Functional conservation between yeast and plant endosomal Na+/H+ antiporters

Vacuolar compartmentation of Na+ is an essential mechanism for salinity tol erance since it lowers cytosolic Na+ levels while contributing to osmotic a djustment for cell turgor and expansion, The AtNHX1 protein of,Arabidopsis thaliana substituted functionally for ScNHX1, the endosomal Na+/H+ antiport er of yeast, Ion tolerance conferred by AtNHX1 and ScSHX1 correlated with i on uptake into an intracellular pool that aas energetically dependent on th e vacuolar (H+)ATPase. AtNX1 localized to vacuolar membrane fractions of ye ast. Hence, both transporters share an evolutionarily conserved function in Na+ compartmentation, AtNHX1 mRNA levels were upregulated by ABA and NaCl treatment in leaf but not in root tissue. (C) 2000 Federation of European B iochemical Societies.