Ascorbate-glutathione Cycle Research Articles

Interplay mechanism of exogenous hydrogen sulfide and nitric oxide in modulating ascorbate–glutathione cycle under nickel-induced oxidative stress in two paddy field cyanobacteria

Interplay mechanism of exogenous hydrogen sulfide and nitric oxide in modulating ascorbate–glutathione cycle under nickel-induced oxidative stress in two paddy field cyanobacteria

Magnesium Hydride Confers Osmotic Tolerance in Mung Bean Seedlings by Promoting Ascorbate–Glutathione Cycle

Despite substantial evidence suggesting that hydrogen gas (H2) can enhance osmotic tolerance in plants, the conventional supply method of hydrogen-rich water (HRW) poses challenges for large-scale agricultural applications. Recently, magnesium hydride (MgH2), a hydrogen storage material in industry, has been reported to yield beneficial effects in plants. This study aimed to investigate the effects and underlying mechanisms of MgH2 in plants under osmotic stress. Mung bean seedlings were cultured under control conditions or with 20% polyethylene glycol (PEG)-6000, with or without MgH2 addition (0.01 g L−1). Under our experimental conditions, the MgH2 solution maintained a higher H2 content and longer retention time than HRW. Importantly, PEG-stimulated endogenous H2 production was further triggered by MgH2 application. Further results revealed that MgH2 significantly alleviated the inhibition of seedling growth and reduced oxidative damage induced by osmotic stress. Pharmacological evidence suggests the MgH2-reestablished redox homeostasis was associated with activated antioxidant systems, particularly the ascorbate–glutathione cycle. The above observations were further supported by the enhanced activities and gene transcriptional levels of ascorbate peroxidase, monodehydroascorbate reductase, dehydroascorbate reductase, and glutathione reductase. Overall, this study demonstrates the importance of MgH2 in mitigating osmotic stress in mung bean seedlings, providing novel insights into the potential agricultural applications of hydrogen storage materials.

Investigation of the preharvest arginine spraying mechanism on antioxidant system in postharvest broccoli via transcriptomics and metabolomics

According to our previous study, preharvest spraying of arginine for 1 day enhanced the antioxidant capacity of postharvest broccoli, but the underlying molecular mechanisms remain unclear. We here performed a comprehensive transcriptome and metabolome analysis to investigate the effects of arginine sprayed 1 day before harvest on the antioxidant capacity and yellowing of broccoli as well as the related action mechanisms. In total, 67 differentially expressed genes and 12 key differentially accumulated metabolites were identified in broccoli at 4 and 8 days during storage. Herein, the gene expression of superoxide dismutase, catalase, and the corresponding peroxisome protein Mpv17 (MPV17) was upregulated, consequently enhancing the scavenging of reactive oxygen species. Genes encoding glucosinolate synthesis- and metabolism-related enzymes were upregulated, and among them, the gene ST5b_c was upregulated by 8.23-fold, which promoted the accumulation of its metabolites. Expression of lignin- and flavonoid biosynthesis-related genes (CAD, POD, CHI, and CHS) was elevated. Flavonoid and lignin accumulation was promoted, with a greater antioxidant capacity at 4 and 8 days, respectively, in the arginine-sprayed broccoli. Additionally, the ascorbate–glutathione cycle was promoted in broccoli at 4 days, GLCAK and APX genes were upregulated by more than 2-fold, and broccoli exhibited a higher tolerance level because of the notably stimulated ascorbic acid and glutathione accumulation. This study offers new insights into the mechanisms through which preharvest spraying of arginine regulates the antioxidant capacity of postharvest broccoli.

Tripartite interactions between grapevine, viruses, and arbuscular mycorrhizal fungi provide insights into modulation of oxidative stress responses

Arbuscular mycorrhizal fungi (AMF) can be beneficial for plants exposed to abiotic and biotic stressors. Although widely present in agroecosystems, AMF influence on crop responses to virus infection is underexplored, particularly in woody plant species such as grapevine. Here, a two-year greenhouse experiment was set up to test the hypothesis that AMF alleviate virus-induced oxidative stress in grapevine. The ‘Merlot’ cultivar was infected with three grapevine-associated viruses and subsequently colonized with two AMF inocula, containing one or three species, respectively. Five and fifteen months after AMF inoculation, lipid peroxidation - LPO as an indicator of oxidative stress and indicators of antioxidative response (proline, ascorbate - AsA, superoxide dismutase - SOD, ascorbate- APX and guaiacol peroxidases - GPOD, polyphenol oxidase - PPO, glutathione reductase - GR) were analysed. Expression of genes coding for a stilbene synthase (STS1), an enhanced disease susceptibility (EDS1) and a lipoxygenase (LOX) were determined in the second harvesting. AMF induced reduction of AsA and SOD over both years, which, combined with not AMF-triggered APX and GR, suggests decreased activation of the ascorbate-glutathione cycle. In the mature phase of the AM symbiosis establishment GPOD emerged as an important mechanism for scavenging H2O2 accumulation. These results, together with reduction in STS1 and increase in EDS1 gene expression, suggest more efficient reactive oxygen species scavenging in plants inoculated with AMF. Composition of AMF inocula was important for proline accumulation. Overall, our study improves the knowledge on ubiquitous grapevine-virus-AMF systems in the field, highlighting that established functional AM symbiosis could reduce virus-induced stress.

Ethylene and hydrogen sulfide regulate hexavalent chromium toxicity in two pulse crops: Implication on growth, photosynthetic activity, oxidative stress and ascorbate glutathione cycle

Sustainable agriculture has become prime importance to feed growing population. To achieve this goal application of exogenous hormones and signaling molecules are gaining important. In this context, we have investigated potential of ethylene (25 μM ethephon; donor) and H2S (10 μM NaHS; donor) in mitigating hexavalent chromium [Cr (VI), 50 μM] toxicity in two pulse seedlings: black bean and mung bean. Cr(VI) declined growth and gas exchange parameters (photosynthetic rate, stomatal conductance, sub cellular CO2 concentration, and transpiration level) which was accompanied by intracellular accumulation of Cr in both pulse crops and the damaging effect was greater in mung bean seedlings. The suppression in the growth and related parameters was occurred due to higher buildup of oxidative stress markers; O2•‾, H2O2, lipid peroxidation (as malondialdehyde, MDA equivalents) and membrane injury in leaf and root of both pulse crops. Cr induced disturbance in AsA-GSH cycle (reduction in the activity of glutathione reductase, ascorbate peroxidase, monodehydroascorbate reductase and dehydroascorbate reductase, and the amount of ASA and GSH) could be one of the reasons for greater accumulation of H2O2. Further, exogenous application of ethylene and H2S significantly ameliorated Cr toxicity on growth and photosynthetic activity by significantly lowering the intracellular Cr accumulation and oxidative biomarkers, and also by strengthening the activity of AsA-GSH cycle. The exogenous application of biosynthesis inhibitors of ethylene (AVG) and H2S (PAG) caused greater damaging effect on these parameters due to more accumulation of Cr(VI), thereby suggesting that the endogenous levels of these regulators are critical for Cr(VI) tolerance. Interestingly, ET did not rescue adverse effects of Cr(VI) in absence of endogenous H2S, while H2S could do so even without endogenous ethylene, suggesting that H2S played downstream signaling to ethylene in regulating Cr(VI) toxicity. Hence, being cheap and easily available theses growth regulators may be considered for sustainable agriculture.

The superoxide-mediated ascorbate-glutathione cycle modulates the transition of growth to reproduction in Ulva prolifera

The superoxide-mediated ascorbate-glutathione cycle modulates the transition of growth to reproduction in Ulva prolifera

Salicylic Acid and Melatonin Synergy Enhances Boron Toxicity Tolerance via AsA-GSH Cycle and Glyoxalase System Regulation in Fragrant Rice.

Background: Boron is an essential micronutrient for plant growth and productivity, yet excessive boron leads to toxicity, posing significant challenges for agriculture. Fragrant rice is popular among consumers, but the impact of boron toxicity on qualitative traits of fragrant rice, especially aroma, remains largely unexplored. The individual potentials of melatonin and salicylic acid in reducing boron toxicity are less known, while their synergistic effects and mechanisms in fragrant rice remain unclear. Methods: Thus, this study investigates the combined application of melatonin and salicylic acid on fragrant rice affected by boron toxicity. One-week-old seedlings were subjected to boron (0 and 800 µM) and then treated with melatonin and salicylic acid (0 and 100 µM, for 3 weeks). Results: Boron toxicity significantly impaired photosynthetic pigments, plant growth, and chloroplast integrity while increasing oxidative stress markers such as hydrogen peroxide, malondialdehyde, methylglyoxal, and betaine aldehyde dehydrogenase. Likewise, boron toxicity abridged the precursors involved in the 2-acetyl-1-pyrroline (2-AP) biosynthesis pathway. However, individual as well as combined application of melatonin and salicylic acid ameliorated boron toxicity by strengthening the antioxidant defense mechanisms-including the enzymes involved during the ascorbate-glutathione (AsA-GSH) cycle and glyoxalase system-and substantially improved 2-AP precursors including proline, P5C, Δ1-pyrroline, and GABA levels, thereby restoring the 2-AP content and aroma. These findings deduce that melatonin and salicylic acid synergistically alleviate boron toxicity-induced disruptions on the 2-AP biosynthesis pathway by improving the 2-AP precursors and enzymatic activities, as well as modulating the physio-biochemical processes and antioxidant defense system of fragrant rice plants. Conclusions: The findings of this study have the potential to enhance rice productivity and stress tolerance, offering solutions to improve food security and sustainability in agricultural practices, particularly in regions affected by environmental stressors.

Delineating drought-induced antioxidative traits as potential mechanisms for climate resilience in Argania spinosa

Drought stress ranks among the most critical environmental challenges facing agriculture today, causing significant impairments to plant growth and development. In Morocco, these negative impacts are projected to intensify further under the combined pressures of climate change and the worsening water shortage crisis. The imperative need for sustainable arganiculture (cultivation of Argane trees) in dry lands necessitates the expeditious identification of drought-tolerant elite Argania spinosa trees. In this context, we investigated the drought tolerance of 2-year-old A. spinosa seedlings from two contrasting provenances Lakhssas (LKS) and Aoulouz (ALZ) under severe stress by evaluating their antioxidative defense mechanisms. A total of 24 parameters related to reactive oxygen species (ROS), oxidative damage, and enzymatic and non-enzymatic antioxidant defense were measured and compared between both provenances. The results showed that the drought-stressed conditions significantly increased the activity of enzymatic antioxidants, including superoxide dismutase, catalase, peroxidase, polyphenoloxidase, glutathione peroxidase, glutathione S-transferase, and ascorbate-glutathione cycle enzymes, as well as the content of non-enzymatic antioxidants, including reduced glutathione (GSH), ascorbic acid (AsA), α-Tocopherols (α-toc), polyphenols, anthocyanins, and group thiols. The ability of A. spinosa trees to greatly enhance their antioxidant system to limit cellular damage caused by ROS production might be an important attribute linked to drought tolerance. Regarding the inter-provenance variation under drought stress conditions, LKS provenance exhibited superior antioxidative capacity through enhanced AsA-GSH cycle activity and elevated levels of AsA-GSH, α-toc, and polyphenols. However, ALZ demonstrated elevated anthocyanin levels and reduced peroxidative stress markers (hydrogen peroxide and malonyldialdehyde). Significant and positive correlations were recorded between studied ROS and antioxidants. Investigating the multifaceted antioxidative defense system underpinning drought tolerance in A. spinosa can facilitate the identification of drought-tolerant argane trees for the development of a future breeding program allowing sustainable arganiculture in dry lands.

Silicon nanoparticles (SiNPs) mediate GABA, SOD and ASA-GSH cycle to improve cd stress tolerance in Solanum lycopersicum

Contamination of agricultural products with Cadmium (Cd) is a global problem that should be considered for minimizing the risks to human health. Considering the potential effects of SiNPs in decreasing abiotic stress, a study was conducted to investigate the effect of SiNPs in the reduction of Cd stress on Solanum lycopersicum. SiNPs was used at 0, 25, 50 and 100 mg/l and CdCl2 at 0, 100 and 200 µM concentrations. The results showed that Cd stress caused a significant decrease in dry weight, content of GSH, ASA, significently increasing the activity of GR, APX, GST, SOD, as well as content of H2O2, MDA, proline, and GABA in shoots and roots compared to the control. SiNPs significantly increased shoot and root dry weight compared to the control. As a coenzyme, SiNPs induced the activity of antioxidant enzymes and significantly increased GST and GR gene expression compared to the control. SiNPs also caused a substantial increase in the content of ASA, GSH, proline and GABA compared to the control. By inducing the activity of antioxidant enzymes and metabolites of the ascorbate-glutathione (ASA-GSH) cycle, SiNPs removed a large content of H2O2 and significantly reduced the MDA content, and as a result led to the stability of cell membrane under Cd stress. Induction of ASA-GSH, GABA and SOD cycle by SiNPs clearly showed that SiNPs could be a potential tool to alleviate Cd stress in plants cultivated in areas contaminated with this heavy metal.

Salicylic Acid Treatment Ameliorates Postharvest Quality Deterioration in 'France' Prune (Prunus domestica L. 'Ximei') Fruit by Modulating the Antioxidant System.

The potential of salicylic acid (SA) in delaying postharvest fruit senescence has been extensively documented; nevertheless, its effect on antioxidant activity and quality of 'France' prune fruit is largely unknown. The study investigated the effects of SA (0.5 mM) on postharvest quality deterioration of 'France' prune fruit. Results indicated that SA impeded the increase in respiration rate and weight loss, and mitigated the decrease of soluble solids content (SSC), titratable acidity (TA) content, firmness, and hue angle. SA sustained the ascorbate-glutathione cycle by inducing the production of ascorbic acid (AsA) and glutathione (GSH) and attenuates flavonoids, total phenols, and anthocyanins degradation by inhibiting polyphenol oxidase (PPO) activity and PdPPO. Moreover, SA significantly improved superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), peroxidase (POD), and glutathione reductase (GR) activities and gene expression levels, sustained higher 2,2'-Azinobis-(3-ethylbenzthiazoline-6-sulphonate) (ABTS) and 1,1-diphenyl-2-picryl-hydrazyl (DPPH) free radical scavenging capacity, ferric reducing antioxidant power (FRAP), and hydroxyl radical (·OH) inhibition capacity, and impeded the production of hydrogen peroxide (H2O2) and superoxide anion (O2•-). Overall, SA improved the antioxidant capacity by inducing the synthesis of defense response-related substances and promoting antioxidant enzyme activities to sustain the storage quality of 'France' prune fruit.

Phosphorus-induced restructuring of the ascorbate-glutathione cycle and lignin biosynthesis alleviates manganese toxicity in peach roots.

Manganese (Mn) is indispensable for plant growth, but its excessive uptake in acidic soils leads to toxicity, hampering food safety. Phosphorus (P) application is known to mitigate Mn toxicity, yet the underlying molecular mechanism remains elusive. Here, we conducted physiological and transcriptomic analyses of peach roots response to P supply under Mn toxicity. Manganese treatment disrupted root architecture and caused ultrastructural damage due to oxidative injury. Notably, P application ameliorated the detrimental effects and improved the damaged roots by preventing the shrinkage of cortical cells, epidermis and endodermis, as well as reducing the accumulation of reactive oxygen species (ROS). Transcriptomic analysis revealed the differentially expressed genes enriched in phenylpropanoid biosynthesis, cysteine, methionine and glutathione metabolism under Mn and P treatments. Phosphorus application upregulated the transcripts and activities of core enzymes crucial for lignin biosynthesis, enhancing cell wall integrity. Furthermore, P treatment activated ascorbate-glutathione cycle, augmenting ROS detoxification. Additionally, under Mn toxicity, P application downregulated Mn uptake transporter while enhancing vacuolar sequestration transporter transcripts, reducing Mn uptake and facilitating vacuolar storage. Collectively, P application prevents Mn accumulation in roots by modulating Mn transporters, bolstering lignin biosynthesis and attenuating oxidative stress, thereby improving root growth under Mn toxicity. Our findings provide novel insights into the mechanism of P-mediated alleviation of Mn stress and strategies for managing metal toxicity in peach orchards.

Antioxidant and biofertilizing effect of compost extracts on horticultural crops to minimize the use of agrochemicals

Excessive chemical fertilizers harm the environment, economy, and health, while compost and its extracts provide a sustainable solution. Consequently, the development of liquid organic amendments with biofertilizing and antioxidant capabilities is of significant interest in intensive agriculture. To achieve this, four Compost Extraction Protocols (CEP1–4) were applied to different compost to obtain a range of aqueous extracts. These treatments varied in temperature, incubation duration, and agitation. The raw materials for the compost used were Agri-food Waste (AW), Sewage Sludge (SS), Vegetable Waste (VW), and Olive Mill Waste (OMW). The extracts were characterized in physicochemical terms and their potential to promote radicle germination in cucumber and lettuce seeds. Additionally, counts of microbial groups associated with biofertilizing capacity were conducted. Three extracts were chosen based on the germination index to conduct an in vivo bioassay on seedlings. Finally, oxidative stress in radicles and seedlings resulting from the preceding tests was evaluated by quantifying malondialdehyde (MDA), total phenolic compounds (TPC), and ascorbate-glutathione cycle enzymes. The results established that protocols with milder temperatures, such as CEP1 and CEP4, yielded aqueous compost extracts with good biofertilizing and antioxidant properties, although the effect was dependent on crop sensitivity. Specifically, the extracts selected for the seedling trial, OMW-A CEP4, AW-A CEP1, and especially AW-A CEP4, demonstrated a remarkable biofertilizing and antioxidant properties in lettuce, by increasing growth parameters and TPC while decreasing MDA. The results indicate that aqueous compost extracts are a suitable alternative to reduce the consumption of chemical fertilizers.

Regulation of arsenate stress by nitric oxide and hydrogen sulfide in Oryza sativa seedlings: Implication of sulfur assimilation, glutathione biosynthesis, and the ascorbate-glutathione cycle and its genes

Seed priming by nitric oxide (NO) and hydrogen sulphide (H2S) in combating against abiotic stress in plants is well documented. However, knowledge of fundamental mechanisms of their crosstalk is scrambled. Therefore, the reported study examined the probable role of NO and H2S in the mitigation of arsenate toxicity (As(V)) in rice seedlings and whether their potential signalling routes crossover. Results report that As(V) toxicity limited shoot and root length growth with more As accumulation in roots. As(V) further caused elevated reactive oxygen species levels, inhibited ascorbate-glutathione cycle enzymes and relative gene expression of its enzymes and thus, causing lipid and protein oxidation. These results correlate with reduced nitric oxide synthase-like and L–cysteine desulfhydrase activity along with endogenous NO and H2S. While, L-NAME or PAG augmented As(V) toxicity, and addition of SNP or NaHS effectively reversed their respective effects. Furthermore, SNP under PAG or NaHS under L-NAME were able to pacify As(V) stress, implicating that endogenous NO and H2S efficiently ameliorate As(V) toxicity but without their shared signaling in rice seedlings.

Comparison on stress memory of two Hypnaceae moss species to haze

Abstract Industrialization and the rapid growth of economies have caused severe environmental pollution, which might impact the survival of sensitive species. In this study, we investigated the defense responses of two common mosses with varying anti-haze capacities, Hypnum callichroum and Homomallium incurvatum, in response to simulated haze pollution. Photoprotection and antioxidant mechanisms of both mosses were measured immediately after the first exposure to the haze treatment, followed by the initial recovery stage and again after exposure to secondary stress and secondary recovery. Haze exposure caused severe oxidative stress and photodamage in both H. callichroum and H. incurvatum. Metabolic processes such as photorespiration, the ascorbate–glutathione cycle, and secondary metabolism—which play roles in defense responses—were significantly activated in both moss species after haze treatment. During the recovery following haze stress, H. callichroum exhibited a significant stress memory response, as evidenced by the greater accumulation of several memory substances, including xanthophylls and phenolic acids. However, H. incurvatum did not exhibit a strong stress memory response, which might explain its relatively inferior anti-haze capacity in the natural environment.

Effects of Drought at Anthesis on Flag Leaf Physiology and Gene Expression in Diverse Wheat (Triticum aestivum L.) Genotypes

The current study aimed to quantify the effects of two drought intensities achieved by deprivation of watering for 45 and 65% of the volumetric soil moisture content (VSMC) for 14 days after wheat anthesis to identify physio-biochemical and molecular changes associated with drought tolerance in six genotypes with different drought tolerance. Drought at 65% of VSMC induced a significant decrease in the chlorophyll a content in the drought-sensitive genotype, which indicated a strong loss of photosynthetic reaction centres. Further, in the drought-tolerant genotype, the content of carotenoids, which could play a vital role in resisting water shortage stress, tended to increase. The increased production of malondialdehyde showed that the antioxidant system in the drought-sensitive genotypes was not properly activated. A significant decrease in catalase (CAT; EC 1.11.1.6) was observed at a 45% reduction in VSMC, compared to the control, in the drought-sensitive genotype, and at a reduction in VSMC of 65%, in all medium sensitive genotypes. Further, the drought-tolerant and -medium tolerant genotypes responded to drought with a decline in total glutathione concentrations with the intention to reinforce their defence system. Thereby, dehydroascorbate reductase (DHAR; EC 1.8.5.1), monodehydroascorbate reductase (MDHAR; EC 1.6.5.4), and glutathione reductase (GR; EC 1.6.4.2) were critical enzymes involved in the ascorbate–glutathione cycle together with CAT, showing their main role in the detoxification of ROS produced with the reduction in VSMC by 65%. The results of gene expression analysis showed that severe drought increased the levels of the DHN5 and WZY2 genes (that were significantly positively correlated) in the drought-tolerant genotype, whose grain weight, area, and length did not change in maturity. Also, it was seen that DHN5 expression showed a significant positive correlation with grain length and proline content at a 45% reduction in VSMC. The identification of different mechanisms under drought can contribute to the selection of drought-tolerant genotypes.

Responsive mechanism of Hemerocallis citrina Baroni to complex saline-alkali stress revealed by photosynthetic characteristics and antioxidant regulation.

Saline-alkali stress induces oxidative damage and photosynthesis inhibition in H. citrina, with a significant downregulation of the expression of photosynthesis- and antioxidant-related genes at high concentration. Soil salinization is a severe abiotic stress that impacts the growth and development of plants. In this study, Hemerocallis citrina Baroni was used to investigate its responsive mechanism to complex saline-alkali stress (NaCl:Na2SO4:NaHCO3:Na2CO3 = 1:9:9:1) for the first time. The growth phenotype, photoprotective mechanism, and antioxidant system of H. citrina were studied combining physiological and transcriptomic techniques. KEGG enrichment and GO analyses revealed significant enrichments of genes related to photosynthesis, chlorophyll degradation and antioxidant enzyme activities, respectively. Moreover, weighted gene co-expression network analysis (WGCNA) found that saline-alkali stress remarkably affected the photosynthetic characteristics and antioxidant system. A total of 29 key genes related to photosynthesis and 29 key genes related to antioxidant enzymes were discovered. High-concentration (250mmolL-1) stress notably inhibited the expression levels of genes related to light-harvesting complex proteins, photosystem reaction center activity, electron transfer, chlorophyll synthesis, and Calvin cycle in H. citrina leaves. However, most of them were insignificantly changed under low-concentration (100mmolL-1) stress. In addition, H. citrina leaves under saline-alkali stress exhibited yellow-brown necrotic spots, increased cell membrane permeability and accumulation of reactive oxygen species (ROS) as well as osmolytes. Under 100mmolL-1 stress, ROS was eliminate by enhancing the activities of antioxidant enzymes. Nevertheless, 250mmolL-1 stress down-regulated the expression levels of genes encoding antioxidant enzymes, and key enzymes in ascorbate-glutathione (AsA-GSH) cycle as well as thioredoxin-peroxiredoxin (Trx-Prx) pathway, thus inhibiting the activities of these enzymes. In conclusion, 250mmolL-1 saline-alkali stress caused severe damage to H. citrina mainly by inhibiting photosynthesis and ROS scavenging capacity.

Atmospheric NO2 enhances tolerance to low temperature by promoting nitrogen and carbon metabolism in tobacco

With abnormal global climate change and the frequent occurrence of extreme weather, low-temperature stress poses an increasingly serious threat to the diversity of plants. Low temperatures accompanied by limitations in nitrogen cause a series of morphological, physiological, and molecular changes in plants. Nitrogen dioxide (NO2) is a gas that is considered to be a toxic air pollutant. However, NO2 in the atmosphere can be absorbed by plants and participate in nitrogen metabolism. In this study, tobacco (Nicotiana tabacum L.) seedlings were fumigated with a concentration of 4 µL·L−1 NO2 at 4 ℃ for 10 days. NO2 promoted the glutamine synthetase-glutamate synthase (GS/GOGAT) pathway in the leaves at low temperatures, which transforms more organic nitrogen that can be directly utilized by the plants, and improves the skeleton for carbon metabolism. Moreover, gamma-aminobutyric acid (GABA) was generated through the ornithine and glutamate pathways, and the biosynthesis of proline was also enhanced after treatment with NO2. Together, these compounds regulate the osmotic balance of tobacco leaf cells under low-temperature stress. NO2 activated the ascorbate-glutathione (AsA-GSH) cycle in the leaves under low-temperature stress, and this antioxidant enzyme system synergistically removed the intracellular free radicals that result from reactive oxygen species. Additionally, NO2 significantly increased the content of nitric oxide (NO) in the leaves under low-temperature stress and enhanced the opening of stomata, thus, improving photosynthesis in the leaves. The biosynthesis of chlorophyll in the leaves was inhibited by low-temperature stress, but NO2 promotes the biosynthesis of chlorophyll directly or through the nitric acid signaling pathway and improves the ability of plants to capture light energy. NO2 also alleviates the photoinhibition induced by cold stress by regulating photosynthetic electron transfer and absorbing more energy for the assimilation of photosynthetic carbon. This improves the photochemical efficiency of tobacco leaves. In conclusion, NO2 enhanced the tolerance of tobacco seedlings to low temperature by regulating nitrogen metabolism, the osmotic balance, antioxidant system, and photosynthesis.

Carnitine modulates antioxidative defense in ABI2 mutant under salt stress

Carnitine, a ubiquitous compound in living organisms, fulfills diverse roles in energy metabolism, stress resilience, and detoxification. Its antioxidant and osmolyte traits offer relief to stressed plants. Antagonizing abscisic acid (ABA), carnitine influences ABA-responsive genes. Our study, using Arabidopsis thaliana wild-type Ler. (Landsberg erecta) and ABA-insensitive abi2-1 mutants, explored carnitine’s impact on antioxidative responses and ABI2’s role in salt-induced carnitine metabolism. The application of 5 µM carnitine has alleviated the decrease in RWC, shoot weight, and rosette diameter WT plants caused by 80 mM salt stress for 4 days. Carnitine reduced cell membrane damage and salinity effects, evidenced by decreased lipid peroxidation and H2O2. In contrast, the impaired ABI2 of abi2-1, due to deficient phosphatase activity, further exacerbated the inhibitory effect of carnitine on the enzymes of the ascorbate-glutathione cycle, consequently reducing stress mitigation. While abi2-1 mutants exhibited unchanged superoxide dismutase (SOD) activity, they demonstrated increased catalase and peroxidase activity following carnitine treatment under salt stress compared to WT plants. Conversely, wild-type WT plants treated with carnitine exhibited elevated total glutathione content under salt stress, a response not observed in abi2-1 mutants under carnitine treatment. These results underscore the crucial role of ABI2-dependent ABA signaling in regulating plant carnitine metabolism.

Enhancing maize resilience to microplastics and cadmium through nanoparticles intervention

Microplastic (MPs) and heavy metals (HMs) pollution present significant ecological and environmental threats due to their widespread production and release into natural ecosystems. This study aimed to investigate the individual effects of polyvinyl chloride microplastics (PVC-MPs) and cadmium (Cd) on various aspects of plant growth, as well as the potential ameliorative role of titanium dioxide nanoparticles (TiO2 NPs) in mitigating their adverse impacts. The experiment involved exposing maize seedlings to different concentrations of PVC-MPs (0, 2, and 4 mg L−1) and Cd (0, 50, and 100 mg kg−1), along with varying levels of TiO2NPs (50 µg mL−1). Our findings showed that Cd toxicity in the soil significantly reduced growth, gas exchange properties, sugar content, ascorbate-glutathione (ASA-GSH) cycle activity, cellular composition, and proline metabolism in maize. In contrast, Cd contaminating greatly boosted oxidative stress indicators, enzymatic and non-enzymatic antioxidants, and gene expression in maize. Stimulatingly, the use of TiO2NPs caused in a significant development in growth of plant, plant biomass, gas exchange parameters, enzymatic antioxidants and non-enzymatic antioxidant activity, and gene expressions of antioxidants enzymes, lowering oxidative stress (MDA and H2O2) and Cd absorption in maize plants. Furthermore, TiO2NPs increased cellular fractionation (cellulose and hemicellulose), altering proline metabolism and ASA-GSH cycle activity in maize plants. Overall, this work emphasizes the intricate interactions between MPs and Cd, and nanoparticles in plant systems, highlighting TiO2NPs as a possible strategy for increasing plant flexibility and minimizing the negative effects of environmental pollutants. These findings have crucial implications regarding the development of long-term agricultural management approaches in polluted areas.

Dose-dependent regulation of morphological, physio-biochemical, nutritional, and metabolic responses by cobalt in Tagestes erecta L. plants exposed to salinity stress

Salinity is a major concern globally and causing reduction in crop growth and development thereby lowering food production. Interestingly, cobalt (Co), a multifunctional non-essential micro-element, has an important role in improving growth and development under salinity stress. In the current study, the effects of Co on the morphological, biochemical, nutritional, and metabolic changes of African marigold plants at two salinity levels were assessed. Two concentrations of Co (C1; 10 mg/L and C2; 20 mg/L) were applied as foliar application to the marigold plants under salinity (S1; 300 mM and S2; 600 mM) stress. The results indicated that salinity substantially reduced the growth by negatively affecting the nutritional and metabolic profile. Interestingly, the C1 application mitigated the salinity effects and improved all the studied parameters including vegetative, nutritional, biochemical and metabolites (amino acids, fatty acids, organic acids, sugars, carotenoids, flavonoids, and terpenoids) by reducing the reactive oxygen species (ROS) and methylglyoxal (MG)-induced oxidative stress, at two salinity levels. The overall results revealed that C1was an ideal dose for marigold plants undergoing salinity stress since C2 application showed some toxicity symptoms under both the salinity levels; with reduced growth and impaired development. Based on the observations, the two different oxidative stress scavenging pathways in marigold are discussed i.e. ROS-scavenging by ascorbate-glutathione (AsA-GSH) cycle and the MG-detoxification by glyoxalase. With the limitations imposed upon the glutathione (GSH) pool size and redox homeostasis, the study indicated that GSH played a critical role in both ROS- and MG-detoxification in marigold plants at both salinity levels.