Cobalt stress affects nitrogen metabolism,photosynthesis and antioxidant system in chickpea (Cicer arietinum L.)

Abstract

Plants of chickpea were exposed to varied levels of cobalt (Co) and sampled at the 60-day stage. Cobalt at concentration <100 µM significantly increased the number of nodules, their dry mass, leghemoglobin concentration and the activity of nitrogenase. Similarly, the activities of glutamate dehydrogenase, glutamine synthetase and glutamate synthase also exhibited an increase in the presence of Co <100 µM, in nodules and leaves, respectively. The various photosynthetic attributes in leaves and the activity of antioxidative enzymes both in nodules and leaves were inhibited by Co in a concentration-dependent manner. However, the lipid peroxidation and the content of proline exhibited a significant increase in response to Co and were at a maximum in the plants exposed to 250 µM concentration of cobalt. Since most of the parameters showed a significant increase in response to 50 µM cobalt, this concentration may be regarded as a threshold concentration.     

Ethylene-promoted ascorbate peroxidase activity protects plants against hydrogen peroxide, ozone and paraquat

Abstract. In experiments where mung beans ( Vigna radiata L.) and peas ( Pisum sativum L.) have been pre-exposed to ethylene and afterwards treated with ozone, it has been shown that such ethylenepretreated plants may become more resistant to ozone. Further experiments with hydrogen peroxide (H₂O₂) and the herbicide paraquat suggest that this increased resistance against ozone depends on the stimulation of ascorbate peroxidase activity which provides cells with increased resistance against the formation of H₂O₂ which is also formed when plants are fumigated with ozone. These results explain why increased production of ethylene can be observed in plants exposed with ozone or other oxidative stress and clearly demonstrate that in plants, as well as animals, peroxidases protect cells against harmful concentrations of hydroperoxides.     

Cadmium-induced changes in antioxidative systems,hydrogen peroxide content,and lipid peroxidation in<Emphasis Type="Italic">Arabidopsis thaliana</Emphasis>

To study the relationship between cadmium (Cd)-induced phytotoxicity and oxidative stress, we grew Cd-sensitive wild-type (WT) and Cd-resistant type (RT) seedlings ofArabidopsis thaliana on MS media containing up to 500 μM CdCl₂. The resistant seedlings showed higher biomasses and lower hydrogen peroxide and lipid peroxidation levels, the latter expressed in terms of malondialdehyde (MDA) production. These results indicate that RT plants experience lower oxidative stress when exposed to Cd. Furthermore, compared with the WT, RT seedlings have significantly higher activities of superoxide dismutase (SOD) and enzymes related to hydrogen peroxide removal, e.g., guaiacol peroxidase (GPX), ascorbate peroxidase (APX), and glutathione reductase (GR). These differential responses suggest that such phytotoxicity could be induced by oxidative stress, and that lower accumulations of hydrogen peroxide confer Cd tolerance in seedlings.     

Combined effects of water stress and high temperature on photosynthesis, nitrogen metabolism and lipid peroxidation of a perennial grass Leymus chinensis

Drought and high-temperature stresses have been extensively studied; however, little is known about their combined impact on plants. In the present study, we determined the photosynthetic gas exchange, chlorophyll fluorescence, nitrogen level, and lipid peroxidation of the leaves of a perennial grass (Leymus chinensis (Trin.) Tzvel.) subjected to three constant temperatures (23, 29 and 32°C), and five soil-moisture levels (75–80%, 60–65%, 50–55%, 35–40% and 25–30% of field capacity, respectively). High temperature significantly decreased plant biomass, leaf green area, leaf water potential, photosynthetic rate (A), maximal efficiency of PSII photochemistry (F _v/F _m), actual PSII efficiency (Φ_PSII), the activities of nitrate reductase (NR; EC 1.6.6.1) and glutamine synthetase (GS; EC 6.3.1.2), but markedly increased the ratio of leaf area to leaf weight (SLA), endopeptidase (EP; EC 3.4.24.11) activity, and malondialdehyde (MDA) content, especially under severe water stress conditions. The A and F _v/F _m were significantly and positively correlated with leaf-soluble protein content, and the activities of NR and GS. However, both photosynthesis parameters were significantly and negatively correlated with EP activity and MDA content (P < 0.05). It is suggested that high temperature, combined with severe soil drought, might reduce the function of PSII, weaken nitrogen anabolism, strengthen protein catabolism, and provoke lipid peroxidation. The results also indicate that severe water stress might exacerbate the adverse effects of high temperature, and their combination might reduce the plant productivity and distribution range of L. chinensis in the future.     

干旱胁迫对坡柳等抗旱树种幼苗膜脂过氧化及保护酶活性的影响

以金沙江干热河谷主要树种坡柳、银合欢、山毛豆实生幼苗为材料,通过盆栽苗自然干旱胁迫,同时以浇水处理为对照,研究了干旱胁迫对坡柳、银合欢、山毛豆3个树种丙二醛含量、膜相对透性及保护酶活性的影响。结果表明,干旱胁迫下3个树种幼苗的细胞膜透性、MDA及SOD, POD酶活性都发生了变化,只是变化的幅度和进程不同。干旱胁迫对银合欢膜系统损伤生成的主要降解产物不是MDA;山毛豆清除活性氧毒害作用主要不是通过SOD和POD的作用;通过叶片相对保水力测定及膜透性、MDA相对含量、酶活性变化情况的分析,3个树种中坡柳耐旱性最强,其次为银合欢,山毛豆居后。     

In situ and in vitro senescence induced by KCl stress: nutritional imbalance, lipid peroxidation and antioxidant metabolism

Sunflower (Helianthus annuus L. cv. SH222) plants and calli were exposed to KCl stress for three weeks. Calli were more tolerant to KCl than plants. KCl stress decreased NO(-)(3), Mn, Fe and B levels in whole plants and P, Ca and Mg in shoots. NO(-)(3), P, Ca, Mg, Mn, and B levels decreased in 100 mM-stressed calli. Chlorophyll content, F:(m) and (F:(m)-F:(0))/F:(m) ratio decreased in stressed leaves, while F:(0) increased only in leaves exposed to severe stress (100 and 150 mM). Membrane permeability and lipid peroxidation increased in plants under all stress conditions and in 100 and 150 mM stressed calli, but remained unchanged in 25 mM stressed calli. Salt stress also induced changes relating to antioxidant enzymes: plants under all stress conditions showed a decrease in catalase, peroxidase and SOD activities. Calli under moderate stress (25 mM KCl) showed an increase of catalase, peroxidase and SOD activities, but the activities of peroxidase and SOD decreased when calli were exposed to higher KCl concentrations. The decrease of antioxidant enzyme activities is in tune with lipid peroxidation and membrane permeability increases. On the other hand, calli adapted for 6 months to 100 mM KCl showed an increase of these enzyme activities compared to unstressed calli, while MDA production and membrane permeability were not significantly affected.     

Study on lipid peroxidation potential in different tissues induced by ascorbate-Fe2+: Possible factors involved in their differential susceptibility

Susceptibility of four major rat tissues to oxidative damage in terms of lipid peroxidation induced by in vitro by ascorbate-Fe²⁺ in homogenates and mitochondria has been examined. Lipid peroxidation, as assessed by thiobarbituric acid reactive substances (TBARS) and conjugated dienes was maximum in brain followed by liver, kidney and heart. However, the time course of lipid peroxidation showed different patterns in tissues examined. The higher susceptibilities of brain and liver can be explained by substrate availability and to a lesser extent the level of antioxidants. The differences observed in the tissues studied may reflect their susceptibility to degenerative diseases and xenobiotic toxicity which are considered as a result of oxidative damage to membranes.     

Soybean MAPK, GMK1 Is dually regulated by phosphatidic acid and hydrogen peroxide and translocated to nucleus during salt stress

Mitogen-activated protein kinase (MAPK) is activated by various biotic and abiotic stresses. Salt stress induces two well-characterized MAPK activating signaling molecules, phosphatidic acid (PA) via phospholipase D and phospholipase C, and reactive oxygen species (ROS) via nicotinamide adenine dinucleotide phosphate (NADPH)-oxidase. In our previous study, the activity of soybean MAPK, GMK1 was strongly induced within 5 min of 300 mM NaCl treatment and this early activity was regulated by PA. In this study, we focused on the regulation of GMK1 at the later stage of the salt stress, because its activity was strongly persistent for up to 30 min. H₂O₂ activated GMK1 even in the presence of PA generation inhibitors, but GMK1 activity was greatly decreased in the presence of diphenyleneiodonium, an inhibitor of NADPH-oxidase after 5 min of the treatment. On the contrary, the n-butanol and neomycin reduced GMK1 activity within 5 min of the treatment. Thus, GMK1 activity may be sustained by H₂O₂ 10 min after the treatment. Further, GMK1 was translocated into the nucleus 60 min after NaCl treatment. In the relationship between GMK1 and ROS generation, ROS generation was reduced by SB202190, a MAPK inhibitor, but was increased in protoplast overexpressing TESD-GMKK1. However, these effects were occurred at prolonged time of NaCl treatment. These data suggest that GMK1 indirectly regulates ROS generation. Taken together, we propose that soybean GMK1 is dually regulated by PA and H₂O₂ at a time dependant manner and translocated to the nucleus by the salt stress signal.     

Separately and simultaneously induced dark chilling and drought stress effects on photosynthesis, proline accumulation and antioxidant metabolism in soybean

The effects of separately or simultaneously induced dark chilling and drought stress were evaluated in two Glycine max (L.) Merrill cultivars. For the separately induced dark chilling treatment (C), plants were incubated at 8 °C during 9 consecutive dark periods. During the days, plants were kept at normal growth temperatures. For the separately induced drought treatment (D), plants were maintained at normal growth temperatures without irrigation. For the simultaneously induced dark chilling and drought stress treatment (CD), plants were dark chilled without irrigation. All treatments caused similar decreases in pre-dawn leaf water potential, but resulted in distinct physiological and biochemical effects on photosynthesis. In Maple Arrow, where C had the smallest effect on photosynthesis, prolonged CD caused less inhibition of photosynthesis compared to D. Compared to Fiskeby V, the photosynthetic apparatus of Maple Arrow appears to possess superior dark chilling tolerance, a property which probably also conveyed enhanced protection against CD. Proline accumulation was prevented by CD at the ψ_PD where D already resulted in considerable accumulation. The superior capacity for proline accumulation in Maple Arrow would seem to be an important factor in its stress tolerance. Antioxidant activity evoked by CD and D was higher than for C alone. In Fiskeby V, the small increase in ascorbate peroxidase (EC 1.11.1.7) activity, which was in most cases not accompanied by increased gluthatione reductase (EC 1.6.4.2) activity, could impact negatively on its stress tolerance. These results demonstrate large genotypic differences in response to chilling and drought stress, even between soybean cultivars regarded as chilling tolerant.     

The tomato ethylene receptor LE-ETR3 (NR) is not involved in mediating ozone sensitivity: causal relationships among ethylene emission, oxidative burst and tissue damage

The causal relationships among ethylene emission, oxidative burst and tissue damage, and the temporal expression patterns of some ethylene biosynthetic and responsive genes, were examined in the Never ripe (Nr) tomato (Lycopersicon esculentum) mutant and its isogenic wild type (cv. Pearson), to investigate the role played by the ethylene receptor LE-ETR3 (NR) in mediating the plant response to ozone (O(3)). Tomato plants were used in a time-course experiment in which they were exposed to acute O(3) fumigation with 200 nl l(-1) O(3) for 4 h. The pattern of leaf lesions indicated similar sensitivities to O(3) for cv. Pearson and Nr. In both genotypes, O(3) activated a hydrogen peroxide (H(2)O(2))-dependent oxidative burst, which was also ethylene-driven in Nr leaves. Ozone induced some ethylene and jasmonate biosynthetic and inducible genes, although with different timings and to different extents in the two genotypes. The overall data indicate that Nr retains partial sensitivity to ethylene, suggesting only a marginal role of the NR receptor in mediating the complex response of tomato plants to O(3).     

Adipokinetic hormone counteracts oxidative stress elicited in insects by hydrogen peroxide: in vivo and in vitro study

The role of adipokinetic hormone (AKH) in counteracting oxidative stress elicited in the insect body is studied in response to exogenously applied hydrogen peroxide, an important metabolite of oxidative processes. In vivo experiments reveal that the injection of hydrogen peroxide (8 µmol) into the haemocoel of the firebug, Pyrrhocoris apterus L. (Heteroptera: Pyrrhocoridae) increases the level of AKH by 2.8‐fold in the central nervous system (CNS) and by 3.8‐fold in the haemolymph. The injection of hydrogen peroxide also increases the mortality of experimental insects, whereas co‐injection of hydrogen peroxide with Pyrap‐AKH (40 pmol) reduces mortality to almost control levels. Importantly, an increase in haemolymph protein carbonyl levels (i.e. an oxidative stress biomarker) elicited by hydrogen peroxide is decreased by 3.6‐fold to control levels when hydrogen peroxide is co‐injected with Pyrap‐AKH. Similar results are obtained using in vitro experiments. Oxidative stress biomarkers such as malondialdehyde and protein carbonyls are significantly enhanced upon exposure of the isolated CNS to hydrogen peroxide in vitro, whereas co‐treatment of the CNS with hydrogen peroxide and Pyrap‐AKH reduces levels significantly. Moreover, a marked decrease in catalase activity compared with controls is recorded when the CNS is incubated with hydrogen peroxide. Incubation of the CNS with hydrogen peroxide and Pyrap‐AKH together curbs the negative effect on catalase activity. Taken together, the results of the present study provide strong support for the recently published data on the feedback regulation between oxidative stressors and AKH action, and implicate AKH in counteracting oxidative stress. The in vitro experiments should facilitate research on the mode of action of AKH in relation to oxidative stress, and could help clarify the key pathways involved in this process.     

Turning point in apoptosis/necrosis induced by hydrogen peroxide

The turning point between apoptosis and necrosis induced by hydrogen peroxide (H₂O₂) have been investigated using human T-lymphoma Jurkat cells. Cells treated with 50 μM H₂O₂ exhibited caspase-9 and caspase-3 activation, finally leading to apoptotic cell death. Treatment with 500 μM H₂O₂ did not exhibit caspase activation and changed the mode of death to necrosis. On the other hand, the release of cytochrome c from the mitochondria was observed under both conditions. Treatment with 500 μM H₂O₂, but not with 50 μM H₂O₂, caused a marked decrease in the intracellular ATP level; this is essential for apoptosome formation. H₂O₂-reducing enzymes such as cellular glutathione peroxidase (cGPx) and catalase, which are important for the activation of caspases, were active under the 500 μM H₂O₂ condition. Prevention of intracellular ATP loss, which did not influence cytochrome c release, significantly activated caspases, changing the mode of cell death from necrosis to apoptosis. These results suggest that ATP-dependent apoptosome formation determines whether H₂O₂-induced cell death is due to apoptosis or necrosis.     

Effects of moderate heat stress on photosynthesis: importance of thylakoid reactions, rubisco deactivation, reactive oxygen species, and thermotolerance provided by isoprene

Photosynthesis is particularly sensitive to heat stress and recent results provide important new insights into the mechanisms by which moderate heat stress reduces photosynthetic capacity. Perhaps most surprising is that there is little or no damage to photosystem II as a result of moderate heat stress even though moderate heat stress can reduce the photosynthetic rate to near zero. Moderate heat stress can stimulate dark reduction of plastoquinone and cyclic electron flow in the light. In addition, moderate heat stress may increase thylakoid leakiness. At the same time, rubisco deactivates at moderately high temperature. Relationships between effects of moderate heat on rubisco activation and thylakoid reactions are not yet clear. Reactive oxygen species such as H₂O₂ may also be important during moderate heat stress. Rubisco can make hydrogen peroxide as a result of oxygenase side reactions and H₂O₂ production by rubisco was recently shown to increase substantially with temperature. The ability to withstand moderately high temperature can be improved by altering thylakoid lipid composition or by supplying isoprene. In my opinion this indicates that thylakoid reactions are important during moderate heat stress. The deactivation of rubisco at moderately high temperature could be a parallel deleterious effect or a regulatory response to limit damage to thylakoid reactions.     

Inhibitory effects of echinoisoflavanone and sophoraisoflavanone D in Sophora chrysophylla SEEM on lipid peroxidation of mice brain homogenate by interaction of ferrous ion and hydrogen peroxide, in vitro

We present the results of an in vitro investigation of the inhibitory effects of echinoisoflavanone and sophoraisoflavanone D isolated from Sophora chrysophylla SEEM on lipid peroxidation of mice brain homogenate by interaction of ferrous ion and hydrogen peroxide, in vitro. They inhibited lipid peroxidation. The order of inhibitory effects of these isoflavanones and mannitol as a hydroxy radical scavenger was echinoisoflavanone > mannitol > sophoraisoflavanone D. The results suggest that some isoflavanones may be of use in cases where oxidative stress is present.     

Catalase, but not MnSOD, inhibits glucose deprivation-activated ASK1-MEK-MAPK signal transduction pathway and prevents relocalization of Daxx: hydrogen peroxide as a major second messenger of metabolic oxidative stress

Overexpression of catalase, but not manganese superoxide dismutase (MnSOD), inhibited glucose deprivation-induced cytotoxicity and c-Jun N-terminal kinase 1 (JNK1) activation in human prostate adenocarcinoma DU-145 cells. Suppression of JNK1 activation by catalase overexpression resulted from inhibition of apoptosis signal-regulating kinase 1 (ASK1) activation by preventing dissociation of thioredoxin (TRX) from ASK1. Overexpression of catalase also inhibited relocalization of Daxx from the nucleus to the cytoplasm as well as association of Daxx with ASK1 during glucose deprivation. Taken together, hydrogen peroxide (H(2)O(2)) rather than superoxide anion (O(2) (*-)) acts as a second messenger of metabolic oxidative stress to activate the ASK1-MAPK/extracellular signal-regulated kinase (ERK) kinase (MEK)-mitogen-activated protein kinase (MAPK) signal transduction pathway.     

Plant water status, ethylene evolution, N(2)-fixing efficiency, antioxidant activity and lipid peroxidation in Cicer arietinum L. nodules as affected by short-term salinization and desalinization

Salinity induced changes in ethylene evolution, antioxidant defense system, N(2)-fixing efficiency and membrane integrity in relation to water and mineral status in chickpea (Cicer arietinum L.) nodules were studied under screen house conditions. At vegetative stage (55-65 DAS) plants were exposed to single saline irrigation (Cl(-) dominated) of levels 0, 2.5, 5.0 and 10.0dSm(-1) and sampled after 3d. The other set of treated plants was desalinized by flooding and the plants were sampled after further 3d. Water potential (Psiw) of leaf and osmotic potential (Psis) of leaf and nodules significantly decreased from -0.44 to -0.56MPa and from -0.65 to -1.15MPa and from -0.75 to -1.77MPa, respectively upon salinization. RWC of leaf and nodules also reduced from 86.05% to 73.30% and 94.70% to 89.98%, respectively. The decline in Psis of nodules was due to accumulation of proline and total soluble sugar. In comparison to control, the increase in ethylene (C(2)H(4)) production was 35-108% higher and correspondingly increase in 1-aminocycloprane-1-carboxylic acid (ACC) content (37-126%) and ACC oxidase activity (31-118%) was also noticed. Similarly, marked increase in H(2)O(2) (25-139%) and thiobarbituric acid substances (TBRAS, 11-133%) contents was seen. N(2)-fixing efficiency i.e. N(2)-ase activity, leghemoglobin and N contents of nodules declined significantly after saline irrigation. The induction in specific activity of antioxidant enzymes was confirmed by the increase in activity of superoxide dismutase, peroxidase, ascorbate peroxidase, glutathione reductase and glutathione transferase, whereas reverse was true for catalase. These activated enzymes could not overcome the accumulation of H(2)O(2) in nodules. Ascorbic acid content also declined from 20 to 38%, whereas Na(+)/K(+) ratio and Cl(-) content were significantly enhanced. Upon desalinization, a partial recovery in all above metabolic processes and water relations parameters was noticed. It is suggested that ethylene in relation to water status and lipid peroxidation and along with other metabolic processes has an important role in induced nodules senescence under salinity.     

Effect of overexpression of wild-type and mutant Cu/Zn-superoxide dismutases on oxidative stress and cell death induced by hydrogen peroxide, 4-hydroxynonenal or serum deprivation: potentiation of injury by ALS-related mutant superoxide dismutases and protection by Bcl-2

Mutations in Cu/Zn-superoxide dismutase (SOD1) are associated with some cases of familial amyotrophic lateral sclerosis (ALS). We overexpressed Bcl-2, wild-type SOD1 or mutant SOD1s (G37R and G85R) in NT-2 and SK-N-MC cells. Overexpression of Bcl-2 rendered cells more resistant to apoptosis induced by serum withdrawal, H2O2 or 4-hydroxy-2-trans-nonenal (HNE). Overexpression of Bcl-2 had little effect on levels of protein carbonyls, lipid peroxidation, 8-hydroxyguanine (8-OHG) or 3-nitrotyrosine. Serum withdrawal or H2O2 raised levels of protein carbonyls, lipid peroxidation, 8-OHG and 3-nitrotyrosine, changes that were attenuated in cells overexpressing Bcl-2. Overexpression of either SOD1 mutant tended to increase levels of lipid peroxidation, protein carbonyls, and 3-nitrotyrosine and accelerated viability loss induced by serum withdrawal, H2O2 or HNE, accompanied by greater rises in oxidative damage parameters. The effects of mutant SOD1s were attenuated by Bcl-2. By contrast, expression of wild-type SOD1 rendered cells more resistant to loss of viability induced by serum deprivation, HNE or H2O2. The levels of lipid peroxidation in wild-type SOD1 transfectants were elevated. Overexpression of mutant SOD1s makes cells more predisposed to undergo apoptosis in response to several insults. Our cellular systems appear to mimic events in patients with ALS or transgenic mice overexpressing mutant SOD1.     

Antioxidant status of Lobiger serradifalci and Oxynoe olivacea (Opisthobranchia, Mollusca)

Invasion of the Mediterranean Sea by the two world-wide famous exotic algae species, Caulerpa taxifolia and Caulerpa racemosa, is still a problem and has adverse effects on the Mediterranean sublittoral ecosystem. Biological control studies revealed that the two native Sacoglossans, Oxynoe olivacea and Lobiger serradifalci, may have an effect on the expansion of invasive Caulerpa spp. in the Mediterranean. In the framework of this study, antioxidant enzyme activities, such as superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px), lipid peroxidation (LPO) and oxidized glutathione (GSSG) levels, as oxidative stress markers in L. serradifalci and O. olivacea were determined at two different temperature conditions (20 and 27 °C). In both species, SOD, CAT and GSH-Px activities were found to be positively correlated with temperature. The SOD activities in L. serradifalci were higher than those in O. olivacea at both temperatures, whereas the CAT and GSH-Px activities were significantly (p<0.05) higher in O. olivacea, compared to L. serradifalci. As expected, both species showed decreased LPO levels at 27 °C compared to 20 °C. GSSG level at 27 °C in O.olivacea was significantly (p<0.05) higher than that of 20 °C. On the other hand, no statistical (p>0.05) difference in L.serradifalci existed between GSSG levels at two temperatures. But, despite the variations in the antioxidant enzyme activities, there was no significant difference in LPO levels between the species, suggesting that the oxidative consequences of a given environmental condition may vary among different species. Inasmuch as the GSSG levels were in accordance with antioxidant enzyme activities, GSH might have acted as a cofactor of GSH-Px and an individual antioxidant in these sea slugs.