Journal Article

Auxin is a Positive Regulator for Ethylene-Mediated Response in the Growth of Arabidopsis Roots

Abidur Rahman, Taisaku Amakawa, Nobuharu Goto and Seiji Tsurumi

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 42, issue 3, pages 301-307
Published in print March 2001 | ISSN: 0032-0781
Published online March 2001 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/pcp/pce035
Auxin is a Positive Regulator for Ethylene-Mediated Response in the Growth of Arabidopsis Roots

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The requirement of auxin for the ethylene-mediated growth response in the root of Arabidopsis thaliana seedlings was investigated using two ethylene-resistant mutants, aux1-7 and eir1-1, whose roots have been shown to have a defect in the auxin influx and efflux carriers, respectively. A 50% inhibition of growth (I50) was achieved with 0.84 µl liter–1 ethylene in wild-type roots, but 71.3 µl liter –1 ethylene was required to induce I50 in eir1-1 roots. In aux1-7 roots, I50 was not obtained even at 1,000 µl liter–1 ethylene. By contrast, in the presence of 10 nM 1-naphthaleneacetic acid (NAA), the concentrations of ethylene required to induce I50 in eir1-1 and aux1-7 roots were greatly reduced nearly to the level required in wild-type roots. Since the action of NAA to restore the ethylene response in aux1-7 roots was not replaced by IAA, an increase in the intracellular level of auxin is likely to be the cause for the restoration of ethylene response. NAA at 10 nM did not inhibit root growth when applied solely, but it was the optimum concentration to recover the ethylene response in the mutant roots. These results suggest that auxin is a positive regulator for ethylene-induced inhibition in root elongation.

Keywords: Key words: Arabidopsis thaliana — aux1 — Auxin — eir1 — Ethylene — Root growth.; Abbreviations: ACC, 1-aminocyclopropane-1-carboxylic acid; 2,4-D, 2,4-dichlorophenoxyacetic acid; I50, 50% inhibition of growth; NAA, 1-naphthaleneacetic acid; TIBA, 2,3,5-triiodobenzoic acid.

Journal Article.  4408 words.  Illustrated.

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

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