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Beth A. Ahner - One of the best experts on this subject based on the ideXlab platform.

  • environmental cadmium levels increase phytochelatin and glutathione in lettuce grown in a chelator buffered nutrient solution
    Journal of Environmental Quality, 2003
    Co-Authors: Elizabeth A Maier, Rosalyn D Matthews, Jennifer A Mcdowell, Rebecca R Walden, Beth A. Ahner
    Abstract:

    : Phytochelatins are enzymatically synthesized peptides involved in metal detoxification and have been measured in plants grown at very high Cd concentrations, but few studies have examined the response of plants at lower environmentally relevant Cd concentrations. Using an ethylenediaminetetraacetic acid (EDTA)-buffered nutrient medium, we have varied Cd exposure and measured phytochelatin and glutathione concentrations in romaine lettuce (Lactuca sativa L. var. longifolia Lam. var. Parris Island) grown in a flow-through hydroponic (FTH) system. Very low free ionic Cd (10(-9.6) M) increased average phytochelatin concentrations above those of controls, and increasing Cd resulted in increased phytochelatin production, though increases were tissue dependent. Glutathione concentrations also increased with increasing Cd. In other standard hydroponic experiments, the media were manipulated to vary total Cd concentration while the ionic Cd was fixed. We found that the total amount of Cd (primarily EDTA bound) in the medium altered thiol production in roots, whereas thiols in leaves remained constant. The Cd uptake into roots and translocation to old leaves was also influenced by the total concentration in the medium. Cadmium in all tissues was lower and in some tissues thiol concentrations were higher than in FTH-grown plants grown in identical medium, suggesting that nutrient delivery technique is also an important variable. Though phytochelatin and glutathione production can be sensitive to changes in bioavailable Cd, thiol concentrations will not necessarily reflect the Cd content of the plant tissues.

  • Role for heavy metals in forest decline indicated by phytochelatin measurements
    Nature, 1996
    Co-Authors: James E. Gawel, Beth A. Ahner, Andrew J. Friedland, François M. M. Morel
    Abstract:

    FOREST decline in the United States and Europe has been documented for a number of tree species1,2 and atmospheric pollutants from industrial sources, such as acids or oxidants, are thought to be partly responsible1–4. Heavy metals have also been implicated because their deposition pattern is correlated with forest decline5–11, but so far there has been no direct evidence for a physiological link between tree damage and exposure to metals. Here we use the concentrations of Phytochelatins, which are intracellular metal-binding peptides that act as specific indicators of metal stress12,13, to show that metals are indeed likely to be a contributing factor in the decline of forests in the north-eastern United States. Phytochelatin concentrations in red spruce, a species in decline, are higher than in balsam fir, a species which is not. Concentrations increase with altitude, as does forest decline, and they also increase across the region in forest stands that show increasing levels of tree damage.

  • phytochelatin production in marine algae 1 an interspecies comparison
    Limnology and Oceanography, 1995
    Co-Authors: Beth A. Ahner, Shing Kong, Fracois M M Morel
    Abstract:

    Phytochelatins are metal-binding peptides produced enzymatically by higher plants, fungi, and algae in response to many metals, particularly Cd. We have studied phytochelatin production in several marine phytoplankton exposed to a range of free Cd ion concentrations. As a result of increased analytical resolution, we have found that all the species contain phytochelatin, even when there is no added Cd, and that elevated phytochelatin concentrations are induced by Cd, even at very low and environmentally relevant concentrations (as low as 10 -12 M free ion concn). In some but not all species, intracellular Cd and phytochelatin concentrations are maintained at a fixed stoichiometric ratio at high Cd concentrations. Phytochelatin production and accumulation appear to be regulated in a manner that varies among phytoplankton species.

  • phytochelatin production in marine algae 2 induction by various metals
    Limnology and Oceanography, 1995
    Co-Authors: Beth A. Ahner, Fracois M M Morel
    Abstract:

    Phytochelatin has been quantified in Thalassiosira weissflogii, a marine diatom after exposure to a series of trace metals (Cd, Pb, Ni, Cu, Zn, Co, Ag, and Hg) at concentrations similar to those in the marine environment. Within the range of concentrations relevant to natural waters, Cd, and to a lesser extent Cu and Zn, are the most effective inducers of Phytochelatins. The generality of this result was confirmed by short-term experiments with two other phytoplankton species. Quantification of intracellular Cd, Ni, and Zn shows that phytochelatin production does not follow a simple stoichiometric relationship to the metal quotas. The rapid formation of phytochelatin in T. weissflogii after Cd exposure and the fast elimination when metal exposure is alleviated reveal a dynamic pool of phytochelatin which is tightly regulated by the cell. Many trace metals have been shown to induce phytochelatin production in plants (Grill et al. 1987), although the concentration necessary to stimulate the response as well as the magnitude of the response depend on the particular metal. Although it is believed that production of this peptide is a general metal detoxification system, Cd has been found to be the most effective inducer of phytochelatin synthase (Grill et al. 1989). Our goal is to elucidate the factors that control phytochelatin production by phytoplankton in the laboratory in order to better understand what stimulates phytochelatin production in the field (Ahner et al. 1994). In a companion paper (Ahncr et al. 1995), we investigated phytochelatin production by several phytoplankton species in response to Cd. In this study we examine the response of Thalassiosira weissflogii to a variety of metals (Cd, Pb, Cu, Ni, Zn, Co, Ag, and Hg), all of which have been found to stimulate phytochelatin production in higher plants. As in our experiments with Cd, we tested free metal concentrations that would be encountered in natural seawater in order to evaluate which metals may stimulate this response in natural populations of algae. We performed short-term assays with two other phytoplankton species to compare the patterns of the phytochelatin response to various metals. Finally, to assess how changing environmental conditions might affect cellular concentrations of phytochelatin, we examined the kinetics of phytochelatin production and elimination upon changes in metal exposure.

  • phytochelatin production by marine phytoplankton at low free metal ion concentrations laboratory studies and field data from massachusetts bay
    Proceedings of the National Academy of Sciences of the United States of America, 1994
    Co-Authors: Beth A. Ahner, Neil M Price, François M. M. Morel
    Abstract:

    Abstract Phytochelatins are small metal-binding polypeptides synthesized by algae in response to high metal concentrations. Using a very sensitive HPLC method, we have quantified Phytochelatins from phytoplankton in laboratory cultures at environmentally relevant metal concentrations and in marine field samples. Intracellular concentrations of phytochelatin, in the diatom Thalassiosira weissflogii, exhibit a distinct dose-response relation with free Cd2+ concentration in the medium--not with total Cd(2+)--and are detectable even when the free Cd2+ concentration is less than 1 pM. In Massachusetts Bay, phytochelatin levels (normalized to chlorophyll a) in the particulate fraction are similar to those measured in laboratory cultures exposed to picomolar free Cd2+ concentrations and exhibit a decreasing seaward trend. Incubations of natural samples with added Cd2+ confirmed the induction of the peptides by this metal. Ambient phytochelatin concentrations thus appear to provide a measure of the metal stress resulting from the complex mixture of trace metals and chelators in natural waters.

Thomas Rausch - One of the best experts on this subject based on the ideXlab platform.

  • phytochelatin synthase pcs protein is induced in brassica juncea leaves after prolonged cd exposure
    Journal of Experimental Botany, 2003
    Co-Authors: Senta Heiss, Andreas Wachter, Jochen Bogs, Thomas Rausch
    Abstract:

    Abstract Higher plants respond to cadmium exposure with theproduction of Phytochelatins (PCn), small heavymetal binding peptides, which are synthesized fromglutathione by phytochelatin synthase (PCS). Theisolation of a PCS cDNA clone from Brassica junceaL. cv. Vitasso, a candidate species for phytoremedia-tion, is reported here. CLUSTAL analysis revealed aclose relationship of BjPCS1 with PCS proteins fromArabidopsis thaliana and Thlaspi caerulescens.BjPCS1 expressed as recombinant protein in E. colihad PCS activity in vitro that was activated by 50 mMCu and 200 mM Cd to a similar extent. Immunoblotanalysis with an antiserum directed against recombi-nant BjPCS1 showed constitutive PCS expressionduring plant development. As a percentage of thetotal protein, the expression was higher in the roots,internodes and petioles in comparison with the leaftissue. When B. juncea plants were treated with25 mM cadmium, PCn accumulated increasingly over a6 d period. Levels in shoots were about 3-fold higherthan in roots. Prolonged cadmium exposure caused asignificant increase of PCS protein in leaves,whereas in roots PCS protein levels were notaffected.Key words: Brassica juncea, cadmium, heavy metal,phytochelatin synthase.

  • phytochelatin synthase pcs protein is induced in brassica juncea leaves after prolonged cd exposure
    Journal of Experimental Botany, 2003
    Co-Authors: Senta Heiss, Andreas Wachter, Jochen Bogs, Thomas Rausch
    Abstract:

    Higher plants respond to cadmium exposure with the production of Phytochelatins (PCn), small heavy metal binding peptides, which are synthesized from glutathione by phytochelatin synthase (PCS). The isolation of a PCS cDNA clone from Brassica juncea L. cv. Vitasso, a candidate species for phytoremediation, is reported here. CLUSTAL analysis revealed a close relationship of BjPCS1 with PCS proteins from Arabidopsis thaliana and Thlaspi caerulescens. BjPCS1 expressed as recombinant protein in E. coli had PCS activity in vitro that was activated by 50 microM Cu and 200 microM Cd to a similar extent. Immunoblot analysis with an antiserum directed against recombinant BjPCS1 showed constitutive PCS expression during plant development. As a percentage of the total protein, the expression was higher in the roots, internodes and petioles in comparison with the leaf tissue. When B. juncea plants were treated with 25 microM cadmium, PCn accumulated increasingly over a 6 d period. Levels in shoots were about 3-fold higher than in roots. Prolonged cadmium exposure caused a significant increase of PCS protein in leaves, whereas in roots PCS protein levels were not affected.

Stephan Clemens - One of the best experts on this subject based on the ideXlab platform.

  • arabidopsis thaliana phytochelatin synthase 2 is constitutively active in vivo and can rescue the growth defect of the pcs1 deficient cad1 3 mutant on cd contaminated soil
    Journal of Experimental Botany, 2014
    Co-Authors: Tanja Kuhnlenz, Holger Schmidt, Shimpei Uraguchi, Stephan Clemens
    Abstract:

    Phytochelatins play a key role in the detoxification of metals in plants and many other eukaryotes. Their formation is catalysed by phytochelatin synthases (PCS) in the presence of metal excess. It appears to be common among higher plants to possess two PCS genes, even though in Arabidopsis thaliana only AtPCS1 has been demonstrated to confer metal tolerance. Employing a highly sensitive quantification method based on ultraperformance electrospray ionization quadrupole time-of-flight mass spectrometry, we detected AtPCS2-dependent phytochelatin formation. Overexpression of AtPCS2 resulted in constitutive phytochelatin accumulation, i.e. in the absence of metal excess, both in planta and in a heterologous system. This indicates distinct enzymatic differences between AtPCS1 and AtPCS2. Furthermore, AtPCS2 was able to partially rescue the Cd hypersensitivity of the AtPCS1-deficient cad1-3 mutant in a liquid seedling assay, and, more importantly, when plants were grown on soil spiked with Cd to a level that is close to what can be found in agricultural soils. No rescue was found in vertical-plate assays, the most commonly used method to assess metal tolerance. Constitutive AtPCS2-dependent phytochelatin synthesis suggests a physiological role of AtPCS2 other than metal detoxification. The differences observed between wild-type plants and cad13 on Cd soil demonstrated: (i) the essentiality of phytochelatin synthesis for tolerating levels of Cd contamination that can naturally be encountered by plants outside of metal-rich habitats, and (ii) a contribution to Cd accumulation under these conditions.

  • analysis of plant pb tolerance at realistic submicromolar concentrations demonstrates the role of phytochelatin synthesis for pb detoxification
    Environmental Science & Technology, 2014
    Co-Authors: Sina Fischer, Holger Schmidt, Tanja Kuhnlenz, Michael Thieme, Stephan Clemens
    Abstract:

    Lead (Pb) ranks first among metals with respect to tonnage produced and released into the environment. It is highly toxic and therefore an important pollutant of worldwide concern. Plant Pb uptake, accumulation, and detoxification mobilize Pb into food webs. Still, knowledge about the underlying mechanisms is very limited. This is largely due to serious experimental challenges with respect to Pb availability. In most studies, Pb(II) concentrations in the millimolar range have been used even though the toxicity threshold is in the nanomolar range. We therefore developed a low-phosphate, low-pH assay system that is more realistic with respect to soil solution conditions. In this system the growth of Arabidopsis thaliana seedlings was significantly affected by the addition of only 0.1 μM Pb(NO3)2. Involvement of Phytochelatins in the detoxification of Pb(II) could be demonstrated by investigating phytochelatin synthase mutants. They showed a stronger inhibition of root growth and a lack of Pb-activated phyto...

  • multi tasking phytochelatin synthases
    Plant Science, 2009
    Co-Authors: Stephan Clemens, Derek Persoh
    Abstract:

    Abstract Phytochelatins are essential for cadmium and arsenic detoxification in plants, some fungi, and animals. It is mysterious, that the responsible enzymes, phytochelatin synthases (PCS), are constitutively expressed and so widespread in nature. Phylogenetic analysis indicates multiple horizontal transfers of PCS genes, but a bacterial origin appears unlikely. Differences between bacterial and eukaryotic PCS proteins in structure and activity had indicated bi-functionality of phytochelatin synthases as peptidases and transpeptidases. Recent observations indicate that PCS indeed serve physiological functions that most likely are much more prevalent than cadmium or arsenic detoxification. First, PCS-deficient Arabidopsis thaliana mutants are hypersensitive to zinc suggesting a role of phytochelatin synthesis, i.e. the formation of metal-binding peptides from glutathione in a transpeptidase reaction, in Zn homeostasis. Second, these mutants are also impaired in defense responses conferring resistance to incompatible pathogens (= nonhost resistance). The latter is hypothesized to be attributable to an involvement of PCS as a peptidase in indole glucosinolate metabolism. Possibly, micronutrient homeostasis and nonhost resistance are closely connected as PCS are not the only proteins involved in both processes.

  • overexpression of phytochelatin synthase in tobacco distinctive effects of atpcs1 and cepcs genes on plant response to cadmium
    Journal of Experimental Botany, 2008
    Co-Authors: Sylwia Wojas, Henk Schat, Stephan Clemens, Jacek Hennig, Aleksandra Sklodowska, Edyta Kopera, Wojciech Bal, Danuta Maria Antosiewicz
    Abstract:

    Phytochelatins, heavy-metal-binding polypeptides, are synthesized by phytochelatin synthase (PCS) (EC 2.3.2.15). Previous studies on plants overexpressing PCS genes yielded contrasting phenotypes, ranging from enhanced cadmium tolerance and accumulation to cadmium hypersensitivity. This paper compares the effects of overexpression of AtPCS1 and CePCS in tobacco (Nicotiana tabacum var. Xanthi), and demonstrates how the introduction of single homologous genes affects to a different extent cellular metabolic pathways leading to the opposite of the desired effect. In contrast to WT and CePCS transformants, plants overexpressing AtPCS1 were Cd-hypersensitive although there was no substantial difference in cadmium accumulation between studied lines. Plants exposed to cadmium (5 and 25 μM CdCl 2 ) differed, however, in the concentration of non-protein thiols (NPT). In addition, PCS activity in AtPCS1 transformants was around 5-fold higher than in CePCS and WT plants. AtPCS1 expressing plants displayed a dramatic accumulation of γ-glutamylcysteine and concomitant strong depletion of glutathione. By contrast, in CePCS transformants, a smaller reduction of the level of glutathione was noticed, and a less pronounced change in γ-glutamylcysteine concentration. There was only a moderate and temporary increase in phytochelatin levels due to AtPCS1 and CePCS expression. Marked changes in NPT composition due to AtPCS1 expression led to moderately decreased Cd-detoxification capacity reflected by lower SH:Cd ratios, and to higher oxidative stress (assessed by DAB staining), which possibly explains the increase in Cd-sensitivity. The results indicate that contrasting responses to cadmium of plants overexpressing PCS genes might result from species-dependent differences in the activity of phytochelatin synthase produced by the transgenes.

  • evolution and function of phytochelatin synthases
    Journal of Plant Physiology, 2006
    Co-Authors: Stephan Clemens
    Abstract:

    Both essential and non-essential transition metal ions can easily be toxic to cells. The physiological range for essential metals between deficiency and toxicity is therefore extremely narrow and a tightly controlled metal homeostasis network to adjust to fluctuations in micronutrient availability is a necessity for all organisms. One protective strategy against metal excess is the expression of high-affinity binding sites to suppress uncontrolled binding of metal ions to physiologically important functional groups. The synthesis of Phytochelatins, glutathione-derived metal binding peptides, represents the major detoxification mechanism for cadmium and arsenic in plants and an unknown range of other organisms. A few years ago genes encoding phytochelatin synthases (PCS) were cloned from plants, fungi and nematodes. Since then it has become apparent that PCS genes are far more widespread than ever anticipated. Searches in sequence databases indicate PCS expression in representatives of all eukaryotic kingdoms and the presence of PCS-like proteins in several prokaryotes. The almost ubiquitous presence in the plant kingdom and beyond as well as the constitutive expression of PCS genes and PCS activity in all major plant tissues are still mysterious. It is unclear, how the extremely rare need to cope with an excess of cadmium or arsenic ions could explain the evolution and distribution of PCS genes. Possible answers to this question are discussed. Also, the molecular characterization of phytochelatin synthases and our current knowledge about the enzymology of phytochelatin synthesis are reviewed.

Barbara Pawlikskowronska - One of the best experts on this subject based on the ideXlab platform.

  • cellular mechanisms of cu tolerance in the epilithic lichen lecanora polytropa growing at a copper mine
    Lichenologist, 2006
    Co-Authors: Barbara Pawlikskowronska, William O Purvis, Jacek Pirszel, Tadeusz Skowroński
    Abstract:

    Cellular responses to copper stress were investigated for the first time in a saxicolous lichen species, Lecanora polytropa (Hoffm.) Rabenh. Bright blue-green apothecia accumulated up to 1·3% Cu on a dry weight basis (205 μ mol Cu g−1), c. 50% in an exchangeable form. A bright turquoise-blue layer extended beneath the hymenium into the medulla, above and between a dentate photobiont layer. Oxalic (1·88 μ mol g−1), citric (0·83 μ mol g−1) and lower concentrations of malic (0·45 μ mol g−1) acids were determined by GC/MS analysis. Short-term exposure to high Cu2+ concentrations (40 and 400 μ mol g−1) under non-complexing conditions caused a dose-dependent decrease in chlorophyll a content; chlorophyll b and total carotenoid contents remained constant. The phaeophytinization quotient remained unchanged during Cu2+ exposure. Analysis of thiol peptides confirmed glutathione was reduced (GSH) in native L. polytropa (0·538 μ mol g−1), and Phytochelatins (PC2 and PC3) oxidised. Short-term exposure to 40 μ mol g−1 Cu2+ oxidised c. 28% of the glutathione pool; oxidised phytochelatin concentrations remained unchanged. This is the first report of phytochelatin production and thiol peptide status in a crustose lichen. These represent two possible detoxification mechanisms in this Cu-tolerant species. Copper complexation by low molecular mass organic acids and non-protein thiols do not entirely account for its tolerance.

  • when adapted to high zinc concentrations the periphytic green alga stigeoclonium tenue produces high amounts of novel phytochelatin related peptides
    Aquatic Toxicology, 2003
    Co-Authors: Barbara Pawlikskowronska
    Abstract:

    Two ecotypes of the green alga Stigeoclonium tenue Kutz. coming from polluted or unpolluted freshwaters and showing various Zn-tolerance were compared for their production of non-proteinaceous thiols in response to Zn. In short-term (17 h) exposures to 15 microM Zn they did not reveal any significant difference in levels of glutathione, Phytochelatins and some unknown thiols. However, after prolonged metal exposure (48 h) the Zn-tolerant S. tenue (T) isolated from Zn-polluted mining water, produced at the expense of GSH besides Phytochelatins (PC(2)-PC(4)) much higher amounts of novel, phytochelatin-related peptides. After a 6-week exposure to 30 microM Zn, Phytochelatins (approximately 6 micromol SH per g D.W.) and the novel thiol peptides (approximately 31 micromol SH per g D.W.), only in the surviving Zn-tolerant alga, were produced. HPLC analysis suggested that the novel peptides (P1-P3) differ from each other by one gammaGlu-Cys unit. ESI/MS analysis of the purified, most abundant peptides P2 and P3, of m/z values 643 and 875, respectively, suggested that they contain one cysteine residue more than PC(2) and PC(3). A 22-fold higher concentration of these peptides in Zn-tolerant S. tenue (T) than in Zn-sensitive S. tenue (S) was also observed in response to Pb exposure. Biosynthesis of the large amounts of the novel thiol peptides, which contain more SH-groups than Phytochelatins, detected in the Zn-tolerant organism after long Zn exposure, and lack of such a response in the Zn-sensitive ecotype S. tenue (S), isolated from unpolluted water, suggest that they are essential in the adaptation of S. tenue (T) to increased heavy metal concentrations.

  • phytochelatin production in freshwater algae stigeoclonium in response to heavy metals contained in mining water effects of some environmental factors
    Aquatic Toxicology, 2001
    Co-Authors: Barbara Pawlikskowronska
    Abstract:

    Production of Phytochelatins (PC) in two freshwater, filamentous green algae of the genus Stigeoclonium, in response to heavy metals contained in mining water was studied. Stigeoclonium sp. grown abundantly in ditches with the mining water (southern Poland) accumulated high amounts of heavy metals. The other studied alga Stigeoclonium tenue Kutz. was isolated from unpolluted lake water in the Netherlands. Both algae exposed to the heavy metal mixture (17 microM; mainly zinc) contained in the hard, alkaline (pH 8.2) mining water produced similar amounts of Phytochelatins (PC2 and PC3): 500-600 nmol SH g(-1) dry weight. After water acidification to pH 6.8, a > 2-fold increase of the total phytochelatin level as well as the appearance of longer chain peptide PC4 in the cells of both algae was observed. The concentration of labile forms of zinc in the acidified mining water was four times as high as that in the alkaline water. The heavy metal mixture (17 microM) in non-complexing solution of pH 6.8 caused a comparable phytochelatin production in both Stigeoclonium strains as the same mixture present in the acidified mining water. However, in the non-complexing solution of pH 8.2, the metal mixture induced in algae more PCs than at pH 6.8. A positive effect of bicarbonate enrichment in the solution on the PC production in S. tenue was also observed. Stigeoclonium sp. exposed to high concentrations (10 microM) of individual metals (Zn, Pb and Cd available as free cations) synthesised much higher amounts of Phytochelatins (PC2-PC4) than in response to the metal mixture contained in the mining water. The order of PC induction by the studied metals in the Stigeoclonium sp. was Cd > Pb > Zn. Addition of suspended solid matter to the heavy metal solution resulted in essential quantitative changes in Phytochelatins in algal cells; a considerable decrease of PC2, PC3 and PC4 levels was observed. The PC production in algae of the genus Stigeoclonium exposed to the heavy metal mixture is discussed in the context of various metal bioavailability and the algal adaptation to complex aquatic environment.

  • phytochelatin production in freshwater algae stigeoclonium in response to heavy metals contained in mining water effects of some environmental factors
    International Symposium on Pollutant Responses in Marine Organisms (PRIMO 10), 2001
    Co-Authors: Barbara Pawlikskowronska
    Abstract:

    Production of Phytochelatins (PC) in two freshwater, filamentous green algae of the genus Stigeoclonium, in response to heavy metals contained in mining water was studied. Stigeoclonium sp. grown abundantly in ditches with the mining water (southern Poland) accumulated high amounts of heavy metals. The other studied alga Stigeoclonium tenue Kutz, was isolated from unpolluted lake water in the Netherlands. Both algae exposed to the heavy metal mixture (17 μM: mainly zine) contained in the hard, alkaline (pH 8.2) mining water produced similar amounts of Phytochelatins (PC 2 and PC 3 ): 500-600 nmol SH g -1 dry weight. After water acidification to pH 6.8, a >2-fold increase of the total phytochelation level as well as the appearance of longer chain peptide PC 4 in the cells of both algae was observed. The concentration of labile forms of zinc in the acidified mining water was four times as high as that in the alkaline water. The heavy metal mixture (17 μM) in non-complexing solution of pH 6.8 caused a comparable phytochelatin production in both Stigeoclonium strains as the same mixture present in the acidified mining water. However, in the non-complexing solution of pH 8.2, the metal mixture induced in algae more PCs than at pH 6.8. A positive effect of bicarbonate enrichment in the solution on the PC production in S. tenue was also observed. Stigeoclonium sp. exposed to high concentrations (10 μM) of individual metals (Zn, Pb and Cd available as free cations) synthesized much higher amounts of Phytochelatins (PC 2 -PC 4 ) than in response to the metal mixture contained in the mining water. The order of PC induction by the studied metals in the Stigeoclonium sp was Cd > Pb > Zn. Addition of suspended solid matter to the heavy metal solution resulted in essential quantitative changes in Phytochelatins in algal cells; a considerable decrease of PC 2 , PC 3 and PC 4 levels was observed. The PC production in algae of the genus Stigeoclonium exposed to the heavy metal mixture is discussed in the context of various metal bioavailability and the algal adaptation to complex aquatic environment.

Prabodh Kumar Trivedi - One of the best experts on this subject based on the ideXlab platform.

  • heterologous expression of ceratophyllum demersum phytochelatin synthase cdpcs1 in rice leads to lower arsenic accumulation in grain
    Scientific Reports, 2015
    Co-Authors: Manju Shri, Richa Dave, Sanjay Diwedi, Devesh Shukla, Ravi Kesari, Rudra Deo Tripathi, Prabodh Kumar Trivedi
    Abstract:

    Recent studies have identified rice (Oryza sativa) as a major dietary source of inorganic arsenic (As) and poses a significant human health risk. The predominant model for plant detoxification of heavy metals is complexation of heavy metals with Phytochelatins (PCs), synthesized non-translationally by PC synthase (PCS) and compartmentalized in vacuoles. In this study, in order to restrict As in the rice roots as a detoxification mechanism, a transgenic approach has been followed through expression of phytochelatin synthase, CdPCS1, from Ceratophyllum demersum, an aquatic As-accumulator plant. CdPCS1 expressing rice transgenic lines showed marked increase in PCS activity and enhanced synthesis of PCs in comparison to non-transgenic plant. Transgenic lines showed enhanced accumulation of As in root and shoot. This enhanced metal accumulation potential of transgenic lines was positively correlated to the content of PCs, which also increased several-fold higher in transgenic lines. However, all the transgenic lines accumulated significantly lower As in grain and husk in comparison to non-transgenic plant. The higher level of PCs in transgenic plants relative to non-transgenic presumably allowed sequestering and detoxification of higher amounts of As in roots and shoots, thereby restricting its accumulation in grain.

  • arsenic accumulation and tolerance in rootless macrophyte najas indica are mediated through antioxidants amino acids and Phytochelatins
    Aquatic Toxicology, 2014
    Co-Authors: Rudra Deo Tripathi, Sanjay Dwivedi, Ragini Singh, Preeti Tripathi, Reshu Chauhan, Bijan Adhikari, Prabodh Kumar Trivedi
    Abstract:

    Abstract Arsenic (As) accumulation and tolerance response of a submerged rootless macrophyte Najas indica were evaluated during arsenate (AsV; 10–250 μM) and arsenite (AsIII; 1–50 μM) exposure. Higher As accumulation at AsIII exposure and more tolerance upon AsV exposure resulted in more toxicity during AsIII stress than AsV, which was evident through measurement of growth parameters and oxidative stress related parameters viz., lipid peroxidation (MDA content), electrical conductivity (EC) and hydrogen peroxide (H2O2) levels. Antioxidant enzymes and various amino acids were more prominent during moderate exposure of AsV, suggesting their possible role in As tolerance and detoxification. Various non-enzymatic antioxidant metabolites viz., ascorbic acid (ASC), glutathione (GSH), non-protein thiols (NPTs) and Phytochelatins (PCs) biosynthesis involving phytochelatin synthase (PCS) activity increased more significantly during AsIII stress. However, PCs content seems inadequate in response to As accumulation leading to lower PC-SH:As molar ratio and higher As phytotoxicity during AsIII stress. N. indica may prove useful plant species for phytoremediation purpose in moderately As contaminated water bodies due to high As accumulation and tolerance potential.

  • thiol metabolism play significant role during cadmium detoxification by ceratophyllum demersum l
    Bioresource Technology, 2009
    Co-Authors: Seema Mishra, Rudra Deo Tripathi, Prabodh Kumar Trivedi, Sudhakar Srivastava, Sanjay Dwivedi, Om Parkash Dhankher, A Khare
    Abstract:

    Abstract In the present study, the level of thiols and activity of related enzymes were investigated in coontail ( Ceratophyllum demersum L.) plants to analyze their role in combating the stress caused upon exposure to cadmium (Cd; 0–10 μM) for a duration up to 7 d. Plants showed the maximum accumulation of 1293 μg Cd g −1  dw after 7 d at 10 μM. Significant increases in the level of total non-protein thiols (NP-SH) including Phytochelatins (PCs) as well as upstream metabolites of the PC biosynthetic pathway, cysteine and glutathione (GSH) were observed. In addition, significant increases in the activities of cysteine synthase (CS), glutathione- S -transferase (GST), glutathione reductase (GR), as well as in vitro activation of phytochelatin synthase (PCS), were noticed in response to Cd. In conclusion, under Cd stress, plants adapted to a new metabolic equilibrium of thiols through coordinated synthesis and consumption to combat Cd toxicity and to accumulate it.