Effect of short-term salt stress on oxidative stress markers and antioxidant enzymes activity in tocopherol-deficient Arabidopsis thaliana plants

Changes of carotenoids and anthocyanins content, lipid peroxidation, and activity of antioxidant enzymes were studied in wild type and tocopherol-deficient lines vte1 and vte4 of Arabidopsis thaliana subjected to 200 mM NaCI during 24 h. The salt stress enhanced the intensity of lipid peroxidation to different extent in all three plant lines. Salt stress resulted in an increase of carotenoid content and activity of catalase, ascorbate peroxidase, guaiacol peroxidase and glutathione reductase in wild type and tocopherol-deficient vte1 mutant. However, the increase in anthocyanins concentration was observed in vte1 mutants only. In vte4 mutant, which contain gamma-tocopherol instead of alpha-tocopherol, the response to salt stress occurred via coordinative action of superoxide dismutase and enzymes of ascorbate-glutathione cycle, in particular, ascorbate peroxidase, glutathione reductase, dehydroascorbate reductase, and glutathione-S-transferase. It can be concluded, that salt stress was accompanied by oxidative stress in three studied lines, however different mechanisms involved in adaptation of wild type and tocopherol-deficient lines to salt stress.     

Responses of Camellia sinensis to Drought and Rehydration

The effects of drought and rehydration on tea seedlings were significant. After five days of drought imposition the contents of chlorophylls, carotenoids, ascorbate and glutathione, and activities of guaiacol peroxidase and glutathione reductase decreased. Simultaneously, contents of proline, H₂O₂ and superoxide anion, lipid peroxidation and activities of catalase and superoxide dismutase increased. These parameters recovered to different degrees during subsequent rehydration.     

Inactivation of genes,encoding tocopherol biosynthetic pathway enzymes,results in oxidative stress in outdoor grown Arabidopsis thaliana

Tocopherols (α-, β-, γ- and δ-tocopherols) represent a group of lipophilic antioxidants which are synthesized only by photosynthetic organisms. It is widely believed that protection of pigments and proteins of photosynthetic system and polyunsaturated fatty acids from oxidative damage caused by reactive oxygen species (ROS) is the main function of tocopherols. The wild type Columbia and two mutants of Arabidopsis thaliana with T-DNA insertions in tocopherol biosynthesis genes – tocopherol cyclase (vte1) and γ-tocopherol methyltransferase (vte4) – were analyzed after long-term outdoor growth. The concentration of total tocopherol was up to 12-fold higher in outdoor growing wild type and vte4 plant lines than in plants grown under laboratory conditions. The vte4 mutant plants had a lower concentration of chlorophylls and carotenoids, whereas the mutant plants had a higher level of total glutathione than of wild type. The activities of antioxidant enzymes superoxide dismutase (SOD, EC 1.15.1.1) and ascorbate oxidase (AO, EC 1.10.3.3) were lower in both mutants, whereas activities of catalase (EC 1.11.1.6) and ascorbate peroxidase (APx, EC 1.11.1.11) were lower only in vte1 mutant plants in comparison to wild type plants. However, the activity of guaiacol peroxidase (GuPx, EC 1.11.1.7) was higher in vte1 and vte4 mutants than that in wild type. Additionally, both mutant plant lines had higher concentration of protein carbonyl groups and oxidized glutathione compared to the wild type, indicating the development of oxidative stress. These results demonstrate in plants that tocopherols play a crucial role for growth of plants under outdoor conditions by preventing oxidation of cellular components.     

Effect of high sodium chloride concentrations on the pigment content and free-radical processes in corn seedlings leaves

The effect of sodium chloride on general morphometrical parameters of seedlings, and biochemical parameters in the leaves of corn seedlings was studied. Exposure to 100 and 200 mM NaCl slowed down the growth of stem and roots, whereas 100 and 200 mM NaCl during 24 h enhanced the concentration of chlorophylls, carotenoids, anthocyans, and thiobarbituric acid reactive substances. The decrease in protein carbonyl groups was found at 24-hour exposure to 200 mM salt. The treatment during 24, 48 and 72 h to 200 mM salt increased the level of total and high molecular mass thiols, whereas low molecular mass thiol content was by 20-25% higher at 48 h exposure to all used salt concentrations. The activity of guaiacol peroxidase was higher only at 24 h exposure to 100 and 200 mM salt, and catalase--at 50 mM during 48 h. At 72-hour exposure, catalase activity was by 27 and 41% higher in seedlings, exposed to 50 and 200 mM NaCl, respectively. Therefore, it is concluded the plant exposure to 50-200 mM salt initially developed oxidative stress, inducing adaptive response--an increase in antioxidant potential and efficiency of systems of energy production. That results in plant adaptation to unfavourable conditions.     

Effect of sodium nitroprusside and S-nitrosoglutathione on pigment content and antioxidant system of tocopherol-deficient plants of Arabidopsis thaliana

Sodium nitroprusside (SNP) and S-nitrosoglutathione (GSNO) were used as a source of exogenous nitric oxide (NO) to investigate their effects on biochemical parameters and antioxidant enzyme response in leaves of wild type Columbia and tocopherol-deficient vte4 and vte1 mutant lines of Arabidopsis thaliana plants and possible tocopherol involvement in regulation of antioxidant response under NO-induced stress. SNP enhanced the activity of the enzymes, that scavenge hydrogen peroxide in leaves of all studied lines, and increased glutathione reductase and glutathione-S-transferase activity there. In addition, it decreased the intensity of lipid peroxidation in vte1 mutant line leaves. At the same time, GSNO increased the levels of protein carbonyls and inactivated enzymes ascorbate peroxidase, guaiacol peroxidase and dehydroascorbate reductase in almost all investigated plant lines. In contrast to wild type, GSNO increased superoxide dismutase activity and decreased catalase activity and chlorophyll a/b ratio in the leaves of two mutant lines. It can be assumed that tocopherols in some way are responsible for plant protection against NO-induced stress. However the mechanisms of this protection remain unknown.     

Nitrogen and Azotobacter chroococcum enhance oxidative stress tolerance in sugar beet

After treatment with increased quantities of nitrogen and Azotobacter strains, activities of antioxidant enzymes superoxide dismutase, peroxidase and catalase, content of chlorophylls and carotenoids, soluble proteins and dry matter in leaves of sugar beet increased. This revised version was published online in July 2006 with corrections to the Cover Date.     

Effect of short-term exposure to NaCl on photochemical activity and antioxidant enzymes in <Emphasis Type="Italic">Bruguiera parviflora</Emphasis>, a non-secretor mangrove

Effect of short-term (6 days) exposure to high salinity (500 mM NaCl) was studied in Bruguiera parviflora, a tree mangrove. NaCl treatment decreased photochemical activity, but had no effect on growth. Thylakoid protein profile and spectral characteristic were not changed. There was no significant effect on chlorophylls and carotenoids content, total proteins and total free amino acids. However, there was an increase in free proline. The activity of antioxidant enzymes like catalase, ascorbate peroxidase was enhanced, but no significant change in guaiacol peroxidase was observed. Salinity did not cause any alteration in malondialdehyde formation indicating intactness of membrane integrity upon high salinity. We conclude that the effect of high NaCl stress is not revealed in morphology of the plants, but in the metabolic changes as increase in proline and antioxidant enzyme activity. These effects are the adaptive mechanisms that operates under high salt stress in this mangrove; however, the decrease in photochemical activity may be due to onset of senescence which helps plant in remobilization of photosynthate to new leaves after adaptation.     

Mechanisms of the selenium tolerance of the Arabidopsis thaliana knockout mutant of sulfate transporter SULTR1;2

We investigated the mechanism of selenium (Se) tolerance using an Arabidopsis thaliana knockout mutant of a sulfate transporter, sultr1;2. Se stress inhibited plant growth, decreased chlorophyll contents, and increased protein oxidation and lipid peroxidation in the wild type, whereas the sultr1;2 mutation mitigated damage of these forms, indicating that sultr1;2 is more tolerant of Se than the wild type is. The accumulation of symplastic Se was suppressed in sultr1;2 as compared to the wild type, and the chemical speciation of Se in the mutant was different from that in the wild type. Regardless of Se stress, the activities of ascorbate peroxidase, catalase, and peroxidase in the mutant were higher than in the wild type, while the activity of superoxide dismutase in the mutant was the same as in the wild type. These results suggest that the sultr1;2 mutation confers Se tolerance on Arabidopsis by decreasing symplastic Se and maintaining antioxidant enzyme activities.     

A barley mutant with improved salt tolerance through ion homeostasis and ROS scavenging under salt stress

To investigate key regulatory components and genes with great impact on salt tolerance, near isogenic or mutant lines with distinct salinity tolerance are suitable genetic materials to simplify and dissect the complex genes networks. In this study, we evaluated responses of a barley mutant genotype (73-M4-30), in comparison with its wild-type background (Zarjou) under salt stress. Although the root growth of both genotypes was significantly decreased by exposure to sodium chloride (NaCl), the effect was greater in the wild type. The chlorophyll content decreased under salt stress for the wild type, but no change occurred in the mutant. The mutant maintained the steady-state level of [K⁺] and significantly lower [Na⁺] concentrations in roots and higher [K⁺]/[Na⁺] ratio in shoots under salt conditions. The catalase (CAT), peroxidase (POD) activity, and proline content were higher in the mutant than those in the wild type under controlled conditions. The soluble proline was higher after 24 h of salt stress in roots of the mutant but was higher after 96 h of salt stress in the wild type. The CAT and POD activity of the mutant increased under salt stress which was as a coincidence to lower levels of hydrogen peroxide (H₂O₂) and malondialdehyde (MDA) contents. The ratio of dry-to-fresh weight of the roots increased for the mutant under salt stress which was as a result of the higher phenylalanine ammonia-lyase (PAL) gene expression and peroxidase activity and involved in cell wall lignification. Consequently, it seems that ion homeostasis and increased peroxidase activity have led to salt tolerance in the mutant’s genotype.     

Daily Fluctuations of Antioxidants in Bean (Phaseolus vulgaris L.) Leaves As Affected by the Presence of Ambient Air Pollutants

During the period 0800–1700 h (GMT) of a summer day, youngleaves were collected every 20 min from Phaseolus vulgaris L.cv. Horticultural plants grown in open-top field chambers locatedat an urban site in northern Italy and exposed either to ambientlevels of gaseous air pollutants or to filtered ambient air.Ascorbic and dehydroascorbic acids, GSH and GSSG, superoxidedismutase, ascorbate peroxidase, dehydroascorbate reductase,GSSG reductase, GSH peroxidase, catalase, guaiacol peroxidase,chlorophylls, carotenoids, soluble protein and dry weight weremeasured in these leaves. The main differences between treatedand control leaves were observed during the period 1100–1530h and concerned superoxide dismutase, catalase, ascorbate peroxidase,ascorbate/dehydroascorbate and GSH/GSSG ratios, chlorophylls,carotenoids and dry weight. On the basis of the pollution climateobserved at the experimental site on the day of leaves sampling,ozone appeared to be the causative agent of the observed divergencesamong the time patterns of antioxidants in treated and controlplants. It was deduced that ozone can induce oxidative stressvia the production of superoxide radical anion and hydrogenperoxide. (Received June 1, 1992; Accepted December 9, 1992)     

Salinity up-regulates the antioxidative system in root mitochondria and peroxisomes of the wild salt-tolerant tomato species Lycopersicon pennellii

The effect of salinity on the antioxidative system of root mitochondria and peroxisomes of a cultivated tomato Lycopersicon esculentum (Lem) and its wild salt-tolerant related species L. pennellii (Lpa) was studied. Salt stress induced oxidative stress in Lem mitochondria, as indicated by the increased levels of lipid peroxidation and H(2)O(2). These changes were associated with decreased activities of superoxide dismutase (SOD) and guaiacol peroxidases (POD) and contents of ascorbate (ASC) and glutathione (GSH). By contrast, in mitochondria of salt-treated Lpa plants both H(2)O(2) and lipid peroxidation levels decreased while the levels of ASC and GSH and activities of SOD, several isoforms of ascorbate peroxidase (APX), and POD increased. Similarly to mitochondria, peroxisomes isolated from roots of salt-treated Lpa plants exhibited also decreased levels of lipid peroxidation and H(2)O(2) and increased SOD, ascorbate peroxidase (APX), and catalase (CAT) activities. In spite of the fact that salt stress decreased activities of antioxidant enzymes in Lem peroxisome, oxidative stress was not evident in these organelles.     

Morpho-physiological and antioxidant response to NaCl-induced stress in in vitro shoots of pomegranate (<Emphasis Type="Italic">Punica granatum</Emphasis> L.)

The physiological and antioxidant response to salinity was studied in pomegranate (Punica granatum L.) by exposing in vitro growing shoots of the Italian variety Profeta Partanna to 125 or 250 mM NaCl for 10 and 20 days. 250 mM NaCl significantly reduced shoot length, leaf area and water content of the shoots, regardless the length of the salt treatment,with respect to the control and to the 125 mM NaCl treatment. After 20 days the shoots treated with 250 mM NaCl also showed a significant reduction in relative growth rate (RGR) together with marked necroses and abscission of the oldest leaves. Salt treatments significantly decreased the contents of chlorophylls and carotenoids in both exposure times, depending on NaCl concentration. Proline, total phenolic compounds and ellagic acid did not increase or even decrease with the salt treatments. The levels of lipid peroxidation decreased, ascorbate peroxidase (APX) activity significantly increased in both treatment times and concentrations, while guaiacol peroxidase (G-POD) activity significantly increased in shoots treated with 250 mM NaCl for 20 days suggesting the rapid involvement of APX in controlling the oxidative stress in this species, even at low salt concentrations, and a delayed complementary role of G-POD.     

Hydrogen peroxide pre-treatment induces salt-stress acclimation in maize plants

The effect of exogenously applied H2O2 on salt stress acclimation was studied with regard to plant growth, lipid peroxidation, and activity of antioxidative enzymes in leaves and roots of a salt-sensitive maize genotype. Pre-treatment by addition of 1 microM H2O2 to the hydroponic solution for 2 days induced an increase in salt tolerance during subsequent exposure to salt stress. This was evidenced by plant growth, lipid peroxidation and antioxidative enzymes measurements. In both leaves and roots the variations in lipid peroxidation and antioxidative enzymes (superoxide dismutase, ascorbate peroxidase, guaiacol peroxidase, glutathione reductase, and catalase) activities of both acclimated and unacclimated plants, suggest that differences in the antioxidative enzyme activities may, at least in part, explain the increased tolerance of acclimated plants to salt stress, and that H2O2 metabolism is involved as signal in the processes of maize salt acclimation.     

Acetylsalicylic acid ameliorates negative effects of NaCl or osmotic stress in Solanum stoloniferum in vitro

The role of acetylsalicylic acid (0, 1 and 10 μM) pre-treatment in amelioration of salt and osmotic stress in a wild species of potato (Solanum stoloniferum) was investigated. We compared the effects of iso-osmotic concentrations of polyethylene glycol 6000 (15 %) and NaCl (80 mM) on the physiological responses of this species in explants grown in the liquid Murashige and Skoog medium. Both salt and drought reduced shoot growth parameters, photosynthetic pigment contents and increased lipid peroxidation, electrolyte leakage, H₂O₂ content and lipoxygenase activity. The effect of NaCl was more severe than that of polyethylene glycol. Salinity also increased Na⁺ content and decreased K⁺ content and K⁺/Na⁺ ratio. Under both stresses, the activities of superoxide dismutase, guaiacol peroxidase, ascorbate peroxidase, catalase and glutathione reductase enzymes were increased. Acetylsalicylic acid pre-treatment alleviated the adverse effects of both stresses on all parameters measured.     

Induction of Oxidative Stress in Roots of Oryza sativa L. in Response to Salt Stress

With the imposition of salt stress (0.5 to 3 % NaCl or CaCl₂) a decrease in germination rate and accumulation of proline was observed in the root tissue. Both NaCl and CaCl₂ solutions induced an increase in the total peroxide content and lipid peroxidation and decrease in catalase, guaiacol peroxidase and superoxide dismutase activities in root tissues suggesting an oxidative stress in the salt sensitive rice cultivar.     

转萝卜过氧化物酶基因Rsprx1提高毕赤酵母抗盐性

为探讨转萝卜过氧化物酶基因（Rsprx1）提高毕赤酵母(Pichia pastoris)抗盐性机理,用不同浓度NaCl处理转基因酵母GSRP25和野生型酵母GS115,检测菌体生长、相对无机盐含量、过氧化物酶活性和同工酶谱及某些抗性基因表达．实验结果表明,在YPD培养条件下,转基因酵母的过氧化物酶活性和菌体生长速率高于野生型酵母,其过氧化氢酶（CTT1）、热休克蛋白（Hsp12）、Rsprx1基因表达和K+/Na+比值均高于野生型．醛脱氢酶（ALD3）的mRNA表达在两者之间没有差异．在BMMY培养条件下,转基因酵母菌体生长速率和过氧化物酶活性显著高于野生型酵母．因此,转基因酵母通过增加过氧化物酶基因表达提高过氧化物酶活性,改变细胞的某些基因表达和无机盐相对含量,从而提高酵母抗盐能力．     

Interactive effects of salicylic acid and nitric oxide on soybean plants under NaCl salinity

The effects of salicylic acid (SA), sodium nitroprusside (SNP), a nitric oxide donor, and their combination (SA+SNP) on some physiological parameters of 23-day-old soybean seedlings grown under saline and nonsaline conditions were studied. The changes in the leaf area, shoot fresh and dry weights, contents of chlorophylls and carotenoids, amounts of MDA and hydrogen peroxide showed that the addition of 100 μM SA and/or 100 μM SNP markedly declined the oxidative damage to soybean plants induced by 50 and 100 μM NaCl. Our results proved that combined action of SA and nitric oxide donor significantly activated catalase (CAT), ascorbate peroxidase (APX), and guaiacol peroxidase (GPX), which contributed to the decay of H₂O₂ in soybean leaves under NaCl toxicity. The protective action of (SA+SNP) against saltinduced oxidative damage was often more efficient than effects of SA and SNP alone. We also observed that the accumulation of proline was apparently accelerated by these substances under salt stress. As well, it was observed that the interaction between SA and nitric oxide had synergistic effects in decreasing of the damages induced by NaCl salinity.     

Expression of arabidopsis cytosolic ascorbate peroxidase gene in response to ozone or sulfur dioxide

The effects of ozone or sulfur dioxide on antioxidant enzymes were investigated in Arabidopsis thaliana. Plants were fumigated with 0.1–0.15 ppm ozone or sulfur dioxide up to about 1 week in an environment-controlled chamber. Both pollutants increased the activities of ascorbate peroxidase and guaiacol per-oxidase in leaves, but had little effect on the activities of superoxide dismutase, catalase, monodehydroascorbate reductase, dehydroascorbate reductase or glutathione reductase. Ozone was more effective than sulfur dioxide in increasing the activities of the peroxidases. Ascorbate peroxidase activity increased 1.8-fold without a lag period during fumigation with 0.1 ppm ozone, while guaiacol peroxidase activity increased 4.4-fold with a 1-day lag. Expression of the APX1 gene encoding cytosolic ascorbate peroxidase was further investigated. Its protein levels in leaves exposed to 0.1 ppm ozone for 4 or 8 days were 1.5-fold higher than in controls. Both ozone and sulfur dioxide elevated APX1 mRNA levels in leaves at 4 and 7 days, whereas at 1 day only ozone was effective. The induction of APX1 mRNA levels by ozone (3.4- to 4.1-fold) was more prominent than that by sulfur dioxide (1.6-to 2.6-fold). The APX1 mRNA level increased by day and decreased by night. Exposure of plants to 0.1 ppm ozone enhanced the APX1 mRNA level within 3 h, which showed a diurnal rhythm similar to that of the control. These results demonstrate that near-ambient concentrations of ozone as well as similar concentrations of sulfur dioxide can induce APX1 gene expression in A. thaliana.Environmental Biology Division     

ABC转运体位于H2S上游参与盐胁迫诱导的拟南芥气孔关闭

本文以拟南芥野生型、ABC转运体缺失突变体（Atmrp4、Atmrp5和Atmrp4／5）为材料研究了硫化氢（hydrogensulfide,H2S）和ABC转运体在盐胁迫诱导拟南芥气孔关闭中的作用及其相互关系。结果表明,盐胁迫能够引起拟南芥叶片AtMRP4及AtMRP5表达量显著升高,诱导野生型拟南芥叶片气孔关闭,但对Atmrp4、Atmrp5及Atmrp4／5气孔开度无显著影响;而ABC转运体抑制剂格列本脲（glibenclamide,Gli）可减弱盐胁迫诱导的拟南芥气孔关闭的作用,表明ABC转运体参与盐胁迫诱导的拟南芥气孔关闭过程。盐胁迫能够引起野生型拟南芥H,s合成相关酶L-／D-半胱氨酸脱巯基酶（L-／D-CDes）活性及H2S含量显著升高,而ABc转运体抑制剂格列本脲处理后则没有这种变化,同时盐胁迫也不能引起Atmrp4、Atmrp5及Atmrp4／5的L-／19-CDes活性及H2S含量显著升高,表明ABC转运体位于H2s上游参与盐胁迫诱导气孔关闭过程。     

The activity of antioxidant enzymes in Arabidopsis thaliana exposed to colchicine and H2O2

Studies on the possible interference of colchicine and H2O2 with the activity of some antioxidant enzymes were carried out on Arabidopsis thaliana v. Columbia grown in Murashige and Skooge nutrient medium. Measurements of superoxide dismutase (SOD), guaiacol peroxidase (POX), ascorbate peroxidase (APX) and catalase (CAT) activities were conducted spectrophotometrically. In the presence of colchicine, SOD activity increased, while CAT, APX and POX activities decreased. Inhibitory H2O2 effects on the activity of the enzymes were found. Colchicine pre-treatment resulted in an increase in CAT activity and a further increase in SOD activity in plants treated with H2O2.