Salinity-induced Oxidative Stress Research Articles

Versatile MXenzymes Scavenging ROS for Promotion of Seed Germination under Salt Stress.

Salinization is recognized as a global problem, restricting agricultural production and sustainability. Targeting the salinity-induced oxidative stress, antioxidant treatment represents a protective strategy to improve plant salt tolerance. Herein, we report a V4C3 MXene nanozyme (MXenzyme), which exhibits good biocompatibility and excellent reactive oxygen species scavenging activity to ameliorate the salt stress-induced inhibition of seed germination. V4C3 MXenzyme treatment can significantly relieve salinity-induced oxidative stress and restore the antioxidant system in pea seeds, thus improving the phenotypic traits during germination. The molecular mechanism by which antioxidant V4C3 MXenzymes augment salt tolerances is revealed through transcriptomics and metabolomics. V4C3 MXenzymes significantly regulate the gene expression of antioxidant enzymes and molecule biosynthesis that correlate closely with hormone signal transduction genes and energy metabolism genes. With correlation and the combined analysis, redox homeostasis targeted by antioxidant V4C3 MXenzymes plays a critical role in promoting plant growth under salt stress.

Ascorbic acid-mediated enhancement of antioxidants and photosynthetic efficiency: A strategy for enhancing canola yield under salt stress

Ascorbic acid (AsA), a water-soluble antioxidant, act as cofactor for enzymes that regulate photosynthesis, hormonal and antioxidant biosynthesis that enables the plants to alleviate the harmful effects of salinity stress. The study was aimed to investigate the ameliorative role of foliar application of 200 ppm ascorbic acid (AsA) in improving growth by changing antioxidant response, photosynthetic capacity and mineral nutrient status of two canola varieties (Dunkled and Cyclone) under salinity stress (200 mM NaCl). Salt stress reduced plant biomass, photosynthetic activity, and accumulation of macro and micronutrients such as K+, Ca2+and Zn2+ in both canola varieties, on the other hand accumulation of Na+ and Cl−was increased. The salinity-induced oxidative stress (H2O2 and MDA) caused photoinhibition of PSII at the donor and acceptor ends. The salinity-induced reduction in efficiency of electron donation to PSII (Fv/Fo) and electron transport through PSII (Fm/Fo), especially in Cyclone, significantly reduced ETRII thus enhancing CEF around PSI and NPQ in both canola varieties that has been considered as photo-protective mechanism of plants. In addition, salt stress enhanced CEF around PSI. However, application of AsA improved the structural stability of PSII, linear electron transport and reduced donor end limitation of PSI activity by improving electron transfer from PSII to PSI. The application of AsA improved the stomatal conductance, inter-cellular CO2 concentration and net CO2 assimilation rate thereby resulting in improved consumption of extra-electrons in CO2 fixation generated by photosynthetic electron transport. Exogenous AsA application reduced the oxidative stress and improved the antioxidant potential by managing extra-electrons produced in CO2 fixation. All these physiological and biochemical changes due to AsA application helped the canola plants to improve growth and yield under salinity. Thus, the application of ascorbic acid has the potential to ameliorate the detrimental effects of NaCl stress on canola plants.

A REVIEW ON IMPROVEMENT OF SALT TOLERANCE IN RICE (ORYZA SATIVA L) BY INCREASING ANTIOXIDANT DEFENCE SYSTEMS USING EXOGENOUS APPLICATION OF PROLINE

Rice (Oryza sativa L) stands as a staple food crop globally particularly in the regions with warm climates. However, its cultivation faces significant challenges from abiotic stresses like salinity, which hinder crop growth and productivity. Salinity stress disrupts essential physiological processes, leading to reduced yields and compromised food security. In response to this pressing concern, this review investigates the potential of exogenous proline application to enhance salt tolerance in rice. The study delves into the intricate mechanisms underlying salinity stress in rice plants, highlighting its detrimental effects on growth, ion balance, and cellular metabolism. Salinity-induced oxidative stress, characterized by the accumulation of reactive oxygen species (ROS), exacerbates cellular damage, impairing plant growth and development. Proline, an amino acid known for its multifaceted roles in stress mitigation, emerges as a promising candidate for enhancing salt tolerance in rice. Exogenous application of proline demonstrates significant improvements in rice growth, yield and physiological attributes under saline conditions. The study elucidates the impact of exogenous proline on various aspects of rice physiology, including seed germination, water relations, and oxidative stress mitigation. By enhancing nutrient uptake, maintaining ion homeostasis, and fortifying antioxidant defences, proline offers a promising avenue for sustainable rice production in the face of escalating salinity stress. In conclusion, this study underscores the pivotal role of exogenous proline in augmenting salt tolerance in rice, offering insights into novel strategies for mitigating the adverse effects of salinity stress on crop yields.

Characterization of a Novel Polysaccharide Derived from Rhizospheric Paecilomyces vaniformisi and Its Mechanism for Enhancing Salinity Resistance in Rice Seedlings.

Soil salinity is an important limiting factor in agricultural production. Rhizospheric fungi can potentially enhance crop salinity tolerance, but the precise role of signaling substances is still to be systematically elucidated. A rhizospheric fungus identified as Paecilomyces vaniformisi was found to enhance the salinity tolerance of rice seedlings. In this study, a novel polysaccharide (PPL2b) was isolated from P. vaniformisi and identified as consisting of Manp, Glcp, GalpA, and Galp. In a further study, PPL2b showed significant activity in alleviating salinity stress-induced growth inhibition in rice seedlings. The results indicated that under salinity stress, PPL2b enhances seed germination, plant growth (height and biomass), and biochemical parameters (soluble sugar and protein contents). Additionally, PPL2b regulates genes such as SOS1 and SKOR to decrease K+ efflux and increase Na+ efflux. PPL2b increased the expression and activity of genes related to antioxidant enzymes and nonenzyme substances in salinity-induced oxidative stress. Further study indicated that PPL2b plays a crucial role in regulating osmotic substances, such as proline and betaine, in maintaining the osmotic balance. It also modulates plant hormones to promote rice seedling growth and enhance their tolerance to soil salinity. The variables interacted and were divided into two groups (PC1 77.39% and PC2 18.77%) based on their relative values. Therefore, these findings indicate that PPL2b from P. vaniformisi can alleviate the inhibitory effects of salinity stress on root development, osmotic adjustment, ion balance, oxidative stress balance, and growth of rice seedlings. Furthermore, it suggests that polysaccharides produced by rhizospheric fungi could be utilized to enhance crop tolerance to salinity.

How Does Zinc Improve Salinity Tolerance? Mechanisms and Future Prospects.

Salinity stress (SS) is a serious abiotic stress and a major constraint to agricultural productivity across the globe. High SS negatively affects plant growth and yield by altering soil physio-chemical properties and plant physiological, biochemical, and molecular processes. The application of micronutrients is considered an important practice to mitigate the adverse effects of SS. Zinc (Zn) is an important nutrient that plays an imperative role in plant growth, and it could also help alleviate the effects of salt stress. Zn application improves seed germination, seedling growth, water uptake, plant water relations, nutrient uptake, and nutrient homeostasis, therefore improving plant performance and saline conditions. Zn application also protects the photosynthetic apparatus from salinity-induced oxidative stress and improves stomata movement, chlorophyll synthesis, carbon fixation, and osmolytes and hormone accumulation. Moreover, Zn application also increases the synthesis of secondary metabolites and the expression of stress responsive genes and stimulates antioxidant activities to counter the toxic effects of salt stress. Therefore, to better understand the role of Zn in plants under SS, we have discussed the various mechanisms by which Zn induces salinity tolerance in plants. We have also identified diverse research gaps that must be filled in future research programs. The present review article will fill the knowledge gaps on the role of Zn in mitigating salinity stress. This review will also help readers to learn more about the role of Zn and will provide new suggestions on how this knowledge can be used to develop salt tolerance in plants by using Zn.

Phenotypic and microarray analysis reveals salinity stress-induced oxidative tolerance in transgenic rice expressing a DEAD-box RNA helicase, OsDB10.

Helicases are the motor proteins not only involved in the process of mRNA metabolism but also played a significant role in providing abiotic stresses tolerance. In this study, a DEAD-box RNA helicase OsDB10 was cloned and functionally characterized. The transcript levels of OsDB10 were increased both in shoot and root upon salt, heat, cold, and ABA application and was more prominent in shoot compared to root. Genomic integration of OsDB10 in transgenic rice was confirmed by PCR, Southern blot and qRT-PCR analysis. The transgenic plants showed quicker seed germination, reduced necrosis, higher chlorophyll, more survival rate, better seedling growth, and produced more grain yield under salinity stress. Furthermore, transgenic lines also accumulated less Na+ and high K+ ions and salinity tolerance of the transgenic were also assayed by measuring different bio-physiological indices. Moreover, the OsDB10 transgenic plants showed enhanced tolerance to salinity-induced oxidative stress by scavenging ROS and increased activity of antioxidants enzymes. Microarray analysis showed upregulation of transcriptional regulations and metabolic reprogramming as OsDB10 overexpression modulates the expression of many other genes. Altogether, our results confirmed that OsDB10 is a functional DEAD-box RNA helicase and played vital roles in plant defence response against salinity stress.

Genetic linkage mapping and QTL identification for salinity tolerance in Indian mustard (Brassica juncea L. Czern and Coss.) using SSR markers

Soil salinity is one of the major environmental constraints that limits crop yield and nearly 7% of the total area worldwide is affected by salinity. Salinity-induced oxidative stress causes membrane damage during germination and seedling growth. Indian mustard is a major oilseed crop in India and its production and productivity are severely affected by salt stress. Breeding Brassica cultivars for salinity tolerance by conventional means is very difficult and time-consuming. Therefore, understanding the molecular components associated with salt tolerance is needed to facilitate breeding for salt tolerance in Brassica. In this investigation, quantitative trait loci (QTLs) associated with salt tolerance were identified using F2:3 mapping population developed from a cross between CS52 (salinity tolerant) and RH30 (salinity sensitive). Parents and F2:3 were evaluated under controlled and salinity stress conditions for 14 morpho-physiological traits for two consecutive generations (F2 and F2:3), explaining proportion of the phenotypic variance under control condition. Simple sequence repeat (SSR) markers were used for mapping studies. A genetic linkage map based on 42 simple sequence repeats (SSRs) markers was constructed covering 2298.5 ​cM (Haldane) to identify the loci associated with salt tolerance in Brassica juncea. Forty-one SSRs showing polymorphism in the parents (CS52 and RH30) were mapped on 8 linkage groups (C1–C8). One marker (nga 129) did not map to any of the linkage group and was excluded from mapping. Linkage group 5 (C5; 317.9 ​cM) was longest and linkage group 1 (C1, 255.0 ​cM) was shortest. Further, we identified 15 QTLs controlling 8 traits using F2:3 population. These QTLs explained 12.44–60.63% of the phenotypic variation with a LOD score range of 3.62–5.97. Out of these QTLs, QMI4.1 related to membrane injury showed 51.28% phenotypic variance with a LOD score of 3.34. QTL QBYP8.1 related to biological yield per plant showed 60.63% phenotypic variance at a LOD score of 3.62. The highest LOD score of 5.97 was recorded for QTL related to seed yield per plant (QSYP4.1). Major QTLs were QTL for biological yield per plant (QBYP8.1), QTL for siliquae per plant (QSP4.1), QTL for primary branches (QPB4.1), QTLs for seed per siliqua (QSS4.1, QSS4.2), QTL for seed yield per plant (QSYP4.1), and QTL for membrane injury (QMI8.1) which showed more than 50% phenotypic variance. These QTLs identified in our study need to be confirmed in other populations as well so that these can be used in marker-assisted selection and breeding to enhance salt tolerance in Brassica juncea.

Chitosan oligomers (COS) trigger a coordinated biochemical response of lemongrass (Cymbopogon flexuosus) plants to palliate salinity-induced oxidative stress

Plant susceptibility to salt depends on several factors from its genetic makeup to modifiable physiological and biochemical status. We used lemongrass (Cymbopogon flexuosus) plants as a relevant medicinal and aromatic cash crop to assess the potential benefits of chitosan oligomers (COS) on plant growth and essential oil productivity during salinity stress (160 and 240 mM NaCl). Five foliar sprays of 120 mg L−1 of COS were applied weekly. Several aspects of photosynthesis, gas exchange, cellular defence, and essential oil productivity of lemongrass were traced. The obtained data indicated that 120 mg L−1 COS alleviated photosynthetic constraints and raised the enzymatic antioxidant defence including superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD) activities that minimised salt-induced oxidative damage. Further, stomatal conductance (gs) and photosynthetic CO2 assimilation (A) were improved to support overall plant development. The same treatment increased geraniol dehydrogenase (GeDH) activity and lemongrass essential oil production. COS-induced salt resilience suggests that COS could become a useful biotechnological tool in reclaiming saline soil for improved crop productivity, especially when such soil is unfit for leading food crops. Considering its additional economic value in the essential oil industry, we propose COS-treated lemongrass as an excellent alternative crop for saline lands.

Exogenous Application of Calcium Ameliorates Salinity Stress Tolerance of Tomato (Solanum lycopersicum L.) and Enhances Fruit Quality.

Tomato is affected by various biotic and abiotic stresses, especially salinity, which drastically hinders the growth and yield of tomato. Calcium (Ca) is a vital macronutrient which plays physiological and biochemical roles in plants. Hence, we studied the protective roles of Ca against salinity stress in tomato. There were eight treatments comprising control (nutrient solution), 5 mM Ca, 10 mM Ca, 15 mM Ca, 12 dS m-1 NaCl, 12 dS m-1 NaCl + 5 mM Ca, 12 dS m-1 NaCl + 10 mM Ca and 12 dS m-1 NaCl + 15 mM Ca, and two tomato varieties: BARI tomato-2 and Binatomato-5. Salinity significantly decreased the plant-growth and yield attributes, relative water content (RWC), photosynthetic pigments (SPAD value) and the uptake of K, Ca and Mg in leaves and roots. Salinity-induced oxidative stress was present in the form of increased Na+ ion concentration, hydrogen peroxide (H2O2) content and lipid peroxidation (MDA). Ca application reduced oxidative stress through the boosting of antioxidant enzymatic activity. Exogenous Ca application enhanced proline and glycine betaine content and reduced Na+ uptake, which resulted in the inhibition of ionic toxicity and osmotic stress, respectively. Hence, Ca application significantly increased the growth and yield attributes, RWC, SPAD value, and uptake of K, Ca and Mg. Calcium application also had a significant effect on the fruit quality of tomato and the highest total soluble solid, total sugar, reducing sugar, β-carotene, vitamin C and juice pH were found for the combined application of NaCl and Ca. Therefore, application of Ca reversed the salt-induced changes through increasing osmoprotectants, activation of antioxidants enzymes, and by optimizing mineral nutrient status.

Selenium fortification stimulates antioxidant- and enzyme gene expression-related defense mechanisms in response to saline stress in Cucurbita pepo

Salinity dramatically decreases the yield of most agricultural plants by causing osmotic and ionic stress that negatively impacts plant growth and development. As previously documented, selenium (Se), as a serviceable trace element, alleviates abiotic stress impacts, particularly salinity, on several plant species. This work was done perfectly to evaluate the impact of leaf feeding with Se on indicators of salt tolerance in Cucurbita pepo. Salt stress (9.45 dS m−1) noticeably raised electrolyte leakage (EL) and malondialdehyde (MDA) owing to the rise in the examined markers of oxidative stress like hydrogen peroxide (H2O2) and superoxide (O2•‒), and Na+ content. As a result, the contents of osmo-regulators and non-enzymatic antioxidants, activities of enzymatic antioxidants, and enzyme gene expressions were markedly increased. The salinity-induced oxidative stress noticeably diminished growth features, membrane stability index (MSI), relative water content (RWC), K+/Na+ ratio, pigment, nutrient, and Se contents. Fruit yield and fruit content of Se and vitamin C also diminished. However, the application of Se noticeably decreased LI and MDA owing to the minimization in the levels of O2•‒, H2O2, and Na+. This positive outcome was connected with a further rise in the levels and activities of osmo-regulators, the defensive system components, and enzymatic gene expressions, which were positively reflected in the growth features, RWC, MSI, K+/Na+ ratio, pigment, nutrient, and Se contents, as well as fruit yield and fruit quality. Our results indicate that 15 g Se applied per hectare attenuated the negative impacts of salt stress in C. pepo via various mechanisms such as minimization of reactive oxygen species (ROS; O2•‒ and H2O2) and Na+ contents, and improvement of leaf integrity, nutrient homeostasis, photosynthetic capacity, osmoregulators and antioxidant enzyme activities, enzymatic gene expressions, and the regulation of Na+ homeostasis.

Synergistic Practicing of Rhizobacteria and Silicon Improve Salt Tolerance: Implications from Boosted Oxidative Metabolism, Nutrient Uptake, Growth and Grain Yield in Mung Bean.

Plant growth promoting rhizobacteria (PGPR) and silicon (Si) are known for alleviating abiotic stresses in crop plants. In this study, Bacillus drentensis and Enterobacter cloacae strains of PGPR and foliar application of Si were tested for regulating the antioxidant metabolism and nutrient uptake on grain yield of mung bean under irrigation of saline water (3.12 and 7.81 dS m−1). Bacterial inoculation and supplemental Si (1 and 2 kg ha−1) reduced salinity-induced oxidative stress in mung bean leaves. The improved salt stress tolerance was achieved by enhancing the activities of catalase (45%), peroxidase (43%) and ascorbate peroxidase (48%), while decreasing malondialdehyde levels (57%). Enhanced nutrient uptake of magnesium 1.85 mg g−1, iron 7 mg kg−1, zinc 49.66 mg kg−1 and copper 12.92 mg kg−1 in mung bean seeds was observed with foliar application of Si and PGPR inoculation. Biomass (7.75 t ha−1), number of pods per plant (16.02) and 1000 seed weight (60.95 g) of plants treated with 2 kg Si ha−1 and B. drentensis clearly outperformed treatments with Si or PGPR alone. In conclusion, application of Si and PGPR enhances mung bean productivity under saline conditions, thereby helping exploitation of agriculture in low productive areas.

Comparative efficacy of bio-selenium nanoparticles and sodium selenite on morpho-physiochemical attributes under normal and salt stress conditions, besides selenium detoxification pathways in Brassica napus L.

Selenium nanoparticles (SeNPs) have attracted considerable attention globally due to their significant potential for alleviating abiotic stresses in plants. Accordingly, further research has been conducted to develop nanoparticles using chemical ways. However, our knowledge about the potential benefit or phytotoxicity of bioSeNPs in rapeseed is still unclear. Herein, we investigated the effect of bioSeNPs on growth and physiochemical attributes, and selenium detoxification pathways compared to sodium selenite (Se (IV)) during the early seedling stage under normal and salt stress conditions. Our findings showed that the range between optimal and toxic levels of bioSeNPs was wider than Se (IV), which increased the plant’s ability to reduce salinity-induced oxidative stress. BioSeNPs improved the phenotypic characteristics of rapeseed seedlings without the sign of toxicity, markedly elevated germination, growth, photosynthetic efficiency and osmolyte accumulation versus Se (IV) under normal and salt stress conditions. In addition to modulation of Na+ and K+ uptake, bioSeNPs minimized the ROS level and MDA content by activating the antioxidant enzymes engaged in ROS detoxification by regulating these enzyme-related genes expression patterns. Importantly, the main effect of bioSeNPs and Se (IV) on plant growth appeared to be correlated with the change in the expression levels of Se-related genes. Our qRT-PCR results revealed that the genes involved in Se detoxification in root tissue were upregulated upon Se (IV) treated seedlings compared to NPs, indicating that bioSeNPs have a slightly toxic effect under higher concentrations. Furthermore, bioSeNPs might improve lateral root production by increasing the expression level of LBD16. Taken together, transamination and selenation were more functional methods of Se detoxification and proposed different degradation pathways that synthesized malformed or deformed selenoproteins, which provided essential mechanisms to increase Se tolerance at higher concentrations in rapeseed seedlings. Current findings could add more knowledge regarding the mechanisms underlying bioSeNPs induced plant growth.Graphical

Changes in Growth, Photosynthetic Pigments, Cell Viability, Lipid Peroxidation and Antioxidant Defense System in Two Varieties of Chickpea (Cicer arietinum L.) Subjected to Salinity Stress

Salinity is one of the most severe abiotic stresses for crop production. The present study investigates the salinity-induced modulation in growth indicators, morphology and movement of stomata, photosynthetic pigments, activity of carbonic anhydrase as well as nitrate reductase, and antioxidant systems in two varieties of chickpea (Pusa-BG5023, and Pusa-BGD72). On 20th day of sowing, plants were treated with varying levels of NaCl (0, 50, 100, 150 and 200 mM) followed by sampling on 45 days of sowing. Recorded observations on both the varieties reveal that salt stress leads to a significant decline in growth, dry biomass, leaf area, photosynthetic pigments, protein content, stomatal behavior, cell viability, activity of nitrate reductase and carbonic anhydrase with the rise in the concentration of salt. However, quantitatively these changes were less in Pusa-BG5023 as compared to Pusa-BGD72. Furthermore, salinity-induced oxidative stress enhanced malondialdehyde content, superoxide radicals, foliar proline content, and the enzymatic activities of superoxide dismutase, catalase, and peroxidase. The variety Pusa-BGD72 was found more sensitive than Pusa-BG5023 to salt stress. Out of different graded concentrations (50, 100, 150 and 200 mM) of sodium chloride, 50 mM was least toxic, and 200 mM was most damaging. The differential behavior of these two varieties measured in terms of stomatal behavior, cell viability, photosynthetic pigments, and antioxidant defense system can be used as prospective indicators for selection of chickpea plants for salt tolerance and sensitivity.

Insights into the Bacterial and Nitric Oxide-Induced Salt Tolerance in Sugarcane and Their Growth-Promoting Abilities.

Soil salinity causes severe environmental stress that affects agriculture production and food security throughout the world. Salt-tolerant plant-growth-promoting rhizobacteria (PGPR) and nitric oxide (NO), a distinctive signaling molecule, can synergistically assist in the alleviation of abiotic stresses and plant growth promotion, but the mechanism by which this happens is still not well known. In the present study, in a potential salt-tolerant rhizobacteria strain, ASN-1, growth up to 15% NaCl concentration was achieved with sugarcane rhizosphere soil. Based on 16S-rRNA gene sequencing analysis, the strain ASN-1 was identified as a Bacillus xiamenensis. Strain ASN-1 exhibits multiple plant-growth-promoting attributes, such as the production of indole-3-acetic acid, 1-aminocyclopropane-1-carboxylate deaminase, siderophores, HCN, ammonia, and exopolysaccharides as well as solubilized phosphate solubilization. Biofilm formation showed that NO enhanced the biofilm and root colonization capacity of the PGPR strain ASN-1 with host plants, evidenced by scanning electron microscopy. The greenhouse study showed that, among the different treatments, the combined application of PGPR and sodium nitroprusside (SNP) as an NO donor significantly (p ≤ 0.05) enhanced sugarcane plant growth by maintaining the relative water content, electrolyte leakage, gas exchange parameters, osmolytes, and Na+/K+ ratio. Furthermore, PGPR and SNP fertilization reduced the salinity-induced oxidative stress in plants by modulating the antioxidant enzyme activities and stress-related gene expression. Thus, it is believed that the acquisition of advanced information about the synergistic effect of salt-tolerant PGPR and NO fertilization will reduce the use of harmful chemicals and aid in eco-friendly sustainable agricultural production under salt stress conditions.

The Drought-Mediated Soybean GmNAC085 Functions as a Positive Regulator of Plant Response to Salinity.

Abiotic stress factors, such as drought and salinity, are known to negatively affect plant growth and development. To cope with these adverse conditions, plants have utilized certain defense mechanisms involved in various aspects, including morphological, biochemical and molecular alterations. Particularly, a great deal of evidence for the biological importance of the plant-specific NAM, ATAF1/2, CUC2 (NAC) transcription factors (TFs) in plant adaptation to abiotic stress conditions has been reported. A previous in planta study conducted by our research group demonstrated that soybean (Glycine max) GmNAC085 mediated drought resistance in transgenic Arabidopsis plants. In this study, further characterization of GmNAC085 function in association with salt stress was performed. The findings revealed that under this condition, transgenic soybean plants overexpressing GmNAC085 displayed better germination rates than wild-type plants. In addition, biochemical and transcriptional analyses showed that the transgenic plants acquired a better defense system against salinity-induced oxidative stress, with higher activities of antioxidant enzymes responsible for scavenging hydrogen peroxide or superoxide radicals. Higher transcript levels of several key stress-responsive genes involved in the proline biosynthetic pathway, sodium ion transporter and accumulation of dehydrins were also observed, indicating better osmoprotection and more efficient ion regulation capacity in the transgenic lines. Taken together, these findings and our previous report indicate that GmNAC085 may play a role as a positive regulator in plant adaptation to drought and salinity conditions.

Changes in Carbon Partitioning and Pattern of Antioxidant Enzyme Activity Induced by Arginine Treatment in the Green Microalga Dunaliella salina Under Long-Term Salinity.

In this work, the effects of arginine (Arg) on biochemical responses and antioxidant enzyme activity in the green microalga Dunaliella salina grown at different salt concentrations were investigated. Suspensions adapted with the concentrations of 1, 2, and 3M NaCl were treated at the exponential growth phase with a concentration of 5mM Arg. Salt stress was associated with a large decrease in the number of cells and non-reducing sugar levels but accumulated higher amounts of chlorophyll, β-carotene, reducing sugar, starch, total protein, free amino acid, and glycerol. Increased levels of protein carbonylation, lipid peroxidation, proteolysis, hydrogen peroxide, and antioxidant enzyme activity also occurred during salinity. Arg treatment changed the pattern of biochemical responses in the cells grown at high salinity by directing carbon flow to the biosynthesis of non-reducing sugars instead of starch, lowering levels of hydrogen peroxide, and downregulating antioxidant enzyme activity, but the levels of lipid peroxidation, glycerol, and β-carotene remained nearly unchanged. These results suggest that Arg treatment alleviates salinity-induced oxidative stress in D. salina cells by modifying carbon partitioning and inducing signaling molecules rather than antioxidant enzymes.

Seed Treatment with Biostimulants Extracted from Weeping Willow (Salix babylonica) Enhances Early Maize Growth.

Biostimulants can be used as innovative and promising agents to address current needs of sustainable agriculture. Weeping willow tree (Salix babylonica) extracts are rich in many bioactive compounds, including, but not limited, to salicylates and phenolics. In this study, the potential of willow bark (WB) and willow leaf (WL) extracts is evaluated as plant-based biostimulants to improve the early growth of maize (Zea mays) under control and salinity stress conditions. In 3 days, seed treatment with salicylic acid and willow extract increased the shoot FW of maize seedlings 130% and 225%, respectively. The root area was, on average, enhanced by 43% with SA and 87% with willow extract applications. Moreover, these extracts increased the leaf protein concentration and reduced the negative effects of salinity during early growth. Reductions in lipid peroxidation and specific activities of antioxidative enzymes by seed treatments with willow extracts suggests a mitigation of salinity-induced oxidative stress. For most reported traits, WL applications were at least as effective as WB applications. Results indicate that aqueous extracts of weeping willow leaves, as well as bark, can be used as seed treatment agents with biostimulant activity to improve seedling growth and establishment under control and stress conditions.

Exogenous melatonin ameliorates salinity-induced oxidative stress and improves photosynthetic capacity in sweet corn seedlings

Melatonin (MT) is involved in physiological processes in plants under abiotic stress. In this study, we investigated the effects of melatonin on maize photosynthetic and antioxidant capacities under salinity stress. Our findings indicated salinity stress significantly inhibited maize growth. However, exogenous MT promoted maize growth and antioxidant capacity. Superoxide dismutase, peroxidase, and catalase increased by 138.8, 38.7, and 32.0%, respectively, while H2O2 and malondialdehyde decreased by 23 and 31%, respectively. Exogenous MT also improved maize photosynthesis under salinity stress. Net photosynthetic rate, transpiration rate, and stomatal conductance increased by 134, 67.2, and 46.3%, respectively. Maximum quantum yield of PSII photochemistry, effective quantum yield of PSII photochemistry, photochemical quenching coefficient, and electron transport rate increased by 5.8, 70.4, 65.3, and 41.0%, respectively. Therefore, our findings suggested exogenous MT significantly ameliorated maize physiological and photosynthetic adaptation under salinity stress, thereby providing helpful guidance for maize cultivation in areas of high salinity.

Role of melatonin in regulation of lipid accumulation, autophagy and salinity-induced oxidative stress in microalga Monoraphidium sp. QLY-1

The aim of this study was to explore the effect of melatonin (MT) on lipid accumulation in Monoraphidium sp. QLY-1 under salinity stress. The interconnection between MT, oxidative stress and autophagy in the regulation of lipid synthesis was also clarified. MT application significantly promoted the lipid content, peaking at 51.74%, which was 1.16- and 1.44-fold higher than those induced by salinity stress alone (44.77%) and control group (35.96%), respectively. Exogenous MT also upregulated the transcription levels of lipogenesis-related genes and decreased salinity stress-induced oxidative stress. Interestingly, the application of MT upregulated autophagic activity, which led to the 1.47-fold upregulation of autophagy-related atg8 gene expression. Additional results demonstrated that autophagy promotion led to further increases in lipid accumulation by involving lipogenesis gene expression and ROS signalling in cells treated with MT under salinity stress conditions. The maximum lipid content (54.26%) was achieved by treatment with MT and rapamycin (RAPA), an activator of autophagy. Taken together, these findings indicate that combination of MT and salinity stress is a valuable strategy for enhancing lipid production in microalgae and provides novel insights into the regulatory mechanisms underlying the effects of MT and autophagy on the promotion of lipid synthesis and improvements to algal tolerance.

Coumarin improves tomato plant tolerance to salinity by enhancing antioxidant defence, glyoxalase system and ion homeostasis.

Salinity is a severe threat to crop growth, development and even to world food sustainability. Plant possess natural antioxidant defense tactics to mitigate salinity-induced oxidative stress. Phenolic compounds are non-enzymatic antioxidants with specific roles in protecting plant cells against stress-mediated reactive oxygen species (ROS) generation. Coumarin (COU) is one of these compounds, however, to date, little is known about antioxidative roles of exogenous COU in enhancing plant tolerance mechanisms under salt stress. The involvement of COU in increasing tomato salt tolerance was examined in the present study using COU as a pre-treatment at 20 or 30µM for 2days against salt stress (100 or 160 NaCl; 5days). The COU-mediated stimulation of plant antioxidant defence and glyoxalase systems to suppress salt-induced ROS and methylglyoxal (MG) toxicity, respectively, were the main hypotheses examined in the present study. Addition of COU suppressed salt-induced excess accumulation of ROS and MG, and significantly reduced membrane damage, lipid peroxidation and Na+ toxicity. These results demonstrate COU-improved plant growth, biomass content, photosynthetic pigment content, water retention and mineral homeostasis upon imposition of salinity. Finally, this present study suggests that COU has potential roles as a phytoprotectant in stimulating plant antioxidative mechanisms and improving glyoxalase enzyme activity under salinity stress.