| Budget Amount *help |
¥3,710,000 (Direct Cost: ¥3,500,000、Indirect Cost: ¥210,000)
Fiscal Year 2007: ¥910,000 (Direct Cost: ¥700,000、Indirect Cost: ¥210,000)
Fiscal Year 2006: ¥1,000,000 (Direct Cost: ¥1,000,000)
Fiscal Year 2005: ¥1,800,000 (Direct Cost: ¥1,800,000)
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| Research Abstract |
The metabolic fates of secondary metabolites were investigated in gramineous plants, oats, and a model plant Arabidopsis thaliana.
In oats, it has been demonstrated that their phytoalesxins, avenanthramides, are incorporated into cell walls. lb know the incorporation processes in detail, the metabolites that are derived from avenanthramides were investigated. The avenanthramide metabolites that are genrerated by the action of peroxidase were found to be present in oat leaves. The analysis of their chemical structures revealed that they are dehydrodimers of avenanthramides. The spectroscopic analysis revealed that they have unique carbon skeletons that have not been found in natural products. These compounds are considered to be units for the incorporation of avenanthramides into cell walls.
In Arabidopsis thaliana, indole-3-carboxylic acid (ICA) has been indicated to bound to the cell walls. We found that the amount of ICA increases in the leaves infected by A. brassicicola. The biosynthetic pathway of ICA was analyzed by using stable isotope labeled putative precursors and mutants that exhibit modified tryptophan metabolism. First, Arabidopsis leaves were fed with labeled tryptophan and the conidia of A. brassicicola were inoculated. The leaves were extracted with methanol and the incorporation of tryptophan into ICA was analyzed by LC-MS/MS. The labeled tryptophan was effectively incorporated into ICA, indicating de novo synthesis of ICA in the infected leaves. Next, we analyzed ICA contents in multiple lines that have altered tryptophan metabolism. The increase of the amount of ICA in the cell walls was found in pad 3 mutant line. pad 3 line larks the accumulation of indolic phytoalexin, camalexin. Thus, this finding strongly suggests that ICA is not directly derived from camalexin, and that the biosynthetic pathway of ICA is shared by the pathway for camalexin.
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