Open Access

ARTICLE

Survey of Barley Sodium Transporter HvHKT1;1 Variants and Their Functional Analysis

Shahin Imran^1,2, Maki Katsuhara^1,*

1 Institute of Plant Science and Resources, Okayama University, 2 Chome-20-1 Central, Kurashiki, 710-0046, Japan
2 Department of Agronomy, Khulna Agricultural University, Khulna, 9100, Bangladesh

* Corresponding Author: Maki Katsuhara. Email:

(This article belongs to the Special Issue: Plant Responses to Biological and Abiotic Stresses)

Phyton-International Journal of Experimental Botany 2025, 94(11), 3653-3665. https://doi.org/10.32604/phyton.2025.073959

Received 29 September 2025; Accepted 03 November 2025; Issue published 01 December 2025

Abstract

Barley (Hordeum vulgare L.) employs the Na⁺ transporter HvHKT1;1, which is an N⁺-selective transporter. This study characterized the full-length HvHKT1;1 (HvHKT1;1-FL) and three mRNA variants (HvHKT1;1-V1, -V2, and -V3), which encode polypeptides of 64.7, 54.0, 40.5, and 32.9 kDa, respectively. Tissue-specific expression profiling revealed that HvHKT1;1-FL is the most abundant transcript across leaf, sheath, and root tissues under normal conditions, with the highest expression in leaves. Under 150 mM NaCl stress, HvHKT1;1-FL and its variants showed a dynamic, time-dependent expression pattern, with peak leaf expression at 2 h, sheath expression at 12 h, and root expression at 2 h, suggesting their roles in early stress response. Functional analysis using two-electrode voltage-clamp measurements demonstrated that HvHKT1;1-FL is highly selective for Na⁺, with minimal conductance for K⁺, Li⁺, Rb⁺, or Cs⁺. It demonstrated high Na⁺ transport efficiency, characterized by higher Vmax and lower Km values, while the variants showed reduced Na⁺ currents, lower Vmax, and higher Km values, indicating decreased Na⁺ transport capacity. Reversal potential analyses further confirmed Na⁺ selectivity, with HvHKT1;1-FL displaying the strongest preference for Na⁺. Notably, while all variants retained Na⁺ selectivity, they showed reduced efficiency, as indicated by a more negative reversal potential in low Na⁺ conditions. These findings highlight the functional diversity among HvHKT1;1 variants, with HvHKT1;1-FL playing a dominant role in Na⁺ transport. The tissue-specific regulation of these variants under salinity stress underscores their importance in barley’s adaptive responses.

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Keywords

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Supplementary Material

Supplementary Material File

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