Raising the cytosolic Ca2+ concentration increases the membrane capacitance of maize coleoptile protoplasts: Evidence for Ca2+-stimulated exocytosis |
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Authors: | Gerhard Thiel Marjan Rupnik Robert Zorec |
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Institution: | (1) Pflanzenphysiologisches Institut der Universität, Untere Karspüle 2, D-37073 Göttingen, Germany;(2) Laboratory of Neuroendocrinology, Institut of Pathophysiology, School of Medicine, 61105 Ljubljana, Slovenia |
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Abstract: | Enhanced elongation of coleoptile cells has been proposed to be related to a rise in secretory activity. Therefore, to obtain a direct measurement of exocytotic events in maize (Zea mays L.) coleoptile protoplasts we used the patch-clamp method to record changes in membrane capacitance (Cm) as a parameter proportional to fluctuations of the membrane surface area. The secretory activity of protoplasts was correlated with the cytosolic free Ca2+ concentration (Ca2+]cyt): dialyzing protoplasts with 1 M Ca2+]cyt caused a steady rise in Cm of 3.3 ± pF·s–1. In contrast, dialysis with a solution containing <20 nM Ca2+ produced a small and persistent decrease in Cm. This demonstrates that secretory activity in coleoptile cells can be controlled by factors which modulate Ca2+]cyt.Abbreviation Cm
membrane capacitance
This work was made possible by a visiting grant from the Research Council of Slovenia and financial support of the Deutsche Forschungsgemeinschaft to G.T. We are grateful to Dr. W. Diekmann (University of Göttingen) for teaching us the preparation of coleoptile protoplasts. |
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Keywords: | Calcium (cytosolic) Coleoptile Exocytosis Membrane capacitance (patch-clamp) Zea (Ca2+ protoplast) |
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