title: Low-pH and aluminum resistance in arabidopsis correlates with high cytosolic magnesium content and increased magnesium uptake by plant roots.
abstract: Low-pH stress and Al(3+) toxicity affect root growth in acid soils. It was hypothesized that the capacity of genotypes to maintain Mg(2+) uptake in acidic environments may contribute to low-pH and Al resistance, but explicit evidence is lacking. In this work, an Al-resistant alr104 mutant and two Al-sensitive mutants (als5 and als3) of Arabidopsis thaliana were compared with the wild type (Col-0) for Mg(2+) uptake and intracellular Mg(2+) concentration under low-pH and combined low-pH/Al stresses. Magnesium accumulation in roots was measured in long-term (7 d) experiments. The Mg(2+) fluxes were measured using ion-sensitive microelectrodes at the distal elongation and the mature root zones in short-term (0-60 min) experiments. Intracellular Mg(2+) concentrations were measured in intact root cells at the distal elongation zone using magnesium-specific fluorescent dye and fluorescent lifetime imaging (FLIM) analysis. Under low-pH stress, Arabidopsis mutants als5 and alr104 maintained a higher Mg concentration in roots, and had greater Mg(2+) influx than the wild type and the als3 mutant. Under combined low-pH/Al treatment, Al-resistant genotypes (wild type and alr104) maintained a higher Mg(2+) accumulation, and had a higher Mg(2+) influx and higher intracellular Mg(2+) concentration than Al-sensitive genotypes (als3 and als5). Overall, these results show that increased Mg(2+) uptake correlates with an enhanced capacity of Arabidopsis genotypes to cope with low-pH and combined low-pH/Al stresses.
authors.affiliation: School of Earth and Environment, University of Western Australia, Crawley, WA 6009, Australia. Jay.Bose@utas.edu.au
authors.forename: Jayakumar
authors.initials: J
authors.lastname: Bose
authors.forename: Olga
authors.initials: O
authors.lastname: Babourina
authors.forename: Sergey
authors.initials: S
authors.lastname: Shabala
authors.forename: Zed
authors.initials: Z
authors.lastname: Rengel
mesh_terms: D000535:Aluminum / Q000378:metabolism / Q000494:pharmacology*; D017360:Arabidopsis / Q000166:cytology / Q000235:genetics / Q000378:metabolism*; D001692:Biological Transport / Q000187:drug effects / Q000235:genetics; D003600:Cytosol / Q000187:drug effects* / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004351:Drug Resistance / Q000235:genetics; D005838:Genotype; D006863:Hydrogen-Ion Concentration; D042541:Intracellular Space / Q000187:drug effects / Q000378:metabolism; D008274:Magnesium / Q000378:metabolism*; D009154:Mutation; D018517:Plant Roots / Q000166:cytology / Q000235:genetics / Q000378:metabolism*; D013997:Time Factors
chemical_list: D000535:Aluminum; D008274:Magnesium
keywords: Aluminum toxicity; Arabidopsis thaliana; Intracellular magnesium; Low pH; Magnesium flux