Cytological and Molecular Biological Analyses of Mechanisms of Signal Recognition and Host Specificity at Incipient Infection Stage

已知白粉病分生孢子在接触疏水膜后立即释放胞外物质（ECM）。在本研究中，证实了大麦白粉病菌和小麦白粉病菌、豌豆白粉病菌在宿主表面释放ECM。ECM有助于分生孢子的粘附和芽管萌发位置的确定。免疫电子显微镜和共聚焦显微镜显示，材料从分生孢子转移到宿主表皮，反之亦然，通过ECM分生孢子接触后30分钟内。大麦的表皮细胞接触B. g. trivaniae和E.pisi（两者都是大麦的非病原体）的ECM在分生孢子接触后6-7 h内被导向不可接近性，而那些接触B. g. hordei（大麦的病原体）的ECM的大麦的表皮细胞被导向既不可接近性也不不可接近性。这些结果表明，信号转导和宿主反应后立即启动分生孢子-宿主细胞接触。燕麦食酸菌在单子叶植物中的寄主范围很广，但个别菌株只能侵染一种或几种寄主。最近我们报道了麦长管蚜的不亲和菌株引起了抗性反应，而亲和菌株则没有。我们还报道了不亲和菌株的鞭毛蛋白诱导的抗性反应。为了研究水稻在不亲和系诱导下的防御反应机制以及鞭毛蛋白在这种防御反应中的作用，利用水稻cDNA微阵列技术进行了分析。基因芯片分析表明，25个基因的诱导是由不相容的鞭毛知觉。我们还研究了不相容和相容鞭毛蛋白之间抗性反应的诱导特异性。利用纯化的鞭毛蛋白和重组鞭毛蛋白在水稻细胞中诱导抗性反应的分析表明，鞭毛蛋白的翻译后修饰涉及鞭毛蛋白的特异性。

Powdery mildew conidia were known to release extracellular materials (ECM)immediately after contact to hydrophobic membranes. In this study, Blumeria graminis hordei and B.g.tritici, Erysiphe pisi were confirmed to release ECM on host surfaces. ECM contributes to adhesion of conidia and determination of the emergence site of germtubes. Immuno electron and confocal microscopies revealed that materials were moved from conidia to host epidermis and vice versa via ECM within 30 min after conidial contact. Epidermal cells of barley that contacted ECM of B.g.tritici and E.pisi (both nonpathogens to barley) were directed towards inaccessibility within 6-7 h after conidial contact, while those that contacted ECM of B.g.hordei (pathogen to barley) were directed towards neither accessibility nor inaccessibility. These results show that signal transduction and host response initiate immediately after conidium-host cell contact. The host range of Acidovorax avenae is wide among monocotyledonous but individual strains can infect only one or a few host species. Recently we reported that incompatible strain of A.avenae caused the resistance response, but compatible strain did not. We also reported that the resistance response was induced by flagellin from the incompatible strain. To investigate the mechanism of rice defense response induced by the incompatible strain and the role of flagellin on this defense induction, rice cDNA microarray analysis was performed. The microarray analysis showed that induction of 25 genes was regulated by the incompatible flagellin perception. We also investigated induction specificity of resistant response between incompatible and compatible flagellins. Induction analysis of resistant response in cultured rice cells using purified flagellins and recombinant flagellins showed that the flagellin specificity is involved in the post-translational modification of flgaellins.