of Botany, Faculty of Science, Hokkaido University, Sapporo, Japan.
Plant Physiol. 1995 Nov;109(3):839-45. doi: 10.1104/pp.109.3.839.
The release of elicitor-active carbohydrates from fungal cell walls by beta-1,3-endoglucanase contained in host tissues has been implicated as one of the earliest processes in the interaction between soybean (Glycine max) and the fungal pathogen Phytophthora megasperma f. sp. glycinea leading to host defense responses such as phytoalexin production. The present study was conducted to evaluate the primary structure of the glucanase-released elicitor (RE). Gel-filtration chromatography of carbohydrates released from mycelial walls by purified soybean beta-1,3-endoglucanase resolved them into the four fractions (elicitor-active RE-I, -II, and -III and elicitor-inactive RE-IV). Sugar composition analysis indicated that all of the fractions were composed almost entirely of glucose. 1H- and 13C-nuclear magnetic resonance analysis indicated the presence of both beta-1,3- and beta-1,6-linkages for the elicitor-active RE-I, -II, and -III fractions and only beta-1,3 linkage for the elicitor-inactive RE-IV fraction. Methylation analysis and degradation studies employing beta-1,3-endo- and beta-1,3-exoglucanase further suggested that the basic structure of elicitor-active RE consists of beta-1,6-linked glucan backbone chains of various lengths with frequent side branches composed of beta-1,3-linked one or two glucose moieties. From these structural analyses of RE, a structural model of how RE is originally present in fungal cell walls and released by host beta-1,3-endoglucanase is also proposed.
宿主组织中含有的β-1,3-内切葡聚糖酶从真菌细胞壁释放出诱导活性碳水化合物，这被认为是大豆（Glycine max）与真菌病原体大豆疫霉（Phytophthora megasperma f. sp. glycinea）相互作用中最早的过程之一，该过程会引发宿主防御反应，如植保素的产生。本研究旨在评估葡聚糖酶释放的诱导子（RE）的一级结构。用纯化的大豆β-1,3-内切葡聚糖酶从菌丝壁释放的碳水化合物进行凝胶过滤层析，将它们分离成四个组分（诱导活性的RE-I、-II和-III以及诱导无活性的RE-IV）。糖组成分析表明，所有组分几乎完全由葡萄糖组成。1H和13C核磁共振分析表明，诱导活性的RE-I、-II和-III组分同时存在β-1,3-和β-1,6-连接，而诱导无活性的RE-IV组分仅存在β-1,3连接。甲基化分析和使用β-1,3-内切和β-1,3-外切葡聚糖酶的降解研究进一步表明，诱导活性RE的基本结构由不同长度的β-1,6-连接的葡聚糖主链组成，这些主链带有由β-1,3-连接的一个或两个葡萄糖部分组成的频繁侧链。基于对RE的这些结构分析，还提出了RE最初如何存在于真菌细胞壁中并由宿主β-1,3-内切葡聚糖酶释放的结构模型。
