Journal Article

Brassinosteroids Regulate Plasma Membrane Anion Channels in Addition to Proton Pumps During Expansion of <i>Arabidopsis thaliana</i> Cells

Zongshen Zhang, Javier Ramirez, David Reboutier, Mathias Brault, Jacques Trouverie, Anne-Marie Pennarun, Zahia Amiar, Bernadette Biligui, Lydia Galagovsky and Jean-Pierre Rona

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 46, issue 9, pages 1494-1504
Published in print September 2005 | ISSN: 0032-0781
Published online September 2005 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/pcp/pci162
Brassinosteroids Regulate Plasma Membrane Anion Channels in Addition to Proton Pumps During Expansion of Arabidopsis thaliana Cells

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Brassinosteroids (BRs) are involved in numerous physiological processes associated with plant development and especially with cell expansion. Here we report that two BRs, 28-homobrassinolide (HBL) and its direct precursor 28-homocastasterone (HCS), promote cell expansion of Arabidopsis thaliana suspension cells. We also show that cell expansions induced by HBL and HCS are correlated with the amplitude of the plasma membrane hyperpolarization they elicited. HBL, which promoted the larger cell expansion, also provoked the larger hyperpolarization. We observed that membrane hyperpolarization and cell expansion were partially inhibited by the proton pump inhibitor erythrosin B, suggesting that proton pumps were not the only ion transport system modulated by the two BRs. We used a voltage clamp approach in order to find the other ion transport systems involved in the PM hyperpolarization elicited by HBL and HCS. Interestingly, while anion currents were inhibited by both HBL and HCS, outward rectifying K+ currents were increased by HBL but inhibited by HCS. The different electrophysiological behavior shown by HBL and HCS indicates that small changes in the BR skeleton might be responsible for changes in bioactivity.

Keywords: Arabidopsis thaliana; Brassinosteroid; Ion currents; Plasma membrane; Proton pump; Suspension cells; ABP, auxin-binding protein; 9-AC, anthracene-9-carboxylic acid; BL, brassinolide; BR, brassinosteroid; DIDS, 4,4-diisothiocyano-2,2-stilbene disulfonate; EB, erythrosin B; FC, fusicoccin; HBL, 28-homobrassinolide; HCS, homoethylcastasterone; K+ ORC, potassium outward rectifying current; LRR, leucine-rich repeat; PM, plasma membrane; RLIT, rice lamina inclination test; SITS, 4-acetamido-4-isothiocyano-2,2-stilbene disulfonate; STG, stigmasterol; TEA, tetraethylammonium

Journal Article.  8180 words.  Illustrated.

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

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