151
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Visioli G, Marmiroli N. The proteomics of heavy metal hyperaccumulation by plants. J Proteomics 2012; 79:133-45. [PMID: 23268120 DOI: 10.1016/j.jprot.2012.12.006] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2012] [Revised: 12/06/2012] [Accepted: 12/07/2012] [Indexed: 10/27/2022]
Abstract
Hyperaccumulators are distinguished from non-hyperaccumulators on the basis of their capacity to extract heavy metal ions from the soil, their more efficient root-to-shoot translocation of these ions and their greater ability to detoxify and sequester heavy metals in the shoot. The understanding of the mechanisms underlying metal ion accumulation has progressed beyond the relevant biochemistry and physiology to encompass the genetic and molecular regulatory systems which differentiate hyperaccumulators from non-hyperaccumulators. This paper reviews the literature surrounding the application of proteomics technology to plant metal hyperaccumulation, in particular involving the elements As, Cd, Cu, Ni, Pb and Zn. The hyperaccumulation process across a number of unrelated plant species appears to be associated with proteins involved in energy metabolism, the oxidative stress response and abiotic and biotic stress. The relevance of transducers of the metal stress response to the phenomenon of hyperaccumulation is summarized. Proteomic data complement the more voluminous genomic and transcriptomic data sets in providing a more nuanced picture of the process, and should therefore help in the identification of the major genetic determinants of the hyperaccumulation phenomenon.
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Affiliation(s)
- Giovanna Visioli
- Department of Life Sciences, University of Parma, Parco Area delle Scienze 11/a, 43124, Parma Italy
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152
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Gomes MP, Marques TCLLSEM, Martins GA, Carneiro MMLC, Soares ÂM. Cd-tolerance markers of Pfaffia glomerata (Spreng.) Pedersen plants: anatomical and physiological features. ACTA ACUST UNITED AC 2012. [DOI: 10.1590/s1677-04202012000400008] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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153
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Gallego SM, Pena LB, Barcia RA, Azpilicueta CE, Iannone MF, Rosales EP, Zawoznik MS, Groppa MD, Benavides MP. Unravelling cadmium toxicity and tolerance in plants: Insight into regulatory mechanisms. ENVIRONMENTAL AND EXPERIMENTAL BOTANY 2012. [PMID: 0 DOI: 10.1016/j.envexpbot.2012.04.006] [Citation(s) in RCA: 579] [Impact Index Per Article: 48.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
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154
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Degryse F, Shahbazi A, Verheyen L, Smolders E. Diffusion limitations in root uptake of cadmium and zinc, but not nickel, and resulting bias in the Michaelis constant. PLANT PHYSIOLOGY 2012; 160:1097-109. [PMID: 22864584 PMCID: PMC3461532 DOI: 10.1104/pp.112.202200] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/18/2012] [Accepted: 08/01/2012] [Indexed: 05/05/2023]
Abstract
It has long been recognized that diffusive boundary layers affect the determination of active transport parameters, but this has been largely overlooked in plant physiological research. We studied the short-term uptake of cadmium (Cd), zinc (Zn), and nickel (Ni) by spinach (Spinacia oleracea) and tomato (Lycopersicon esculentum) in solutions with or without metal complexes. At same free ion concentration, the presence of complexes, which enhance the diffusion flux, increased the uptake of Cd and Zn, whereas Ni uptake was unaffected. Competition effects of protons on Cd and Zn uptake were observed only at a very large degree of buffering, while competition of magnesium ions on Ni uptake was observed even in unbuffered solutions. These results strongly suggest that uptake of Cd and Zn is limited by diffusion of the free ion to the roots, except at very high degree of solution buffering, whereas Ni uptake is generally internalization limited. All results could be well described by a model that combined a diffusion equation with a competitive Michaelis-Menten equation. Direct uptake of the complex was estimated to be a major contribution only at millimolar concentrations of the complex or at very large ratios of complex to free ion concentration. The true K(m) for uptake of Cd(2+) and Zn(2+) was estimated at <5 nm, three orders of magnitude smaller than the K(m) measured in unbuffered solutions. Published Michaelis constants for plant uptake of Cd and Zn likely strongly overestimate physiological ones and should not be interpreted as an indicator of transporter affinity.
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Affiliation(s)
- Fien Degryse
- Laboratory for Soil and Water Management, Katholieke Universiteit Leuven, 3001 Heverlee, Belgium.
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155
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Lin YF, Aarts MGM. The molecular mechanism of zinc and cadmium stress response in plants. Cell Mol Life Sci 2012; 69:3187-206. [PMID: 22903262 PMCID: PMC11114967 DOI: 10.1007/s00018-012-1089-z] [Citation(s) in RCA: 350] [Impact Index Per Article: 29.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2012] [Revised: 07/09/2012] [Accepted: 07/09/2012] [Indexed: 01/09/2023]
Abstract
When plants are subjected to high metal exposure, different plant species take different strategies in response to metal-induced stress. Largely, plants can be distinguished in four groups: metal-sensitive species, metal-resistant excluder species, metal-tolerant non-hyperaccumulator species, and metal-hypertolerant hyperaccumulator species, each having different molecular mechanisms to accomplish their resistance/tolerance to metal stress or reduce the negative consequences of metal toxicity. Plant responses to heavy metals are molecularly regulated in a process called metal homeostasis, which also includes regulation of the metal-induced reactive oxygen species (ROS) signaling pathway. ROS generation and signaling plays an important duel role in heavy metal detoxification and tolerance. In this review, we will compare the different molecular mechanisms of nutritional (Zn) and non-nutritional (Cd) metal homeostasis between metal-sensitive and metal-adapted species. We will also include the role of metal-induced ROS signal transduction in this comparison, with the aim to provide a comprehensive overview on how plants cope with Zn/Cd stress at the molecular level.
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Affiliation(s)
- Ya-Fen Lin
- Laboratory of Genetics, Wageningen University, The Netherlands.
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156
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Tang YT, Cloquet C, Sterckeman T, Echevarria G, Carignan J, Qiu RL, Morel JL. Fractionation of stable zinc isotopes in the field-grown zinc hyperaccumulator Noccaea caerulescens and the zinc-tolerant plant Silene vulgaris. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2012; 46:9972-9979. [PMID: 22891730 DOI: 10.1021/es3015056] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Stable Zn isotope signatures offer a potential tool for tracing Zn uptake and transfer mechanisms within plant-soil systems. Zinc isotopic compositions were determined in the Zn hyperaccumulator Noccaea caerulescens collected at a Zn-contaminated site (Viviez), a serpentine site (Vosges), and a noncontaminated site (Sainte Eulalie) in France. Meanwhile, a Zn-tolerant plant ( Silene vulgaris ) was also collected at Viviez for comparison. While δ(66)Zn was substantially differentiated among N. caerulescens from the three localities, they all exhibited an enrichment in heavy Zn isotopes of 0.40-0.72‰ from soil to root, followed by a depletion in heavy Zn from root to shoot (-0.10 to -0.50‰). The enrichment of heavy Zn in roots is ascribed to the transport systems responsible for Zn absorption into root symplast and root-to-shoot translocation, while the depletion in heavy Zn in shoots is likely to be mediated by a diffusive process and an efficient translocation driven by energy-required transporters (e.g., NcHMA4). The mass balance yielded a bulk Zn isotopic composition between plant and soil (Δ(66)Zn(plant-soil)) of -0.01‰ to 0.63‰ in N. caerulescens , indicative of high- and/or low-affinity transport systems operating in the three ecotypes. In S. vulgaris , however, there was no significant isotope fractionation between whole plant and rhizosphere soil and between root and shoot, suggesting that this species appears to have a particular Zn homeostasis. We confirm that quantifying stable Zn isotopes is useful for understanding Zn accumulation mechanisms in plants.
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Affiliation(s)
- Ye-Tao Tang
- School of Environmental Science and Engineering, Sun Yat-sen University, Guangzhou 510275, People's Republic of China
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157
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Fernandez LR, Vandenbussche G, Roosens N, Govaerts C, Goormaghtigh E, Verbruggen N. Metal binding properties and structure of a type III metallothionein from the metal hyperaccumulator plant Noccaea caerulescens. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2012; 1824:1016-23. [DOI: 10.1016/j.bbapap.2012.05.010] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/24/2012] [Revised: 05/07/2012] [Accepted: 05/25/2012] [Indexed: 11/30/2022]
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158
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Gainza-Cortés F, Pérez-Dïaz R, Pérez-Castro R, Tapia J, Casaretto JA, González S, Peña-Cortés H, Ruiz-Lara S, González E. Characterization of a putative grapevine Zn transporter, VvZIP3, suggests its involvement in early reproductive development in Vitis vinifera L. BMC PLANT BIOLOGY 2012; 12:111. [PMID: 22824090 PMCID: PMC3432002 DOI: 10.1186/1471-2229-12-111] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/10/2012] [Accepted: 06/29/2012] [Indexed: 05/02/2023]
Abstract
BACKGROUND Zinc (Zn) deficiency is one of the most widespread mineral nutritional problems that affect normal development in plants. Because Zn cannot passively diffuse across cell membranes, it must be transported into intracellular compartments for all biological processes where Zn is required. Several members of the Zinc-regulated transporters, Iron-regulated transporter-like Protein (ZIP) gene family have been characterized in plants, and have shown to be involved in metal uptake and transport. This study describes the first putative Zn transporter in grapevine. Unravelling its function may explain an important symptom of Zn deficiency in grapevines, which is the production of clusters with fewer and usually smaller berries than normal. RESULTS We identified and characterized a putative Zn transporter from berries of Vitis vinifera L., named VvZIP3. Compared to other members of the ZIP family identified in the Vitis vinifera L. genome, VvZIP3 is mainly expressed in reproductive tissue - specifically in developing flowers - which correlates with the high Zn accumulation in these organs. Contrary to this, the low expression of VvZIP3 in parthenocarpic berries shows a relationship with the lower Zn accumulation in this tissue than in normal seeded berries where its expression is induced by Zn. The predicted protein sequence indicates strong similarity with several members of the ZIP family from Arabidopsis thaliana and other species. Moreover, VvZIP3 complemented the growth defect of a yeast Zn-uptake mutant, ZHY3, and is localized in the plasma membrane of plant cells, suggesting that VvZIP3 has the function of a Zn uptake transporter. CONCLUSIONS Our results suggest that VvZIP3 encodes a putative plasma membrane Zn transporter protein member of the ZIP gene family that might play a role in Zn uptake and distribution during the early reproductive development in Vitis vinifera L., indicating that the availability of this micronutrient may be relevant for reproductive development.
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Affiliation(s)
- Felipe Gainza-Cortés
- Instituto de Biología Vegetal y Biotecnología, Universidad de Talca, Talca, Chile
- Centro de Estudios Avanzados en Fruticultura (CEAF) CONICYT-Regional, GORE-O’Higgins R08I1001, Rengo, Chile
| | - Ricardo Pérez-Dïaz
- Instituto de Biología Vegetal y Biotecnología, Universidad de Talca, Talca, Chile
| | - Ramón Pérez-Castro
- Instituto de Biología Vegetal y Biotecnología, Universidad de Talca, Talca, Chile
- Laboratorio de Investigaciones Biomédicas, Facultad de Medicina, Universidad Católica del Maule, Talca, Chile
| | - Jaime Tapia
- Instituto de Química de Recursos Naturales, Universidad de Talca, Talca, Chile
| | - José A Casaretto
- Instituto de Biología Vegetal y Biotecnología, Universidad de Talca, Talca, Chile
| | - Sebastián González
- Instituto de Biología Vegetal y Biotecnología, Universidad de Talca, Talca, Chile
| | - Hugo Peña-Cortés
- Centro de Biotecnología Daniel Alkalay Lowitt, Universidad Federico Santa María, Valparaíso, Chile
| | - Simón Ruiz-Lara
- Instituto de Biología Vegetal y Biotecnología, Universidad de Talca, Talca, Chile
| | - Enrique González
- Instituto de Biología Vegetal y Biotecnología, Universidad de Talca, Talca, Chile
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159
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Li T, Xu Z, Han X, Yang X, Sparks DL. Characterization of dissolved organic matter in the rhizosphere of hyperaccumulator Sedum alfredii and its effect on the mobility of zinc. CHEMOSPHERE 2012; 88:570-576. [PMID: 22475152 DOI: 10.1016/j.chemosphere.2012.03.031] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/31/2011] [Revised: 02/29/2012] [Accepted: 03/08/2012] [Indexed: 05/31/2023]
Abstract
Pot experiments were performed to investigate the characteristics of dissolved organic matter (DOM) in the rhizosphere soil of hyperaccumulating ecotype (HE) and a non-hyperaccumulating ecotype (NHE) of Sedum alfredii and its effects on the mobility of zinc (Zn). DOM was fractionated using XAD resins into six fractions. The acid fraction was the predominant component of DOM in the rhizosphere of S. alfredii, with hydrophilic acid (HiA), hydrophilic base (HiB), and hydrophilic neutral (HiN) in HE-DOM being 1.6, 1.9, and 1.2 times higher respectively, as compared to NHE-DOM. ATR-FTIR results showed that DOM in the rhizosphere of S. alfredii consisted of a mixture of hydroxylated and carboxylic acids, and HE-DOM exhibited more CO, OH, CC and CO functional groups than NHE-DOM. Resin equilibration experiment results indicated that DOM from the rhizosphere of both ecotypes of S. alfredii had the ability to form complexes with Zn, whereas the degree of complexation was significantly higher for HE-DOM (60%) than NHE-DOM (42%). The addition of HE-DOM significantly (P<0.05) increased the solubility of four Zn minerals while NHE-DOM was not as effective at the same concentration. It was concluded that DOM derived from the rhizosphere of hyperaccumulating ecotype of S. alfredii could significantly increase Zn mobility through the formation of soluble DOM-metal complexes, this might be one of the important mechanism by which S. alfredii is involved in activating metal in rhizosphere.
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Affiliation(s)
- Tingqiang Li
- Ministry of Education Key Laboratory of Environmental Remediation and Ecological Health, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou, China.
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160
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Milner MJ, Craft E, Yamaji N, Koyama E, Ma JF, Kochian LV. Characterization of the high affinity Zn transporter from Noccaea caerulescens, NcZNT1, and dissection of its promoter for its role in Zn uptake and hyperaccumulation. THE NEW PHYTOLOGIST 2012; 195:113-23. [PMID: 22524643 DOI: 10.1111/j.1469-8137.2012.04144.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
• In this paper, we conducted a detailed analysis of the ZIP family transporter, NcZNT1, in the zinc (Zn)/cadmium (Cd) hyperaccumulating plant species, Noccaea caerulescens, formerly known as Thlaspi caerulescens. NcZNT1 was previously suggested to be the primary root Zn/Cd uptake transporter. Both a characterization of NcZNT1 transport function in planta and in heterologous systems, and an analysis of NcZNT1 gene expression and NcZNT1 protein localization were carried out. • We show that NcZNT1 is not only expressed in the root epidermis, but also is highly expressed in the root and shoot vasculature, suggesting a role in long-distance metal transport. Also, NcZNT1 was found to be a plasma membrane transporter that mediates Zn but not Cd, iron (Fe), manganese (Mn) or copper (Cu) uptake into plant cells. • Two novel regions of the NcZNT1 promoter were identified which may be involved in both the hyperexpression of NcZNT1 and its ability to be regulated by plant Zn status. • In conclusion, we demonstrate here that NcZNT1 plays a role in Zn and not Cd uptake from the soil, and based on its strong expression in the root and shoot vasculature, could be involved in long-distance transport of Zn from the root to the shoot via the xylem.
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Affiliation(s)
- Matthew J Milner
- Robert W. Holley Center for Agriculture and Health, USDA-ARS, Cornell University, Ithaca, NY 14853, USA
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161
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Molecular Mechanism of Heavy Metal Toxicity and Tolerance in Plants: Central Role of Glutathione in Detoxification of Reactive Oxygen Species and Methylglyoxal and in Heavy Metal Chelation. ACTA ACUST UNITED AC 2012. [DOI: 10.1155/2012/872875] [Citation(s) in RCA: 432] [Impact Index Per Article: 36.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Heavy metal (HM) toxicity is one of the major abiotic stresses leading to hazardous effects in plants. A common consequence of HM toxicity is the excessive accumulation of reactive oxygen species (ROS) and methylglyoxal (MG), both of which can cause peroxidation of lipids, oxidation of protein, inactivation of enzymes, DNA damage and/or interact with other vital constituents of plant cells. Higher plants have evolved a sophisticated antioxidant defense system and a glyoxalase system to scavenge ROS and MG. In addition, HMs that enter the cell may be sequestered by amino acids, organic acids, glutathione (GSH), or by specific metal-binding ligands. Being a central molecule of both the antioxidant defense system and the glyoxalase system, GSH is involved in both direct and indirect control of ROS and MG and their reaction products in plant cells, thus protecting the plant from HM-induced oxidative damage. Recent plant molecular studies have shown that GSH by itself and its metabolizing enzymes—notably glutathione S-transferase, glutathione peroxidase, dehydroascorbate reductase, glutathione reductase, glyoxalase I and glyoxalase II—act additively and coordinately for efficient protection against ROS- and MG-induced damage in addition to detoxification, complexation, chelation and compartmentation of HMs. The aim of this review is to integrate a recent understanding of physiological and biochemical mechanisms of HM-induced plant stress response and tolerance based on the findings of current plant molecular biology research.
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162
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Adams JP, Adeli A, Hsu CY, Harkess RL, Page GP, Depamphilis CW, Schultz EB, Yuceer C. Plant-based FRET biosensor discriminates environmental zinc levels. PLANT BIOTECHNOLOGY JOURNAL 2012; 10:207-216. [PMID: 21910820 DOI: 10.1111/j.1467-7652.2011.00656.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Heavy metal accumulation in the environment poses great risks to flora and fauna. However, monitoring sites prone to accumulation poses scale and economic challenges. In this study, we present and test a method for monitoring these sites using fluorescent resonance energy transfer (FRET) change in response to zinc (Zn) accumulation in plants as a proxy for environmental health. We modified a plant Zn transport protein by adding flanking fluorescent proteins (FPs) and deploying the construct into two different species. In Arabidopsis thaliana, FRET was monitored by a confocal microscope and had a 1.4-fold increase in intensity as the metal concentration increased. This led to a 16.7% overall error-rate when discriminating between a control (1μm Zn) and high (10mm Zn) treatment after 96h. The second host plant (Populus tremula×Populu salba) also had greater FRET values (1.3-fold increase) when exposed to the higher concentration of Zn, while overall error-rates were greater at 22.4%. These results indicate that as plants accumulate Zn, protein conformational changes occur in response to Zn causing differing interaction between FPs. This results in greater FRET values when exposed to greater amounts of Zn and monitored with appropriate light sources and filters. We also demonstrate how this construct can be moved into different host plants effectively including one tree species. This chimeric protein potentially offers a method for monitoring large areas of land for Zn accumulation, is transferable among species, and could be modified to monitor other specific heavy metals that pose environmental risks.
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Affiliation(s)
- Joshua P Adams
- School of Forest Resources, University of Arkansas at Monticello, Monticello, AR, USA.
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163
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Zhou ZS, Zeng HQ, Liu ZP, Yang ZM. Genome-wide identification of Medicago truncatula microRNAs and their targets reveals their differential regulation by heavy metal. PLANT, CELL & ENVIRONMENT 2012; 35:86-99. [PMID: 21895696 DOI: 10.1111/j.1365-3040.2011.02418.x] [Citation(s) in RCA: 75] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
We adopted a deep sequencing approach developed by Solexa (Illumina Inc., San Diego, CA, USA) to investigate global expression and complexity of microRNAs (miRNAs) and their targets from Medicago truncatula. Two small RNA libraries and two degradome libraries were constructed from mercury (Hg)-treated and Hg-free M. truncatula seedlings. For miRNAs, each library generated 18.5-18.6 million short sequences, resulting in 10.2-10.8 million clean reads. At least 52 new miRNA candidates with ≈ 21 nucleotides are perfectly matched to the M. truncatula genome. Statistical analysis on transcript abundance of the new candidate miRNAs revealed that most of them were differentially regulated by the heavy metal mercury Hg(II), with 12 miRNAs being specifically induced by Hg exposure. Additionally, we identified 201 individual miRNAs representing 63 known M. truncatula miRNA families, including 12 new conserved and one non-conserved miRNAs that have not been described before. Finally, 130 targets for 58 known (37 conserved and 21 non-conserved) miRNA families and 37 targets for 18 new M. truncatula-specific candidate miRNA families were identified by high-throughput degradome sequencing approach.
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Affiliation(s)
- Zhao Sheng Zhou
- Department of Biochemistry and Molecular Biology, College of Life Science, Nanjing Agricultural University, Nanjing, China
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164
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165
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Li L, Liu X, Peijnenburg WJGM, Zhao J, Chen X, Yu J, Wu H. Pathways of cadmium fluxes in the root of the halophyte Suaeda salsa. ECOTOXICOLOGY AND ENVIRONMENTAL SAFETY 2012; 75:1-7. [PMID: 21943551 DOI: 10.1016/j.ecoenv.2011.09.007] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/08/2011] [Revised: 09/05/2011] [Accepted: 09/11/2011] [Indexed: 05/27/2023]
Abstract
Halophyte plants offer a greater potential for phytoremediation research for reducing the levels of toxic metals from saline soils than salt sensitive plants. Using the scanning ion-selective electrode technique, we analyzed the pattern and rate of Cd(2+) fluxes at different regions of the root apex of Suaeda salsa. The Cd(2+) influx in the rhizosphere was greatest near the root tip (within 150μm of the tip). The results indicated that Cd(2+) influx into roots was significantly suppressed by the pre-treatment or in the presence of two kinds of Ca(2+) channel blockers; LaCl(3) and verapamil. The Cd(2+) influx was also reduced by N-ethylmaleimide, a thiol blocker. Cd content determination and labeling of Cd using fluorescent dye support our conclusion. The results of this study provide a more stable theoretical basis for the phytoremediation of Cd contamination in saline soils of coastal zones.
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Affiliation(s)
- Lianzhen Li
- Yantai Institute of Coastal Zone Research, Chinese Academy of Sciences, Yantai, People's Republic of China
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166
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Biochemical and Functional Responses of Arabidopsis thaliana Exposed to Cadmium, Copper and Zinc. THE PLANT FAMILY BRASSICACEAE 2012. [DOI: 10.1007/978-94-007-3913-0_9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/06/2022]
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167
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Mahmood Q, Rashid A, Ahmad SS, Azim MR, Bilal M. Current Status of Toxic Metals Addition to Environment and Its Consequences. THE PLANT FAMILY BRASSICACEAE 2012. [DOI: 10.1007/978-94-007-3913-0_2] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/04/2022]
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168
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Gao HW, Ma DD, Xu G. Medicinal plant acid-treatment for a healthier herb tea and recycling of the spent herb residue. RSC Adv 2012. [DOI: 10.1039/c2ra20429k] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
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169
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Tian S, Lu L, Labavitch J, Yang X, He Z, Hu H, Sarangi R, Newville M, Commisso J, Brown P. Cellular sequestration of cadmium in the hyperaccumulator plant species Sedum alfredii. PLANT PHYSIOLOGY 2011; 157:1914-25. [PMID: 22025609 PMCID: PMC3327216 DOI: 10.1104/pp.111.183947] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/22/2011] [Accepted: 10/23/2011] [Indexed: 05/03/2023]
Abstract
Spatial imaging of cadmium (Cd) in the hyperaccumulator Sedum alfredii was investigated in vivo by laser ablation inductively coupled plasma mass spectrometry and x-ray microfluorescence imaging. Preferential Cd accumulation in the pith and cortex was observed in stems of the Cd hyperaccumulating ecotype (HE), whereas Cd was restricted to the vascular bundles in its contrasting nonhyperaccumulating ecotype. Cd concentrations of up to 15,000 μg g(-1) were measured in the pith cells, which was many fold higher than the concentrations in the stem epidermis and vascular bundles in the HE plants. In the leaves of the HE, Cd was mainly localized to the mesophyll and vascular cells rather than the epidermis. The distribution pattern of Cd in both stems and leaves of the HE was very similar to calcium but not zinc, irrespective of Cd exposure levels. Extended x-ray absorption fine structure spectroscopy analysis showed that Cd in the stems and leaves of the HE was mainly associated with oxygen ligands, and a larger proportion (about 70% in leaves and 47% in stems) of Cd was bound with malic acid, which was the major organic acid in the shoots of the plants. These results indicate that a majority of Cd in HE accumulates in the parenchyma cells, especially in stems, and is likely associated with calcium pathways and bound with organic acid (malate), which is indicative of a critical role of vacuolar sequestration of Cd in the HE S. alfredii.
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Affiliation(s)
| | | | | | - Xiaoe Yang
- Ministry of Education Key Laboratory of Environment Remediation and Ecological Health, College of Environmental and Resource Science, Zhejiang University, Hangzhou 310058, China (S.T., L.L., X.Y.); Department of Plant Sciences, University of California, Davis, California 95616 (S.T., L.L., J.L., H.H., J.C., P.B.); Indian River Research and Education Center, Institute of Food and Agricultural Science, University of Florida, Fort Pierce, Florida 34945 (Z.H.); Stanford Synchrotron Radiation Lightsource, Stanford Linear Accelerator Center National Accelerator Laboratory, Menlo Park, California 94025 (R.S.); GSECARS Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439 (M.N.)
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170
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Wang X, Song Y, Ma Y, Zhuo R, Jin L. Screening of Cd tolerant genotypes and isolation of metallothionein genes in alfalfa (Medicago sativa L.). ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2011; 159:3627-3633. [PMID: 21868142 DOI: 10.1016/j.envpol.2011.08.001] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/03/2011] [Revised: 07/10/2011] [Accepted: 08/01/2011] [Indexed: 05/27/2023]
Abstract
In order to evaluate Cd tolerance in wide-ranging sources of alfalfa (Medicago sativa) and to identify Cd tolerant genotypes which may potentially be useful for restoring Cd-contaminated environments, thirty-six accessions of alfalfa were screened under hydroponic culture. Our results showed that the relative root growth rate varied from 0.48 to 1.0, which indicated that different alfalfa accessions had various responses to Cd stress. The candidate fragments derived from differentially expressed metallothionein (MT) genes were cloned from leaves of two Cd tolerant genotypes, YE and LZ. DNA sequence and the deduced protein sequence showed that MsMT2a and MsMT2b had high similarity to those in leguminous plants. DDRT-PCR analysis showed that MsMT2a expressed in both YE and LZ plants under control and Cd stress treatment, but MsMT2b only expressed under Cd stress treatment. This suggested that MsMT2a was universally expressed in leaves of alfalfa but expression of MsMT2b was Cadmium (Cd) inducible.
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Affiliation(s)
- Xiaojuan Wang
- School of Pastoral Agriculture Science and Technology, Lanzhou University, PO Box 61, Lanzhou 730020, China.
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171
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Kulaeva OA, Tsyganov VE. Molecular-genetic basis of cadmium tolerance and accumulation in higher plants. ACTA ACUST UNITED AC 2011. [DOI: 10.1134/s2079059711050108] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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172
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Leitenmaier B, Witt A, Witzke A, Stemke A, Meyer-Klaucke W, Kroneck PM, Küpper H. Biochemical and biophysical characterisation yields insights into the mechanism of a Cd/Zn transporting ATPase purified from the hyperaccumulator plant Thlaspi caerulescens. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2011; 1808:2591-9. [DOI: 10.1016/j.bbamem.2011.05.010] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/01/2011] [Revised: 05/10/2011] [Accepted: 05/11/2011] [Indexed: 01/05/2023]
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173
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Mechanisms of Cd Hyperaccumulation and Detoxification in Heavy Metal Hyperaccumulators: How Plants Cope with Cd. ACTA ACUST UNITED AC 2011. [DOI: 10.1007/978-3-642-22746-2_5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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174
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Li T, Di Z, Yang X, Sparks DL. Effects of dissolved organic matter from the rhizosphere of the hyperaccumulator Sedum alfredii on sorption of zinc and cadmium by different soils. JOURNAL OF HAZARDOUS MATERIALS 2011; 192:1616-1622. [PMID: 21782330 DOI: 10.1016/j.jhazmat.2011.06.086] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/12/2011] [Revised: 06/06/2011] [Accepted: 06/29/2011] [Indexed: 05/31/2023]
Abstract
Pot experiments were conducted to investigate the changes of the dissolved organic matter (DOM) in the rhizosphere of hyperaccumulating ecotype (HE) and non-hyperaccumulating ecotype (NHE) of Sedum alfredii and its effects on Zn and Cd sorption by soils. After planted with HE, soil pH in the rhizosphere reduced by 0.5-0.6 units which is consistent with the increase of DOM. The hydrophilic fractions (51%) in DOM from the rhizosphere of HE (HE-DOM) was much greater than NHE-DOM (35%). In the presence of HE-DOM, Zn and Cd sorption capacity decreased markedly in the following order: calcareous clay loam>neutral clay loam>acidic silty clay. The sorption isotherms could be well described by the Freundlich equation (R(2)>0.95), and the partition coefficient (K) in the presence of HE-DOM was decreased by 30.7-68.8% for Zn and 20.3-59.2% for Cd, as compared to NHE-DOM. An increase in HE-DOM concentration significantly reduced the sorption and increased the desorption of Zn and Cd by three soils. DOM derived from the rhizosphere of the hyperaccumulating ecotype of S. alfredii could significantly reduce metal sorption and increase its mobility through the formation of soluble DOM-metal complexes.
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Affiliation(s)
- Tingqiang Li
- Ministry of Education, Key Laboratory of Environmental Remediation and Ecosystem Health, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou 310029, China.
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175
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Zhao L, Sun YL, Cui SX, Chen M, Yang HM, Liu HM, Chai TY, Huang F. Cd-induced changes in leaf proteome of the hyperaccumulator plant Phytolacca americana. CHEMOSPHERE 2011; 85:56-66. [PMID: 21723586 DOI: 10.1016/j.chemosphere.2011.06.029] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/10/2011] [Revised: 05/24/2011] [Accepted: 06/05/2011] [Indexed: 05/28/2023]
Abstract
Cadmium (Cd) is highly toxic to all organisms. Soil contamination by Cd has become an increasing problem worldwide due to the intensive use of Cd-containing phosphate fertilizers and industrial zinc mining. Phytolacca americana L. is a Cd hyperaccumulator plant that can grow in Cd-polluted areas. However, the molecular basis for its remarkable Cd resistance is not known. In this study, the effects of Cd exposure on protein expression patterns in P.americana was investigated by 2-dimensional gel electrophoresis (2-DE). 2-DE profiles of leaf proteins from both control and Cd-treated (400μM, 48h) seedlings were compared quantitatively using ImageMaster software. In total, 32 differentially expressed protein spots were identified using MALDI-TOF/TOF mass spectrometry coupled to protein database search, corresponding to 25 unique gene products. Of those 14 were enhanced/induced while 11 reduced under Cd treatment. The alteration pattern of protein expression was verified for several key proteins involved in distinct metabolic pathways by immuno-blot analysis. Major changes were found for the proteins involved in photosynthetic pathways as well as in the sulfur- and GSH-related metabolisms. One-third of the up-regulated proteins were attributed to transcription, translation and molecular chaperones including a protein belonging to the calreticulin family. Other proteins include antioxidative enzymes such as 2-cys-peroxidase and oxidoreductases. The results of this proteomic analysis provide the first and primary information regarding the molecular basis of Cd hypertolerance in P. americana.
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Affiliation(s)
- Le Zhao
- Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
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176
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177
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Ueno D, Milner MJ, Yamaji N, Yokosho K, Koyama E, Clemencia Zambrano M, Kaskie M, Ebbs S, Kochian LV, Ma JF. Elevated expression of TcHMA3 plays a key role in the extreme Cd tolerance in a Cd-hyperaccumulating ecotype of Thlaspi caerulescens. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2011; 66:852-62. [PMID: 21457363 DOI: 10.1111/j.1365-313x.2011.04548.x] [Citation(s) in RCA: 142] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Cadmium (Cd) is a highly toxic heavy metal for plants, but several unique Cd-hyperaccumulating plant species are able to accumulate this metal to extraordinary concentrations in the aboveground tissues without showing any toxic symptoms. However, the molecular mechanisms underlying this hypertolerance to Cd are poorly understood. Here we have isolated and functionally characterized an allelic gene, TcHMA3 (heavy metal ATPase 3) from two ecotypes (Ganges and Prayon) of Thlaspi caerulescens contrasting in Cd accumulation and tolerance. The TcHMA3 alleles from the higher (Ganges) and lower Cd-accumulating ecotype (Prayon) share 97.8% identity, and encode a P(1B)-type ATPase. There were no differences in the expression pattern, cell-specificity of protein localization and transport substrate-specificity of TcHMA3 between the two ecotypes. Both alleles were characterized by constitutive expression in the shoot and root, a tonoplast localization of the protein in all leaf cells and specific transport activity for Cd. The only difference between the two ecotypes was the expression level of TcHMA3: Ganges showed a sevenfold higher expression than Prayon, partly caused by a higher copy number. Furthermore, the expression level and localization of TcHMA3 were different from AtHMA3 expression in Arabidopsis. Overexpression of TcHMA3 in Arabidopsis significantly enhanced tolerance to Cd and slightly increased tolerance to Zn, but did not change Co or Pb tolerance. These results indicate that TcHMA3 is a tonoplast-localized transporter highly specific for Cd, which is responsible for sequestration of Cd into the leaf vacuoles, and that a higher expression of this gene is required for Cd hypertolerance in the Cd-hyperaccumulating ecotype of T. caerulescens.
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Affiliation(s)
- Daisei Ueno
- Institute of Plant Science and Resources, Okayama University, Chuo 2-20-1, Kurashiki 710-0046, Japan
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178
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Singh BR, Gupta SK, Azaizeh H, Shilev S, Sudre D, Song WY, Martinoia E, Mench M. Safety of food crops on land contaminated with trace elements. JOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE 2011; 91:1349-1366. [PMID: 21445857 DOI: 10.1002/jsfa.4355] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/03/2009] [Revised: 08/20/2010] [Accepted: 09/22/2010] [Indexed: 05/30/2023]
Abstract
Contamination of agricultural soils with trace elements (TEs) through municipal and industrial wastes, atmospheric deposition and fertilisers is a matter of great global concern. Since TE accumulation in edible plant parts depends on soil characteristics, plant genotype and agricultural practices, those soil- and plant-specific options that restrict the entry of harmful TEs into the food chain to protect human and animal health are reviewed. Soil options such as in situ stabilisation of TEs in soils, changes in physicochemical parameters, fertiliser management, element interactions and agronomic practices reduce TE uptake by food crops. Furthermore, phytoremediation and solubilisation as alternative techniques to reduce TE concentrations in soils are also discussed. Among plant options, selection of species and cultivars, metabolic processes and microbial transformations in the rhizosphere can potentially affect TE uptake and distribution in plants. For this purpose, genetic variations are exploited to select cultivars with low uptake potential, especially low-cadmium accumulator wheat and rice cultivars. The microbial reduction of elements and transformations in the rhizosphere are other key players in the cycling of TEs that may offer the basis for a wide range of innovative biotechnological processes. It is thus concluded that appropriate combination of soil- and plant-specific options can minimise TE transfer to the food chain.
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Affiliation(s)
- Bal Ram Singh
- Department of Plant and Environmental Sciences, Norwegian University of Life Sciences (UMB), PO Box 5003, N-1432 Ås, Norway.
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179
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Miransari M. Hyperaccumulators, arbuscular mycorrhizal fungi and stress of heavy metals. Biotechnol Adv 2011; 29:645-53. [PMID: 21557996 DOI: 10.1016/j.biotechadv.2011.04.006] [Citation(s) in RCA: 148] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2011] [Revised: 04/02/2011] [Accepted: 04/21/2011] [Indexed: 10/18/2022]
Abstract
Use of plants, with hyperaccumulating ability or in association with soil microbes including the symbiotic fungi, arbuscular mycorrhiza (AM), are among the most common biological methods of treating heavy metals in soil. Both hyperaccumulating plants and AM fungi have some unique abilities, which make them suitable to treat heavy metals. Hyperaccumulator plants have some genes, being expressed at the time of heavy metal pollution, and can accordingly localize high concentration of heavy metals to their tissues, without showing the toxicity symptoms. A key solution to the issue of heavy metal pollution may be the proper integration of hyperaccumulator plants and AM fungi. The interactions between the soil microbes and the host plant can also be important for the treatment of soils polluted with heavy metals.
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Affiliation(s)
- Mohammad Miransari
- Department of Soil Science, College of Agricultural Sciences, Shahed University, Tehran, Qom Highway, Tehran 18151/159, Iran.
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180
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Waters BM, Sankaran RP. Moving micronutrients from the soil to the seeds: genes and physiological processes from a biofortification perspective. PLANT SCIENCE : AN INTERNATIONAL JOURNAL OF EXPERIMENTAL PLANT BIOLOGY 2011; 180:562-74. [PMID: 21421405 DOI: 10.1016/j.plantsci.2010.12.003] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/21/2010] [Revised: 11/23/2010] [Accepted: 12/03/2010] [Indexed: 05/04/2023]
Abstract
The micronutrients iron (Fe), zinc (Zn), and copper (Cu) are essential for plants and the humans and animals that consume plants. Increasing the micronutrient density of staple crops, or biofortification, will greatly improve human nutrition on a global scale. This review discusses the processes and genes needed to translocate micronutrients through the plant to the developing seeds, and potential strategies for developing biofortified crops.
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Affiliation(s)
- Brian M Waters
- Department of Agronomy and Horticulture, University of Nebraska, Lincoln, NE 68583-0915, USA.
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181
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Wang Y, Zong K, Jiang L, Sun J, Ren Y, Sun Z, Wen C, Chen X, Cao S. Characterization of an Arabidopsis cadmium-resistant mutant cdr3-1D reveals a link between heavy metal resistance as well as seed development and flowering. PLANTA 2011; 233:697-706. [PMID: 21165647 DOI: 10.1007/s00425-010-1328-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/26/2010] [Accepted: 11/23/2010] [Indexed: 05/16/2023]
Abstract
A lot of studies have identified many key genes involved in heavy metal detoxification and tolerance in plants; however, our understanding of its molecular mechanisms is far from complete. To gain insight into the regulatory mechanisms for heavy metal detoxification and tolerance, we performed a mutant screen for identifying Arabidopsis (Arabidopsis thaliana) cadmium (Cd)-resistant mutants. A Cd-resistant mutant cdr3-1D (c a d mium-r esistant) was isolated because of its increased root growth and fresh weight in Cd stress, and genetic analysis showed that cdr3-1D is a single dominant nuclear mutation. Compared with the wild type, the cdr3-1D mutant was more resistant to heavy metals Cd, Pb, and copper as well as hydrogen peroxide. Moreover, we also observed that seeds of the cdr3-1D mutant were larger than those of wild type, and that cdr3-1D displayed early flowering compared with wild type. A lower Cd/Pb content was detected in cdr3-1D plants than in wild-type plants when subjected to Cd/Pb treatment, which was associated, at least in part, with increase of expression of AtPDR8/AtPDR12, a pump excluding Cd/Pb and/or Cd/Pb-containing toxic compounds from the cytoplasm, respectively. In addition, enhanced Cd/Pb resistance of the cdr3-1D mutant was partially glutathione (GSH) dependent, which was related to increase of expression of GSH1 gene involved in GSH synthesis and consequently increased GSH content. Taken together, our results provide genetic evidence indicating that CDR3 is involved in the regulation of heavy metal resistance as well as seed development and flowering.
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Affiliation(s)
- Yang Wang
- School of Biotechnology and Food Engineering Hefei University of Technology, No. 193 Tunxi Road, Hefei, 230009, Anhui, People's Republic of China
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182
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Qiu RL, Thangavel P, Hu PJ, Senthilkumar P, Ying RR, Tang YT. Interaction of cadmium and zinc on accumulation and sub-cellular distribution in leaves of hyperaccumulator Potentilla griffithii. JOURNAL OF HAZARDOUS MATERIALS 2011; 186:1425-30. [PMID: 21211902 DOI: 10.1016/j.jhazmat.2010.12.014] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/18/2010] [Revised: 10/17/2010] [Accepted: 12/06/2010] [Indexed: 05/25/2023]
Abstract
Potentilla griffithii Hook is a newly found hyperaccumulator plant capable of high tolerance and accumulation of Zn and Cd. We investigated the interactive effects between Cd and Zn on accumulation and vacuolar sequestration in P. griffithii. Stimulatory effect of growth was noted at 0.2 mM Cd and 1.25 and 2.5 mM Zn tested. Accumulation of Zn and Cd in roots, petioles and leaves were increased significantly with addition of these metals individually. However, the Zn supplement decreased root Cd accumulation but increased the concentration of Cd in petioles and leaves. The results from sub-cellular distribution showed that up to 94% and 70% of the total Zn and Cd in the leaves were present in the protoplasts, and more than 90% Cd and Zn in the protoplasts were localized in the vacuoles. Nearly, 88% and 85% of total Cd and Zn were extracted in the cell sap of the leaves suggesting that most of the Cd and Zn in the leaves were available in soluble form. The present results indicate that Zn supplement significantly enhanced the petiole accumulation of Cd and further vacuolar sequestration plays an important role in tolerance, detoxification and hyperaccumulation of these metals in P. griffithii.
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Affiliation(s)
- Rong-Liang Qiu
- School of Environmental Science and Engineering, Sun Yat-Sen University, Guangzhou 510275, PR China.
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183
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Kudo H, Kudo K, Ambo H, Uemura M, Kawai S. Cadmium sorption to plasma membrane isolated from barley roots is impeded by copper association onto membranes. PLANT SCIENCE : AN INTERNATIONAL JOURNAL OF EXPERIMENTAL PLANT BIOLOGY 2011; 180:300-305. [PMID: 21421374 DOI: 10.1016/j.plantsci.2010.09.008] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/23/2010] [Accepted: 09/22/2010] [Indexed: 05/30/2023]
Abstract
The present study was designed to examine the effect of copper (Cu) on sorption of cadmium (Cd) to plasma membrane (PM) preparations as one of the models of competition between metals on root PM. Plasma membrane preparations were obtained from roots of barley (Hordeum vulgare L. cv. Minorimugi) and 50 μM CdSO₄ with or without 50 μM CuSO₄ were added to the PM suspensions. The sorption of Cd to PM vesicles increased with time within 15 min while Cu sorption to the PM occurred instantaneously. The sorption of Cd to PM vesicles was inactivated immediately after the addition of Cu into the reaction mixture. Results indicate that Cu association to PM vesicles occurs quicker than Cd, and, as a result, impedes the access of Cd to PM vesicles. The present study suggests that the competition between Cd and other minerals at root PM of plants can be demonstrated by employing isolated PM preparations. We consider that the difference in the capacity among some minerals for impeding Cd sorption to PM may also be characterized by investigating the interaction between Cd and other minerals on the PM.
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Affiliation(s)
- Hiroaki Kudo
- The United Graduate School of Agricultural Sciences, Iwate University, 3-18-8 Ueda, Morioka 020-8550, Japan.
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184
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Leitenmaier B, Küpper H. Cadmium uptake and sequestration kinetics in individual leaf cell protoplasts of the Cd/Zn hyperaccumulator Thlaspi caerulescens. PLANT, CELL & ENVIRONMENT 2011; 34:208-19. [PMID: 20880204 DOI: 10.1111/j.1365-3040.2010.02236.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Hyperaccumulators store accumulated metals in the vacuoles of large leaf epidermal cells (storage cells). For investigating cadmium uptake, we incubated protoplasts obtained from leaves of Thlaspi caerulescens (Ganges ecotype) with a Cd-specific fluorescent dye. A fluorescence kinetic microscope was used for selectively measuring Cd-uptake and photosynthesis in different cell types, so that physical separation of cell types was not necessary. Few minutes after its addition, cadmium accumulated in the cytoplasm before its transport into the vacuole. This demonstrated that vacuolar sequestration is the rate-limiting step in cadmium uptake into protoplasts of all leaf cell types. During accumulation in the cytoplasm, Cd-rich vesicle-like structures were observed. Cd uptake rates into epidermal storage cells were higher than into standard-sized epidermal cells and mesophyll cells. This shows that the preferential heavy metal accumulation in epidermal storage cells, previously observed for several metals in intact leaves of various hyperaccumulator species, is due to differences in active metal transport and not differences in passive mechanisms like transpiration stream transport or cell wall adhesion. Combining this with previous studies, it seems likely that the transport steps over the plasma and tonoplast membranes of leaf epidermal storage cells are driving forces behind the hyperaccumulation phenotype.
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185
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Hou L, Shi W, Wei W, Shen H. Cadmium uptake, translocation, and tolerance in AHA1OX Arabidopsis thaliana. Biol Trace Elem Res 2011; 139:228-40. [PMID: 20229360 DOI: 10.1007/s12011-010-8657-6] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/05/2010] [Accepted: 02/17/2010] [Indexed: 10/19/2022]
Abstract
Information on cadmium (Cd) uptake and transport is essential to understand better the physiology of Cd tolerance in plants. In this study, Cd uptake, translocation, and tolerance were investigated in AHA1 (Arabidopsis plasma membrane H(+)-ATPase gene) overexpressed plants. Exposed to 10 µM CdCl(2), AHA1OX showed a higher root elongation, accumulated more Cd, and maintained better integrity of nucleus membrane of root tips in comparison to the control plant (WT), suggesting that AHA1OX was more Cd tolerant than WT. To investigate Cd tolerance mechanism of AHA1OX plants, we measured the activity of plasma membrane H(+)-ATPase and the secretion of citrate. Results indicated that treatment with 10 µM of Cd stimulated the activity of plasma membrane H(+)-ATPase and the secretion of citrate, while 30 µM of Cd inhibited them. AHA1OX had higher activity of H(+)-ATPase and secretion of citrate than WT. Addition of citrate enhanced root-to-shoot translocation of Cd significantly. A higher root-to-shoot Cd translocation was observed in AHA1OX than in WT plants. Treatment with low temperature or metabolic inhibitor (carbonyl cyanide m-chlorophenylhydrazone) inhibited Cd uptake and translocation. The study of Cd forms using sequential extraction indicated that Cd was mainly present as a protein-bound form, and AHA1OX had more water-soluble Cd than WT. Taken together, our results suggested that the Cd tolerance of AHA1OX was associated with its root-to-shoot Cd translocation and secretion of citrate, which converts Cd(2+) into less toxic and more easily transportable forms in plant cells.
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Affiliation(s)
- Lingyan Hou
- Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, China.
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186
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Li T, Di Z, Islam E, Jiang H, Yang X. Rhizosphere characteristics of zinc hyperaccumulator Sedum alfredii involved in zinc accumulation. JOURNAL OF HAZARDOUS MATERIALS 2011; 185:818-23. [PMID: 20970251 DOI: 10.1016/j.jhazmat.2010.09.093] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/28/2010] [Revised: 09/05/2010] [Accepted: 09/25/2010] [Indexed: 05/25/2023]
Abstract
A hyperaccumulating ecotype (HE) and a non-hyperaccumulating ecotype (NHE) of Sedum alfredii were grown in a pot experiment to investigate the chemical characteristics of the rhizosphere. The results indicated that HE accumulated more Zn in the shoot than NHE after growing in both heavily and slightly polluted soil. The water soluble Zn and mobile Zn (extractable with 1M NH(4)NO(3)) fraction in both rhizosphere and bulk soils decreased considerably after growth of HE compared to NHE. However, the decreases in mobile fraction accounted for less than 8.5% of the total Zn uptake by HE indicating that HE was effective in mobilizing Zn from the non-mobile fractions. Zinc-induced root exudates reduced the soil pH (by 0.6-0.8 units) and increased dissolved organic carbon concentrations in the rhizosphere of HE compared to the bulk soil. The dissolved organic matter (DOM) from the rhizosphere of HE showed greater (1.7-2.5 times) extracting ability of Zn from various Zn minerals than those of NHE-DOM (P<0.05). Results from this study suggests that rhizosphere acidification and the exudation of high amounts of DOM with great metal extracting ability might be two important mechanisms by which HE S. alfredii is involved in activating metal in the rhizosphere.
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Affiliation(s)
- Tingqiang Li
- Ministry of Education Key Laboratory of Environmental Remediation and Ecosystem Health, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou 310029, China.
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187
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Hongbo S, Liye C, Gang X, Kun Y, Lihua Z, Junna S. Progress in Phytoremediating Heavy-Metal Contaminated Soils. SOIL BIOLOGY 2011. [DOI: 10.1007/978-3-642-21408-0_4] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
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188
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Marquès L, Oomen RJFJ. On the way to unravel zinc hyperaccumulation in plants: a mini review. Metallomics 2011; 3:1265-70. [DOI: 10.1039/c1mt00117e] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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189
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Zeng XW, Qiu RL, Ying RR, Tang YT, Tang L, Fang XH. The differentially-expressed proteome in Zn/Cd hyperaccumulator Arabis paniculata Franch. in response to Zn and Cd. CHEMOSPHERE 2011; 82:321-328. [PMID: 21074242 DOI: 10.1016/j.chemosphere.2010.10.030] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/19/2010] [Revised: 10/06/2010] [Accepted: 10/11/2010] [Indexed: 05/30/2023]
Abstract
The Zn/Cd hyperaccumulator Arabis paniculata is able to tolerate high level of Zn and Cd. To clarify the molecular basis of Zn and Cd tolerance, proteomic approaches were applied to identify proteins involved in Zn and Cd stress response in A. paniculata. Plants were exposed to both low and high Zn or Cd levels for 10 d. Proteins of leaves in each treatment were separated by 2-DE (two-dimensional electrophoresis). Nineteen differentially-expressed proteins upon Zn treatments and 18 proteins upon Cd treatments were observed. Seventeen out of 19 of Zn-responsive proteins and 16 out of 18 of Cd-responsive proteins were identified using MALDI-TOF/TOF-MS (matrix-assisted laser desorption/ionization time of flight mass spectrometry). The most of identified proteins were known to function in energy metabolism, xenobiotic/antioxidant defense, cellular metabolism, protein metabolism, suggesting the responses of A. paniculata to Zn and Cd share similar pathway to certain extend. However, the different metal defense was also revealed between Zn and Cd treatment in A. paniculata. These results indicated that A. paniculata against to Zn stress mainly by enhancement of energy metabolism including auxin biosynthesis and protein metabolism to maintain plant growth and correct misfolded proteins. In the case of Cd, plants adopted antioxidative/xenobiotic defense and cellular metabolism to keep cellular redox homeostasis and metal-transportation under Cd stress.
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Affiliation(s)
- Xiao-Wen Zeng
- School of Environmental Science and Engineering, Sun Yat-sen University, Guangzhou, Guangdong Province 510275, PR China; School of Public Health, Sun Yat-sen University, Guangzhou, Guangdong Province 510008, PR China
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190
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191
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Ectopic expression of foxtail millet zip-like gene, SiPf40, in transgenic rice plants causes a pleiotropic phenotype affecting tillering, vascular distribution and root development. SCIENCE CHINA-LIFE SCIENCES 2010; 53:1450-8. [DOI: 10.1007/s11427-010-4090-5] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/12/2010] [Accepted: 05/18/2010] [Indexed: 11/30/2022]
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192
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Lu L, Tian S, Zhang M, Zhang J, Yang X, Jiang H. The role of Ca pathway in Cd uptake and translocation by the hyperaccumulator Sedum alfredii. JOURNAL OF HAZARDOUS MATERIALS 2010; 183:22-8. [PMID: 20674155 DOI: 10.1016/j.jhazmat.2010.06.036] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/08/2010] [Revised: 06/07/2010] [Accepted: 06/10/2010] [Indexed: 05/16/2023]
Abstract
Effect of Ca on plant growth, Cd uptake and translocation in the hyperaccumulator Sedum alfredii was investigated, as to reveal the possible pathway of Cd entry into the plants system. High Ca increased plant growth under Cd stress after 7 d, and significantly affected the total Cd influx and translocation rate. Short-term kinetics of (109)Cd influx performed using radiotracers confirmed a significant inhibition of (109)Cd influx into the roots induced by high Ca. Under exposure of 5.0 mM Ca, K(m) of (109)Cd influx into roots was 2-fold higher in the hyperaccumulator, although the V(max) value remained at similar level, when compared with the treatments of 0.5 mM Ca. Calcium concentrations in xylem sap of the hyperaccumulator decreased with the increasing Cd levels and significant negative correlationship between the two elements was observed. However, increased xylem loading of Cd was observed in the hyperaccumulator in response to the increasing exogenous Ca level from 0.5 to 4.0 mM, but reverse effect was observed when higher Ca levels (8-32 mM) were presented in the solutions. These results suggest that Cd uptake and translocation in the hyperaccumulator S. alfredii plants is positively associated with Ca pathway.
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Affiliation(s)
- Lingli Lu
- MOE Key Laboratory of Environment Remediation and Ecosystem Health, College of Environmental and Resources Science, Zhejiang University, Huajiachi Campus, Hangzhou 310029, PR China.
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193
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Characterization of zinc transport by divalent metal transporters of the ZIP family from the model legume Medicago truncatula. Biometals 2010; 24:51-8. [DOI: 10.1007/s10534-010-9373-6] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2010] [Accepted: 08/31/2010] [Indexed: 11/26/2022]
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194
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Fay MF, Christenhusz MJ. BRASSICALES - AN ORDER OF PLANTS CHARACTERISED BY SHARED CHEMISTRY. ACTA ACUST UNITED AC 2010. [DOI: 10.1111/j.1467-8748.2010.01695.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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195
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Shi G, Liu C, Cai Q, Liu Q, Hou C. Cadmium accumulation and tolerance of two safflower cultivars in relation to photosynthesis and antioxidative enzymes. BULLETIN OF ENVIRONMENTAL CONTAMINATION AND TOXICOLOGY 2010; 85:256-263. [PMID: 20640847 DOI: 10.1007/s00128-010-0067-0] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/13/2010] [Accepted: 07/08/2010] [Indexed: 05/29/2023]
Abstract
To investigate the effects of cadmium (Cd) on photosynthetic and antioxidant activities of safflower (Carthamus tinctorius L.) plants, two cultivars (Yuming and New safflower No. 4) were used for long-term pot experiment, under 0, 25, 50 or 100 mg Cd kg(-1) (DW) soil conditions. The results showed that there is a large amount of Cd (148.6-277.2 mg kg(-1)) accumulated in the shoot of safflower, indicating this species might be a potential Cd accumulator. Exposure to 25-100 mg Cd kg(-1) soil decreased the net photosynthetic rate by 25.6%-48.9% for New safflower No. 4, and 16.7%-57.3% for Yuming, respectively. The inhibition of photosynthesis might result from the limitation of stomatal conductance, reduction in photosynthetic pigment, and destruction of photosynthetic apparatus caused by Cd stress. Cd caused an enhancement of malondialdehyde (MDA), an increase in activity of superoxide dismutase (SOD) and ascorbate peroxidase (APX), and a decrease in catalase (CAT) activity for both cultivars. It seems that SOD and APX accounted for the scavenging of oxidant stress in safflower cultivars. The physiological response of safflower plants to Cd stress was cultivar- and dose-dependent. New safflower No. 4 exhibited high photosynthetic performance at high Cd stress, which may be contributed by high intercellular CO(2) concentration, APX activity and Car/Chl ratio. In contrast, Yuming is more tolerant to Cd toxicity at low Cd level, in which an efficient antioxidant system is involved.
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Affiliation(s)
- Gangrong Shi
- The Anhui Provincial Key Laboratory of the Resource Plant Biology in College of Life Sciences, Huaibei Normal University, 235000, Huaibei, People's Republic of China
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196
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Watanabe A, Ito H, Chiba M, Ito A, Shimizu H, Fuji SI, Nakamura SI, Hattori H, Chino M, Satoh-Nagasawa N, Takahashi H, Sakurai K, Akagi H. Isolation of novel types of Arabidopsis mutants with altered reactions to cadmium: cadmium-gradient agar plates are an effective screen for the heavy metal-related mutants. PLANTA 2010; 232:825-836. [PMID: 20628760 DOI: 10.1007/s00425-010-1217-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/24/2010] [Accepted: 06/27/2010] [Indexed: 05/29/2023]
Abstract
We are interested in elucidating the molecular mechanisms underlying plant reactions to the toxic heavy metal cadmium (Cd). To this end, we devised a new screening strategy using agar plates with a gradient of Cd concentrations, termed Cd-gradient agar plates (CGAPs), to isolate Arabidopsis mutants that displayed altered reactions to the metal. Arabidopsis M(2) seeds, derived from ethyl methanesulfonate (EMS) treated seeds, were germinated on the CGAPs such that the primary root of each seedling elongated against increasing concentrations of Cd on the surface of the plate. Under these conditions, the lengths of the primary roots reliably demonstrated the degree of Cd tolerance of individual seedlings. The use of CGAPs also allowed close observation of the root reaction of each seedling to Cd without causing lethal damage. The screen identified three mutant lines, MRC-32, MRC-22 and MRC-26, which showed distinctly different characteristics. MRC-32 plants exhibited enhanced tolerance to Cd and contained Cd at higher concentrations than wild-type (WT) plants treated with the heavy metal. The whole root system of MRC-22 plants showed a Cd-phobic response. MRC-26 plants accumulated less Cd in their aboveground tissues than WT plants, suggesting that they were defective in transporting the heavy metal from roots to aboveground tissues. We also determined the likely chromosomal location of each mutation.
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Affiliation(s)
- Akio Watanabe
- Department of Biological Production, Faculty of Bioresource Sciences, Akita Prefectural University, Shimoshinjo-Nakano, Akita, Japan.
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197
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Song WY, Choi KS, Kim DY, Geisler M, Park J, Vincenzetti V, Schellenberg M, Kim SH, Lim YP, Noh EW, Lee Y, Martinoia E. Arabidopsis PCR2 is a zinc exporter involved in both zinc extrusion and long-distance zinc transport. THE PLANT CELL 2010; 22:2237-52. [PMID: 20647347 PMCID: PMC2929092 DOI: 10.1105/tpc.109.070185] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/21/2009] [Revised: 06/13/2010] [Accepted: 07/01/2010] [Indexed: 05/19/2023]
Abstract
Plants strictly regulate the uptake and distribution of Zn, which is essential for plant growth and development. Here, we show that Arabidopsis thaliana PCR2 is essential for Zn redistribution and Zn detoxification. The pcr2 loss-of-function mutant was compromised in growth, both in Zn-excessive and -deficient conditions. The roots of pcr2 accumulated more Zn than did control plants, whereas the roots of plants overexpressing PCR2 contained less Zn, indicating that PCR2 removes Zn from the roots. Consistent with a role for PCR2 as a Zn-efflux transporter, PCR2 reduced the intracellular concentration of Zn when expressed in yeast cells. PCR2 is located mainly in epidermal cells and in the xylem of young roots, while it is expressed in epidermal cells in fully developed roots. Zn accumulated in the epidermis of the roots of pcr2 grown under Zn-limiting conditions, whereas it was found in the stele of wild-type roots. The transport pathway mediated by PCR2 does not seem to overlap with that mediated by the described Zn translocators (HMA2 and HMA4) since the growth of pcr2 hma4 double and pcr2 hma2 hma4 triple loss-of-function mutants was more severely inhibited than the individual single knockout mutants, both under conditions of excess or deficient Zn. We propose that PCR2 functions as a Zn transporter essential for maintaining an optimal Zn level in Arabidopsis.
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Affiliation(s)
- Won-Yong Song
- Institut für Pflanzenbiologie, Universität Zürich, 8008 Zurich, Switzerland.
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198
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Wang M, Xu Q, Yu J, Yuan M. The putative Arabidopsis zinc transporter ZTP29 is involved in the response to salt stress. PLANT MOLECULAR BIOLOGY 2010; 73:467-79. [PMID: 20358261 DOI: 10.1007/s11103-010-9633-4] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/19/2009] [Accepted: 03/21/2010] [Indexed: 05/20/2023]
Abstract
Salt stress leads to a stress response, called the unfolded protein response (UPR), in the endoplasmic reticulum (ER). UPR is also induced in a wide range of organisms by zinc deficiency. However, it is not clear whether regulation of zinc levels is involved in the initiation of the UPR in plant response to salt stress. In this study, a putative zinc transporter, ZTP29, was identified in Arabidopsis thaliana. ZTP29 localizes to the ER membrane and is expressed primarily in hypocotyl and cotyledon tissues, but its expression can be induced in root tissue by salt stress. T-DNA insertion into the ZTP29 gene led to NaCl hypersensitivity in seed germination and seedling growth, leaf etiolation, and widening of cells in the root elongation zone. In addition, in ztp29 mutant plants, salt stress-induced upregulation of the UPR pathway genes BiP2 and bZIP60 was inhibited. Furthermore, under conditions of salt stress, upregulation of BiP2 and bZIP60 was inhibited by treatment with high concentrations of zinc in both control and ztp29 plants. However, zinc chelation restored salt stress-induced BiP2 and bZIP60 upregulation in ztp29 mutant plants. These experimental results suggest that ZTP29 is involved in the response to salt stress, perhaps through regulation of zinc levels required to induce the UPR pathway.
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Affiliation(s)
- Miaoying Wang
- State Key Laboratory of Plant Physiology and Biochemistry, Department of Plant Sciences, College of Biological Sciences, China Agricultural University, 100193 Beijing, China
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199
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Ma W, Xu W, Xu H, Chen Y, He Z, Ma M. Nitric oxide modulates cadmium influx during cadmium-induced programmed cell death in tobacco BY-2 cells. PLANTA 2010; 232:325-35. [PMID: 20449606 DOI: 10.1007/s00425-010-1177-y] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/18/2010] [Accepted: 04/13/2010] [Indexed: 05/20/2023]
Abstract
Nitric oxide (NO) is a bioactive gas and functions as a signaling molecule in plants exposed to diverse biotic and abiotic stresses including cadmium (Cd(2+)). Cd(2+) is a non-essential and toxic heavy metal, which has been reported to induce programmed cell death (PCD) in plants. Here, we investigated the role of NO in Cd(2+)-induced PCD in tobacco BY-2 cells (Nicotiana tabacum L. cv. Bright Yellow 2). In this work, BY-2 cells exposed to 150 microM CdCl(2) underwent PCD with TUNEL-positive nuclei, significant chromatin condensation and the increasing expression of a PCD-related gene Hsr203J. Accompanied with the occurring of PCD, the production of NO increased significantly. The supplement of NO by sodium nitroprusside (SNP) had accelerated the PCD, whereas the NO synthase inhibitor Nomega-nitro-L-arginine methyl ester hydrochloride (L-NAME) and NO-specific scavenger 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (cPTIO) alleviated this toxicity. To investigate the mechanism by which NO exerted its function, Cd(2+) concentration was measured subsequently. SNP led more Cd(2+) content than Cd(2+) treatment alone. By contrast, the prevention of NO by L-NAME decreased Cd(2+) accumulation. Using the scanning ion-selective electrode technique, we analyzed the pattern and rate of Cd(2+) fluxes. This analysis revealed the promotion of Cd(2+) influxes into cells by application of SNP, while L-NAME and cPTIO reduced the rate of Cd(2+) uptake or even resulted in net Cd(2+) efflux. Based on these founding, we concluded that NO played a positive role in CdCl(2)-induced PCD by modulating Cd(2+) uptake and thus promoting Cd(2+) accumulation in BY-2 cells.
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Affiliation(s)
- Wenwen Ma
- Key Laboratory of Photosynthesis and Environmental Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing, People's Republic of China
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200
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Hong-Bo S, Li-Ye C, Cheng-Jiang R, Hua L, Dong-Gang G, Wei-Xiang L. Understanding molecular mechanisms for improving phytoremediation of heavy metal-contaminated soils. Crit Rev Biotechnol 2010; 30:23-30. [PMID: 19821782 DOI: 10.3109/07388550903208057] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Heavy metal pollution of soil is a significant environmental problem with a negative potential impact on human health and agriculture. Rhizosphere, as an important interface of soil and plants, plays a significant role in phytoremediation of contaminated soil by heavy metals, in which, microbial populations are known to affect heavy metal mobility and availability to the plant through release of chelating agents, acidification, phosphate solubilization and redox changes, and therefore, have potential to enhance phytoremediation processes. Phytoremediation strategies with appropriate heavy metal-adapted rhizobacteria or mycorrhizas have received more and more attention. In addition, some plants possess a range of potential mechanisms that may be involved in the detoxification of heavy metals, and they manage to survive under metal stresses. High tolerance to heavy metal toxicity could rely either on reduced uptake or increased plant internal sequestration, which is manifested by an interaction between a genotype and its environment.A coordinated network of molecular processes provides plants with multiple metal-detoxifying mechanisms and repair capabilities. The growing application of molecular genetic technologies has led to an increased understanding of mechanisms of heavy metal tolerance/accumulation in plants and, subsequently, many transgenic plants with increased heavy metal resistance, as well as increased uptake of heavy metals, have been developed for the purpose of phytoremediation. This article reviews advantages, possible mechanisms, current status and future direction of phytoremediation for heavy-metal-contaminated soils.
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Affiliation(s)
- Shao Hong-Bo
- State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, Institute of Soil and Water Conservation, Chinese Academy of Sciences, Northwest A&F University, Yangling, China.
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