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|Title:||Malate-permeable channels and cation channels activated by aluminum in the apical cells of wheat roots|
|Citation:||Plant Physiology, 2001; 125(3):1459-1472|
|Publisher:||Amer Soc Plant Physiologists|
|Wen-Hao Zhang, Peter R. Ryan, and Stephen D. Tyerman|
|Abstract:||Aluminum (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.|
|Keywords:||Triticum; Plant Roots; Aluminum; Malates; Niflumic Acid; Ion Channels; Cyclic AMP; Biological Transport; Permeability; ortho-Aminobenzoates|
|Appears in Collections:||Agriculture, Food and Wine publications|
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