2000 Fiscal Year Final Research Report Summary
Evolution of cyanelles deduced from constituents of cyenelle envelopes of a glaucocystophyte, Cyanophora paradoxa
| Project/Area Number |
11640655
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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 | Himeji Institute of Technology |
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Principal Investigator |
KOIKE Hiroyuki Himeji Inst.Tech.Life Science, Associate Prof., 理学部, 助教授 (60201480)
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| Co-Investigator(Kenkyū-buntansha) |
KASHINO Yasuhiro Himeji Insti.Tech.Life Science, Research Associate, 理学部, 助手 (20221872)
SATOH Kazuhijko Himeji Inst.Tech.Life Science, Professor, 理学部, 教授 (00090522)
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| Project Period (FY) |
1999 – 2000
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| Keywords | Glaucocystophyte / cyanelle / envelope / chloroplast / evolution / cyanobacteria |
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| Research Abstract |
Cyanophora paradoxa posseses a special organelle, a cyanelle, which performs oxygenic photosynthesis. Chloroplasts of eukaryotic photosynthetic organisms are hypothesized to be established by endosymbiosis by a progenitor of cyanobacteria. Investigation of plastid envelope of cyanelles of C.paradoxa will provide some crue to elucidate the evolutionary processes of plastids from endosymbiotic cyanobacteria, sice cyanelles stil preserve some characteristics common to cyanobacteria. In the present research project, we have isolated and characterized envelope membranes from C.paradoxa cyanelles and compared characteristics with those of cyanobacteria and plant chloroplasts.
Isolated intact cyanelles were treated with lysozyme and raptured by French Pressure cell treatment. Envelope membranes were purified from the homogenate by sucrose gradient floatation centrifugation. Two yellow fractions were separated. One fraction has a buoyant density of 1.12 g/cm^3 and rich in zeaxanthin. This corresponded to inner envelope membranes. Another fraction with a buoyant density of <1.00 g/cm^3 was rich in β-carotene. This fraction however, did not show membranous structures by observation with electron microscopy. It was concluded that the fraction does not contain envelope membanes.
A yellow fraction was found to be remained after detergent treatment of thylakoid membranes. This was rich in zeaxanthin with an estimated buoyant density of 1.18 g/cm^3, and thus estimated to be an outer envelope membranes.
The outer envelope membranes have an affinity to that of outer envelope membranes in protein composition, while to that of cyanobacteria in buoyant density and insolubility to detergent. On ther other hand, the protein composition of inner envelope membranes was similar to that of plasma membranes of cyanobactria. The results indicate that the envelope membranes have chimeric nature between cyanobacteria and plants.
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Research Products
(2 results)
