[The role of intracellular Ca(2+) pools in the regulation of protoplast volume. Effect of red light on the Ca(2+) mobilization in cytoplasm of Arabidopsis cells].

The changes in cytosol Ca2+ concentration associated with the shrinkage of Arabidopsis cells induced by the inhibitor of Ca(2+)-ATPase, cyclopiazonic acid and the Ca2+ ionophore ionomycin were monitored using the fluorescence of Ca(2+)-sensitive probe chlortetracycline hydrochloride. It was found that these compounds elicited a substantial decrease in fluorescence intensity closely associated with Ca(2+)-release from the intracellular stores to the cytoplasm. The release of Ca2+ from the intracellular depots was accompanied by decrease of plant cell volume. Thapsigargin and 2,5'-ditert-butyl-1,4-benzohydroquinone (highly specific inhibitors of Ca(2+)-ATPase of endoplasmic reticulum) resulted in much weaker changes than cyclopiazonic acid did. It was also found with the help of the same technique that red light (lambda = 660 nm) illumination induced a similar Ca2+ release from the intracellular stores. Moreover, the amplitudes of light-induced fluorescence responses registered in mutant plants differing in the content of phytochrome A (phyAOX) and phytochrome B (phyBOX) were much higher than those registered in wild-type of Arabidopsis.