Characterization of a family of vacuolar Na+/H+ antiporters in Arabidopsis thaliana

A family of AtNHX1-like genes of Arabidopsis thaliana, coding for vacuolar Na+/H+ antiporters, was cloned and functionally characterized by their heterologous expression in yeast mutants lacking an endosomal vacuolar antiporter. The expression of all of the AtNHX members of the family provided a recovery of the salt sensitive yeast mutant, supporting their role in Na+/H+ exchange. RT-PCR, used to determine the relative abundance of the AtNHX transcripts, showed that while AtNHX1 and AtNHX2 transcripts were abundant and widely distributed in all tissues, AtNHX3 and AtNHX4 transcripts were almost exclusively detected in flower and root tissues, respectively. AtNHX5 transcripts were observed at very low levels in all tissues. The potential for the use of these genes for the engineering of salt tolerance in crop plants is discussed.