Alu antisense RNA ameliorates methylglyoxal-induced human lens epithelial cell apoptosis by enhancing antioxidant defense

AIM:To determine whether an antisense RNA corresponding to the human Alu transposable element(Aluas RNA)can protect human lens epithelial cells(HLECs)from methylglyoxal-induced apoptosis.METHODS:Cell counting kit-8(CCK-8)and 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide(MTT)assays were used to assess HLEC viability.HLEC viability/death was detected using a Calcein-AM/PI double staining kit;the annexin V-FITC method was used to detect HLEC apoptosis.The cytosolic reactive oxygen species(ROS)levels in HLECs were determined using a reactive species assay kit.The levels of malondialdehyde(MDA)and the antioxidant activities of total-superoxide dismutase(T-SOD)and glutathione peroxidase(GSH-Px)were assessed in HLECs using their respective kits.RT-q PCR and Western blotting were used to measure m RNA and protein expression levels of the genes.RESULTS:Aluas RNA rescued methylglyoxal-induced apoptosis in HLECs and ameliorated both the methylglyoxalinduced decrease in Bcl-2 m RNA and the methylglyoxalinduced increase in Bax m RNA.In addition,Aluas RNA inhibited the methylglyoxal-induced increase in Alu sense RNA expression.Aluas RNA inhibited the production of ROS induced by methylglyoxal,restored T-SOD and GSHPx activity,and moderated the increase in MDA content after treatment with methylglyoxal.Aluas RNA significantly restored the methylglyoxal-induced down-regulation of Nrf2 gene and antioxidant defense genes,including glutathione peroxidase,heme oxygenase 1,γ-glutamylcysteine synthetase and quinone oxidoreductase 1.Aluas RNA ameliorated methylglyoxal-induced increases of the m RNA and protein expression of Keap1 that is the negative regulator of Nrf2.CONCLUSION:Aluas RNA reduces apoptosis induced by methylglyoxal by enhancing antioxidant defense.

Silicon and Nitric Oxide-Mediated Regulation of Growth Attributes, Metabolites and Antioxidant Defense System of Radish (Raphanus sativus L.) under Arsenic Stress

Arsenic(As)contaminated food chains have emerged as a serious public concern for humans and animals and are known to affect the cultivation of edible crops throughout the world.Therefore,the present study was designed to investigate the individual as well as the combined effects of exogenous silicon(Si)and sodium nitroprusside(SNP),a nitric oxide(NO)donor,on plant growth,metabolites,and antioxidant defense systems of radish(Raphanus sativus L.)plants under three different concentrations of As stress,i.e.,0.3,0.5,and 0.7 mM in a pot experiment.The results showed that As stress reduced the growth parameters of radish plants by increasing the level of oxidative stress markers,i.e.,malondialdehyde and hydrogen peroxide.However,foliar application of Si(2 mM)and pretreatment with SNP(100μM)alone as well as in combination with Si improved the plant growth parameters,i.e.,root length,fresh and dry weight of plants under As stress.Furthermore,As stress also reduced protein,and metabolites contents(flavonoids,phenolic and anthocyanin).Activities of antioxidative enzymes such as catalase(CAT),ascorbate peroxidase(APX),guaiacol peroxidase(POD),and polyphenol oxidase(PPO),as well as the content of non-enzymatic antioxidants(glutathione and ascorbic acid)decreased under As stress.In most of the parameters in radish,As III concentration showed maximum reduction,as compared to As I and II concentrations.However,the individual and combined application of Si and NO significantly alleviated the As-mediated oxidative stress in radish plants by increasing the protein,and metabolites content.Enhancement in the activities of CAT,APX,POD and PPO enzymes were recorded.Contents of glutathione and ascorbic acid were also enhanced in response to co-application of Si and NO under As stress.Results obtained were more pronounced when Si and NO were applied in combination under As stress,as compared to their individual application.In short,the current study highlights that Si and NO synergistically regulate plant growth through lowering the As-mediated oxidative stress by upregulating the metabolites content,activity of antioxidative enzymes and non-enzymatic antioxidants in radish plants.

Toxic effects of crude-oil-contaminated soil in aquatic environment on Carassius auratus and their hepatic antioxidant defense system

Under the indoor simulant conditions, toxic effects of crude-oil-contaminated soil which was put into aquatic environment on the young fishes Carassius auratus and their hepatic antioxidant system after a 20-d exposure were investigated. Results showed that the relationship between the mortality of C. auratus and the exposed doses could be divided into 3 phases： fishes exposed to the low dose groups （0.5-5.0 g/L） were dead due to the ingestion of crude-oil-contaminated soils in aquatic environment; at the medium dose groups （5.0-25.0 g/L） fishes were dead due to the penetration of toxic substances; at the high dose groups （25.0-50.0 g/L） fishes were dead due to environmental stress. The highest mortality and death speed were found in the 1.0 g/L dose group, and the death speed was sharply increased in the 50.0 g/L dose group in the late phase of exposure. The activities of superoxide dismutase （SOD）, catalase （CAT） and glutathione S-transferase （GST） and the content of malaondialdehyde （MDA） in the hepatic tissues of C. auratus were induced significantly. The activity of SOD was increased and then decreased. It was significantly inhibited in the 50.0 g/L dose group. The activity of CAT was highly induced, and restored to a level which is little more than the control when the exposed doses exceeded 10.0 g/L. The activity of GST was the most sensitive, it was significantly induced in all dose groups, and the highest elevation was up to 6 times in the 0.5 g/L dose group comparing with the control. The MDA content was significantly elevated in the 50.0 g/L dose group, and the changes of the MDA content were opposite with the changes of GST activity.

Influence of fasting on muscle composition and antioxidant defenses of market-size Sparus macrocephalus

The study was conducted to investigate fasting effects on flesh composition and antioxidant defenses of market-size Sparus macrocephalus. Two hundred fish (main initial weight 580 g) were divided into two groups (control and fasted) and reared in 6 cages. After two weeks of adaptation, group I fasted for 28 d; group II was fed normally as a control. In 3, 7, 14, 21 and 28 d, 6 fish per group were sampled for proximate flesh composition, liver antioxidant enzyme activities and malondialdehyde flesh content analyses. In fasted fish, the reduction of lipid content in muscle occurred after day 3, and, compared to controls, the content of protein decreased from day 14, the activities of liver antioxidative enzymes superoxide dismutase (SOD) and glutathione peroxidase (GPX) increased from day 3, and flesh malondialdehyde levels increased from day 21. Flesh fat reduction shows that fasting may be used as a technique to reduce flesh lipid content in Sparus macrocephalus. However, considering flesh protein loss and the subsequent oxidative stress, the fasting technique should be used with precautions.

Changes in Growth,Photosynthetic Pigments,Cell Viability,Lipid Peroxidation and Antioxidant Defense System in Two Varieties of Chickpea(Cicer arietinum L.)Subjected to Salinity Stress

Salinity is one of the most severe abiotic stresses for crop production.The present study investigates the salinityinduced modulation in growth indicators,morphology and movement of stomata,photosynthetic pigments,activity of carbonic anhydrase as well as nitrate reductase,and antioxidant systems in two varieties of chickpea(Pusa-BG5023,and Pusa-BGD72).On 20^(th) day of sowing,plants were treated with varying levels of NaCl(0,50,100,150 and 200 mM)followed by sampling on 45 days of sowing.Recorded observations on both the varieties reveal that salt stress leads to a significant decline in growth,dry biomass,leaf area,photosynthetic pigments,protein content,stomatal behavior,cell viability,activity of nitrate reductase and carbonic anhydrase with the rise in the concentration of salt.However,quantitatively these changes were less in Pusa-BG5023 as compared to Pusa-BGD72.Furthermore,salinity-induced oxidative stress enhanced malondialdehyde content,superoxide radicals,foliar proline content,and the enzymatic activities of superoxide dismutase,catalase,and peroxidase.The variety Pusa-BGD72 was found more sensitive than Pusa-BG5023 to salt stress.Out of different graded concentrations(50,100,150 and 200 mM)of sodium chloride,50 mM was least toxic,and 200 mM was most damaging.The differential behavior of these two varieties measured in terms of stomatal behavior,cell viability,photosynthetic pigments,and antioxidant defense system can be used as prospective indicators for selection of chickpea plants for salt tolerance and sensitivity.

Antioxidant defense mechanisms and fatty acid catabolism in Red-billed Leiothrix(Leiothrix lutea)exposed to high temperatures

Extreme hot weather is occurring more frequently due to global warming,posing a significant threat to species survival.Birds in particular are more likely to overheat in hot weather because they have a higher body temperature.This study used a heat stress model to investigate the antioxidant defense mechanisms and changes in fatty acid catabolism in Red-billed Leiothrix(Leiothrix lutea)to gain an understanding of how birds adapt to high temperatures.The birds were divided into five groups:a control group(30℃for 0 days),1 D group(40℃for 1 day),3 D group(40℃for 3 days),14 D group(40℃for 14 days)and recovery group(40℃for 14 days,then 30℃for 14 days).Our results indicated that when Red-billed Leiothrix are subjected to heat stress,malondialdehyde(MDA)content in the liver significantly increased,as did the enzyme activities of catalase(CAT),glutathione-SH-peroxidase(GSH-PX)and total antioxidant capacity(T-AOC)in the liver.Furthermore,there was a significant increase in heat shock protein 70(HSP70)expression in the liver,while avian uncoupling protein(avUCP)expression in muscle was significantly reduced.Additionally,there was a significant reduction in fatty acid catabolism enzyme activity such as 3-hydroxyacyl-CoAdehydrogenase(HOAD)activity in the heart,and carnitine palmitoyl transferase 1(CPT-1)and citrate synthase(CS)activity in the heart and liver.Furthermore,fatty acid translocase(FAT/CD36)in the heart,heart-type fatty acid binding protein(H-FABP)and fatty acid binding protein(FABP-pm)in the liver and heart were also significantly decreased.These changes reverted after treatment,but not to the same level as the control group.Our results indicated that when Red-billed Leiothrix are exposed to heat stress their internal antioxidant defense system is activated to counteract the damage caused by high temperatures.However,even with high antioxidant levels,prolonged high temperature exposure still caused some degree of oxidative damage possibly requiring a longer recovery time.Additionally,Red-billed Leiothrix may be able to resist heat stress by reducing fatty acid transport and catabolism.

Response of antioxidant defense system in copepod Calanus sinicus Brodsky exposed to CO_2-acidified seawater

Marine zooplankton responds sensitively to elevated seawater CO_2 concentration. However, the underlying physiological mechanisms have not been studied well. We therefore investigated the effects of elevated CO_2concentration（0.08%, 0.20%, 0.50% and 1.00%） on antioxidant defense components, as well as two detoxification enzymes of Calanus sinicus（copepod）. The results showed that glutathione peroxidase（GPx） activity exposed to CO_2-acidified seawater was significantly stimulated while other antioxidant components, including glutathione-Stransferase（GST） activity, superoxide dismutase（SOD） activity decreased significantly with reduced glutathione（GSH） level and GSH/oxidized glutathione（GSSG） value. CO_2-acidified seawater exhibited stimulatory effects on adenosine triphosphatase（ATPase） activity and acetylcholinesterase（Ach E） activity was inhibited. Moreover, the results of principal component analysis indicated that 75.93% of the overall variance was explained by the first two principal components. The elevated CO_2 concentration may affect the metabolism and survivals of copepods through impacts these enzymes activities. Further studies are needed to focus on the synergistic effects of elevated CO_2 concentration and other environmental factors on copepods.

Response of enzymatic and non-enzymatic antioxidant defense systems of Polygonum hydropiper to Mn stress

The response of enzyme and non-enzymatic antioxidants of Mn hyperaccumuator, Polygonum hydropiper （P. hydropiper）, to Mn stress was studied using hydroponics culture experiments to explore the mechanism of Mn tolerance in this species. Results showed that both chlorophyll and carotenoid contents significantly （p〈0.05） decreased with increasing Mn treatment levels （0, 0.5, 1, 2, 4, and 8 mg/L） in hydroponics. The concentrations of malondialdehyde （MDA） and hydrogen peroxide （H202） in the root and shoot of P hydropiper were accumulated under Mn stress. Meanwhile, the anti-oxidative functions of several important enzymes, including superoxide dismutase （SOD）, catalase （CAT）, ascorbate peroxidase （APX） and peroxidase （POD） in plants were stimulated by Mn spike in leaves and roots, especially at low Mn stress; while sulfhydryl group （--SH） and glutathion （GSH） were likely involved in Mn detoxification ofP. hydropiper under high Mn stress.

Therapeutic implications of antioxidant defense in acute pancreatitis

Acute pancreatitis is an inflammation initially localized in the pancreas,which may be accompanied with severe complications such as multi-organ failure,gastrointestinal hemorrhage and malnutrition.One in ten severe cases of acute pancreatitis develops systemic inflammatory response syndrome.Despite treatment,acute pancreatitis can be a life-threatening disease as its mortality rate amounts to 5%-10%in general,and up to 35%in cases of severe course.[1]Over the years,the role of oxidative stress

Context‑dependent antioxidant defense system(ADS)‑based stress memory in response to recurrent environmental challenges in congeneric invasive species

Marine ecosystems are facing escalating environmental fluctuations owing to climate change and human activities,imposing pressures on marine species.To withstand recurring environmental challenges,marine organisms,especially benthic species lacking behavioral choices to select optimal habitats,have to utilize well-established strategies such as the antioxidant defense system(ADS)to ensure their survival.Therefore,understanding of the mechanisms governing the ADS-based response is essential for gaining insights into adaptive strategies for managing environmental challenges.Here we conducted a com-parative analysis of the physiological and transcriptional responses based on the ADS during two rounds of'hypersalinity-recovery'challenges in two model congeneric invasive ascidians,Ciona robusta and C.savignyi.Our results demonstrated that C.savignyi exhibited higher tolerance and resistance to salinity stresses at the physiological level,while C.robusta demonstrated heightened responses at the transcriptional level.We observed distinct transcriptional responses,particularly in the utilization of two superoxide dismutase(SOD)isoforms.Both Ciona species developed physiological stress memory with elevated total SOD(T-SOD)and glutathione(GSH)responses,while only C.robusta demonstrated transcriptional stress memory.The regulatory distinctions within the Nrf2-Keap1 signalling pathway likely explain the formation disparity of transcriptional stress memory between both Ciona species.These findings support the'context-dependent stress memory hypothesis',emphasizing the emergence of species-specific stress memory at diverse regulatory levels in response to recurrent environmental challenges.Our results enhance our understanding of the mechanisms of environmental challenge manage-ment in marine species,particularly those related to the ADS.

Foliar application of strigolactones improves the desiccation tolerance,grain yield and water use efficiency in dryland wheat through modulation of non-hydraulic root signals and antioxidant defense

Non-hydraulic root signals(nHRS)are affirmed as a unique positive response to soil drying,and play a crucial role in regulating water use efficiency and yield formation in dryland wheat production.Strigolactones(SLs)can enhance plant drought adaptability.However,the question of whether strigolactones enhance grain yield and water use efficiency by regulating nHRS and antioxidant defense systems in dryland wheat remains unanswered.In this study,pot experiments were conducted to investigate the effects of strigolactones on nHRS,antioxidant defense system,and grain yield and water use efficiency in dryland wheat.The results showed that external application of SLs increased drought-induced abscisic acid(ABA)accumulation and activated an earlier trigger of nHRS at 73.4% field capacity(FC),compared to 68.5%FC in the control group(CK).This phenomenon was mechanically associated with the physiological mediation of SLs.The application of SLs significantly enhanced the activities of leaf antioxidant enzymes,reduced ROS production,and mitigated oxidative damage to lipid membrane.Additionally,root biomass,root length density,and root to shoot ratio were increased under strigolactone treatment.Furthermore,exogenous application of SLs significantly increased grain yield by 34.9%under moderate drought stress.Water use efficiency was also increased by 21.5% and 33.3% under moderate and severe drought conditions respectively,compared to the control group(CK).The results suggested that the application of strigolactones triggered earlier drought-sensing mechanism and improved the antioxidant defense ability,thus enhancing grain yield and water use efficiency in dryland wheat production.

The C_2H_2 -type Zinc Finger Protein ZFP182 is Involved in Abscisic Acid-Induced Antioxidant Defense in Rice

C2H2-type zinc finger proteins （ZFPs） are thought to play important roles in modulating the responses of plants to drought, salinity and oxidative stress. However, direct evidence is lacking for the involvement of these ZFPs in abscisic acid （ABA）-induced antioxidant defense in plants. In this study, the role of the rice （Oryza sativa L. sub.japonica cv. Nipponbare） C2H2-type ZFP ZFP182 in ABA-induced antioxidant defense and the relationship between ZFP182 and two rice MAPKs, OsMPK1 and OsMPK5 in ABA signaling were investigated. ABA treatment induced the increases in the expression of ZFP182, OsMPK1 and OsMPK5, and the activities of superoxide dismutase （SOD） and ascorbate peroxidase （APX） in rice leaves. The transient gene expression analysis and the transient RNA interference （RNAi） analysis in protoplasts showed that ZFP182, OsMPK1 and OsMPK5 are involved in ABA-induced up-regulation in the activities of SOD and APX. Besides, OsMPK1 and OsMPK5 were shown to be required for the up-regulation in the expression of ZFP182 in ABA signaling, but ZFP182 did not mediate the ABA-induced up-regulation in the expression of OsMPK1 and OsMPKS. These results indicate that ZFP182 is required for ABA-induced antioxidant defense and the expression of ZFP182 is regulated by rice MAPKs in ABA signaling.

OsDMI3 Is a Novel Component of Abscisic Acid Signaling in the Induction of Antioxidant Defense in Leaves of Rice

Ca^2＋ and calmodulin （CAM） have been shown to play an important role in abscisic acid （ABA）-induced anti- oxidant defense. However, it is unknown whether Ca^2＋/CaM-dependent protein kinase （CCaMK） is involved in the pro- cess. In the present study, the role of rice CCaMK, OsDMI3, in ABA-induced antioxidant defense was investigated in leaves of rice （Oryza sativa） plants. Treatments with ABA, H2O2, and polyethylene glycol （PEG） induced the expression of OsDMI3 and the activity of OsDMI3, and H2O2 is required for the ABA-induced increases in the expression and the activity of OsDMI3 under water stress. Subcellular localization analysis showed that OsDMI3 is located in the nucleus, the cytoplasm, and the plasma membrane. The analysis of the transient expression of OsDMI3 in rice protoplasts and the RNA interference （RNAi） silencing of OsDMI3 in rice protoplasts showed that OsDMI3 is required for ABA-induced increases in the expression and the activities of superoxide dismutase （SOD） and catalase （CAT）. Further, the oxidative damage induced by higher concentrations of PEG and H202 was aggravated in the mutant of OsDMI3. Moreover, the analysis of the RNAi silencing of OsDMI3 in protoplasts and the mutant of OsDMI3 showed that higher levels of H2O2 accumulation require OsDMI3 activation in ABA signaling, but the initial H2O2 production induced by ABA is not depend- ent on the activation of OsDMI3 in leaves of rice plants. Our data reveal that OsDMI3 is an important component in ABA-induced antioxidant defense in rice.

Involvement of Polyamine Oxidase in Abscisic Acidinduced Cytosolic Antioxidant Defense in Leaves of Maize

Using pharmacological and biochemical approaches, the role of maize polyamine oxidase （MPAO） in abscisic acid （ABA）- induced antioxidant defense in leaves of maize （Zea mays L.） plants was investigated. Exogenous ABA treatment enhanced the expression of the MPAO gene and the activities of apoplastic MPAO. Pretreatment with two different inhibitors for apoplastic MPAO partly reduced hydrogen peroxide （H202） accumulation induced by ABA and blocked the ABA-induced expression of the antioxidant genes superoxide dismutase 4 and cytosolic ascorbate peroxidase and the activities of the cytosolic antioxidant enzymes. Treatment with spermidine, the optimum substrate of MPAO, also induced the expression and the activities of the antioxidant enzymes, and the upregulation of the antioxidant enzymes was prevented by two inhibitors of MPAO and two scavengers of H202. These results suggest that MPAO contributes to ABA-induced cytosolic antioxidant defense through H202, a Spd catabolic product.

Involvement of Protein Phosphorylation in Water Stress-induced Antioxidant Defense in Maize Leaves

Using pharmacological and biochemical approaches, the role of protein phosphorylation and the interrelationship between water stress-enhanced kinase activity, antioxidant enzyme activity, hydrogen peroxide （H202） accumulation and endogenous abscisic acid in maize （Zea mays L.） leaves were investigated. Water-stress upregulated the activities of total protein phosphorylation and Ca^2＋-dependent protein kinase, and the upregulation was blocked in abscisic aciddeficient vp5 mutant. Furthermore, pretreatments with a nicotinamide adenine dinucleotide phosphate oxidase inhibitor and a scavenger of H2O2 significantly reduced the increased activities of total protein kinase and Ca^2＋-dependent protein kinase in maize leaves exposed to water stress. Pretreatments with different protein kinase inhibitors also reduced the water stress-induced H2O2 production and the water stress-enhanced activities of antioxidant enzymes such as superoxide dismutase, catalase, ascorbate peroxidase and glutathione reductase. The data suggest that protein phosphorylation and H2O2 generation are required for water stress-induced antioxidant defense in maize leaves and that crosstalk between protein phosphorylation and H2O2 generation may occur.

OsHK3 is a crucial regulator of abscisic acid signaling involved in antioxidant defense in rice

In this study, the role of the rice （Oryza sativa L.） histidine kinase OsHK3 in abscisic acid （ABA）-induced antioxidant defense was investigated. Treatments with ABA, H2O2, and polyethylene glycol （PEG） induced the expression of OsHK3 in rice leaves, and H2O2 is required for ABA-induced increase in the expression of OsHK3 under water stress. Subcellular localization analysis showed that OsHK3 is located in the cytoplasm and the plasma membrane. The transient expression analysis and the transient RNA interference test in rice protoplasts showed that OsHK3 is required for ABA-induced upreguiation in the expression of antioxidant enzymes genes and the activities of antioxidant enzymes. Further analysis showed that OsHK3 functions upstream of the calcium/ calmodulin-dependent protein kinase OsDMI3 and the mitogen-activated protein kinase OsMPK1 to regulate the activities of antioxidant enzymes in ABA signaling. Moreover, OsHK3 was also shown to regulate the expression of nicotinamide adenine dinucleotide phosphate oxidase genes, OsrbohB and OsrbohE, and the production of H2O2 in ABA signaling. Our data indicate that OsHK3 play an important role in the regulation of ABA-induced antioxidant defense and in the feedback regulation of H2O2 production in ABA signaling.

Cadmium-induced oxidative damage and antioxidant defense mechanisms in Glycine max L.

Objective:To analyze the effect of Cadmium(Cd)on the metabolism of reduced glutathione(GSH)in roots and leaves of Glycine max L.Methods:A capillary electrophoresis methodology was optimized to determinate simultaneously GSH and reduced and oxidized GSH in a precise and accurate way.The functional role of the genes involved in GSH cellular metabolism(γ-glutamylcysteine synthetase),GSH synthetase and glutathione reductase(GR)was evaluated.Finally,the activities of antioxidant enzymes as GR and superoxide dismutases were determinate.Results:The studies ofγ-glutamylcysteine synthetase and GSH synthetase gene expression showed an increase and GR showed a decrease in Cd-treated plants.GR and superoxide dismutases activities increased at 24 h and 6 h respectively in roots under Cd exposure.GSH content was higher and showed a significant increase in roots and leaves at 6 h and 24 h of treatment.Conclusions:The results of the present study showed a better understanding in signaling pathway by alterations in antioxidant mechanisms by Cd in soybean seedlings.

Grain Yield,Biomass Accumulation,and Leaf Photosynthetic Characteristics of Rice under Combined Salinity-Drought Stress

Simultaneous stresses of salinity and drought often coincide during rice-growing seasons in saline lands,primarily due to insufficient water resources and inadequate irrigation facilities.Consequently,combined salinity-drought stress poses a major threat to rice production.In this study,two salinity levels(NS,non-salinity;HS,high salinity)along with three drought treatments(CC,control condition;DJ,drought stress imposed at jointing;DH,drought stress imposed at heading)were performed to investigate their combined influences on leaf photosynthetic characteristics,biomass accumulation,and rice yield formation.Salinity,drought,and their combination led to a shortened growth period from heading to maturity,resulting in a reduced overall growth duration.Grain yield was reduced under both salinity and drought stress,with a more substantial reduction under the combined salinity-drought stress.The combined stress imposed at heading caused greater yield losses in rice compared with the stress imposed at jointing.Additionally,the combined salinity-drought stress induced greater decreases in shoot biomass accumulation from heading to maturity,as well as in shoot biomass and nonstructural carbohydrate(NSC)content in the stem at heading and maturity.However,it increased the harvest index and NSC remobilization reserve.Salinity and drought reduced the leaf area index and SPAD value of flag leaves and weakened the leaf photosynthetic characteristics as indicated by lower photosynthetic rates,transpiration rates,and stomatal conductance.These reductions were more pronounced under the combined stress.Salinity,drought,and especially their combination,decreased the activities of ascorbate peroxidase,catalase,and superoxide dismutase,while increasing the contents of malondialdehyde,hydrogen peroxide,and superoxide radical.Our results indicated a more significant yield loss in rice when subjected to combined salinity-drought stress.The individual and combined stresses of salinity and drought diminished antioxidant enzyme activities,inhibited leaf photosynthetic functions,accelerated leaf senescence,and subsequently lowered assimilate accumulation and grain yield.

Antioxidant responses to benzo[a]pyrene,tributyltin and their mixture in the spleen of Sebasticus marmoratus

It has been reported that there is an interaction between Benzo[a]pyrene （BaP）, a widespread carcinogenic polycyclic aromatic hydrocarbon, and tributyltin （TBT）, an organometal used as an antifouling biocide. This study was therefore designed to examine the potential in vivo influence of BaP, TBT and their mixture on splenic antioxidant defense systems of Sebastiscus marmoratus. The fish were exposed to water containing environmentally relevant concentrations of BaP, TBT and their mixture. Spleens were collected for biochemical analysis after exposure for 7, 25, 50 d and after recovery for 7, 20 d. Cotreatment with BaP and TBT for 7 d potentiated the induction of glutathione peroxidase （GPx） activity by BaP or TBT alone. The cotreatment for 25 and 50 d resulted in inhibition of GPx activity, which was similar to the effect of TBT. Splenic glutathione S-transferase （GST） activities were significantly elevated in S. marmoratus exposed to BaP starting from 7 d and remained high up to 25 d. However, no further activity change was found with prolonged exposure. Cotreatment of BaP and TBT primarily inhibited the GST activity, which was similar to the effect of TBT. Cotreatment with BaP and TBT for 25 or 50 d potentiated the depletion of GSH （glutathione） by BaP or TBT alone. MDA （malondialdehyde） contents in spleen of S. marmoratus were not significantly altered compared with the control during the test period. Spleen, as an immune organ, is sensitive to exposure of BaP or TBT. It should have an effective mechanism to counteract oxidative damage. Antioxidative defense systems in spleen of S. marmoratus should be considered as potential biomarkers. Short-term exposure of BaP or TBT could result in induction of antioxidant defense system. A significant decrease of these indices, such as GSH, GST, GPx might indicate more severe contamination.

Responses of the antioxidant system to fluroxypyr in foxtail millet (Setaria italica L.) at the seedling stage

Foxtail millet （Setaria italica L.） is an important food and fodder crop in semi-arid areas. However, there are few herbicides suitable for use on weed control in field-grown foxtail millet during the post-emergence herbicides stage. The present study was conducted using four concentrations （0.5, 1, 2, and 4 L ai ha-1） of foliar-applied fluroxypyr, and the effect of fluroxypyr on selected metabolic and stress-related parameters in foxtail millet were assessed after 15 days. In this study, increasing concentrations decreased plant height and accumulation of chlorophylls. Our results also showed that malondialdehyde （MDA） accumulated in response to fluroxypyr application, demonstrating increased lipid peroxidation due to excessive reactive oxygen species production. In response to this oxidative stress, the activities of antioxidant enzymes were generally enhanced. Non-enzymatic antioxidant defense systems, which function in concert with antioxidant enzymes, can also protect plant cells from oxidative damage by scavenging reactive oxygen species （ROS）. In conclusion, the hybrid variety （Zhangzagu） exhibited a greater tolerance to fluroxypyr than did the conventional variety Jingu 21, which might be associated with the antioxidant mechanisms of Zhangzagu hybrid millet.