Molecular Cloning and Functional Analysis of a Na-Insensitive K Transporter of Jacq.

High-affinity K (HAK) transporters are encoded by a large family of genes and are ubiquitous in the plant kingdom. These HAK-type transporters participate in low- and high-affinity potassium (K) uptake and are crucial for the maintenance of K homeostasis under hostile conditions. In this study, the full-length cDNA of gene was isolated from roots of the habanero pepper (). expression was positively regulated by K starvation in roots and was not inhibited in the presence of NaCl. Phylogenetic analysis placed the CcHAK1 transporter in group I of the HAK K transporters, showing that it is closely related to CaHAK1 and LeHAK5. Characterization of the protein in a yeast mutant deficient in high-affinity K uptake (WΔ3) suggested that CcHAK1 function is associated with high-affinity K uptake, with K and V for Rb of 50 μM and 0.52 nmol mg min, respectively. K uptake in yeast expressing the CcHAK1 transporter was inhibited by millimolar concentrations of the cations ammonium ([Formula: see text]) and cesium (Cs) but not by sodium (Na). The results presented in this study suggest that the CcHAK1 transporter may contribute to the maintenance of K homeostasis in root cells in plants undergoing K-deficiency and salt stress.