Superoxide-Dismutase Deficient Mutants in Common Beans (Phaseolus vulgaris L.): Genetic Control, Differential Expressions of Isozymes, and Sensitivity to Arsenic
28 Aug 2013-BioMed Research International (Hindawi Publishing Corporation)-Vol. 2013, pp 782450-782450
TL;DR: Gene expressions using qRT PCR confirmed higher expressions of Cu/Zn SOD transcripts in both mutants and the absence of Fe SOD in sodPv 1 and Mn S OD in SodPv 2 and ROS-imaging study revealed overaccumulation of both superoxides and H2O2 in leaves of double mutant.
Abstract: Two common bean (Phaseolus vulgaris L.) mutants, sodPv 1 and sodPv 2, exhibiting foliar superoxide dismutase (SOD) activity of only 25% and 40% of their mother control (MC) cv. VL 63 were isolated in EMS-mutagenized (0.15%, 8 h) M2 progeny. Native-PAGE analysis revealed occurrence of Mn SOD, Fe SOD, Cu/Zn SOD I and Cu/Zn SOD II isozymes in MC, while Fe SOD, and Mn SOD were not formed in sodPv 1 and sodPv 2 leaves, respectively. In-gel activity of individual isozymes differed significantly among the parents. SOD deficiency is inherited as recessive mutations, controlled by two different nonallelic loci. Gene expressions using qRT PCR confirmed higher expressions of Cu/Zn SOD transcripts in both mutants and the absence of Fe SOD in sodPv 1 and Mn SOD in sodPv 2. In 50 μM arsenic, Cu/Zn SODs genes were further upregulated but other isoforms downregulated in the two mutants, maintaining SOD activity in its control level. In an F2 double mutants of sodPv 1 × sodPv 2, no Fe SOD, and Mn SOD expressions were detectable, while both Cu/Zn SODs are down-regulated and arsenic-induced leaf necrosis appeared. In contrast to both mutants, ROS-imaging study revealed overaccumulation of both superoxides and H2O2 in leaves of double mutant.
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01 Jan 2016
TL;DR: The redox-dependent modification of sensitive signalling proteins is proposed as a key mode of redox signal transmission, which plays a key role in the adaptive response to the adverse environment.
Abstract: Plants are frequently exposed to different stressful factors, both of biotic or abiotic nature, which limit their growth and productivity. To survive under stress conditions, plants must activate stress-specific signalling pathways, which finally lead to morphological, physiological, and biochemical changes that allow to adapt to the adverse environment. Cellular redox homeostasis, determined by a complex interplay between pathways that produce and scavenge reactive oxygen species (ROS), plays a key role in the adaptive response. Each deviation in the cellular redox state, due to an imbalance of ROS production and/or scavenging, is indicative of environmental disturbance and works as a signal. Under stress conditions, different ROS are produced in many cell compartments. Plants have very proficient, versatile and flexible antioxidant machinery, which comprises enzymes and metabolites with distinct biochemical properties and distinct sub-cellular localization. The antioxidant systems play a key role in the control of redox homeostasis, determining either the extent or the specificity of ROS signals and the downstream redox-dependent responses. Redox signalling is responsive to a number of environmental cues, and the complex and dynamic pathways of redox regulation occur in different cell compartments. The redox-dependent modification of sensitive signalling proteins is proposed as a key mode of redox signal transmission. Each redox-dependent interaction is opportunely regulated by a restricted environment, whose change transfers the complex system of information and influences the plant response to external changes.
57 citations
TL;DR: Results indicated coordinated response of thiol-metabolism and antioxidant defense in conferring As-tolerance in lentil, and GSH is the key point in this cascade.
Abstract: Response of sulfate transporters, thiol metabolism, and antioxidant defense system was studied in roots of two lentil (Lens culinaris Medik.) genotypes grown in arsenic (10, 25, and 40 μM As(V))-supplemented nutrient solution, and significant changes compared to control (0 μM As(V)) were observed mainly at 25 and 40 μM. In L 414, high glutathione (GSH) redox (0.8-0.9) was maintained with elevated thiol synthesis, powered by transcriptional up-regulation of LcSultr1;1 and LcSultr1;2 sulfate transporters and significant induction of LcSAT1;1 and LcSAT1;2 (serine acetyltransferase), OAS-TL (O-acetylserine(thiol)-lyase), γ-ECS (γ-glutamylcysteine synthetase), and PCS (phytochelatin synthase) genes predominantly within 12-24 h of As exposure at 25 μM and within 6-12 h at 40 μM. This thiolic potency in L 414 roots was effectively complemented by up-regulation of gene expressions and consequent enhanced activities of superoxide dismutase, ascorbate peroxidase (APX), dehydroascorbate reductase, glutathione reductase (GR), and glutathione-S-transferase (GST) isoforms at 25 and 40 μMAs, efficiently scavenging excess reactive oxygen species to prevent onset of As-induced oxidative stress and consequent inhibition of root growth in L 414. In contrast, down-regulation of vital sulfate-uptake transporters as well as entire thiol-metabolizing system and considerably low APX, GST, and GR expressions in DPL 59 not only resulted in reduced GSH redox but also led to over-accumulation of H2O2. This triggered membrane lipid peroxidations as the marks of As-induced oxidative damage. Results indicated coordinated response of thiol-metabolism and antioxidant defense in conferring As-tolerance in lentil, and GSH is the key point in this cascade.
28 citations
TL;DR: In this article, the role of the superoxide dismutase (SOD), catalase (CAT), peroxidase (POX), and APX enzymes in Salvinia molesta tolerance to AsIII was investigated.
Abstract: Antioxidant enzymes are important components in the defense against arsenic (As) stress in plants. Here, we tested the hypothesis that Salvinia molesta, an aquatic fern, counteracts the harmful arsenite (AsIII) effects by activating scavenging reactive oxygen species (ROS) enzymes. Thus, our objective was to investigate the role of the superoxide dismutase (SOD), catalase (CAT), peroxidase (POX), and ascorbate peroxidase (APX) in S. molesta tolerance to AsIII and indicate the use of this plant in remediation of contaminated water. Plants were grown in nutrient solution at pH 6.5 and exposed to 0, 5, 10, or 20 µM AsIII for 96 h (analyses of As absorption, mineral nutrient content, and relative growth rate) and for 24 h (analyses of oxidative stress indicators and enzymatic antioxidant defenses). In the floating leaves, there was a greater basal activity of the antioxidant enzymes and less accumulation of As than in submerged leaves. The submerged leaves, which function as roots in S. molesta, accumulated more As than floating leaves, and SOD and CAT activities were inhibited. Thus, there was a greater production of ROS and oxidative stress. Our results show that S. molesta presents enzymatic antioxidant defenses to alleviate AsIII toxicity and are more effectives in the floating leaves. These results are important to elucidate the AsIII tolerance mechanisms in S. molesta and the possibility of their use in contamined water phytoremediation. Additional studies exposing plants to more prolonged stress and using AsIII concentrations closer to those found in contaminated environments will confirm this claim.
21 citations
Cites background from "Superoxide-Dismutase Deficient Muta..."
...Oxidative stress is the main deleterious AsIII effect in plants (Talukdar 2013; Singh et al. 2015a; Farooq et al. 2015), although it may also inhibit the catalytic function of enzymes by binding to their sulfhydryl groups, leading to metabolic damage (Sharma 2012; Farooq et al. 2016a)....
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...The ROS increase can cause intense oxidative damage and promote plant tissue necrosis, affecting plant biomass (Talukdar and Talukdar 2013; Upadhyaya et al. 2014)....
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TL;DR: Native PAGE analysis revealed that enzyme isoforms were involved in the regulation of foliar H2O2 metabolism, the level of which was found extremely critical in determining arsenic tolerance of grass pea genotypes.
Abstract: Response of four improved grass pea (Lathyrus sativus L.) genotypes to arsenic was tested in pot experiment using 30 mg As l−1 up to 60 days of growth after commencement of treatment (DAC). Arsenic exposure significantly reduced growth and seed yield potential of vars B1 and BioL-212, but no such effect was observed in bold-seeded mutant and pod indehiscent mutant lines. Results revealed normal leaf photosynthesis and antioxidant metabolism at 20 DAC in both varieties. However, high superoxide dismutase activity coupled with low ascorbate redox and declining ascorbate peroxidase level led to abnormal rise in H2O2 content at reproductive stages (40 and 60 DAC), consequently, resulting in significantly enhanced arsenic-induced oxidative damage and physiological impediment in both varieties. By contrast, H2O2 level in both the mutants was remarkably modulated at reproductive stage (40 DAC) in a highly controlled manner by balanced action of antioxidant defense. This favored normal photosynthesis and ensured good grain yield even under prolonged arsenic exposure by effectively preventing oxidative damage to membrane in both the mutants. Native PAGE analysis revealed that enzyme isoforms were involved in the regulation of foliar H2O2 metabolism, the level of which was found extremely critical in determining arsenic tolerance of grass pea genotypes.
12 citations
28 May 2016
TL;DR: Results suggested exogenous TU stimulated the Gly and antioxidant defense in fine tune against As-induced oxidative damage in lentil genotypes, as was evident from ROS-imaging study.
Abstract: Arsenic (As) is a wide-spread toxic and carcinogenic metalloid, affecting crop productivity worldwide. Lentil, an edible grain legume, is increasingly exposed to soil arsenic contamination. However, our understandings regarding mechanistic details and mitigation strategies against arsenic toxicity in edible legume are extremely poor. Main purpose of the present study was to investigate the As-effects and its mitigation by thiourea (TU), a sulfhydryl bioregulator, in lentil. Four widely grown lentil genotypes were grown in nutrient media, supplemented with 30 μM sodium arsenate (As), As + 6.5 mM TU and As + 13 mM TU, keeping an untreated control for 10 d. As severely affected plant dry weight by accumulating in shoots and roots. However, TU application sequestered As in crop roots and prevented up-ward translocation of As. TU coordinately modulated glyoxalase system I and II (Gly I and II) and ascorbate (AsA)-glutathione (GSH) redox, and antioxidant defense enzymes in both leaves and roots of four genotypes. Elevation of Gly system prevented toxic methyl glyoxal overaccumulation whereas stimulated AsA-GSH cycle enzymes and Glutathione s-transferase and catalase effectively scavenged H 2 O 2 and prevented reactive oxygen species (ROS) -mediated onset of oxidative damage in four genotypes, as was evident from ROS-imaging study. Results suggested exogenous TU stimulated the Gly and antioxidant defense in fine tune against As-induced oxidative damage in lentil genotypes.
12 citations
Cites background or result from "Superoxide-Dismutase Deficient Muta..."
...Overproduction of superoxides and H 2 O 2 due to toxic metals/metalloids was distinctly screened by CLSM study in pea, beans, alfalfa, and lupin roots (Ortega-Villasante et al., 2005; Rodr´ıguez-Serrano et al., 2006; Talukdar and Talukdar, 2013)....
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...As-induced reduction in Chl A and Chl A/B ratio was observed in As-exposed edible legumes, cereals, and other crops but unlike the present circumstances in most of these cases carotenoid levels were not affected by As exposure (Guo et al., 2005; Talukdar and Talukdar, 2013; 2014)....
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References
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TL;DR: The results suggest that the exogenous application of NO could be advantageous against Cd toxicity, and could confer tolerance to heavy metal stress in plants.
437 citations
"Superoxide-Dismutase Deficient Muta..." refers background in this paper
...Besides As, heavy metal-dependent induction of SOD activity was also found in crops like Pisum sativum [32], Lens culinaris [34], Helianthus annuus [35], and Coffea arabica [36]....
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TL;DR: In this paper, the authors found that NO donor sodium nitroprusside (SNP) stimulates seed germination and root growth of lupin (Lupinus luteus L. cv. Ventus).
408 citations
"Superoxide-Dismutase Deficient Muta..." refers background in this paper
...Overproduction of superoxides and H 2 O 2 due to toxic metals/metalloids was distinctly screened by CLSM study in pea, Medicago sativa, and Lupinus luteus roots [32, 46, 47]....
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TL;DR: Both Cd and Hg not only compromised severely the cellular redox homeostasis, but also caused cell necrosis, indicating that the depletion of the GSH/hGSH pool was not sufficient to promote cell death, and that other phytotoxic mechanisms might be involved.
Abstract: Alfalfa (Medicago sativa) plantlets were exposed to Cd or Hg to study the kinetics of diverse stress indexes. In the so-called beaker-size hydroponic system, plantlets were grown in 30 microM of Cd or Hg for 7 d. Oxidative stress took place and increased over time, a linear response being observed with Cd but not with Hg. To improve the sensitivity of the stress assays used, a micro-assay system, in which seedlings were exposed for 24 h, was developed. Phytotoxicity of metals, quantified as growth inhibition, was observed well before there was any change in the non-protein thiol tissue concentration. When measured with conventional techniques, oxidative stress indexes did not show significant variation. To trace early and small plant responses to Cd and Hg, a microscopic analysis with novel fluorescent dyes, which had not yet been exploited to any significant extent for use in plants, was conducted. These fluorescent probes, which allowed minute cellular responses to 0, 3, 10, and 30 microM of both metals to be visualized in the roots of the alfalfa seedlings, were: (i) 2',7'-dichlorofluorescin diacetate that labels peroxides; (ii) monochlorobimane that stains reduced glutathione/homoglutathione (GSH/hGSH); and (iii) propidium iodide that marks nuclei of dead cells. Oxidative stress and cell death increased after exposure for 6-24 h to Cd and Hg, but labelling of GSH/hGSH decreased acutely. This diminution might be the result of direct interaction of GSH/hGSH with both Cd and Hg, as inferred from an in vitro conjugation assay. Therefore, both Cd and Hg not only compromised severely the cellular redox homeostasis, but also caused cell necrosis. In plants treated with 1 mM L-buthionine sulphoximine, a potent inhibitor of GSH/hGSH synthesis, only the oxidative stress symptoms appeared, indicating that the depletion of the GSH/hGSH pool was not sufficient to promote cell death, and that other phytotoxic mechanisms might be involved.
290 citations
"Superoxide-Dismutase Deficient Muta..." refers background in this paper
...Overproduction of superoxides and H 2 O 2 due to toxic metals/metalloids was distinctly screened by CLSM study in pea, Medicago sativa, and Lupinus luteus roots [32, 46, 47]....
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TL;DR: In this paper, the effect of As (10.0 and 50.0 μM) on seedling growth, root anatomy, lipid peroxidation (malondialdehyde and conjugated dienes), electrolyte leakage, H2O2 content, root oxidizability and the activities of antioxidant enzymes in mung bean (Phaseolus aureus Roxb).
Abstract: Arsenic (As) toxicity and its biochemical effects have been mostly evaluated in ferns and a few higher plants. In this study, we investigated the effect of As (10.0 and 50.0 μM) on seedling growth, root anatomy, lipid peroxidation (malondialdehyde and conjugated dienes), electrolyte leakage, H2O2 content, root oxidizability and the activities of antioxidant enzymes in mung bean (Phaseolus aureus Roxb.). Arsenic significantly enhanced lipid peroxidation (by 52% at 50.0 μM As), electrolyte leakage and oxidizability in roots. However, there was no significant change in H2O2 content. Arsenic toxicity was associated with an increase in the activities of superoxide dismutase (SOD), guaiacol peroxidase (GPX) and glutathione reductase (GR). In response to 50.0 μM As, the activities of SOD and GR increased by over 60% and 90%, respectively. At 10.0 μM As, the activity of ascorbate peroxidase (APX) increased by 83%, whereas at 50.0 μM it declined significantly. The catalase (CAT) activity, on the other hand, decreased in response to As exposure, and it corresponded to the observed decrease in H2O2 content. We conclude that As causes a reduction in root elongation by inducing an oxidative stress that is related to enhanced lipid peroxidation, but not to H2O2 accumulation.
285 citations
"Superoxide-Dismutase Deficient Muta..." refers background in this paper
...or common bean is a widely grown food legume and is rich in antioxidant flavonoids and proteins [23]....
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...Like many other edible legumes, beans are highly sensitive to arsenate form of arsenic [23, 24] and showed severe perturbations in different morphophysiological, micromorphological, and biochemical parameters underAs exposure [25]....
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TL;DR: The results indicate that higher doses of arsenate produce oxidative damage in clover shoots, and increase in SOD activity and accumulation of PAs as well as chl loss could be prevented by application of Zn and Cd together with As.
277 citations
"Superoxide-Dismutase Deficient Muta..." refers background in this paper
...As can induce oxidative stress through generation of reactive oxygen species (ROS) [4, 5], and moderate accumulation of ROS significantly affects nuclear gene expression [9]....
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...Arsenic (As) is a ubiquitous toxic metalloid without known biological functions in higher plants [4, 5]....
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