Signal transduction and cellular responses in plant infection

在本次合作研究项目中，我们在分子和细胞水平上深入研究了寄主细胞对真菌病原菌释放的信号因子的识别，取得了许多有益的结果如下：1.从烟草赤霉病、丹西橘赤霉病、大葱灰霉病和稻瘟菌的孢子萌发液中分别分离得到了病原菌的信号因子及其生物发生机制：AT-毒素、ACT-毒素A、寄主识别因子和侵染诱导因子。其中，来自灰色霉菌的因子在诱导可及性而不会导致宿主细胞坏死方面是非常独特的。在链格孢菌生物合成AK-毒素和AF-毒素的过程中，发现一种环氧基结合的十碳三烯酸醇是主要的中间代谢产物。互作梨…基因组文库及高效转化体系的建立为了鉴定和分离致病基因，建立了更多的致病类型。在宿主细胞的质膜上检测到信号毒素受体。克隆了1，3-内切葡聚糖酶基因，并测定了其碱基序列。II.信号转导及其调控：AM-毒素诱导的苹果叶片坏死过程中含有光抑制阶段，需要3小时的暗期才能完成。来自真菌的抑制物拮抗激发子诱导的豌豆组织中植物保卫素的合成。超氧物产生系统和磷脂酶的激活与马铃薯的超敏细胞反应有关。III.细胞对信号的反应：对寄主中主要靶标明显不同的毒素的早期作用过程与可及性诱导之间的关系的研究表明，质膜上的功能修饰与诱导密切相关；即使是移栽植物的感染也不需要坏死。因此，膜病理学将成为研究感染机制的重要靶点。较少

In the present co-operative research program, we investigated in-depth the recognition by host cells of signal factors released from fungal pathogens at the molecular and cellular levels, and obtained many useful results as follows;I. Isolation and characterization of pathogen's signal factors, and their biogenetic mechanisms: AT-toxin, ACT-toxin A, a host-recognition factor and an infection-inducing factor were isolated respectively from spore-germinated fluids of the brown spot pathogen of tobacco, the brown spot pathogen of Dancy tangerine, the gray mold of scallion and the rice blast fungus. Of them, the factor from the gray mold was very unique in respect to an ability to induce accessibility without causing necrosis in host cells. An epoxyradical-attached decatrienoic acid alcohol was found to be a major intermediate metabolite in the biosynthesis of AK-toxin and AF-toxin by Alternaria pathogens. Genomic library and an efficient transformation system of A. alternata Japanese pear … More pathotype were established to identify and isolate the pathogenicity gene. Receptors for signal toxins were detected in the plasma membrane of host cells. Gene for -1,3-endoglucanase that releases a phytoalexin-elicitor from Phytophthora's cell wall was cloned and its base sequence was completely determined.II. Signal transduction and its regulation: Necrotic process in apple leaves caused by AM-toxin was found to contain a photo-inhibition phase; 3hr-dark period was necessary to complete the necrosis. A suppressor from Mycospherella antagonized the elicitor-inducing phytoalexin synthesis in pea tissues. superoxideproducing system and phospholipase activation related to hypersensitive cell reaction in potato.III. Cellular responses to signals: Investigation of the relation between early action process of toxins whose primary targets in hosts are distinctly different and accessibility induction revealed that functional modification in plasma membranes was very colsely correlated to the induction; no necrosis was required for infection even by perthophytes. In conclusion, membrane pathology will be the key target for study of infection mechnism. Less