2003 Fiscal Year Final Research Report Summary
Studies on low oxygen sensitivity mechanism of CAM photosynthesis
| Project/Area Number |
12460011
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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 |
作物学
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| Research Institution | Saga University |
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Principal Investigator |
NOSE Akihiko Saga University, Faculty of Agriculture, Professor, 農学部, 教授 (80045137)
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| Project Period (FY) |
2000 – 2003
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| Keywords | CAM photosynthesis / low oxygen / pineapple / mitochondria / malate / OAA shuttle / cyanide resistant respiration / PEP carboxykinase / decarboxylation |
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| Research Abstract |
The phenomenon in which the depression of CO2 exchange in CAM photosynthesis (phase 3) disappeared under low oxygen conditions, could not be related to CAM subtype of CO2 decarboxylation, that is, PEP carboxykinase (PCK) type and malic enzyme (ME) type. For the oxygen concentration in which the phase 3 of CAM disappears, it has been indicated that cyanide resistant respiration of mitochondria is concerned in low oxygen sensitivity of CAM photosynthesis. However the low oxygen sensitivity of CAM photosynthesis could not be explained simply with cyanide resistant respiration. In the pineapple mitochondria purified with Percoll density method, malic acid was incorporated actively into, the mitochondria only under the condition in which malate/OAA shuttle of the inner membrane functioned. This result indicates that the of malate in the phase 3 dose not operate in the pineapple mitochondria. In addtion, it is suggested that the conversion of malate to OAA in the pineapple mitochondria matrix functions as a replenishment system to supply the OAA as the substrate to the decarboxylation using PCK in the pineapple CAM phase 3. In other words, it is suggestedd that the low oxygen sensitivity of CAM photosynthesis appear only under the condition where the malate in CAM phase 3 is decarboxylated actively by NAD-ME in mitochondria and the NADH produced by the decarboxylation is oxidized with the cyanide resistant respiration.
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