FeSOD Activity Research Articles

Variation in oxidative defense system and physiological traits in Maize under drought stress

The study included the role of key metabolites involved in oxidative defense, and osmotic adjustment under water stress is still undiscovered. We have evaluated whether antioxidant potential could be nominated as a potential marker of drought resistance in three maize hybrids (SC01, SC703, and SC720). Underwater deficiency in all maize hybrids decreased significantly compared to control samples in grain yield, photosynthetic pigments, and phenolic compounds. In contrast, proline and glycine betaine (GB) significantly increased. In contrast, a significant increase (p<?0.05) was detected in the lipid peroxidation indicator of malondialdehyde (MDA). The hydrogen peroxide (H2O2) and total soluble proteins remained unaffected under drought stress in the three maize hybrids. Electrophoretic investigations attributed three, two, and one isoforms, respectively, to peroxidase (POX), superoxide dismutase (SOD), and catalase (CAT). In the studied maize hybrids, SOD isoforms, including Fe-SOD, Cu/Zn-SOD, and Mn-SOD, appeared on the 8% slab polyacrylamide gels. The water stress decreases Mn-SOD, Cu/Zn-SOD, and Fe-SOD activities in all three hybrids. Further, POX1, POX2, and CAT activities decreased in SC01 and SC703, while they increased in SC720 under water deficit stress. In all maize hybrids, oxidative stress from water limitation leads to significant changes in the enzymatic/non-enzymatic antioxidants and main organic osmolytes. Based on the current study's findings, we believe that Cu/Zn-SOD activity, proline, and photosynthetic pigments might be used as biochemical indicators of water stress tolerance.

Study of the activity of antioxidant enzymes in somaclonal potato variants for use in selection for resistance to the PVS virus

The article presents the results of a study into the activity of the antioxidant system of potatoes in response to infection with the PVS virus. The PVS virus is widespread in the Omsk region. The work set out to study the activity of antioxidant enzymes in somaclonal potato variants when infected with PVS virus to obtain valuable varietal characteristics for use in breeding selection. Potato varieties Yermak, Alena and the Khozyayushka were selected from the Omsk Agrarian Scientific Centre breeding lines as objects of research. Differences in resistance to viral infection in varieties of different susceptibility and obtained somaclones were studied using the example of changes in the activity of the isoenzyme composition of antioxidant enzymes. The results showed that somaclone EC1, which was derived from the susceptible Yermak variety, had two additional isoenzymes upon infection and an increase in isoperoxidase activity compared to the control. Although the number of isoperoxidases did not increase in the samples obtained from the stable HC94 and the moderately susceptible AC91 variety, an increase in their activity was noted. Activation occurs in infected plants of the additional 3rd isoforms of catalase compared to the control – 1 isoform, while the 4th isoform of catalase was detected in the EC1 somaclonal sample. When studying the superoxide dismutase spectra, the control group showed the activity of Mp-SOD and Fe-SOD, while two forms of the enzyme were identified in the HC94, AC91 and EC1 somaclonal samples: Feand Cu/Zn-SOD. These forms play a significant role in the neutralisation of the superoxide radical.

Antioxidant enzymes of Pseudochlorella pringsheimii under two stressors: variation of SOD Isoforms activity

Algae are always facing the challenge of exposure to different stress conditions, therefore raising challenges of adaptation for survival. In this context, the growth and the antioxidant enzymes of the green stress-tolerant alga Pseudochlorella pringsheimii were investigated under two environmental stresses viz. iron and salinity. The number of algal cells was moderately increased by iron treatment in the range of 0.025–0.09 mM of iron, yet, the number of cells decreased at high iron concentrations (0.18 to 0.7 mM Fe). Furthermore, the different NaCl concentrations (8.5–136.0 mM) had an inhibitory effect on the algal cell number, compared to the control.The superoxide dismutase (SOD) showed three isoforms namely; Mn, Fe, and Cu/Zn SOD. The in gel and in vitro (tube-test) activities of FeSOD were higher compared with the other SOD isoforms. The activity of total SOD and its isoforms increased significantly by the different concentrations of Fe and non-significantly by NaCl. The maximum SOD activity was recorded at 0.7 mM Fe (67.9% above control). The relative expression of FeSOD was high under iron and NaCl at 8.5 and 34 mM, respectively. However, FeSOD expression was reduced at the highest NaCl tested concentration (136 mM). In addition, the antioxidant enzyme activity of catalase (CAT) and peroxidase (POD) were accelerated by increasing iron and salinity stress which indicates the essential role of these enzymes under stress. The correlation between the investigated parameters was also investigated. A highly significant positive correlation between the activity of total SOD and its isoforms, and with the relative expression of FeSOD was observed.

The Bioactivity of Xylene, Pyridine, and Pyrazole Aza Macrocycles against Three Representative Leishmania Species.

Due to the urgent need for finding effective and free of secondary effect treatments for every clinical form of Leishmaniasis, a series of synthetic xylene, pyridine and, pyrazole azamacrocycles were tested against three Leishmania species. A total of 14 compounds were tested against J774.2 macrophage cells which were models for host cells, and against promastigote and amastigote forms of each studied Leishmania parasite. Amongst these polyamines, one proved effective against L. donovani, another one for L. braziliensis and L. infantum, and another one was selective solely for L. infantum. These compounds showed leishmanicidal activity and reduced parasite infectivity and dividing ability. Action mechanism studies gave a hint that compounds were active against Leishmania due to their ability to alter parasite metabolic pathways and reduce (except Py33333) parasitic Fe-SOD activity.

Tolerance of Pyrus spp. and Cydonia oblonga as pear rootstocks to iron chlorosis determined by in vitro growth, antioxidant and molecular responses

Determination of Fe-efficient rootstock genotypes is important for the success of pear cultivation in calcareous soils. Otherwise, the use of iron-containing fertilizers against Fe-chlorosis for a long time may cause significant environmental hazards. In the present study, the morphological, antioxidant and molecular responses of Pyrus elaeagrifolia (AH-0 and AH-1 wild pear clones), P. communis (OHxF 333) and Cydonia oblonga (QA) as pear rootstocks to iron deficiency were determined in vitro micro shoots. Iron deficiency was created by reducing the amount of ferric-sodium EDTA added as 0.1 mM at full strength in modified Murashige and Skoog's basal medium to 0.03 mM or 0.0 mM. After six weeks in cultures, shoot proliferation percentage, shoot number per explant, shoot length, dry and fresh weight, proline content, H2O2, total chlorophyll and Fe content, CAT (EC 1.11.1.6), SOD (EC 1.15.1.1) and APX (EC 1.11.1.11) activities were determined. The expression of the dehydrin gene DQ660905 originated from Malus domestica associated with stress response was evaluated in Fe-deficient micro shoots at 1, 2, 4, 8 days after stress. According to the findings, the percentage of decrease in the number of shoots and length of wild pear clones were lower than those of OHxF 333 and QA under Fe deficiency. Fresh and dry weights of all genotypes were increased in media containing ferric-sodium EDTA. Under Fe deficiency conditions, total chlorophyll of micro shoots was reduced in all genotypes. However, the decrease was not statistically significant only in the AH-0 wild pear clone. Also, prolin remained statistically the same in this clone with the decrease of ferric-sodium EDTA level in the medium, but increased significantly in other genotypes. APX and SOD activities of AH-1 clone were higher than other genotypes in deficient conditions. Differential expression of the dehydrin gene DQ660905 revealed that the highest increase was determined in QA, AH-1 at day 1, and in AH-0 at day 4. The overall expression of OHxF 333 was lower than the other genotypes. In conclusion, according to the findings of the study, tolerance of wild pear clones to Fe deficiency was higher than OHxF 333 and QA rootstocks.

Differential responses of the scavenging systems for reactive oxygen species (ROS) and reactive carbonyl species (RCS) to UV-B irradiation in Arabidopsis thaliana and its high altitude perennial relative Arabis alpina.

The present work aimed to compare antioxidant response and lipid peroxide detoxification capacity of an arctic-alpine species Arabis alpina to its close relative model species Arabidopsis thaliana under acute short duration (3h and 6h) UV-B stress (4.6 and 8.2W/m2). After 3 and 6h exposure to UV-B, A. alpina showed lower lipid peroxidation and H2O2 accumulation when compared to A. thaliana. Moreover, Fv/Fm value of A. thaliana dropped to 0.70, while A. alpina dropped to 0.75 indicating better protection of PSII in this species. For elucidation of the antioxidant response, activities of superoxide dismutase (SOD), catalase (CAT), peroxidase (POX), ascorbate peroxidase (APX), glutathione reductase (GR) and dehydroascorbate reductase (DHAR) were measured. SOD induction with 6h of UV-B was more prominent in A. alpina. Also, A. alpina had higher chloroplastic FeSOD activity when compared to A. thaliana. APX activity was also significantly induced in A. alpina, while its activity decreased at 3h or did not change at 6h in A. thaliana. A. alpina was able to maintain constant CAT activity, but drastic decreases were observed in A. thaliana at both time points. Moreover, A. alpina was able to maintain or induce aldehyde dehydrogenase (ALDH), alkenal reductases (AERs) and glutathione-S-transferases (GST) activity, while an opposite trend was observed in A. thaliana. These findings indicate that A. alpina was able to maintain/induce its antioxidant defence and lipid peroxide detoxification conferring better protection against UV-B.

Effects of heat stress on photosystem II activity and antioxidant enzymes in two maize cultivars.

The main reason for the maize genotype "DKC7221" to be heat tolerant is to have higher photosynthetic activity under heat stress conditions. The genotype "P3167" is sensitive to high temperature because of the heat-induced inhibition in photosynthetic electron transport reactions. In the present study, the effect of heat stress (45ºC for 20min) on some physiological changes was investigated through a chlorophyll afluorescence technique, and some endogenous resistance mechanisms (activities of some antioxidant enzymes, free proline, and reduced ascorbate contents) in two maize cultivars (Zea mays L. cvs. P3167 and DKC7221). Chlorophyll fluorescence measurements demonstrated that heat stress led to the reduction in the efficiency of the Hill reaction, accumulation of inactive reaction centers, inhibition of electron flow from reaction centers to the plastoquinone pool, and induction of non-photochemical dissipation of absorbed light energy. Changes in Φo/(1 - Φo), SFIABS and PIABS indicated that electron transport reactions in P3167 were almost completely inhibited by heat stress. In DKC7221, however, photosynthetic electron transport reactions were maintained under heat stress conditions. As a result of impairment in the photosynthetic efficiency in P3167 under heat stress, oxidative stress appeared as shown by lower antioxidant activity, accumulation of H2O2, malondialdehyde, and formazon and photooxidative injuries in chlorophyll pigments in the leaf tissue. DKC7221, on the other hand, had a higher antioxidant efficiency and lower oxidative damage under heat stress. FeSOD activity was found to be responsible for the dismutation of superoxide radicals in both maize genotypes under heat stress. As a result, it may be concluded that the genotype DKC7221 is more tolerant to heat stress than P3167.

Increasing the copper sensitivity of microorganisms by restricting iron supply, a strategy for bio-management practices.

SummaryPollution by copper (Cu2+) extensively used as antimicrobial in agriculture and farming represents a threat to the environment and human health. Finding ways to make microorganisms sensitive to lower metal concentrations could help decreasing the use of Cu2 + in agriculture. In this respect, we showed that limiting iron (Fe) uptake makes bacteria much more susceptible to Cu2 + or Cd2+ poisoning. Using efflux mutants of the purple bacterium Rubrivivax gelatinosus, we showed that Cu+ and Cd2+ resistance relies on the expression of the Fur‐regulated FbpABC and Ftr iron transporters. To support this conclusion, inactivation of these Fe‐importers in the Cu+ or Cd2+‐ATPase efflux mutants gave rise to hypersensitivity towards these ions. Moreover, in metal overloaded cells the expression of FbpA, the periplasmic iron‐binding component of the ferric ion transport FbpABC system was induced, suggesting that cells perceived an ‘iron‐starvation’ situation and responded to it by inducing Fe‐importers. In this context, the Fe‐Sod activity increased in response to Fe homoeostasis dysregulation. Similar results were obtained for Vibrio cholerae and Escherichia coli, suggesting that perturbation of Fe‐homoeostasis by metal excess appeared as an adaptive response commonly used by a variety of bacteria. The presented data support a model in which metal excess induces Fe‐uptake to support [4Fe‐4S] synthesis and thereby induce ROS detoxification system.

New insights into cadmium stressful-conditions: Role of ethylene on selenium-mediated antioxidant enzymes

Cadmium (Cd) contamination has generated an environmental problem worldwide, leading to harmful effects on human health and damages to plant metabolism. Selenium (Se) is non essential for plants, however it can improve plant growth and reduce the adverse effects of abiotic stress. In addition, ethylene may interplay the positive effects of Se in plants. In order to investigate the role of ethylene in Se-modulation of antioxidant defence system in response to Cd-stress, we tested the hormonal mutant Epinastic (epi) with a subset of constitutive activation of the ethylene response and Micro-Tom (MT) plants. For this purpose, Se mineral uptake, Cd and Se concentrations, pigments, malondialdeyde (MDA) and hydrogen peroxide (H2O2) contents, ethylene production, glutathione (GSH) compound, and superoxide dismutase (SOD), ascorbate peroxidase (APX), catalase (CAT), glutathione reductase (GR) and glutathione peroxidase (GSH-Px) activities were analysed in MT and epi plants submitted to 0.5 mM CdCl2 and 1 μM of selenate or selenite. MT plants treated with both Se forms increased growth in the presence or not of 0.5 mM CdCl2, but not change epi growth. Both Se forms reduced Cd uptake in MT plants and cause reverse effect in epi plants. P, Mg, S, K and Zn uptake increased in epi plants with Se application, irrespective to Cd exposure. Chlorophylls and carotenoids contents decreased in both genotypes under Cd exposure, in contrast to what was observed in epi leaves in the presence of Se. When antioxidant enzymes activities were concerned, Se application increased Mn-SOD, Fe-SOD and APX activities. In the presence of Cd, MT and epi plants exhibited decreased SOD activity and increased CAT, APX and GR activities. MT and epi plants with Se supply exhibited increased APX and GR activities in the presence of Cd. Overall, these results suggest that ethylene may be involved in Se induced-defence responses, that triggers a positive response of the antioxidant system and improve growth under Cd stress. These results showed integrative roles of ethylene and Se in regulating the cell responses to stressful-conditions and, the cross-tolerance to stress could be used to manipulate ethylene regulated gene expression to induce heavy metal tolerance.

Assessment of the effects of zinc on the growth and antioxidant enzymes in Scenedesmus ellipsoideus Chodat

Abstract This study explores the activity of total superoxide dismutase (SOD), ascorbate peroxidase (APX) and glutathione reductase (GR), biomass accumulation and chlorophyll a content in Scenedesmus ellipsoideus Chodat grown under conditions of varying zinc (Zn) concentrations. In addition, the activity of different SOD isozymes (MnSOD, FeSOD and CuZnSOD) was measured separately to determine the intracellular extent of oxidative stress resulting from Zn toxicity. We found that the activity of FeSOD and MnSOD was induced by lower Zn concentration (2 μg ml−1 and 4 μg ml−1, respectively), whereas CuZnSOD activity was not affected, which indicates that chloroplasts are the first location in S. ellipsoideus cells where superoxide accumulation is accelerated by Zn toxicity. The activity of total SOD and APX was significantly increased by moderate Zn concentrations, probably due to some oxidative stress caused by Zn toxicity. The higher level of Zn application, however, led not only to the inhibition of total SOD and APX activity, but also to the reduction of biomass accumulation and chlorophyll a content. As a result, it can be concluded that the accumulation of superoxide radicals and H2O2 in S. ellipsoideus cells induced by Zn toxicity may be responsible for the reduced growth rate and the impairment of photosynthetic pigments.

Cytotoxic Activity of LCS-1 is not Only due to Inhibition of SOD1.

The cytotoxic activity of the pyridazin-3-one derivative LCS-1 was previously suggested to be due to the inhibition of superoxide dismutase 1 (SOD1). However, no direct evidence was provided that LCS-1 inhibits SOD1 within cells. In this study, we investigated the cytotoxic activity of LCS-1 against bloodstream forms of Trypanosoma brucei, a protozoan parasite that does not express copper/zinc-containing SOD1, but an iron-containing superoxide dismutase (FeSOD). At 250 µM, LCS-1 did not inhibit the activity of FeSOD in cell lysates of bloodstream forms of T. brucei, confirming that the compound is a specific inhibitor of SOD1. However, LCS-1 displayed substantial trypanocidal activity with a minimum inhibitory concentration of 10 µM and a half-maximal effective concentration of 1.36 µM, indicating that the cytotoxic action of the compound cannot solely be due to inhibition of SOD1. The results of this study is an important finding as it shows that LCS-1 has more than one cytotoxic mode of action.

Exogenous easily extractable glomalin-related soil protein improves drought tolerance of trifoliate orange

ABSTRACTMycorrhiza-released glomalin-related soil protein (GRSP) influences rhizosphere properties, but it is not clear whether exogenous GRSP enhances drought tolerance of plants. In this work, easily extracted GRSP (EE-GRSP) was isolated from Satsuma mandarin soil, and half-strength EE-GRSP (0.007 mg protein mL−1) was weekly applied into rhizosphere of potted trifoliate orange (Poncirus trifoliata) exposed to well watered (WW) and drought stress (DS). After four months, EE-GRSP-treated seedlings exhibited significantly higher plant growth (plant height, leaf number and fresh weight) and root growth-related parameters (lateral root numbers and root morphology) than non-EE-GRSP-treated seedlings under both WW and DS conditions. Exogenous EE-GRSP generally significantly increased leaf water potential, net photosynthesis rate, transpiration rate, stomatal conductance and intercellular CO2 concentration, while dramatically decreased leaf temperature, regardless of soil water status. The seedlings treated with exogenous EE-GRSP observed significantly higher activities of leaf Fe-SOD and root Mn-SOD, Cu/Zn-SOD, and Fe-SOD than untreated control under DS. Leaf abscisic acid, indole-acetic acid and methyl jasmonate concentrations were significantly higher in EE-GRSP-treated seedlings than untreated control under DS. This work firstly reported that exogenous application of EE-GRSP improved drought tolerance of trifoliate orange, thereby, offering a strong possibility in favour of EE-GRSP to be used as a plant growth regulator.

Nitric oxide triggers a concentration-dependent differential modulation of superoxide dismutase (FeSOD and Cu/ZnSOD) activity in sunflower seedling roots and cotyledons as an early and long distance signaling response to NaCl stress

Dark-grown sunflower (Helianthus annuus L.) seedlings exhibit modulation of total superoxide dismutase (SOD;EC 1.15.1.1) activity in roots and cotyledons (10,000g supernatant) in response to salt stress (NaCl; 120 mM) through a differential, zymographically detectable, whole tissue activity of FeSOD and Cu/ZnSOD. Confocal laser scanning microscopic imaging (CLSM) has further shown that NaCl stress significantly influences differential spatial distribution of Cu/ZnSOD and MnSOD isoforms in an inverse manner. Dual action of nitric oxide (NO) is evident in its crosstalk with FeSOD and Cu/ZnSOD in seedling roots and cotyledons in control and NaCl− stress conditions. Cu/ZnSOD activity in the roots of 2 d old NaCl− stressed seedlings is enhanced in the presence of 125–1000 µM of NO donor (sodium nitroprusside; SNP) indicating salt sensitivity of the enzyme activity. Quenching of endogenous NO by cPTIO treatment (500, 1000 µM) lowers FeSOD activity in roots (-NaCl). Cotyledons from control seedlings show an upregulation of FeSOD activity with increasing availability of SNP (125–1000 µM) in the Hoagland irrigation medium. Quenching of NO by cPTIO provides evidence for an inverse correlation between NO availability and FeSOD activity in seedling cotyledons irrespective of NaCl stress. Variable response due to NO on SOD isoforms in sunflower seedlings reflects its concentration-dependent biphasic (pro- and antioxidant) nature of action. Differential induction of SOD isoforms by NO indicates separate intracellular signaling pathways (associated with their respective functional separation) operative in seedling roots as an early salt stress mechanism and in cotyledons as an early long-distance NaCl stress sensing mechanism.

Characterization of the superoxide dismutase genes of the halophyte Suaeda maritima in Japan and Egypt.

Suaeda maritima varieties native to Japan and Egypt were cultured under aseptic conditions. The varieties differed in genetic distance but exhibited similar expression profiles of superoxide dismutase isozyme genes. The expression characteristics of superoxide dismutase (SOD; EC 1.15.1.1) isozyme genes from halophytic Suaeda marit ima plants native to Japan and Egypt were analyzed using young plants grown under aseptic conditions. A phylogenetic tree based on internal transcribed spacer sequences suggested that Egyptian S. maritima is related to European and India S. maritima, while Japanese S. maritima belongs to a separate clade. An in-gel SOD activity staining assay revealed that leaves from both the Egyptian and Japanese varieties showed high levels of CuZn-SOD and Fe-SOD activity, but no Mn-SOD activity; conversely, stems from both varieties showed Mn-SOD activity as well as other SOD isozyme activities. In Japanese S. maritima leaves, SOD activity was increased by incubation in growth medium containing 400 mM NaCl, while Egyptian S. maritima leaves showed elevated SOD activity in the absence of high salt. Genes encoding Mn-SOD and Fe-SOD were isolated from both plant types. RT-PCR analysis revealed that all SOD isozyme-encoding genes were expressed at the same levels in leaves from both plant types grown in normal or high-salt medium. In contrast, the expression of genes encoding choline monooxygenase and betaine aldehyde dehydrogenase, which are involved in betacyanin biosynthesis, was increased in high-salt medium. In leaves of Japanese S. maritima plants, Fe deficiency without high salt exposure preferentially decreased Fe-SOD activity. On the other hand, Fe deficiency with high salt exposure decreased not only Fe-SOD activity but also CuZn-SOD activity, suggesting that Fe availability is involved in the up-regulation of SOD isozymes mediating salt tolerance.

Modulation of superoxide dismutase (SOD) isozymes by organ development and high long-term salinity in the halophyte Cakile maritima.

Superoxide dismutase (SOD) activity catalyzes the disproportionation of superoxide radicals into hydrogen peroxide and oxygen. This enzyme is considered to be a first line of defense for controlling the production of reactive oxygen species (ROS). In this study, the number and type of SOD isozymes were identified in the principal organs (roots, stems, leaves, flowers, and seeds) of Cakile maritima. We also analyzed the way in which the activity of these SOD isozymes is modulated during development and under high long-term salinity (400 mM NaCl) stress conditions. The data indicate that this plant contains a total of ten SOD isozymes: two Mn-SODs, one Fe-SOD, and seven CuZn-SODs, with the Fe-SOD being the most prominent isozyme in the different organs analyzed. Moreover, the modulation of SOD isozymes, particularly CuZn-SODs, was only detected during development and under severe salinity stress conditions. These data suggest that, in C. maritima, the occurrence of these CuZn-SODs in roots and leaves plays an adaptive role since this CuZn-SOD isozyme might replace the diminished Fe-SOD activity under salinity stress to overcome this adverse environmental condition.

Inhibitory effects and oxidative target site of dibutyl phthalate on Karenia brevis

The inhibitory action and possible damage mechanism of dibutyl phthalate (DBP) on the red tide algae Karenia brevis were investigated. The results showed that the algae experienced oxidative stress after exposure to 5mgL−1 DBP. Malondialdehyde (MDA) peaked after 72h, with a value approximately 2.3 times higher than that observed for untreated cells. The superoxide dismutase (SOD) and catalase (CAT) activities significantly increased as an adaptive reaction after 48h. DBP induced the overproduction of reactive oxygen species (ROS), the OH concentration showed a peak of 33UmL−1 at 48h, and the highest H2O2 content was approximately 250nmol/107 cells at 72h; these latter two values were 2.5 and 4.4 times higher than observed for the control, respectively. TEM images showed that a number of small vacuoles or apical tubers were commonly found around the cell membrane, and the membrane structure was ultimately disintegrated. Further experiments were carried out to locate the original ROS production sites following DBP exposure. The activity of CuZn-SOD (a mainly cytosolic isoform, with some also found in chloroplasts) under DBP exposure was approximately 2.5 times higher than the control, whereas the Mn-SOD (mitochondrial isoform) activity was significantly inhibited. No significant difference was observed in the activity of Fe-SOD (chloroplastic isoform). In addition, dicumarol (an inhibitor of the electron transport chain in the plasma membrane) stimulated DBP-induced ROS production, whereas rotenone (an inhibitor of the mitochondria electron transport chain complex I) decreased DBP-induced ROS production. These results suggested that mitochondria could be the main target sites for DBP attack.

Protective effect of Mn(III)-desferrioxamine B upon oxidative stress caused by ozone and acid rain in the Brazilian soybean cultivar Glycine max "Sambaiba".

This study aimed to investigate the effects of the Mn complex (Mn(III)-desferrioxamine B (MnDFB)) on oxidative stress in the Brazilian soybean cultivar Glycine max "Sambaiba" following exposure to ozone and acid rain. We determined the suitable dose of MnDFB to apply to G. max seedlings using a dose-response curve. The highest superoxide dismutase (SOD) activity and Mn content in leaves were found upon the application of 8μM MnDFB. Thus, G. max seedlings pretreated with 8μM MnDFB were individually exposed to ozone and acid rain simulated. Pretreatment with MnDFB reduced lipid peroxidation upon ozone exposure and increased SOD activity in leaves; it did not alter the metal content in any part of the plant. Conversely, following acid rain exposure, neither the metal content in leaves nor SOD enzyme activity were directly affected by MnDFB, unlike pH. Our findings demonstrated that exogenous MnDFB application before ozone exposure may modulate the MnSOD, Cu/ZnSOD, and FeSOD activities to combat the ROS excess in the cell. Here, we demonstrated that the applied dose of MnDFB enhances antioxidative defenses in soybean following exposure to acid rain and especially to ozone.

Time-dependent changes in antioxidative enzyme expression and photosynthetic activity of Chlamydomonas reinhardtii cells under acute exposure to cadmium and anthracene

Heavy metals (HM) and polycyclic aromatic hydrocarbons (PAHs) are present in the freshwater environment at concentrations that can be hazardous to the biota. Among HMs and PAHs, cadmium (Cd) and anthracene (ANT) are the most prevalent and toxic ones. The response of Chlamydomonas cells to Cd and ANT at concentrations that markedly reduced the growth of algal population was investigated in this study. At such concentrations, both cadmium and anthracene were recognized as oxidative stress inducers, since high concentration of H2O2 in treated cultures was observed. Therefore, as a part of the “molecular phase” of the cell response to this stress, we examined the time-dependent expression of genes encoding the main antioxidative enzymes: superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (APX), as well as the activity of these enzymes in cells, with special attention paid to chloroplastic and mitochondrial isoforms of SOD. To characterize the cell response at the “physiological level”, we examined the photosynthetic activity of stressed cells via analysis of chlorophyll a fluorescence in vivo. In contrast to standard ecotoxicity studies in which the growth end-points are usually determined, herein we present time-dependent changes in algal cell response to Cd- and ANT-induced stress. The most significant effect(s) of the toxicants on photosynthetic activity was observed in the 6th hour, when strong depression of PI parameter value, an over 50 percent reduction of the active reaction center fraction (RC0) and a 3-fold increase in non-photochemical energy dissipation (DI0/RC) were noted. At the same time, the increase (up to 2.5-fold) in mRNA transcript of SOD and CAT genes, followed by the enhancement in the enzyme activity was observed. The high expression of the Msd 3 gene in treated Chlamydomonas cells probably complements the partial loss of chloroplast Fe-SOD and APX activity, while catalase and Mn-SOD 5 seem to be the major enzymes responsible for mitochondrion protection. The progressive increase in SOD and CAT activities seems to be involved in the recovery of photosynthesis within 12–24h after the application of the toxicants.

Deregulation of transition metals homeostasis is a key feature of cadmium toxicity in Salmonella.

Cadmium is a highly toxic metal whose presence in the environment represents a challenge for all forms of life. To improve our knowledge on cadmium toxicity, we have explored Salmonella Typhimurium responses to this metal. We have found that cadmium induces the concomitant expression of the cation efflux pump ZntA and of the high affinity zinc import system ZnuABC. This observation suggests that cadmium accumulation within the cell induces a condition of apparent zinc starvation, possibly due to the ability of this metal to compete with zinc for the metal binding site of proteins. This hypothesis is supported by the finding that strains lacking ZntA or ZnuABC are hyper-susceptible to cadmium and that the cadmium-induced growth defect of a znuABC mutant strain is largely relieved by zinc supplementation. A similar growth defect was observed for a mutant with impaired ability to acquire iron, whereas cadmium does not affect growth of a strain defective in manganese import. Cadmium also influences the expression and activity of the two cytoplasmic superoxide dismutases FeSOD and MnSOD, which are required to control cadmium-mediate oxidative stress. Exposure to cadmium causes a reduction of FeSOD activity in Salmonella wild type and the complete abrogation of its expression in the strain defective in iron import. In contrast, although MnSOD intracellular levels increase in response to cadmium, we observed discrepancies between protein levels and enzymatic activity which are suggestive of incorporation of non-catalytic metals in the active site or to cadmium-mediated inhibition of manganese import. Our results indicate that cadmium interferes with the ability of cells to manage transition metals and highlight the close interconnections between the homeostatic mechanisms regulating the intracellular levels of different metals.

Antioxidant defence in UV-irradiated tobacco leaves is centred on hydrogen-peroxide neutralization

Greenhouse grown tobacco (Nicotiana tabacum L. cv. Petit Havana) plants were exposed to supplemental UV centred at 318 nm and corresponding to 13.6 kJ m−2 d−1 biologically effective UV-B (280–315 nm) radiation. After 6 days this treatment decreased photosynthesis by 30%. Leaves responded by a large increase in UV-absorbing pigment content and antioxidant capacities. UV-stimulated defence against ROS was strongest in chloroplasts, since activities of plastid enzymes FeSOD and APX had larger relative increases than other, non-plastid specific SODs or peroxidases. In addition, non-enzymatic defence against hydroxyl radicals was doubled in UV treated leaves as compared to controls. In UV treated leaves, the extent of activation of ROS neutralizing capacities followed a peroxidases > hydroxyl-radical neutralization > SOD order. These results suggest that highly effective hydrogen peroxide neutralization is the focal point of surviving UV-inducible oxidative stress and argue against a direct signalling role of hydrogen peroxide in maintaining adaptation to UV, at least in laboratory experiments.