Aluminum resistance in the Arabidopsis mutant alr-104 is caused by an aluminum-induced increase in rhizosphere pH

• Published in: Plant physiology (Bethesda) Vol. 117; no. 1; pp. 19 - 27
• Main Authors: Degenhardt, J. (United States Plant, Soil, and Nutrition Laboratory, USDA, ARS, Cornell University, Ithaca, NY.), Larsen, P.B, Howell, S.H, Kochian, L.V
• Format: Journal Article
• Language: English
• Published: Rockville, MD American Society of Plant Physiologists 01.05.1998
• Subjects: Agronomy. Soil science and plant productions; ALUMINIO; ALUMINIUM; Aluminum; Aluminum - pharmacology; Arabidopsis - drug effects; Arabidopsis - genetics; Arabidopsis - metabolism; ARABIDOPSIS THALIANA; Biological and medical sciences; CRECIMIENTO; CROISSANCE; Drug Resistance - genetics; Economic plant physiology; FITOTOXICIDAD; Fundamental and applied biological sciences. Psychology; Gels; GENETIC ANALYSIS; GENETIC VARIATION; GENETICA; GENETICS; GENETIQUE; GROWTH; HIDROGENO; HYDROGEN; Hydrogen-Ion Concentration - drug effects; HYDROGENE; ION; ION UPTAKE; Ion-Selective Electrodes; IONES; IONS; LOCALIZATION; MEASUREMENT; MEDICION; MESURE; Microelectrodes; Mineral nutrition; MUTANT; MUTANTES; MUTANTS; Mutation; Nutrient solutions; Nutrition. Photosynthesis. Respiration. Metabolism; PHYTOTOXICITE; PHYTOTOXICITY; Plant physiology and development; Plant roots; Plant Roots - metabolism; Plants; PLANTULAS; PLANTULE; RACINE; RAICES; RHIZOSPHERE; RIZOSFERA; Root growth; ROOT TIPS; ROOTS; SEEDLINGS; STRESS RESPONSE; VARIACION GENETICA; VARIATION GENETIQUE; Vibration; Water and solutes. Absorption, translocation and permeability; Whole Plant, Environmental, and Stress Physiology; WILD STRAINS; Root; Growth; Aluminium; Arabidopsis thaliana; Resistance; Rhizosphere; Cruciferae; Dicotyledones; Angiospermae; pH; Spermatophyta; Mutation; Experimental plant; Mechanism of action; Proton transport
• ISSN: 0032-0889; 1532-2548
• DOI: 10.1104/pp.117.1.19

A mechanism that confers increased Al resistance in the Arabidopsis thaliana mutant alr-104 was investigated. A modified vibrating microelectrode system was used to measure H+ fluxes generated along the surface of small Arabidopsis roots. In the absence of Al, no differences in root H+ fluxes between wild type and alr-104 were detected. However, Al exposure induced a 2-fold increase in net H+ influx in alr-104 localized to the root tip. The increased flux raised the root surface pH of alr-104 by 0.15 unit. A root growth assay was used to assess the Al resistance of alr-104 and wild type in a strongly pH-buffered nutrient solution. Increasing the nutrient solution pH from 4.4 to 4.5 significantly increased Al resistance in wild type, which is consistent with the idea that the increased net H+ influx can account for greater Al resistance in alr-104. Differences in Al resistance between wild type and alr-104 disappeared when roots were grown in pH-buffered medium, suggesting that Al resistance in alr-104 is mediated only by pH changes in the rhizosphere. This mutant provides the first evidence, to our knowledge, for an Al-resistance mechanism based on an Al-induced increase in root surface pH