Salt-stressed Plants Research Articles

Enhancement of heat tolerance by salt stress in Tetraselmis striata CTP4: impacts on HSP gene expression, pigments, and proximal composition

AbstractAs the world average temperature is on the rise and heat waves are becoming more prevalent, microalgal producers have been facing significant challenges regarding the time periods during which they are able to grow less thermotolerant microalgae in outdoor production facilities. Therefore, it is urgent to explore how microalgae cope with thermal stress and under which growth conditions tolerance to temperatures close to or higher than their maximum thermal threshold is induced. For this purpose, Tetraselmis striata CTP4, a euryhaline microalga known for its thermotolerance, was selected. Tetraselmis striata belongs to the Chlorodendrophyceae, a clade that branched off early from other "core chlorophyte" clades, usually comprised of microalgae able to colonise freshwater habitats. Here, we present compelling evidence that the ability of this microalga to withstand otherwise lethal thermal upshifts to 40 °C is induced by exposure to higher salinity (35 ppt). In contrast, this response is abrogated at lower salinities. Concomitantly, the expression of genes encoding HSP70 and HSP100, two heat shock proteins known to mediate thermotolerance and tolerance to other stresses (e.g., salt stress) in fungi, animals and plants, was enhanced when exposed to both heat stress and higher salinities. This suggests that cross-protective mechanisms against abiotic stress appeared early during the evolution of the core chlorophytes and of Archaeplastida in general. This knowledge can be used to select novel strains and growth conditions that promote thermotolerance in microalgae that are grown in outdoor industrial production facilities in environments where heat waves are expected.

AtDGCR14L contributes to salt‐stress tolerance via regulating pre‐mRNA splicing in Arabidopsis

SUMMARYIn plants, pre‐mRNA alternative splicing has been demonstrated to be a crucial tier that regulates gene expression in response to salt stress. However, the underlying mechanisms remain elusive. Here, we studied the roles of DIGEORGE‐SYNDROME CRITICAL REGION 14‐like (AtDGCR14L) in regulating pre‐mRNA splicing and salt stress tolerance. We discovered that Arabidopsis AtDGCR14L is required for maintaining plant salt stress tolerance and the constitutively spliced and active isoforms of important stress‐ and/or abscisic acid (ABA)‐responsive genes. We also identified the interaction between AtDGCR14L and splicing factor U1‐70k, which needs a highly conserved three amino acid (TWG) motif in DGCR14. Different from wild‐type AtDGCR14L, the overexpression of the TWG‐substituted AtDGCR14L mutant did not change salt stress tolerance or pre‐mRNA splicing of stress/ABA‐responsive genes. Additionally, SWITCH3A (SWI3A) is a core subunit of the SWI/SUCROSE NONFERMENTING (SWI/SNF) chromatin‐remodeling complexes. We found that SWI3A, whose splicing depends on AtDGCR14L, actively enhances salt stress tolerance. These results revealed that AtDGCR14L may play an essential role in crosstalk between plant salt‐stress response and pre‐mRNA splicing mechanisms. We also unveiled the potential role of SWI3A in controlling salt stress tolerance. The TWG motif in the intrinsically disordered region of AtDGCR14L is highly conserved and crucial for DGCR14 functions.

Brassinosteroids Alleviate Salt Stress by Enhancing Sugar and Glycine Betaine in Pepper (Capsicum annuum L.)

Salt stress is a major abiotic factor that negatively impacts the growth, performance, and secondary metabolite production in pepper (Capsicum annuum L.) plants. Brassinosteroids (BRs) play a crucial role in enhancing plant tolerance to abiotic stress, yet their potential in mitigating salt stress in pepper plants, particularly by promoting sugar and glycine betaine accumulation, remains underexplored. In this study, we investigated the effects of the foliar application of 2,4-epibrassinolide (EBR) on salt-stressed pepper seedlings. Our findings revealed that EBR treatment significantly increased the levels of proline, sugar, and glycine betaine under salt stress compared to untreated controls. Moreover, EBR enhanced the antioxidant defense mechanisms in pepper seedlings by increasing sugar and glycine betaine levels, which contributed to the reduction of reactive oxygen species (ROS) and malondialdehyde (MDA) accumulation.

γ-Aminobutyric Acid Alleviates Salinity-Induced Impairments in Rice Plants by Improving Photosynthesis and Upregulating Osmoprotectants and Antioxidants

Salt stress is a significant abiotic stress that hinders the growth of rice (Oryza sativa L.) and reduces their yield. Previous research has examined the synthesis of γ-aminobutyric acid (GABA) and its role in plant resistance under various abiotic stresses. However, the synthesis of GABA and its ability to mitigate damage caused by salt stress—particularly its effects on osmotic adjustment, antioxidant defense, photosynthesis, and overall plant growth throughout the entire rice lifecycle—remains unclear. Therefore, we conducted two experiments using salt-tolerant rice cultivar Lianjian 5 (J-5) and salt-susceptible cultivar Lianjing 7 (L-7). In Experiment I, RNA-seq (RNA sequencing) was used to analyze the differential expression of the transcriptome between CK and salinity treatments, revealing the key roles of GABA in salt tolerance. In Experiment II, different levels of exogenous GABA were applied to salt-stressed plants to investigate its physiological role in enhancing salt tolerance. Therefore, RNA-seq (RNA sequencing) was used to analyze the differential expression of the transcriptome between CK and salinity treatments, revealing the key roles of GABA in salt tolerance. Subsequently, different levels of exogenous GABA were applied to salt-stressed plants to investigate its physiological role in enhancing salt tolerance. We measured the activities of superoxide dismutase, peroxidase, and catalase, as well as photosynthetic characteristics such as photosynthesis, transpiration, chlorophyll content, stomatal density and size, and leaf anatomical features. The RNA-seq analysis revealed that GABA production is enhanced via the glutamate decarboxylase (GAD) gene (LOC4333932) in the salt-resistant rice cultivar. Exogenous GABA application improves salt-stress tolerance by increasing endogenous ABA and GABA contents, which enhance osmotic adjustment, boost antioxidant defenses, and regulate ion balance. These combined effects help maintain photosynthetic efficiency and support overall plant growth under salt-stressed environments. Additionally, the increased proportion of mesophyll cell periphery covered by chloroplasts (Sc/Sm) indicated enhanced mesophyll conductance. These helped maintain photosynthesis under saline conditions while reducing water consumption.

Visualizing plant salt stress with a NaCl-responsive fluorescent probe

Visualizing plant salt stress with a NaCl-responsive fluorescent probe

Profiling of Key Hub Genes Using a Two-State Weighted Gene Co-Expression Network of 'Jao Khao' Rice under Soil Salinity Stress Based on Time-Series Transcriptome Data.

RNA-sequencing enables the comprehensive detection of gene expression levels at specific time points and facilitates the identification of stress-related genes through co-expression network analysis. Understanding the molecular mechanisms and identifying key genes associated with salt tolerance is crucial for developing rice varieties that can thrive in saline environments, particularly in regions affected by soil salinization. In this study, we conducted an RNA-sequencing-based time-course transcriptome analysis of 'Jao Khao', a salt-tolerant Thai rice variety, grown under normal or saline (160 mM NaCl) soil conditions. Leaf samples were collected at 0, 3, 6, 12, 24, and 48 h. In total, 36 RNA libraries were sequenced. 'Jao Khao' was found to be highly salt-tolerant, as indicated by the non-significant differences in relative water content, cell membrane stability, leaf greenness, and chlorophyll fluorescence over a 9-day period under saline conditions. Plant growth was slightly retarded during days 3-6 but recovered by day 9. Based on time-series transcriptome data, we conducted differential gene expression and weighted gene co-expression network analyses. Through centrality change from normal to salinity network, 111 key hub genes were identified among 1,950 highly variable genes. Enriched genes were involved in ATP-driven transport, light reactions and response to light, ATP synthesis and carbon fixation, disease resistance and proteinase inhibitor activity. These genes were upregulated early during salt stress and RT-qPCR showed that 'Jao Khao' exhibited an early upregulation trend of two important genes in energy metabolism: RuBisCo (LOC_Os10g21268) and ATP synthase (LOC_Os10g21264). Our findings highlight the importance of managing energy requirements in the initial phase of the plant salt-stress response. Therefore, manipulation of the energy metabolism should be the focus in plant resistance breeding and the genes identified in this work can serve as potentially effective candidates.

Opportunities and limits of image-based plant stress phenotyping: detecting plant salt stress status using machine learning techniques

Abstract Plant stress phenotyping is a useful tool to facilitate targeted interventions and optimize management practices of plants growing in stressful conditions. However, various technical challenges still need to be overcome, though, and there is a clear need for investigating functional traits that can be used as a proxy for stress prediction, especially for abiotic stresses. This experimental work leveraged machine learning classification models to detect salt stress in two populations of a non-model species, combining image-based approaches (i.e. both manual and automated) and minimal morpho-physiological/biochemical analyses. A small set of specific features, combining malondialdehyde content with other non-destructive image-derived traits, such as Chroma Difference and Chroma Ratio indices, was able to distinguish non-stressed from stressed plants (2-class model; precision: 0.91) as well as stress intensity (3-class model; precision: 0.84). This flexible approach can be adapted to different plant developmental stages and leaf shape/morphology. In the future, the robustness and reliability of the models should be tested in other species and other abiotic stresses, such as drought.

Methyl jasmonate mitigates biochemical and phytochemical changes in salt stressed Stevia rebaudiana plants

This study explored the effects of salt stress on growth, oxidative stress, and steviol glycoside content in Stevia rebaudiana Bertoni plants cultivated in soil supplemented with methyl jasmonate (MeJA). Stevia plants were cultivated under normal and salt stress conditions, with and without MeJA supplements of 30 ?M, 60 ?M, and 120 ?M. Samples were harvested after the 1st, 3rd, 5th, 10th, and 15th day of treatment. The levels of chlorophyll (p<0.0001), carotenoids (p<0.0001), and antioxidant enzymes such as catalase (p<0.0001), superoxide dismutase (p<0.0001), APX (p<0.0001), and glutathione reductase (p<0.0001) were observed. The quantification of steviol glycosides, including stevioside (p<0.0001) and rebaudioside-A (p<0.0001), was studied by the most advanced hyphenated technique, LC-MS/MS. The study revealed that the oxidative stress responses were significantly improved in MeJA-treated plants compared to salt-stress control plants. The level of production of phenols (p<0.0001), flavonoids, total sugar, reducing sugar, and steviol glucosides was significantly altered in salt-stress plants. MeJA showed a dose- and time-dependent significant effect on the improvement of these factors over salt stress. In conclusion, MeJA not only improves the growth of plants but also reduces oxidative stress and enhances the level of phytochemicals under saline stress.

The role of biochar nanoparticles in reducing salt stress in tomato (Solanum lycopersicum) plants grown in fields

Soil salinization is a major threat to global food security, affecting over 20 % of cultivated land and reducing yields of important crops like tomato (Solanum lycopersicum). This field study explored the potential of biochar nanoparticles (BNPs) derived from rice straw to mitigate salt stress in tomato plants. The BNPs, prepared by pyrolysis at 350 ℃ and ball milling, had an average size of 130.32 nm. Tomato plants were grown for 12 weeks in soil with 0.2 % NaCl (w/w) and BNPs at 0.5, 1, or 2 ‰ w/w. Controls included unamended soil, soil with NaCl only, soil with BNPs only, and regular biochar with and without NaCl. BNPs significantly improved growth, biomass, and fruit yield of salt-stressed tomato plants. The 2 ‰ BNP treatment increased fruit yield by 115.05 % compared to salt stress alone. Stem fresh and dry weights increased by 35.64 % and 79.71 %, respectively, while root fresh and dry weights increased by 138.27 % and 68.35 %, respectively. BNPs enhanced fruit quality, with higher concentrations showing better effects. BNPs alleviated salt stress by regulating ion homeostasis, limiting Na translocation to leaves and fruits (reducing Na content by 35.15 % in leaves and 16.06 % in fruits), improving K content and Na/K ratio, and influencing Mg and P absorption and translocation. The nanoscale size, high surface area, and enhanced reactivity of BNPs allow them to penetrate plant tissues and interact with ion transport components. This study demonstrates the potential of BNPs as a sustainable approach for enhancing tomato salt tolerance in the field. Using crop residues for BNP production supports circular economy and sustainable agriculture. This approach holds potential for enhancing sustainable crop production under saline conditions, contributing to food security and the development of resilient agricultural systems in challenging environments.

The transcription factor ZmNAC84 increases maize salt tolerance by regulating ZmCAT1 expression

Salt stress severely affects plant growth and yield. The transcription factor NAC plays a variety of important roles in plant abiotic stress, but we know relatively little about the specific molecular mechanisms of NAC in antioxidant defense. Here, our genetic studies reveal the positive regulation of salt tolerance in maize by the transcription factor ZmNAC84. Under salt stress, overexpression of ZmNAC84 in maize increased the expression of ZmCAT1, enhanced CAT activity, and consequently reduced H2O2 accumulation, thereby improving salt stress tolerance in maize. Whereas RNA interference-mediated knockdown of ZmNAC84 produced the opposite effect. Subsequently, we found that ZmNAC84 directly binds to and regulates the expression of the ZmCAT1 promoter, and the hybridized material also demonstrated that ZmCAT1 is a downstream target gene of ZmNAC84. In addition, phenotypic and biochemical analyses indicated that ZmCAT1 positively regulated salt tolerance by regulating H2O2 accumulation under salt stress. Taken together, these results reveal the function of ZmNAC84 in regulating ZmCAT1-mediated antioxidant defense in response to salt stress in plants.

Research of salt tolerance of genetically modified wheat plants with an additional copy of the ornithine-Δ-aminotransferase gene

Aim. To investigate the level of resistance to salt stress of T3 and T4 seed generation plants of genetically modified wheat (Triticum aestivum L.) with an additional copy of the ornithine-δ-aminotransferase (oat) gene and their original genotypes. Methods. Determination of the content of free L-proline (Pro) and physiological and morphometric parameters. Results. The level of Pro was studied and the morphometric and growth parameters of the offspring of transgenic plants and their original forms under normal / stress conditions were analyzed. Conclusions. T3 and T4 wheat plants under salinity conditions had a higher percentage and higher rate of seed germination compared to the original genotypes. During in vitro cultivation of seedlings, a stress state was observed at doses of 250 and 300 mM NaCl, at which the percentage of survival of transgenic variants was 83.3, non-transgenic only 33.3. Under conditions of in vivo salt stress, T3 and T4 plants had taller shoots and longer roots compared to the original forms. The survival rate of genetically modified plants was ~ 90 %, non-transgenic plants about 60 %. There was no significant difference in the accumulation of free L-proline between the investigated plant variants. It increased in transgenic seedlings on the 21st day of stress under conditions of artificially simulated salinity.

Halotolerant Enterobacter asburiae A103 isolated from the halophyte Salix linearistipularis: Genomic analysis and growth-promoting effects on Medicago sativa under alkali stress

Soil salinization negatively affects plant growth and threatens food security. Halotolerant plant growth-promoting bacteria (PGPB) can alleviate salt stress in plants via diverse mechanisms. In the present study, we isolated salt-tolerant bacteria with phosphate-solubilizing abilities from the rhizosphere of Salix linearistipularis, a halophyte distributed in saline-alkali soils. Strain A103 showed high phosphate solubilization activity and was identified as Enterobacter asburiae based on genome analysis. In addition, it can produce indole-3-acetic acid (IAA), siderophores, and 1-aminocyclopropane-1-carboxylate (ACC) deaminase. Genome mining has also revealed the presence of several functional genes involved in the promotion of plant growth. Inoculation with A103 markedly improved alfalfa growth in the presence of 100 mM NaHCO3. Under alkali stress, the shoot and root dry weights after bacterial inoculation improved by 42.9 % and 21.9 %, respectively. Meanwhile, there was a 35.9–37.1 % increase in the shoot and root lengths after treatment with A103 compared to the NaHCO3-treated group. Soluble sugar content, peroxidase and catalase activities increased in A103-inoculated alfalfa under alkaline stress. A significant decrease in the malondialdehyde content was observed after treatment with strain A103. Metabolomic analysis indicated that strain A103 positively regulated alkali tolerance in alfalfa through the accumulation of metabolites, such as homocarnosine, panthenol, and sorbitol, which could reduce oxidative damage and act as osmolytes. These results suggest that halophytes are valuable resources for bioprospecting halotolerant beneficial bacteria and that the application of halotolerant growth-promoting bacteria is a natural and efficient strategy for developing sustainable agriculture.

Promoting salt tolerance, growth, and phytochemical responses in coriander (Coriandrum sativum L. cv. Balady) via eco-friendly Bacillus subtilis and cobalt

In plant production, evaluation of salt stress protectants concerning their potential to improve growth and productivity under saline stress is critical. Bacillus subtilis (Bs) and cobalt (Co) have been proposed to optimize salt stress tolerance in coriander (Coriandrum sativum L. cv. Balady) plants by influencing some physiological activities. The main aim of this work is to investigate the response of (Bs) and (Co) as eco-safe salt stress protectants to resist the effect of salinity, on growth, seed, and essential oil yield, and the most important biochemical constituents of coriander produced under salt stress condition. Therefore, in a split-plot factorial experiment design in the RCBD (randomized complete block design), four levels of salinity of NaCl irrigation water (SA) were assigned to the main plots; (0.5, 1.5, 4, and 6 dS m−1); and six salt stress protectants (SP) were randomly assigned to the subplots: distilled water; 15 ppm (Co1); 30 ppm (Co2); (Bs); (Co1 + Bs); (Co2 + Bs). The study concluded that increasing SA significantly reduced coriander growth and yield by 42.6%, which could be attributed to ion toxicity, oxidative stress, or decreased vital element content. From the results, we recommend that applying Bs with Co (30 ppm) was critical for significantly improving overall growth parameters. This was determined by the significant reduction in the activity of reactive oxygen species scavenging enzymes: superoxide dismutase (SOD), catalase (CAT), and malondialdehyde (MDA) and non-enzyme: proline by 5, 11.3, 14.7, and 13.8% respectively, while increasing ascorbic acid by 8% and preserving vital nutrient levels and enhancing plant osmotic potential to buffer salt stress, seed yield per plant, and essential oil yield increased by 12.6 and 18.8% respectively. The quality of essential oil was indicated by highly significant quantities of vital biological phytochemicals such as linalool, camphor, and protein which increased by 10.3, 3.6, and 9.39% respectively. Additional research is suggested to determine the precise mechanism of action of Bs and Co's dual impact on medicinal and aromatic plant salt stress tolerance.

Functional characterization of maize phytochrome-interacting factor 3 (ZmPIF3) in enhancing salt tolerance in arabidopsis

Soil salinization, a prevalent form of environmental stress, leads to significant soil desertification and impacts agricultural productivity by altering the internal soil environment, slowing cellular metabolism, and modifying cellular architecture. This results in a marked reduction in both the yield and diversity of crops. Maize, which is particularly susceptible to salt stress, serves as a critical model for studying these effects, making the elucidation of its molecular responses essential for crop improvement strategies. This study focuses on the phytochrome-interacting factor 3 (PIF3), previously known for its role in freezing tolerance, to assess its function in salt stress tolerance. Utilizing two transcript variants of maize ZmPIF3 (ZmPIF3.1 and ZmPIF3.2), we engineered Arabidopsis transgenic lines to overexpress these variants and analyzed their phenotypic, physiological, biochemical, and transcriptomic responses to salt stress. Our findings reveal that these transgenic lines displayed not only enhanced salt tolerance but also improved peroxide decomposition and reduced cellular membrane damage. Transcriptome analysis indicated significant roles of hormonal and Ca2+ signaling pathways, along with key transcription factors, in mediating the enhanced salt stress response. This research underscores a novel role for ZmPIF3 in plant salt stress tolerance, offering potential avenues for breeding salt-resistant crop varieties.

A novel Microbacterium strain SRS2 promotes the growth of Arabidopsis and MicroTom (S. lycopersicum) under normal and salt stress conditions.

Microbacterium strain SRS2 promotes growth and induces salt stress resistance in Arabidopsis and MicroTom in various growth substrates via the induction of the ABA pathway. Soil salinity reduces plant growth and development and thereby decreases the value and productivity of soils. Plant growth-promoting rhizobacteria (PGPR) have been shown to support plant growth such as in salt stress conditions. Here, Microbacterium strain SRS2, isolated from the root endosphere of tomato, was tested for its capability to help plants cope with salt stress. In a salt tolerance assay, SRS2 grew well up to medium levels of NaCl, but the growth was inhibited at high salt concentrations. SRS2 inoculation led to increased biomass of Arabidopsis and MicroTom tomato in various growth substrates, in the presence and in the absence of high NaCl concentrations. Whole-genome analysis revealed that the strain contains several genes involved in osmoregulation and reactive oxygen species (ROS) scavenging, which could potentially explain the observed growth promotion. Additionally, we also investigated via qRT-PCR, promoter::GUS and mutant analyses whether the abscisic acid (ABA)-dependent or -independent pathways for tolerance against salt stress were involved in the model plant, Arabidopsis. Especially in salt stress conditions, the plant growth-promotion effect of SRS2 was lost in aba1, abi4-102, abi3, and abi5-1 mutant lines. Furthermore, ABA genes related to salt stress in SRS2-inoculated plants were transiently upregulated compared to mock under salt stress conditions. Additionally, SRS2-inoculated ABI4::GUS and ABI5::GUS plants were slightly more activated compared to the uninoculated control under salt stress conditions. Together, these assays show that SRS2 promotes growth in normal and in salt stress conditions, the latter possibly via the induction of ABA-dependent and -independent pathways.

The effect of the combined application of elicitors to Salvia virgata Jacq. under salinity stress on physiological and antioxidant defense

Salinity stress is one of the most important stress barriers to crop production worldwide. Developing and implementing new strategies against salinity stress is critical for increasing agricultural productivity and supporting sustainable farming. Elicitors such as nanoparticles and Salicylic acid have recently been used potentially for better product yield. Therefore, in our research the Salvia virgata plant was exposed to salinity (NaCl) stress, and zinc oxide nanoparticles (ZnONP), salicylic acid (SA), and the ZnONP + SA combination were applied to plants divided into different groups. While salinity stress decreased the amount of chlorophyll a, chlorophyll b, and carotenoid pigments, SA, ZnONP, and SA + ZnONP elicitors combined with salinity stress enhanced the content of all three pigments. While salt stress raised MDA, H2O2, total phenolic, total flavonoid, soluble sugar and proline content, elicitor applications enhanced proline, soluble sugar, total phenolic and total flavonoid content more. Additionally, the application of NaCl + SA + ZnONP increased proline content by 21.55% and sugar content by 15.73% compared to NaCl application, while decreasing MDA content by 42.28% and H2O2 levels by 42.34%, thereby alleviating the plant's salt stress. It was revealed that DPPH, ABTS, and CUPRAC antioxidant activity sequence used to determine the total antioxidant activity displayed similarities, and it was found as NaCI + ZnONP > NaCI + SA > NaCI + SA + ZnONP > NaCI > Control. Furthermore, all elicitor applications increased CAT, GR, APX, and SOD enzyme activities while reducing oxidative stress in S. virgata plants. When all the data were evaluated, it was confirmed that SA and ZnONP had a synergistic effect and that SA and ZnONP have the potential to support plant development and growth under salinity. SA and ZnONP applications may have the capacity to least the detrimental impacts of salinity stress on plants. However, further research is needed to investigate the effectiveness of SA and ZnONPs in ameliorating salinity or different stress factors in various other plants.

Silencing of GhSINAT5 Reduces Drought Resistance and Salt Tolerance in Cotton.

The SEVEN IN ABSENTIA (SINA) E3 ubiquitin ligase is widely involved in drought and salt stress in plants. However, the biological function of the SINA proteins in cotton is still unknown. This study aimed to reveal the function of GhSINAT5 through biochemical, genetic and molecular approaches. GhSINAT5 is expressed in several tissues of cotton plants, including roots, stems, leaves and cotyledons, and its expression levels are significantly affected by polyethylene glycol, abscisic acid and sodium chloride. When GhSINAT5 was silenced in cotton plants, drought and salinity stress occurred, and the length, area and volume of the roots significantly decreased. Under drought stress, the levels of proline, superoxide dismutase, peroxidase and catalase in the GhSINAT5-silenced cotton plants were significantly lower than those in the non-silenced control plants, whereas the levels of hydrogen peroxide and malondialdehyde were greater. Moreover, the expression of stress-related genes in silenced plants under drought stress suggested that GhSINAT5 may play a positive role in the plant response to drought and salt stress by regulating these stress response-related genes. These findings not only deepen our understanding of the mechanisms of drought resistance in cotton but also provide potential targets for future improvements in crop stress resistance through genetic engineering.

Comparative Physiological and Transcriptomic Analyses of Oat (Avena sativa) Seedlings under Salt Stress Reveal Salt Tolerance Mechanisms.

Soil salinity is a major abiotic stress limiting crop production globally. Oat (Avena sativa) is an annual cereal with a strong salt tolerance, a high yield, and nutritional quality, although the mechanisms underlying its salt stress response remain largely unknown. We examined the physiological and transcriptomic responses of A. sativa seedlings to salt stress in tolerant cultivar Qingyongjiu 195 and sensitive cultivar 709. Under salt stress, Qingyongjiu 195 maintained a higher photosynthetic efficiency, antioxidant enzymes activity, and leaf K+ accumulation but a lower Na+ uptake than 709. RNA-seq revealed 6616 differentially expressed genes (DEGs), including 4265 up- and 2351 downregulated. These were enriched in pathways like plant-pathogen interaction, phenylpropanoid biosynthesis, and MAPK signaling. We specifically highlight DEGs involved in photosynthesis (chlG, CP47 psbB, COX2, LHCB) and antioxidants (trxA, GroES). Qingyongjiu 195 also appeared to enhance K+ uptake via KAT1 and AKT2 and sequester Na+ in vacuoles via NHX2. Additionally, HKT restricted Na+ while promoting K+ transport to shoots, maintaining K+/Na+. The expression levels of CAX, ACA, CML, CaM, and CDPK in Qingyongjiu 195 were higher than those in 709. Oats regulated Ca2+ concentration through CAX and ACA after salt stress, decoded Ca2+ signals through CML, and then transferred Ca2+ signals to downstream receptors through the Ca2+ sensors CaM and CDPK, thereby activating K+/Na+ transporters, such as SOS1 and NHX, etc. Our results shed light on plant salt stress response mechanisms and provide transcriptomic resources for molecular breeding in improving salt tolerance in oats.

Role of Quaternary Aminoacid Derivatives and Ion Homeostasis in Amelioration of Salinity Stress

Salinity is a detriment to plant production throughout the world. Salinity impacts the quality of irrigation water. Understanding salt stress in plants necessitates complex physiological and metabolic stages. Preserving turgescent cells and regulating the water potential to maintain a proper water balance among the key responsibilities of osmoprotectants, long-term, high salt doses can slow down plant growth and development by interfering with physiological processes like nutrient imbalance, membrane damage, enzyme inhibition and metabolic dysfunctions like photosynthesis, hormone production and ion homeostasis, all of which can result in plant death. Hyperionic and hyperosmotic stress are also caused by prolonged, high salt doses. Osmolytes (such as proline and glycine betaine) accumulate under different salt levels, antioxidant enzyme activities increase and eventually some of the negative effects of NaCl toxicity on plants are mitigated. Plants under salt stress may have higher concentrations of reactive oxygen species (ROS) such as superoxide radicals (O2) and hydrogen peroxide (H2O2). Ion homeostasis is crucial for plants during abiotic stress conditions.

Effect of seed priming with auxin on ROS detoxification and carbohydrate metabolism and their relationship with germination and early seedling establishment in salt stressed maize

As crucial stages in the plant ontogeny, germination and seedling establishment under adverse conditions greatly determine staple crop growth and productivity. In the context of green technologies aiming to improve crop yield, seed priming is emerging as an effective approach to enhance seed vigor and germination performance under salt stress. In this study, we assess the efficiency of seed priming with indole-3-acetic acid (IAA) in mitigating the adverse effects of salt stress on maize (Zea mays L.) seedlings during germination and early seedling stages. In unprimed seeds, salt stress reduced germination indices, and seedling (both radicle and coleoptile) growth, together with decreased tissue hydration. However, seed priming using IAA significantly improved maize salt response, as reflected by the increased seed germination dynamics, early seedling establishment, and water status. Besides, seedlings from IAA-primed seeds showed a higher activity of α-amylase, resulting in increased sugar contents in roots and coleoptiles of salt-stressed plants. Further, IAA-seed priming stimulated the accumulation of endogenous IAA in salt-stressed seedlings, in concomitance with a significant effect on reactive oxygen species detoxification and lipid peroxidation prevention. Indeed, our data revealed increased antioxidant enzyme activities, differentially regulated in roots and coleoptiles, leading to increased activities of the antioxidant enzymes (SOD, CAT and GPX). In summary, data gained from this study further highlight the potential of IAA in modulating early interactions between multiple signaling pathways in the seed, endowing maize seedlings with enhanced potential and sustained tolerance to subsequent salt stress.