Exchangers man the pumps: functional interplay between proton pumps and proton-coupled Ca2+ exchangers
Barkla, BJ, Hirschi, KD & Pittman, JK 2008, 'Exchangers man the pumps: functional interplay between proton pumps and proton-coupled Ca2+ exchangers', Plant Signalling & Behavior, vol. 3, no. 5, pp. 354-356.
Tonoplast-localized proton-coupled Ca2+ transporters encoded by cation/H+ exchanger (CAX) genes play a critical role in sequestering Ca2+ into the vacuole. These transporters may function in coordination with Ca2+ release channels, to shape stimulus-induced cytosolic Ca2+ elevations. Recent analysis of Arabidopsis CAX knockout mutants, particularly cax1 and cax3, identified a variety of phenotypes including sensitivity to abiotic stresses, which indicated that these transporters might play a role in mediating the plant’s stress response. A common feature of these mutants was the perturbation of H+-ATPase activity at both the tonoplast and the plasma membrane, suggesting a tight interplay between the Ca2+/H+ exchangers and H+ pumps. We speculate that indirect regulation of proton flux by the exchangers may be as important as the direct regulation of Ca2+ flux. These results suggest cautious interpretation of mutant Ca2+/H+ exchanger phenotypes that may be due to either perturbed Ca2+ or H+ transport.