1996 Fiscal Year Final Research Report Summary
Morphological Study on the Chloroplast Division of a Chromophytic Alga, Heterosigma akashiw
| Project/Area Number |
07640880
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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 |
生物形態・構造
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| Research Institution | The University of Tokyo |
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Principal Investigator |
HASHIMOTO Haruki The University of Tokyo, Graduate School of Arts and Sciences, Associate Professor, 大学院・総合文化研究科, 助教授 (90134410)
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| Project Period (FY) |
1995 – 1996
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| Keywords | Heterosigma akashiwo / Raphidophyceae / Rapid freezing / Plastid / plastid division / Chloroplast / Chloroplast division / Plastid dividing-ring |
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| Research Abstract |
Summary. The plastokinesis (kinesis of chloroplast) of a raphidophyte alga, Heterosigma akashiwo was studied by electron microscopy using rapid freezing and freeze-substitution techniques. The chloroplasts are enveloped by two pairs of tightly appressed double membranes, the inner and the cytoplasmic outer pair. The inner pair constricts to divide in advance of the outer pair. By observation of serial sections and electron-opaque, annular structure (plastid dividing-ring) was observed at the isthmus of constricting chloroplasts, girdling the periplastidal outer surface of the inner pair of the four surrounding membranes. These observations suggest that the mechanism underlying the constriction of the inner and outer pair may differ from each other. The localization of the annular structure (plastid-dividing ring) suggests that the inner pair of the surrounding membranes may be homologous to the double envelope membranes of the chleroplasts of Chlorophyta and Rhodophyta. In addition these findings provide a new evidence supporting the secondary endosymbiosis hypothesis for the origin of the chleroplasts in chromophyte algae.
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