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<p>Salt stress poses a significant challenge to crop productivity, making it essential to understand the genetic mechanisms underlying salt tolerance in barley (<i>Hordeum vulgare</i>). In this study, we performed a comprehensive analysis of the barley NHX gene family (HvNHX), which is known to function in Na<sup>+</sup>/H<sup>+</sup> exchange and ion homeostasis under stress conditions. Sixteen barley NHX genes (<i>HvNHX1–HvNHX16</i>) were identified and mapped to chromosomes 5H and 7H. The predicted HvNHX proteins varied in molecular weight, isoelectric point, instability index, hydrophobicity, and predicted subcellular localization, indicating biochemical and spatial diversity within the family. Promoter analysis of the 2-kb upstream regions revealed abundant hormone- and stress-responsive <i>cis</i>-elements, including ABRE, MBS, and G-box motifs, suggesting transcriptional regulation by abscisic acid, drought/salinity-related signaling, and light-associated regulatory pathways. Phylogenetic analysis of NHX proteins from barley and other plant species resolved the family into three major groups, a classification supported by conserved motif organization and gene-structure patterns. Gene Ontology enrichment indicated that HvNHX genes are primarily associated with sodium and potassium transmembrane transport, ion homeostasis, and membrane-associated transport activity. qRT-PCR analysis under salt stress at 0, 2, 6, 12, 24, 36, and 48 h revealed strongly time-dependent and gene-specific expression patterns. <i>HvNHX3, HvNHX9, HvNHX13,</i> and <i>HvNHX14</i> showed early induction at 2 h, whereas <i>HvNHX1, HvNHX4, HvNHX7, HvNHX11, HvNHX12</i>, and <i>HvNHX16</i> reached peak expression at 6 h. Several genes, including <i>HvNHX2, HvNHX4, HvNHX6, HvNHX8, HvNHX10, HvNHX15,</i> and <i>HvNHX16,</i> maintained elevated expression at 48 h, suggesting roles in sustained ionic adjustment during prolonged salt exposure. Collectively, these results demonstrate that the barley HvNHX family is structurally diversified, transcriptionally responsive to salt stress, and likely contributes to both early and sustained ion-homeostasis responses. This study provides a genome-wide framework for prioritizing <i>HvNHX</i> candidates for functional validation and for improving barley salt tolerance.</p>

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Exploring salt-stress adaptation: genome-wide identification and expression profiling of the NHX (Na+/H+ antiporter) gene family in barley

  • 期刊论文

  • 发表日期：

    2026年6月28日

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  • Fatmah Ahmed Safhi,
  • Samar G. Thabet

摘要

Salt stress poses a significant challenge to crop productivity, making it essential to understand the genetic mechanisms underlying salt tolerance in barley (Hordeum vulgare). In this study, we performed a comprehensive analysis of the barley NHX gene family (HvNHX), which is known to function in Na+/H+ exchange and ion homeostasis under stress conditions. Sixteen barley NHX genes (HvNHX1–HvNHX16) were identified and mapped to chromosomes 5H and 7H. The predicted HvNHX proteins varied in molecular weight, isoelectric point, instability index, hydrophobicity, and predicted subcellular localization, indicating biochemical and spatial diversity within the family. Promoter analysis of the 2-kb upstream regions revealed abundant hormone- and stress-responsive cis-elements, including ABRE, MBS, and G-box motifs, suggesting transcriptional regulation by abscisic acid, drought/salinity-related signaling, and light-associated regulatory pathways. Phylogenetic analysis of NHX proteins from barley and other plant species resolved the family into three major groups, a classification supported by conserved motif organization and gene-structure patterns. Gene Ontology enrichment indicated that HvNHX genes are primarily associated with sodium and potassium transmembrane transport, ion homeostasis, and membrane-associated transport activity. qRT-PCR analysis under salt stress at 0, 2, 6, 12, 24, 36, and 48 h revealed strongly time-dependent and gene-specific expression patterns. HvNHX3, HvNHX9, HvNHX13, and HvNHX14 showed early induction at 2 h, whereas HvNHX1, HvNHX4, HvNHX7, HvNHX11, HvNHX12, and HvNHX16 reached peak expression at 6 h. Several genes, including HvNHX2, HvNHX4, HvNHX6, HvNHX8, HvNHX10, HvNHX15, and HvNHX16, maintained elevated expression at 48 h, suggesting roles in sustained ionic adjustment during prolonged salt exposure. Collectively, these results demonstrate that the barley HvNHX family is structurally diversified, transcriptionally responsive to salt stress, and likely contributes to both early and sustained ion-homeostasis responses. This study provides a genome-wide framework for prioritizing HvNHX candidates for functional validation and for improving barley salt tolerance.