Intracellular Mobilization of Ca^ and Inhibition of Cytoplasmic Streaming Induced by Transcellular Osmosis in Internodal Cells of Nitella flexilis : MEMBARANES AND BIOENERGETICS : STRUCTURE AND FUNCTION OF CELLS

元データ 日本植物生理学会


When transcellular osmosis was induced in internodal cells of Nitella flexilis that had been rendered inexcitable by treatment with KCl or EGTA, the rate of cytoplasmic streaming was reduced and the membrane was depolarized. In both KCl^- and EGTA-treated cells, the endoosmosis induced a significant increase in the concentration of Ca^<2+> in the cytoplasm, which was demonstrated by monitoring the emission of light from aequorin that had been injected into the cytoplasm. When transcellular osmosis was induced in tonoplast-free cells, in which the intracellular Ca^<2+> concentration had been stabilized at a very low level by treatment with the Ca^<2+>-chelating agent EGTA, no change in the rate of cytoplasmic streaming on the endoosmosis side was observed . Hydration of the cytoplasm in the absence of endoosmosis was induced by direct introduction of a hypotonic medium into the vacuole by intracellular perfusion. The results mimicked the inhibition of streaming induced by transcellular osmosis. During transcellular osmosis, chloroplasts on the endoosmosis side swelled as a result of dilution of the cell sap. Swelling of chloroplasts was demonstrated to be unrelated to the inhibition of streaming, since streaming was retarded at sites from which chloroplasts had been removed. It is suggested that hydration of the cytoplasm triggers the mobilization of Ca^<2+> from internal stores and causes an increase in the level of cytoplasmic Ca^<2+> that is responsible for the inhibition of streaming. Possible mechanisms for the osmosis-induced increases in the level of Ca^<2+> in the cytoplasm are discussed.


MIMURA Tetsuro Department of Biology, Graduate School of Science, Kobe University
Mimura Tetsuro Department Of Biological Science Faculty Of Science Nara-women's University
Kikuyama Munehiro Biological Laboratory, The University of the Air
Mimura Tetsuro Biological Laboratory Hitotsubashi University
Kikuyama M Niigata Univ. Niigata Jpn
Tazawa Masashi Fukui Institute of Technology
Yokoo Takehiko Department of Botany, Faculty of Science, The University of Tokyo
Yokoo Takehiko Department Of Botany Faculty Of Science The University Of Tokyo
Kikuyama Munehiro Biological Laboratory The University Of The Air.
Mimura T Graduate School Of Science Kobe University
Kikuyama Munehiro Biological Laboratory The University Of The Air