Mendgen Kurt, Deising Holger
Universität Konstanz, Fakultät für Biologie, Lehrstuhl für Phytopathologie, Universitätsstr. 10, D-78434 Konstanz, Federal Republic of Germany.
New Phytol. 1993 Jun;124(2):193-213. doi: 10.1111/j.1469-8137.1993.tb03809.x.
Many fungi differentiate specific infection structures in order to infect the host plant. The spore attaches to the host surface, the cuticle, and the germ tube may recognize suitable penetration sites, over which an appressorium is formed. Additional wall layers in appressoria of many fungi suggest that this structure supports increasing pressure during the penetration process. During appressorium formation, synthesis of polymer-degrading enzymes is often initiated. Cutinases, cellulases and pectin-degrading enzymes can be formed in a developmentally controlled or adaptive, i.e. substrate-dependent, fashion. The penetration hypha develops below the appressorium. This hypha has a new wall structure and exhibits features which serve to breach the plant cell wall. However, at present it is not clear whether penetration hyphae arising from appressoria are more efficient in penetration or induce less damage than hyphae which penetrate without detectable special adaptations. The infection hypha differentiates within the host. During differentiation a characteristic set of enzymes is synthesized to enable successful establishment of the host-pathogen relationship. If, as in most cases, multiple forms of cell wall-degrading enzymes are formed by the pathogen, mutagenesis or deletion of a gene encoding one of these enzymes very often has no effect on pathogenicity or even virulence. Proof is missing very often that an enzyme is needed at the right time and at the right site of infection. Events occurring during differentiation of fungal infection structures are reviewed with special emphasis on Magnaporthe grisea, Colletotrichum spp., and rust fungi, and common features which may be of importance to the success of infection are discussed. CONTENTS Summary 193 I. Introduction 193 II. Spore and germ tube 195 III. The appressorium 199 IV. The penetration hypha 201 V. The infection hypha 204 VI. Future prospects 208 Acknowledgements 208 References 208.
许多真菌会分化出特定的感染结构以侵染寄主植物。孢子附着在寄主表面即角质层上，芽管可能识别合适的穿透位点，在该位点上形成附着胞。许多真菌的附着胞中有额外的壁层，这表明该结构在穿透过程中有助于增加压力。在附着胞形成过程中，通常会启动聚合物降解酶的合成。角质酶、纤维素酶和果胶降解酶可以以发育控制或适应性（即依赖底物）的方式形成。穿透菌丝在附着胞下方发育。这种菌丝具有新的壁结构，并呈现出有助于突破植物细胞壁的特征。然而，目前尚不清楚由附着胞产生的穿透菌丝在穿透方面是否比没有明显特殊适应性的穿透菌丝更有效或造成的损害更小。侵染菌丝在寄主体内分化。在分化过程中会合成一组特定的酶，以成功建立寄主 - 病原体关系。在大多数情况下，如果病原体形成多种形式的细胞壁降解酶，对其中一种酶的编码基因进行诱变或缺失通常对致病性甚至毒力没有影响。通常缺乏证据表明在感染的正确时间和正确部位需要某种酶。本文综述了真菌感染结构分化过程中发生的事件，特别强调了稻瘟病菌、炭疽菌属和锈菌，并讨论了可能对感染成功至关重要的共同特征。目录摘要193 一、引言193 二、孢子和芽管195 三、附着胞199 四、穿透菌丝201 五、侵染菌丝204 六、未来展望208 致谢208 参考文献208 。
