2000 Fiscal Year Final Research Report Summary
Calcium stores in Nitella flexilis
| Project/Area Number |
11640658
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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 | Fukui University of Technology |
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Principal Investigator |
TAZAWA Masashi Fukui University of Technology, Department of Applied Physics and Chemisty, 工学部, 教授 (80028117)
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| Co-Investigator(Kenkyū-buntansha) |
KIKUYAMA Munehiro The University of the Air, General Education, 教養部, 助教授 (90131010)
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| Project Period (FY) |
1999 – 2000
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| Keywords | Ca^<2+> / Ca^<2+> store / Ca^<2+> channel / Characeae / SA channel / Mg^<2+> / chloroplast |
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| Research Abstract |
(1)In a species of Characeae, Nitella flexilis, inflow of water into the cytoplasm causes an increase in the cytoplasmic Ca^<2+> concentration. This hydration-induced Ca^<2+> increase may be caused by release of Ca^<2+> from Ca^<2+> stores in response to osmotic extension of the store membrane. A stretch-activated Ca^<2+> channel in the Ca^<2+> stores may be responsible for the hydration-induced Ca^<2+> release (HICR).
(2) Ryanodine or IP_3-seinsitive Ca^<2+> release mechanism may not be involved in HICR, since injection of these agents into the cytoplasm had no effect on HICR.
(3) In order to demonstrate the existence of mechano-sensitive Ca^<2+> release in the cytoplasm of N.flexilis, we stimulated mechanically the cytoplasmic drop isolated in vitro. One method is to shoot the cytoplsmic drop with a drop of silicon oil. The second method is to deform the cytoplsmic drop by compression and decompression. Release of Ca^<2+> from the cytoplasmic drop was detected by light emission of aequorin which was measured by photomultiplier.
(4) Mechanical deformations applied to the drop by both methods induced a rapid transient Ca^<2+> increase.
(5) The cytoplasmic drop was fractionated into the chloroplast and the chloroplast-free white fractions. Only the chloroplast fraction showed Ca^<2+> transient on stimulation.
(6) When starch grains were added to the white fraction, it responded to mechanical stimulation, indicating that the cytoplasm contains mechano-sensitive Ca^<2+> stores and also that collision of the stores with particles is essential for the mechnoresponse to occur.
(7) Cytoplasmic contents of Mg^<2+> and Ca^<2+> were measured in N.flexilis, Chara corallina and N.axilliformis. No significant difference was found in the Mg^<2+> content among them. But as for the Ca^<2+> content, N.flexilis contained 2-3 times more Ca^<2+> than the other two species. A markedly higher capacity for IIICR in N.flexilis might be explained by its higher cytoplasmic Ca^<2+> content.
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Research Products
(4 results)
