Methyl jasmonate-induced antioxidant defence in root apoplast from sunflower seedlings

We have investigated the physiological functions of the rapid generation of reactive oxygen species (ROS) and the implication of the antioxidant enzymes in the apoplast and symplast of roots of sunflower (Helianthus annuus L.) seedlings exposed to methyl jasmonate (MeJA, 50 μM). MeJA-elicited roots showed a fast increase in ROS content, followed by a marked increase in the activity of H₂O₂-scavenging enzymes, guaiacol peroxidase (GPX), ascorbate peroxidase (APX) and catalase (CAT). The mechanisms responsible for MeJA-induced H₂O₂ accumulation was investigated further by studying both the production and scavenging of H₂O₂ in the extracellular matrix. Peroxidases active against (2,2′-azino-bis-[3-ethylbenzthiazoline-6-sulfonic acid], ABTS) and guaiacol were found in the apoplastic fluid, and proved to be ionically and covalently associated with sunflower cell walls, although only the peroxidase activities of the soluble apoplastic fractions and those ionically linked to the cell wall were correlated with the accumulation of the H₂O₂ detected. The results indicated that H₂O₂ accumulation is a complex and highly regulated event requiring the time-dependent stimulation and down-regulation of differently located enzymes, some of which are involved in H₂O₂ generation and degradation. It is concluded that exogenous MeJA may be involved in the oxidative stress processes by regulating antioxidant enzyme activities.     

Nickel-induced Inhibition of Wheat Root Growth is Related to H2O2 Production, but not to Lipid Peroxidation

Effects of exogenous nickel (Ni: 10 and 200 μM) on growth, mitotic activity, Ni accumulation, H₂O₂ content and lipid peroxidation as well as the activities of various antioxidative enzymes, such as superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX) and glutathione peroxidase (GSH-Px) were investigated in wheat roots. A considerable Ni accumulation in the roots occurred at both the concentrations. Although Ni at 10 μM did not have any significant effect on root growth, it strongly inhibited the root growth at 200 μM. Mitotic activity in the root tips was not significantly affected by exposure of the seedlings to 10 μM Ni; however, it was almost completely inhibited at 200 μM treatment. Ni stress did not result in any significant changes in CAT and APX activities as well as lipid peroxidation. However, H₂O₂ concentration increased up to 82% over the control in the roots of seedlings exposed to 200 μM Ni. There was a significant decline in both SOD (50%) and GSH-Px (20–30%) activities in the roots when the seedlings were treated with 200 μM Ni. The results indicated that a strong inhibition of wheat root growth caused by Ni stress was not due to enhanced lipid peroxidation, but might be related to the accumulation of H₂O₂ in root tissue.     

Hydrogen Sulfide Improves the Vase Life and Quality of Cut Roses and Chrysanthemums

Recent studies indicate that hydrogen sulfide (H₂S) plays various physiological roles in plants. However, whether H₂S participates in the postharvest senescence in cut flowers remains unknown. In this study, the regulatory roles of H₂S during the senescence of cut roses (Rosa hybrida L.) and chrysanthemums (Dendranthema morifolium Ramat.) were investigated. The results showed that compared with the control (distilled water), the 50 μM sodium hydrosulfide (NaHS) treatment, a H₂S donor, extended the vase life of cut roses to 9.3 days and their flower diameter also showed an increment of 22.7% after 4 days treatment. Treatments with 30 μM NaHS significantly prolonged the vase life of cut chrysanthemums to 8.87 days and the flower diameter was 13.21% longer than the control on day 6. Additionally, results also indicated that a 30 or 50 μM NaHS treatment effectively decreased the rate of fresh weight changes and O²⁻ production and H₂O₂ content, increased the levels of soluble sugar, soluble protein, anthocyanin and carotenoid, and enhanced the activities of antioxidant enzymes (superoxide dismutase, peroxidase, catalase and ascorbate peroxidase) of cut roses and chrysanthemums in comparison with the control, implying that H₂S might be involved in regulating the osmotic balance, antioxidant system and the degradation of nutrient and pigments. Altogether, H₂S at proper doses might play an important role in improving the longevity and quality of cut roses and chrysanthemums by maintaining water balance, reducing the degradation of pigments and nutrient and enhancing antioxidant capacity.

     

Antioxidant activity and protection of human umbilical vein endothelial cells from hydrogen peroxide-induced injury by DMC,a chalcone from buds of Cleistocalyx operculatus

The aim of this work was to study the antioxidant activity and the protective effect of 2′,4′-dihydroxy-6′-methoxy-3′,5′-dimethylchalcone (DMC), the main compound from the buds of Cleistocalyx operculatus, on human umbilical vein endothelial cells against cytotoxicity induced by H₂O₂. The antioxidant activities of DMC were measured by ABTS assay, ferric reducing antioxidant power (FRAP) and hydroxyl radical scavenging activity, and protective effects of DMC on human umbilical vein endothelial cells against cytotoxicity induced by H₂O₂ were tested. DMC was found to have high ABTS radical scavenging activity (176.5 ± 5.2 μmol trolox equivalents/500 μmol DMC) and strong ferric reducing antioxidant power (213.3 ± 5.8 μmol trolox equivalents/500 μmol DMC). In addition, DMC scavenged the hydroxyl radicals, with IC₅₀ values of 243.7 ± 6.3 μM, slightly lower than the reference antioxidant ascorbic acid (ASC). Moreover, DMC could protect the human umbilical vein endothelial cells against H₂O₂-induced cytotoxicity by decrease intracellular and extracellular ROS levels, reduction in catalase (CAT) activity and increment in malondialdehyde (MDA) level. These results suggested that DMC has the potential to be used in the therapy of oxidative damage.     

Alleviation of drought stress and the physiological mechanisms in Citrus cultivar (Huangguogan) treated with methyl jasmonate

ABSTRACT

The role of exogenous methyl jasmonate (MeJA) in alleviating drought stress was investigated on Huangguogan. Except for intercellular CO₂ concentration, MeJA had little effect on net photosynthetic rate, stomatal conductance, and transpiration rate under drought stress. Compared with drought stress, MeJA significantly alleviated the decrease of chlorophyll content. However, chlorophyll a/b ratio was significantly increased. MeJA significantly increased proline and soluble sugar contents, significantly decreased the O₂ ^?· and H₂O₂ levels, and increased SOD and POD activities. In addition, the MDA content of drought stress was the highest of all treatments. MeJA significantly reduced MDA content in drought-stressed Huangguogan leaves. Although the Ascorbic acid (AsA) contents of 500 and 1000 mg L^?1 MeJA treatments were lower than that of 250 mg L^?1 MeJA, but all concentration of MeJA treatments delayed the decline of AsA content. Therefore, MeJA could induce drought stress tolerance by increasing the osmotic adjustment substances and antioxidant activities.     

Strigolactone and Methyl Jasmonate-Induced Antioxidant Defense and the Composition Alterations of Different Active Compounds in Dracocephalum kotschyi Boiss Under Drought Stress

Strigolactone (SL) and methyl jasmonate (MeJA) are one of the most important plant hormones that exert biological activity in plant responses to environmental stresses. Considering the undetected role of SL in drought tolerance and essential oil yield of medicinal plants as well as conceivable interaction among MeJA and SL, a factorial experiment was performed as a complete randomized design with three replications. Experimental factors including two irrigation regimes such as irrigation to 80% field capacity (control) and 40% field capacity (drought stress) and spraying treatments include MeJA (0 and 0.5 mM) and SL (0 and 10 μM) were applied. Treatment of plants with SL and MeJA resulted in higher tolerance to drought stress due to higher fresh and dry weights as well as lower electrolyte leakage, malondialdehyde, H₂O₂, total phenol content, total antioxidant activity and antioxidant power assay. The most important essential oil constituents of D. kotschyi included geranyl acetate (41.1–48.6%), α-pinene (16.2–18.9%), geranial (7.9–10.1%), limonene (5.5–7.0%), neral (3.5–4.1%), methyl geranate (2.3–3.3%) and geraniol (1–2.2%), the least of which was found in non-MeJA- and SL-treated plants under drought and the highest in MeJA- and SL-treated plants under drought stress. Drought tolerance of D. kotschyi became more intense and the amount of essential oil components of water stressed plants was the highest (99.2%) when these plant hormones were used together. These results suggest a cross-link between MeJA and SL in improving drought resistance and optimizing the production of essential oil of D. kotschyi.

     

Asymmetric effects of litter removal and litter addition on the structure and function of soil microbial communities in a managed pine forest

Aims

The effect of different MeJA doses applied prior to or simultaneously with toxic Al on biochemical and physiological properties of Vaccinium corymbosum cultivars with contrasting Al resistance was studied.

Methods

Legacy (Al-resistant) and Bluegold (Al-sensitive) plants were treated with and without toxic Al under controlled conditions: a) without Al and MeJA, b) 100 μM Al, c) 100 μM Al + 5 μM MeJA, d) 100 μM Al + 10 μM MeJA and e) 100 μM Al + 50 μM MeJA. MeJA was applied to leaves 24 h prior to or simultaneously with Al in nutrient solution. After 48 h, Al-concentration, lipid peroxidation (LP), H₂O₂, antioxidant activity, total phenols, total flavonoids, phenolic compounds and superoxide dismutase activity (SOD) of plant organs were analyzed.

Results

Al-concentrations increased with Al-treatment in both cultivars, being Al, LP and H₂O₂ concentrations reduced with low simultaneous MeJA application. Higher MeJA doses induced more oxidative damage than the lowest. Legacy increased mainly non-enzymatic compounds, whereas Bluegold increased SOD activity to counteract Al³⁺.

Conclusions

Low MeJA doses applied simultaneously with Al³⁺ increased Al-resistance in Legacy by increasing phenolic compounds, while Bluegold reduced oxidative damage through increment of SOD activity, suggesting a diminution of its Al-sensitivity. Higher MeJA doses could be potentially toxic. Studies are needed to determine the molecular mechanisms involved in the protective MeJA effect against Al-toxicity.

     

The role of jasmonic acid in root mitochondria disruption

Methyl jasmonate (MeJA) produces an important reduction in the accumulation of proteins related to energy metabolism. The treatment of hairy roots (HR) with MeJA increased the accumulation of H₂O₂ during the first 48 h and this H₂O₂ accumulation was also observed in isolated mitochondria. Peroxidase and catalase activities decreased in the presence of MeJA, and this decrease directly correlated with the increase of H₂O₂ in HR treated with MeJA. This suggests that the H₂O₂ burst due to MeJA is the initial response to mitochondria disruption in the roots.     

Modulation of antioxidant enzyme activities and metabolites ratios by nitric oxide in short-term salt stressed soybean root nodules

Several abiotic factors cause molecular damage to plants either directly or through the accumulation of reactive oxygen species such as hydrogen peroxide (H₂O₂). We investigated if application of nitric oxide (NO) donor 2,2′-(hydroxynitrosohydrazono) bis-ethanimine (DETA/NO) could reduce the toxic effect resulting from short-term salt stress. Salt treatment (150 mM NaCl) alone and in combination with 10 μM DETA/NO or 10 μM DETA were given to matured soybean root nodules for 24 h. Salt stress resulted in high H₂O₂ level and lipid peroxidation while application of DETA/NO effectively reduced H₂O₂ level and prevented lipid peroxidation in the soybean root nodules. NO treatment increased the activities of ascorbate peroxidase and dehydroascorbate reductase under salt stress. Whereas short-term salt stress reduced AsA/DHAsA and GSH/GSSG ratios, application of the NO donor resulted in an increase of the reduced form of the antioxidant metabolites thus increasing the AsA/DHAsA and GSH/GSSG ratios. Our data suggests a protective role of NO against salt stress.     

Peroxide reduction by a metal-dependent catalase in Nostoc punctiforme (cyanobacteria)

This study investigated the role of a novel metal-dependent catalase (Npun_R4582) that reduces hydrogen peroxide in the cyanobacterium Nostoc punctiforme. Quantitative real-time PCR showed that npun_R4582 relative mRNA levels were upregulated by over 16-fold in cells treated with either 2 μM added Co, 0.5 μM added Cu, 500 μM Mn, 1 μM Ni, or 18 μM Zn. For cells treated with 60 μM H₂O₂, no significant alteration in Npun_R4582 relative mRNA levels was detected, while in cells treated with Co, Cu, Mn, Ni, or Zn and 60 μM peroxide, relative mRNA levels were generally above control or peroxide only treated cells. Disruption or overexpression of npun_R4582 altered sensitivity to cells exposed to 60 μM H₂O₂ and metals for treatments beyond the highest viable concentrations, or in a mixed metal solution for Npun_R4582⁻ cells. Moreover, overexpression of npun_R4582 increased cellular peroxidase activity in comparison with wild-type and Npun_R4582⁻ cells, and reduced peroxide levels by over 50%. The addition of cobalt, manganese, nickel, and zinc increased the capacity of Npun_R4582 to reduce the rate or total levels of peroxide produced by cells growing under photooxidative conditions. The work presented confirms the function of NpunR4582 as a catalase and provides insights as to how cells reduce potentially lethal peroxide levels produced by photosynthesis. The findings also show how trace elements play crucial roles as enzymatic cofactors and how the role of Npun_R4582 in hydrogen peroxide breakdown is dependent on the type of metal and the level available to cells.

     

PLC1 and H2O2 Mediated the Allelopathic Effect of Oridonin on Root Growth in Arabidopsis thaliana

Oridonin is a diterpenoid isolated from medicinal herb Rabdosia rubescens (Hemsl.) Hara (Lamiaceae), which has an allelopathic effect on plants. Phospholipase C (PLC1) and hydrogen peroxide (H₂O₂) are involved in many biotic or abiotic stress responses. Using the 16-day-old seedlings of Arabidopsis thaliana ecotype (WT) and PLC1-deficient mutant (plc1) as materials (treated with 10 μM or 60 μM oridonin for 72 h), the effect of oridonin on root growth regulating by PLC1 and H₂O₂ was investigated. The results showed that the promoting of root growth was about 6.9% at 10 μmol L^?1 oridonin and the inhibiting of root growth was about 19.73% at 60 μmol L^?1 oridonin in WT, the inhibiting of root growth was about 10.5% and 41.2% at 10 mol L^?1 and 60 mol L^?1 oridonin, respectively, in plc1. The expression of ARR1, ARR12, and AHK3 was promoted at low concentrations of oridonin and inhibited at high concentrations in WT, whereas the expression of ARR1 and ARR12 was inhibited with the increase of oridonin concentration in plc1. This suggested that PLC1 was involved in the root growth regulation of oridonin. H₂O₂ was promoted by oridonin with concentration dependence pattern in root cells. Oridonin increased the activity of antioxidant enzymes in both WT and plc1, but the activity of antioxidant enzymes in plc1 was lower than WT. This indicated that PLC1 involved in the activation of antioxidant enzymes promoted by the oridonin. Exogenous CaCl₂ facilitated the accumulation of H₂O₂ in both WT and plc1. And the H₂O₂ of WT was obviously higher than that of plc1. The root growth of WT was inhibited by CaCl₂ with the increase of oridonin. However, there is no effect of CaCl₂ on the root growth in plc1. This reflected that PLC1 positively involved in the regulation of Ca²⁺ on the H₂O₂ and the inhibition effect of Ca²⁺ on the root growth under oridonin treatment. PA promoted the H₂O₂ and suppressed the root growth under oridonin treatment in both WT and plc1. In plc1, PA facilitated the root growth with no oridonin and inhibited the root growth with the increase of oridonin. This reflected that PLC1 positively regulated the promotion effect of PA on the root growth under high oridonin treatment. PLC1 mediated oridonin (10 and 60 mol L^?1) to regulate H₂O₂ levels in A. thaliana seedlings, thereby regulating root tip cell morphology and mitosis. These results demonstrated that PLC1 mediated the low-promotion and high-inhibition effect of oridonin on the root growth in A. thaliana by regulating the concentrations of Ca²⁺ and PA, and further affecting the intracellular H₂O₂ level.

     

Protective effects of a wheat germ peptide (RVF) against H2O2-induced oxidative stress in human neuroblastoma cells

RVF (Arg-Val-Phe), a peptide derived from wheat germ, shows antioxidant properties. Here, the neuroprotective efficacies of RVF were investigated in human neuroblastoma cells (SH-SY5Y) that were pretreated with RVF (150–250 μM, 4 h) and exposed to H₂O₂ (200 μM). RVF increased viable cell numbers by 37 % and reduced the release of lactate dehydrogenase. Pretreatment with RVF also inhibited H₂O₂-induced accumulation of reactive oxygen species and maintained the mitochondrial transmembrane potential as well as preventing intracellular Ca²⁺ dysregulation during H₂O₂ exposure. Furthermore, pretreatment with RVF increased the Bcl-2/Bax ratio and blocked cleavage poly(ADP-ribose) polymerase by inhibiting caspase-3 activation, thus decreasing apoptosis.     

Nitric oxide interacts with mitochondrial complex III producing antimycin-like effects

The effect of NO between cytochromes b and c of the mitochondrial respiratory chain were studied using submitochondrial particles (SMP) from bovine heart and GSNO and SPER-NO as NO sources. Succinate-cytochrome c reductase (complex II-III) activity (222±4 nmol/min. mg protein) was inhibited by 51% in the presence of 500 μM GSNO and by 48% in the presence of 30 μM SPER-NO, in both cases at ~1.25 μM NO. Neither GSNO nor SPER-NO were able to inhibit succinate-Q reductase activity (complex II; 220±9 nmol/min. mg protein), showing that NO affects complex III. Complex II-III activity was decreased (36%) when SMP were incubated with l-arginine and mtNOS cofactors, indicating that this effect is also produced by endogenous NO. GSNO (500 μM) reduced cytochrome b₅₆₂ by 71%, in an [O₂] independent manner. Hyperbolic increases in O₂^•- (up to 1.3±0.1 nmol/min. mg protein) and H₂O₂ (up to 0.64±0.05 nmol/min. mg protein) productions were observed with a maximal effect at 500 μM GSNO. The O₂^•-/H₂O₂ ratio was 1.98 in accordance with the stoichiometry of the O₂^•- disproportionation. Moreover, H₂O₂ production was increased by 72–74% when heart coupled mitochondria were exposed to 500 μM GSNO or 30 μM SPER-NO. SMP incubated in the presence of succinate showed an EPR signal (g=1.99) compatible with a stable semiquinone. This EPR signal was increased not only by antimycin but also by GSNO and SPER-NO. These signals were not modified under N₂ atmosphere, indicating that they are not a consequence to the effect of NOx species on complex III area. These results show that NO interacts with ubiquinone-cytochrome b area producing antimycin-like effects. This behaviour comprises the inhibition of electron transfer, the interruption of the oxidation of cytochromes b, and the enhancement of [UQH^•]_ss which, in turn, leads to an increase in O₂^•- and H₂O₂ mitochondrial production rates.     

Exogenous Abscisic Acid Alleviates Cadmium Toxicity by Restricting Cd2+ Influx in Populus euphratica Cells

Abscisic acid (ABA), a widely known phytohormone involved in the plant response to abiotic stress, plays a vital role in mitigating Cd²⁺ toxicity in herbaceous species. However, the role of ABA in ameliorating Cd²⁺ toxicity in woody species is largely unknown. In the present study, we investigated ABA restriction on Cd²⁺ uptake and the relevance to Cd²⁺ stress alleviation in Cd²⁺-hypersensitive Populus euphratica. ABA (5 μM) markedly improved cell viability and growth but reduced membrane permeability in CdCl₂ (100 μM)-stressed P. euphratica cells. Moreover, ABA significantly increased the activity of the antioxidant enzymes catalase (CAT), superoxide dismutase (SOD), and ascorbate peroxidase (APX), contributing to the scavenging of Cd²⁺-elicited H₂O₂ within P. euphratica cells during the period of CdCl₂ exposure (100 μM, 24–72 h). ABA alleviation of Cd²⁺ toxicity was mainly the result of ABA restriction of Cd²⁺ uptake under Cd²⁺ stress. Steady-state and transient flux recordings showed that ABA inhibited Cd²⁺ entry into Cd²⁺-shocked (100 μM, 30 min) and short-term-stressed P. euphratica cells (100 μM, 24–72 h). Non-invasive micro-test technique data showed that H₂O₂ (3 mM) stimulated the Cd²⁺-elicited Cd²⁺ influx but that the plasma membrane (PM) Ca²⁺ channel inhibitor LaCl₃ blocked it, suggesting that the Cd²⁺ influx was through PM Ca²⁺-permeable channels. These results suggested that ABA up-regulated antioxidant enzyme activity in Cd²⁺-stressed P. euphratica and that these enzymes scavenged the Cd²⁺-elicited H₂O₂ within cells. The entry of Cd²⁺ through the H₂O₂-mediated Ca²⁺-permeable channels was subsequently restricted; thus, Cd²⁺ buildup and toxicity were reduced in the Cd²⁺-hypersensitive species, P. euphratica.

     

Effects of Menadione, Hydrogen Peroxide, and Quercetin on Apoptosis and Delayed Luminescence of Human Leukemia Jurkat T-Cells

Menadione (MD) is an effective cytotoxic drug able to produce intracellularly large amounts of superoxide anion. Quercetin (QC), a widely distributed bioflavonoid, can exert both antioxidant and pro-oxidant effects and is known to specifically inhibit cell proliferation and induce apoptosis in different cancer cell types. We have investigated the relation between delayed luminescence (DL) induced by UV-laser excitation and the effects of MD, hydrogen peroxide, and QC on apoptosis and cell cycle in human leukemia Jurkat T-cells. Treatments with 500 μM H₂O₂ and 250 μM MD for 20 min produced 66.0 ± 4.9 and 46.4 ± 8.6% apoptotic cell fractions, respectively. Long-term (24 h) pre-exposure to 5 μM, but not 0.5 μM QC enhanced apoptosis induced by MD, whereas short-term (1 h) pre-incubation with 10 μM QC offered 50% protection against H₂O₂-induced apoptosis, but potentiated apoptosis induced by MD. Since physiological levels of QC in the blood are normally less than 10 μM, these data can provide relevant information regarding the benefits of flavonoid-combined treatments of leukemia. All the three drugs exerted significant effects on DL. Our data are consistent with (1) the involvement of Complex I of the mitochondrial respiratory chain as an important source of delayed light emission on the 10 μs–10 ms scale, (2) the ability of superoxide anions to quench DL on the 100 μs–10 ms scale, probably via inhibition of reverse electron transfer at the Fe/S centers in Complex I, and (3) the relative insensitivity of DL to intracellular OH^? and H₂O₂ levels.     

Redox-related peroxidative responses evoked by methyl-jasmonate in axenically cultured aeroponic sunflower (Helianthus annuus L.) seedling roots

Summary.  Methyl-jasmonate (MeJA) has been proposed to be involved in the evocation of defense reactions, as the oxidative burst in plants, substituting the elicitors or enhancing their effect. 48 h dark- and sterilely cultured (axenic) aeroponic sunflower seedling roots excised and treated with different concentrations of MeJA showed a strong and quick depression of the H⁺ efflux rate, 1.80 μM MeJA totally stopping it for approximately 90 min and then reinitiating it again at a lower rate than controls. These results were wholly similar to those obtained with nonsterilely cultured roots and have been interpreted as mainly based on H⁺ consumption for O₂ ^•− dismutation to H₂O₂. Also K⁺ influx was strongly depressed by MeJA, even transitorily reverting to K⁺ efflux. These results were consistent with those associated to the oxidative burst in plants. MeJA induced massive H₂O₂ accumulation in the middle lamella and intercellular spaces of both the root cap cells and the inside tissues of the roots. The native acidic extracellular peroxidase activity of the intact (nonexcised) seedling roots showed a sudden enhancement (by about 52%) after 5 min of MeJA addition, maintained for approximately 15 min and then decaying again to control rates. O₂ uptake by roots gave similar results. These and other results for additions of H₂O₂ or horseradish peroxidase, diphenylene iodonium, and sodium diethyldithiocarbamate trihydrate to the reaction mixture with roots were all consistent with the hypothesis that MeJA induced an oxidative burst, with the generation of H₂O₂ being necessary for peroxidase activity. Results with peroxidase activity of the apoplastic fluid were in accordance with those of the whole root. Finally, MeJA enhanced NADH oxidation and inhibited hexacyanoferrate(III) reduction by axenic roots, and diphenylene iodonium cancelled out these effects. Redox activities by CN⁻- preincubated roots were also studied. All these results are consistent with the hypothesis that MeJA enhanced the NAD(P)H oxidase of a redox chain linked to the oxidative burst, so enhancing the generation of O₂ ^•− and H₂O₂, O₂ uptake, and peroxidase activity by roots. Received July 12, 2002; accepted October 2, 2002; published online May 21, 2003 RID="*"     

Salicylic Acid Confers Salt Tolerance in Giant Juncao Through Modulation of Redox Homeostasis,Ionic Flux,and Bioactive Compounds: An Ionomics and Metabolomic Perspective of Induced Tolerance Responses

We investigated the stimulatory and/or inhibitory role of exogenous SA in alleviating the salt stress (250, 500 mM NaCl) in Pennisetum giganteum (Giant Juncao) through coordinated induction of redox homeostasis, ionic flux, and bioactive compounds. Salt stress radically impaired root and shoot (growth, fresh, and dry biomass as well as tolerance indices), leaf relative water content, and leaf chlorophyll a/b ratio of Juncao due to higher Na⁺ and Cl^? accumulation followed by H₂O₂ generation, lipid peroxidation (MDA contents), and electrolyte leakage. However, the innate defense response of Juncao counteracted salt-induced damages by osmolytes accumulation combined with orchestrating antioxidants and ionic homeostasis mechanisms. Furthermore, the application of SA had an incremental impact on the development and productivity of high-salinity-exposed Juncao plants by increasing root length, plant biomass, tolerance indices, chlorophyll a/b ratio, and protein contents. Furthermore, SA treatment considerably decreased Na⁺ and Cl^? toxicity by orchestrating antioxidant enzymes, ion transport, and secondary metabolism. Notably, the application of SA substantially mitigated the adverse effects of high salinity concentration (500 mM NaCl), owing to the simultaneous upregulation in enzymatic and non-enzymatic antioxidants, nutrient ion flux, alongside chlorogenic acid production. Thus, we concluded that SA enhanced the tolerance capability of Juncao plants in a NaCl concentration-dependent manner. The findings of this study will enable environmentalists and pharmacologists to gain dual farm-level benefits, including animal therapeutics and restoration of salinized soils for arable purposes.

     

Effect of acetone extract from stem bark of Acacia species (A. dealbata,A. ferruginea and A. leucophloea) on antioxidant enzymes status in hydrogen peroxide-induced HepG2 cells

Acacia species are multipurpose trees, widely used in the traditional systems of medicine to treat various ailments. The major objective of the present study was to determine the gene expression of enzymatic antioxidants by acetone extract from the stem bark of three Acacia species (Acacia dealbata, Acacia ferruginea and Acacia leucophloea) in hydrogen peroxide (H₂O₂)-induced human hepatoma (HepG2) cells. The expression of antioxidant enzymes such as superoxide dismutase containing copper–zinc (CuZnSOD)/manganese (MnSOD), catalase (CAT) and glutathione peroxidase (GPx) in HepG2 cells was evaluated by real-time PCR. The results of antioxidant enzyme expression in real-time PCR study revealed that the H₂O₂ (200 μM) challenged HepG2 cells reduced the expression of enzymes such as SOD, GPx and CAT. However, the cells pre-treated with acetone extracts of all the three Acacia species significantly (P > 0.05) up-regulated the expression of antioxidant enzymes in a concentration dependent manner (25, 50 and 75 μg/mL). In conclusion, the findings of our study demonstrated that the acetone extract of Acacia species effectively inhibited H₂O₂ mediated oxidative stress and may be useful as a therapeutic agent in preventing oxidative stress mediated diseases.     

Effects of root and foliar applications of exogenous NO on alleviating cadmium toxicity in lettuce seedlings

The effects of sodium nitroprusside (SNP, a donor of NO) on cadmium (Cd) toxicity in lettuce seedlings were studied. SNP was added into hydroponic systems or sprayed directly on the leaves of plants grown with and without Cd. Excess supply of Cd (100 μM) caused growth inhibition, dramatically increased Cd accumulation in both leaves and roots, and inhibited the absorption of Ca, Mg, Fe and Cu. Excess Cd also decreased activities of superoxide dismutase peroxidase and catalase in leaves and roots, and increased the accumulation of superoxide anion (O ₂ ^·? ), hydrogen peroxide (H₂O₂) and malondialdehyde (MDA). Root or foliar applications of exogenous NO alleviated Cd-induced growth suppression, especially root application of 250 μM SNP and foliar addition of 500 μM SNP. Addition of SNP promoted the chlorophyll synthesis suggesting that the photosynthesis was up-regulated. Exogenous NO increased Cd-decreased activities of antioxidant enzymes and markedly diminished Cd-induced reactive oxygen species (ROS) and MDA accumulation. Moreover, the absorption of Ca, Mg, Fe and Cu was increased, indicating that exogenous NO stimulated H⁺-ATPase activity to promote sequestration or uptake of ions. In addition, exogenous NO also inhibited Cd transfer from roots to shoots, which may indicate that Cd retention in roots induced by NO plays a significant role in Cd tolerance in lettuce seedlings. These data suggest that under Cd stress, exogenous NO improves photosynthesis by increasing chlorophyll synthesis, protects lettuce seedlings against oxidative damage by scavenging ROS, helps to maintain the uptake of nutrient elements, and inhibits Cd transferred to shoots effectively.     

Protective effect of vanillic acid in hydrogen peroxide-induced oxidative stress in D.Mel-2 cell line

The overproduction of reactive oxygen species (ROS) causes oxidative stress, such as Hydrogen peroxide (H₂O₂). Acute oxidative stress is one of the main reasons for cell death. In this study, the antioxidant properties of vanillic acid- a polyphenolic compound was evaluated. Therefore, this study aims to check the effectiveness of vanillic acid in H₂O₂-induced oxidative stress in D. Mel-2 cell line. The efficacy was determined by biochemical tests to check the ROS production. The cytotoxicity of H₂O₂ and vanillic acid was checked by MTT assay. The DNA fragmentation was visualized by gel electrophoresis. Protein biomarkers of oxidative stress were analyzed by western blotting. The results depict a promising antioxidant effect of vanillic acid. The IC₅₀ value of vanillic acid and H₂O₂ was found 250 μg/ml and 125 μg/ml, respectively. The catalase activity, SOF, GPx, and PC was seen less in H₂O₂ treated group compared with the control and vanillic acid treated group. However, the TBRAS activity was hight in H₂O₂ treated group. The effect of H₂O₂ on DNA fragmentation was high as compared with vanillic acid-treated cells. The protein expression of Hsp70, IL-6 and iNOS was seen significant in a vanillic acid-treated group as compared with H₂O₂ treated group. These results reinforce that at low concentration, vanillic acid could be used as an antioxidant agent in the food and pharmaceutical industries.