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GrainGenes Reference Report: PPS-125-1459

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Reference	PPS-125-1459
Title	Malate-permeable channels and cation channels activated by aluminum in the apical cells of wheat roots
Journal	Plant Physiology
Year	2001
Volume	125
Pages	1459-1472
Author	Zhang WH Ryan PR Tyerman SD
Abstract	Summary: 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 > or = 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
External Databases	Pubmed: 11244125
Keyword	[ Hide all but 1 of 38 ] activation aluminum arabidopsis thaliana camp capacity cation channels cations cell channel channels complexes density efflux functional-characterization genotype guard-cells ion channels k+ locus malate mechanism membrane patch-clamp permeability plasma plasma membrane protoplast rhizosphere root root tips signal transduction single slow anion channels tolerance triticum aestivum voltage regulation wheat root wheat roots

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