Molecular Mechanisms of Resistance Gene Expression in the Crown Rust of Oats

本研究旨在阐明燕麦病害发生与冠锈病相互作用的识别和信号转导的分子机制。特别涉及(1)活性氧释放的作用，(2)在抗性表达过程中被激活的基因的克隆，如作为PR蛋白的几丁质酶和与植物抗毒素产生和信号转导有关的基因。结果发现，活性氧的进化对于植物抗毒素基因的启动是必不可少的。受感染影响的细胞和激发子对检测到包括活性氧在内的自由基的染色呈阳性反应。活性氧可能作为第二信使诱导抗性，诱导PR蛋白、植物保卫素等基因的激活。几丁质酶的诱导与抗性表达是平行的。对酶进行了纯化，测定了N端氨基酸序列，并克隆了几丁质酶编码基因。此外，还发现几丁质酶能释放具有激发子活性的壳寡糖。最后，发现DNA梯状条带是典型的细胞凋亡症状，与锈菌小种和激发子处理的燕麦细胞的抗性反应有关。证实了细胞凋亡与防御反应之间的关系。

The purpose of this research project is to elucidate the molecular mechanisms of recognition and signal transduction which regulate disease occurence in oats and crown rust interactions. Special reference was concerned with (1) a role of release of activated oxygen, (2) cloning of genes activated during resistance expression, such as chitinase as PR protein and genes responsible to phytoalexin production and signal transduction. As a result, it was found that evolvement of activated oxygen is absolutely required for initiation of genes for phytoalexin production. The cells affected by infection as well as elicitors reacted positively to stains which detect free radicals including activated oxygen. Activated oxygen could be important for induction of resistance as a secondary messengers and induce gene activation for PR protein, phytoalexin and so on. Chitinase was induced in parallel with resistance expression. The enzymes were purified and N-teminal sequence of amino acid was determined and the genes encoded with chitinase have been cloned. In addition, it was found that the chitinases can release chito-oligosaccharides active as elicitor. Finally, it was found that DNA-laddering as a typical symptom of apoptosis was detected in association of resistance response in oat cells treated with rust races and elicitors. Relationships between apoptosis and defense response was confirmed.