title: Sodium influx and accumulation in Arabidopsis.
abstract: Arabidopsis is frequently used as a genetic model in plant salt tolerance studies, however, its physiological responses to salinity remain poorly characterized. This study presents a characterization of initial Na+ entry and the effects of Ca2+ on plant growth and net Na+ accumulation in saline conditions. Unidirectional Na+ influx was measured carefully using very short influx times in roots of 12-d-old seedlings. Influx showed three components with distinct sensitivities to Ca2+, diethylpyrocarbonate, and osmotic pretreatment. Pharmacological agents and known mutants were used to test the contribution of different transport pathways to Na+ uptake. Influx was stimulated by 4-aminobutyric acid and glutamic acid; was inhibited by flufenamate, quinine, and cGMP; and was insensitive to modulators of K+ and Ca2+ channels. Influx did not differ from wild type in akt1 and hkt1 insertional mutants. These data suggested that influx was mediated by several different types of nonselective cation channels. Na+ accumulation in plants grown in 50 mM NaCl was strongly reduced by increasing Ca2+ activity (from 0.05-3.0 mM), and plant survival was improved. However, plant biomass was not affected by shoot Na+ concentration, suggesting that in Arabidopsis Na+ toxicity is not dependent on shoot Na+ accumulation. These data suggest that Arabidopsis is a good model for investigation of Na+ transport, but may be of limited utility as a model for the study of Na+ toxicity.
authors.affiliation: Department of Plant Sciences, University of Cambridge, Cambridge CB2 3EA, United Kingdom.
authors.forename: Pauline A
authors.initials: PA
authors.lastname: Essah
authors.forename: Romola
authors.initials: R
authors.lastname: Davenport
authors.forename: Mark
authors.initials: M
authors.lastname: Tester
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism; D015220:Calcium Channels / Q000187:drug effects / Q000378:metabolism; D004047:Diethyl Pyrocarbonate / Q000494:pharmacology; D006861:Hydrogen Peroxide / Q000494:pharmacology; D009154:Mutation; D009997:Osmotic Pressure / Q000187:drug effects; D018520:Plant Shoots / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D018526:Plant Transpiration / Q000187:drug effects; D011092:Polyethylene Glycols / Q000494:pharmacology; D015221:Potassium Channels / Q000187:drug effects / Q000378:metabolism; D012964:Sodium / Q000378:metabolism*; D012965:Sodium Chloride / Q000494:pharmacology; D013997:Time Factors
chemical_list: D015220:Calcium Channels; D015221:Potassium Channels; D011092:Polyethylene Glycols; D012965:Sodium Chloride; D012964:Sodium; D006861:Hydrogen Peroxide; D004047:Diethyl Pyrocarbonate; D002118:Calcium