Journal Article

Regulation of Cytoplasmic pH under Extreme Acid Conditions in Suspension Cultured Cells of <i>Catharanthus roseus</i>: a Possible Role of Inorganic Phosphate

Tetsuro Mimura, Chihiro Shindo, Misako Kato, Etsuo Yokota, Katsuhiro Sakano, Hiroshi Ashihara and Teruo Shimmen

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 41, issue 4, pages 424-431
Published in print April 2000 | ISSN: 0032-0781
Published online April 2000 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/pcp/41.4.424
Regulation of Cytoplasmic pH under Extreme Acid Conditions in Suspension Cultured Cells of Catharanthus roseus: a Possible Role of Inorganic Phosphate

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Changes in cytoplasmic pH of suspension-cultured cells of Catharanthus roseus under extreme acid conditions were measured with the pH-dependent fluorescence dye; 2′,7′-bis-(2-carboxyethyl)-5 (and-6) carboxyfluorescein (-acetoxymethylester) (BCECF). When cells were treated with 1 mM HC1 (pH 3 solution), the cytoplasmic pH first decreased then returned to the original level. Treatment with 10 mM HC1 (pH 2 solution) acidified the cytoplasm to a greater extent, and the acidification continued at a constant level throughout the measurement. Treatment with a pH 2 solution resulted in a gradual decrease of the malate content, indicating the operation of biochemical pH regulation mechanism. The pH 2 treatment also caused a sudden decrease of the intracellular level of Pi. The cellular content of total phosphorus did not change during the acidification. The Pi was converted to the organic phosphate form. The ATP level was not increased by the pH 2 treatment, but slightly decreased. The role of Pi, which might be functioning as a regulatory factor of cytoplasmic pH, a non-competitive inhibitor of the H+-pumps of both the plasma membrane and tonoplast is discussed.

Keywords: Acid treatment; BCECF; Catharanthus roseus; Cytoplasmic pH; Inorganic phosphate; pH regulation

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Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry

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