Glutathione metabolism in Urtica dioica in response to cadmium based oxidative stress

To investigate the antioxidative response of glutathione metabolism in Urtica dioica L. to a cadmium induced oxidative stress, activities of glutathione reductase (GR), glutathione-S-transferase (GST), and glutathione peroxidase (GSH-Px), content of reduced (GSH) and oxidized (GSSG) glutathione, lipid peroxidation (LPO), and also accumulation of Fe, Zn, Mn, Cu besides Cd were determined in the roots, stems, and leaves of plants exposed to 0 (control), 0.045, and 0.09 mM CdCl₂ for 58 h. Whereas the Cd content continuously increased in all organs, the Fe, Zn, Mn, and Cu content decreased in dependence on the applied Cd concentration and incubation time. The Cd treatment resulted in increased GR and GST activities in all organs, however, GSH-Px activity was dependent on Cd concentration and plant organ. The GSH/GSSG ratio maintained above the control level in the stems at both Cd concentrations. The LPO was generally close to the control values in the roots and stems but it increased in the leaves especially at 0.09 mM Cd.     

High level of reduced glutathione contributes to detoxification of lipid peroxide‐derived reactive carbonyl species in transgenic Arabidopsis overexpressing glutathione reductase under aluminum stress

Lipid peroxide‐derived reactive carbonyl species (RCS), generated downstream of reactive oxygen species (ROS), are critical damage‐inducing species in plant aluminum (Al) toxicity. In mammals, RCS are scavenged primarily by glutathione (reduced form of glutathione, GSH), but in plant Al stress, contribution of GSH to RCS detoxification has not been evaluated. In this study, Arabidopsis plants overexpressing the gene AtGR1 (accession code At3g24170), encoding glutathione reductase (GR), were generated, and their performance under Al stress was examined. These transgenic plants (GR‐OE plants) showed higher GSH levels and GSH/GSSG (oxidized form of GSH) ratio, and an improved Al tolerance as they suffered less inhibition of root growth than wild‐type under Al stress. Exogenous application of 4‐hydroxy‐2‐nonenal, an RCS responsible for Al toxicity in roots, markedly inhibited root growth in wild‐type plants. GR‐OE plants suffered significantly smaller inhibition, indicating that the enhanced GSH level increased the capacity of RCS detoxification. The generation of H₂O₂ due to Al stress in GR‐OE plants was lower by 26% than in wild‐type. Levels of various RCS, such as malondialdehyde, butyraldehyde, phenylacetaldehyde, (E)‐2‐heptenal and n‐octanal, were suppressed by more than 50%. These results indicate that high levels of GSH and GSH/GSSG ratio by GR overexpression contributed to the suppression of not only ROS, but also RCS. Thus, the maintenance of GSH level by overexpressing GR reinforces dual detoxification functions in plants and is an efficient approach to enhance Al tolerance.     

Brassica napus subjected to copper excess: Phospholipases C and D and glutathione system in signalling

Brassica napus plants were subjected to an oxidative stress by incubating them with 100 μM CuSO₄ for different times. The early response to copper stress was evaluated studying changes at both root and leaf level in the putative lipid and antioxidative signals diacylglicerol (DAG), phosphatidic acid (PA) and glutathione, in order to achieve elucidation on how these two kind of signals are related to each other. Activation of phospholipases C (PLC) and D (PLD) was studied in roots and leaves whereas increases in the levels of total and reduced glutathione (GSH) and changes in its redox status were evaluated in roots, leaves and chloroplast stroma. PLC and PLD were measured by studying the production of DAG, PA and phosphatidylbutanol (PtdButOH). PA, PtdButOH as well as DAG increased in roots already after 1 min of the treatment whereas in leaves, where no translocation of the metal occurred, any increase in PA and DAG was observed and no PtdButOH was formed. Roots were affected by oxidative stress showing decreases in glutathione reductase (GR), in total glutathione (GSH + GSSG) and GSH, and increases in oxidised glutathione (GSSG). In leaves, GR was induced during the whole stress period and both GSH + GSSG and GSH showed a peak at 5 min of the treatment. In the stroma, the maximum presence in GSH + GSSG and GSH occurred with a time shift of 25 min compared with total leaf extract.     

Effects of a root-colonized dark septate endophyte on the glutathione metabolism in maize plants under cadmium stress

A high Cd-tolerant dark septate endophyte (DSE), Exophiala pisciphila, was inoculated into maize (Zea mays L.) roots under Cd stress. The Cd content, enzymes activity and thiol compound content relevant to glutathione (GSH) metabolism in maize leaves were analyzed. The Cd content in maize shoots increased with increasing Cd stress, but the DSE significantly reduced the Cd content at the 40?mg/kg Cd treatment. Cd stress increased the enzyme activity of glutathione reductase (GR), glutathione S-transferase (GST) and glutathione peroxidase (GSH-Px) as well as the thiol compound contents of sulfur, thiols (-SH) and oxidized glutathione (GSSG). The content of reduced GSH and the GSH/GSSG ratio reached a peak at the 5?mg/kg Cd treatment but then decreased with increasing Cd stress. Furthermore, the DSE significantly enhanced the GR and GSH-Px activity and increased the contents of -SH and GSH under low Cd stress (5 and 10?mg/kg), but decreased the γ-glutamylcysteine synthetase and GST activity under high Cd stress (20 and 40?mg/kg). Highly positive correlations between the Cd content with enzymes activity and enzymes activity with thiol compound content were observed. Results indicated that DSE played a role in activating GSH metabolism in maize leaves under Cd stress.     

Involvement of glutathione metabolism in Eichhornia crassipes tolerance to arsenic

• Aquatic macrophytes are potentially useful for phytoremediation programmes in environments contaminated by arsenic (As). Biochemical and physiological modification analyses in different plant parts are important to understand As tolerance mechanisms.
• The objective was to evaluate glutathione metabolism in leaves and roots of Eichhornia crassipes (Mart.) Solms treated to As. Specimens of E. crassipes were cultured for 3 days in Clark's nutrient solution containing 7 μm As. The enzymes ATP sulphurylase (ATPS), glutathione reductase (GR), glutathione peroxidase (GSH‐Px), glutathione sulphotransferase (GST) and γ‐glutamylcysteine synthetase (γ‐ECS) activity, glutathione content, total protein and non‐protein thiols were evaluated.
• The ATPS activity increased in roots. GR activity in leaves and GSH‐Px in roots were lower. GST activity was higher in roots and lower in leaves, and γ‐ECS activity was higher in leaves. Glutathione levels were lower, total thiol levels were higher and non‐protein levels did not change in E. crassipes leaves and roots. Exposure to As increased enzyme activity involved with sulphur metabolism, such as ATPS. Higher GR activity and lower GSH‐Px indicate increased glutathione conjugation to As due to increased GSH availability. The higher GST activity indicates its participation in As detoxification and accumulation through As GSH conjugation. Changes in glutathione and thiol levels suggest high phytochelatin synthesis.
• In conclusion, the increments in ATPS, GR, GST and γ‐ECS activity indicate that these enzymes are involved in GSH metabolism and are part of the E. crassipes As detoxification mechanism.

     

Exogenous Selenium Pretreatment Protects Rapeseed Seedlings from Cadmium-Induced Oxidative Stress by Upregulating Antioxidant Defense and Methylglyoxal Detoxification Systems

The protective effect of selenium (Se) on antioxidant defense and methylglyoxal (MG) detoxification systems was investigated in leaves of rapeseed (Brassica napus cv. BINA sharisha 3) seedlings under cadmium (Cd)-induced oxidative stress. Two sets of 11-day-old seedlings were pretreated with both 50 and 100???M Se (Na₂SeO₄, sodium selenate) for 24?h. Two concentrations of CdCl₂ (0.5 and 1.0?mM) were imposed separately or on the Se-pretreated seedlings, which were grown for another 48?h. Cadmium stress at any levels resulted in the substantial increase in malondialdehyde and H₂O₂ levels. The ascorbate (AsA) content of the seedlings decreased significantly upon exposure to Cd stress. The amount of reduced glutathione (GSH) increased only at 0.5?mM CdCl₂, while glutathione disulfide (GSSG) increased at any level of Cd, with concomitant decrease in GSH/GSSG ratio. The activities of ascorbate peroxidase (APX) and glutathione S-transferase (GST) increased significantly with increased concentration of Cd (both at 0.5 and 1.0?mM CdCl₂), while the activities of glutathione reductase (GR) and glutathione peroxidase (GPX) increased only at moderate stress (0.5?mM CdCl₂) and then decreased at 1.0?mM severe stress (1.0?mM CdCl₂). Monodehydroascorbate reductase (MDHAR), dehydroascorbate reductase (DHAR), catalase (CAT), glyoxalase I (Gly I), and glyoxalase II (Gly II) activities decreased upon exposure to any levels of Cd. Selenium pretreatment had little effect on the nonenzymatic and enzymatic components of seedlings grown under normal conditions; i.e., they slightly increased the GSH content and the activities of APX, GR, GST, and GPX. On the other hand, Se pretreatment of seedlings under Cd-induced stress showed a synergistic effect; it increased the AsA and GSH contents, the GSH/GSSG ratio, and the activities of APX, MDHAR, DHAR, GR, GPX, CAT, Gly I, and Gly II which ultimately reduced the MDA and H₂O₂ levels. However, in most cases, pretreatment with 50???M Se showed better results compared to pretreatment with 100???M Se. The results indicate that the exogenous application of Se at low concentrations increases the tolerance of plants to Cd-induced oxidative damage by enhancing their antioxidant defense and MG detoxification systems.     

Calcium and L-histidine effects on ascorbate-glutathione cycle components under nickel-induced oxidative stress in tomato plants

The effects of NiSO₄, calcium, and L-histidine (His) on the components of ascorbate-glutathione cycle, antioxidant enzymes and lipid peroxidation in a tomato cultivar Early Urbana Y was investigated. The activities of enzymes including catalase (CAT), guaiacol peroxidase (GPX), ascorbate peroxidase (APX), superoxide dismutase (SOD), glutathione reductase (GR), lipoxygenase (LOX), and phenylalanine ammonia lyase (PAL) were measured. In addition, the content of H₂O₂, ascorbate (ASC), dehydroascorbate (DHA), reduced glutathione (GSH), chlorophyll (Chl) a+b, carotenoids, proteins, malondialdehyde (MDA), membrane aldehydes, and electrolyte leakage (EL) were determined. Results suggest that the excess of Ni increased the content of H₂O₂, MDA, membrane aldehydes and proteins in roots as well as GPX, LOX, APX activities, and EL in leaves, whereas Ca and His ameliorated these effects. Moreover, decreasing leaf GSH and DHA content and GR activity were observed under the Ni stress, but these parameters were raised by Ca plus His treatment. However, no improvement in leaf protein, ASC, root GSH content, and activities of PAL and CAT were observed by using Ca or His under Ni stress.     

Selenium Pretreatment Upregulates the Antioxidant Defense and Methylglyoxal Detoxification System and Confers Enhanced Tolerance to Drought Stress in Rapeseed Seedlings

In order to observe the possible regulatory role of selenium (Se) in relation to the changes in ascorbate (AsA) glutathione (GSH) levels and to the activities of antioxidant and glyoxalase pathway enzymes, rapeseed (Brassica napus) seedlings were grown in Petri dishes. A set of 10-day-old seedlings was pretreated with 25 μM Se (Sodium selenate) for 48 h. Two levels of drought stress (10% and 20% PEG) were imposed separately as well as on Se-pretreated seedlings, which were grown for another 48 h. Drought stress, at any level, caused a significant increase in GSH and glutathione disulfide (GSSG) content; however, the AsA content increased only under mild stress. The activity of ascorbate peroxidase (APX) was not affected by drought stress. The monodehydroascorbate reductase (MDHAR) and glutathione reductase (GR) activity increased only under mild stress (10% PEG). The activity of dehydroascorbate reductase (DHAR), glutathione S-transferase (GST), glutathione peroxidase (GPX), and glyoxalase I (Gly I) activity significantly increased under any level of drought stress, while catalase (CAT) and glyoxalase II (Gly II) activity decreased. A sharp increase in hydrogen peroxide (H₂O₂) and lipid peroxidation (MDA content) was induced by drought stress. On the other hand, Se-pretreated seedlings exposed to drought stress showed a rise in AsA and GSH content, maintained a high GSH/GSSG ratio, and evidenced increased activities of APX, DHAR, MDHAR, GR, GST, GPX, CAT, Gly I, and Gly II as compared with the drought-stressed plants without Se. These seedlings showed a concomitant decrease in GSSG content, H₂O₂, and the level of lipid peroxidation. The results indicate that the exogenous application of Se increased the tolerance of the plants to drought-induced oxidative damage by enhancing their antioxidant defense and methylglyoxal detoxification systems.     

Parameters related to oxygen free radicals in erythrocytes,plasma and epidermis of the hairless rat

The following parameters related to oxygen free radicals (OFR) were determined in erythrocytes and the epidermis of hairless rats: catalase (CAT), glutathione peroxidase (GPx), glutathione reductase (GR), reduced (GSH) and oxidized (GSSG) glutathione, glutathione S-transferase (GST), superoxide dismutase (SOD) and thiobarbituric acid reactive substances (TBARS). GSH, GSSG and TBARS were also analyzed in plasma. In erythrocytes, the Pearson correlation coefficients (r) were significant (p < 0.001) between glutathione and other parameters as follows: GSH correlated negatively with GSSG (r = -0.665) and TBARS (r = -0.669); GSSG correlated positively with SOD (r = 0.709) and TBARS (r = 0.752). Plasma GSSG correlated negatively with erythrocytic thermostable GST activity (r = -0.608; p=0.001) and with erythrocytic total GST activity (r = -0.677; p < 0.001). In epidermis (p < 0.001 in all cases), GSH content correlated with GSSG (r = 0.682) and with GPx (r = 0.663); GSSG correlated with GPx (r = 0.731) and with GR (r = 0.794). By multiple linear regression analysis some predictor variables (R(2)) were found: in erythrocytes, thermostable GST was predicted by total GST activity and GSSG, GSSG content was predicted by GSH and by the GSH/GSSG ratio and GPx activity was predicted by GST, CAT and SOD activities; in epidermis, GSSG was predicted by GR and SOD activities and GR was predicted by GSSG, TBARS and GPx. It is concluded that the hairless rat is a good model for studying OFR-related parameters simultaneously in blood and skin, and that it may provide valuable information about other animals under oxidative stress.     

Preliminary studies on the involvement of glutathione metabolism and redox status against zinc toxicity in radish seedlings by 28-Homobrassinolide

The effect of exogenous application of 28-Homobrassinolide (HBR) on radish (Raphanus sativus L.) seedlings under zinc (Zn²⁺) stress on glutathione (GSH) production, consumption and changes in redox status was investigated. Zinc toxicity resulted in oxidative burst as evidenced by increased accumulation of hydrogen peroxide (H₂O₂) and malondialdehyde (MDA) content. These stress indices were significantly decreased by HBR supplementation. Under Zn²⁺ stress, GSH pool was decreased, while the contribution of oxidized glutathione (GSSG) to total GSH increased (GSSH/GSH ratio), this translated into significant reduction of GSH redox homeostasis. In addition, an increase of phytochelatins (PCs) was observed. In radish seedlings under Zn²⁺ stress, the activities of gamma-glutamylcysteine synthetase (γ-ECS), glutathione synthetase (GS), glutathione peroxidase (GPX), glutathione-S-transferase (GST) and cysteine (Cys) levels increased but the activity of glutathione reductase (GR) decreased. However, application of HBR increased the GSH pool and maintained their redox ratio by increasing the enzyme activities of GSH biosynthesis (γ-ECS and GS) and GSH metabolism (GR, GPX and GST). The results of present study are novel in being the first to demonstrate that exogenous application of HBR modulates the GSH synthesis, metabolism and redox homeostasis to confer resistance against Zn²⁺ induced oxidative stress.     

Selenium-Induced Up-Regulation of the Antioxidant Defense and Methylglyoxal Detoxification System Reduces Salinity-Induced Damage in Rapeseed Seedlings

The present study investigates the regulatory role of exogenous selenium (Se) in the antioxidant defense and methylglyoxal (MG) detoxification systems in rapeseed seedlings exposed to salt stress. Twelve-day-old seedlings, grown in Petri dishes, were supplemented with selenium (25 μM Na₂SeO₄) and salt (100 and 200 mM NaCl) separately and in combination, and further grown for 48 h. The ascorbate (AsA) content of the seedlings decreased significantly with increased salt stress. The amount of reduced glutathione (GSH) and glutathione disulfide (GSSG) increased with an increase in the level of salt stress, while the GSH/GSSG ratio decreased. In addition, the ascorbate peroxidase (APX) and glutathione S-transferase (GST) activity increased significantly with increased salt concentration (both at 100 and 200 mM NaCl), while glutathione peroxidase (GPX) activity increased only at moderate salt stress (100 mM NaCl). Glutathione reductase (GR) activity remained unchanged at 100 mM NaCl, while it was decreased under severe (200 mM NaCl) salt stress. Monodehydroascorbate reductase (MDHAR), dehydroascorbate reductase (DHAR), catalase (CAT), glyoxalase I (Gly I), and glyoxalase II (Gly II) activities decreased upon the imposition of salt stress, whereas a sharp decrease of these activities was observed under severe salt stress (200 mM NaCl). Concomitant increases in the levels of H₂O₂ and lipid peroxidation (MDA) were also measured. Exogenous Se treatment alone had little effect on the non-enzymatic and enzymatic components. However, further investigation revealed that Se treatment had a synergistic effect: in salt-stressed seedlings, it increased the AsA and GSH contents; GSH/GSSG ratio; and the activities of APX, MDHAR, DHAR, GR, GST, GPX, CAT, Gly I, and Gly II. As a result, addition of Se in salt-stressed seedlings led to a reduction in the levels of H₂O₂ and MDA as compared to salt stress alone. These results suggest that the exogenous application of Se rendered the plants more tolerant to salt stress-induced oxidative damage by enhancing their antioxidant defense and MG detoxification systems.     

Oxidative Damage Induced by Arsenic in Mice or Rats: A Systematic Review and Meta-Analysis

In this meta-analysis, studies reporting arsenic-induced oxidative damage in mouse models were systematically evaluated to provide a scientific understanding of oxidative stress mechanisms associated with arsenic poisoning. Fifty-eight relevant peer-reviewed publications were identified through exhaustive database searching. Oxidative stress indexes assessed included superoxide dismutase (SOD), catalase (CAT), glutathione (GSH), glutathione peroxidase (GPx), glutathione-s-transferase (GST), glutathione reductase (GR), oxidized glutathione (GSSG), malondialdehyde (MDA), and reactive oxygen species (ROS). Our meta-analysis showed that arsenic exposure generally suppressed measured levels of the antioxidants, SOD, CAT, GSH, GPx, GST, and GR, but increased levels of the oxidants, GSSG, MDA, and ROS. Arsenic valence was important and GR and MDA levels increased to a significantly (P < 0.05) greater extent upon exposure to As³⁺ than to As⁵⁺. Other factors that contributed to a greater overall oxidative effect from arsenic exposure included intervention time, intervention method, dosage, age of animals, and the sample source from which the indexes were estimated. Our meta-analysis effectively summarized a wide range of studies and detected a positive relationship between arsenic exposure and oxidative damage. These data provide a scientific basis for the prevention and treatment of arsenic poisoning.     

外源一氧化氮供体对NaCl胁迫下多裂骆驼蓬幼苗叶片ASA-GSH循环的影响

研究了外源一氧化氮(NO)供体硝普钠(SNP)对NaCl胁迫下多裂骆驼蓬幼苗抗坏血酸(ASA)-谷胱甘肽(GSH)循环抗氧化系统及H2O2和丙二醛(MDA)含量的影响。结果表明,0.15mmol.L-1SNP能提高300mmol.L-1NaCl胁迫下多裂骆驼蓬幼苗叶片抗坏血酸过氧化物酶(APX)、谷胱甘肽还原酶(GR)和谷胱甘肽转硫酶(GST)活性,增加还原型抗坏血酸(ASA)和谷胱甘肽(GSH)含量,降低脱氢抗坏血酸(DHA)和氧化型谷胱甘肽(GSSG)含量,提高ASA/DHA、GSH/GSSG比率,降低H2O2和MDA水平,对单脱氢抗坏血酸还原酶(MDAR)和脱氢抗坏血酸还原酶(DHAR)活性无显著影响。NO信号转导途径关键酶鸟苷酸环化酶(GC)抑制剂亚甲基蓝(MB)逆转了SNP对盐胁迫下APX、GR、GST活性和ASA、GSH、DHA,H2O2、MDA含量及ASA/DHA、GSH/GSSG比率的调节效应。由此表明,NO可能通过GC介导的cGMP信号转导参与ASA-GSH循环活性氧清除系统的调节,从而缓解盐胁迫诱导的氧化伤害。     

即时浸酸显著降低滞育家蚕卵的还原型与氧化型谷胱甘肽比值

即时浸酸在阻止家蚕Bombyx mori卵滞育发动的同时, 显著提高了家蚕卵H₂O₂含量。还原型谷胱甘肽（reduced glutathione, GSH）与氧化型谷胱甘肽（oxidized glutathione, GSSG）的比值是一种氧化胁迫状态的动态指标。为了调查即时浸酸是否造成滞育家蚕卵氧化胁迫, 本研究利用分光光度法分别测定了滞育家蚕卵和5 min即时浸酸滞育家蚕卵中GSH和GSSG含量以及谷胱甘肽转移酶（glutathione-S-transferase, GST）活性。结果表明: 处理后24 h, 即时浸酸处理家蚕卵的总谷胱甘肽（GSH+2GSSG）含量、 GSH含量、 GSSG含量、 GSH/GSSG比值和GST活性分别相当于同期滞育家蚕卵的204%, 78%, 550%, 14%和97%。据此推测, 即时浸酸在阻止滞育发动的同时, 可能通过促进GSH氧化为GSSG, 而显著降低了GSH/GSSG比值, 使家蚕卵处于过氧化状态。     

Nitric oxide modulates antioxidant defense and the methylglyoxal detoxification system and reduces salinity-induced damage of wheat seedlings

The present study investigates the possible regulatory role of exogenous nitric oxide (NO) in antioxidant defense and methylglyoxal (MG) detoxification systems of wheat seedlings exposed to salt stress (150 and 300 mM NaCl, 4 days). Seedlings were pre-treated for 24 h with 1 mM sodium nitroprusside, a NO donor, and then subjected to salt stress. The ascorbate (AsA) content decreased significantly with increased salt stress. The amount of reduced glutathione (GSH) and glutathione disulfide (GSSG) and the GSH/GSSG ratio increased with an increase in the level of salt stress. The glutathione S-transferase (GST) activity increased significantly with severe salt stress (300 mM). The ascorbate peroxidase (APX), monodehydroascorbate reductase (MDHAR), dehydroascorbate reductase (DHAR), catalase (CAT) and glutathione peroxidase (GPX) activities did not show significant changes in response to salt stress. The glutathione reductase (GR), glyoxalase I (Gly I), and glyoxalase II (Gly II) activities decreased upon the imposition of salt stress, especially at 300 mM NaCl, with a concomitant increase in the H₂O₂ and lipid peroxidation levels. Exogenous NO pre-treatment of the seedlings had little influence on the non-enzymatic and enzymatic components compared to the seedlings of the untreated control. Further investigation revealed that NO pre-treatment had a synergistic effect; that is, the pre-treatment increased the AsA and GSH content and the GSH/GSSG ratio, as well as the activities of MDHAR, DHAR, GR, GST, GPX, Gly I, and Gly II in most of the seedlings subjected to salt stress. These results suggest that the exogenous application of NO rendered the plants more tolerant to salinity-induced oxidative damage by enhancing their antioxidant defense and MG detoxification systems.     

Antioxidative responses and proline level in leaves and roots of pea plants subjected to nickel stress

The activities of superoxide dismutase (SOD), ascorbate peroxidase (APX), catalase (CAT), glutathione S-transferase (GST) as well as proline content were studied in leaves and roots of 14 day-old pea plants treated with NiSO₄ (10, 100, 200 μm) for 1, 3, 6 and 9 days. Exposure of pea plants to nickel (Ni) resulted in the decrease in CuZnSOD as well as total SOD activities in both leaves and roots. The activity of APX in leaves of plants treated with 100 and 200 μm Ni increased following the 3rd day after metal application, while in roots at the end of the experiment the activity of this enzyme was significantly reduced. In both organs CAT activity generally did not change in response to Ni treatment. The activity of GST in plants exposed to high concentrations of Ni increased, more markedly in roots. In both leaves and roots after Ni application accumulation of free proline was observed, but in the case of leaves concentration of this amino acid increased earlier and to a greater extent than in roots. The results indicate that stimulation of GST activity and accumulation of proline in the tissues rather than antioxidative enzymes are involved in response of pea plants to Ni stress.     

Sea fennel (<Emphasis Type="Italic">Crithmum maritimum</Emphasis> L.) under salinity conditions: a comparison of leaf and root antioxidant responses

The present study was carried out to compare the effect of NaCl on growth, cell membrane damage, and antioxidant defences in the halophyte Crithmum maritimum L. (sea fennel). Physiological and biochemical changes were investigated under control (0 mM NaCl) and saline conditions (100 and 300 mM NaCl). Biomass and growth of roots were more sensitive to NaCl than leaves. Roots were distinguished from leaves by increased electrolyte leakage and high malondialdehyde (MDA) concentration. Superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (APX) activities, ascorbic acid (AA) and glutathione (GSH) concentrations were lower in the roots than in the leaves of control plants. The different activity patterns of antioxidant enzymes in response to 100 and 300 mM NaCl indicated that leaves and roots reacted differently to salt stress. Leaf CAT, APX and glutathione reductase (GR) activities were lowest at 300 mM NaCl, but they were unaffected by 100 mM NaCl. Only SOD activity was reduced in the latter treatment. Root SOD activity was significantly decreased in response to 300 mM NaCl and root APX activity was significantly higher in plants treated with 100 and 300 mM compared to the controls. The other activities in roots were insensitive to salt. The concentration of AA decreased in leaves at 100 and 300 mM NaCl, and in roots at 300 mM NaCl, when compared to control plants. The concentrations of GSH in NaCl-treated leaves and roots were not significantly different from the controls. In both organs, AA and GSH were predominating in the total pool in ascorbic acid and glutathione, under control or saline conditions.     

Cadmium-induced oxidative damage and antioxidative defense mechanisms in <Emphasis Type="Italic">Vigna mungo</Emphasis> L.

Cadmium (Cd)-induced oxidative stress and antioxidant defense mechanisms were analyzed in roots and leaves of Vigna mungo L. Seeds were germinated in perlite-vermiculite and irrigated with Hoagland nutrient solution. At day 6, seedlings were exposed to 40 μM Cd under semi-hydroponic conditions for a period of 12 days. Growth anomalies and abnormal chromatin condensation were observed in Cd-treated plants, in comparison with control ones. Cd accumulation was observed in roots of treated plants. The analyses of antioxidative defense and oxidative parameters in roots, stems and leaves showed different tissue-specific responses. Superoxide dismutase (SOD) and guaiacol peroxidase (GPx) activities and the level of lipid peroxidation (MDA content) decreased in roots. However, they increased in leaves. Catalase activity and chlorophyll content, on the other hand, decreased over exposure to Cd stress. Total glutathione, non-protein thiols, reduced glutathione (GSH) and phytochelatins increased significantly, while oxidized glutathione (GSSG) decreased, as compared with control plants. The present data suggest that the presence of Cd in soil and water can cause oxidative damage that may be detrimental for optimum production of nutritional mung.     

Antioxidative responses to different altitudes in leaves of alpine plant Polygonum viviparum in summer

Mountain environmental stresses result in increased formation of hydrogen peroxide (H₂O₂) and accumulation of malondialdehyde (MDA) in leaves of Polygonum viviparum. The activities of several antioxidative system enzymes such as superoxide dismutase (SOD, EC 1.15.1.1), catalase (CAT, EC 1.11.1.6), peroxidase (POD, EC 1.11.1.7), glutathione reductase (GR, EC 1.6.4.2), dehydroascorbate reductase (DHAR, EC 1.8.5.1) and the contents of several non-enzymatic antioxidants such as reduced form of ascorbate (ASC), dehydroascorbate (DHA), reduced glutathione (GSH), and oxidized glutathione (GSSG) were investigated in leaves of P. viviparum, which were collected from three altitudes (2,200, 3,200, and 3,900 m) of Tianshan Mountain in China. The activities of these four antioxidative enzymes were accompanied by increases of H₂O₂ levels from 2,200 to 3,200 m. However, the activities of CAT and POD were decreased, whereas the activities of SOD and GR continually increased at 3,900 m. Analyses of isoforms of SOD, CAT, POD, and GR showed that the leaves of P. viviparum exposed different altitude conditions are capable of differentially altering the intensity. Additionally, two new isoforms of SOD were detected at 3900 m. A continual increase in the ASC, ASC to DHA ratio, GSH and GSH/[GSH + GSSG] ratio, and the activity of DHAR were observed in leaves of P. viviparum with the elevation of altitude. These results suggest that the higher contents of ASC, GSH as well as an increase in reduced redox state may be essential to antioxidation processes in the leaves of P. viviparum, whereas antioxidant enzymes system is a cofactor in the processes.     

Exogenous sodium nitroprusside and glutathione alleviate copper toxicity by reducing copper uptake and oxidative damage in rice (Oryza sativa L.) seedlings

Nitric oxide (NO) and glutathione (GSH) regulate a variety of physiological processes and stress responses; however, their involvement in mitigating Cu toxicity in plants has not been extensively studied. This study investigated the interactive effect of exogenous sodium nitroprusside (SNP) and GSH on Cu homeostasis and Cu-induced oxidative damage in rice seedlings. Hydroponically grown 12-day-old seedlings were subjected to 100 μM CuSO₄ alone and in combination with 200 μM SNP (an NO donor) and 200 μM GSH. Cu exposure for 48 h resulted in toxicity symptoms such as stunted growth, chlorosis, and rolling in leaves. Cu toxicity was also manifested by a sharp increase in lipoxygenase (LOX) activity, lipid peroxidation (MDA), hydrogen peroxide (H₂O₂), proline (Pro) content, and rapid reductions in biomass, chlorophyll (Chl), and relative water content (RWC). Cu-caused oxidative stress was evident by overaccumulation of reactive oxygen species (ROS; superoxide (O₂ ^?–) and H₂O₂). Ascorbate (AsA) content decreased while GSH and phytochelatin (PC) content increased significantly in Cu-stressed seedlings. Exogenous SNP, GSH, or SNP?+?GSH decreased toxicity symptoms and diminished a Cu-induced increase in LOX activity, O₂ ^?–, H₂O₂, MDA, and Pro content. They also counteracted a Cu-induced increase in superoxide dismutase (SOD), ascorbate peroxidase (APX), glutathione reductase (GR), monodehydroascorbate reductase (MDHAR), and glyoxalase I and glyoxalase II activities, which paralleled changes in ROS and MDA levels. These seedlings also showed a significant increase in catalase (CAT), glutathione peroxidase (GPX), dehydroascorbate reductase (DHAR), glutathione S-transferase (GST) activities, and AsA and PC content compared with the seedlings stressed with Cu alone. Cu analysis revealed that SNP and GSH restricted the accumulation of Cu in the roots and leaves of Cu-stressed seedlings. Our results suggest that Cu exposure provoked an oxidative burden while reduced Cu uptake and modulating the antioxidant defense and glyoxalase systems by adding SNP and GSH play an important role in alleviating Cu toxicity. Furthermore, the protective action of GSH and SNP?+?GSH was more efficient than SNP alone.