Activities Of DHAR Research Articles

Expression of Heterologous OsDHAR Gene Improves Glutathione (GSH)-Dependent Antioxidant System and Maintenance of Cellular Redox Status in Synechococcus elongatus PCC 7942.

An excess of reactive oxygen species (ROS) can cause severe oxidative damage to cellular components in photosynthetic cells. Antioxidant systems, such as the glutathione (GSH) pools, regulate redox status in cells to guard against such damage. Dehydroascorbate reductase (DHAR, EC 1.8.5.1) catalyzes the glutathione-dependent reduction of oxidized ascorbate (dehydroascorbate) and contains a redox active site and glutathione binding-site. The DHAR gene is important in biological and abiotic stress responses involving reduction of the oxidative damage caused by ROS. In this study, transgenic Synechococcus elongatus PCC 7942 (TA) was constructed by cloning the Oryza sativa L. japonica DHAR (OsDHAR) gene controlled by an isopropyl β-D-1-thiogalactopyranoside (IPTG)-inducible promoter (Ptrc) into the cyanobacterium to study the functional activities of OsDHAR under oxidative stress caused by hydrogen peroxide exposure. OsDHAR expression increased the growth of S. elongatus PCC 7942 under oxidative stress by reducing the levels of hydroperoxides and malondialdehyde (MDA) and mitigating the loss of chlorophyll. DHAR and glutathione S-transferase activity were higher than in the wild-type S. elongatus PCC 7942 (WT). Additionally, overexpression of OsDHAR in S. elongatus PCC 7942 greatly increased the glutathione (GSH)/glutathione disulfide (GSSG) ratio in the presence or absence of hydrogen peroxide. These results strongly suggest that DHAR attenuates deleterious oxidative effects via the glutathione (GSH)-dependent antioxidant system in cyanobacterial cells. The expression of heterologous OsDHAR in S. elongatus PCC 7942 protected cells from oxidative damage through a GSH-dependent antioxidant system via GSH-dependent reactions at the redox active site and GSH binding site residues during oxidative stress.

Seed Priming with Jasmonic Acid Counteracts Root Knot Nematode Infection in Tomato by Modulating the Activity and Expression of Antioxidative Enzymes.

The environmental stress, biotic as well as abiotic, is the main cause of decreased growth and crop production. One of the stress-causing agents in plants are parasitic nematodes responsible for crop loss. Jasmonic acid (JA) is recognized as one of signaling molecules in defense-related responses in plants, however, its role under nematode infestation is unclear. Therefore, the present study was planned to traverse the role of JA in boosting the activities of antioxidative enzymes in tomato seedlings during nematode inoculation. Application of JA declined oxidative damage by decreasing O2•− content, nuclear and membrane damage under nematode stress. JA treatment elevated the activities of SOD, POD, CAT, APOX, DHAR, GPOX, GR, and PPO in nematode-infested seedlings. Seed soaking treatment of JA upregulated the expression of SOD, POD, CAT, and GPOX under nematode stress. Various amino acids were found in tomato seedlings and higher content of aspartic acid, histidine, asparagine, glutamine, glutamic acid, glycine, threonine, lysine, arginine, B-alanine, GABA, phenylalanine, proline, and ornithine was observed in seeds soaked with JA (100 nM) treatment during nematode inoculation. The results suggest an indispensable role of JA in basal defense response in plants during nematode stress.

Ammonium nutrition mitigates cadmium toxicity in rice (Oryza sativa L.) through improving antioxidase system and the glutathione-ascorbate cycle efficiency.

Nitrogen (N) forms not only affect cadmium (Cd) accumulation in plants, but also affect plant resistance to Cd toxicity. However, few researches have been reported underlying the mechanism of the relationship between nitrogen forms and plant resistance under Cd exposure. Here, we explored the mechanism on how different NO3-/NH4+ ratios affect antioxidase system and the glutathione-ascorbate cycle under five different ratios of NO3-/NH4+ (1:0, 2:1, 1:1, 1:2, 0:1) and three dosages of Cd exposure (0, 1, 5μmolL-1 Cd) in rice (Oryza sativa L.). The results showed that high NO3- and high Cd exposure both significantly inhibited tissue growth of rice plants, and this inhibiting trend was mitigated with increasing NH4+ ratios as proved by the increased biomass and the decreased concentrations of malonaldehyde (MDA) and hydrogen peroxide (H2O2), as well as the levels of Cd contents in rice tissues. Additionally, high NH4+ ratios elevated the SOD activities in rice tissues, especially at high Cd treatment. However, other two antioxidases (CAT and APX) were insensitive to changes of NO3-/NH4+ ratios (except the full NO3-). Furthermore, high NH4+ ratios induced increasing of the efficiency of glutathione-ascorbate cycle (GSH-AsA) under two levels of Cd exposure, as evidenced by increasing concentrations of GSH and AsA and the activities of GR and DHAR in rice tissues. Overall, these results revealed that ammonium nutrition caused an enhancement resistance to Cd stress in rice plants was responsible for increasing of partial antioxidase system and the efficiencies of GSH-AsA cycle.

Differential Responses of Two Wheat Varieties Differing in Salt Tolerance to the Combined Stress of Mn and Salinity

The effect of Mn and NaCl on growth, mineral nutrients and antioxidative enzymes in two tetroploid wheat genotypes differing in salt tolerance was investigated in this study. 100 mM NaCl and Mn stress significantly inhibited plant growth, photosynthesis and Ca uptake, while stimulated ROS accumulation, MDA and proline content in wheat plants, Mn stress also increased SOD, APX, GR and DHAR activities. Durum wheat (AS780) was less affected by 100 mM NaCl and Mn stress than emmer wheat (AS847) due to more proline production, higher antioxidative enzymes activities and less-affected mineral nutrients. Application of 10 mM NaCl to Mn-stressed durum wheat alleviated Mn-induced damage by reducing Mn accumulation and translocation, while promoting proline accumulation and SOD, APX and GR activities. Irrespective of NaCl level, the combined stress of Mn and NaCl caused more severe oxidative stress, result in further reduction of photosynthetic rate and plant growth in emmer wheat as compared to Mn stress alone. The additively negative effects of NaCl and Mn stress on growth of emmer wheat results from reduced SOD and APX activities as well as Ca, Cu and Fe accumulation in both shoots and roots. These results suggest that salt-tolerant durum wheat is superior to emmer in adapting to Mn stress and the combined stress of salinity and Mn.

Effect of High-Temperature Stress on Ascorbate–Glutathione Cycle in Maize

High-temperature stress induces cellular changes leading to over-production of highly reactive oxygen species (ROS) which damage macromolecules and cell organelles, eventually resulting in cell death. Antioxidative metabolism in plants comprising of enzymatic and non-enzymatic antioxidants imparts tolerance by scavenging or detoxification of excess ROS. We investigated the response of major H2O2-detoxifying system, the AsA–GSH cycle in four genotypes of maize differing in heat sensitivity. Stress was imposed by staggered sowing so that one set of plants faced high-temperature stress at their anthesis-silking stage. The concentrations of H2O2 increased across the genotypes by high temperature; however, the increase was lesser in tolerant genotypes: NSJ 189 and NSJ 221. High-temperature stress led to an increase in the level of GSH and GSSG in all the genotypes, whereas GSH/GSSG decreased in sensitive genotypes: PSRJ 13099 and RJR 270. The glutathione S-transferase activity increased significantly under heat stress. APX, MDHAR and DHAR activities decreased under heat stress in the sensitive group. Under high temperature, GR activity remained unchanged in sensitive genotypes, while it increased significantly in tolerant genotypes. Ascorbate levels increased in tolerant genotypes, while a decline was observed in sensitive genotypes. Isoforms of APX showed some new bands in tolerant genotypes as well as higher intensity of the existing ones as compared to sensitive genotypes under stress conditions. Isoforms of GR did not show any genotypic differences under heat stress. Findings emphasized the importance and complexity of the AsA–GSH system in fine-tuning the redox metabolism under heat stress in maize. The study also suggested that the antioxidative enzymes of AsA–GSH cycle play a key role in sustaining the ROS homeostasis in cells, thus minimizing the potential toxic effects of ROS.

Comparison of foliar silicon and selenium on cadmium absorption, compartmentation, translocation and the antioxidant system in Chinese flowering cabbage

Silicon (Si) and selenium (Se) are beneficial for many higher plants when grown on stress conditions. However, the mechanisms underlying the differential effects between foliar Si and Se in alleviation of plant toxicity exposed to cadmium (Cd) stress are remained unclear. In this study, we investigated the discrepant mechanisms of foliar Si and Se on Cd absorption and compartmentation by roots, its translocation in xylem, and the antioxidant system within Chinese flowering cabbage (Brassica campestris L. ssp. chinensis var. utilis) under low and high Cd stress. Results showed that plant growth was significantly enhanced by foliar additions of Si or/and Se according to an increased plant tissue biomass at high Cd exposure. In addition, the foliar coupled addition of Si and Se showed little effects on the concentrations of Si or Se in plant tissues in comparison with the single addition of foliar Si or Se respectively. The foliar Si alone or combined with Se markedly reduced the Cd concentrations in plant shoots under two Cd treatments. This might be explained by the lower Cd concentrations in symplast and apoplast and the higher Cd concentrations in cell walls of plant roots, and the lower Cd concentrations in xylem sap. However, no great changes in these values were observed under the treatments of foliar Se alone. Moreover, the foliar additions of Si or/and Se all increased the antioxidant enzyme activities of SOD, CAT and APX in plant tissues, especially at high Cd dosage. No significant differences in the increasing degrees of these three antioxidant enzymes were found between the foliar Si and Se treatments. However, only the foliar Se alone or combined with Si markedly promoted the antioxidant enzyme activities of GR and DHAR in plant tissues. Our findings demonstrate that the alleviation of Cd toxicity by foliar Si maybe mainly responsible for inhibition of Cd absorption and its translocation to plant shoots, reinforcing its compartmentation into root cell walls, whilst enhancing the antioxidant enzyme system may be employed by foliar Se.

Influence of sodium chloride on the dehydroascorbate reductase activity in Arabidopsis thaliana catalase 2 knokout mutant

Aim. To better understand the mechanisms of abiotic stress resistance in plants, it is important to clarify the role of individual antioxidant enzymes from the same multiproteinic family in the response to stress. It is known that the loss of some isoforms of antioxidant enzymes can be compensated by activation of other enzymes. However, the functional interaction of the ascorbate-glutathione cycle enzymes with catalase under salt stress still remains unexplored. Respectively, we determined the activity of DHAR in knock-out mutants of Arabidopsis thaliana under salt stress. Methods. The DHAR activity was determined in the knock-out line cat2 and in wild-type (WT) Arabidopsis plants after various regimes of treatment with sodium chloride. Results. After treatment with 200 mM sodium chloride in the dark, activation of DHAR was found after 8 hours in WT plants and after 4 hours in the knock-out line cat2. However stress treatment under illumination resulted in significant increase in DHAR activity after 8 hours in both studied lines. In this case, DHAR activity in cat2 was lower than in WT, whereas in non-treated plants or upon stress treatment in the dark no difference between the tested lines was detected. Conclusions. The obtained data indicate that under salt stress conditions, changes in the DHAR activity are included into functional rearrangements of the antioxidant system in cat2 line, which compensate the loss of activity of CAT2 isoenzyme.Keywords: dehydroascorbate reductase, antioxidants, reactive oxygen species (ROS), salt stress, Arabidopsis thaliana

Hydrogen Peroxide is Involved in the Regulation of Ascorbate and Glutathione Metabolism in Wheat Leaves under Water Stress

This study investigated the regulation of ascorbic acid and glutathione metabolism by hydrogen peroxide in wheat leaves under water stress. The results showed that H2O2 level, the activities of ascorbate peroxidase, glutathione reductase, monodehydroascorbate reductase, dehydroascorbate reductase, L-galactono-1,4-lactone dehydrogenase and gamma-glutamylcysteine synthetase, and the contents of reduced ascorbate, reduced glutathione, total ascorbate and total glutathione were increased by water stress. And above increases were suppressed by pre-treatment with NADPH oxidase inhibitor diphenyleneiodonium chloride. Application of DPI also reduced H2O2 level, the activities of γ-ECS, GalLDH, APX, GR, DHAR and MDHAR, and the contents of AsA, GSH, total ascorbate and total glutathione, compared with control. Application of H2O2 to DPI-inhibited wheat seedlings prevented the reduction in the activities of APX, GR, MDHAR, DHAR, GalLDH and γ-ECS, and the contents of AsA, GSH, total ascorbate and total glutathione induced by DPI under water stress. Meanwhile, pre-treatment with DPI increased the malondialdehyde content and electrolyte leakage. Application of H2O2 to DPI-inhibited wheat seedlings prevented the increases in MDA content and EL. Our results suggested that water stress-induced H2O2 is a signal that leads to the up-regulation of ascorbate and glutathione metabolism and has an important role for acquisition of water-stress tolerance in wheat.

Jasmonic acid-induced NO activates MEK1/2 in regulating the metabolism of ascorbate and glutathione in maize leaves.

This study investigated the relationship between MEK1/2 and nitric oxide (NO) in jasmonic acid (JA)-regulated metabolism of ascorbate and glutathione in maize leaves. The results showed that JA increased the activities of APX, GR, MDHAR, DHAR, GalLDH, and γ-ECS; the contents of AsA and GSH; and the production of NO. Above increases except for γ-ECS activity and NO production were all suppressed by pre-treatments with MEK1/2 inhibitors PD98059 and U0126. Above increases were all suppressed by pre-treatments with nitric oxide synthase (NOS) inhibitor L-NAME and NO scavenger cPTIO. The results of western blot showed that JA enhanced the phosphorylation level of MEK1/2. Pre-treatments with L-NAME and cPTIO suppressed JA-induced phosphorylation level of MEK1/2. Our results suggested that JA-induced NO activated MEK1/2 by increasing the phosphorylation level, which, in turn, resulted in the upregulation of ascorbate and glutathione metabolism in maize leaves.

Effects of antimony on redox activities and antioxidant defence systems in sunflower (Helianthus annuus L.) plants.

The alterations induced by the toxicity of antimony (Sb) in the roots and leaves of sunflower plants were determined. The plants were grown hydroponically with different concentrations of Sb, a heavy metal which reduces biomass production and growth. There was preferential accumulation of Sb in the tissues of the roots, with the concentrations in the leaves being much lower. The accumulation of other mineral elements was also altered, especially that of Fe and Zn. Chlorophyll content declined, as also did the photosynthetic efficiency, but the carotenoid content remained unaltered. The total content of phenolics, flavonoids, and phenylpropanoid glycosides rose, evidence of their participation in the defence response. Increases were observed in the amount of superoxide anion in both roots and leaves, and in lipid peroxidation levels, especially with the highest Sb concentration of 1.0 mM. The induced oxidative stress leads to a strong increase in the SOD, POX and APX antioxidant activities, while the GR activity was only increased in the leaves and at the 1.0 mM Sb concentration. In contrast, the DHAR activity increased considerably in both organs. The GSNOR activity increased only in roots, and the total RSNOs increased. The total amount of AsA + DHA increased in roots and remained unaltered in leaves, whereas that of GSH + GSSG decreased considerably in all cases. As a whole, these results are evidence for the development of a strong oxidative stress induced by Sb, with there being a clear imbalance in the content of the compounds that constitute the AsA/GSH cycle. 0.5 mM Sb enhances GST expression, especially in leaves. This, together with the increase that was observed in the amount of GSH, may play an important part in detoxification. This oxidative stress affects both the phenolic and the ROS/RNS metabolic processes, which seems to implicate their involvement in the plant's defence and response to the stress.

Активність DHAR у рослин Arabidopsis thaliana за дії сольового стресу

Активність DHAR у рослин Arabidopsis thaliana за дії сольового стресу

Differential enzymatic defense mechanisms in leaves and roots of two true mangrove species under long- term salt stress

To elucidate the role of antioxidative defense system against salt stresses, the levels of antioxidative enzymes and lipid peroxidation were quantified in leaves and roots of 2-year old Kandelia candel and Rhizophora stylosa seedlings subjected to 0, 5, 15 and 30 parts per thousand (ppt) of salt concentrations during one and two months treatments (1MT and 2MT). The data revealed differential responses between the species to different salt concentrations, while no significant differences observed between the treatment periods.In leaves, higher salinity decreased superoxide dismutase (SOD) and monodehydroascorbate reductase (MDHAR) activities in both species and catalase (CAT) activity in K. candel, while ascorbate peroxidase (APX) and guaiacol peroxidase (GPX) activities in both species and CAT in R. stylosa were increased. In roots, salt stresses increased the activities of most of the tested enzymes. Except for the roots K. candel, the malondialdehyde (MDA) contents were decreased significantly at higher salt concentrations.In K. candel leaves, moderate to strong negative correlations existed between APX, GPX and DHAR activities with MDA content, while SOD, CAT and MDHAR showed positive correlations. Contrarily, in R. stylosa leaves, CAT, APX and sometimes GPX and DHAR showed inverse correlations with respective MDA, while other enzymes showed reverse correlations. With few exceptions, all tested enzymes in roots showed negative correlations with MDA. These results suggested that most of the antioxidant enzymes in roots acted coordinately for effective stress mitigation, while leaf tissues might adopt many other mechanisms for salt tolerance of mangrove plants where antioxidant enzymes played minor role.

Arabidopsis dehydroascorbate reductase 1 and 2 modulate redox states of ascorbate-glutathione cycle in the cytosol in response to photooxidative stress.

Ascorbate and glutathione are indispensable cellular redox buffers and allow plants to acclimate stressful conditions. Arabidopsis contains three functional dehydroascorbate reductases (DHAR1-3), which catalyzes the conversion of dehydroascorbate into its reduced form using glutathione as a reductant. We herein attempted to elucidate the physiological role in DHAR1 and DHAR2 in stress responses. The total DHAR activities in DHAR knockout Arabidopsis plants, dhar1 and dhar2, were 22 and 92%, respectively, that in wild-type leaves. Under high light (HL), the levels of total ascorbate and dehydroascorbate were only reduced and increased, respectively, in dhar1. The oxidation of glutathione under HL was significantly inhibited in both dhar1 and dhar2, while glutathione contents were only enhanced in dhar1. The dhar1 showed stronger visible symptoms than the dhar2 under photooxidative stress conditions. Our results demonstrated a pivotal role of DHAR1 in the modulation of cellular redox states under photooxidative stress.

Growth performance and antioxidative response in bread and durum wheat plants grown with varied potassium treatments under ambient and elevated carbon dioxide

It is predicted that atmospheric carbon dioxide (CO2) level will double by the end of the current century. Although the fertilization effect of CO2 on plant growth is well documented, studies that investigate plant nutritional requirements under elevated CO2 are scarce. Potassium (K) is an essential plant nutrient with prominent roles in key physiological processes. Aim of this work, was to determine the effects of K deficiency on plant growth as affected by elevated CO2 and how antioxidant defense systems (activities of SOD, CAT, POX, APX, GR, MDHAR, DHAR, lipid peroxidation and total antioxidant activity) respond to K deficiency under ambient (a-CO2: 400ppm) or elevated (e-CO2: 900ppm) atmospheric CO2 conditions in durum (Triticum durum cv. Sarıçanak-98) and bread wheat (Triticum aestivum cv. Adana-99). Plants were grown in hydroponics with sufficient (1850μM), low (60μM) or deficient (20μM)K and under a-CO2 or e-CO2. As expected, e-CO2 promoted biomass production with adequate K supply, however in low and deficient K plants biomass was either not affected or even decreased by e-CO2. It was observed that low or deficient supply of K induced oxidative stress, but e-CO2 had no significant impact on antioxidative response of plants and thus could not alleviate detrimental effects of K deficiency. Under K deficiency, CAT activity decreased in both species but this decrease was accompanied with increases in POX and APX which may be for adapting to the changing environment. In general, responses in antioxidant defense enzymes were linked to K nutritional status of plants rather than e-CO2 conditions.

Antioxidant pool optimization in Carthamus tinctorius L. leaves under different NaCl levels and treatment durations

Safflower (Carthamus tinctorius L.) leaves are a good source of natural antioxidants, but their content is highly related to the plant response to NaCl constraint; therefore, optimizing culture conditions is required to improve leaf antioxidant accumulation while maintaining acceptable biomass production under stressful conditions. Leaves from plants grown at (0, 25, 50, and 75 mM NaCl) for three treatment durations (7, 15, and 30 days) were studied. NaCl concentrations and treatment durations for optimal biomass and biomolecules production were concluded. After 30 days of treatment, 25 mM NaCl enhanced total AsA leaf accumulation, while glutathione, soluble protein accumulation as well as SOD and GR activities were promoted at 75 mM NaCl. Non-significant changes were found for MDHAR and DHAR activity, added to, a very low level of reduced AsA, suggesting that ascorbate recycling was not an efficient system in safflower leaves under salinity. Our study demonstrates that C. tinctorius tolerates NaCl stress due to the complementary roles of powerful antioxidant molecules, such as ascorbate (for short-term treatments), glutathione (for long-term treatments), and increased SOD and GR activities.

Exogenous IAA differentially affects growth, oxidative stress and antioxidants system in Cd stressed Trigonella foenum-graecum L. seedlings: Toxicity alleviation by up-regulation of ascorbate-glutathione cycle

In the present study, effect of exogenous indole-3-acetic acid at their different levels (i.e. low; IAAL, 10µM and high; IAAH, 100µM) were studied on growth, oxidative stress biomarkers and antioxidant enzymes (SOD, POD, CAT and GST), and metabolites (AsA and GSH) as well as enzymes (APX, GR and DHAR) of ascorbate-glutathione cycle in Trigonella foenum-graecum L. seedlings grown under cadmium (Cd1, 3mgCd kg−1 soil and Cd2, 9mgCd kg−1 soil) stress. Cadmium (Cd) at both doses caused reduction in growth which was correlated with enhanced lipid peroxidation and damage to membrane as a result of excess accumulation of O2•− and H2O2. Cd also enhanced the oxidation of AsA and GSH to DHA and GSSG, respectively which give a clear sign of oxidative stress, despite of accelerated activity of enzymatic antioxidants: SOD, CAT, POD, GST as well as APX, DHAR (except in Cd2 stress) and GR. Exogenous application of IAAL resulted further rise in the activities of these enzymes, and maintained the redox status (> ratios: AsA/DHA and GSH/GSSG) of cells. The maintained redox status of cells under IAAL treatment declined the level of ROS in Cd1 and Cd2 treated seedlings thereby alleviated the Cd toxicity and this effect was more pronounced under Cd1 stress. Contrary to this, exogenous IAAH suppressed the activity of DHAR and GR and disturbed the redox status (< ratios: AsA/DHA and GSH/GSSG) of cells, hence excess accumulation of ROS further aggravated the Cd induced damage. Thus, overall results suggest that IAA at low (IAAL) and high (IAAH) doses affected the Cd toxicity differently by regulating the ascorbate-glutathione cycle as well as activity of other antioxidants in Trigonella seedlings.

Oxidative Metabolism of Rye (Secale cereale L.) after Short Term Exposure to Aluminum: Uncovering the Glutathione-Ascorbate Redox Network.

One of the major limitations to plant growth and yield in acidic soils is the prevalence of soluble aluminum ions (Al3+) in the soil solution, which can irreversible damage the root apex cells. Nonetheless, many Al-tolerant species overcome Al toxicity and are well-adapted to acidic soils, being able to complete their life cycle under such stressful conditions. At this point, the complex physiological and biochemical processes inherent to Al tolerance remain unclear, especially in what concerns the behavior of antioxidant enzymes and stress indicators at early plant development. Since rye (Secale cereale L.), is considered the most Al-tolerant cereal, in this study we resort to seedlings of two genotypes with different Al sensitivities in order to evaluate their oxidative metabolism after short term Al exposure. Al-induced toxicity and antioxidant responses were dependent on rye genotype, organ and exposure period. Al affected biomass production and membrane integrity in roots and leaves of the sensitive (RioDeva) genotype. Catalase was the primary enzyme involved in H2O2 detoxification in the tolerant (Beira) genotype, while in RioDeva this task was mainly performed by GPX and POX. Evaluation of the enzymatic and non-enzymatic components of the ascorbate–glutathione cycle, as well the oxalate content, revealed that Beira genotype coped with Al stress by converting DHA into oxalate and tartarate, which posteriorly may bind to Al forming non-toxic chelates. In contrast, RioDeva genotype used a much more ineffective strategy which passed through ascorbate regeneration. So, remarkable differences between MDHAR and DHAR activities appear to be the key for a higher Al tolerance.

Expression Patterns of Genes Involved in Ascorbate-Glutathione Cycle in Aphid-Infested Maize (Zea mays L.) Seedlings.

Reduced forms of ascorbate (AsA) and glutathione (GSH) are among the most important non-enzymatic foliar antioxidants in maize (Zea mays L.). The survey was aimed to evaluate impact of bird cherry-oat aphid (Rhopalosiphum padi L.) or grain aphid (Sitobion avenae F.) herbivory on expression of genes related to ascorbate-glutathione (AsA-GSH) cycle in seedlings of six maize varieties (Ambrozja, Nana, Tasty Sweet, Touran, Waza, Złota Karłowa), differing in resistance to the cereal aphids. Relative expression of sixteen maize genes encoding isoenzymes of ascorbate peroxidase (APX1, APX2, APX3, APX4, APX5, APX6, APX7), monodehydroascorbate reductase (MDHAR1, MDHAR2, MDHAR3, MDHAR4), dehydroascorbate reductase (DHAR1, DHAR2, DHAR3) and glutathione reductase (GR1, GR2) was quantified. Furthermore, effect of hemipterans’ attack on activity of APX, MDHAR, DHAR and GR enzymes, and the content of reduced and oxidized ascorbate and glutathione in maize plants were assessed. Seedling leaves of more resistant Z. mays varieties responded higher elevations in abundance of target transcripts. In addition, earlier and stronger aphid-triggered changes in activity of APX, MDHAR, DHAR and GR enzymes, and greater modulations in amount of the analyzed antioxidative metabolites were detected in foliar tissues of highly resistant Ambrozja genotype in relation to susceptible Tasty Sweet plants.

Effects of 24-Epibrassinolide on Antioxidant System and Expression of Drought-tolerance Relative Genes in Pepper Seedlings under Drought Stress

We studied the effects of exogenous 24-epibrassinolide( EBR) on H2O2 and MDA content,antioxidant enzymes activities,and the expression of drought-tolerance relative genes in pepper( Capsicum annuum L.) under drought stress. The results showed that 0. 1 μmol · L- 1EBR induced H2O2 producing slightly,and significantly promoted the activities of SOD,APX,CAT,DHAR,MDAR and GR in leaves of pepper. While EBR significantly increased antioxidant enzymes activities,and alleviated H2O2 and MDA content in leaves of pepper under drought stress. EBR also induced the expression of antioxidant enzymes( c APX and MDAR) and transcription factors( WRKY3,WRKY6 and MYB) genes. It was considered that the suitable exogenous EBR( 0. 1 μmol·L- 1) enhanced drought tolerance in pepper seedling maybe through induction of drought-tolerance relative genes expression and activations of antioxidative enzymes,and H2O2 signal was involved in EBR-induced drought-tolerance relative genes expression.

Molecular Approach Coupled with Biochemical Attributes to Elucidate the Presence of DYMV in Leaf Samples of Lablab purpureus. L Genotypes.

A laboratory study was delineated to ascertain the impact and the extent of Dolichos yellow mosaic virus (DYMV) on biochemical constituents and various enzyme levels in the leaves of hyacinth bean. DYMV-infected leaves of all the genotypes used in the study revealed significant and consistent changes in activities of CAT, APX, PPO, DHAR, and MDHAR paralleled with a compelling hike in proline levels. Unlike that in non-infected leaves of the genotypes VRSEM-301 and VRSEM-749, VRSEM-894 and VRSEM-855, the enzyme level did not alter much which extended equally with increased phenolics, suggesting a well-coordinated generation of free radicals thereby suppressing oxidative stress in the latter. The genotypes were also evaluated at molecular level for elucidating the presence of the virus by using five sets of primer pairs. Two primers viz., DAC1 and DAC2 witnessed the presence of the virus in both non-infected and infected leaves. The difference in the appearance and/or disappearance of bands according to non-infected to infect reverberates the variation between genotypes in defense against infection.