A Low-Affinity K+ Transporter AlHKT2;1 from Recretohalophyte Aeluropus lagopoides Confers Salt Tolerance in Yeast
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The high-affinity potassium transporters (HKT) are highly important for stress tolerance in plants as they uniquely maintain K+/Na+ ratio for their survival and growth. In this study a novel HKT gene AlHKT2;1 was isolated and characterized from salt secreting halophyte, Aeluropus lagopoides. The AlHKT2;1 cDNA comprised of an open reading frame of 1,581 bp, encoding a protein of 526 amino acid residues. It belongs to class II HKTs and showed high homology with other HKT genes. Functional characterization of AlHKT2;1 in both K+ uptake‐deficient (WΔ6) and Na+-sensitive yeast mutants (G19) showed the characteristic feature of low-affinity K+ transporter supporting the growth at >1 mM KCl concentration. The transformed yeast cells showed high sensitivity to NaCl; however, the addition of KCl along with NaCl support the growth of AlHKT2;1 expressing mutant. Ion content analysis of yeast cells with AlHKT2;1 grown in high NaCl medium supplemented with KCl revealed that salt tolerance was correlated with accumulation of K+ during salt stress. These results suggest that AlHKT2;1 plays an important role in the K+ uptake during salt stress and in maintaining a high K+/Na+ ratio in the cytosol.
KeywordsAeluropus lagopoides HKT transporter Salt stress AlHKT2;1 S. cerevisiae
CSIR-CSMCRI Communication No. 185 as provided by BDIM. We are grateful to Dr Alonso Rodriguez-Navarro, Universidad Politecnica de Madrid, Spain, for kindly providing us with the WΔ6, W303.1A and G19 yeast strains and for the helpful discussions. The financial assistance from CSIR (OLP 0067) is greatly acknowledged. PA is thankful for Sennior Research Associateship (CSIR Scientists’ Pool Scheme). PS and JK are thankful to CSIR for Senior Research Fellowship and Junior Research Fellowship, respectively and AcSIR for enrolment in Ph.D.
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