Cloning and characterization of a Ca2+/H+ exchanger from the halophyte Salicornia europaea L.

The calcium ion (Ca2+), which functions as a second messenger, plays an important role in plants' responses to various abiotic stresses, and Ca2+/H+ exchangers (CAXs) are an important part of this process. In this study, we isolated and characterized a putative Ca2+/H+ exchanger gene (SeCAX3) from Salicornia europaea L., a succulent, leafless euhalophyte. The SeCAX3 open reading frame was 1368 bp long and encoded a 455-amino-acid polypeptide that showed 67.9% similarity to AtCAX3. SeCAX3 was expressed in the shoots and roots of S. europaea. Expression of SeCAX3 was up-regulated by Ca2+, Na+, sorbitol, Li+, abscisic acid, and cold treatments in shoots, but down-regulated by Ca2+, sorbitol, abscisic acid, and cold treatments in roots. When SeCAX3 was transformed into a Ca-sensitive yeast strain, the transformed cells were able to grow in the presence of 200 mM Ca2+. Furthermore, SeCAX3 conferred drought, salt, and cold tolerance in yeast. Compared with the control strains, the yeast transformants expressing SeCAX3 were able to grow well in the presence of 30 mM Li+, 150 mM Mg2+, or 6 mM Ba2+. These results showed that the expression of SeCAX3 in yeast suppressed its Ca2+ hypersensitivity and conferred tolerance to Mg2+ and Ba2+. Together, these findings suggest that SeCAX3 might be a Ca2+ transporter that plays a role in regulating cation tolerance and the responses of S. europaea to various abiotic stresses. (C) 2015 Elsevier Masson SAS. All rights reserved.