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

Vacuolar compartmentation of Na+ is an essential mechanism for salinity tolerance since it lowers cytosolic Na+ levels while contributing to osmotic adjustment for cell turgor and expansion, The AtNHX1 protein of,Arabidopsis thaliana substituted functionally for ScNHX1, the endosomal Na+/H+ antiporter of yeast, Ion tolerance conferred by AtNHX1 and ScSHX1 correlated with ion uptake into an intracellular pool that aas energetically dependent on the vacuolar (H+)ATPase. AtNX1 localized to vacuolar membrane fractions of yeast. 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 Biochemical Societies.