| Project/Area Number |
10440243
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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 |
植物生理
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| Research Institution | Fukuyama University |
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Principal Investigator |
ASADA Kozi Fukuyama Univ., Department of Biotechnology, Professor, 工学部, 教授 (50027182)
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| Co-Investigator(Kenkyū-buntansha) |
HARAGUCHI Hiroyuki Fukuyama Univ., Depertment of Biotechnology, Lecturer, 工学部, 講師 (10198905)
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| Project Period (FY) |
1998 – 1999
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| Project Status |
Completed (Fiscal Year 1999)
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| Budget Amount *help |
¥12,800,000 (Direct Cost: ¥12,800,000)
Fiscal Year 1999: ¥3,400,000 (Direct Cost: ¥3,400,000)
Fiscal Year 1998: ¥9,400,000 (Direct Cost: ¥9,400,000)
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| Keywords | Active oxygen / Chloroplasts / Cyclic electron transport / Flavodehydrogenase / Monodehydroascorbate reductase / NAD(P)H dehydrogenase / Superoxide radical / Water-water cycle / NAD(p)Hデヒドロゲナーゼ / 光酸素障害 / 光合成 / スーパーオキシドジスムターゼ / Water-Waterサイクル |
|---|
| Research Abstract |
When plant leaves are exposed to sunlight in excess of its utilizing capacity for coィイD22ィエD2-fixation, the excess photons produce active oxygens and cause the photoinhibition of photosynthesis. The superoxide and hydrogen peroxide photogenerated in photosystem I (PSI) are effectively scavenged, and their interactions with the stromal enzymes, PSI complex and the scavenging enzyme are suppressed. The term of water-water cycle is proposed for this scavenging system, and its molecular mechanism and physiological functions are overviewed. The water-water cycle can dissipate the excess photon energy in addition to the scavenging of active oxygens, and its high flux rate is accounted for by the FAD enzyme monodehydroascorbate reductase-catalyzed photoreduction of OィイD22ィエD2 in chloroplasts.
Stress by the excess photon in chloroplasts is relaxed also by the cyclic electron flow around PSI. Participation of NAD(P)H dehydrogenase (NDH) complex as an electron-mediator between PSI and the intersystem plastoquinone is shown, and the molecular properties of NDH from cyanobacteria and chloroplasts are revealed. NDH-less transformant of tobacco shows a low cycle electron flow and is damaged the stress of excess photons.
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