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Leon V Kochian - One of the best experts on this subject based on the ideXlab platform.
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Differences in Whole-Cell and Single-Channel Ion Currents across the Plasma Membrane of Mesophyll Cells from Two Closely Related Thlaspi Species
2015Co-Authors: Miguel A. Piñeros, Leon V KochianAbstract:The patch clamp technique was used to study the physiology of ion transport in mesophyll cells from two Thlaspi spp. that differ significantly in their physiology. In comparison with Thlaspi arvense, Thlaspi caerulescens (a heavy metal accumulator) can grow in, tolerate, and accumulate very high levels of certain heavy metals (primarily zinc [Zn] and cadmium) in their leaf cells. The membrane conductance of every T. arvense leaf cell was dominated by a slowly activating, time-dependent outward rectifying current (SKOR). In contrast, only 23 % of T. caerulescens cells showed SKOR activity, whereas the remaining 77 % exhibit a rapidly developing instantaneous K outward rectifier (RKOR) current. In contrast to RKOR, the channels underlying the SKOR current were sensitive to changes in the extracellular ion activity. Single-channel recordings indicated the existence of K channel populations with similar unitary conductances, but distinct channel kinetics and regulation. The correlation between these recordings and the whole-cell data indicated that although one type of channel kinetics is preferentially activated in each Thlaspi spp., both species have the capability to switch between either type of current. Ion substitution in whole-cell and single-channel experiments indicated that although the SKOR and RKOR channels mediate a net outward K current, they can also allow a significant Zn2 permeation (i.e. influx). In addition, single-channel recordings allowed us to identify an infrequent type of plasma membrane divalent cation channel that also can mediate Zn2 influx. We propose that the different K channel types or channel states may result from and are likely to reflect differences in the cytoplasmic and apoplastic ionic environment in each species. Thus, the ability to interchangeabl
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investigating heavy metal hyperaccumulation using Thlaspi caerulescens as a model system
Annals of Botany, 2008Co-Authors: Matthew J Milner, Leon V KochianAbstract:†Background Metal-hyperaccumulating plant species are plants that are endemic to metalliferous soils and are able to tolerate and accumulate metals in their above-ground tissues to very high concentrations. One such hyperaccumulator, Thlaspi caerulescens, has been widely studied for its remarkable properties to tolerate toxic levels of zinc (Zn), cadmium (Cd) and sometimes nickel (Ni) in the soil, and accumulate these metals to very high levels in the shoot. The increased awareness regarding metal-hyperaccumulating plants by the plant biology community has helped spur interest in the possible use of plants to remove heavy metals from contaminated soils, a process known as phytoremediation. Hence, there has been a focus on understanding the mechanisms that metal-hyperaccumulator plant species such as Thlaspi caerulescens employ to absorb, detoxify and store metals in order to use this information to develop plants better suited for the phytoremediation of metal-contaminated soils. †Scope In this review, an overview of the findings from recent research aimed at better understanding the physiological mechanisms of Thlaspi caerulescens heavy-metal hyperaccumulation as well as the underlying molecular and genetic determinants for this trait will be discussed. Progress has been made in understanding some of the fundamental Zn and Cd transport physiology in T. caerulescens. Furthermore, some interesting metal-related genes have been identified and characterized in this plant species, and regulation of the expression of some of these genes may be important for hyperaccumulation. †Conclusions Thlaspi caerulescens is a fascinating and useful model system not only for studying metal hyperaccumulation, but also for better understanding micronutrient homeostasis and nutrition. Considerable future research is still needed to elucidate the molecular, genetic and physiological bases for the extreme metal tolerance and hyperaccumulation exhibited by plant species such as T. caerulescens.
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plant cd2 and zn2 status effects on root and shoot heavy metal accumulation in Thlaspi caerulescens
New Phytologist, 2007Co-Authors: Ashot Papoyan, Miguel A Pineros, Leon V KochianAbstract:Summary • In this study we address the impact of changes in plant heavy metal, (i.e. zinc (Zn) and cadmium (Cd)) status on metal accumulation in the Zn/Cd hyperaccumulator, Thlaspi caerulescens. • Thlaspi caerulescens plants were grown hydroponically on both high and low Zn and Cd regimes and whole-shoot and -root metal accumulation, and root 109Cd2+ influx were determined. • High-Zn-grown (500 µm Zn) plants were found to be more Cd-tolerant than plants grown in standard Zn conditions (1 µm Zn). Furthermore, shoot Cd accumulation was significantly greater in the high-Zn-grown plants. A positive correlation was also found between shoot Zn accumulation and increased plant Cd status. Radiotracer 109Cd root flux experiments demonstrated that high-Zn-grown plants maintained significantly higher root Cd2+ influx than plants grown on 1 µm Zn. It was also found that both nickel (Ni) and copper (Cu) shoot accumulation were stimulated by high plant Zn status, while manganese (Mn) accumulation was not affected. • A speculative model is presented to explain these findings, suggesting that xylem loading may be one of the key sites responsible for the hyperaccumulation of Zn and Cd accumulation in Thlaspi caerulescens.
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differences in whole cell and single channel ion currents across the plasma membrane of mesophyll cells from two closely related Thlaspi species
Plant Physiology, 2003Co-Authors: Miguel A Pineros, Leon V KochianAbstract:The patch clamp technique was used to study the physiology of ion transport in mesophyll cells from two Thlaspi spp. that differ significantly in their physiology. In comparison with Thlaspi arvense , Thlaspi caerulescens (a heavy metal accumulator) can grow in, tolerate, and accumulate very high levels of certain heavy metals (primarily zinc [Zn] and cadmium) in their leaf cells. The membrane conductance of every T. arvense leaf cell was dominated by a slowly activating, time-dependent outward rectifying current (SKOR). In contrast, only 23% of T. caerulescens cells showed SKOR activity, whereas the remaining 77% exhibit a rapidly developing instantaneous K + outward rectifier (RKOR) current. In contrast to RKOR, the channels underlying the SKOR current were sensitive to changes in the extracellular ion activity. Single-channel recordings indicated the existence of K + channel populations with similar unitary conductances, but distinct channel kinetics and regulation. The correlation between these recordings and the whole-cell data indicated that although one type of channel kinetics is preferentially activated in each Thlaspi spp., both species have the capability to switch between either type of current. Ion substitution in whole-cell and single-channel experiments indicated that although the SKOR and RKOR channels mediate a net outward K + current, they can also allow a significant Zn 2+ permeation (i.e. influx). In addition, single-channel recordings allowed us to identify an infrequent type of plasma membrane divalent cation channel that also can mediate Zn 2+ influx. We propose that the different K + channel types or channel states may result from and are likely to reflect differences in the cytoplasmic and apoplastic ionic environment in each species. Thus, the ability to interchangeably switch between different channel states allows each species to constantly adjust to changes in their apoplastic ionic environment.
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the molecular physiology of heavy metal transport in the zn cd hyperaccumulator Thlaspi caerulescens
Proceedings of the National Academy of Sciences of the United States of America, 2000Co-Authors: Nicole S Pence, Deborah L D Letham, Mitch M Lasat, David J Eide, David F. Garvin, Paul B. Larsen, Stephen D. Ebbs, Leon V KochianAbstract:An integrated molecular and physiological investigation of the fundamental mechanisms of heavy metal accumulation was conducted in Thlaspi caerulescens, a Zn/Cd-hyperaccumulating plant species. A heavy metal transporter cDNA, ZNT1, was cloned from T. caerulescens through functional complementation in yeast and was shown to mediate high-affinity Zn2+ uptake as well as low-affinity Cd2+ uptake. It was found that this transporter is expressed at very high levels in roots and shoots of the hyperaccumulator. A study of ZNT1 expression and high-affinity Zn2+ uptake in roots of T. caerulescens and in a related nonaccumulator, Thlaspi arvense, showed that alteration in the regulation of ZNT1 gene expression by plant Zn status results in the overexpression of this transporter and in increased Zn influx in roots of the hyperaccumulating Thlaspi species. These findings yield insights into the molecular regulation and control of plant heavy metal and micronutrient accumulation and homeostasis, as well as provide information that will contribute to the advancement of phytoremediation by the future engineering of plants with improved heavy metal uptake and tolerance.
A J M Baker - One of the best experts on this subject based on the ideXlab platform.
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a comparison of the Thlaspi caerulescens and Thlaspi arvense shoot transcriptomes
New Phytologist, 2006Co-Authors: Victoria Mills, Steven N Whiting, John P Hammond, Kevin A Pyke, A J M Baker, Philip J. White, Helen C. Bowen, Martin R. BroadleyAbstract:Summary • Whole-genome transcriptome profiling is revealing how biological systems are regulated at the transcriptional level. This study reports the development of a robust method to profile and compare the transcriptomes of two nonmodel plant species, Thlaspi caerulescens, a zinc (Zn) hyperaccumulator, and Thlaspi arvense, a nonhyperaccumulator, using Affymetrix Arabidopsis thaliana ATH1-121501 GeneChip® arrays (Affymetrix, Santa Clara, CA, USA). • Transcript abundance was quantified in the shoots of agar- and compost-grown plants of both species. Analyses were optimized using a genomic DNA (gDNA)-based probe-selection strategy based on the hybridization efficiency of Thlaspi gDNA with corresponding A. thaliana probes. In silico alignments of GeneChip® probes with Thlaspi gene sequences, and quantitative real-time PCR, confirmed the validity of this approach. • Approximately 5000 genes were differentially expressed in the shoots of T. caerulescens compared with T. arvense, including genes involved in Zn transport and compartmentalization. • Future functional analyses of genes identified as differentially expressed in the shoots of these closely related species will improve our understanding of the molecular mechanisms of Zn hyperaccumulation.
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nickel and zinc hyperaccumulation by alyssum murale and Thlaspi caerulescens brassicaceae do not enhance survival and whole plant growth under drought stress
Plant Cell and Environment, 2003Co-Authors: Steven N Whiting, Peter M. Neumann, A J M BakerAbstract:Nickel and Zn hyperaccumulation by Alyssum murale and Thlaspi caerulescens bear substantial energetic costs and should confer benefits to the plant. This research determined whether metal hyperaccumulation can increase osmotic adjustment and resistance to water stress (drought). Alyssum murale and Thlaspi caerulescens treated with low or high concentrations of Ni or Zn were exposed to moderate (−0·4 MPa) and severe (−1·0 MPa) water stresses using aqueous polyethylene glycol. In the absence of metals both water deficits inhibited shoot growth. Nickel and Zn hyperaccumulation did not ameliorate growth inhibition by either level of water stress. The water stress did not induce major changes in shoot metal concentrations of these constitutive hyperaccumulators. Moreover, metal hyperaccumulation had minimal effects on the osmolality of leaf-sap extracts, relative water content of the shoots, or rate of evapotranspiration. It is concluded that Ni or Zn hyperaccumulation does not augment whole-plant capacity for drought resistance in A. murale and T. caerulescens.
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assessment of zn mobilization in the rhizosphere of Thlaspi caerulescens by bioassay with non accumulator plants and soil extraction
Plant and Soil, 2001Co-Authors: Steven N Whiting, Stephen P Mcgrath, Jonathan R. Leake, A J M BakerAbstract:This study used co-cultivated plants as a bioassay to test the hypothesis that the roots of the zinc-hyperaccumulating plant Thlaspi caerulescensmobilize Zn from less-available pools in the soil. Thlaspi caerulescens was grown in uncompartmentalised pots, or pots that were divided by solid or mesh barriers to limit the extent of root intermingling (rhizosphere interaction) with co-cultivated Thlaspi arvense or Festuca rubra. Thlaspi caerulescens did not increase the concentration of Zn in either indicator species, suggesting that T. caerulescens does not strongly mobilize Zn in its rhizosphere. The increase in the shoot mass of T. arvense when its roots were permitted to intermingle with those of T. caerulescens was explained by greater intensity of competition of T. arvense compared to T. caerulescens.
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hyperaccumulation of zn by Thlaspi caerulescens can ameliorate zn toxicity in the rhizosphere of cocropped Thlaspi arvense
Environmental Science & Technology, 2001Co-Authors: Steven N Whiting, S P Mcgrath, Jonathan R. Leake, A J M BakerAbstract:The metal hyperaccumulating plant Thlaspi caerulescens is effective in depleting plant-available metals from the soil. We hypothesized that this reduction of toxic metals in the rhizosphere of T. caerulescens would increase the growth of less metal-tolerant plants with their roots permitted to intermingle and develop coincident rhizospheres. The extent of rhizosphere interaction between T. caerulescens and a coplanted nonaccumulator species, Thlaspi arvense, was controlled using barriers. Two media with elevated concentrations of water-extractable Zn were prepared by enriching one soil with zinc oxide (ZnO) or zinc sulfide (ZnS). The shoot mass of T. arvense was increased by 30% when its roots were permitted to intermingle with those of T. caerulescens in the ZnO treatment. The concomitant 2−3-fold reduction in shoot Zn concentration in T. arvense confirmed that its improved growth was associated with reduced uptake and phytotoxicity of Zn. Thlaspi arvense also showed increased growth and reduced metal up...
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altered zn compartmentation in the root symplasm and stimulated zn absorption into the leaf as mechanisms involved in zn hyperaccumulation in Thlaspi caerulescens
Plant Physiology, 1998Co-Authors: Mitch M Lasat, A J M Baker, Leon V KochianAbstract:We investigated Zn compartmentation in the root, Zn transport into the xylem, and Zn absorption into leaf cells in Thlaspi caerulescens , a Zn-hyperaccumulator species, and compared them with those of a related nonaccumulator species, Thlaspi arvense . 65 Zn-compartmental analysis conducted with roots of the two species indicated that a significant fraction of symplasmic Zn was stored in the root vacuole of T. arvense , and presumably became unavailable for loading into the xylem and subsequent translocation to the shoot. In T. caerulescens , however, a smaller fraction of the absorbed Zn was stored in the root vacuole and was readily transported back into the cytoplasm. We conclude that in T. caerulescens , Zn absorbed by roots is readily available for loading into the xylem. This is supported by analysis of xylem exudate collected from detopped Thlaspi species seedlings. When seedlings of the two species were grown on either low (1 μm) or high (50 μm) Zn, xylem sap of T. caerulescens contained approximately 5-fold more Zn than that of T. arvense . This increase was not correlated with a stimulated production of any particular organic or amino acid. The capacity of Thlaspi species cells to absorb 65 Zn was studied in leaf sections and leaf protoplasts. At low external Zn levels (10 and 100 μm), there was no difference in leaf Zn uptake between the two Thlaspi species. However, at 1 mmZn 2+ , 2.2-fold more Zn accumulated in leaf sections of T. caerulescens . These findings indicate that altered tonoplast Zn transport in root cells and stimulated Zn uptake in leaf cells play a role in the dramatic Zn hyperaccumulation expressed in T. caerulescens .
David E. Salt - One of the best experts on this subject based on the ideXlab platform.
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reciprocal grafting separates the roles of the root and shoot in zinc hyperaccumulation in Thlaspi caerulescens
New Phytologist, 2009Co-Authors: Marcelo De Almeida Guimaraes, Jean Louis Gustin, David E. SaltAbstract:Summary • The extreme phenotype of zinc (Zn) hyperaccumulation, which is found in several Brassicaceae species, is determined by mechanisms that promote elevated Zn tolerance and high Zn accumulation in shoots. • We used reciprocal grafting between a Zn hyperaccumulator, Thlaspi caerulescens, and a Zn nonaccumulator, Thlaspi perfoliatum, to determine the relative importance of roots and shoots in Zn hyperaccumulation and hypertolerance. • Leaves from plants with a T. perfoliatum rootstock and a T. caerulescens shoot scion did not hyperaccumulate Zn, whereas plants with a T. caerulescens rootstock and a T. perfoliatum shoot scion did hyperaccumulate Zn. However, although leaves from plants with a T. caerulescens rootstock and a T. perfoliatum shoot scion hyperaccumulated Zn, at high Zn loads these leaves showed significant symptoms of Zn toxicity, unlike leaves of self grafted T. caerulescens. • Hyperaccumulation of Zn in leaves of the hyperaccumulator T. caerulescens is pri-marily dictated by root processes. Further, the mechanisms controlling Zn hypertolerance in the hyperaccumulator T. caerulescens are driven primarily by shoot processes.
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The metal tolerance profile of Thlaspi goesingense is mimicked in Arabidopsis thaliana heterologously expressing serine acetyl-transferase
BMC plant biology, 2007Co-Authors: John L Freeman, David E. SaltAbstract:Background The Ni hyperaccumulator Thlaspi goesingense is tolerant to Ni ≅ Zn, ≅ Co and slightly resistant to > Cd. We previously observed that elevated glutathione, driven by constitutive activation of serine acetyltransferase (SAT), plays a role in the Ni tolerance of T. goesingense.
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constitutively elevated salicylic acid signals glutathione mediated nickel tolerance in Thlaspi nickel hyperaccumulators
Plant Physiology, 2005Co-Authors: John L Freeman, Amber Hopf, Daniel Garcia, David E. SaltAbstract:Progress is being made in understanding the biochemical and molecular basis of nickel (Ni)/zinc (Zn) hyperaccumulation in Thlaspi; however, the molecular signaling pathways that control these mechanisms are not understood. We observed that elevated concentrations of salicylic acid (SA), a molecule known to be involved in signaling induced pathogen defense responses in plants, is a strong predictor of Ni hyperaccumulation in the six diverse Thlaspi species investigated, including the hyperaccumulators Thlaspi goesingense, Thlaspi rosulare, Thlaspi oxyceras, and Thlaspi caerulescens and the nonaccumulators Thlaspi arvense and Thlaspi perfoliatum. Furthermore, the SA metabolites phenylalanine, cinnamic acid, salicyloyl-glucose, and catechol are also elevated in the hyperaccumulator T. goesingense when compared to the nonaccumulators Arabidopsis (Arabidopsis thaliana) and T. arvense. Elevation of free SA levels in Arabidopsis, both genetically and by exogenous feeding, enhances the specific activity of serine acetyltransferase, leading to elevated glutathione and increased Ni resistance. Such SA-mediated Ni resistance in Arabidopsis phenocopies the glutathione-based Ni tolerance previously observed in Thlaspi, suggesting a biochemical linkage between SA and Ni tolerance in this genus. Intriguingly, the hyperaccumulator T. goesingense also shows enhanced sensitivity to the pathogen powdery mildew (Erysiphe cruciferarum) and fails to induce SA biosynthesis after infection. Nickel hyperaccumulation reverses this pathogen hypersensitivity, suggesting that the interaction between pathogen resistance and Ni tolerance and hyperaccumulation may have played a critical role in the evolution of metal hyperaccumulation in the Thlaspi genus.
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increased glutathione biosynthesis plays a role in nickel tolerance in Thlaspi nickel hyperaccumulators
The Plant Cell, 2004Co-Authors: John L Freeman, Michael W Persans, Carrie Albrecht, Wendy Ann Peer, Ken Nieman, Ingrid J Pickering, David E. SaltAbstract:Worldwide more than 400 plant species are now known that hyperaccumulate various trace metals (Cd, Co, Cu, Mn, Ni, and Zn), metalloids (As) and nonmetals (Se) in their shoots. Of these, almost one-quarter are Brassicaceae family members, including numerous Thlaspi species that hyperaccumulate Ni up to 3% of there shoot dry weight. We observed that concentrations of glutathione, Cys, and O-acetyl-l-serine (OAS), in shoot tissue, are strongly correlated with the ability to hyperaccumulate Ni in various Thlaspi hyperaccumulators collected from serpentine soils, including Thlaspi goesingense, T. oxyceras, and T. rosulare, and nonaccumulator relatives, including T. perfoliatum, T. arvense, and Arabidopsis thaliana. Further analysis of the Austrian Ni hyperaccumulator T. goesingense revealed that the high concentrations of OAS, Cys, and GSH observed in this hyperaccumulator coincide with constitutively high activity of both serine acetyltransferase (SAT) and glutathione reductase. SAT catalyzes the acetylation of l-Ser to produce OAS, which acts as both a key positive regulator of sulfur assimilation and forms the carbon skeleton for Cys biosynthesis. These changes in Cys and GSH metabolism also coincide with the ability of T. goesingense to both hyperaccumulate Ni and resist its damaging oxidative effects. Overproduction of T. goesingense SAT in the nonaccumulator Brassicaceae family member Arabidopsis was found to cause accumulation of OAS, Cys, and glutathione, mimicking the biochemical changes observed in the Ni hyperaccumulators. In these transgenic Arabidopsis, glutathione concentrations strongly correlate with increased resistance to both the growth inhibitory and oxidative stress induced effects of Ni. Taken together, such evidence supports our conclusion that elevated GSH concentrations, driven by constitutively elevated SAT activity, are involved in conferring tolerance to Ni-induced oxidative stress in Thlaspi Ni hyperaccumulators.
Marjana Regvar - One of the best experts on this subject based on the ideXlab platform.
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Physiological responses to Cd and Zn in two Cd/Zn hyperaccumulating Thlaspi species
Environmental and Experimental Botany, 2009Co-Authors: Paula Pongrac, Fang-jie Zhao, Jaka Razinger, Alexis Zrimec, Marjana RegvarAbstract:In a model hyperaccumulation study a Cd/Zn hyperaccumulator Thlaspi caerulescens accession Ganges and a recently reported Cd/Zn hyperaccumulator Thlaspi praecox grown in increasing Cd and Zn concentrations in the substrate and in field collected polluted soil were compared. Plant biomass, concentrations of Cd and Zn, total chlorophylls and anthocyanins, antioxidative stress parameters and activities of selected antioxidative enzymes were compared. Increasing Cd, but not Zn in the substrate resulted in the increase of biomass of roots and shoots of T. praecox and T. caerulescens. The two species hyperaccumulated Cd in the shoots to a similar extent, whereas T. caerulescens accumulated more Zn in the shoots than T. praecox. Cadmium amendment decreased total chlorophyll concentration and glutathione reductase activity, and increased non-protein thiols concentration only in T. praecox, suggesting that it is less tolerant to Cd than T. caerulescens. In the field-contaminated soil, T. caerulescens accumulated higher Cd concentrations; but as T. praecox produced higher biomass, both species have similar ability to extract Cd.
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Spatial distribution of cadmium in leaves of metal hyperaccumulating Thlaspi praecox using micro-PIXE.
The New phytologist, 2008Co-Authors: Katarina Vogel-mikuš, Marjana Regvar, Jolanta Mesjasz-przybyłowicz, Wojciech J. Przybyłowicz, Jure Simčič, Primož Pelicon, Miloš BudnarAbstract:Summary • Localization of cadmium (Cd) and other el ements was studied in the leaves of thefield-collected cadmium/zinc (Cd/Zn) hyperaccumulator Thlaspi praecox from anarea polluted with heavy metals near a lead mine and smelter in Slovenia, usingmicro-PIXE (proton-induced X-ray emission).† The samples were prepared using cryofixation. Quantitative elemental maps andaverage concentrations in whole-leaf cross-sections and selected tissues wereobtained.† Cd was preferentially localized in the lower epidermis (820 µg g –1 DW), vascularbundles and upper epidermis, whereas about twice the lower concentrations werefound in the mesophyll.† Taking into account the large volume of the mesophyll compared with the epider-mis, the mesophyll is indicated as a relatively large pool of Cd, possibly involved inCd detoxification/dilution at the tissue and cellular level. Key words: cadmium (Cd), dynamic analysis, metal hyperaccumulation, mineralnutrients, nuclear microprobe, Thlaspi praecox , true elemental mapping, X-raymicronalysis.
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Distinctive effects of cadmium on glucosinolate profiles in Cd hyperaccumulator Thlaspi praecox and non-hyperaccumulator Thlaspi arvense
Plant and Soil, 2006Co-Authors: Roser Tolrà, Charlotte Poschenrieder, Marjana Regvar, Paula Pongrac, Katarina Vogel-mikuš, Juan BarcelóAbstract:The influence of Cd on growth, Cd accumulation and glucosinolate (GS) contents was investigated in Thlaspi praecox in comparison to Thlaspi arvense. Accumulation of up to 2,700 μg Cd g-1 dry weight in shoots of T. praecox, growing in nutrient solution with 50 μM Cd without growth inhibition, confirmed this species as a Cd-hyperaccumulator. Cadmium increased the level of total GS in T. praecox without a statistically significant influence on total sulphur. This increase in GS was due to the enhancement of benzyl-GS, mainly sinalbin. In the Cd sensitive T. arvense Cd caused a shift from alkenyl-GS, mainly sinigrin, to indolyl-GS. The Cd-induced increase of total GS in T. praecox indicates that in this species Cd hyperaccumulation is not linked to trade-off of organic defences. The distinctive influence of Cd on GS profiles in Cd-sensitive T. arvense and Cd-tolerant T. praecox favouring indolyl-GS and benzyl-GS, respectively, is discussed in relation to jasmonate and salicylate as possible key molecules in Cd-stress transduction in these contrasting Thlaspi species.
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zn cd and pb accumulation and arbuscular mycorrhizal colonisation of pennycress Thlaspi praecox wulf brassicaceae from the vicinity of a lead mine and smelter in slovenia
Environmental Pollution, 2005Co-Authors: Katarina Vogelmikus, Damjana Drobne, Marjana RegvarAbstract:AbstractSignificant hyperaccumulation of Zn, Cd and Pb in field samples of Thlaspi praecox Wulf. collected from a heavy metal pollutedarea in Slovenia was found, with maximal shoot concentrations of 14590 mgkg 1 Zn, 5960 mgkg Cd and 3500 mgkg Pb.Shoot/root ratios of 9.6 for Zn and 5.6 for Cd show that the metals were preferentially transported to the shoots. Shoot bio-accumulation factors exceeded total soil Cd levels 75-fold and total soil Zn levels 20-fold, further supporting the hyperaccumulationof Cd and Zn. Eighty percent of Pb was retained in roots, thus indicating exclusion as a tolerance strategy for Pb. Low levelcolonisation with arbuscular mycorrhizal fungi (AMF) of a Paris type was observed at the polluted site, whereas at the non-pollutedsite Arum type colonisation was more common. To our knowledge this is the first report of Cd hyperaccumulation and AMFcolonisation in metal hyperaccumulating T. praecox. 2004 Elsevier Ltd. All rights reserved. Keywords: Thlaspi praecox; Arbuscular mycorrhiza; Hyperaccumulation; Phytoremediation; Heavy metals
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Colonization of pennycresses (Thlaspi spp.) of the Brassicaceae by arbuscular mycorrhizal fungi.
Journal of plant physiology, 2003Co-Authors: Marjana Regvar, Katarina Vogel, Nina Irgel, Tone Wraber, Ulrich Hildebrandt, Petra Wilde, Hermann BotheAbstract:Summary Members of the Brassicaceae are generally believed to be non-mycorrhizal. Pennycress (Thlaspi) species of this family from diverse locations in Slovenia, Austria, Italy and Germany were examined for their colonisation by arbuscular mycorrhizal fungi (AMF). Meadow species (T. praecox, T. caerulescens and T. montanum) were sparsely but distinctly colonised, as indicated by the occurrence of intraradical hyphae, vesicles, coils, and occasionally arbuscules. Species from other locations were poorly colonised, but arbuscules were not discernible. The genus Thlaspi comprises several heavy metal hyperaccumulating species (T. caerulescens, T. goesingense, T. calaminare, T. cepaeifolium). All samples collected from heavy metal soils were at best poorly colonized. Thus the chance is small to find a «hypersystem» in phytoremediation consisting of an AM fungus which prevents the uptake of the major part of the heavy metals and of a Thlaspi species which effectively deposits the residual heavy metals inevitably taken up into its vacuoles. In two different PCR approaches, fungal DNA was amplified from most of the Thlaspi roots examined, even from those with a very low incidence of AMF colonization. Sequencing of the 28S- and 18S-rDNA PCR-products revealed that different Thlaspi field samples were colonized by Glomus intraradices and thus by a common AM fungus. However, none of the sequences obtained was identical to any other found in the present study or deposited in the databanks, which might indicate that a species continuum exists in the G. intraradices clade. An effective colonization of Thlaspi by AMF could not be established in greenhouse experiments. Although the data show that Thlaspi can be colonized by AMF, it is doubtful whether an effective symbiosis with the mutual exchange of metabolites is formed by both partners.
Steven N Whiting - One of the best experts on this subject based on the ideXlab platform.
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a comparison of the Thlaspi caerulescens and Thlaspi arvense shoot transcriptomes
New Phytologist, 2006Co-Authors: Victoria Mills, Steven N Whiting, John P Hammond, Kevin A Pyke, A J M Baker, Philip J. White, Helen C. Bowen, Martin R. BroadleyAbstract:Summary • Whole-genome transcriptome profiling is revealing how biological systems are regulated at the transcriptional level. This study reports the development of a robust method to profile and compare the transcriptomes of two nonmodel plant species, Thlaspi caerulescens, a zinc (Zn) hyperaccumulator, and Thlaspi arvense, a nonhyperaccumulator, using Affymetrix Arabidopsis thaliana ATH1-121501 GeneChip® arrays (Affymetrix, Santa Clara, CA, USA). • Transcript abundance was quantified in the shoots of agar- and compost-grown plants of both species. Analyses were optimized using a genomic DNA (gDNA)-based probe-selection strategy based on the hybridization efficiency of Thlaspi gDNA with corresponding A. thaliana probes. In silico alignments of GeneChip® probes with Thlaspi gene sequences, and quantitative real-time PCR, confirmed the validity of this approach. • Approximately 5000 genes were differentially expressed in the shoots of T. caerulescens compared with T. arvense, including genes involved in Zn transport and compartmentalization. • Future functional analyses of genes identified as differentially expressed in the shoots of these closely related species will improve our understanding of the molecular mechanisms of Zn hyperaccumulation.
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nickel and zinc hyperaccumulation by alyssum murale and Thlaspi caerulescens brassicaceae do not enhance survival and whole plant growth under drought stress
Plant Cell and Environment, 2003Co-Authors: Steven N Whiting, Peter M. Neumann, A J M BakerAbstract:Nickel and Zn hyperaccumulation by Alyssum murale and Thlaspi caerulescens bear substantial energetic costs and should confer benefits to the plant. This research determined whether metal hyperaccumulation can increase osmotic adjustment and resistance to water stress (drought). Alyssum murale and Thlaspi caerulescens treated with low or high concentrations of Ni or Zn were exposed to moderate (−0·4 MPa) and severe (−1·0 MPa) water stresses using aqueous polyethylene glycol. In the absence of metals both water deficits inhibited shoot growth. Nickel and Zn hyperaccumulation did not ameliorate growth inhibition by either level of water stress. The water stress did not induce major changes in shoot metal concentrations of these constitutive hyperaccumulators. Moreover, metal hyperaccumulation had minimal effects on the osmolality of leaf-sap extracts, relative water content of the shoots, or rate of evapotranspiration. It is concluded that Ni or Zn hyperaccumulation does not augment whole-plant capacity for drought resistance in A. murale and T. caerulescens.
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assessment of zn mobilization in the rhizosphere of Thlaspi caerulescens by bioassay with non accumulator plants and soil extraction
Plant and Soil, 2001Co-Authors: Steven N Whiting, Stephen P Mcgrath, Jonathan R. Leake, A J M BakerAbstract:This study used co-cultivated plants as a bioassay to test the hypothesis that the roots of the zinc-hyperaccumulating plant Thlaspi caerulescensmobilize Zn from less-available pools in the soil. Thlaspi caerulescens was grown in uncompartmentalised pots, or pots that were divided by solid or mesh barriers to limit the extent of root intermingling (rhizosphere interaction) with co-cultivated Thlaspi arvense or Festuca rubra. Thlaspi caerulescens did not increase the concentration of Zn in either indicator species, suggesting that T. caerulescens does not strongly mobilize Zn in its rhizosphere. The increase in the shoot mass of T. arvense when its roots were permitted to intermingle with those of T. caerulescens was explained by greater intensity of competition of T. arvense compared to T. caerulescens.
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rhizosphere bacteria mobilize zn for hyperaccumulation by Thlaspi caerulescens
Environmental Science & Technology, 2001Co-Authors: Steven N Whiting, M P De Souza, Norman TerryAbstract:Thlaspi caerulescens has a remarkable ability to hyperaccumulate Zn from soils containing mostly nonlabile Zn. The present study shows that rhizosphere microbes play an important role in increasing the availability of water-soluble Zn in soil, thus enhancing Zn accumulation by T. caerulescens. The addition of bacteria to surface-sterilized seeds of T. caerulescens sown in autoclaved soil increased the Zn concentration in shoots 2-fold as compared to axenic controls; the total accumulation of Zn was enhanced 4-fold. When the same experiment was conducted with Thlaspi arvense, a nonaccumulator, bacteria had no effect on shoot Zn accumulation although they increased water-soluble Zn concentrations available to both Thlaspi species by 22−67% as compared to the axenic controls. Further evidence that bacteria increase the availability of water-soluble Zn in soil was obtained when liquid media that had supported bacterial growth mobilized 1.3−1.8-fold more Zn from soil as compared to axenic media. Other experime...
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hyperaccumulation of zn by Thlaspi caerulescens can ameliorate zn toxicity in the rhizosphere of cocropped Thlaspi arvense
Environmental Science & Technology, 2001Co-Authors: Steven N Whiting, S P Mcgrath, Jonathan R. Leake, A J M BakerAbstract:The metal hyperaccumulating plant Thlaspi caerulescens is effective in depleting plant-available metals from the soil. We hypothesized that this reduction of toxic metals in the rhizosphere of T. caerulescens would increase the growth of less metal-tolerant plants with their roots permitted to intermingle and develop coincident rhizospheres. The extent of rhizosphere interaction between T. caerulescens and a coplanted nonaccumulator species, Thlaspi arvense, was controlled using barriers. Two media with elevated concentrations of water-extractable Zn were prepared by enriching one soil with zinc oxide (ZnO) or zinc sulfide (ZnS). The shoot mass of T. arvense was increased by 30% when its roots were permitted to intermingle with those of T. caerulescens in the ZnO treatment. The concomitant 2−3-fold reduction in shoot Zn concentration in T. arvense confirmed that its improved growth was associated with reduced uptake and phytotoxicity of Zn. Thlaspi arvense also showed increased growth and reduced metal up...
