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

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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.