Genome wide identification, evolution and expression analysis of NHX gene family in cultivated barley (Hordeum vulgare. L) grown under salinity.

BACKGROUND

The Na⁺/H⁺ antiporter (NHX) gene family in plants encodes proteins that maintain ion homeostasis, particularly under salt stress, by exchanging Na⁺ or K⁺ for H⁺ across cellular membranes. In cultivated barley (Hordeum vulgare L.), NHX genes have been only partially characterized.

METHODS AND

RESULTS

In this study, we conducted a genome-wide identification of NHX genes in barley, examining their evolutionary relationships, gene structure, and expression patterns under salt stress (200 mM NaCl) in two genotypes differing in salinity tolerance. Seven genes were identified in the H. vulgare genome, and they are unevenly distributed across chromosomes 2 H, 3 H, 4 H, 5 H, and 7 H. Phylogenetic analysis showed that these genes group into three major classes: Vac (HvNHX1, HvNHX2 and HvNHX3), Endo (HvNHX4, HvNHX5 and HvNHX6), and PM (HvNHX7/HvSOS1). Furthermore, exon-intron organization and conserved motif composition were highly conserved within each class. Vac-class NHX proteins were found to contain an amiloride-binding site in TM3 within their N-terminal region. Promoter analysis revealed that HvNHX1, HvNHX5, HvNHX6, and HvNHX7 possess the highest number of abscisic acid (ABA)-responsive elements (ABREs), suggesting potential regulation via the ABA signaling pathway. The protein-protein interaction (PPI) network indicated that several HvNHX proteins interact with HKT, GORK, CHX and KEA partners. Finally, the RT-qPCR analysis revealed a differential expression of NHX genes between the two contrasting barley genotypes in both roots and leaves under salinity.

CONCLUSION

Our findings provide valuable insights into candidate genes that may be targeted in future genetic engineering strategies to enhance salinity tolerance in barley.