Search Results (168)

Soil salinity remains a major constraint to rice productivity, particularly during early developmental stages when plants are highly sensitive to osmotic and ionic stress. In this study, we evaluated 201 genetically diverse rice genotypes from the 3K Rice Diversity Panel to investigate stage-specific mechanisms of salinity tolerance and develop machine learning-based predictive models for rapid phenotypic screening. Morphological and physiological traits were measured under control and saline conditions at germination and early seedling stages to derive Stress Tolerance Indices (STIs). The average membership function value (AMFV), calculated from multi-trait STI profiles, effectively captured variation in salinity responses and enabled classification of genotypes into five tolerance categories. Genome-wide association analysis using high-density SNP markers identified 36 significant marker–trait associations, including potentially novel SNPs on chromosomes 1 and 12. Several loci co-localized with candidate genes (LTR1, LGF1, OsCPS4, OsNCX7, and OsNHX4), while functional SNPs within genes (OsDRP2C, RLCK168, and OsMed37_2) and non-synonymous variants (qSVII11.1 and qSNaK3.1) further supported their candidacy in salinity tolerance. Mining favourable SNPs of causal genes identified superior multilocus combinations consistent with STI-based phenotypic patterns, with genotype 91-382 emerging as the strongest performer, exhibiting enhanced Na⁺ exclusion, K⁺ retention, and biomass resilience across developmental stages. To address multicollinearity among STI traits, we applied cross-validated LASSO (germination) and Elastic Net (early seedling) models, achieving high predictive accuracy and revealing a developmental shift from biomass-driven tolerance at germination to ion-regulatory processes at the seedling stage. Independent validation showed strong agreement between predicted and observed AMFVs. By integrating physiological indices, GWAS-derived SNP signals, and regularized machine learning approaches, this study provides a robust framework for identifying elite donors and accelerating breeding for salt-tolerant rice. Full article

Background/Objectives: The NHX gene family plays a critical role in regulating ion homeostasis and enhancing plant tolerance to abiotic stresses. This study aimed to comprehensively analyze the structural, phylogenetic, and functional characteristics of the NHX gene family in the genome of Spinacia oleracea L. Methods: Through bioinformatic approaches, a total of 44 NHX genes were identified, and their chromosomal distribution, exon-intron organization, and conserved motifs were thoroughly characterized. Protein-protein interaction network analysis revealed that SoNHX14, SoNHX20, and SoNHX33 act as central regulators, playing key roles in cellular stress response mechanisms. Furthermore, the majority of SoNHX proteins were predicted to localize primarily to the plasma membrane, endoplasmic reticulum, and vacuole. Promoter analyses indicated a widespread presence of cis-acting elements responsive to stresses such as low temperature, drought, and wounding, as well as elements responsive to plant hormones, suggesting a complex and multilayered regulatory mechanism. Results: miRNA target predictions demonstrated that NHX genes are extensively regulated at the post-transcriptional level, predominantly by stress-associated miRNA families. Conclusions: These findings support a central role for the NHX gene family in abiotic stress adaptation in S. oleracea and provide a valuable foundation for future genetic interventions aimed at improving stress tolerance. Full article

Salinity stress severely limits rice productivity and grain quality worldwide. Although exogenous foliar application of titanium dioxide nanoparticles (nano-TiO₂) has been reported to enhance crop stress tolerance, its regulatory roles in yield formation and grain quality in rice varieties with differing salt tolerance are not well understood. In the present study, two contrasting rice varieties, viz., Jingliangyou 3261 (JLY3261; salt-tolerant) and Yuxiangyouzhan (YXYZ; salt-sensitive), were applied with five nano-TiO₂ foliar application treatments—viz., CK: water spray; Ti1: 15 mg L⁻¹; Ti2: 30 mg L⁻¹; Ti3: 45 mg L⁻¹; and Ti4: 60 mg L⁻¹—at the jointing and panicle initiation stages. Plants were irrigated with 0.3% saltwater to simulate salt stress. The results showed that Ti2 and Ti3 treatments led to 8.59% and 14.80% increases in grain yield in JLY3261 and YXYZ, respectively, compared with CK. Ti2 and Ti3 treatments significantly increased the leaf area index, net photosynthetic rate, and aboveground biomass of both varieties at the heading stage. Meanwhile, the activities of antioxidant enzymes such as superoxide dismutase and peroxidase, as well as nitrogen metabolism enzymes including nitrate reductase and glutamine synthetase, were improved with a substantial reduction in malondialdehyde contents. Application of nano-TiO₂ upregulated the expression of ion transport-related genes such as OsSOSs, OsNHXs and OsHKTs, thus improving leaf K⁺ accumulation and reducing Na⁺ content to optimize the K⁺/Na⁺ ratio. In addition, Ti2 and Ti3 treatments improved the milled rice rate, head rice rate, and protein content, while they decreased the chalkiness degree of both rice cultivars. Principal component analysis showed that the aboveground biomass at the heading stage was a core evaluation index for both varieties. Overall, foliar application of 30–45 mg L⁻¹ nano-TiO₂ was found to be effective regarding growth and yield improvement in rice under saline conditions. This study provides a theoretical basis for agro-management strategies for rice cultivation in saline–alkaline soils. Full article

In the context of global climate change, the co-occurrence of salt and heat stress represents a major constraint to rice production, resulting in greater yield penalties than either stress alone. This study aimed to assess the effects of salt and heat stress on oxidative homeostasis, photosynthetic performance, carbon (C)–nitrogen (N) metabolism, and rice yield. The experiment comprised four treatments, i.e., control (CK), salt (irrigation with 3.9 dS m⁻¹ NaCl solution), heat (exposure to 36 °C/30 °C day/night for 5 days at panicle initiation), and combined salt + heat stress. Results showed that combined stress enhanced reactive oxygen species (ROS) accumulation (i.e., H₂O₂ content and O₂⁻ contents were 1.3 and 1.5 times higher than CK), and the activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) were increased by 64.6%, 69.5%, and 74.8% higher than CK. At the molecular level, salt + heat stress upregulated antioxidant defense-related genes, i.e., OsAPX2, OsSODCC1, and OsAPX1, while significantly downregulated ion homeostasis-related genes, i.e., OsSOSs, OsHKT1;3, OsHKT1;5, and OsNHX4, and photosynthesis-related genes, i.e., Ospsbo, OsRbcS2, and OsRbcS3, compared with CK. Furthermore, salt + heat stress reduced the activities of C-metabolism enzymes (sucrose phosphate synthase, sucrose synthase, and starch synthase) and N-metabolism enzymes (nitrate reductase, glutamine synthetase, and glutamate synthase), leading to 34.3% and 18.6% lower stem-sheath non-structural carbohydrate accumulation in stem sheath and its translocation rate, respectively, while total N accumulation decreased by 42.9%, as compared with CK. Ultimately, these cascading effects inhibited panicle development and reduced yield. The findings provide a theoretical basis for improving rice tolerance to combined abiotic stresses by targeting oxidative stress mitigation, photosynthetic protection, and key stress-responsive gene regulation. Full article

Background/Objectives: Ziziphus jujuba var. spinosa (sour jujube) is a traditional medicinal plant with remarkable tolerance to abiotic stresses, particularly salinity. However, the regulatory mechanisms underlying its salt stress tolerance remain unclear. NHX genes play a crucial role in plant adaptation to salt stress by mediating Na⁺/K⁺ transport to maintain intracellular ion homeostasis and pH balance. Although the NHX gene family has been characterized in many plant species, its functional characteristics in sour jujube have not yet been systematically investigated. Methods: In this study, using Arabidopsis thaliana as a reference, we identified NHX genes in sour jujube through genome-wide analysis and molecular approaches, and systematically analyzed their phylogenetic relationships, chromosomal locations, conserved motifs, gene structures, cis-regulatory elements in promoter regions, and expression patterns under abiotic stresses, particularly salt stress. Results: The results revealed the presence of eight NHX genes distributed across six chromosomes in sour jujube, which were classified into three subfamilies: Vac-class, Endo-class, and PM-class. Members within the same evolutionary clade exhibited high structural conservation in motif composition and gene architecture. Except for the PM-class, all other clades contained amiloride-binding sites (FF(I/L)(Y/F)LFLLPPI). Analysis of cis-regulatory elements indicated that the promoter regions of these genes were enriched with elements related to defense responses, stress adaptation, and phytohormone signaling, further supporting their role in plant environmental adaptation. Additionally, the qRT-PCR analysis showed that most of the ZjNHX genes in both roots and leaves are up-regulated by salt. Notably, ZjNHX1 expression in roots increased approximately 40-fold within 3 h, whereas ZjNHX2 and ZjNHX3 were strongly induced in leaves under prolonged salt exposure. Conclusions: Taken together, this work gives a detailed overview of the ZjNHX genes and their important roles in response to salt stress in sour jujube. Our findings also provide a foundation for further functional characterization of this gene family. Full article

Lupinus angustifolius is an important leguminous ornamental species, but its productivity is often compromised by alkaline soil stress. GsEXPA8, an expansin gene identified in wild soybean (Glycine soja), has been implicated in alkali stress tolerance. In this study, we examined how heterologous expression of GsEXPA8 in lupinus affects its biochemical, molecular, and rhizospheric responses to alkali stress. Under NaHCO₃-induced alkaline conditions, transgenic lines overexpressing GsEXPA8 displayed improved leaf vigor, greater root biomass and length, elevated activities of antioxidant enzymes (CAT and POD), increased proline accumulation, and reduced malondialdehyde levels compared to the wild type. Expression analysis revealed time-dependent up-regulation of several alkali-responsive genes (LaSOS1, LaNCED3, LaMYB39, LaNAC56, LaNHX6, and LaP5CS). Moreover, the rhizosphere microbial community was significantly restructured, with a marked increase in beneficial microbial taxa such as Pseudomonas and Lysobacter. We also found that the endogenous lupinus homolog LaEXPA8 is alkali-inducible. Overexpression of LaEXPA8 similarly enhanced alkaline tolerance, whereas CRISPR/Cas9 knockout lines showed no clear phenotypic alteration, suggesting potential functional redundancy within the expansin family. Notably, LaEXPA8 and GsEXPA8 differed in their temporal regulation of downstream genes, indicating both conserved and distinct regulatory roles. Our results demonstrate that GsEXPA8 improves alkali tolerance in lupinus through integrated mechanisms: promoting root growth, enhancing antioxidant and osmotic adjustment capacity, dynamically modulating stress-related gene expression, and enriching beneficial rhizosphere microbiota. This work provides the critical report of modifying alkali tolerance by manipulating an expansin gene alongside the associated rhizosphere microbiome, offering a combined strategy for breeding stress-resistant ornamentals. Full article

Sweet potato (Ipomoea batatas L.) is a vital dual-use crop, with some varieties being used as leafy vegetables that are rich in anthocyanins. Nevertheless, salinity stress is a challenge to their production. Homeodomain-leucine zipper (HD-ZIP) gene family members encode proteins participating in the regulation of plant defense and secondary metabolism, while the functional study of HD-ZIP genes in sweet potato is still limited. Herein, a total of 66 IbHD-ZIP genes were identified, which were expanded by segmental duplication. Based upon promoter cis-element information and precedent evidence, IbHD-ZIP61, belonging to subfamily I, was selected for functional studies. Functional characterization was conducted via ectopic expression in transgenic Nicotiana benthamiana. The overexpression of IbHD-ZIP61 significantly increased anthocyanin production under normal growth conditions by promoting anthocyanin biosynthetic genes AN1a, AN2, and DFR. Furthermore, transgenic plants displayed better salinity tolerance, which exhibited reduced growth inhibition, increased water status, decreased oxidative injury, as well as elevated activity of antioxidant enzymes. This study validated the coordinated regulation of anthocyanin pathway genes as well as pivotal pathways (NHX2, NCED1, P5CS) during salinity adaptation. These findings demonstrate that IbHD-ZIP61 is a transcription factor linking anthocyanin synthesis and salinity adaptation, thus making it a potential candidate for improving breeding in nutritionally superior and salinity-adapted edible crops such as sweet potato. Full article

Salinity represents a major constraint on plant development and crop productivity in wheat, which represents one of the most critical sources of dietary calories worldwide. Its detrimental effects are particularly pronounced during the early stages of growth, including seed germination and seedling establishment. Salinity tolerance is a multifaceted trait governed by several interrelated mechanisms, notably ion homeostasis, osmotic adjustment, activation of enzymatic antioxidant systems, and transcriptional regulation of ion transporter genes. In the present study, contrasting wheat genotypes exhibiting differential salinity tolerance were selected from a panel of 172 accessions evaluated under salinity stress (175 mM NaCl) and control conditions (0 mM NaCl). The objectives of the current study are to confirm the underlying physiological and molecular mechanisms conferring salinity tolerance. Key physiological and molecular parameters including Na⁺, K⁺, and P homeostasis; activities of major antioxidant enzymes; and expression profiles of the salinity-responsive ion transporter genes TaAVP1 and NHX1 were quantified in six tolerant genotypes and one susceptible genotype. The tolerant genotypes exhibited higher concentrations of Na⁺ and K⁺ and elevated activities of all antioxidant enzymes, compared with the susceptible genotype. Furthermore, the tolerant genotypes showed differential expression of TaAVP1 and NHX1: both genes were upregulated in Javelin 48 and Kandahar, whereas they were downregulated in genotype 1018d. Notably, genotype Kule demonstrated the highest Na⁺ accumulation, accompanied by markedly elevated activities of all major antioxidant enzymes, with ascorbate peroxidase and glutathione reductase increasing by 9.20-fold and 2.32-fold, respectively, under salinity stress. Based on these findings, the tolerant genotypes can be categorized into two functional groups: Javelin 48, Ghati, and 1018d (characterized by high K⁺ and salinity tolerance) are better suited to soils affected by low Na⁺ salinity, whereas Kandahar, Kule, and 1049 (characterized by high Na⁺ and sodicity tolerance) are more adapted to soils with elevated Na⁺ levels. In conclusion, the tolerant genotypes exhibited distinct, coordinated mechanisms to mitigate salinity stress, underscoring the complexity and plasticity of adaptive responses in wheat. Full article

Soil salinization poses a significant threat to global agricultural productivity. Among crops, soybean (Glycine max), an important source of oil and protein, is more susceptible to salt stress compared to other major crops such as wheat (Triticum aestivum) and rice (Oryza sativa). To better utilize saline land resources, understanding the mechanisms underlying salt tolerance in soybean is essential for developing new salt-tolerant soybean varieties that contribute to food security. This review synthesizes current knowledge on the molecular mechanisms of salt tolerance in soybean, with a focus on ion homeostasis, osmotic adjustment, oxidative balance restoration, structural adaptations, and transcriptional regulatory networks. Key findings highlight the critical roles of ion transporters—such as GmNHX1, GmSOS1, GmHKT1, and GmCLC1—in maintaining Na⁺/K⁺ and Cl⁻ balance; the accumulation of osmoprotectants like proline and LEA proteins to alleviate osmotic stress; and the activation of antioxidant systems—including SOD, CAT, and APX—to scavenge reactive oxygen species (ROS). Additionally, structural adaptations, such as salt gland-like features observed in wild soybean (Glycine soja), and transcriptional regulation via ABA-dependent and independent pathways (e.g., GmDREB, GmbZIP132, GmNAC) further enhance tolerance. Despite these advances, critical gaps remain regarding Cl⁻ transport mechanisms, rhizosphere microbial interactions, and the genetic basis of natural variation in salt tolerance. Future research should integrate genomic tools, omics-based breeding, genome editing techniques such as CRISPR-Cas9, microbial technologies, and traditional breeding methods to develop salt-tolerant soybean varieties, providing sustainable solutions for the utilization of saline–alkali soils and enhancing global food security. Full article

A high salt environment seriously affects the physiological metabolism and yield of plants. Hordeum brevisubulatum (Trin.) Link has high biomass and important ecological, feeding and economic values, but its growth conditions have serious saline-alkali effects. The NHX 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 HbNHX2 gene was cloned from Hordeum brevisubulatum and functionally characterized through phenotypic, physiological, and molecular analyses in transgenic tobacco. Expression profiling revealed that HbNHX2 was most abundant in spikes and least abundant in root tips, and the expression level was significantly induced under salt stress. Overexpression of HbNHX2 led to decreased malondialdehyde (MDA) and superoxide anion (O²⁻) 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 CBL1, ERF2, BI-1, Cu/Zn-SOD, Mn-SOD, POD, GR1, KC1, TPK1, TIP, P5CS, BAS1, STN7 and LTP1, were significantly upregulated, while SERK3B was downregulated. These findings suggest that HbNHX2 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 Hordeum brevisubulatum and lays a foundation for breeding salt-tolerant forage crops. Full article

Soil salinity is a serious abiotic stressor threatening global agriculture, currently affecting nearly 20% of irrigated land, with projections suggesting that almost 50% of cultivated areas may be impacted by 2050. Plant growth-promoting rhizobacteria (PGPR) and Silicon (Si) have been widely investigated for their individual roles in improving plant tolerance to salinity, yet their combined application—particularly using Si nanoparticles (SiNPs), remains underexplored. This review synthesizes current knowledge on PGPR, SiNPs, and their synergistic effects in mitigating salinity stress, with emphasis on physiological, biochemical, and molecular mechanisms. Special attention is given to Si-mediated regulation of stress-responsive genes (e.g., RD29B, DREB2b, RAB18, HKT1, WRKY TFs, CAT, POD) and PGPR-induced gene expression (e.g., GmST1, GmLAX3, NHX1, NRT2.2, GR), which are directly linked to ion homeostasis, osmolyte accumulation, and antioxidant activation. In addition, crop-specific case studies and emerging molecular insights are highlighted to demonstrate practical applications. Despite these promising findings, significant challenges remain, including the stability of nanoformulations, microbial compatibility, and the lack of field-scale validation under diverse agro-climatic conditions. This review highlights knowledge gaps and briefly outlines future directions for the integrated use of PGPR and SiNPs as sustainable strategies to enhance crop resilience under salinity stress. Full article

Salt stress represents one of the most critical abiotic constraints limiting global agricultural productivity by adversely affecting plant growth, metabolism, and yield. Soil salinization disrupts water uptake and nutrient homeostasis, leading to ionic toxicity, osmotic imbalance, and oxidative stress that collectively impair crop development. Cucumis melo, a major horticultural crop of significant economic value, exhibits high sensitivity to salinity. Recent advances have elucidated that melon adapts to salt stress through intricate physiological and molecular mechanisms involving osmotic adjustment, ion transport regulation, antioxidant defense, and transcriptional reprogramming. Several pivotal genes, such as CmNHX1, CmHKT1;1, CmCML13, CmAPX27, and CmRAV1, etc., have been identified to participate in multiple signaling pathways governing salt tolerance in melon. In this review, we comprehensively summarize the physiological effects of salt stress on melon growth, elucidating the key molecular mechanisms underlying salt tolerance, particularly those associated with ion homeostasis, antioxidant defense, and transcriptional regulation. The review further discusses current strategies and future perspectives for the genetic improvement of salt tolerance. Collectively, this review provides a theoretical framework and valuable reference for future research on the molecular basis of salt tolerance and breeding of salt-tolerant melon cultivars. Full article

Mitogen-Activated Protein Kinases (MAPKs) play crucial roles in plant stress signaling, but the mechanisms of MAPK genes in Portulaca oleracea remain functionally uncharacterized. In this study, transcriptomic screening of P. oleracea under salt stress identified PoMPK3 as a candidate gene, showing significant root-specific upregulation. Phylogenetic analysis classified it as a Group A MAPK protein, and subcellular localization confirmed its membrane association. Heterologous expression of PoMPK3 in Arabidopsis thaliana significantly enhanced salt tolerance, as evidenced by improved seed germination rates, longer primary roots, increased biomass, and reduced stress symptoms. Mechanistically, PoMPK3 expression activated ABA signaling, leading to increased ABA levels and upregulation of AtNCED3, AtPYR1, and AtABF3. Furthermore, it strengthened the antioxidant defense, as evidenced by elevated antioxidant enzyme activity, leading to a reduction in oxidative stress. The transgenic lines also demonstrated enhanced osmotic adjustment through osmolytes accumulation and ionic homeostasis, evidenced by tissue-specific Na⁺/K⁺ ratios (low in shoots, high in roots) resulting from the concerted upregulation of AtSOS1, AtNHX1, and AtHKT1. In addition, gene co-expression network analysis and molecular docking predicted phosphorylation of WRKY transcription factors, suggesting a novel mechanism for transcriptome reprogramming. Collectively, our findings not only advance the understanding of salt tolerance mechanisms in purslane but also identify PoMPK3 as a key genetic determinant, thereby laying the foundation for its use in breeding programs aimed at enhancing salt stress resilience in crops. Full article

This study investigated how exogenous 2,4-epibrassinolide (EBR) and nitric oxide (NO) enhance the tolerance of cucumber (Cucumis sativus L.) seedlings to NaHCO₃-induced alkaline stress under hydroponic conditions. NaHCO₃ exposure caused severe sodium toxicity, reactive oxygen species (ROS) accumulation, and photosynthetic inhibition, which, together, suppressed plant growth. Treatments with either EBR or NO significantly improved plant performance by alleviating these adverse effects. Both regulators enhanced the ROS scavenging system, maintained ionic homeostasis, and alleviated sodium toxicity. They also stimulated the activities of vacuolar H⁺-ATPase, H⁺-PPase, and plasma membrane H⁺-ATPase, and increased the accumulation of citric and malic acids, thereby sustaining higher photosynthetic efficiency under stress conditions. qRT-PCR analysis further revealed that EBR and NO upregulated SOS1 and NHX2 (sodium transporters) as well as PIP1;2 and PIP2;4 (aquaporins), confirming their involvement in ionic and osmotic regulation. Pharmacological experiments showed that application of NO synthesis inhibitors, including tungstate and L-NAME, as well as the NO scavenger cPTIO, markedly weakened the protective effects of EBR. In contrast, application of the brassinosteroid biosynthesis inhibitor brassinazole (BRz) only had a limited effect on NO-mediated stress tolerance. Collectively, these findings demonstrate that NO functions as a downstream signaling mediator of EBR, coordinating multiple defense pathways including photosynthetic regulation, antioxidant protection, ion balance, aquaporin activity, and organic acid metabolism to enhance cucumber resistance to alkaline stress. Full article

Plant vacuolar-type Na⁺, K⁺/H⁺ antiporters (NHXs) play important roles in pH and K⁺ homeostasis and osmotic balance under normal physiological conditions. Under salt stress, vacuolar-type NHX enhances salt tolerance by compartmentalizing Na⁺ into vacuoles. However, the ion transport mechanism of vacuolar-type NHX remains poorly understood due to the absence of resolved protein crystal structures. To investigate the ion transport mechanism for vacuolar-type NHX, the three-dimensional structure of rice vacuolar-type NHX1 (OsNHX1) was established through homology modeling and AlphaFold3.0. The OsNHX1 model contains thirteen transmembrane segments according to hydrophobic characteristics and empirical and phylogenetic data. Furthermore, this study validated the OsNHX1 model via functional experiments, revealing a set of key charged amino acids essential for its activity. Mapping these amino acids onto the OsNHX1 model revealed that its pore domain exhibits a transmembrane charge-compensated pattern similar to that of NHE1 while also displaying a distinct charge distribution on either side of the pore domain. Comparative analysis of the key amino acid sites responsible for ion transport in the crystal structure of OsSOS1 and NHE1 revealed that OsNHX1 employs a unique ion transport mechanism. This study will enhance our understanding of the function and catalytic mechanism of OsNHX1 and other plant vacuolar-type NHXs. Full article