Salt Tolerance

Soil salinization is a widespread hindrance that endangers agricultural production and ecological security. High salt concentrations in saline soils are primarily caused by osmotic stress, ionic toxicity and oxidative stress, which have a negative impact on plant growth and development. In order to withstand salt stress, plants have developed a series of complicated physiological and molecular mechanisms, encompassing adaptive changes in the structure and function of various plant organs, as well as the intricate signal transduction networks enabling plants to survive in high-salinity environments. This review summarizes the recent advances in salt perception under different tissues, physiological responses and signaling regulations of plant tolerance to salt stress. We also examine the current knowledge of strategies for breeding salt-tolerant plants, including the applications of omics technologies and transgenic approaches, aiming to provide the basis for the cultivation of salt-tolerant crops through molecular breeding. Finally, future research on the application of wild germplasm resources and muti-omics technologies to discover new tolerant genes as well as investigation of crosstalk among plant hormone signaling pathways to uncover plant salt tolerance mechanisms are also discussed in this review.

Chloride (Cl-) ions cause major damage to crops in saline soils. Understanding the key factors that influence Cl- uptake and translocation will aid the breeding of more salt-tolerant crops. Here, using genome-wide association study and transcriptomic analysis, we identified a NITRATE TRANSPORTER 1 (NRT1)/PEPTIDE TRANSPORTER family (NPF) protein, GmNPF7.5, as the dominant gene locus influencing Cl- homeostasis in soybean (Glycine max). A natural SNP variation resulted in two haplotypes (GmNPF7.5HapA and GmNPF7.5HapB), which was associated with Cl- content. GmNPF7.5HapA mediated Cl- or nitrate (NO3-) uptake in a pH-dependent manner and exhibited higher permeability for Cl- over NO3-. The suppression of GmNPF7.5HapA expression decreased Cl- accumulation and salt damage in plants, whereas its overexpression showed the opposite effects. The elite haplotype GmNPF7.5HapB diminished Cl- transport activity independently from NO3- permeability, thus enhancing soybean salt tolerance. Furthermore, the protein kinase GmPI4Kγ4 could phosphorylate GmNPF7.5, which repressed Cl- uptake without affecting NO3- permeability. Our findings define a regulatory mechanism for Cl- control under NaCl stress, providing a strategy for the improvement of salt tolerance in soybean plants.

Salt stress poses a significant challenge to plant growth and restricts agricultural development. To delve into the intricate mechanisms involved in soybean's response to salt stress and find targets to improve the salt resistance of soybean, this study integrated transcriptomic, proteomic, and metabolomic analyses to explore the regulatory networks involved in soybean salt tolerance. Transcriptomic analysis revealed significant changes in transcription factors, hormone-related groups, and calcium ion signaling. Notably, the biosynthetic pathways of cutin, suberine, and wax biosynthesis play an important role in this process. Proteomic results indicated salt-induced DNA methylation and the enrichment of phosphopyruvate hydrase post-salt stress, as well as its interaction with enzymes from various metabolic pathways. Metabolomic data unveiled the synthesis of various metabolites, including lipids and flavonoids, in soybean following salt stress. Furthermore, the integrated multiomics results highlighted the activation of multiple metabolic pathways in soybean in response to salt stress, with six pathways standing out prominently: stilbenoid, diarylheptanoid, and gingerol biosynthesis; carotenoid biosynthesis; carbon fixation in photosynthetic organisms; alanine, aspartate, and glutamate metabolism; thiamine metabolism; and pyruvate metabolism. These findings not only offer valuable insights into leveraging multiomics profiling techniques for uncovering salt tolerance mechanisms but also identify candidate genes for soybean improvement.

Halophytic plants harbour salt-tolerant bacteria that enhance resilience to salinity. In this study, two highly halotolerant Kushneria isolates, K. konosiri (Kk) and K. marisflavi (Km), were obtained from the halophyte Suaeda maritima. Both strains tolerated up to 25% NaCl and promoted Arabidopsis thaliana growth under salt stress by producing indole-3-acetic acid, proline, and extracellular polysaccharides that mitigated osmotic stress. Inoculation with Kk or Km increased shoot and root biomass and reduced intracellular Na⁺ and reactive oxygen species. Their agricultural potential was tested in cabbage (Brassica rapa), where both isolates alleviated salinity-induced growth inhibition. A combined inoculum (Kkm) showed enhanced efficacy, significantly increasing shoot biomass (1.26-fold vs. Kk; 1.23-fold vs. Km) and dry weight (1.19-fold vs. Kk; 1.13-fold vs. Km). Kkm treatment also improved the K⁺/Na⁺ ratio and proline accumulation. Microbial profiling revealed that Kkm enriched Bacillus species in the rhizosphere and promoted greater biofilm formation than single strains. These findings demonstrate that Kushneria isolates function as salt-tolerant plant growth-promoting bacteria, enhancing ion homoeostasis, stress protection, and rhizosphere restructuring. This study highlights the potential of halophyte-derived microbial consortia to improve crop salt tolerance in agriculture.