RETRACTED: The AtCCX1 transporter mediates salinity tolerance in both Arabidopsis and yeast (Retracted article. See vol. 110, pg. 317, 2012)

Maintaining high cytosolic K+/Na+ ratio and detoxicity of Na+ is important for plant cell metabolism and resistance to salt stress. Cation calcium exchangers, CCXs, are a novel family of genes that have recently been separated from the family of cation exchangers, CAXs, and these are likely to be correlated with Na+ transport. In this study, an Arabidopsis CCX putative gene, AtCCX1, has been cloned, and second structure model is constructed. Moreover, expression patterns in various tissues of Arabidopsis have been investigated along with heterologous expression of AtCCX1 in yeast. The gene AtCCX1 contains 1713 nucleotides, with a short N-terminal hydrophilic domain that does not support an N-terminal autoinhibitory domain. Expression of AtCCX1 in Arabidopsis is higher under salt stress and drought stress when compared to wild-type, but when plants are exposed to either cold stress or abscisic acid treatment, no differences in expression levels are observed. Yeast lines expressing AtCCX1 are more tolerant to low pH medium and have displayed higher level of tolerance to sodium salt stress compared to wild-type lines. Inductively coupled plasma atomic emission spectroscopy analysis has revealed that following overexpression of AtCCX1 in yeast, accumulation of Na+ is increased, while accumulation of K+ and Cu2+ is decreased. These findings support the fact that AtCCX1 is critical for Na+ tolerance and may serve as a Na+/K+ exchanger, similar to AtCCX3.