Phenotypic changes in Arabidopsis caused by expression of a yeast vacuolar Ca2+/H+ antiporter

In plants, cytosolic Ca²⁺ levels are tightly regulated, and changes in cytosolic Ca²⁺ have been implicated in converting numerous signals into adapted responses. Vacuolar ion transporters are thought to be key mediators of cytosolic Ca²⁺ concentrations. In an attempt to interpret the role of vacuolar Ca²⁺ transport in plant processes, we have expressed the yeast vacuolar Ca²⁺/H⁺ antiporter, VCX1, in Arabidopsis and tobacco. This transporter localizes to the plant vacuolar membrane. VCX1-expressing Arabidopsis plants displayed increased sensitivity to sodium and other ions. These ion sensitivities could be suppressed by addition of calcium to the media. VCX1-expressing plants demonstrated increased tonoplast-enriched Ca²⁺/H⁺ antiport activity as well as increased Ca²⁺ accumulation. These results suggest that VCX1 expression in Arabidopsis could be a valuable tool with which to experimentally dissect the role of Ca²⁺ transport around the plant vacuole.