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Updated: Aug 18, 2026

Measuring Spatial and Temporal Ca2+ Signals in Arabidopsis Plants
Published on: September 2, 2014
CAX1, an H+/Ca2+ antiporter from Arabidopsis
K D Hirschi1, R G Zhen, K W Cunningham
1Whitehead Institute for Biomedical Research, Nine Cambridge Center, MA 02142, USA.
Abstract:
Reestablishment of the resting state after stimulus-coupled elevations of cytosolic-free Ca2+ requires the rapid removal of Ca2+ from the cytosol of plant cells. Here we describe the isolation of two genes, CAX1 and CAX2, from Arabidopsis thaliana that suppress a mutant of Saccharomyces cerevisiae that has a defect in vacuolar Ca2+ accumulation. Both genes encode polypeptides showing sequence similarities to microbial H+/Ca2+ antiporters. Experiments on vacuolar membrane-enriched vesicles isolated from yeast expressing CAX1 or CAX2 demonstrate that these genes encode high efficiency and low efficiency H+/Ca2+ exchangers, respectively. The properties of the CAX1 gene product indicate that it is the high capacity transporter responsible for maintaining low cytosolic-free Ca2+ concentrations in plant cells by catalyzing pH gradient-energized vacuolar Ca2+ accumulation.
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