| Project/Area Number |
09460037
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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 The University of Tokyo, Graduate School of Agricultural and Life Science, 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 The University of Tokyo, Graduate School of Agricultural and Life Science, Assis, 大学院・農学生命科学研究科, 助手 (80282698)
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| Project Period (FY) |
1997 – 1998
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| Project Status |
Completed (Fiscal Year 1998)
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| Budget Amount *help |
¥11,500,000 (Direct Cost: ¥11,500,000)
Fiscal Year 1998: ¥2,500,000 (Direct Cost: ¥2,500,000)
Fiscal Year 1997: ¥9,000,000 (Direct Cost: ¥9,000,000)
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| Keywords | Iron Deficiency / Graminaceous Plant / Barley / Mugineic Acids Family Phytosiderophores / Immunocytochemistry / Nicotianamine / Nicotianamine Synthase / Nicotianamine aminotransferase / 鉄欠乏耐性 / 植物の鉄栄養 / 細胞化学 / ムギネ酸 / イネ / 形質転換植物 / Ids3 |
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| Research Abstract |
Under iron deficient conditions, graminaceous plants secrete iron chelators called mugineic acid family phytosiderophores (MAs) to dissolve sparingly soluble iron compounds in the soil. The secretion of MAs follows a distinct diurnal rhythm. A secretion peak occurs just after the initial illumination and the secretion ceased in the afternoon. In contrast, MAs is produced continuously during 24 hours. MAs might be stored somewhere in the roots until the beginning of secretion. Previously we found that the particular vesicles were present in barley root cells. They assumed to be originated from r-ER.The volume of these vesicles was expanded especially before sunrise when MAs were enriched in iron deficient barley roots. Therefore, we hypothesized that MAs is produced and stored in these particular vesicles.
Recently we have identified several genes involved in biosynthesis of MAs. Three molecules of S-adenosyl methionine are combined to form nicotianamine (NA) catalyzed by nicotianamine synthase (NAS), which is then converted to deoxymugineic acid (DMA) by amino-group transfer and then subsequent reduction at the 3"-carbon. Aminotransfer of NA is catalyzed by nicotianamine aminotransferase (NAAT). Seven cDNA clones of nas and two cDNA clones of naat were isolated.
In this study, dynamics and the localization of these two crucial enzymes in MAs biosynthesis, NAS and NAAT, were investigated by using transient expression system of GFP-fusion protein and immunocytochemistry. As a result, it is demonstrated that both NAS and NAAT were targeted to the above mentioned particular vesicles. NAS localizes on the limiting membrane of the vesicles and NAAT is present within the vesicles. This localization is consistent with the fact that predicted amino acid sequence of NAS has a transmembrane domain and NAAT has a signal peptide at the N-terminal. Therefore, we conclude that the particular vesicles appeared in iron deficient barley root cells are site of MAs production.
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