Reactive Oxygen Species Scavenging Enzymes Research Articles

Osmotin-expressing transgenic tea plants have improved stress tolerance and are of higher quality

Drought is a major stress that affects the yield and quality of tea, a widely consumed beverage crop grown in more than 20 countries of the world. Therefore, osmotin gene-expressing transgenic tea plants produced using earlier optimized conditions were evaluated for their tolerance of drought stress and their quality. Improved tolerance of polyethylene glycol-induced water stress and faster recovery from stress were evident in transgenic lines compared with the normal phenotype. Significant improvements in growth under in-vitro conditions were also observed. Besides enhanced reactive oxygen species-scavenging enzyme activity, the transgenic lines contained significantly higher levels of flavan-3-ols and caffeine, key compounds that govern quality and commercial yield of the beverage. The selected transgenic lines have the potential to meet the demands of the tea industry for stress-tolerant plants with higher yield and quality. These traits of the transgenic lines can be effectively maintained for generations because tea is commercially cultivated through vegetative propagation only.

Phosphorus Improves Arsenic Phytoremediation by Anadenanthera Peregrina by Alleviating Induced Oxidative Stress

Due to similarities in their chemical behaviors, studies examining interactions between arsenic (As)—in special arsenate—and phosphorus (P) are important for better understanding arsenate uptake, toxicity, and accumulation in plants. We evaluated the effects of phosphate addition on plant biomass and on arsenate and phosphate uptake by Anadenanthera peregrina, an important Brazilian savanna legume. Plants were grown for 35 days in substrates that received combinations of 0, 10, 50, and 100 mg kg−1 arsenate and 0, 200, and 400 mg kg−1 phosphate. The addition of P increased the arsenic-phytoremediation capacity of A. peregrina by increasing As accumulation, while also alleviating As-induced oxidative stress. Arsenate phytotoxicity in A. peregrina is due to lipid peroxidation, but not hydrogen peroxide accumulation. Added P also increased the activity of important reactive oxygen species-scavenging enzymes (catalase and ascorbate peroxidase) that help prevent lipid peroxidation in leaves. Our findings suggest that applying P represents a feasible strategy for more efficient As phytoremediation using A. peregrina.

Dry up and survive: the role of antioxidant defences in anhydrobiotic organisms

Although the evolution of life has turned oxygen into a vital chemical for aerobic organisms, this element can also have deleterious effects on living systems through the production of oxidative stress. This is a process resulting from an imbalance between the excessive production of Reactive Oxygen Species (ROS) and the limited action of antioxidant defences. It is a particularly harmful health risk factor, involved in the development of several chronic human pathologies and believed to play a major role in the ageing process. Consequently aerobic metabolism needs a stringent control of ROS. Water too is essential for life, but some organisms widespread throughout nature have the ability to survive complete desiccation by entering an anhydrobiotic state. The loss of water induces changes in metabolism, cell membrane organization, and molecular composition. In the anhydrobiotic state, high temperatures, high humidity, light exposure, and high oxygen partial pressure negatively affect organism survival and directly influence the time required to reactivate the metabolism after a period of desiccation. These abiotic factors induce damages that are accumulated in proportion to the time spent in the desiccated state, potentially leading to organism death. Oxidative stress seems to be one of the most deleterious damages due to water depletion, therefore anhydrobiosis also needs a stringent control of ROS production. Anhydrobiotic organisms seem to apply two main strategies to cope with the danger of oxygen toxicity, namely an increased efficiency of antioxidant defences and a metabolic control of both energy-production and energy-consuming processes. Experimental studies provide evidence that antioxidant defences such as ROS scavenging enzymes ( e.g. peroxidases, catalases, superoxide dismutase, glutathione peroxidases) and other molecules ( e.g. glutathione, carotenoids, vitamins C and E) represent a key group of molecules required for desiccation tolerance in anhydrobiotic organisms. The action of these molecules emphasises the need for redox balancing in anhydrobiotic organisms including tardigrades and chironomid larvae.

A Fogging System Improves Antioxidative Defense Responses and Productivity in Tomato

Crops cultivated during summer in greenhouses and screen-covered structures (screenhouses) are negatively affected by stressful temperatures and vapor pressure deficit (VPD), which in turn influence yield and product quality. Fogging systems have been proposed as cooling methods to mitigate the adverse effects of high evaporation and excess temperatures in greenhouses. To evaluate the possible action of the fogging system on antioxidant response in cherry tomato (Solanum lycopersicum) fruit production, we studied the behavior of reactive oxygen species (ROS) scavenger enzymes such as superoxide dismutase, catalase, guaiacol peroxidase, enzymes involved in the ascorbate-glutathione cycle (Halliwell-Asada cycle), and compounds with antioxidant functions such as ascorbate, glutathione, proline, and polyamines. Fogging-screenhouse treatments, SF (a fogging system inside the screenhouse) and SFS (fogging system with a plastic sheeting, to maintain the microclimate created by the fogging system in the screenhouse) showed the best performance in terms of radiation with a percentage reduction of incident radiation on the crop of 18% and 37% and a mean reduction of maximum VPD values of 0.4 and 0.2 kPa, respectively, compared with the unfogging treatment (S). These improved environmental conditions, besides promoting the highest activities of ROS-scavenging enzymes and Halliwell-Asada cycle, the redox state of the ascorbate, and a low proline:free putrescine ratio, would explain the increase in commercial weight of fruit by 21% and 17% in SF and SFS, respectively, with respect to S.

Arabidopsis enhanced drought tolerance1/HOMEODOMAIN GLABROUS11 confers drought tolerance in transgenic rice without yield penalty.

Enhancing drought tolerance without yield decrease has been a great challenge in crop improvement. Here, we report the Arabidopsis (Arabidopsis thaliana) homodomain-leucine zipper transcription factor Enhanced Drought Tolerance/HOMEODOMAIN GLABROUS11 (EDT1/HDG11) was able to confer drought tolerance and increase grain yield in transgenic rice (Oryza sativa) plants. The improved drought tolerance was associated with a more extensive root system, reduced stomatal density, and higher water use efficiency. The transgenic rice plants also had higher levels of abscisic acid, proline, soluble sugar, and reactive oxygen species-scavenging enzyme activities during stress treatments. The increased grain yield of the transgenic rice was contributed by improved seed setting, larger panicle, and more tillers as well as increased photosynthetic capacity. Digital gene expression analysis indicated that AtEDT1/HDG11 had a significant influence on gene expression profile in rice, which was consistent with the observed phenotypes of transgenic rice plants. Our study shows that AtEDT1/HDG11 can improve both stress tolerance and grain yield in rice, demonstrating the efficacy of AtEDT1/HDG11 in crop improvement.

Accumulation and scavenging of reactive oxygen species and nitric oxide correlate with stigma maturation and pollen–stigma interaction in sunflower

During the course of stigma development in sunflower (bud, staminate and pistillate stages), correlation is evident among the accumulation of reactive oxygen species (ROS), nitric oxide (NO), and the activities of ROS scavenging enzymes [superoxide dismutase (SOD) and peroxidase (POD)]. Confocal image analysis shows a gradual increase in ROS and NO accumulation in the stigmatic papillae, which may provide immunity to the developing stigma and function as signalling molecules. A novel, NO-specific probe (MNIP-Cu) has been employed for the detection and quantification of intracellular NO. Mn-SOD (mitochondrial) and Cu/Zn-SOD (cytoplasmic) exhibit differential expression during the staminate stage of stigma development. An increase in total SOD activity at the staminate stage is followed by a peak of POD activity during pistillate stage, thereby indicating the sequential action of the two enzymes in scavenging ROS. An increase in the number of POD isoforms is observed with the passage of stigma development (from three at bud stage to seven at pistillate stage), and two POD isoforms are unique to pistillate stage, thereby highlighting their role in ROS scavenging mechanism. ROS and NO accumulation exhibit reverse trends during pollen–stigma interaction.

Kinetics of metabolism in sugarcane (Saccharum officinarum L.) under heat stress

A study was conducted to determine the kinetics of metabolism of sugarcane in vivo under heat stress. 30-days-old sugarcane settlings (Co 86032) were subjected to critical temperature (40 °C) for 5, 10, 15, 20, 25 and 30 h. The metabolic changes in terms of total phenolics, total sugars, proline, glycinebetaine and reactive oxygen species (ROS) scavenging enzymes activity and isozyme pattern were studied at different temperatures. A linear accumulation of soluble sugars, free proline and glycinebetaine (up to 25 h of heat stress treatment) was evident in sugarcane sprouts due to heat stress, although none of these metabolites accumulated under control conditions suggesting their role in osmotic adjustment and thereby in protecting cells from heat damage for short heat stress conditions. Heat stress induced increase in total phenolics content of settlings (44.5–128.5 μg g−1 FW) and callus (37.5–105.1 μg g−1 FW) with the gradual increase of sampling timing (5–25 h) might play a role in the prevention of stress-induced oxidative damage and maintenance of osmotic balance. High temperature stress enhanced the activity of antioxidant enzymes up to 15 h of 40 °C temperature stress and after wards declined. Higher degree of expression of peroxidase and superoxide dismutase isoform and their activities lead to protection of cells from oxidative damage under heat stress suggesting that the plants have developed enzymatic control of scavenge ROS under short term stress.

Zymogram profiling of superoxide dismutase and catalase activities allows Saccharomyces and non-Saccharomyces species differentiation and correlates to their fermentation performance

Aerobic organisms have devised several enzymatic and non-enzymatic antioxidant defenses to deal with reactive oxygen species (ROS) produced by cellular metabolism. To combat such stress, cells induce ROS scavenging enzymes such as catalase, peroxidase, superoxide dismutase (SOD) and glutathione reductase. In the present research, we have used a double staining technique of SOD and catalase enzymes in the same polyacrylamide gel to analyze the different antioxidant enzymatic activities and protein isoforms present in Saccharomyces and non-Saccharomyces yeast species. Moreover, we used a technique to differentially detect Sod1p and Sod2p on gel by immersion in NaCN, which specifically inhibits the Sod1p isoform. We observed unique SOD and catalase zymogram profiles for all the analyzed yeasts and we propose this technique as a new approach for Saccharomyces and non-Saccharomyces yeast strains differentiation. In addition, we observed functional correlations between SOD and catalase enzyme activities, accumulation of essential metabolites, such as glutathione and trehalose, and the fermentative performance of different yeasts strains with industrial relevance.

The Effect of Blue-light-emitting Diodes on Antioxidant Properties and Resistance to Botrytis cinerea in Tomato

In higher plants, blue-light is mainly perceived by cryptochromes and phototropins, which subsequently orchestrates phototropism, chloroplast relocation, stomatal opening, rapid inhibition of hypocotyl elongation and leaf expansion. Blue-light signaling is also known to mediate the plant responses to biotic stresses, but relevant mechanisms are largely unknown. Here, we demonstrated that blue LED (Light Emitting Diode)-driven inhibition of gray mold disease was highly correlated with the increases in cellular protectants like proline, antioxidants and ROS (Reactive Oxygen Species) scavenger activities. After twenty one days of exposure to various wavelengths of LED lights, blue-LED treated tomato displayed significant increases in proline accumulation in the leaves and stems, whereas red- and green-LED treated tomato exhibited the lower proline contents. Similarly, the blue-LED treatment increased the amount of polyphenolic compounds in tomatoes, compared to other wavelength of LED lights. The activities of various ROS (Reactive Oxygen Species) scavenging enzymes were also slightly increased under the blue-LED lighted conditions. Finally, blue-LED significantly suppressed symptom development of tomato infected by gray mold. Combined results suggest that blue LED light inhibits the development of gray mold disease, which can be mechanistically explained by the enhanced proline accumulation and antioxidative processes at least in partial.

Loss-of-function mutation of EIN2 in Arabidopsis exaggerates oxidative stress induced by salinity

Accumulation of reactive oxygen species (ROS) causes oxidative stress under adverse environmental conditions, such as salinity. Ethylene decreases accumulation of ROS induced by salinity, but the mechanism is still unclear. To examine the interactions between salinity and ROS accumulation and the possible role of ethylene metabolism in regulation, we used mutant ein2-5 in Arabidopsis with loss of function in EIN2. The mutant is compared to the wild-type Col-0, completely insensitivity to ethylene at the morphological, physiological and molecular levels. The oxidative responses of the wild type and mutant to salinity were compared. Loss-of-function of EIN2 enhanced sensitivity to salinity, implying that EIN2 is required for plant response to salinity. Furthermore, salinity resulted in accumulation of large amounts of ROS in ein2-5 seedlings when compared with Col-0, suggesting that the loss-of-function of EIN2 exaggerates oxidative stress induced by salinity. Activities of the antioxidant enzymes SOD, POD and CAT decreased significantly in ein2-5 under salinity when compared with Col-0 plants. The expression profiles of the genes Fe-SOD, PODs and CAT1, which code for ROS scavenging enzymes were severely decreased in ein2-5 under salinity compared with Col-0, suggesting that EIN2 was involved in regulating expression of these genes. Taken together, our results demonstrate that loss-of-function of EIN2 increased oxidative stress induced by salinity and that EIN2 is involved in modulating ROS accumulation, at least in part, by decreasing activities of ROS-scavenging enzymes.

Abstract 18268: Jund is a Critical Modulator of Oxidative Stress-induced Vascular Aging

Background. Reactive oxygen species (ROS) are the major determinant of vascular aging. JunD, a member of the activated protein 1 (AP-1) family of transcription factors, promotes the intracellular redox homeostasis. The present study investigates the role of JunD in aging-associated endothelial dysfunction. Methods and Results . Blunted vasorelaxation was found in young and old JunD -/- mice as compared with age-matched WT animals [maximal relaxations were 51±1.5 %vs 83±4.8 (young) and 34±2.3 vs 58±2.4 (old) for JunD -/- and WT mice, respectively, n=6-8, p<0.05 vs age-matched group]. ROS scavengers superoxide dismutase (PEG-SOD) and catalase restored endothelial function. Accordingly, JunD-/- mice displayed not only an age-independent decline of NO release but also increased superoxide and peroxynitrite levels in endothelial cells assessed by chemoluminescence. Nitrotyrosine residues, identified by immunofluorescence, were also elevated. ROS scavenging enzymes manganese (Mn) and extracellular (ec) SOD, aldehyde dehydrogenase-2 and glutathione peroxidase-1(GPx-1) were downregulated in JunD -/- mice. In contrast, NADPH oxidase subunit p47phox was upregulated. Furthermore, in JunD-/- mice eNOS expression and eNOS activating Ser-1177 phosphorylation were reduced. Interestingly, age-induced endothelial dysfunction was paralleled by a significant reduction of JunD protein expression in old as compared with young WT mice. In human aortic endothelial cells, siRNA-mediated JunD knockdown elicited a similar impairment of NO/O2- production, which was abolished by simultaneous silencing of p47phox. Notably, JunD mRNA expression was reduced in peripheral monocytes from old compared with young healthy blood donors (63.30 ± 6.0 vs 113.9 ± 6.7, respectively, values normalized to TBP mRNA, n=6; p< 0.0004), and correlated with gene expression of MnSOD (r=0.65, p<0.05). Conclusions. Aging-induced oxidative stress and endothelial dysfunction were markedly accelerated in JunD -/- mice compared with age-matched WT littermates. JunD may be a crucial modulator of ROS-mediated vascular aging, representing a novel molecular target to slow down this process.

Molecular Basis of Neocytolysis.

Abstract 2093The principal function of red blood cells (RBCs) is to deliver oxygen via hemoglobin resulting in the formation of reactive oxygen species (ROS), which mandates the existence of an ROS protective mechanism. Hypoxia increases RBC mass by increasing hypoxia-inducible factors (HIFs) levels. This is mainly mediated by HIFs-regulated erythropoietin. Upon return to normoxia, RBC mass is overcorrected by the destruction of newly formed RBCs, a process termed neocytolysis. Neocytolysis was first described in astronauts and people descending from high-altitude, and likely accounts for the rapid transition from polycythemia to anemia in neonates upon leaving the fetal hypoxic environment. The molecular mechanism of neocytolysis has not yet been elucidated. Reticulocytes newly released from the marrow contain ribosomes and mitochondria which are removed by multiple mechanisms, including mitochondrial loss by autophagy regulated by HIFs-controlled Bnip3L gene. FOXO3a is a HIF-regulated transcription factor that controls ROS-scavenging enzymes. Mature RBCs cannot respond to rapid changes of ROS levels because of their inability to produce new proteins. We hypothesized that after hypoxic exposure and return to normoxia, there is an increase in reticulocytes' ROS (mediated by Bnip3L), causing preferential destruction of the hypoxia-born young RBCs having decreased activity of FOXO3a-controlled ROS-scavenging enzymes.We developed a mouse model of neocytolysis that replicates RBC changes observed in humans to test our hypothesis, with awareness that RBCs live ∼120 days in humans and ∼45 days in mice. C57/BL6 mice were maintained at 12% oxygen (equivalent to 4500 m altitude) for 10 days followed by return to ambient air. We measured the following parameters: hematocrit (hct), reticulocyte count, RBC survival, mitochondrial mass, mRNA and the activity of ROS-scavenging enzymes, Bnip3L and FOXO3a mRNA, and ROS content in peripheral blood cells before and after hypoxic exposure.Hypoxic exposure increased hct by 22%; upon return to normoxia, hct reached normal levels at post-hypoxia days (PHD) 4–7, then continued to decrease by 28% at PHD 7–10, while plasma volume did not significantly change until its decrease at PHD 10 (p=0.049). Reticulocyte count increased by 35% following hypoxia, then decreased by 33% at PHD 4 compared to pre-hypoxic levels. Reticulocytes recovered by 50% by PHD 7, then normalized at PHD 14. To measure RBCs survival, we labeled them with biotin prior to hypoxic exposure and found preferential destruction of newly formed RBCs in the initial phase of normoxic return. This was accompanied by a dramatic increase of ROS level at PHD 0 and PHD 4 confined only to RBCs (and preferentially to young RBCs, i.e. 2.6 fold higher at PHD 4 in CD71+/TER119+ compared to CD71−/TER119+ in older RBCs) but not to platelets, neutrophils, B and T cells, or monocytes. We demonstrated that the ROS changes were accompanied by a commensurate increase of mitochondrial mass that was limited to reticulocytes; i.e. mitochondrial mass increased in reticulocytes by 40%, with an inverse relation to reticulocytes’ Bnip3L transcript levels (reduced by 35%). Furthermore, we show the transcripts and activity of FOXO3a-regulated ROS scavenging enzyme catalase were reduced at PHD 0 and PHD 4 by 30% and recovered at PHD 10, accompanied by commensurate changes in FOXO3a mRNA. However, there were no similar changes in glutathione peroxidase and superoxide dismutase. These data demonstrate that the increase in ROS is due to both excessive generation in mitochondria and insufficient scavenging due to a decrease in catalase activity.We conclude that there are three different phases in the response of RBC mass to transient hypoxia: 1) Hypoxia increases erythropoiesis, resulting in polycythemia; 2) Upon return to normoxia, the increased RBC mass is overcorrected below the initial levels by neocytolysis; 3) After 10–14 days, RBC mass normalizes. We demonstrate that neocytolysis is mediated by ROS in reticulocytes, with increased mitochondrial mass due to downregulation of Bnip3L. These increased ROS cannot be scavenged by young RBCs with decreased catalase activity. These two processes lead in concert to neocytolysis. These studies reveal a novel role for mitochondria-derived ROS in the regulation of red cell mass. Disclosures:No relevant conflicts of interest to declare.

Transcriptional profiling reveals sexual differences of the leaf transcriptomes in response to drought stress in Populus yunnanensis

Populus yunnanensis Dode., a native dioecious woody plant species in Southwest China, plays an important role in commercial forestry and environmental protection. In natural habitats, female P. yunnanensis trees are extremely rare while males are dominant in population. Our previous physiological studies in the species have revealed sex-dependent difference in response to drought stress, and females suffer greater negative effects than males. However, the molecular basis of sex-related differences during drought stress has been poorly characterized. We use the Illumina-Solexa platform to sequence the leaf transcriptomes derived from male and female P. yunnanensis trees grown in normal condition and drought stress. In total, 22,235 transcripts were identified in this study and 6039 genes were differentially expressed (DEGs) during drought stress. Majority of the DEGs were identified in males (92%, 5539); thus, males had greater remodeling of the leaf transcriptome in response to drought compared with females. Furthermore, many genes involved in hormone biosynthesis, photosynthesis and reactive oxygen species (ROS) scavenging enzyme system had more transcript changes in males than in females during drought stress, while these genes exhibited higher transcript alteration in females than in males in normal condition. Quantitative reverse transcriptase-polymerase chain reaction (qRT-PCR) analysis of 15 selected genes suggested that during drought treatment the up-regulated DEGs had a quicker increment in their transcript abundances in females than that in males. The sexual differences of gene transcription coincide with the sexual different adaptation of P. yunnanensis in the present natural habitats.

Superoxide dismutase induces G1‐phase cell cycle arrest by down‐regulated expression of Cdk‐2 and cyclin‐E in murine sarcoma S180 tumor cells

As an efficient reactive oxygen species-scavenging enzyme, superoxide dismutase (SOD) has been shown to inhibit tumor growth and interfere with motility and invasiveness of cancer cells. In this study, the molecular mechanisms of cell cycle arrest when S180 tumor cells were exposed to high levels of SOD were investigated. Here, both murine sarcoma S180 tumor cells and NIH-3T3 mouse fibroblasts were respectively treated with varying concentrations of Cu/Zn-SOD for 24, 48 and 72 h to determine optimal dose of SOD, which was a concentration of 800 U/ml SOD for 48 h. It is found that SOD induced S180 cell cycle arrest at G1-phase with decreasing level of superoxide production, whereas SOD had less effect on proliferation of NIH-3T3 cells. Moreover, the expression rate of Proliferating Cell Nuclear Antigen (PCNA) in S180 tumor cells was suppressed after SOD treatment, which indicated the inhibition of DNA synthesis in S180 cells. Besides, there were significant down-regulations of cyclin-E and Cdk-2 in S180 cells after SOD treatment, which contributed to the blockage of G1/S transition in S180 cell cycle. Together, our data confirmed that SOD could notably inhibit proliferation of S180 tumor cell and induce cell cycle arrest at G1-phase by down-regulating expressions of cyclin-E and Cdk-2.

Physiological and biochemical response to photooxidative stress of the fundamental citrus species

Despite the economic importance of citrus, insights on the genetic response to stress are scarce. The aim of the present study was to compare fundamental citrus species for their response to photooxidative stress. The experiment was conducted under orchard conditions on three fundamental citrus species C. medica L., C. reticulata Blanco and C. maxima (Burm.) Merr., and on Fortunella japonica (Thunb.) Swing. We examined their respective net photosynthesis (Pnet), stomatal conductance (Gs) and chlorophyll fluorescence (Fv/Fm) on sun-acclimated leaves and shade-acclimated leaves returned under natural sunlight irradiance. To compare the respective response mechanism, we analyzed changes in oxidative status (hydrogen peroxide (H2O2) and malondialdehyde (MDA)), reactive oxygen species (ROS)-scavenging enzymes (superoxide dismutase (SOD), catalase, ascorbate peroxidase), recycling enzymes (monodehydroascorbate reductase, dehydroascorbate reductase and glutathione reductase) and antioxidant metabolites (ascorbate and glutathione). Kumquat and pummelo exposed lower down-regulation and full recovery of photosynthetic parameters, lower accumulation of oxidized compounds associated with greater production of reduced glutathione (Gsh) and enhanced activity of the three ROS scavenging enzymes, especially SOD. Citron and mandarin showed a marked decrease and incomplete recovery in photosynthetic performance, mainly in Pnet and Fv/Fm, larger accumulation of oxidative parameters, slighter induction of antioxidant enzymes and down-regulation of reduced ascorbate (Asa) and Gsh synthesis. These results suggest that kumquat and pummelo have a greater tolerance to photooxidative stress than citron and mandarin.

Cinnamic acid induced changes in reactive oxygen species scavenging enzymes and protein profile in maize (Zea mays L.) plants grown under salt stress

Plant growth and development are greatly affected due to changes in environmental conditions and become a serious challenge to scientific people. Therefore, present study was conducted to determine the role of secondary metabolites on the growth and development of maize under abiotic stress conditions. Cinnamic acid (CA) is one of the basic phenylpropanoid with antioxidant activity, produced by plants in response to stressful conditions. Response of maize seeds to the presoaking treatment with 0.5mM CA was studied under different concentrations of NaCl stress. Exogenous CA increased growth characteristics in saline and non-saline conditions, while effects of CA were more significant under saline conditions in comparison to non-saline conditions in maize plants. CA also reduced oxidative damage through the induction of ROS scavenging enzymes such as supperoxide dismutase (SOD) (EC 1.15.1.1), peroxidase (POD) (EC 1.11.1.7), while the activity of enzyme catalase (CAT) (EC 1.11.1.6) was decreased. The content of malondialdehyde (MDA) was reduced significantly in maize leaf under CA treatment. Changes in protein banding patterns in the maize leaves showed a wide variation in response to NaCl-stress, while in the presence of CA salt-induced expression of polypeptides was reduced significantly. Present study clearly reports the alleviative effects of CA in response to salinity stress on growth, metabolic activity and changes in protein profile of 21days old maize plants.

Defective root growth triggered by oxidative stress is controlled through the expression of cell cycle-related genes

Reactive oxygen species (ROS) have many functions in aerobic organisms. High levels of ROS can have a negative impact on plant cells leading to senescence and cell death. ROS accumulates in cells subjected to environmental stress and induces a cellular response to this external stimulus. To protect cells from the negative impacts of excess ROS, plants also possess a ROS detoxifying system to maintain normal ROS levels. The regulation of ROS levels is particularly important as ROS also functions as an important signal molecule and can regulate plant growth by modulating gene expression. Despite the functional importance of ROS signaling, little is known about the molecular mechanisms involved in the regulation of gene expression through ROS. Therefore, the present study investigated the effect of hydrogen peroxide (H2O2), a ROS compound, on cell cycle-related gene expression. Gene expression analyses coupled with microdissected sections of the developmental zone of Arabidopsis root tips revealed that H2O2 affects the expression of cell cycle-related genes. Additionally, ROS scavenging enzymes were found to play an important role in the root growth phenotype induced by H2O2. Specifically, root growth inhibition by H2O2 was diminished in transgenic Arabidopis overexpressing peroxidase but increased in a catalase2 (cat2) mutant. The strong root growth inhibition observed in the cat2 mutant upon H2O2 treatment indicated that CAT2 has an essential role in maintaining root meristem activity in the presence of oxidative stress. Overall, these results confirm that ROS function not only as stress-related compounds but that they also function as signaling molecules to regulate the progression of the cell cycle in root tips.

Response of respiratory rate and reactive oxygen species scavenging enzyme activity in seed mitochondria of <I>Clausena lansium</I> dehydration and its ecological significance

Response of respiratory rate and reactive oxygen species scavenging enzyme activity in seed mitochondria of <I>Clausena lansium</I> dehydration and its ecological significance

Comparative proteomic profiles of Pinus monticola needles during early compatible and incompatible interactions with Cronartium ribicola

The proteomic profiles of primary needles from Cr2-resistant and cr2-susceptible Pinus monticola seedlings were analysed post Cronartium ribicola inoculation by 2-DE. One hundred-and-five protein spots exhibiting significant differential expression were identified using LC-MS/MS. Functional classification showed that the most numerous proteins are involved in defence signalling, oxidative burst, metabolic pathways, and other physiological processes. Our results revealed that differential expression of proteins in response to C. ribicola inoculation was genotype- and infection-stage dependent. Responsive proteins in resistant seedlings with incompatible white pine blister rust (WPBR) interaction included such well-characterized proteins as heat shock proteins (HSPs), reactive oxygen species (ROS) scavenging enzymes, and intermediate factors functioning in the signal transduction pathways triggered by well-known plant R genes, as well as new candidates in plant defence like sugar epimerase, GTP-binding proteins, and chloroplastic ribonucleoproteins. Fewer proteins were regulated in susceptible seedlings; most of them were in common with resistant seedlings and related to photosynthesis among others. Quantitative RT-PCR analysis confirmed HSP- and ROS-related genes played an important role in host defence in response to C. ribicola infection. To the best of our knowledge, this is the first comparative proteomics study on WPBR interactions at the early stages of host defence, which provides a reference proteomic profile for other five-needle pines as well as resistance candidates for further understanding of host resistance in the WPBR pathosystem.

Melatonin promotes water‐stress tolerance, lateral root formation, and seed germination in cucumber (Cucumis sativus L.)

A comprehensive investigation was carried out to determine the changes that occurred in water-stressed cucumber (Cucumis sativus L.) in response to melatonin treatment. We examined the potential roles of melatonin during seed germination and root generation and measured its effect on reactive oxygen species (ROS) levels, antioxidant enzyme activities, and photosynthesis. Melatonin alleviated polyethylene glycol induced inhibition of seed germination, with 100 μm melatonin-treated seeds showing the greatest germination rate. Melatonin stimulated root generation and vitality and increased the root:shoot ratio; therefore, melatonin may have an effect on strengthening cucumber roots. Melatonin treatment significantly reduced chlorophyll degradation. Seedlings treated with 100 μm melatonin clearly showed a higher photosynthetic rate, thus reversing the effect of water stress. Furthermore, the ultrastructure of chloroplasts in water-stressed cucumber leaves was maintained after melatonin treatment. The antioxidant levels and activities of the ROS scavenging enzymes, i.e., superoxide dismutase, peroxidase, and catalase, were also increased by melatonin. These results suggest that the adverse effects of water stress can be minimized by the application of melatonin.