Molecular Mechanism of Signal Transfer at Plant-Parasite Interfaces.

本研究旨在从细胞学和生理学的角度对植物与病原菌相互作用进行分子生物学研究。利用大麦胚芽鞘在细胞水平上进行的细胞学研究表明，寄主细胞在病原体侵入之前就已经识别出病原体的存在，寄主细胞中的细胞骨架可能参与了这种识别机制。稻瘟病菌毒素可引起水稻细胞电解质的渗漏。赤星菌ACT毒素的分子结构与AK和AF毒素相似。这些结果表明，宿主特异性毒素可能作为触发病原体致病性的信号发挥作用。豌豆褐斑病菌释放的一种抑制因子能特异性地抑制寄主细胞质膜上的ATP酶，从而成功地延缓了寄主防御反应的表达。马铃薯-晚疫病菌系统的生理分析表明，Ca^++， 关于我们 O2 ^-和蛋白激酶可能与诱导寄主防御反应有关。这些结果与其它有关木质素形成和过氧化脂质检测的研究一起，促进了我们对植物抗性机制某些方面的理解。单基因分析表明，燕麦冠锈病抗性基因与胜利灵感病基因紧密连锁。本研究建立了梨褐斑病菌的基因操作技术和大麦胚芽鞘的显微注射转化技术。在大豆-大豆疫霉系统中，成功克隆了一个与菜豆抗病反应有关的激发子基因的cDNA。转基因烟草植株对该菌的抗性明显增强。此外，从甜瓜叶片感染农杆菌生根预先通过导入CMV抗性基因转化再生抗CMV甜瓜植株。所有这些结果大大增强了我们对寄生-宿主界面事件的认识。少

The present study aimed the molecular biological investigation of the plant-pathogen interactions on the basis of cytological and physiological analyses. The cytological studies using barley coleoptiles at cellular level revealed that host cells recognized the presence of a pathogen prior to its penetration and that cytoskeleton in host cells might be involved in this recognition mechanism. The toxin of the rice blast fungus was proved to cause the leakage of electrolytes from rice cells. The molecular structure of ACT toxin of tangerine brown spot fungus was similar to that of AK and AF toxins. These results suggest that host-specific toxins might play a role as a signal for triggering pathogenicity of the pathogen. A suppressor released from the pea brown spot fungus was shown to inhibit ATPase of host plasma membranes specificaly, and thus successfully delay the expression of host defense reaction. Physiological analyses of potato-Phytophthora infestans system revealed that Ca^<++>, … More O_<2^-> and protein kinase might be related to induction of host defense responses. Together with other studies concerning lignin formation and detection of peroxidated lipids, all these results promoted our understanding of some aspects of the resistance mechanism of plants. A separate gene analyses indicated that resistant genes of avena for crown rust was closely linked with susceptible genes of victorin. Several molecular biological techniques were established during the present study : the gene manipulation technique of the pear brown spot fungus and the transformation technique for barley coleoptiles using a microinjection method. In the soybean-Phytophthora megasperma system, cDNA of an elicitor gene responsible for a resistant response of bean was successfully cloned. The resistance to this fungus was evidently enhanced in tobacco plants which had been transformed by introduction of this gene. Moreover, CMV-resistant melon plants were regenerated from melon leaves infected with Agrobacterium rhizogenesis previously transformed by introduction of CMV-resistant gene. All these results greatly enhanced our knowledges on the events occurring at the parasite-host interfaces. Less