Cellular Na +/K + ratio is a crucial parameter determining plant salinity stress resistance. We tested the function of plasma membrane Na +/K + cotransporters in the High-affinity K + Transporter (HKT) family from the halophytic Arabidopsis (Arabidopsis thaliana) relative Thellungiella salsuginea. T. salsuginea contains at least two HKT genes. TsHKT1;1 is expressed at very low levels, while the abundant TsHKT1;2 is transcriptionally strongly up-regulated by salt stress. TsHKT-based RNA interference in T. salsuginea resulted in Na + sensitivity and K + deficiency. The athkt1 mutant lines overexpressing TsHKT1;2 proved less sensitive to Na + and showed less K + deficiency than lines overexpressing AtHKT1. TsHKT1;2 ectopically expressed in yeast mutants lacking Na + or K + transporters revealed strong K + transporter activity and selectivity for K + over Na +. Altering two amino acid residues in TsHKT1;2 to mimic the AtHKT1 sequence resulted in enhanced sodium uptake and loss of the TsHKT1;2 intrinsic K + transporter activity. We consider the maintenance of K + uptake through TsHKT1;2 under salt stress an important component supporting the halophytic lifestyle of T. salsuginea. © 2012 American Society of Plant Biologists.
Publication Source (Journal or Book title)
Ali, Z., Park, H., Ali, A., Oh, D., Aman, R., Kropornicka, A., Hong, H., Choi, W., Chung, W., Kim, W., Bressan, R., Bohnert, H., Lee, S., & Yun, D. (2012). TsHKT1;2, a HKT1 homolog from the extremophile arabidopsis relative Thellungiella salsuginea, shows K + specificity in the presence of NaCl. Plant Physiology, 158 (3), 1463-1474. https://doi.org/10.1104/pp.111.193110