| Project/Area Number | 10640630 |
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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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 | Osaka University |
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Principal Investigator |
HASE Toshiharu Osaka University, Institute for Protein Research, Professor, たんぱく質研究所, 教授 (00127276)
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| Co-Investigator(Kenkyū-buntansha) |
ARIGA Yoko Osaka University, Institute for Protein Research, Instructor, たんぱく質研究所, 助手 (60255429)
FUJITA Yuichi Osaka University, Institute for Protein Research, Instructor, たんぱく質研究所, 助手 (80222264)
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| Project Period (FY) |
1998 – 2000
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| Project Status |
Completed(Fiscal Year 2000)
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| Budget Amount *help |
¥3,500,000 (Direct Cost : ¥3,500,000)
Fiscal Year 2000 : ¥700,000 (Direct Cost : ¥700,000)
Fiscal Year 1999 : ¥700,000 (Direct Cost : ¥700,000)
Fiscal Year 1998 : ¥2,100,000 (Direct Cost : ¥2,100,000)
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| Keywords | Carbon assimilation / Nitrogen assimilation / Ferredoxin / Glutamate Synthase / Ferredoxin-NADP^+ reductase / Electron transfer complex / フェレドキシンNADP^+還元酵素 / 炭酸固定 / シアノバクテリア / ラン藻 / 炭素同化 |
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| Research Abstract |
Assimilation of carbon and nitrogen in photosynthetic organisms is dependent on the supply of reductant and ATP and the regulation of the metabolic cross-talk of these metabolic processes is crucial for cell growth. This project focused on enzymes involved in glutamate synthesis, which is the first product of C and N assimilation, and reductant supply system for catalysis. Following results have been obtained.
1. Genes for Fd- and NADPH-dependent glutamate synthase were cloned from the cyanobacteria Plectonema boryanum. Mutants deficient of each gene is viable, but only the strain lacking Fddependent enzyme is suffered from nitrogen deficiency under an efficient carbon assimilation condition. In this strain, change of cellular amino acid pool, decrease in the transcript level of phycobiliporoteins and efficient reduction from nitrate to ammonia were observed in response to the nitrogen deficiency.
2. Mesophyll and bundle sheath cells of maize leaves, which are differentiated in C and N assimilation, possess unique ferredoxin isoproteins (FdI and FdII, respectively). Using cyanobacterial cells whose endogenous Fd gene was replaced by each maize Fd gene, it was found that FdI functions predominantly as an electron carrier for the non-cyclic photosynthetic electron transfer and that FdII was superior in the cyclic electron transfer, resulting in a weak electron donation to the N-assimilation pathway. These results suggest that Fd is a key molecule for the coordination of C and N assimilation.
3.X-ray crystal structure of the complex between Fd and Fd-NADP+ reductase has been determined. Structural information on topology of the prosthetic groups and interaction of the two proteins are obtained. To obtain structural basis of the cross-talk of C, N and S assimilation, this study will be extended to investigate molecular designs of Fd for interaction with GOGAT and other S assimilatory redox enzymes.
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