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Light-induced cytosolic calcium transients in green plant cells. ll. The effect on a K+ channel as studied by a kinetic analysis in Chara corallina
Authors:Christoph Plieth  Burkhard Sattelmacher  Ulf-Peter Hansen
Institution:Institute for Cell and Molecular Biology, University of Edinburgh, Mayfield Road, Edinburgh EH9 3JH, UK, GB
Institut für Pflanzenern?hrung und Bodenkunde, Christian-Albrechts-Universit?t, Hermann-Rodewald-Str. 2, D-24098 Kiel, Germany, DE
Institut für Angewandte Physik, Christian-Albrechts-Universit?t, Leibnizstr. 11, D-24098 Kiel, Germany, DE
Abstract:The fluorescent dye chlorotetracycline was used to study the relationship between the light-induced decrease in cytosolic free calcium concentration, Ca2+]c, and its effect on ion transport at the plasma membrane in the giant cells of Chara corallina Klein ex Willd. A kinetic analysis of the simultaneously measured light-induced changes in membrane potential and in Ca2+]c led to the same time constant of about 40 s. The reversal potential of the light effect on membrane potential was in agreement with the dominant role of a K+ channel in the plasma membrane. Thus, the experiments reported here provide evidence for the following light-driven signal transduction chain from the chloroplasts to K+ transport of the plasma membrane: (i) light causes an uptake of Ca2+ into the chloroplasts, (ii) this causes a decrease in cytosolic Ca2+]c, (iii) this leads to a decrease in the activity of a K+ channel. The results also initiated a re-analysis of previously published data of the light effect on the velocity of cytosolic streaming and supported the hypothesis that Ca2+ fluxes coming out of the chloroplasts upon darkening cause a Ca2+-induced phosphorylation of myosin, which slows down cytoplasmic streaming. Received: 3 May 1997 / Accepted: 19 May 1998
Keywords:: Chlorotetracycline  Chara  Cytoplasmic calcium  Light (membrane potential)  Photosynthesis  Protoplasmic streaming
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