| Budget Amount *help |
¥3,500,000 (Direct Cost: ¥3,500,000)
Fiscal Year 1999: ¥2,200,000 (Direct Cost: ¥2,200,000)
Fiscal Year 1998: ¥1,300,000 (Direct Cost: ¥1,300,000)
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| Research Abstract |
The conidial germ tube of Magnaporthe grisea differentiates an infection specific structure, and appressorium, for penetration into the host plant. Formation of appressorium is also observed on synthetic solid substrata such as polycarbonate. We found that a plant lectin, concanavalin A, specifically suppressed the appressorium formation without affecting the germling adhesion if it was applied within 2-3 hours after germination. Standing on the result, we constructed a cDNA library which represents the early stage of germ tube development and/or appressorium formation from the 2.5 hours-old germ tuibes using a cDNA subtraction strategy by the combination of biotin labeled driver method and adapter-primed PCR method. Out of 686 colonies of the library, 158 distinct clones' nucleotide sequence were partially determined. Some clone's expression pattern was detected by RT-PCR and from those results, our library seemed to have good quality to represent the aimed stage of M. grisea.
A gene, A4, found in a DNA subtractive differential library specifically expressed during developmental stage of conidial germ tube. Gene disruption experiments were performed to reveal the function of A4 gene. Null mutants of A4 gene failed to differentiate appressorium formation on the artificial solid surface but not on the plant surface. This phenotype was recovered by cAMP and fatty alcohols. A4 gene seemed to play an important role on the recognition of physical parameters on solid surfaces or interaction with them. Interestingly, A4 codes two copies of chitin binding domain which is specific in plant's type I and IV chitinase and chitin binding plant lectins such as WGA. However, whole structure of the gene showed no similarity with those genes.
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