Reactive Oxygen Species Scavenging Enzymes Research Articles

Biochemical and physiological response to oxidative stress in cultivated sugarcane and wild genera

Sugarcane related genera and species exhibit tolerance to a number of abiotic stresses. In the present study, oxidative stress response was compared between Saccharum sp and their related genera using physiological and biochemical parameters. A pot culture experiment was conducted using five clones of Erianthus arundinaceus and two commercial varieties of Saccharum hybrids. The oxidative stress was induced by external application of hydrogen peroxide (H2O2) at different concentrations (control, 300, 500, 1000 ppm) on 65 days—old plants for three consecutive days in a glass house. Adaptive response in sugarcane/wild genera was estimated in terms of chlorophyll fluorescence, chlorophyll stability index, proline, soluble protein, and reactive oxygen species scavenging enzyme activities like super oxide dismutase and peroxidase. Analysis of variance was performed and significance of each group was verified with three-way analysis of variance (chlorophyll fluorescence, peroxidase, superoxide dismutase, lipid peroxidation, protein and proline content) and two way analysis of variance (chlorophyll stability index,) followed by Tukey HSD (P < 0.05). Significant interaction between clones, H2O2 treatment and time interval was observed. Two clones of Erianthus sp (IJ76-389 and IK76-91) exhibited relatively higher tolerance for oxidative stress at 500 and 1000 ppm of H2O2 with 48 h of treatment. In Erianthus sp, the percentage increase in enzyme activity was significant; the clone IS76-139 showed maximum peroxidase (60.9% increase) and super oxide dismutase activity (189.3% increase). Cell membrane damage due to lipid peroxidation has increased with increase in concentration of H2O2. Drought tolerant sugarcane variety Co 99004 showed 50.5% reduction in lipid peroxidation when compared to the variety Co 86032. Based on physiological and biochemical response, the effective concentration to induce the oxidative stress was found to be 500 ppm at 48 h after treatment.

Exposure to lower red to far-red light ratios improve tomato tolerance to salt stress

BackgroundRed (R) and far-red (FR) light distinctly influence phytochrome-mediated initial tomato growth and development, and more recent evidence indicates that these spectra also modulate responses to a multitude of abiotic and biotic stresses. This research investigated whether different R: FR values affect tomato growth response and salinity tolerance. Tomato seedlings were exposed to different R: FR conditions (7.4, 1.2 and 0.8) under salinity stress (100 mM NaCl), and evaluated for their growth, biochemical changes, active reactive oxygen species (ROS) and ROS scavenging enzymes, pigments, rate of photosynthesis, and chlorophyll fluorescence.ResultsThe results showed that under conditions of salinity, tomato seedlings subjected to a lower R: FR value (0.8) significantly increased both their growth, proline content, chlorophyll content and net photosynthesis rate (Pn), while they decreased malondialdehyde (MDA) compared to the higher R: FR value (7.4). Under conditions of salinity, the lower R: FR value caused a decrease in both the superoxide anion (O2•−) and in hydrogen peroxide (H2O2) generation, an increase in the activities of superoxidase dismutase (SOD, EC 1.15.1.1), peroxidase (POD, EC 1.11.1.7) and catalase (CAT, EC 1.11.1.7). Tomato seedlings grown under the lower R: FR value and conditions of salinity showed a higher actual quantum yield of photosynthesis (ΦPSII), electron transport rate (ETR), and photochemical quenching (qP) than those exposed to a higher R: FR, indicating overall healthier growth. However, the salinity tolerance induced at the lower R: FR condition disappeared in the tomato phyB1 mutant.ConlusionThese results suggest that growing tomato with a lower R: FR value could improve seedlings’ salinity tolerance, and phytochrome B1 play an very important role in this process. Therefore, different qualities of light can be used to efficiently develop abiotic stress tolerance in tomato cultivation.

Hydrogen sulfide treatment confers chilling tolerance in hawthorn fruit during cold storage by triggering endogenous H 2 S accumulation, enhancing antioxidant enzymes activity and promoting phenols accumulation

Abstract Cold storage as the postharvest beneficial procedure has been used for retaining sensory and nutritional quality and extending postharvest life of hawthorn fruit. However, fruit chilling injury (CI) manifested by pitting is a dominant restriction for applying cold storage for hawthorn fruit. In this experiment, the impacts of postharvest hydrogen sulfide (H2S) fumigation releasing from 0, 0.5, 1 and 1.5 mM H2S donor NaHS on chilling injury manifesting by pitting and nutritional quality of hawthorn fruit during storage at 1 °C for 20 days was evaluated. Our results revealed that 1.5 mM H2S donor NaHS treatment remarkably ameliorated fruit chilling injury, which was accompanied by lower malondialdehyde (MDA) accumulation. Hawthorn fruit in response to H2S donor NaHS treatment showed remarkably higher endogenous H2S accumulation by triggering l -cysteine desulfhydrase (LCD) and d -cysteine desulfhydrase (DCD) enzymes activity, which coincided with higher reactive oxygen species (ROS) scavenging enzymes superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APX) activity give rise to lower H2O2 accumulation. In addition, hawthorn fruit treated with H2S showed remarkably higher phenols, flavonoids, and anthocyanins accumulation by triggering phenylalanine ammonia lyase (PAL) enzyme activity. Higher DPPH scavenging activity in hawthorn fruit treated with H2S donor NaHS arise from higher phenols, flavonoids, anthocyanins and ascorbic acid accumulation. According to our results, postharvest 1.5 mM H2S donor NaHS applying may be considered as a beneficial procedure not only for conferring chilling tolerance of hawthorn fruit by triggering endogenous H2S accumulation, enhancing ROS scavenging enzymes activity and promoting phenols accumulation which are crucial for maintaining membrane integrity, but also for preserving nutritional quality of hawthorn fruit during cold storage.

MiR-9 upregulation leads to inhibition of erythropoiesis by repressing FoxO3

MicroRNAs (miRNAs) are emerging as critical regulators of normal and malignant hematopoiesis. In previous studies of acute myeloid leukemia miR-9 overexpression was commonly observed. Here, we show that ectopic expression of miR-9 in vitro and in vivo significantly blocks differentiation of erythroid progenitor cells with an increase in reactive oxygen species (ROS) production. Consistent with this observation, ROS scavenging enzymes, including superoxide dismutase (Sod2), Catalase (Cat), and glutathine peroxidase (Gpx1), are down-regulated by miR-9. In addition, miR-9 suppresses expression of the erythroid transcriptional regulator FoxO3, and its down-stream targets Btg1 and Cited 2 in erythroid progenitor cells, while expression of a constitutively active form of FoxO3 (FoxO3-3A) reverses miR-9-induced suppression of erythroid differentiation, and inhibits miR-9-induced ROS production. Thus, our findings indicate that aberrant expression of miR-9 blocks erythropoiesis by deregulating FoxO3-mediated pathways, which may contribute to the ineffective erythropoiesis observed in patients with hematological malignancies.

Multifunctional activities of ERF109 as affected by salt stress in Arabidopsis

Transcriptomic analysis was conducted in leaves of Arabidopsis T-DNA insertion ERF109-knocked out (KO) mutant or plants overexpressing (OE) the gene to detect its role in driving expression of programmed cell death- (PCD-) or growth-related genes under high salt (200 mM NaCl) stress. The analysis yielded ~22–24 million reads, of which 90% mapped to the Arabidopsis reference nuclear genome. Hierarchical cluster analysis of gene expression and principal component analysis (PCA) successfully separated transcriptomes of the two stress time points. Analysis indicated the occurrence of 65 clusters of gene expression with transcripts of four clusters differed at the genotype (e.g., WT (wild type), KOERF109 or OEERF109) level. Regulated transcripts involved DIAP1-like gene encoding a death-associated inhibitor of reactive oxygen species (ROS). Other ERF109-regulated transcripts belong to gene families encoding ROS scavenging enzymes and a large number of genes participating in three consecutive pathways, e.g., phenylalanine, tyrosine and tryptophan biosynthesis, tryptophan metabolism and plant hormone signal transduction. We investigated the possibility that ERF109 acts as a “master switch” mediator of a cascade of consecutive events across these three pathways initially by driving expression of ASA1 and YUC2 genes and possibly driving GST, IGPS and LAX2 genes. Action of downstream auxin-regulator, auxin-responsive as well as auxin carrier genes promotes plant cell growth under adverse conditions.

Non-canonical regulation of glutathione and trehalose biosynthesis characterizes non-Saccharomyces wine yeasts with poor performance in active dry yeast production.

Several yeast species, belonging to Saccharomyces and non-Saccharomyces genera, play fundamental roles during spontaneous must grape fermentation, and recent studies have shown that mixed fermentations, co-inoculated with S. cerevisiae and non-Saccharomyces strains, can improve wine organoleptic properties. During active dry yeast (ADY) production, antioxidant systems play an essential role in yeast survival and vitality as both biomass propagation and dehydration cause cellular oxidative stress and negatively affect technological performance. Mechanisms for adaptation and resistance to desiccation have been described for S. cerevisiae, but no data are available on the physiology and oxidative stress response of non-Saccharomyces wine yeasts and their potential impact on ADY production. In this study we analyzed the oxidative stress response in several non-Saccharomyces yeast species by measuring the activity of reactive oxygen species (ROS) scavenging enzymes, e.g., catalase and glutathione reductase, accumulation of protective metabolites, e.g., trehalose and reduced glutathione (GSH), and lipid and protein oxidation levels. Our data suggest that non-canonical regulation of glutathione and trehalose biosynthesis could cause poor fermentative performance after ADY production, as it corroborates the corrective effect of antioxidant treatments, during biomass propagation, with both pure chemicals and food-grade argan oil.

Targeting a Sirt5-Positive Subpopulation Overcomes Multidrug Resistance in Wild-Type Kras Colorectal Carcinomas

A major obstacle for successful management of patients with colorectal carcinoma (CRC) is resistance to anti-cancer cytotoxic treatments. Here, we identified a mechanism of multidrug resistance in wild-type Kras CRCs based on the survival of a cell subpopulation characterized by Sirt5 expression. Sirt5+ cells in wild-type Kras CRCs are resistant to either chemotherapeutic agents or cetuximab and serve as a reservoir for recurrence. Sirt5 demalonylates and inactivates succinate dehydrogenase complex subunit A (SDHA), leading to an accumulation of theoncometabolite succinate. Succinate binds to and activates a reactive oxygen species-scavenging enzyme, thioredoxin reductase 2 (TrxR2), to confer chemotherapy resistance. In contrast, Sirt5+ cells exhibit an elevated succinate-to-aKG ratio that inhibits aKG-dependent dioxygenases to maintain cetuximab resistance. Our findings suggest that Sirt5 inhibitors in combination with chemotherapeutic agents and/or cetuximab may represent atherapeutic strategy for CRC patients harboring wild-type Kras.

Alleviation of drought stress in pulse crops with ACC deaminase producing rhizobacteria isolated from acidic soil of Northeast India

The agricultural crops are often affected by the scarcity of fresh water. Seasonal drought is a major constraint on Northeast Indian agriculture. Almost 80% of the agricultural land in this region is acidic and facing severe drought during the winter period. Apart from classical breeding and transgenic approaches, the application of plant-growth-promoting bacteria (PGPB) is an alternative strategy for improving plant fitness under stressful conditions. The 1-aminocyclopropane-1-carboxylate (ACC) deaminase-producing PGPB offer drought stress tolerance by regulating plant ethylene levels. The aim of the present study was to evaluate the consortium effect of three ACC-deaminase producing rhizobacteria – Ochrobactrum pseudogrignonenseRJ12, Pseudomonas sp.RJ15 and Bacillus subtilisRJ46 on drought stress alleviation in Vigna mungo L. and Pisum sativum L. Consortium treatment significantly increase seed germination percentage, root length, shoot length, and dry weight of treated plants. An elevated production of reactive oxygen species scavenging enzymes and cellular osmolytes; higher leaf chlorophyll content; increase in relative water content and root recovery intension were observed after consortium treatment in comparison with the uninoculated plants under drought conditions. The consortium treatment decreased the ACC accumulation and down-regulated ACC-oxidase gene expression. This consortium could be an effective bio-formulator for crop health improvement in drought-affected acidic agricultural fields.

Dehydrins Impart Protection against Oxidative Stress in Transgenic Tobacco Plants.

Environmental stresses generate reactive oxygen species (ROS) which might be detrimental to the plants when produced in an uncontrolled way. However, the plants ameliorate such stresses by synthesizing antioxidants and enzymes responsible for the dismutation of ROS. Additionally, the dehydrins were also able to protect the inactivation of the enzyme lactate dehydrogenase against hydroxyl radicals (OH⋅) generated during Fenton’s reaction. SbDhn1 and SbDhn2 overexpressing transgenic tobacco plants were able to protect against oxidative damage. Transgenic tobacco lines showed better photosynthetic efficiency along with high chlorophyll content, soluble sugar and proline. However, the malonyl dialdehyde (MDA) content was significantly lower in transgenic lines. Experimental evidence demonstrates the protective effect of dehydrins on electron transport chain in isolated chloroplast upon methyl viologen (MV) treatment. The transgenic tobacco plants showed significantly lower superoxide radical generation () upon MV treatment. The accumulation of the H2O2 was also lower in the transgenic plants. Furthermore, in the transgenic plants the expression of ROS scavenging enzymes was higher compared to non-transformed (NT) or vector transformed (VT) plants. Taken together these data, during oxidative stress dehydrins function by scavenging the () directly and also by rendering protection to the enzymes responsible for the dismutation of () thereby significantly reducing the amount of hydrogen peroxides formed. Increase in proline content along with other antioxidants might also play a significant role in stress amelioration. Dehydrins thus function co-operatively with other protective mechanisms under oxidative stress conditions rendering protection in stress environment.

A Rice CPYC-Type Glutaredoxin OsGRX20 in Protection against Bacterial Blight, Methyl Viologen and Salt Stresses.

Glutaredoxins (GRXs) belong to the antioxidants involved in the cellular stress responses. In spite of the identification 48 GRX genes in rice genomes, the biological functions of most of them remain unknown. Especially, the biological roles of members of GRX family in disease resistance are still lacking. Our proteomic analysis found that OsGRX20 increased by 2.7-fold after infection by bacterial blight. In this study, we isolated and characterized the full-length nucleotide sequences of the rice OsGRX20 gene, which encodes a GRX family protein with CPFC active site of CPYC-type class. OsGRX20 protein was localized in nucleus and cytosol, and its transcripts were expressed predominantly in leaves. Several stress- and hormone-related motifs putatively acting as regulatory elements were found in the OsGRX20 promoter. Real-time quantitative PCR analysis indicated that OsGRX20 was expressed at a significantly higher level in leaves of a resistant or tolerant rice genotype, Yongjing 50A, than in a sensitive genotype, Xiushui 11, exposed to bacterial blight, methyl viologen, heat, and cold. Its expression could be induced by salt, PEG-6000, 2,4-D, salicylic acid, jasmonic acid, and abscisic acid treatments in Yongjing 50A. Overexpression of OsGRX20 in rice Xiushui 11 significantly enhanced its resistance to bacterial blight attack, and tolerance to methyl viologen and salt stresses. In contrast, interference of OsGRX20 in Yongjing 50A led to increased susceptibility to bacterial blight, methyl viologen and salt stresses. OsGRX20 restrained accumulation of superoxide radicals in aerial tissue during methyl viologen treatment. Consistently, alterations in OsGRX20 expression affect the ascorbate/dehydroascorbate ratio and the abundance of transcripts encoding four reactive oxygen species scavenging enzymes after methyl viologen-induced stress. Our results demonstrate that OsGRX20 functioned as a positive regulator in rice tolerance to multiple stresses, which may be of significant use in the genetic improvement of rice resistance.

Ameliorative Effects of Nitric Oxide on Oilseed Rape (Brassica napus L.) Under Water Stress

The ameliorative effects of nitric oxide on oilseed rape seedlings, Okapy cultivar, under drought condition were investigated. Water stress at 60 and 30% field capacity, increased lipid peroxidation and H2O2 content in oilseed rape leaves. Among the different concentrations (25, 50, 75 and 100 µM) of sodium nitroprusside used, spraying plants leaves with 25 µM sodium nitroprusside a NO donor, reduced the damaging effects of water stress which was reflected by a decrease in malondialdehyde and hydrogen peroxide content in leaves. Drought stress enhanced leaves superoxide dismutase, peroxidase and ascorbate peroxidase activities but decreased catalase activity. Sodium nitroprusside treatment (25 µM) had a positive effect on antioxidant enzymes under water stress. At higher sodium nitroprusside concentrations, its ameliorative effects on water stress were decreased and the oxidative damages to the leaves were sustained. The reduction in drought induced oxidative damages by NO in oilseed rape is most likely mediated by the NO ability to induce and increase the activity of reactive oxygen species scavenging enzymes.

Stress Resilience of Spermatozoa and Blood Mononuclear Cells without Prion Protein.

The cellular prion protein PrPC is highly expressed in neurons, but also present in non-neuronal tissues, including the testicles and spermatozoa. Most immune cells and their bone marrow precursors also express PrPC. Clearly, this protein operates in highly diverse cellular contexts. Investigations into putative stress-protective roles for PrPC have resulted in an array of functions, such as inhibition of apoptosis, stimulation of anti-oxidant enzymes, scavenging roles, and a role in nuclear DNA repair. We have studied stress resilience of spermatozoa and peripheral blood mononuclear cells (PBMCs) derived from non-transgenic goats that lack PrPC (PRNPTer/Ter) compared with cells from normal (PRNP+/+) goats. Spermatozoa were analyzed for freeze tolerance, DNA integrity, viability, motility, ATP levels, and acrosome intactness at rest and after acute stress, induced by Cu2+ ions, as well as levels of reactive oxygen species (ROS) after exposure to FeSO4 and H2O2. Surprisingly, PrPC-negative spermatozoa reacted similarly to normal spermatozoa in all read-outs. Moreover, in vitro exposure of PBMCs to Doxorubicin, H2O2 and methyl methanesulfonate (MMS), revealed no effect of PrPC on cellular survival or global accumulation of DNA damage. Similar results were obtained with human neuroblastoma (SH-SY5Y) cell lines stably expressing varying levels of PrPC. RNA sequencing of PBMCs (n = 8 of PRNP+/+ and PRNPTer/Ter) showed that basal level expression of genes encoding DNA repair enzymes, ROS scavenging, and antioxidant enzymes were unaffected by the absence of PrPC. Data presented here questions the in vitro cytoprotective roles previously attributed to PrPC, although not excluding such functions in other cell types or tissues during inflammatory stress.

Desiccation tolerance in bryophytes: the rehydration proteomes of Bryum argenteum provide insights into the resuscitation mechanism

Bryum argenteum Hedw. is a desiccation tolerant bryophyte and belongs to one of the most important components of the biological soil crusts (BSCs) found in the deserts of Central Asia. Limited information is available on rehydration-responsive proteins in desiccation tolerant plants. As a complement to our previous research analyzing the rehydration transcriptome, we present a parallel quantitative proteomic effort to study rehydration-responsive proteins. Bryophyte gametophores were desiccated (Dry) and rehydrated for 2 h (R2) and 24 h (R24). Proteins from Dry, R2 and R24 gametophores were labeled by isobaric tags for relative and absolute quantitation (iTRAQ) to determine the relative abundance of rehydration-responsive proteins. A total of 5503 non-redundant protein sequences were identified and 4772 (86.7%) protein sequences were annotated using Gene Ontology (GO) terms and Pfam classifications. Upon rehydration 239 proteins were elevated and 461 proteins were reduced as compared to the desiccated protein sample. Differentially up-regulated proteins were classified into a number of categories including reactive oxygen species scavenging enzymes, detoxifying enzymes, Late Embryogenesis Abundant (LEA) proteins, heat shock proteins, proteasome components and proteases, and photosynthesis and translation related proteins. Furthermore, the results of the correlation between transcriptome and proteome revealed the discordant changes in the expression between protein and mRNA.

ROS scavenging Mn3O4 nanozymes for in vivo anti-inflammation.

Reactive oxygen species (ROS)-induced oxidative stress is linked to various diseases, including cardiovascular disease and cancer. Though highly efficient natural ROS scavenging enzymes have been evolved, they are sensitive to environmental conditions and hard to mass-produce. Therefore, enormous efforts have been devoted to developing artificial enzymes with ROS scavenging activities. Among them, ROS scavenging nanozymes have recently attracted great interest owing to their enhanced stability, multi-functionality, and tunable activity. It has been implicated that Mn-contained nanozymes would possess efficient ROS scavenging activities, however only a few such nanozymes have been reported. To fill this gap, herein we demonstrated that Mn3O4 nanoparticles (NPs) possessed multiple enzyme mimicking activities (i.e., superoxide dismutase and catalase mimicking activities as well as hydroxyl radical scavenging activity). The Mn3O4 nanozymes therefore significantly scavenged superoxide radical as well as hydrogen peroxide and hydroxyl radical. Moreover, they were not only more stable than the corresponding natural enzymes but also superior to CeO2 nanozymes in terms of ROS elimination. We showed that the Mn3O4 NPs not only exhibited excellent ROS removal efficacy in vitro but also effectively protected live mice from ROS-induced ear-inflammation in vivo. These results indicated that Mn3O4 nanozymes are promising therapeutic nanomedicine for treating ROS-related diseases.

Constitutive expression of CaHSP22.5 enhances chilling tolerance in transgenic tobacco by promoting the activity of antioxidative enzymes.

Chilling stress limits the productivity and geographical distribution of many organisms throughout the world. In plants, the small heat shock proteins (sHSPs) belong to a group of proteins known as chaperones. The sweet pepper (Capsicum annuum L.) cDNA clone CaHSP22.5, which encodes an endoplasmic reticulum-located sHSP (ER-sHSP), was isolated and introduced into tobacco (Nicotiana tabacum L.) plants and Escherichia coli. The performance index and the maximal efficiency of PSII photochemistry (Fv/Fm) were higher and the accumulation of H2O2 and superoxide radicals (O2-) was lower in the transgenic lines than in the untransformed plants under chilling stress, which suggested that CaHSP22.5 accumulation enhanced photochemical activity and oxidation resistance. However, purified CaHSP22.5 could not directly reduce the contents of H2O2 and O2- in vitro. Additionally, heterologously expressed recombinant CaHSP22.5 enhanced E. coli viability under oxidative stress, helping to elucidate the cellular antioxidant function of CaHSP22.5 in vivo. At the same time, antioxidant enzyme activity was higher, which was consistent with the lower relative electrolyte conductivity and malondialdehyde contents of the transgenic lines compared with the wild-type. Furthermore, constitutive expression of CaHSP22.5 decreased the expression of other endoplasmic reticulum molecular chaperones, which indicated that the constitutive expression of ER-sHSP alleviated endoplasmic reticulum stress caused by chilling stress in plants. We hypothesise that CaHSP22.5 stabilises unfolded proteins as a chaperone and increases the activity of reactive oxygen species-scavenging enzymes to avoid oxidation damage under chilling stress, thereby suggesting that CaHSP22.5 could be useful for improving the tolerance of chilling-sensitive plant types.

METALLOTHIONEIN genes encoding ROS scavenging enzymes are down-regulated in the root cortex during inducible aerenchyma formation in rice

ABSTRACTUnder waterlogged conditions, roots of gramineous plants form lysigenous aerenchyma (internal gas spaces) by inducing the death of cortical cells. Rice (Oryza sativa) roots induce aerenchyma formation through ethylene- and reactive oxygen species (ROS)-mediated signaling. Metallothionein (MT) is a small, cysteine-rich protein that acts as a ROS scavenger. In rice roots, the expression of MT1a, MT1b, MT1c and MT1Ld were higher than those of the other MT genes. In the root cortex, where aerenchyma forms exclusively, the expression of MT1a, MT1b and MT1Ld was reduced prior to aerenchyma formation. These findings suggest that ROS accumulation in the cortex, which is aided by downregulation of MT1 genes, is needed for aerenchyma formation in rice roots.

Hydrogen Peroxide Response in Leaves of Poplar (Populus simonii × Populus nigra) Revealed from Physiological and Proteomic Analyses.

Hydrogen peroxide (H2O2) is one of the most abundant reactive oxygen species (ROS), which plays dual roles as a toxic byproduct of cell metabolism and a regulatory signal molecule in plant development and stress response. Populus simonii × Populus nigra is an important cultivated forest species with resistance to cold, drought, insect and disease, and also a key model plant for forest genetic engineering. In this study, H2O2 response in P. simonii × P. nigra leaves was investigated using physiological and proteomics approaches. The seedlings of 50-day-old P. simonii × P. nigra under H2O2 stress exhibited stressful phenotypes, such as increase of in vivo H2O2 content, decrease of photosynthetic rate, elevated osmolytes, antioxidant accumulation, as well as increased activities of several ROS scavenging enzymes. Besides, 81 H2O2-responsive proteins were identified in the poplar leaves. The diverse abundant patterns of these proteins highlight the H2O2-responsive pathways in leaves, including 14-3-3 protein and nucleoside diphosphate kinase (NDPK)-mediated signaling, modulation of thylakoid membrane structure, enhancement of various ROS scavenging pathways, decrease of photosynthesis, dynamics of proteins conformation, and changes in carbohydrate and other metabolisms. This study provides valuable information for understanding H2O2-responsive mechanisms in leaves of P. simonii × P. nigra.

Response of ROS-Scavenging Systems to Salinity Stress in Two Different Wheat (Triticum aestivum L.) Cultivars

Salinity leads to oxidative stress in plant cells due to increased production of reactive oxygen species. The response of two wheat (Triticum aestivum L.) cultivars, salt sensitive (‘Darab2’) and salt-tolerant (‘Arta’) were studied to salinity-induced oxidative stress (0, 75 and 150 mM NaCl). Increasing of lipid peroxidation caused oxidative stress in both sensitive and tolerant cultivars. The result showed that reactive oxygen species (ROS) viz., superoxide and hydrogen peroxide increased in leaves of ‘Darab2’ under salinity stress. Under salinity stress, the salt-tolerant cv. ‘Arta’ showed higher activity of the ROS scavenging enzymes like ascorbate peroxidase and peroxidases than ‘Darab2’. Furthermore, in sensitive cv. ‘Darab2’ the activities of these enzymes in leaves were unable to prevent the scavenging of H2O2. Unlike ‘Arta’, there were no significant differences in superoxide dismutases and glutathione reductase activities in sensitive cv. ‘Darab2’ under salinity stress. The amount of reduced glutathione, reduced/oxidized glutathione ratio in leaves of ‘Darab2’ was lower than ‘Arta’ under saline conditions. It seems that in salt tolerant cultivars like ‘Arta’, both enzymatic and non-enzymatic ROS scavenging machineries is critical point to overcome salinity-induced oxidative stress.

OsDSR-1, a calmodulin-like gene, improves drought tolerance through scavenging of reactive oxygen species in rice (Oryza sativa L.)

Calmodulin-like (CML) genes regulate plant growth, development, and responses to abiotic stresses such as salinity and drought. Many genes encoding CML proteins have been identified from rice (Oryza sativa), but their functions remain largely unknown. Our characterization of one putative CML gene, OsDSR-1 (O. sativa Drought Stress Response-1), showed that its protein binds Ca2+ and displays Ca2+-dependent conformational changes. In contrast to wild-type (WT) and OsDSR-1-RNA interference (OsDSR-1-Ri) plants, transgenic rice plants that overexpress OsDSR-1 were significantly more drought tolerant and had increased sensitivity to abscisic acid. Furthermore, their concentrations of free proline and soluble sugars and the activities of reactive oxygen species-scavenging enzymes as well as the transcript levels of many ROS-scavenging and stress-related genes were significantly enhanced under drought stress. Much less hydrogen peroxide and malondialdehyde accumulated in OsDSR-1-overexpressing (OsDSR-1-OE) plants than in either the Ri or WT plants. All of these results suggest that OsDSR-1 plays important roles in conferring tolerance to drought in rice by decreasing the occurrence of oxidative damage.

The influence of glyphosate on carotenoid pigments, reactive oxygen species scavenging enzymes and secondary stress metabolites within leaf tissue of three Acer species

Glyphosate is a commonly used systemic herbicide in urban landscapes. Incidental spray drift and/or ground water contamination potentially represents an under-estimated problem that can detrimentally impact on the biology of trees. There are few studies that have investigated differences in tolerance of urban trees to glyphosate-induced oxidative stress. Aims of this study were to quantify the influence of a range of pigments carotenoids (lutein:β-carotene: neoxanthin:α-carotene, xanthophyll-cycle pigments (zeaxanthin:antheraxanthin: violaxanthin)), reactive oxygen species (ROS) scavenging enzymes (superoxide dismutase, calatase) and the stress metabolite proline within leaf tissue of three Acer species (Acer pseudoplatanus (sycamore), A. campestre (Field maple) and A. palmatum ‘Atropurpurea’ (Japanese maple)) widely planted into urban landscapes to identify the role these compounds play in protecting foliar tissue against glyphosate. Tolerance to glyphosate damage based on reductions in leaf chlorophyll content as a measure of leaf necrosis/chlorosis was in the order Acer pseudoplatanus>A. campestre>A. palmatum ‘Atropurpurea’. Quantitative analysis of carotenoid pigments, ROS scavenging enzymes and the stress metabolite proline demonstrated significant differences between the three Acer species. Highest concentrations of these compounds within leaf tissue was in the order Acer pseudoplatanus>A. campestre>A. palmatum ‘Atropurpurea’ which reflected order of tolerance based on leaf chlorophyll content loss. Results of this study indicate Acer species possess a suite of stress protective compounds with leaf tissue that potentially confer differing degrees of glyphosate tolerance. Quantification of the formation, concentration and fate of these enzymes and pigments may prove helpful in selecting trees with in-built capacity to tolerate glyphosate induced oxidative stress and allow professionals to make informed decisions regarding tree selection in urban areas where glyphosate is routinely used.