| Project/Area Number |
12460030
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Plant nutrition/Soil science
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| Research Institution | The University of Tokyo |
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Principal Investigator |
NISHIZAWA Naoko Graduate School of Agriculture and Life Sciences, The University of Tokyo, Professor, 大学院・農学生命科学研究科, 教授 (70156066)
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| Co-Investigator(Kenkyū-buntansha) |
NAKANISHI Hiromi Graduate School of Agriculture and Life Sciences, The University of Tokyo, Assistant, 大学院・農学生命科学研究科, 助手 (80282698)
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| Project Period (FY) |
2000 – 2001
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| Project Status |
Completed (Fiscal Year 2001)
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| Budget Amount *help |
¥12,900,000 (Direct Cost: ¥12,900,000)
Fiscal Year 2001: ¥4,900,000 (Direct Cost: ¥4,900,000)
Fiscal Year 2000: ¥8,000,000 (Direct Cost: ¥8,000,000)
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| Keywords | Iron deficiency / Graminaceous plants / Barley / Mugineic acid family phytosiderophores / Deoxymugineic acid synthase / Aldo-keto reductase / Iron chelator / Biosynthetic pathway of mugineic acid family phytosiderophores / アルドーケト還元酵素 / ケト体還元酵素 / トランスポーター |
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| Research Abstract |
Graminaceous plants secrete mugineic acid family phytosiderophores (MAs) from their roots to acquire Fe. The production and the secretion of MAs are markedly increased in response to Fe-deficiency. MAs are synthesized from L-methionine. Methionine is converted to S-adenosylmetionine (SAM) by SAM synthetase. Three molecules of SAM are combined into one molecule of nicotianamine (NA) by NA synthase (NAS) and an amino group of NA is transferred by NA aminotransferase (NAAT) to form a 2'-keto intermediate, which is subsequently reduced to 2'-deoxymugineic acid (DMA), the initial member of the MAs. We isolated the genes for SAM synthetase, NAS and NAAT from barley, rice and maize. However, genes for the reductase catalyzing the conversion of keto-form to DMA had not been isolated in this biosynthetic pathway. Therefore, we attempted to isolate the gene encoding this enzyme. Since the enzyme is a NAD(P)H-dependent reductase, we assumed that the enzyme might be a member of an aldo-keto reductase superfamily. Based on the protein sequences highly conserved in this family, we designed degenerate primers for PCR and obtained three PCR products. Northern blot analysis using these PCR fragments showed that the expression of one fragment was induced by Fe-deficiency in barley roots. We used this 500 bp fragment for the probe to screen cDNA library prepared from Fe-deficient barley roots and obtained two cDNA clones. Northern blot analysis showed that the expression of both cDNAs was induced in response to Fe-deficiency and suppressed by Fe supply. The protein products of these cDNAs showed the enzyme activity to convert keto-form to DMA. Thus, we could isolate the two genes for DMA synthase from barley. As a result, we have isolated the genes for all the enzymes participated in the biosynthetic pathway of MAs.
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