Plant Cell Reports

, Volume 37, Issue 11, pp 1533–1546 | Cite as

Foxtail millet SiHAK1 excites extreme high-affinity K+ uptake to maintain K+ homeostasis under low K+ or salt stress

  • Haiwen Zhang
  • Wen Xiao
  • Wenwen Yu
  • Lei Yao
  • Legong Li
  • Jianhua Wei
  • Ruifen LiEmail author
Original Article


Key message

This is the first evidence that SiHAK1 acts as a K+ transporter and is modulated by internal and external K+, which expands our understanding of the significant physiological roles of large HAK/KUP/KT transporters in crops.


Crop genomes have shown the richness of K+ transporters in HAK/KUP/KT (High Affinity K+/K+ Uptake Proteins/K+ Transporter) family, and much progress have been achieved toward understanding the diverse roles of K+ uptake and translocation, and abiotic stresses resistance in this family. The HAK/KUP/KT family has increasingly been recognized to be at a pivotal status in the mediation of K+ translocation and long-term transport; however, our understanding of the molecular mechanisms remains limited. Foxtail millet is an ideal plant for studying long-distance potassium (K) transport because of its small diploid genome and better adaptability to arid lands. Here, we identified 29 putative HAK/KUP/KT proteins from the Setaria italica genome database. These genes were distributed in seven chromosomes of foxtail millet and divided into five clusters. SiHAK1 exhibited widespread expression in various tissues and significant up-regulation in the shoots under low K condition. SiHAK1 was localized in the cell membrane and low K elicited SiHAK1-meidated high-affinity K+ uptake activity in Cy162 yeast cells and Arabidopsis athak5 mutants. The transport activity of SiHAK1 was coordinately modulated by external K+ supply and internal K+ content in the cell under low K and high salt environment. Our findings reveal the K uptake mechanisms of SiHAK1 and indicated that it may be involved in the mediation of K homeostasis in S. italica under K+-deficiency and salt stress.


Setaria italica HAK/KUP/KT transporter High-affinity K+ transporter K+ homeostasis Salt tolerance 



This work was supported by Grants of Special Program for Innovation of Beijing Academy of Agriculture and Forestry Sciences (KJCX20170203, KJCX20180201) to R.L., the National Natural Science Foundation of China (31600212) to H.Z., the Natural Science Foundation of Beijing Municipality with grant (5182007) to H. Z., Beijing Municipal Science and Technology Project to J.W (Z161100000916003), and the National Transgenic Major Program of China (2014ZX0800917B) to J.W. We thank Drs. Begoña Benito (Madrid, Spain) and Hyeong Cheol Park (Korea) for kindly providing yeast mutant strains and vectors.

Compliance with ethical standards

Conflict of interest

The authors declare that they have no conflict of interest.

Supplementary material

299_2018_2325_MOESM1_ESM.pdf (871 kb)
Supplementary material 1 (PDF 870 KB)


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Copyright information

© Springer-Verlag GmbH Germany, part of Springer Nature 2018

Authors and Affiliations

  1. 1.Beijing Key Laboratory of Agricultural Genetic Resources and Biotechnology, Beijing Agro-biotechnology Research CenterBeijing Academy of Agriculture and Forestry SciencesBeijingChina
  2. 2.Beijing Key Laboratory of Plant Gene Resources and Biotechnology for Carbon Reduction and Environmental Improvement, College of Life SciencesCapital Normal UniversityBeijingChina

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