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We previously cloned a vacuolar Na⁺/H⁺ antiporter gene (OsNHX1) from rice (Oryza sativa). Here we identified four additional NHX-type antiporter genes in rice (OsNHX2 through OsNHX5) and performed molecular and functional analyses of those genes. The exon-intron structure of the OsNHX genes and the phylogenetic tree of the OsNHX proteins suggest that the OsNHX proteins are categorized into two subgroups (OsNHX1 through OsNHX4 and OsNHX5). OsNHX1, OsNHX2, OsNHX3, and OsNHX5 can suppress the Na⁺, Li⁺, and hygromycin sensitivity of yeast nhx1 mutants and their sensitivity to a high K⁺ concentration. The expression of OsNHX1, OsNHX2, OsNHX3, and OsNHX5 is regulated differently in rice tissues and is increased by salt stress, hyperosmotic stress, and ABA. When we studied the expression of β-glucuronidase (GUS) driven by either the OsNHX1 or the OsNHX5 promoter, we observed activity in the stele, the emerging part of lateral roots, the vascular bundle, the water pore, and the basal part of seedling shoots with both promoters. In addition, each promoter had a unique expression pattern. OsNHX1 promoter-GUS activity only was localized to the guard cells and trichome, whereas OsNHX5 promoter-GUS activity only was localized to the root tip and pollen grains. Our results suggest that the members of this gene family play important roles in the compartmentalization into vacuoles of the Na⁺ and K⁺ that accumulate in the cytoplasm and that the differential regulation of antiporter gene expression in different rice tissues may be an important factor determining salt tolerance in rice.

Metagenomic DNA libraries constructed from the Dagong Ancient Brine Well were screened for genes with Na⁺/H⁺ antiporter activity on the antiporter-deficient Escherichia coli KNabc strain. One clone with a stable Na⁺-resistant phenotype was obtained and its Na⁺/H⁺ antiporter gene was sequenced and designated as m-nha. The deduced amino acid sequence of M-Nha protein consists of 523 residues with a calculated molecular weight of 58 147 Da and a pI of 5.50, which is homologous with NhaH from Halobacillus dabanensis D-8T (92%) and Halobacillus aidingensis AD-6T (86%), and with Nhe2 from Bacillus sp. NRRL B-14911 (64%). It had a hydropathy profile with 10 putative transmembrane domains and a long carboxyl terminal hydrophilic tail of 140 amino acid residues, similar to Nhap from Synechocystis sp. and Aphanothece halophytica, as well as NhaG from Bacillus subtilis. The m-nha gene in the antiporter-negative mutant E. coli KNabc conferred resistance to Na⁺ and the ability to grow under alkaline conditions. The difference in amino acid sequence and the putative secondary structure suggested that the m-nha isolated from the Dagong Ancient Brine Well in this study was a novel Na⁺/H⁺ antiporter gene.

Mungbean is an important pulse crop extensively cultivated in Southeast Asia for supply of easily digestible protein. Salinity severely limits the growth and productivity of mungbean, and weeding poses nutritional and disease constraints to mungbean cultivation. To pyramid both salt tolerance and protection against herbicide in mungbean, the encoding tonoplast Na /H antiporter from Arabidopsis, and gene associated with herbicide resistance were co-expressed through transformation. Stress inducible expression of significantly improved tolerance under salt stress to ionic, osmotic, and oxidative stresses in transgenic mungbean plants compared to the wild type (WT) plants, whereas constitutive expression of provided resistance to herbicide. Compared to WT, transgenic mungbean plants grew better with higher plant height, foliage, dry mass and seed yield under high salt stress (200 mM NaCl) in the greenhouse. The improved performance of transgenic plants under salt stress was associated with enhanced sequestration of Na in roots by vacuolar Na /H antiporter and limited transport of toxic Na to shoots, possibly by restricting Na influx into shoots. Transgenic plants showed better intracellular ion homeostasis, osmoregulation, reduced cell membrane damage, improved photosynthetic capacity, and transpiration rate as compared to WT when subjected to salt stress. Reduction in hydrogen peroxide and oxygen radical production indicated enhanced protection of transgenic plants to both salt- and methyl vialogen (MV)-induced oxidative stress. This study laid a firm foundation for improving mungbean yield in saline lands in Southeast Asia.

Salt stress affects plant growth and development, resulting in the loss of crop yield across the world, and sodium-proton antiporters (NHXs) are one of the genes known to promote salt tolerance in transgenic plants. In this study, we conducted a comprehensive genome-wide analysis and expression profile of NHX genes in wheat under salinity stress. We identified 30 TaNHX genes in wheat based on the Na + /H + exchanger domain, with all genes containing an amiloride motif except one, a known for inhibiting Na + ions in plants. Phylogenetic analysis classified these genes into three classes with subfamilies: 12 were localized in vacuoles, while 18 were in the endoplasmic reticulum and plasma membrane. Promoter analysis revealed stress-related cis -acting elements, indicating their potential role in abiotic stress tolerance. The non-synonymous (K a )/synonymous (K s ) ratios highlighted that the majority of TaNHX genes experienced robust purifying selection throughout their evolutionary history. Transcriptomis data analysis and qRT-PCR demonstrated distinct expression patterns for TaNHX genes across various tissues when subjected to salt stress. Additionally, we predicted 20 different miRNA candidates targeting the identified TaNHX genes. Protein-protein interaction prediction revealed NHX6’s involvement in the SOS1 pathway, while NHX1 gene exhibit proton antiporter activity. Molecular dynamics (MD) simulations were also conducted to examine the interactions of TaNHX1 , TaNHX2 , and TaNHX3 . These results represent a significant advancement in our understanding of the molecular mechanisms governing Na + transporters. This may also offer promising avenues for future studies aimed at unraveling the intricate details of their biological roles and applications.

Salinity tolerance in plants involves controlled Na⁺ transport at the site of Na⁺ accumulation and intracellular Na⁺ compartmentation. The focus of this study was the identification and analysis of the expression of Na⁺/H⁺ antiporters in response to NaCl stress in one particular plant, the facultative halophyte Mesembryanthemum crystallinum Na⁺/H⁺ antiporters of M. crystallinum were cloned by RACE-PCR from total mRNA of leaf mesophyll cells. Functional complementation of Saccharomyces cerevisiae and Escherichia coli mutants was performed. The kinetics of changes in the expression of antiporters were quantified by real-time PCR in leaves and roots. Five Na⁺/H⁺ antiporters (McSOS1, McNhaD, McNHX1, McNHX2 and McNHX3) were cloned, representing the entire set of these transporters in M. crystallinum. The functionality of McSOS1, McHX1 and McNhaD was demonstrated in complementation experiments. Quantitative analysis revealed a temporal correlation between salt accumulation and expression levels of genes in leaves, but not in roots, which was most pronounced for McNhaD. Results suggest a physiological role of McSOS1, McNhaD and McNHX1 in Na⁺ compartmentation during plant adaptation to high salinity. The study also provides evidence for salt-induced expression and function of the Na⁺/H⁺ antiporter McNhaD in chloroplasts and demonstrates that the chloroplast is one of the compartments involved in the response of cells to salt stress.

To develop a salt-tolerant upland rice cultivar (Oryza sativa L.), OsNHX1, a vacuolar-type Na⁺/H⁺ antiporter gene from rice was transferred into the genome of an upland rice cultivar (IRAT109), using an Agrobacterium-mediated method. Seven independent transgenic calli lines were identified by polymerase chain reaction (PCR) analysis. These 35S::OsNHX1 transgenic plants displayed a little accelerated growth during seedling stage but showed delayed flowering time and a slight growth retardation phenotype during late vegetative stage, suggesting that the OsNHX1 has a novel function in plant development. Northern and western blot analyses showed that the expression levels of OsNHX1 mRNA and protein in the leaves of three independent transgenic plant lines were significantly higher than in the leaves of wild type (WT) plants. T₂ generation plants exhibited increased salt tolerance, showing delayed appearance and development of damage or death caused by salt stress, as well as improved recovery upon removal from this condition. Several physiological traits, such as increased Na⁺ content, and decreased osmotic potential in transgenic plants grown in high saline concentrations, further indicated that the transgenic plants had enhanced salt tolerance. Our results suggest the potential use of these transgenic plants for further agricultural applications in saline soil.

Abiotic stresses such as drought, salinity, and heat affect plant growth and development. Karelinia caspica is a unique perennial herb that grows in desert area for a long time and has strong tolerance to environmental stresses. In order to explore the functions of the Na+/H+ antiporter gene from eremophyte K. caspica (KcNHX1) in the abiotic stress response of K. caspica and the underlying regulatory mechanisms, we constructed a vector overexpressing KcNHX1 and transformed it into Arabidopsis thaliana. The physiological results showed that the overexpression of KcNHX1 in A. thaliana not only enhanced the plant's tolerance to salt stress, but also enhanced its tolerance to drought and heat stress at the seedling stage. In addition, KcNHX1-overexpressing plants exhibited enhanced reproductive growth under high temperature, which was mediated by increased auxin accumulation. Taken together, our results indicate that KcNHX1 from an eremophyte can be used as a candidate gene to improve multiple stress tolerance in other plants.

Salinity is one of the major environmental factors that limit the plant growth and crop productivity worldwide. Tonoplast Na+/H+ transporters (NHXs) play crucial roles in regulating the intracellular Na+/K+ and pH homoeostasis, which is essential for salt tolerance and development of plants. In the present study, a novel gene BvNHX1 encoding tonoplast Na+/H+ antiporter was isolated in natrophilic crop sugar beet (Betavulgaris) and functionally characterized in tobacco (Nicotianatabacum) plants to assess the behavior of the transgenic organisms in the response to salt stress. The results showed that overexpression of BvNHX1 significantly enhanced salt tolerance in transgenic tobacco plants compared with wild-type (WT) plants. The seed germination, root length, plant height, and fresh and dry weights in transgenic plants were significantly higher than those in WT plants under salt stresses. The contents of leaf relative water, chlorophyll, proline, soluble sugars, and soluble proteins were significantly higher as compared with WT plants, while malondialdehyde (MDA) contents were significantly lower than those of WT plants under salt stresses. Na+ and K+ contents both in shoots and roots of transgenic plants were significantly higher than those of WT plants, and transgenic plants maintained a balanced K+/Na+ ratio under saline conditions. Taken together, these results suggested that overexpression of BvNHX1 reduced damage to cell membrane by reducing osmotic potential of cells, and maintaining relative water and chlorophyll contents of leaves, and finally improved salt tolerance in transgenic tobacco plants.

Salinity and drought are main threat to agriculture productivity, to avoid further losses it is necessary to improve the genetic material of crops against these stresses In this present study, AtNHX1, a vacuolar type Na+/H+ antiporter gene driven by 35S promoter was introduced into groundnut using Agrobacterium tumefaciens transformation system. The stable integration of the AtNHX1 gene was confirmed by polymerase chain reaction (PCR) and southern blot analysis. It was found that transgenic plants having AtNHX1 gene are more resistant to high concentration of salt and water deprivation than the wild type plants. Salt and proline level in the leaves of the transgenic plants were also much higher than that of wild type plants. The results showed that overexpression of AtNHX1 gene not only improved salt tolerance but also drought tolerance in transgenic groundnut. Our results suggest that these plants could be cultivated in salt and drought-affected soils.

A high salt environment seriously affects the physiological metabolism and yield of plants. (Trin.) Link has high biomass and important ecological, feeding and economic values, but its growth conditions have serious saline-alkali effects. The gene family plays a vital role in regulating intracellular Na /K balance, pH homeostasis, and vesicle and protein transport in plants. In this study, the gene was cloned from and functionally characterized through phenotypic, physiological, and molecular analyses in transgenic tobacco. Expression profiling revealed that was most abundant in spikes and least abundant in root tips, and the expression level was significantly induced under salt stress. Overexpression of led to decreased malondialdehyde (MDA) and superoxide anion (O ) levels, while it enhanced the activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT). Additionally, the levels of glutathione (GSH), soluble proteins, proline, and chlorophyll were also increased. Several stress-responsive genes, including , , , , , , , , , , , , and , were significantly upregulated, while was downregulated. These findings suggest that enhances plant salt tolerance by maintaining osmotic balance, scavenging reactive oxygen species (ROS), and regulating stress-responsive gene expression. This study provides new insights into the molecular mechanism of salt tolerance in and lays a foundation for breeding salt-tolerant forage crops.