Journal Article

Aluminum Rapidly Depolymerizes Cortical Microtubules and Depolarizes the Plasma Membrane: Evidence that these Responses are Mediated by a Glutamate Receptor

Mayandi Sivaguru, Sharon Pike, Walter Gassmann and Tobias I. Baskin

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 44, issue 7, pages 667-675
Published in print July 2003 | ISSN: 0032-0781
Published online July 2003 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/pcp/pcg094
Aluminum Rapidly Depolymerizes Cortical Microtubules and Depolarizes the Plasma Membrane: Evidence that these Responses are Mediated by a Glutamate Receptor

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Efforts to understand how plants respond to aluminum have focused on describing the symptoms of toxicity and elucidating mechanisms of tolerance; however, little is known about the signal transduction steps that initiate the plant’s response. Here, we image cortical microtubules and quantify plasma-membrane potential in living, root cells of intact Arabidopsis seedlings. We show that aluminum depolymerizes microtubules and depolarizes the membrane, and that these responses are prevented by calcium channel blockade. Calcium influx might involve glutamate receptors, which in animals are ligand-gated cation channels and are present in the Arabidopsis genome. We show that glutamate depolymerizes microtubules and depolarizes the plasma membrane. These responses, and also the inhibition of root elongation, occur within the first few min of treatment, but are evoked more rapidly by glutamate than by aluminum. Microtubule depolymerization and membrane depolarization, induced by either glutamate or aluminum, are blocked by a specific antagonist of ionotropic glutamate receptors, 2-amino-5-phosphonopentanoate; whereas an antagonist of an aluminum-gated anion channel blocks the two responses to aluminum but not to glutamate. For growth, microtubule integrity, and membrane potential, responses to combined glutamate and aluminum were not greater than to glutamate alone. We propose that signaling in response to aluminum is initiated by efflux of a glutamate-like ligand through an anion channel and the binding of this ligand to a glutamate receptor.

Keywords: Keywords: Aluminum — Arabidopsis thaliana — Cortical microtubules — Membrane potential — Ionotropic glutamate receptors — Roots.; Abbreviations: AP-5, 2-amino-5-phosphonopentanoate; GFP, green fluorescent protein; MBD, microtubule-binding domain; NMDA, N-methyl-d-aspartate; NPPB, 5-nitro-2-(3′-phenylpropyl-amino)-benzoate.

Journal Article.  6537 words.  Illustrated.

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

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