Studies on morphogenesis of infection structure and its responses to environment in plant pathogenic fungi

1)本研究以菜豆炭疽菌（Colletotrichum leganarium）为材料，构建了菜豆炭疽菌（Colletotrichum leganarium）的cDNA文库。通过对文库的差异筛选，分离到4个在种子萌发和附着胞形成过程中优先表达的基因。对环境和附着胞分化的响应本研究发现，植物叶片表面的物质可以诱导西瓜炭疽菌在寄主植物上的萌发，这种诱导作用可能是通过cAMP依赖的蛋白激酶信号转导途径来实现的。克隆了一个MAP激酶基因，并通过基因破坏实验分析了该基因的功能。由此可见，MAP激酶途径参与了寄主植物的萌发、附着胞形成和入侵生长。此外，还分离并鉴定了一个参与黑色素生物合成基因表达的转录因子。该转录因子以发育依赖的方式正向调节两个结构性黑色素生物合成基因。此外，该转录因子显示出非常独特的结构，包含两种不同类型的DNA结合基序。这是在真核生物中首次发现转录因子。

1) Isolation and characterization of genes that specifically expressed at appressorium differentiation.In this research, an equalized cDNA library of Colletotrichum leganarium was constructed. By differential screening of this library, 4 genes that preferentially expressed at germination and appressorium formation were isolated. Those genes were characterized by sequencing and expression analysis during appressorium differentiation.Responses to environment and appressorium differentiationIn this research, it became evident that a plant leaf surface substance(s) induces germination of Colletotrichum lagenarium on host plant and this induction was seems to be mediated by cAMP dependent protein kinase signal transduction pathway. A MAP kinase gene was cloned and function of this gene was analyzed by gene disruption experiment. From this, it became evident that a MAP kinase pathway is involved in germination, appressorium formation and invasive growth in host plant. Furthermore, a transcription factor that involved in expression of melanin biosynthesis genes was isolated and characterized. This transcription factor positively regulated two structural melanin biosynthesis genes in a development dependent manner. Also this transcription factor showed very unique structure that contains two different type of DNA binding motifs. This was a first finding of transcription factor among eukaryotic organism.