Antioxidant Ascorbate Research Articles

Ascorbate-glutathione cycle and thioredoxin system are involved in nitric oxide alleviating excess nitrate stress in tomato seedlings

ABSTRACT Nitric oxide (NO) plays an important role in plant growth, development, and stress responses. The exogenous NO donor sodium nitroprusside (SNP) increased the plant height, root length, and biomass of tomato seedlings under nitrate stress, especially 100 μM SNP. The reactive oxygen species (ROS) and malondialdehyde (MDA) contents were decreased, while the antioxidant enzyme activities, ascorbate and glutathione contents, and expression of SlTrxh, SlNTRB, SlTpx were increased in tomato after SNP and nitrate stress treatment, compared with nitrate stress. The tomato plants showed shorter root length, more MDA and ROS contents after the NADPH-dependent thioredoxin reductase (NTR) inhibitor Auranofin (ANF) was added, suggesting that ANF inhibited the alleviating effect of NO under nitrate stress. The NO and S-nitrosothiol (SNO) contents and the SlNR transcript levels were decreased and the expression of SlGLB, SlGSNOR was increased after NO and nitrate stress treatment. The S-nitrosylated level in tomato roots was increased after nitrate stress. The SlMDHAR, SlTrxh, and SlNTRB protein were S-nitrosylated after NO and nitrate stress treatment. These results suggested that key enzymes in ascorbate-glutathione cycle and Trx system played an important role in alleviating the effect of NO in tomato seedlings under nitrate stress involving the S-nitrosylation modification.

Physiological and Transcriptomic Analyses Reveal the Effects of Carbon-Ion Beam on Taraxacum kok-saghyz Rodin Adventitious Buds.

Taraxacum kok-saghyz Rodin (TKS) has great potential as an alternative natural-rubber (NR)-producing crop. The germplasm innovation of TKS still faces great challenges due to its self-incompatibility. Carbon-ion beam (CIB) irradiation is a powerful and non-species-specific physical method for mutation creation. Thus far, the CIB has not been utilized in TKS. To better inform future mutation breeding for TKS by the CIB and provide a basis for dose-selection, adventitious buds, which not only can avoid high levels of heterozygosity, but also further improve breeding efficiency, were irradiated here, and the dynamic changes of the growth and physiologic parameters, as well as gene expression pattern were profiled, comprehensively. The results showed that the CIB (5-40 Gy) caused significant biological effects on TKS, exhibiting inhibitory effects on the fresh weight and the number of regenerated buds and roots. Then,15 Gy was chosen for further study after comprehensive consideration. CIB-15 Gy resulted in significant oxidative damages (hydroxyl radical (OH•) generation activity, 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical-scavenging activity and malondialdehyde (MDA) content) and activated the antioxidant system (superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), and ascorbate peroxidase (APX)) of TKS. Based on RNA-seq analysis, the number of differentially expressed genes (DEGs) peaked at 2 h after CIB irradiation. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis revealed that DNA-replication-/repair- (mainly up-regulated), cell-death- (mainly up-regulated), plant-hormone- (auxin and cytokinin, which are related to plant morphogenesis, were mainly down-regulated), and photosynthesis- (mainly down-regulated) related pathways were involved in the response to the CIB. Furthermore, CIB irradiation can also up-regulate the genes involved in NR metabolism, which provides an alternative strategy to elevate the NR production in TKS in the future. These findings are helpful to understand the radiation response mechanism and further guide the future mutation breeding for TKS by the CIB.

Biochemical changes of rice genotypes against blast (Magnaporthe oryzae) disease and SSR marker validation for resistance genes

Rice blast caused by Magnoporthe oryzae is a major devastating fungal disease and represents a potential threat to world rice productions. However, information about the genetic and biochemical basis of disease tolerance is still limited. In this study, we tested the presence and diversity of resistant R genes using SSR markers, and the antioxidant enzymes catalase (CAT), ascorbate peroxidise (APX) and guaicol peroxidise (POD), activity and also the concentration of hydrogen peroxide (H2O2) and malondialdehyde (MDA) in resistant (BAUdhan 3) and susceptible (BRRIdhan 28) genotype. Molecular marker analysis reveals the presence of all ten studied resistant genes in BAUdhan 3. Among the markers studied, three markers namely RM224, RM72 and RM206 produce distinct band only in resistant genotype BAUdhan 3, which might be used to screen resistant genotypes. The enzymatic activity of APX, CAT and POD increased in the inoculated plant for both cultivars but the increase was more prominent for BAUdhan 3. The M. oryzae infections significantly increased the H2O2 content in BRRIdhan 28 and not much changed in BAUdhan 3. The MDA concentration was higher in the leaves of inoculated plants of BRRIdhan 28. The higher activities of APX and POD in the leaves of the inoculated plants of BAUdhan 3 resulted in lower H2O2 accumulation which can minimize the cellular damages possibly caused by reactive oxygen species. The result shows that the presence of more resistance genes and an effective antioxidative system in BAUdhan 3, which limits the damage caused due to fungal infection and thus contributes to greater resistance.

Genome-wide identification of NF-Y gene family in maize (Zea mays L.) and the positive role of ZmNF-YC12 in drought resistance and recovery ability.

Nuclear factor Y (NF-Y) genes play important roles in many biological processes, such as leaf growth, nitrogen nutrition, and drought resistance. However, the biological functions of these transcription factor family members have not been systematically analyzed in maize. In the present study, a total of 52 ZmNF-Y genes were identified and classified into three groups in the maize genome. An analysis of the evolutionary relationship, gene structure, and conserved motifs of these genes supports the evolutionary conservation of NF-Y family genes in maize. The tissue expression profiles based on RNA-seq data showed that all genes apart from ZmNF-Y16, ZmNF-YC15, and ZmNF-YC17 were expressed in different maize tissues. A weighted correlation network analysis was conducted and a gene co expression network method was used to analyze the transcriptome sequencing results; six core genes responding to drought and rewatering were identified. A real time fluorescence quantitative analysis showed that these six genes responded to high temperature, drought, high salt, and abscisic acid (ABA) treatments, and subsequent restoration to normal levels. ZmNF-YC12 was highly induced by drought and rewatering treatments. The ZmNF-YC12 protein was localized in the nucleus, and the Gal4-LexA/UAS system and a transactivation analysis demonstrated that ZmNF-YC12 in maize (Zea mays L.) is a transcriptional activator that regulates drought resistance and recovery ability. Silencing ZmNF-YC12 reduced net photosynthesis, chlorophyll content, antioxidant (superoxide dismutase, catalase, peroxidase and ascorbate peroxidase) system activation, and soluble protein and proline contents; it increased the malondialdehyde content, the relative water content, and the water loss rate, which weakened drought resistance and the recoverability of maize. These results provide insights into understanding the evolution of ZmNF-Y family genes in maize and their potential roles in genetic improvement. Our work provides a foundation for subsequent functional studies of the NF-Y gene family and provides deep insights into the role of the ZmNF-YC12 regulatory network in controlling drought resistance and the recoverability of maize.

Antioxidant enzyme activity associated to Meloidogyne and Pratylenchus infection in sugarcane

The plant-parasitic nematodes Meloidogyne and Pratylenchus are the main nematode pathogens reducing sugarcane yield worldwide. Despite, defense responses to overcome the pathogen stresses through neutralizing cytotoxicity of reactive oxygen species (ROS) have been reported for a range of important crops and pathogens, few studies have been developed for sugarcane under nematode stress. The aim of this study was to evaluate responses of the antioxidant enzymes superoxide dismutase (SOD) and ascorbate peroxidase (APX) at different density of Meloidogyne and Pratylenchus in a sugarcane replant field and in a ratoon crop. Evaluations based on nematode densities, plant growth parameters and SOD and APX activity at six (T6) and nine (T9) months after planting (Area 1) or cutting (Area 2 - ratoon crop). Pratylenchus abundance significantly decreased in Area 1, but not in Area 2. In contrast, Meloidogyne abundance increased through time in Area 1, but decreased in Area 2. In both areas, SOD activity decreased over time, but APX activity did not present significant fluctuation over time in Area 1, in contrast to the increase over time of APX activity in Area 2. Abundance of both nematodes correlated positively with number of tillers and negatively with height of stalks, besides the negative correlation between Pratylenchus and stalk diameter. This inverse correlation between the plant-parasitic nematode and stalk number was also demonstrated by the PCA. There was not significant correlation between the antioxidant enzymes and plant growth parameters or nematode abundance, except the positive correlation between SOD activity and number of tillers.

Future Climate CO2 Reduces the Tungsten Effect in Rye Plants: A Growth and Biochemical Study.

Heavy metal pollution is one of the major agronomic challenges. Tungsten (W) exposure leads to its accumulation in plants, which in turn reduces plant growth, inhibits photosynthesis and induces oxidative damage. In addition, the predicted increase in CO2 could boost plant growth under both optimal and heavy metal stress conditions. The aim of the present study was to investigate the effect of W on growth, photosynthetic parameters, oxidative stress and redox status in rye plants under ambient and elevated (eCO2) levels. To this end, rye plants were grown under the following conditions: ambient CO2 (aCO2, 420 ppm), elevated CO2 (eCO2, 720 ppm), W stress (350 mg kg-1 soil) and W+eCO2. W stress induced significant (p < 0.05) decreases in growth and photosynthesis, increases in oxidative damages (lipid peroxidation) and the antioxidant defense system, i.e., ascorbate (ASC), reduced glutathione (GSH), GSH reductase (GR), peroxidase (POX), catalase (CAT), superoxide dismutase (SOD), ASC peroxide (APX) and dehydroascorbate reductase (DHAR). On the other hand, eCO2 decreased W uptake and improved photosynthesis, which sequentially improved plant growth. The obtained results showed that eCO2 can decrease the phytotoxicity risks of W in rye plants. This positive impact of eCO2 on reducing the negative effects of soil W was related to their ability to enhance plant photosynthesis, which in turn provided energy and a carbon source for scavenging the reactive oxygen species (ROS) accumulation caused by soil W stress.

Effects of SiO2 nanoparticles on root structures, gas exchange, and antioxidant activities of Cunninghamia lanceolata seedlings under drought stress

Increasing evidence shows that silicon possesses important physiological functions in plants, thus, silicon fertilizers are used widely in agriculture. However, few attentions were paid on the effects of silicon dioxide nanoparticles (SiO2NPs) on plant growth and resistance to abiotic stresses. In this present study, different amount of SiO2NPs were applied in pots with Cunninghamia lanceolata seedlings, and their root development, gas exchange, and drought resistance were investigated. These results showed that SiO2NPs treatment increased total root length, root volume, and the numbers of root tips of these seedlings under drought stress. Specific root area (SRA) and specific root length (SRL) also increased. SiO2NPs treatment altered anatomical structures of the first-order lateral roots of C. lanceolata seedlings under drought stress (i.e., increase in cortex thickness and the number of cortex layers). Under drought stress, SiO2NPs treatment increased net photosynthetic rates, stomatal conductance, intercellular CO2 concentration, and transpiration. SiO2NPs treatment also led to increase in light use efficiency and instantaneous Rubisco carboxylation rate and decrease in water use efficiency under drought stress. Under drought stress, SiO2NPs treatment resulted in increased activities of antioxidant enzymes (superoxide dismutase, catase, and peroxidase) and concentrations of antioxidants (ascorbate and glutathione), decreasing oxidative damage caused by drought stress. All together, these results suggested that SiO2NPs could be used for seedling culture of forest trees.

Transcriptomics and metabolomics provide insight into the anti-browning mechanism of selenium in freshly cut apples.

Enzymatic browning has a considerable negative impact on the acceptability and marketability of freshly cut apples. However, the molecular mechanism by which selenium (Se) positively affects freshly cut apples in this regard is not yet clear. In this study, 0.75 kg/plant of Se-enriched organic fertilizer was applied to "Fuji" apple trees during the young fruit stage (M5, May 25), the early fruit enlargement stage (M6, June 25), and the fruit enlargement stage (M7, July 25), respectively. The same amount of Se-free organic fertilizer was applied as a control. Herein, the regulatory mechanism by which exogenous Se exerts its anti-browning effect in freshly cut apples was investigated. The results showed that the M7 treatment applied in Se-reinforced apples could remarkably inhibit their browning at 1h after being freshly cut. Additionally, the expression of polyphenol oxidase (PPO) and peroxidase (POD) genes treated with exogenous Se was significantly reduced compared to controls. Moreover, the lipoxygenase (LOX) and phospholipase D (PLD) genes, which are involved in membrane lipid oxidation, were expressed at higher levels in the control. The gene expression levels of the antioxidant enzymes catalase (CAT), superoxide dismutase (SOD), glutathione S-transferase (GST), and ascorbate peroxidase (APX) were upregulated in the different exogenous Se treatment groups. Similarly, the main metabolites measured during the browning process were phenols and lipids; thus, it could be speculated that the mechanism by which exogenous Se produces its anti-browning effect may be by reducing phenolase activity, improving the antioxidant capacity of the fruits, and alleviating membrane lipid peroxidation. In summary, this study provides evidence regarding and insight into the response mechanism employed by exogenous Se to inhibit browning in freshly cut apples.

Early Physiological, Cytological and Antioxidative Responses of the Edible Halophyte Chenopodium quinoa Exposed to Salt Stress.

Quinoa (Chenopodium quinoa Willd.) is a plant of South American origin recently valorized for its nutritional and nutraceutical properties in human diet. Quinoa is cultivated in many parts of the world, with a selection of varieties with good adaptability to extreme climatic conditions and salt stress. The variety Red Faro, native to southern Chile but harvested in Tunisia, was considered for salt stress resistance, considering its seed germination and 10-day seedling growth at increasing doses of NaCl (0, 100, 200 and 300 mM). Seedlings were spectrophotometrically analyzed for antioxidant secondary metabolites (polyphenols, flavonoids, flavonols and anthocyanins), antioxidant capacity (ORAC, oxygen radical absorbance capacity, DPPH*, 2,2-diphenyl-1-pic-rylhydrazyl), antioxidant enzyme activity (superoxide dismutase (SOD), guaiacol peroxidase (GPX), ascorbate peroxidase (APX) and catalase (CAT)) and mineral nutrient content in root and shoot tissues. Cytogenetic analysis of root tip was performed to check for meristematic activity and the possible presence of chromosomal abnormalities induced by salt stress. The results indicated a general increase in antioxidant molecules and antioxidant enzymes NaCl dose-dependent, no effects on seed germination but negative effects on seedling growth, and little effect on root meristems mitotic activity. These results indicated that stress conditions can induce an increase in biologically active molecules that could be used for nutraceutical purposes.

Synergistic effect of trans-zeatin and silymarin on mitigation of cadmium stress in chili pepper through modulating the activity of antioxidant enzymes and gene expressions

Many human activities, including waste disposal and the use of synthetic phosphate fertilizers, increase the concentration of cadmium (Cd) in the environment and harm plants and human health. Therefore, it is imperative to find effective solutions to overcome this problem. As plant biostimulants, trans-zeatin-type cytokinin (tr-Z) and silymarin (Sm) can act as anti-heavy metal agents, effectively ameliorating Cd damage to plants. In a pot trial, the impacts of foliar treatment with tr-Z (40 μM), Sm (400 μM), or tr-Z + Sm (25 +250 μM, respectively, applied sequentially) on biomass production, yield, photosynthetic efficiency, osmoregulators, antioxidative defense system, and transcript levels of enzyme-related genes of chili pepper under normal or Cd (500 μM) stress were investigated. Cadmium stress elevated the levels of superoxide (O2•), hydrogen peroxide (H2O2), electrolyte leakage (EL), malondialdehyde (MDA), and Cd, while negatively affecting biomass production, photosynthetic efficiency, and defense system components. Exogenous tr-Z and/or Sm attenuated the Cd-induced negative impacts on plants, highlighting that the integrative tr-Z + Sm treatment was more efficient than the single treatments. The tr-Z + Sm treatment decreased contents of roots, shoot, and fruit Cd by 66–91%, and reduced levels of O2• and H2O2, MDA, and EL by 45%, 73%, 51%, and 72%, respectively, correlated with increased tr-Z and Sm contents by 38–66%. Exogenous tr-Z + Sm increased biomass production by 99–134%, photosynthetic efficiency attributes by 31–169%, and antioxidants (ascorbate, proline, glutathione, and phenolics) by 33–123%. The levels of proteins and total leaf and fruit capsaicin were higher in Cd-stressed plants treated with tr-Z + Sm. Furthermore, the co-application of tr-Z + Sm up-regulated the activities of superoxide dismutase (SOD), glutathione reductase (GR), ascorbate peroxidase (APX), and catalase (CAT) enzymes by 38–43%, and maximized transcript level of genes-encoding enzymes in stress-exposed plants. As a result, the integrative tr-Z + Sm treatment is highly recommended to mitigate Cd stress impacts in chili pepper plants.

Modulation of Antioxidant Defense Mechanisms and Morpho-Physiological Attributes of Wheat through Exogenous Application of Silicon and Melatonin under Water Deficit Conditions

Although the individual influences of silicon (Si) and melatonin (MT) have been widely studied under various abiotic stresses, little is known about their interaction under drought stress. In this study, an experiment in pots was carried out to investigate the potential of an individual or combined foliar application of silicon (Si) and melatonin (ML) (control (ck), water spray, 4.0 mM Si, 200 µM ML, and 4.0 mM Si + 200 µM ML) on wheat grown at two different water-holding capacity levels (80% well-water condition and 40% drought stress) in order to check of grain yield and some important physiological characteristics. Under drought stress conditions, grain yield and yield attributes, water content and photosynthetic efficiency of wheat crops were significantly decreased. Application of Si+ ML significantly improved leaf pigments (Chl a, Chl b and Chll a + b), leaf relative water content (RWC), proline, total soluble sugars, and total soluble protein. As well as, the activities of important antioxidant enzymes, including catalase (CAT), superoxide dismutase (SOD), peroxidase (POD) and ascorbate peroxidase (APX) were effectively boosted through the combined application of Si + ML. This improvement was correlated with an obvious decrease in the levels of MDA, H2O2, and electrolyte leakage and increased water use efficiency. Conclusively, the combination of Si + ML significantly enhanced the 20.21% yield and various morpho-physiological attributes of drought-stressed wheat plants and can be recommended as a promising treatment to enhance wheat productivity in drought-affected regions. Additionally, the results of this study may open up a whole new area of research opportunities at the transcriptional level to further understand the mechanisms underlying how Si + ML integrates and interacts with plants under drought stress.

Influence of Thermotolerant Rhizobacteria Bacillus spp. on Biochemical Attributes and Antioxidant Status of Mustard Under High Temperature Stress

Due to global warming, increasing incidences of higher-than-normal temperatures have been observed, which adversely affect seed germination, crop growth, and productivity. Several reports are available on the effect of inoculation with rhizobacteria on plant growth and biochemical attributes; however, information on their influence on seed germination and plant stress levels is lacking. In the present study, under heat stress, we studied the effect of three thermotolerant rhizobacterial strains on mustard seed germination, seedling vigor, and plant growth. Effect of inoculation with the rhizobacterial strains on the plant stress levels, biochemical attributes and antioxidant activity was also determined. Under heat stress, inoculation with the rhizobacterial strains improved seed germination and seedling fresh weight and plumule length; while only Bacillus licheniformis SSA 61 inoculated plants showed better radicle length. There was a concomitant decrease in the plant ethylene levels in the inoculated treatments. Inoculated plants showed higher shoot fresh weight, however, Bacillus sp. MRD-17 inoculated plants only improved root growth. There was significant increase in most of the plant biochemical parameters and activities of antioxidant enzymes superoxide dismutase, catalase, and ascorbate peroxidase. Significant reduction in proline and total sugar content was noted in the inoculated treatments; while increase in the amino acid and phenolics content was observed. A further increase in the antioxidant enzyme activity was recorded in most of the inoculated treatments compared with no stress. Thus, our study indicated that thermotolerant rhizobacterial strains reduced plant stress levels; enhanced seed germination, seedling vigor, plant biomass, and thermotolerance of mustard.

Biocontrol features of Pseudomonas syringae B-1 against Botryosphaeria dothidea in apple fruit.

Apple ring rot caused by Botryosphaeria dothidea is an important disease that leads to severe quality deterioration and yield loss at pre-harvest and postharvest stages. Therefore, it is urgent to develop safe and efficient measures to control this disease. The objective of the present study was to investigate the biocontrol features of Pseudomonas syringae B-1 against B. dothidea and explore its mechanism of action utilizing in vitro and in vivo assays. The results showed that P. syringae B-1 strongly reduced the incidence of apple ring rot and lesion diameter by 41.2 and 90.2%, respectively, in comparison to the control fruit. In addition, the control efficiency of strain B-1 against B. dothidea infection depended on its concentration and the interval time. P. syringae B-1 cells showed higher inhibitory activities than its culture filtrates on the mycelial growth and spore germination of B. dothidea. Moreover, P. syringae B-1 treatment alleviated electrolyte leakage, lipid peroxidation, and H2O2 accumulation in B. dothidea-infected apple fruit by increasing antioxidant enzyme activities, including peroxidase, catalase, superoxide dismutase, and ascorbate peroxidase. We also found that strain B-1 treatment enhanced four defense-related enzyme activities and stimulated the accumulation of three disease-resistant substances including phenolics, lignin, and salicylic acid (SA) in apple fruit. In addition, strain B-1 triggered the upregulated expression of defense-related genes such as PR genes (PR1, PR5, GLU, and CHI) and two genes involved in the biosynthesis of SA (SID2 and PAD4) to promote the resistance potential in apple fruit. Hence, our results suggest that P. syringae B-1 is a promising strategy against B. dothidea, mainly through reducing oxidative damage, activating defense-related enzymes, accumulating disease-resistant substances, and triggering the expression of resistance-correlated genes in apple fruit.

Morphological, physiological and antioxidant response of Stevia rebaudiana under in vitro agar induced drought stress

In this investigation, the response of Stevia rebaudiana Bertoni was studied in different in vitro drought conditions. A method based on agar concentration in different levels (6, 8, 10, 12, 14 gl-1) was used to induce some drought stress levels. Agar concentrations can make a meaningful difference in biochemical, physiological, and antioxidant responses of the Stevia. Under the stress condition, the highest accumulation of proline content (50%) and malondialdehyde (MDA) (42%) were recorded in the highest concentration of agar. Moreover, antioxidant enzyme activities, ascorbate peroxidase (17%), catalase (53%), and peroxidase (30%) have been drastically enhanced from 8 gl-1 agar. Current results indicated that using agar as a water stress agent could be effectively exploited as an efficient method in modeling the in vitro drought stress in Stevia rebaudiana.

Molecular mechanisms of toxicity and detoxification in rice (Oryza sativa L.) exposed to polystyrene nanoplastics

Nanoplastics (NPs) are an emerging threat to higher plants in terrestrial ecosystems. However, the molecular of NP-related phytotoxicity remains unclear. In the present study, rice seedlings were exposed to polystyrene (PS, 50 nm) NPs at 0, 50, 100, and 200 mg/L under hydroponic conditions to investigate the induced physiological indices and transcriptional mechanisms. We found that 50, 100, and 200 mg/L PS significantly reduced root (53.05%, 49.61%, and 57.58%, respectively) and shoot (54.63%, 61.56%, and 62.64%, respectively) biomass as compared with the control seedlings. The activities of antioxidant enzymes, including catalase (CAT), peroxidase (POD), superoxide dismutase (SOD), and ascorbate peroxidase (APX), were significantly activated in all PS treatment groups, indicating that PS inhibited plant growth and induced oxidative stress. Transcriptome analyses showed that PS modulated the expression of the genes involved in cell detoxification, active oxygen metabolism, mitogen-activated protein kinase (MAPK), and plant hormone transduction pathways. Our study provides new insights into phytotoxicity by demonstrating the potential underlying toxicity of PS NPs in higher plants.

Capsaicin toxicity to the yeast Saccharomyces cerevisiae is not due to oxidative stress but to disruption of membrane structure

Capsaicin (CAP) is a common food constituent, conferring a pungent taste to red peppers of the genus Capsicum. It has bactericidal and fungicidal activity. The study was aimed to test the hypothesis of whether oxidative stress mediates the toxicity of CAP to the baker's yeast Saccharomyces cerevisiae as a model yeast. CAP showed good antioxidant properties (1.30 and 1.10 mol Trolox equivalents/mol in the 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonate (ABTS) radical scavenging assay and the Ferric Reducing Antioxidant Power assay, respectively). However, its autoxidation generated hydrogen peroxide. CAP inhibited the growth of S. cerevisiae at concentrations ≥100 μM. Yeast mutants deficient in superoxide dismutase 1 or catalase T were more sensitive to CAP than wild-type yeast. CAP did not augment the ROS level in yeast cells. Standard antioxidants (N-acetylcysteine and ascorbate) did not protect significantly against CAP-induced yeast growth inhibition. Thus, oxidative stress does not mediate the CAP's inhibition of yeast growth. CAP did not decrease mitochondrial membrane potential of the yeast but induced a concentration-dependent decrease in membrane fluidity. These results indicate that the disturbance of membrane properties is the apparent cause of CAP toxicity to the yeast.

Zat12 Gene Ameliorates Temperature Stress in Wheat Transgenics by Modulating the Antioxidant Defense System

The present study was undertaken with the objective to reconnoiter the role of Zat12-related biochemical activities in temperature stress tolerance in wheat transgenic lines Z-8-12 1A, Z-8-12 1B, Z-8-19, and Z-15-10, which were produced by transforming wheat-cultivar PBW 621. Zat12 transgenics (ZT) along with non-transgenic (NT) wheat cultivars (PBW 621, PBW, 550, and HD 3086) were assessed at the three-weeks seedling stage under chilling (−2 °C and −4 °C) and heat (30 °C and 32 °C) stress. Specific activities of superoxide dismutase (SOD), peroxidase (POD), ascorbate peroxidase (APX), glutathione-S-transferase (GST), glutathione reductase (GR), and antioxidants (proline and ascorbate) were profoundly increased under temperature stress in ZT related to NT. However, under −4 °C and 32 °C, a significantly higher increase was reported. In contrast, H2O2 and MDA were found to be much lower in ZT than in NT. Similarly, lesser decreases in length, fresh weight, and dry weight of seedlings were reported in ZT at 30 °C and 32 °C. RT-PCR studies revealed the enhanced expression of Zat12 in the roots of seedlings at the 5, 10, and 14 days after germination (DAG) stages in ZT under the stress conditions. Upregulation of the antioxidant defense system in ZT and their better tolerance depict an alternative for wheat cultivation under temperature stress-prone areas.

Hydroxypropyl cellulose reduces chilling injury in green bell pepper (Capsisum annuum L.) by regulating the activity and gene expression of enzymes involved in antioxidant and membrane lipid metabolism

Green bell peppers (Capsicum annuum L.) are subject to chilling harm when being stored and transported. In the current study, the effect of hydroxypropyl cellulose (HPC) on chilling injury (CI) of green peppers stored at 4 °C for 8 d and then moved to 20 °C for 3 d to simulate shelf life was examined. Results exhibited that the HPC treatment greatly reduced the CI of green pepper, decreased the degradation of chlorophyll and ascorbic acid, controlled the buildup of malondialdehyde (MDA), and decreased the level of relative conductivity, relative to untreated controls, all of which reflect a decreased level of injury. HPC increased the activities and gene expressions of antioxidant enzymes, including catalase (CAT), peroxidase (POD), superoxide dismutase (SOD), and ascorbate peroxidase (APX), resulting in lower levels of reactive oxygen species (ROS) in the stored peppers. The major enzymes involved in membrane lipid metabolism were controlled by HPC, which also regulated their gene expressions. These findings demonstrate that the use of HPC on harvested green peppers is a viable strategy for enhancing their tolerance to chilling temperatures and functions through its ability to activate the antioxidant system in green pepper and modify membrane lipid metabolism.

EVALUATION OF CALCIUM OXIDE NANOPARTICLES TO ENHANCE HEAVY METAL STRESS TOLERANCE IN PLANTS

Heavy metal contamination is a severe environmental problem affecting global food production and safety. Heavy metal stress due to its toxicity, bioaccumulation, and non-biodegradability, it become quite serious in nature. The available strategies for preventing heavy metal contamination are not frequently used because of their inefficient and time- or money-consuming properties. Recent developments in nanotechnology have been made based on ameliorative strategies which have a potential alternative to physic-chemical methods. Under heavy metal stress, the application of calcium oxide nanoparticles (CaO-NPs) significantly boosts plant biomass, anti-oxidative enzyme activities (such as catalase (CAT), ascorbate peroxidase (APX), superoxide dismutase (SOD), and glutathione reductase (GR)), and the level of non-enzymatic antioxidants (ascorbate and glutathione). Additionally, CaO-NPs enhance the gene expression linked to anti-oxidative enzymes. It can be suggested that CaO-NPs could be used as a potential chemical to reduce heavy metal uptake and toxicity in the plants grown under heavy metal contaminated soil. This review provides an overview of plant-CaO-NPs research in increasing heavy metal stress tolerance in plants.

Responses of individual and combined polystyrene and polymethyl methacrylate nanoplastics on hormonal content, fluorescence/photochemistry of chlorophylls and ROS scavenging capacity in Lemna minor under arsenic-induced oxidative stress

Nanoplastics alter the adverse impacts of hazardous contaminants such as heavy metals by changing their adsorption and accumulation. Few findings are available on the interaction between nanoplastic and heavy metals in plants. However, there is no report on the mechanisms for removing metal stress-mediated oxidative damage by the combination treatments of nanoplastics. To address this lack of information, polystyrene nanoplastic (PS, 100 mg L-1) and polymethyl methacrylate (PMMA, 100 mg L-1) were hydroponically applied to Lemna minor exposed to arsenate (As, 100 μM) for 7 days. PS or PMMA caused a reduction in the contents of N, P, K, Ca, Mg and Mn, but the improved contents were detected in the presence of PS or PMMA plus As stress. The hormone contents (auxin, gibberellic acid, cytokinin, salicylic acid and jasmonic acid) reduced by stress were re-arranged through PS or PMMA applications. Based on chlorophyll efficiency, fluorescence kinetics and performance of PSII, the impaired photosynthesis by As stress was improved via PS or PMMA applications. This alleviation did not continue under the combined form of PS and PMMA in As-applied plants. All analyzed antioxidant activity (superoxide dismutase (SOD), catalase (CAT), peroxidase (POX), ascorbate peroxidase (APX), glutathione reductase (GR), glutathione S-transferase (GST), glutathione peroxidase (GPX), monodehydroascorbate reductase (MDHAR) and dehydroascorbate reductase (DHAR)) decreased or unchanged under As, PS or PMMA. Due to the inactivation of the defense system, L. minor had high levels of hydrogen peroxide (H2O2) and thiobarbituric acid reactive substances (TBARS), showing lipid peroxidation. After As toxicity, induvial applications of PS or PMMA indicated the activated enzyme capacity (SOD, POX, GST and GPX) and upregulated AsA/DHA, GSH/GSSG and redox state of GSH, which facilitated the removal of radical accumulation. The efficiency of the antioxidant system in As + PS + PMMA-applied L. minor was not enough to remove damage induced by As stress; hereby, TBARS and H2O2 contents were similar to the As-treated group. Our findings from alone or combined application of PS and PMMA provide new information to advance the tolerance mechanism against As exposure in L. minor.