Journal Article

Characterization of Citrate Transport through the Plasma Membrane in a Carrot Mutant Cell Line with Enhanced Citrate Excretion

Takashi Ohno, Hiroyuki Koyama and Tetsuo Hara

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 44, issue 2, pages 156-162
Published in print February 2003 | ISSN: 0032-0781
Published online February 2003 | e-ISSN: 1471-9053 | DOI: https://dx.doi.org/10.1093/pcp/pcg025
Characterization of Citrate Transport through the Plasma Membrane in a Carrot Mutant Cell Line with Enhanced Citrate Excretion

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The superior ability of citrate excretion in a carrot (Daucus carota L.) mutant cell line, namely IPG (insoluble phosphate grower) [Takita et al. (1999a) Plant Cell Physiol. 40: 489] cells has been characterized in terms of citrate transport at the plasma membrane. IPG cells released about a 20-fold increase in citrate in comparison with malate, while the concentration of malate was only 35% lower than that of citrate in the cell sap. Citrate excretion was sensitive to anion channel blockers, such as niflumic acid and anthracene-9-carboxylic acid. These results indicate that IPG cells release citrate through the plasma membrane using citrate specific anion channels. The rate of citrate release from IPG cells was not affected by the concentration of aluminum (0 and 50 µM), soluble Pi (0 or 2 mM) and the pH (4.5–5.6) of the medium, suggesting that anion channels would not be regulated by such external conditions. Citrate excretion correlated with the H+ efflux, possibly from the action of H+-ATPase on the plasma membrane. The activity of plasma membrane H+-ATPase was about three times higher in IPG cells than in wild-type cells, and might be involved in the high citrate excretion ability.

Keywords: Keywords: Aluminum phosphate — Anion channel — Citrate excretion — Daucus carota — H+-ATPase.; Abbreviations: A-9-C, anthracene-9-carboxylic acid; DIDS, 4,4′-diisothiocyanostilbene-2,2′-disulfonic acid; EA, ethacrynic acid; IPG, insoluble phosphate grower; NA, niflumic acid; WT, wild-type.

Journal Article.  5571 words.  Illustrated.

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

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