Improving Wheat Salt Tolerance for Saline Agriculture

Enhanced salt tolerance in Synechocystis sp. PCC 6803 through adaptive evolution: Mechanisms and applications for environmental bioremediation

As a significant environmental challenge, salt stress is common in saline-alkali soils and brackish water, where elevated salt levels hinder the growth of various organisms. Cyanobacteria are ideal models for studying adaptations to salt stress due to their wide distribution across aquatic and terrestrial ecosystems. In this study, we employed adaptive laboratory evolution to increase the salt (NaCl) tolerance of the model cyanobacterium Synechocystis sp. PCC 6803 from 4.0 % to 6.5 % (w/v). Through genome re-sequencing and mutant analysis, six key genes associated with salt tolerance were identified. Notably, overexpression of the slr1753 gene enhanced Na⁺ accumulation on the cell surface, enabling the engineered strain to effectively reduce Na⁺ concentration in seawater by 6.4 %. Additionally, the adapted strain showed promise in remediating saline-alkali soils, with observed increases in the germination rate (184.2 %) and average height (43.8 %) of Brassica rapa chinensis. Soil quality also improved, with a 25.3 % increase in total organic carbon content, a 1.8 % reduction in total salt content, and a 1.9 % decrease in pH. This study provides new insights into the mechanisms underlying salt tolerance and highlights the potential of engineered cyanobacteria for bioremediation in high-salinity environments.

Biosynthesized Fe-C-dots nanozymes modulate growth, physiological and phytochemical peculiarity to improve saline-alkaline stress tolerance in wheat

Nanotechnology has shown great potential to improve agricultural production and increase crop tolerance to abiotic stresses, including saline-alkaline environments. This study focuses on the biological mechanism of biocompatible iron-doped carbon dots (Fe-C-dots) nanozyme biosynthesized from artemisinin extract to alleviate saline-alkaline stress in wheat (Triticum aestivum L.). Particularly, Fe-C-dots with two types of natural enzyme mimicking properties, target reactive oxygen species (ROS) to assuage oxidative damage and to enhance the antioxidant capacity of enzyme-activated systems. Exogenous application of Fe-C-dots (50 mg/L) significantly promoted wheat growth and increased photosynthetic pigment content and photosynthetic efficiency. At the molecular level, Fe-C-dots treatment activated the nitrogen metabolism pathway of roots, up-regulated the expression of related genes OsNRT2.1, OsGS1, and NADH-GOGAT, and promoted the accumulation of nitrogen in wheat. Transcriptomics and metabolomics analyses reveal that Fe-C-dots triggered metabolic and transcriptional reprogramming in wheat seedlings. Besides, Fe-C-dots activated stress signaling and defense-related pathways, such as plant hormone signal transduction, MAPK, and photosynthesis signaling pathways, the cutin, suberin, wax, flavonoids, and phenolic acids biosynthesis. Importantly, compared to the control group, the application of Fe-C-dots under saline-alkaline stress increased the net photosynthetic rate (Pn) and transpiration rate (Tr) in wheat shoots by 77.5 %, and 78.6 %, respectively. These findings suggested that Fe-C-dots can improve root nitrogen metabolism and stem photosynthesis of wheat, as well as the synthesis of related stress-resistant compounds to cope with the damage of saline-alkaline stress on wheat growth. However, further studies are needed to explore the effectiveness of Fe-C-dots in wheat yield and quality evaluation.

LbHKT1;1 Negatively Regulates Salt Tolerance of Limonium bicolor by Decreasing Salt Secretion Rate of Salt Glands

The HKT-type proteins have been extensively studied and have been shown to play important roles in long-distance Na+ transport, maintaining ion homoeostasis and improving salt tolerance in plants. However, there have been no reports on the types, characteristics and functions of HKT-type proteins in Limonium bicolor, a recretohalophyte species with the typical salt gland structure. In this study, five LbHKT genes were identified in L. bicolor, all belonging to subfamily 1 (HKT1). There are many cis-acting elements related to abiotic/biotic stress response on the promoters of the LbHKT genes. LbHKT1;1 was investigated in detail. Subcellular localization results showed that LbHKT1;1 is targeted to the plasma membrane. Functional analysis in yeast showed that LbHKT1;1 has a higher tolerance than AtHKT1;1 under high Na+ conditions. Silencing and overexpression of the LbHKT1;1 gene in L. bicolor showed that LbHKT1;1 negatively regulates salt secretion by the salt glands. Further experiments showed that LbbZIP52 can specifically bind to the ABRE element in the LbHKT1;1 promoter and regulate the expression of the LbHKT1;1 gene and is involved in the negative regulation of the salt secretion capacity of L. bicolor. This study demonstrates for the first time that the HKT-type protein is involved in salt secretion by salt glands and provides a new perspective on the function of HKT-type proteins under salt stress conditions.

Glycolysis and signal transduction participate in Lycium barbarum in response to NaCl stress through protein phosphorylation

BACKGROUND

Lycium barbarum L. possesses great salt tolerance and medicinal values, studying its salt tolerance contribute to variety improvement, as well as the increase in yield and quality.

RESULTS

The study integrated the tandem mass tags (TMT) phosphoproteomics and physiological indexes of L. barbarum exposed to different concentrations of NaCl, with the aim of characterizing salt adaptation characteristics of L. barbarum. The findings indicated that a total of 2189 differentially phosphorylated peptides were identified, functional analysis revealed their involvement in glycolysis, plant hormone signal transduction, mitogen-activated protein kinase (MAPK) signal transduction and other pathways, and that the enzyme activities and substances related to glycolysis and signal transduction underwent significant changes under salt stress.

CONCLUSION

Salt stress enhanced the glycolysis pathway through protein phosphorylation, and the changes in related enzymes activity accelerated the conversion of intermediate metabolites and energy supply. Salt stress led to the accumulation of abscisic acid (ABA), jasmonic acid (JA), and salicylic acid (SA) levels, triggering signal transduction events regulated by phosphorylated proteins to improve salt tolerance for L. barbarum in saline environments. The phosphorylation of MAPK signaling pathway-related proteins is triggered by reactive oxygen species (ROS) and ABA as signal molecules to induce the expression of downstream salt stress response factors. This study provides a foundation for further analysis of the molecular regulatory mechanism of protein phosphorylation in L. barbarum for salt stress.

Physiological and transcriptional analysis provides insights into responses of a spring wheat variety to combination of salt and heat stresses

Enhancing the frequency and intensity of extreme high temperature conditions due to global warming largely deteriorates salt-induced harm to the crop plants living in saline lands, which leads to losses of agricultural production. In northern China, spring wheat is grown in many slightly saline areas and often subjected to a combination of salt and heat stresses. In this study, a spring wheat cultivar was selected as the experimental material and subjected to salt stress (S), heat stress (H) and their combination (S + H). Physiological analysis showed that the inhibitory effect of S + H stress on wheat growth was much stronger than that of individual salt stress due to aggravating Na+ toxicity caused by heat stress. We observed that many genes involved in plant hormones showed much higher expression under S + H stress than under salt stress and heat stress, including key ABA synthesis genes (NCEDs), core ABA signalling transduction genes, key ethylene synthesis genes, and core ethylene signalling transduction genes. Particularly, many ABA-responsive genes (HSFs, HSPs, DHNs and LEAs) were upregulated under S + H stress but not under salt stress and heat stress. DHNs and LEAs were identified to play an important role in preventing cytoplasmic dehydration, protein aggregation, and slowing Na+ migration, and ethylene was identified to contribute to Na+ detoxification. We propose that in response to S + H stress, wheat plants regulate the expression of DHNs, LEAs, HSPs and HSFs via the ABA pathway to prevent cell dehydration and protein aggregation and keep ion homeostasis via the ethylene pathway.

Synergistic Remediation of Cadmium Pollution in Saline-Alkali Soil by Hydrogel and Suaeda salsa

The cadmium (Cd) in saline-alkali soil poses a serious threat to the ecological environment and human health. Suaeda salsa, as a hyperaccumulator plant, can remediate Cd in saline-alkali soil, but the efficiency of phytoremediation is low. To improve the remediation effect of Cd pollution in saline-alkali soil, this study for the first time uses the synergy of hydrogel and Suaeda salsa for the remediation of Cd in saline-alkali soil. Hydrogel possesses excellent mechanical properties and outstanding adsorption properties. In addition, the hydrogel increases the content of some nutrient elements in the soil and improves the physicochemical properties of the soil. The water retention capacity of the hydrogel and the improvement of the physicochemical properties of the soil further promote the growth of Suaeda salsa. Meanwhile, both the hydrogel and Suaeda salsa have a positive impact on microorganisms. Our experiment provides a brand-new way for the remediation of Cd pollution in saline-alkali soil and is of great significance for soil health and ecological protection.

RNA sequencing and functional analysis uncover key long non-coding RNAs involved in regulating pollen fertility during the process of gametocidal action in wheat

Gametocidal (Gc) chromosomes have been widely utilized in genetic breeding due to their ability to induce chromosomal breakage and eliminate gametes that lack them. Long noncoding RNAs (lncRNAs) have various functional mechanisms in regulating pollen and anther development; however, their regulatory contributions to Gc action are still unknown. Here, we identified 2824 differentially expressed lncRNAs (DE-lncRNAs) from the anther tissues of Triticum aestivum cv. Chinese Spring (CS) and Chinese Spring-Gc 3C chromosome monosomic addition line (CS-3C) through sequencing. In this study, we predicted 161 target mRNAs for 145 DE-lncRNAs, including 104 cis-regulatory, 60 trans-regulatory, and three both cis-regulatory and trans-regulatory manner. Combined with our previous miRNA sequencing data, 241 DE-lncRNAs functioned as potential endogenous target mimics (eTMs) for 84 differentially expressed microRNAs (DE-miRNAs, including 12 novel miRNAs). The results of transient transformation in tobacco leaves indicated that L006278 could bind to MTCONS_00006277, which encoded a calcineurin CBL-interacting protein kinase 19-like, and suppress its expression. Furthermore, L117735 could function as an eTM for tae-miR9657b-3p, and L056972 could function as an eTM for gc-m2240-5p. To explore the function of lncRNAs in the process of Gc action, we transformed L006278, an up-regulated lncRNA in CS-3C, into rice to analyze its effect on pollen fertility. Overexpression of L006278 led to a reduction in rice pollen fertility. Overall, our findings indicate that lncRNAs can contribute to the regulation of pollen fertility during the process of Gc action by regulating the expression levels of target mRNAs and acting as eTMs for certain key miRNAs.

Salt tolerance in wheat is associated with the maintenance of shoot biomass, stomatal conductance, and sucrose in the phloem

Wheat (Triticum aestivum L.) is a mega-staple for millions of the world's populations and its yield potential is impacted by soil salinization. This study investigated genotypic variation in salt tolerance among six wheat genotypes, Gladius, Drysdale, GD0014, GD0120, GD0180, and GD0185. The study also characterized shoot traits, photosynthetic traits, leaf Na and K concentrations, and phloem sucrose. The plants were grown under controlled growth room conditions at 0 mM NaCl (Control) and 100 mM NaCl. The results showed that the salt tolerance index (STISFW, SFW: shoot fresh weight) varied from 0.52 for GD0120 to 0.69 for GD0180. Based on the STISFW, salt tolerance for the wheat genotypes was in the order, GD0180 > Gladius > GD0185 > Drysdale > GD0014 > GD0120. Projected shoot area (PSA) at all growth stages, 14, 20, 27, 34, and 40 DAS were strongly correlated with SFW at 45 DAS. Salt treatment significantly increased phloem sucrose level in the salt intolerant, Drysdale, while having no effect on this parameter in Gladius. Gladius showed greater maintenance of stomatal conductance than Drysdale. The relative ratio of K/Na between treatment and control was strongly correlated with the relative ratio of SFW (r = .85). The correlation between PSA at 14 DAS and SFW at 45 DAS and the correlation between the relative ratio of K/Na between treatment and control with STISFW identify these parameters to be potential traits for screening salt tolerance in wheat. Higher salt tolerance in Gladius would be associated with higher maintenance of stomatal conductance and enhanced phloem sucrose transport.

Insights into Salinity Tolerance in Wheat

Salt stress has a detrimental impact on food crop production, with its severity escalating due to both natural and man-made factors. As one of the most important food crops, wheat is susceptible to salt stress, resulting in abnormal plant growth and reduced yields; therefore, damage from salt stress should be of great concern. Additionally, the utilization of land in coastal areas warrants increased attention, given diminishing supplies of fresh water and arable land, and the escalating demand for wheat. A comprehensive understanding of the physiological and molecular changes in wheat under salt stress can offer insights into mitigating the adverse effects of salt stress on wheat. In this review, we summarized the genes and molecular mechanisms involved in ion transport, signal transduction, and enzyme and hormone regulation, in response to salt stress based on the physiological processes in wheat. Then, we surveyed the latest progress in improving the salt tolerance of wheat through breeding, exogenous applications, and microbial pathways. Breeding efficiency can be improved through a combination of gene editing and multiple omics techniques, which is the fundamental strategy for dealing with salt stress. Possible challenges and prospects in this process were also discussed.

Uncovering key salt-tolerant regulators through a combined eQTL and GWAS analysis using the super pan-genome in rice

For sessile plants, gene expression plays a pivotal role in responding to salinity stress by activating or suppressing specific genes. However, our knowledge of genetic variations governing gene expression in response to salt stress remains limited in natural germplasm. Through transcriptome analysis of the Global Mini-Core Rice Collection consisting of a panel of 202 accessions, we identified 22 345 and 27 610 expression quantitative trait loci associated with the expression of 7787 and 9361 eGenes under normal and salt-stress conditions, respectively, leveraging the super pan-genome map. Notably, combined with genome-wide association studies, we swiftly pinpointed the potential candidate gene STG5-a major salt-tolerant locus known as qSTS5. Intriguingly, STG5 is required for maintaining Na+/K+ homeostasis by directly regulating the transcription of multiple members of the OsHKT gene family. Our study sheds light on how genetic variants influence the dynamic changes in gene expression responding to salinity stress and provides a valuable resource for the mining of salt-tolerant genes in the future.

Designing salt stress-resilient crops: Current progress and future challenges

Excess soil salinity affects large regions of land and is a major hindrance to crop production worldwide. Therefore, understanding the molecular mechanisms of plant salt tolerance has scientific importance and practical significance. In recent decades, studies have characterized hundreds of genes associated with plant responses to salt stress in different plant species. These studies have substantially advanced our molecular and genetic understanding of salt tolerance in plants and have introduced an era of molecular design breeding of salt-tolerant crops. This review summarizes our current knowledge of plant salt tolerance, emphasizing advances in elucidating the molecular mechanisms of osmotic stress tolerance, salt-ion transport and compartmentalization, oxidative stress tolerance, alkaline stress tolerance, and the trade-off between growth and salt tolerance. We also examine recent advances in understanding natural variation in the salt tolerance of crops and discuss possible strategies and challenges for designing salt stress-resilient crops. We focus on the model plant Arabidopsis (Arabidopsis thaliana) and the four most-studied crops: rice (Oryza sativa), wheat (Triticum aestivum), maize (Zea mays), and soybean (Glycine max).

Genome-wide identification and expression pattern analysis of the kiwifruit GRAS transcription factor family in response to salt stress

BACKGROUND

GRAS is a family of plant-specific transcription factors (TFs) that play a vital role in plant growth and development and response to adversity stress. However, systematic studies of the GRAS TF family in kiwifruit have not been reported.

RESULTS

In this study, we used a bioinformatics approach to identify eighty-six AcGRAS TFs located on twenty-six chromosomes and phylogenetic analysis classified them into ten subfamilies. It was found that the gene structure is relatively conserved for these genes and that fragmental duplication is the prime force for the evolution of AcGRAS genes. However, the promoter region of the AcGRAS genes mainly contains cis-acting elements related to hormones and environmental stresses, similar to the results of GO and KEGG enrichment analysis, suggesting that hormone signaling pathways of the AcGRAS family play a vital role in regulating plant growth and development and adversity stress. Protein interaction network analysis showed that the AcGRAS51 protein is a relational protein linking DELLA, SCR, and SHR subfamily proteins. The results demonstrated that 81 genes were expressed in kiwifruit AcGRAS under salt stress, including 17 differentially expressed genes, 13 upregulated, and four downregulated. This indicates that the upregulated AcGRAS55, AcGRAS69, AcGRAS86 and other GRAS genes can reduce the salt damage caused by kiwifruit plants by positively regulating salt stress, thus improving the salt tolerance of the plants.

CONCLUSIONS

These results provide a theoretical basis for future exploration of the characteristics and functions of more AcGRAS genes. This study provides a basis for further research on kiwifruit breeding for resistance to salt stress. RT-qPCR analysis showed that the expression of 3 AcGRAS genes was elevated under salt stress, indicating that AcGRAS exhibited a specific expression pattern under salt stress conditions.

Germination and First Stages of Growth in Drought, Salinity, and Cold Stress Conditions of Plasma-Treated Barley Seeds

Numerous works have demonstrated that cold plasma treatments constitute an effective procedure to accelerate seed germination under nonstress conditions. Evidence also exists about a positive effect of plasmas for germination under environmental stress conditions. For barley seeds, this work studies the influence of cold plasma treatments on the germination rate and initial stages of plant growth in common stress environments, such as drought, salinity, and low-temperature conditions. As a general result, it has been found that the germination rate was higher for plasma-treated than for untreated seeds. Plasma also induced favorable changes in plant and radicle dimensions, which depended on the environment. The obtained results demonstrate that plasma affects the biochemical metabolic chains of seeds and plants, resulting in changes in the concentration of biochemical growing factors, a faster germination, and an initially more robust plant growth, even under stress conditions. These changes in phenotype are accompanied by differences in the concentration of biomarkers such as photosynthetic pigments (chlorophylls a and b and carotenoids), reactive oxygen species, and, particularly, the amino acid proline in the leaves of young plants, with changes that depend on environmental conditions and the application of a plasma treatment. This supports the idea that, rather than an increase in seed water imbibition capacity, there are clear beneficial effects on seedling of plasma treatments.