Zhang, W.Ryan, P.Tyerman, S.2007-07-052007-07-052001Plant Physiology, 2001; 125(3):1459-14720032-08891532-2548http://hdl.handle.net/2440/34565Aluminum (Al³⁺)-dependent efflux of malate from root apices is a mechanism for Al³⁺ tolerance in wheat (Triticum aestivum). The malate anions protect the sensitive root tips by chelating the toxic Al³⁺ cations in the rhizosphere to form non-toxic complexes. Activation of malate-permeable channels in the plasma membrane could be critical in regulating this malate efflux. We examined this by investigating Al³⁺-activated channels in protoplasts from root apices of near-isogenic wheat differing in Al³⁺ tolerance at a single locus. Using whole-cell patch clamp we found that Al³⁺ stimulated an electrical current carried by anion efflux across the plasma membrane in the Al³⁺-tolerant (ET8) and Al³⁺-sensitive (ES8) genotypes. This current occurred more frequently, had a greater current density, and remained active for longer in ET8 protoplasts than for ES8 protoplasts. The Al³⁺-activated current exhibited higher permeability to malate²⁻ than to Cl⁻ (Pmal/PCl ≥ 2.6) and was inhibited by anion channel antagonists, niflumate and diphenylamine-2-carboxylic acid. In ET8, but not ES8, protoplasts an outward-rectifying K⁺ current was activated in the presence of Al³⁺ when cAMP was included in the pipette solution. These findings provide evidence that the difference in Al³⁺-induced malate efflux between Al³⁺-tolerant and Al³⁺-sensitive genotypes lies in the differing capacity for Al³⁺ to activate malate permeable channels and cation channels for sustained malate release.enTriticumPlant RootsAluminumMalatesNiflumic AcidIon ChannelsCyclic AMPBiological TransportPermeabilityortho-AminobenzoatesJournal article002006345910.1104/pp.125.3.14590001681798000342-s2.0-003509962850910Tyerman, S. [0000-0003-2455-1643]