The Arabidopsis concentration-dependent influx/efflux transporter ABCB4 regulates cellular auxin levels in the root epidermis
Language English Country England, Great Britain Media print-electronic
Document type Journal Article, Research Support, Non-U.S. Gov't, Research Support, U.S. Gov't, Non-P.H.S.
- MeSH
- ATP-Binding Cassette Transporters genetics metabolism MeSH
- Arabidopsis cytology drug effects genetics physiology MeSH
- Biological Transport MeSH
- Cell Membrane metabolism MeSH
- Plant Epidermis cytology metabolism MeSH
- Indoles metabolism MeSH
- Plant Roots cytology metabolism MeSH
- 2,4-Dichlorophenoxyacetic Acid metabolism MeSH
- Indoleacetic Acids metabolism MeSH
- Mutation MeSH
- Oxindoles MeSH
- Arabidopsis Proteins genetics metabolism MeSH
- Schizosaccharomyces genetics metabolism MeSH
- Signal Transduction physiology MeSH
- Nicotiana genetics metabolism MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
- Research Support, U.S. Gov't, Non-P.H.S. MeSH
- Names of Substances
- 2-oxindole MeSH Browser
- ATP-Binding Cassette Transporters MeSH
- ABCB4 protein, Arabidopsis MeSH Browser
- indoleacetic acid MeSH Browser
- Indoles MeSH
- 2,4-Dichlorophenoxyacetic Acid MeSH
- Indoleacetic Acids MeSH
- Oxindoles MeSH
- Arabidopsis Proteins MeSH
Arabidopsis ATP-binding cassette B4 (ABCB4) is a root-localised auxin efflux transporter with reported auxin uptake activity in low auxin concentrations. Results reported here demonstrate that ABCB4 is a substrate-activated regulator of cellular auxin levels. The contribution of ABCB4 to shootward auxin movement at the root apex increases with auxin concentration, but in root hair elongation assays ABCB4-mediated uptake is evident at low concentrations as well. Uptake kinetics of ABCB4 heterologously expressed in Schizosaccharomyces pombe differed from the saturation kinetics of AUX1 as uptake converted to efflux at threshold indole-3-acetic acid (IAA) concentrations. The concentration dependence of ABCB4 appears to be a direct effect on transporter activity, as ABCB4 expression and ABCB4 plasma membrane (PM) localisation at the root apex are relatively insensitive to changes in auxin concentration. However, PM localization of ABCB4 decreases with 1-naphthylphthalamic acid (NPA) treatment. Unlike other plant ABCBs studied to date, and consistent with decreased detergent solubility, ABCB4(pro) :ABCB4-GFP is partially internalised in all cell types by 0.05% DMSO, but not 0.1% ethanol. In trichoblasts, ABCB4(pro) :ABCB4-GFP PM signals are reduced by >200 nm IAA and 2,4-dichlorophenoxyacetic acid (2,4-D). In heterologous systems and in planta, ABCB4 transports benzoic acid with weak affinity, but not the oxidative catabolism products 2-oxindole-3-acetic-acid and 2-oxindole-3-acetyl-β-D-glucose. ABCB4 mediates uptake, but not efflux, of the synthetic auxin 2,4-D in cells lacking AUX1 activity. Results presented here suggest that 2,4-D is a non-competitive inhibitor of IAA transport by ABCB4 and indicate that ABCB4 is a target of 2,4-D herbicidal activity.
References provided by Crossref.org
Inactivation of the entire Arabidopsis group II GH3s confers tolerance to salinity and water deficit
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Advances in Understanding the Mechanism of Action of the Auxin Permease AUX1
Auxins and Cytokinins-The Role of Subcellular Organization on Homeostasis
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