A Sodium Transporter HvHKT1;1 Confers Salt Tolerance in Barley via Regulating Tissue and Cell Ion Homeostasis

Yong Han, Shuya Yin, Lu Huang, Xuelong Wu, Jianbin Zeng, Xiaohui Liu, Long Qiu, Rana Munns, Zhong Hua Chen, Guoping Zhang

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Abstract

Our previous studies showed that high salt tolerance in Tibetan wild barley accessions was associated with HvHKT1;1, a member of high-affinity potassium transporter family. However, molecular mechanisms of HvHKT1;1 for salt tolerance and its roles in K+/Na+ homeostasis remain to be elucidated. Functional characterization of HvHKT1;1 was conducted in the present study. NaCl-induced transcripts of HvHKT1;1 were significantly higher in the roots of Tibetan wild barley XZ16 relative to other genotypes, being closely associated with its higher biomass and lower tissue Na+ 36 content under salt stress. Heterologous expression of HvHKT1;1 in Saccharomyces cerevisiae (yeast) and Xenopus laevis oocytes showed that HvHKT1;1 had higher selectivity to Na+ over K+ and other monovalent cations. HvHKT1;1 was found to be localized at the cell plasma membrane of root stele and epidermis. Knock-down of HvHKT1;1 in barley led to higher Na+ accumulation in both roots and leaves while over-expression of HvHKT1;1 in salt-sensitive Arabidopsis hkt1-4 and sos1-12 loss-of-function lines resulted in significantly less shoot and root Na+ accumulation. Additionally, microelectrode ion flux measurements and root elongation assay revealed that the transgenic Arabidopsis plants exhibited a remarkable capacity in regulating Na+, K+, Ca2+ and H+ homeostasis under salt stress. These results indicate that HvHKT1;1 is critical in radial root Na+ transport, which eventually reduces shoot Na+ accumulation. Besides, HvHKT1;1 may be indirectly involved in retention of K+ and Ca2+ in root cells, which also improves plant salt tolerance.
Original languageEnglish
Pages (from-to)1976-1989
Number of pages14
JournalPlant and Cell Physiology
Volume59
Issue number10
DOIs
Publication statusPublished - 1 Oct 2018

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