1
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Santin A, Russo MT, de Los Ríos LM, Chiurazzi M, d'Alcalà MR, Lacombe B, Ferrante MI, Rogato A. The tonoplast localized protein PtNPF1 participates in the regulation of nitrogen response in diatoms. THE NEW PHYTOLOGIST 2024; 241:1592-1604. [PMID: 38084038 DOI: 10.1111/nph.19461] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/26/2023] [Accepted: 11/21/2023] [Indexed: 01/26/2024]
Abstract
Diatoms are a highly successful group of phytoplankton, well adapted also to oligotrophic environments and capable of handling nutrient fluctuations in the ocean, particularly nitrate. The presence of a large vacuole is an important trait contributing to their adaptive features. It confers diatoms the ability to accumulate and store nutrients, such as nitrate, when they are abundant outside and then to reallocate them into the cytosol to meet deficiencies, in a process called luxury uptake. The molecular mechanisms that regulate these nitrate fluxes are still not known in diatoms. In this work, we provide new insights into the function of Phaeodactylum tricornutum NPF1, a putative low-affinity nitrate transporter. To accomplish this, we generated overexpressing strains and CRISPR/Cas9 loss-of-function mutants. Microscopy observations confirmed predictions that PtNPF1 is localized on the vacuole membrane. Furthermore, functional characterizations performed on knock-out mutants revealed a transient growth delay phenotype linked to altered nitrate uptake. Together, these results allowed us to hypothesize that PtNPF1 is presumably involved in modulating intracellular nitrogen fluxes, managing intracellular nutrient availability. This ability might allow diatoms to fine-tune the assimilation, storage and reallocation of nitrate, conferring them a strong advantage in oligotrophic environments.
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Affiliation(s)
- Anna Santin
- Stazione Zoologica Anton Dohrn, Villa Comunale, Naples, 80121, Italy
| | | | - Laura Morales de Los Ríos
- Institute for Plant Science of Montpellier (IPSiM), University of Montpellier, CNRS, INRAE, Montpellier SupAgro, Place Pierre Viala 2, Montpellier, 34060, France
| | - Maurizio Chiurazzi
- Institute of Biosciences and BioResources, CNR, Via P. Castellino 111, Naples, 80131, Italy
| | | | - Benoît Lacombe
- Institute for Plant Science of Montpellier (IPSiM), University of Montpellier, CNRS, INRAE, Montpellier SupAgro, Place Pierre Viala 2, Montpellier, 34060, France
| | - Maria Immacolata Ferrante
- Stazione Zoologica Anton Dohrn, Villa Comunale, Naples, 80121, Italy
- National Institute of Oceanography and Applied Geophysics, Trieste, 34010, Italy
| | - Alessandra Rogato
- Stazione Zoologica Anton Dohrn, Villa Comunale, Naples, 80121, Italy
- Institute of Biosciences and BioResources, CNR, Via P. Castellino 111, Naples, 80131, Italy
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2
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Stanchev LD, Møller-Hansen I, Lojko P, Rocha C, Borodina I. Screening of Saccharomyces cerevisiae metabolite transporters by 13C isotope substrate labeling. Front Microbiol 2023; 14:1286597. [PMID: 38116525 PMCID: PMC10729909 DOI: 10.3389/fmicb.2023.1286597] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2023] [Accepted: 11/10/2023] [Indexed: 12/21/2023] Open
Abstract
The transportome of Saccharomyces cerevisiae comprises approximately 340 membrane-bound proteins, of which very few are well-characterized. Elucidating transporter proteins' function is essential not only for understanding central cellular processes in metabolite exchange with the external milieu but also for optimizing the production of value-added compounds in microbial cell factories. Here, we describe the application of 13C-labeled stable isotopes and detection by targeted LC-MS/MS as a screening tool for identifying Saccharomyces cerevisiae metabolite transporters. We compare the transport assay's sensitivity, reproducibility, and accuracy in yeast transporter mutant cell lines and Xenopus oocytes. As proof of principle, we analyzed the transport profiles of five yeast amino acid transporters. We first cultured yeast transporter deletion or overexpression mutants on uniformly labeled 13C-glucose and then screened their ability to facilitate the uptake or export of an unlabeled pool of amino acids. Individual transporters were further studied by heterologous expression in Xenopus oocytes, followed by an uptake assay with 13C labeled yeast extract. Uptake assays in Xenopus oocytes showed higher reproducibility and accuracy. Although having lower accuracy, the results from S. cerevisiae indicated the system's potential for initial high-throughput screening for native metabolite transporters. We partially confirmed previously reported substrates for all five amino acid transporters. In addition, we propose broader substrate specificity for two of the transporter proteins. The method presented here demonstrates the application of a comprehensive screening platform for the knowledge expansion of the transporter-substrate relationship for native metabolites in S. cerevisiae.
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Affiliation(s)
| | | | | | | | - Irina Borodina
- The Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark, Kongens Lyngby, Denmark
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3
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Strauss J, Deng L, Gao S, Toseland A, Bachy C, Zhang C, Kirkham A, Hopes A, Utting R, Joest EF, Tagliabue A, Löw C, Worden AZ, Nagel G, Mock T. Plastid-localized xanthorhodopsin increases diatom biomass and ecosystem productivity in iron-limited surface oceans. Nat Microbiol 2023; 8:2050-2066. [PMID: 37845316 PMCID: PMC10627834 DOI: 10.1038/s41564-023-01498-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2023] [Accepted: 09/12/2023] [Indexed: 10/18/2023]
Abstract
Microbial rhodopsins are photoreceptor proteins that convert light into biological signals or energy. Proteins of the xanthorhodopsin family are common in eukaryotic photosynthetic plankton including diatoms. However, their biological role in these organisms remains elusive. Here we report on a xanthorhodopsin variant (FcR1) isolated from the polar diatom Fragilariopsis cylindrus. Applying a combination of biophysical, biochemical and reverse genetics approaches, we demonstrate that FcR1 is a plastid-localized proton pump which binds the chromophore retinal and is activated by green light. Enhanced growth of a Thalassiora pseudonana gain-of-function mutant expressing FcR1 under iron limitation shows that the xanthorhodopsin proton pump supports growth when chlorophyll-based photosynthesis is iron-limited. The abundance of xanthorhodopsin transcripts in natural diatom communities of the surface oceans is anticorrelated with the availability of dissolved iron. Thus, we propose that these proton pumps convey a fitness advantage in regions where phytoplankton growth is limited by the availability of dissolved iron.
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Affiliation(s)
- Jan Strauss
- School of Environmental Sciences, University of East Anglia, Norwich Research Park, Norwich, UK.
- Ocean EcoSystems Biology Unit, RD3, GEOMAR Helmholtz Centre for Ocean Research Kiel, Kiel, Germany.
- European Molecular Biology Laboratory (EMBL), Hamburg Unit c/o Deutsches Elektronen Synchrotron (DESY), Hamburg, Germany.
- Centre for Structural Systems Biology (CSSB), Hamburg, Germany.
- German Maritime Centre, Hamburg, Germany.
| | - Longji Deng
- School of Environmental Sciences, University of East Anglia, Norwich Research Park, Norwich, UK
| | - Shiqiang Gao
- Department of Neurophysiology, Institute of Physiology, University of Würzburg, Wuerzburg, Germany
| | - Andrew Toseland
- School of Environmental Sciences, University of East Anglia, Norwich Research Park, Norwich, UK
| | - Charles Bachy
- Ocean EcoSystems Biology Unit, RD3, GEOMAR Helmholtz Centre for Ocean Research Kiel, Kiel, Germany
- Sorbonne Université, CNRS, FR2424, Station biologique de Roscoff, Roscoff, France
| | - Chong Zhang
- Department of Neurophysiology, Institute of Physiology, University of Würzburg, Wuerzburg, Germany
| | - Amy Kirkham
- School of Environmental Sciences, University of East Anglia, Norwich Research Park, Norwich, UK
- School of Biological Sciences, University of East Anglia, Norwich Research Park, Norwich, UK
| | - Amanda Hopes
- School of Environmental Sciences, University of East Anglia, Norwich Research Park, Norwich, UK
| | - Robert Utting
- School of Environmental Sciences, University of East Anglia, Norwich Research Park, Norwich, UK
| | - Eike F Joest
- Department of Biology, Biocenter, University of Würzburg, Wuerzburg, Germany
| | | | - Christian Löw
- European Molecular Biology Laboratory (EMBL), Hamburg Unit c/o Deutsches Elektronen Synchrotron (DESY), Hamburg, Germany
- Centre for Structural Systems Biology (CSSB), Hamburg, Germany
| | - Alexandra Z Worden
- Ocean EcoSystems Biology Unit, RD3, GEOMAR Helmholtz Centre for Ocean Research Kiel, Kiel, Germany
- Max Planck Institute for Evolutionary Biology, Plön, Germany
- Marine Biological Laboratory, Woods Hole, MA, USA
| | - Georg Nagel
- Department of Neurophysiology, Institute of Physiology, University of Würzburg, Wuerzburg, Germany
| | - Thomas Mock
- School of Environmental Sciences, University of East Anglia, Norwich Research Park, Norwich, UK.
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4
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Wang W, An X, Yan K, Li Q. Construction and Application of Orthogonal T7 Expression System in Eukaryote: An Overview. Adv Biol (Weinh) 2023; 7:e2200218. [PMID: 36464626 DOI: 10.1002/adbi.202200218] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2022] [Revised: 10/17/2022] [Indexed: 12/12/2022]
Abstract
The T7 system is an orthogonal transcription-system, which is characterized by simplicity, higher efficiency, and higher processivity, and it is used for protein or mRNA synthesis in various biological-systems. In comparison with prokaryotes, the construction of the T7 expression system is still on-going in eukaryotes, but it shows greatly applicable prospects. In the present paper, development of T7 expression system construction in eukaryotes is reviewed, including its construction in animal (mammalian cells, trypanosomatid protozoa, Xenopus oocytes, zebrafish), plant, and microorganism and its application in vaccine production and gene therapy. In addition, the innate challenges of T7 expression system construction in eukaryote and its potential application in vaccine production and gene therapy are discussed.
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Affiliation(s)
- Wenya Wang
- College of Life Science and Technology, Beijing University of Chemical Technology, Beijing, 100029, P. R. China
| | - Xiaoyan An
- College of Life Science and Technology, Beijing University of Chemical Technology, Beijing, 100029, P. R. China
| | - Kun Yan
- College of Life Science and Technology, Beijing University of Chemical Technology, Beijing, 100029, P. R. China
| | - Qiang Li
- Key Laboratory for Industrial Biocatalysis, Ministry of Education, Department of Chemical Engineering, Tsinghua University, Beijing, 100084, P. R. China
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5
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Brunner N, Stein L, Amasheh S. Cellular Distribution Pattern of tjp1 (ZO-1) in Xenopus laevis Oocytes Heterologously Expressing Claudins. J Membr Biol 2023; 256:51-61. [PMID: 35737002 PMCID: PMC9884258 DOI: 10.1007/s00232-022-00251-z] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2022] [Accepted: 06/02/2022] [Indexed: 02/07/2023]
Abstract
Epithelial barriers constitute a fundamental requirement in every organism, as they allow the separation of different environments and set boundaries against noxious and other adverse effectors. In many inflammatory and degenerative diseases, epithelial barrier function is impaired because of a disturbance of the paracellular seal. Recently, the Xenopus laevis oocyte has been established as a heterologous expression model for the analysis of transmembrane tight junction protein interactions and is currently considered to be a suitable screening model for barrier effectors. A prerequisite for this application is a physiological anchoring of claudins to the cytoskeleton via the major scaffolding protein tjp1 (tight junction protein 1, ZO-1). We have analyzed the oocyte model with regard to the interaction of heterologously expressed claudins and tjp1. Our experiments have revealed endogenous tjp1 expression in protein and mRNA analyses of unfertilized Xenopus laevis oocytes expressing human claudin 1 (CLDN1) to claudin 5 (CLDN5). The amphibian cell model can therefore be used for the analysis of claudin interactions.
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Affiliation(s)
- Nora Brunner
- Institute of Veterinary Physiology, Freie Universität Berlin, Oertzenweg 19b, 14163 Berlin, Germany
| | - Laura Stein
- Institute of Veterinary Physiology, Freie Universität Berlin, Oertzenweg 19b, 14163 Berlin, Germany
| | - Salah Amasheh
- Institute of Veterinary Physiology, Freie Universität Berlin, Oertzenweg 19b, 14163 Berlin, Germany
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6
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Ivorra I, Alberola-Die A, Cobo R, González-Ros JM, Morales A. Xenopus Oocytes as a Powerful Cellular Model to Study Foreign Fully-Processed Membrane Proteins. MEMBRANES 2022; 12:986. [PMID: 36295745 PMCID: PMC9610954 DOI: 10.3390/membranes12100986] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/16/2022] [Revised: 10/05/2022] [Accepted: 10/08/2022] [Indexed: 06/16/2023]
Abstract
The use of Xenopus oocytes in electrophysiological and biophysical research constitutes a long and successful story, providing major advances to the knowledge of the function and modulation of membrane proteins, mostly receptors, ion channels, and transporters. Earlier reports showed that these cells are capable of correctly expressing heterologous proteins after injecting the corresponding mRNA or cDNA. More recently, the Xenopus oocyte has become an outstanding host-cell model to carry out detailed studies on the function of fully-processed foreign membrane proteins after their microtransplantation to the oocyte. This review focused on the latter overall process of transplanting foreign membrane proteins to the oocyte after injecting plasma membranes or purified and reconstituted proteins. This experimental approach allows for the study of both the function of mature proteins, with their native stoichiometry and post-translational modifications, and their putative modulation by surrounding lipids, mostly when the protein is purified and reconstituted in lipid matrices of defined composition. Remarkably, this methodology enables functional microtransplantation to the oocyte of membrane receptors, ion channels, and transporters from different sources including human post-mortem tissue banks. Despite the large progress achieved over the last decades on the structure, function, and modulation of neuroreceptors and ion channels in healthy and pathological tissues, many unanswered questions remain and, most likely, Xenopus oocytes will continue to help provide valuable responses.
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Affiliation(s)
- Isabel Ivorra
- Departamento de Fisiología, Genética y Microbiología, Universidad de Alicante, Apdo 99, E-03080 Alicante, Spain
| | - Armando Alberola-Die
- Departamento de Fisiología, Genética y Microbiología, Universidad de Alicante, Apdo 99, E-03080 Alicante, Spain
| | - Raúl Cobo
- Departamento de Fisiología, Genética y Microbiología, Universidad de Alicante, Apdo 99, E-03080 Alicante, Spain
| | - José Manuel González-Ros
- Instituto de Investigación, Desarrollo e Innovación en Biotecnología Sanitaria de Elche (IDiBE), Universidad Miguel Hernández, E-03202 Elche, Spain
| | - Andrés Morales
- Departamento de Fisiología, Genética y Microbiología, Universidad de Alicante, Apdo 99, E-03080 Alicante, Spain
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7
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Dhatterwal P, Mehrotra S, Miller AJ, Aduri R, Mehrotra R. Effect of ACGT motif in spatiotemporal regulation of AtAVT6D, which improves tolerance to osmotic stress and nitrogen-starvation. PLANT MOLECULAR BIOLOGY 2022; 109:67-82. [PMID: 35377091 DOI: 10.1007/s11103-022-01256-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/27/2021] [Accepted: 03/01/2022] [Indexed: 06/14/2023]
Abstract
Plasma membrane-localized AtAVT6D importing aspartic acid can be targeted to develop plants with enhanced osmotic and nitrogen-starvation tolerance. AtAVT6D promoter can be exploited as a stress-inducible promoter for genetic improvements to raise stress-resilient crops. The AtAVT6 family of amino acid transporters in Arabidopsis thaliana has been predicted to export amino acids like aspartate and glutamate. However, the functional characterization of these amino acid transporters in plants remains unexplored. The present study investigates the expression patterns of AtAVT6 genes in different tissues and under various abiotic stress conditions using quantitative Real-time PCR. The expression analysis demonstrated that the member AtAVT6D was significantly induced in response to phytohormone ABA and stresses like osmotic and drought. The tissue-specific expression analysis showed that AtAVT6D was strongly expressed in the siliques. Taking together these results, we can speculate that AtAVT6D might play a vital role in silique development and abiotic stress tolerance. Further, subcellular localization study showed AtAVT6D was localized to the plasma membrane. The heterologous expression of AtAVT6D in yeast cells conferred significant tolerance to nitrogen-deficient and osmotic stress conditions. The Xenopus oocyte studies revealed that AtAVT6D is involved in the uptake of Aspartic acid. While overexpression of AtAVT6D resulted in smaller siliques in Arabidopsis thaliana. Additionally, transient expression studies were performed with the full-length AtAVT6D promoter and its deletion constructs to study the effect of ACGT-N24-ACGT motifs on the reporter gene expression in response to abiotic stresses and ABA treatment. The fluorometric GUS analyses revealed that the promoter deletion construct-2 (Pro.C2) possessing a single copy of ACGT-N24-ACGT motif directed the strongest GUS expression under all the abiotic conditions tested. These results suggest that Pro.C2 can be used as a stress-inducible promoter to drive a significant transgene expression.
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Affiliation(s)
- Pinky Dhatterwal
- Department of Biological Sciences, Birla Institute of Technology and Science Pilani, K.K. Birla Goa Campus, Goa, India
| | - Sandhya Mehrotra
- Department of Biological Sciences, Birla Institute of Technology and Science Pilani, K.K. Birla Goa Campus, Goa, India
| | - Anthony J Miller
- Department of Metabolic Biology, John Innes Centre, Norwich Research Park, Norwich, UK
| | - Raviprasad Aduri
- Department of Biological Sciences, Birla Institute of Technology and Science Pilani, K.K. Birla Goa Campus, Goa, India
| | - Rajesh Mehrotra
- Department of Biological Sciences, Birla Institute of Technology and Science Pilani, K.K. Birla Goa Campus, Goa, India.
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8
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Havukainen S, Pujol-Giménez J, Valkonen M, Westerholm-Parvinen A, Hediger MA, Landowski CP. Electrophysiological characterization of a diverse group of sugar transporters from Trichoderma reesei. Sci Rep 2021; 11:14678. [PMID: 34282161 PMCID: PMC8290022 DOI: 10.1038/s41598-021-93552-7] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2021] [Accepted: 06/21/2021] [Indexed: 02/06/2023] Open
Abstract
Trichoderma reesei is an ascomycete fungus known for its capability to secrete high amounts of extracellular cellulose- and hemicellulose-degrading enzymes. These enzymes are utilized in the production of second-generation biofuels and T. reesei is a well-established host for their production. Although this species has gained considerable interest in the scientific literature, the sugar transportome of T. reesei remains poorly characterized. Better understanding of the proteins involved in the transport of different sugars could be utilized for engineering better enzyme production strains. In this study we aimed to shed light on this matter by characterizing multiple T. reesei transporters capable of transporting various types of sugars. We used phylogenetics to select transporters for expression in Xenopus laevis oocytes to screen for transport activities. Of the 18 tested transporters, 8 were found to be functional in oocytes. 10 transporters in total were investigated in oocytes and in yeast, and for 3 of them no transport function had been described in literature. This comprehensive analysis provides a large body of new knowledge about T. reesei sugar transporters, and further establishes X. laevis oocytes as a valuable tool for studying fungal sugar transporters.
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Affiliation(s)
- Sami Havukainen
- Protein Production Team, VTT Technical Research Center of Finland Ltd, Tietotie 2, 02150, Espoo, Finland
| | - Jonai Pujol-Giménez
- Membrane Transport Discovery Lab, Department of Biomedical Research, Inselspital, University of Bern, 3010, Bern, Switzerland
| | - Mari Valkonen
- Protein Production Team, VTT Technical Research Center of Finland Ltd, Tietotie 2, 02150, Espoo, Finland
| | - Ann Westerholm-Parvinen
- Protein Production Team, VTT Technical Research Center of Finland Ltd, Tietotie 2, 02150, Espoo, Finland
| | - Matthias A Hediger
- Membrane Transport Discovery Lab, Department of Biomedical Research, Inselspital, University of Bern, 3010, Bern, Switzerland
| | - Christopher P Landowski
- Protein Production Team, VTT Technical Research Center of Finland Ltd, Tietotie 2, 02150, Espoo, Finland.
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9
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The Xenopus Oocyte as an Expression System for Functional Analyses of Fish Aquaporins. Methods Mol Biol 2021. [PMID: 33606219 DOI: 10.1007/978-1-0716-0970-5_2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/29/2023]
Abstract
Aquaporins are membrane proteins present in all organisms that selectively transport water and small, uncharged solutes across biological membranes along an osmotic gradient. Recent gene editing technologies in zebrafish (Danio rerio) have started to uncover the physiological functions of the aquaporins in teleosts, but these approaches require methods to establish the effects of specific mutations on channel function. The oocytes of the South African frog Xenopus laevis are widely used for the expression of bacterial, plant, and animal aquaporins, and this heterologous system has contributed to numerous discoveries in aquaporin biology. This chapter focuses on techniques used for oocyte preparation and aquaporin expression and gives an overview of specific methods to determine water and solute permeability of the channels and their intracellular trafficking in oocytes.
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10
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Nambiar DM, Kumari J, Arya GC, Singh AK, Bisht NC. A cell suspension based uptake method to study high affinity glucosinolate transporters. PLANT METHODS 2020; 16:75. [PMID: 32489397 PMCID: PMC7247208 DOI: 10.1186/s13007-020-00618-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/24/2019] [Accepted: 05/15/2020] [Indexed: 06/11/2023]
Abstract
BACKGROUND Glucosinolates are an important class of secondary metabolites characteristic to the order Brassicales. They are known to play a major role in plant defense and from the human perspective, can be anticarcinogenic or antinutritive. GTRs are plasma-membrane localized high affinity glucosinolate transporters, which are important components of the source (leaf) to sink (seed) translocation of intact glucosinolates in members of Brassicaceae family. GTRs are identified as major candidates for Brassica crop improvement, thus dictating a need for their functional characterization. However, currently there are limitations in availability of heterologous assay systems for functional characterization of plant secondary metabolite transporters. To date, the animal-based Xenopus oocyte system is the best established heterologous system for functional characterization of these transporters. Inherent biochemical and physiological attributes unique to the plant membranes necessitate the need for developing plant-based transporters assay systems as well. METHODS In this study, Agrobacterium mediated transformation was used to develop GTR expressing cotton cell lines (CCL-1) for functional characterization of the Arabidopsis high affinity glucosinolate transporters, AtGTR1 and AtGTR2. Following sub-cellular localization of AtGTRs, we standardized the glucosinolate uptake assays using cell suspension cultures of AtGTR expressing CCL-1 its requirement of pH, salt, and time based glucosinolate uptake. Using the GTR expressing CCL-1, we subsequently performed kinetic analysis of AtGTR1 and AtGTR2 for different glucosinolate substrates, sinigrin, gluconapin and sinalbin. RESULTS Several clones expressing each of AtGTR1 and AtGTR2 were obtained showing high level of GTR expression and were maintained through regular sub-culturing. Both AtGTR1 and AtGTR2 are predominantly plasma-localized proteins when overexpressed in CCL-1 cells. Uptake assays were standardized, suggesting that glucosinolate uptake of GTR expressing CCL-1 is robust within the physiological pH range 5-6, and at lower concentration of nitrate salts. GTR expressing CCL-1 cells show increasing glucosinolate accumulation in time course experiment. Kinetic studies over a wide glucosinolate concentrations (10-800 µM) revealed that our novel assay system displayed robust GTR-mediated uptake of different glucosinolates and unambiguously helps elucidate the saturable kinetics of GTRs. Our system confirms the high affinity of AtGTRs for both aliphatic and aromatic glucosinolates. CONCLUSION The transporter assay system described in this study holds potential for studying sub-functionalization amongst GTR homologs present across Brassicaceae family. The fast growing CCL-1 cells, confer the benefits of an in vitro system for quick assays and is plant based thus enabling optimal expression without sequence modifications. The efficient functioning of the GTR transporters in the heterologous CCL-1 opens the possibility of using this plant cell suspension system for functional characterization of other metabolite transporters.
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Affiliation(s)
- Deepti M. Nambiar
- National Institute of Plant Genome Research, Aruna Asaf Ali Marg, New Delhi, 110067 India
| | - Juhi Kumari
- National Institute of Plant Genome Research, Aruna Asaf Ali Marg, New Delhi, 110067 India
| | - Gulab C. Arya
- National Institute of Plant Genome Research, Aruna Asaf Ali Marg, New Delhi, 110067 India
| | - Amarjeet K. Singh
- Department of Genetics, CGMCP, University of Delhi South Campus, New Delhi, 110021 India
| | - Naveen C. Bisht
- National Institute of Plant Genome Research, Aruna Asaf Ali Marg, New Delhi, 110067 India
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11
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Li H. K+ Release Assay and K+ Measurement in Oocyte Assay. Bio Protoc 2020; 10:e3802. [DOI: 10.21769/bioprotoc.3802] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2020] [Revised: 08/31/2020] [Accepted: 09/26/2020] [Indexed: 11/02/2022] Open
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12
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Demurtas OC, de Brito Francisco R, Martinoia E, Giuliano G. Transportomics for the Characterization of Plant Apocarotenoid Transmembrane Transporters. Methods Mol Biol 2020; 2083:89-99. [PMID: 31745915 DOI: 10.1007/978-1-4939-9952-1_7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/09/2022]
Abstract
Apocarotenoids are carotenoid derivatives produced by the nonenzymatic or enzymatic cleavage of carotenoids, followed by different enzymatic modifications. In plants, apocarotenoids play different roles, such as attraction of pollinators and seeds dispersal, defense against pathogens and herbivores, protection against photo-oxidative stresses, stimulation and inhibition of plant growth and regulation of biological processes in the case of phytohormones abscisic acid and strigolactones. While carotenoids are in general plastid-localized metabolites, apocarotenoids can reach different final destinations inside or outside the cell. The mechanisms of apocarotenoid transport through biological membranes have been poorly studied. This chapter describes a method to characterize transmembrane transporters involved in the transport of polar and amphipathic apocarotenoids. This protocol was successfully used to in vitro characterize the transport activity of ATP-binding cassette (ABC) and multidrug and toxic extrusion (MATE) in microsomes isolated from Saccharomyces cerevisiae expressing these plant transporters.
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Affiliation(s)
- Olivia Costantina Demurtas
- ENEA, Italian National Agency for New Technologies, Energy and Sustainable Economic Development, C.R. Casaccia, Rome, Italy
| | | | - Enrico Martinoia
- Department of Plant and Microbial Biology, University of Zurich, Zurich, Switzerland
| | - Giovanni Giuliano
- ENEA, Italian National Agency for New Technologies, Energy and Sustainable Economic Development, C.R. Casaccia, Rome, Italy.
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13
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Pike S, Matthes MS, McSteen P, Gassmann W. Using Xenopus laevis Oocytes to Functionally Characterize Plant Transporters. ACTA ACUST UNITED AC 2019; 4:e20087. [PMID: 30707001 DOI: 10.1002/cppb.20087] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Functionally characterizing plant membrane transport proteins is challenging. Typically, heterologous systems are used to study them. Immature eggs (oocytes) of the South African clawed frog Xenopus laevis are considered an ideal expression system for such studies. These large oocytes have a low number of endogenous transport systems in their plasma membranes and highly express foreign mRNA; the oocyte plasma membrane is the default destination of integral membrane proteins that lack recognized organellar sorting signals. These features facilitate almost background-free characterization of putative plant membrane transporters. Here we describe how to isolate Xenopus laevis oocytes, prepare capped sense RNA (cRNA) of the maize boron importer TASSEL-LESS1 (TLS1) as an example, microinject the cRNA into the isolated oocytes, and functionally assess the boron import capabilities of TLS1 in an oocyte swelling assay. These protocols can be easily adapted to study other plant and non-plant transporters with putative import function. © 2019 by John Wiley & Sons, Inc.
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Affiliation(s)
- Sharon Pike
- Division of Plant Sciences, Bond Life Sciences Center, and Interdisciplinary Plant Group, University of Missouri, Columbia, Missouri
| | - Michaela S Matthes
- Division of Biological Sciences, Bond Life Sciences Center, Interdisciplinary Plant Group, and Missouri Maize Center, University of Missouri, Columbia, Missouri
| | - Paula McSteen
- Division of Biological Sciences, Bond Life Sciences Center, Interdisciplinary Plant Group, and Missouri Maize Center, University of Missouri, Columbia, Missouri
| | - Walter Gassmann
- Division of Plant Sciences, Bond Life Sciences Center, and Interdisciplinary Plant Group, University of Missouri, Columbia, Missouri
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Jiang X, Xie Y, Ren Z, Ganeteg U, Lin F, Zhao C, Xu H. Design of a New Glutamine-Fipronil Conjugate with α-Amino Acid Function and Its Uptake by A. thaliana Lysine Histidine Transporter 1 ( AtLHT1). JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2018; 66:7597-7605. [PMID: 29944366 DOI: 10.1021/acs.jafc.8b02287] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
Creating novel pesticides with phloem mobility is essential for controlling insects in vascular tissue and root, and conjugating existing pesticides with amino acid is an effective approach. In order to obtain a highly phloem-mobile candidate for efficient pesticides, an electro-neutral l-glutamine-fipronil conjugate (l-GlnF) retaining α-amino acid function was designed and synthesized to fit the substrate specificity of an amino acid transporter. Cotyledon uptake and phloem loading tests with Ricinus communis have verified that l-GlnF was phloem mobile, and its phloem mobility was higher than that of its enantiomer d-GlnF and other previously reported amino acid-fipronil conjugates. Inhibition experiments then suggested that the uptake of l-GlnF was, at least partially, mediated by an active transport mechanism. This inference was further strengthened by assimilation experiments with Xenopus oocytes and genetically modified Arabidopsis thaliana, which showed a direct correlation between the uptake of l-GlnF and the expression of amino acid transporter AtLHT1. Thus, conjugation with l-Gln appears to be a potential strategy to ensure the uptake of pesticides via an endogenous amino acid transport system.
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Affiliation(s)
- Xunyuan Jiang
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources and Key Laboratory of Natural Pesticide and Chemical Biology, Ministry of Education , South China Agricultural University , Guangzhou 510642 , China
| | - Yun Xie
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources and Key Laboratory of Natural Pesticide and Chemical Biology, Ministry of Education , South China Agricultural University , Guangzhou 510642 , China
| | - Zhanfu Ren
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources and Key Laboratory of Natural Pesticide and Chemical Biology, Ministry of Education , South China Agricultural University , Guangzhou 510642 , China
| | - Ulrika Ganeteg
- Umeå Plant Science Centre, Department of Forest Genetics and Plant Physiology , Swedish University of Agricultural Sciences , SE-901 83 Umeå , Sweden
| | - Fei Lin
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources and Key Laboratory of Natural Pesticide and Chemical Biology, Ministry of Education , South China Agricultural University , Guangzhou 510642 , China
| | - Chen Zhao
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources and Key Laboratory of Natural Pesticide and Chemical Biology, Ministry of Education , South China Agricultural University , Guangzhou 510642 , China
| | - Hanhong Xu
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources and Key Laboratory of Natural Pesticide and Chemical Biology, Ministry of Education , South China Agricultural University , Guangzhou 510642 , China
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15
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Kesinger E, Liu J, Jensen A, Chia CP, Demers A, Moriyama H. Influenza D virus M2 protein exhibits ion channel activity in Xenopus laevis oocytes. PLoS One 2018; 13:e0199227. [PMID: 29927982 PMCID: PMC6013169 DOI: 10.1371/journal.pone.0199227] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2018] [Accepted: 06/04/2018] [Indexed: 01/01/2023] Open
Abstract
BACKGROUND A new type of influenza virus, known as type D, has recently been identified in cattle and pigs. Influenza D virus infection in cattle is typically asymptomatic; however, its infection in swine can result in clinical disease. Swine can also be infected with all other types of influenza viruses, namely A, B, and C. Consequently, swine can serve as a "mixing vessel" for highly pathogenic influenza viruses, including those with zoonotic potential. Currently, the only antiviral drug available targets influenza M2 protein ion channel is not completely effective. Thus, it is necessary to develop an M2 ion channel blocker capable of suppressing the induction of resistance to the genetic shift. To provide a basis for developing novel ion channel-blocking compounds, we investigated the properties of influenza D virus M2 protein (DM2) as a drug target. RESULTS To test the ion channel activity of DM2, the DNA corresponding to DM2 with cMyc-tag conjugated to its carboxyl end was cloned into the shuttle vector pNCB1. The mRNA of the DM2-cMyc gene was synthesized and injected into Xenopus oocytes. The translation products of DM2-cMyc mRNA were confirmed by immunofluorescence and mass spectrometry analyses. The DM2-cMyc mRNA-injected oocytes were subjected to the two-electrode voltage-clamp (TEVC) method, and the induced inward current was observed. The midpoint (Vmid) values in Boltzmann modeling for oocytes injected with DM2-cMyc RNA or a buffer were -152 and -200 mV, respectively. Assuming the same expression level in the Xenopus oocytes, DM2 without tag and influenza C virus M2 protein (CM2) were subjected to the TEVC method. DM2 exhibited ion channel activity under the condition that CM2 ion channel activity was reproduced. The gating voltages represented by Vmid for CM2 and DM2 were -141 and -146 mV, respectively. The reversal potentials observed in ND96 for CM2 and DM2 were -21 and -22 mV, respectively. Compared with intact DM2, DM2 variants with mutation in the YxxxK motif, namely Y72A and K76A DM2, showed lower Vmid values while showing no change in reversal potential. CONCLUSION The M2 protein from newly isolated influenza D virus showed ion channel activity similar to that of CM2. The gating voltage was shown to be affected by the YxxxK motif and by the hydrophobicity and bulkiness of the carboxyl end of the molecule.
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Affiliation(s)
- Evan Kesinger
- School of Biological Sciences, University of Nebraska-Lincoln, Lincoln, Nebraska, United States of America
| | - Jianing Liu
- School of Biological Sciences, University of Nebraska-Lincoln, Lincoln, Nebraska, United States of America
| | - Aaron Jensen
- School of Biological Sciences, University of Nebraska-Lincoln, Lincoln, Nebraska, United States of America
| | - Catherine P. Chia
- School of Biological Sciences, University of Nebraska-Lincoln, Lincoln, Nebraska, United States of America
| | - Andrew Demers
- School of Biological Sciences, University of Nebraska-Lincoln, Lincoln, Nebraska, United States of America
| | - Hideaki Moriyama
- School of Biological Sciences, University of Nebraska-Lincoln, Lincoln, Nebraska, United States of America
- * E-mail:
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16
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Sheng Q, Liu X, Xie Y, Lin F, Zhang Z, Zhao C, Xu H. Synthesis of Novel Amino Acid-Fipronil Conjugates and Study on Their Phloem Loading Mechanism. Molecules 2018; 23:molecules23040778. [PMID: 29597301 PMCID: PMC6017586 DOI: 10.3390/molecules23040778] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2018] [Revised: 03/15/2018] [Accepted: 03/21/2018] [Indexed: 01/02/2023] Open
Abstract
To develop a new pesticide with phloem mobility, a series of new amino acid–fipronil conjugates were designed and synthesized based on derivatization at the 3-position of the pyrazole ring of fipronil. Experiments using a Ricinus communis seedling system showed that all tested conjugates were phloem mobile except for the isoleucine–fipronil conjugate, and that the serine–fipronil conjugate (4g) exhibited the highest concentration in phloem sap (52.00 ± 5.80 μM). According to prediction with log Cf values and uptake experiments with Xenopus oocytes, the phloem loading process of conjugate 4g involved both passive diffusion and an active carrier system (RcANT15). In particular, compared with for a previously reported glycinergic–fipronil conjugate (GlyF), passive diffusion played a more important role for conjugate 4g in the enhancement of phloem mobility. This study suggests that associating a nutrient at a different position of an existing pesticide structure could still be effective in obtaining phloem-mobile derivatives, but the distinct physicochemical properties of resultant conjugates may lead to different phloem loading mechanisms.
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Affiliation(s)
- Qingqing Sheng
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, South China Agricultural University, Guangzhou 510642, China.
- Key Laboratory of Natural Pesticide and Chemical Biology, Ministry of Education, South China Agricultural University, Guangzhou 510642, China.
| | - Xinxin Liu
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, South China Agricultural University, Guangzhou 510642, China.
- Key Laboratory of Natural Pesticide and Chemical Biology, Ministry of Education, South China Agricultural University, Guangzhou 510642, China.
| | - Yun Xie
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, South China Agricultural University, Guangzhou 510642, China.
- Key Laboratory of Natural Pesticide and Chemical Biology, Ministry of Education, South China Agricultural University, Guangzhou 510642, China.
| | - Fei Lin
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, South China Agricultural University, Guangzhou 510642, China.
- Key Laboratory of Natural Pesticide and Chemical Biology, Ministry of Education, South China Agricultural University, Guangzhou 510642, China.
| | - Zhixiang Zhang
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, South China Agricultural University, Guangzhou 510642, China.
- Key Laboratory of Natural Pesticide and Chemical Biology, Ministry of Education, South China Agricultural University, Guangzhou 510642, China.
| | - Chen Zhao
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, South China Agricultural University, Guangzhou 510642, China.
- Key Laboratory of Natural Pesticide and Chemical Biology, Ministry of Education, South China Agricultural University, Guangzhou 510642, China.
| | - Hanhong Xu
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, South China Agricultural University, Guangzhou 510642, China.
- Key Laboratory of Natural Pesticide and Chemical Biology, Ministry of Education, South China Agricultural University, Guangzhou 510642, China.
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17
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Wang S, Mitani-Ueno N, Takano J. Boron Uptake Assay in Xenopus laevis Oocytes. Bio Protoc 2018; 8:e2755. [PMID: 34179281 DOI: 10.21769/bioprotoc.2755] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2017] [Revised: 02/19/2018] [Accepted: 02/21/2018] [Indexed: 11/02/2022] Open
Abstract
Boron (B) is essential for plant growth and taken up by plant roots as boric acid. Under B limitation, B uptake and translocation in plants are dependent on the boric acid channels located in the plasma membrane. Xenopus leavis oocyte is a reliable heterologous expression system to characterize transport activities of boric acid channels and related major intrinsic proteins (aquaporins). Here, we outline the protocols for expression of boric acid channels and boric acid uptake assay in Xenopus leavis oocytes.
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Affiliation(s)
- Sheliang Wang
- Graduate School of Life and Environmental Sciences, Osaka Prefecture University, Sakai, Japan
| | - Namiki Mitani-Ueno
- Institute of Plant Science and Resources, Okayama University, Kurashiki, Japan
| | - Junpei Takano
- Graduate School of Life and Environmental Sciences, Osaka Prefecture University, Sakai, Japan
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18
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Aguero T, Newman K, King ML. Microinjection of Xenopus Oocytes. Cold Spring Harb Protoc 2018; 2018:pdb.prot096974. [PMID: 29321284 DOI: 10.1101/pdb.prot096974] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Microinjection of Xenopus oocytes has proven to be a valuable tool in a broad array of studies that require expression of DNA or RNA into functional protein. These studies are diverse and range from expression cloning to receptor-ligand interaction to nuclear programming. Oocytes offer a number of advantages for such studies, including their large size (∼1.2 mm in diameter), capacity for translation, and enormous nucleus (0.3-0.4 mm). They are cost effective, easily manipulated, and can be injected in large numbers in a short time period. Oocytes have a large maternal stockpile of all the essential components for transcription and translation. Consequently, the investigator needs only to introduce by microinjection the specific DNA or RNA of interest for synthesis. Oocytes translate virtually any exogenous RNA regardless of source, and the translated proteins are folded, modified, and transported to the correct cellular locations. Here we present procedures for the efficient microinjection of oocytes and their subsequent care.
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Affiliation(s)
- Tristan Aguero
- Department of Cell Biology, University of Miami School of Medicine, Miami, Florida 33136
| | - Karen Newman
- Department of Cell Biology, University of Miami School of Medicine, Miami, Florida 33136
| | - Mary Lou King
- Department of Cell Biology, University of Miami School of Medicine, Miami, Florida 33136
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19
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Mao GL, Yan Y, Chen Y, Wang BF, Xu FF, Zhang ZX, Lin F, Xu HH. Family of Ricinus communis Monosaccharide Transporters and RcSTP1 in Promoting the Uptake of a Glucose-Fipronil Conjugate. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2017; 65:6169-6178. [PMID: 28692262 DOI: 10.1021/acs.jafc.7b02044] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Enhancing the systemic distribution of a bioactive compound by exploiting the vascular transport system of a plant presents a means of reducing both the volume and frequency of pesticide/fungicide application. The foliar uptake of the glucose-fipronil conjugate N-[3-cyano-1-[2,6-dichloro-4-(trifluoromethyl)phenyl]-4-[(trifluoromethyl)sulfinyl]-1H-pyrazol-5-yl]-1-(β-d-glucopyranosyl)-1H-1,2,3-triazole-4-methanamine (GTF) achieved in castor bean (Ricinus communis) and its transport via the phloem are known to be mediated by monosaccharide transporter(s) [MST(s)], although neither the identity of the key MST(s) involved nor the mechanistic basis of its movement have yet to be described. On the basis of homology with Arabidopsis thaliana sugar transporters, the castor bean genome was concluded to harbor 53 genes encoding a sugar transporter, falling into the eight previously defined subfamilies INT, PMT, VGT, STP, ERD6, pGlucT, TMT, and SUT. Transcriptional profiling identified the product of RcSTP1 as a candidate for mediating GTF uptake, because this gene was induced by exposure of the plant to GTF. When RcSTP1 was transiently expressed in onion epidermis cells, the site of RcSTP1 deposition was shown to be the plasma membrane. A functional analysis based on RcSTP1 expression in Xenopus laevis oocytes demonstrated that its product has a high affinity for GTF. The long-distance root-to-shoot transport of GTF was enhanced in a transgenic soybean chimera constitutively expressing RcSTP1.
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Affiliation(s)
- Gen-Lin Mao
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources and Key Laboratory of Natural Pesticide and Chemical Biology, Ministry of Education, South China Agricultural University , Guangzhou, Guangdong 510642, People's Republic of China
| | - Yin Yan
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources and Key Laboratory of Natural Pesticide and Chemical Biology, Ministry of Education, South China Agricultural University , Guangzhou, Guangdong 510642, People's Republic of China
| | - Yan Chen
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources and Key Laboratory of Natural Pesticide and Chemical Biology, Ministry of Education, South China Agricultural University , Guangzhou, Guangdong 510642, People's Republic of China
| | - Bing-Feng Wang
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources and Key Laboratory of Natural Pesticide and Chemical Biology, Ministry of Education, South China Agricultural University , Guangzhou, Guangdong 510642, People's Republic of China
| | - Fei-Fei Xu
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources and Key Laboratory of Natural Pesticide and Chemical Biology, Ministry of Education, South China Agricultural University , Guangzhou, Guangdong 510642, People's Republic of China
| | - Zhi-Xiang Zhang
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources and Key Laboratory of Natural Pesticide and Chemical Biology, Ministry of Education, South China Agricultural University , Guangzhou, Guangdong 510642, People's Republic of China
| | - Fei Lin
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources and Key Laboratory of Natural Pesticide and Chemical Biology, Ministry of Education, South China Agricultural University , Guangzhou, Guangdong 510642, People's Republic of China
| | - Han-Hong Xu
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources and Key Laboratory of Natural Pesticide and Chemical Biology, Ministry of Education, South China Agricultural University , Guangzhou, Guangdong 510642, People's Republic of China
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20
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Tang Z, Chen Y, Chen F, Ji Y, Zhao FJ. OsPTR7 (OsNPF8.1), a Putative Peptide Transporter in Rice, is Involved in Dimethylarsenate Accumulation in Rice Grain. PLANT & CELL PHYSIOLOGY 2017; 58:904-913. [PMID: 28340032 DOI: 10.1093/pcp/pcx029] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/08/2017] [Accepted: 02/14/2017] [Indexed: 05/20/2023]
Abstract
Rice (Oryza sativa) is a major dietary source of arsenic (As) for the population consuming rice as their staple food. Rice grain contains both inorganic As and methylated As species, especially dimethyarsinate (DMA). DMA is highly mobile in long-distance translocation in plants, but the underlying mechanism remains unknown. In the present study, we showed that OsPTR7 (OsNPF8.1), a putative peptide transporter in rice, was permeable to DMA in Xenopus laevis oocytes. Transient expression of the OsPTR7-green fluorescent protein (GFP) in tobacco protoplasts showed that OsPTR7 was localized in the cell plasma membrane. Quantitative real-time PCR analysis showed that OsPTR7 was more highly expressed in the shoots than in the roots at the seedling stage. At the flowering and grain-filling stage, the OsPTR7 transcript was abundant in the leaves, node I and roots. Knockout or knockdown mutants of OsPTR7 had significantly decreased root to shoot translocation of DMA compared with wild-type plants and accumulated less As in the brown rice. In field-grown plants, DMA accounted for 35% of the total As in the brown rice of wild-type plants but was undetectable in the knockout mutant. Our study demonstrates that OsPTR7 is involved in the long-distance translocation of DMA and contributes to the accumulation of DMA in rice grain.
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Affiliation(s)
- Zhong Tang
- State Key Laboratory of Crop Genetics and Germplasm Enhancement, College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing, China
| | - Yi Chen
- Department of Metabolic Biology, John Innes Centre, Norwich Research Park, Norwich, UK
| | - Fei Chen
- State Key Laboratory of Crop Genetics and Germplasm Enhancement, College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing, China
| | - Yuchen Ji
- State Key Laboratory of Crop Genetics and Germplasm Enhancement, College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing, China
| | - Fang-Jie Zhao
- State Key Laboratory of Crop Genetics and Germplasm Enhancement, College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing, China
- Rothamsted Research, Harpenden, Hertfordshire, UK
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21
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Lefoulon C, Boeglin M, Moreau B, Véry AA, Szponarski W, Dauzat M, Michard E, Gaillard I, Chérel I. The Arabidopsis AtPP2CA Protein Phosphatase Inhibits the GORK K+ Efflux Channel and Exerts a Dominant Suppressive Effect on Phosphomimetic-activating Mutations. J Biol Chem 2016; 291:6521-33. [PMID: 26801610 DOI: 10.1074/jbc.m115.711309] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2015] [Indexed: 12/13/2022] Open
Abstract
The regulation of the GORK (Guard Cell Outward Rectifying) Shaker channel mediating a massive K(+) efflux in Arabidopsis guard cells by the phosphatase AtPP2CA was investigated. Unlike the gork mutant, the atpp2ca mutants displayed a phenotype of reduced transpiration. We found that AtPP2CA interacts physically with GORK and inhibits GORK activity in Xenopus oocytes. Several amino acid substitutions in the AtPP2CA active site, including the dominant interfering G145D mutation, disrupted the GORK-AtPP2CA interaction, meaning that the native conformation of the AtPP2CA active site is required for the GORK-AtPP2CA interaction. Furthermore, two serines in the GORK ankyrin domain that mimic phosphorylation (Ser to Glu) or dephosphorylation (Ser to Ala) were mutated. Mutations mimicking phosphorylation led to a significant increase in GORK activity, whereas mutations mimicking dephosphorylation had no effect on GORK. In Xenopus oocytes, the interaction of AtPP2CA with "phosphorylated" or "dephosphorylated" GORK systematically led to inhibition of the channel to the same baseline level. Single-channel recordings indicated that the GORK S722E mutation increases the open probability of the channel in the absence, but not in the presence, of AtPP2CA. The dephosphorylation-independent inactivation mechanism of GORK by AtPP2CA is discussed in relation with well known conformational changes in animal Shaker-like channels that lead to channel opening and closing. In plants, PP2C activity would control the stomatal aperture by regulating both GORK and SLAC1, the two main channels required for stomatal closure.
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Affiliation(s)
- Cécile Lefoulon
- From the Laboratoire de Biochimie et Physiologie Moléculaire des Plantes, CNRS/INRA/SupAgro/UM2, Unité Mixte de Recherche (UMR) 5004, 2 Place Viala, 34060 Montpellier Cedex, France and
| | - Martin Boeglin
- From the Laboratoire de Biochimie et Physiologie Moléculaire des Plantes, CNRS/INRA/SupAgro/UM2, Unité Mixte de Recherche (UMR) 5004, 2 Place Viala, 34060 Montpellier Cedex, France and
| | - Bertrand Moreau
- From the Laboratoire de Biochimie et Physiologie Moléculaire des Plantes, CNRS/INRA/SupAgro/UM2, Unité Mixte de Recherche (UMR) 5004, 2 Place Viala, 34060 Montpellier Cedex, France and
| | - Anne-Aliénor Véry
- From the Laboratoire de Biochimie et Physiologie Moléculaire des Plantes, CNRS/INRA/SupAgro/UM2, Unité Mixte de Recherche (UMR) 5004, 2 Place Viala, 34060 Montpellier Cedex, France and
| | - Wojciech Szponarski
- From the Laboratoire de Biochimie et Physiologie Moléculaire des Plantes, CNRS/INRA/SupAgro/UM2, Unité Mixte de Recherche (UMR) 5004, 2 Place Viala, 34060 Montpellier Cedex, France and
| | - Myriam Dauzat
- the Laboratoire d'Ecophysiologie des Plantes sous Stress Environnementaux, INRA/SupAgro, UMR 759, 2 Place Viala, 34060 Montpellier Cedex, France
| | - Erwan Michard
- From the Laboratoire de Biochimie et Physiologie Moléculaire des Plantes, CNRS/INRA/SupAgro/UM2, Unité Mixte de Recherche (UMR) 5004, 2 Place Viala, 34060 Montpellier Cedex, France and
| | - Isabelle Gaillard
- From the Laboratoire de Biochimie et Physiologie Moléculaire des Plantes, CNRS/INRA/SupAgro/UM2, Unité Mixte de Recherche (UMR) 5004, 2 Place Viala, 34060 Montpellier Cedex, France and
| | - Isabelle Chérel
- From the Laboratoire de Biochimie et Physiologie Moléculaire des Plantes, CNRS/INRA/SupAgro/UM2, Unité Mixte de Recherche (UMR) 5004, 2 Place Viala, 34060 Montpellier Cedex, France and
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22
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Abstract
The oocytes of the African clawed frog (Xenopus laevis) comprise one of the most widely used membrane protein expression systems. While frequently used for studies of transporters and ion channels, the application of this system to the study of mechanosensitive ion channels has been overlooked, perhaps due to a relative abundance of native expression systems. Recent advances, however, have illustrated the advantages of the oocyte system for studying plant and bacterial mechanosensitive channels. Here we describe in detail the methods used for heterologous expression and characterization of bacterial and plant mechanosensitive channels in Xenopus oocytes.
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Affiliation(s)
- Grigory Maksaev
- Department of Biology, Washington University in Saint Louis, One Brookings Drive, Mail Code 1137, Saint Louis, MO, 63130, USA
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23
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Sasaki T, Tsuchiya Y, Ariyoshi M, Ryan PR, Furuichi T, Yamamoto Y. A domain-based approach for analyzing the function of aluminum-activated malate transporters from wheat (Triticum aestivum) and Arabidopsis thaliana in Xenopus oocytes. PLANT & CELL PHYSIOLOGY 2014; 55:2126-38. [PMID: 25311199 DOI: 10.1093/pcp/pcu143] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Wheat and Arabidopsis plants respond to aluminum (Al) ions by releasing malate from their root apices via Al-activated malate transporter. Malate anions bind with the toxic Al ions and contribute to the Al tolerance of these species. The genes encoding the transporters in wheat and Arabidopsis, TaALMT1 and AtALMT1, respectively, were expressed in Xenopus laevis oocytes and characterized electrophysiologically using the two-electrode voltage clamp system. The Al-activated currents generated by malate efflux were detected for TaALMT1 but not for AtALMT1. Chimeric proteins were generated by swapping the N- and C-terminal halves of TaALMT1 and AtALMT1 (Ta::At and At::Ta). When these chimeras were characterized in oocytes, Al-activated malate efflux was detected for the Ta::At chimera but not for At::Ta, suggesting that the N-terminal half of TaALMT1 is necessary for function in oocytes. An additional chimera, Ta(48)::At, generated by swapping 17 residues from the N-terminus of AtALMT1 with the equivalent 48 residues from TaALMT1, was sufficient to support transport activity. This 48 residue region includes a helical region with a putative transmembrane domain which is absent in AtALMT1. The deletion of this domain from Ta(48)::At led to the complete loss of transport activity. Furthermore, truncations and a deletion at the C-terminal end of TaALMT1 indicated that a putative helical structure in this region was also required for transport function. This study provides insights into the structure-function relationships of Al-activated ALMT proteins by identifying specific domains on the N- and C-termini of TaALMT1 that are critical for basal transport function and Al responsiveness in oocytes.
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Affiliation(s)
- Takayuki Sasaki
- Institute of Plant Science and Resources, Okayama University, Chuo 2-20-1, Kurashiki, Okayama, 710-0046 Japan
| | - Yoshiyuki Tsuchiya
- Institute of Plant Science and Resources, Okayama University, Chuo 2-20-1, Kurashiki, Okayama, 710-0046 Japan
| | - Michiyo Ariyoshi
- Institute of Plant Science and Resources, Okayama University, Chuo 2-20-1, Kurashiki, Okayama, 710-0046 Japan
| | - Peter R Ryan
- CSIRO Agriculture, GPO Box 1600, Canberra, ACT 2601, Australia
| | - Takuya Furuichi
- Department of Health and Nutrition, Faculty of Home Economics, Gifu Women's University, Taromaru 80, Gifu, 501-2592 Japan
| | - Yoko Yamamoto
- Institute of Plant Science and Resources, Okayama University, Chuo 2-20-1, Kurashiki, Okayama, 710-0046 Japan
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Feng H, Xia X, Fan X, Xu G, Miller AJ. Optimizing plant transporter expression in Xenopus oocytes. PLANT METHODS 2013; 9:48. [PMID: 24359672 PMCID: PMC3878178 DOI: 10.1186/1746-4811-9-48] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/02/2013] [Accepted: 12/13/2013] [Indexed: 05/02/2023]
Abstract
BACKGROUND Rapid improvements in DNA synthesis technology are revolutionizing gene cloning and the characterization of their encoded proteins. Xenopus laevis oocytes are a commonly used heterologous system for the expression and functional characterization of membrane proteins. For many plant proteins, particularly transporters, low levels of expression can limit functional activity in these cells making it difficult to characterize the protein. Improvements in synthetic DNA technology now make it quick, easy and relatively cheap to optimize the codon usage of plant cDNAs for Xenopus. We have tested if this optimization process can improve the functional activity of a two-component plant nitrate transporter assayed in oocytes. RESULTS We used the generally available software (http://www.kazusa.or.jp/codon/; http://genomes.urv.es/OPTIMIZER/) to predict a DNA sequence for the plant gene that is better suited for Xenopus laevis. Rice OsNAR2.1 and OsNRT2.3a DNA optimized sequences were commercially synthesized for Xenopus expression. The template DNA was used to synthesize cRNA using a commercially available kit. Oocytes were injected with cRNA mixture of optimized and original OsNAR2.1 and OsNRT2.3a. Oocytes injected with cRNA obtained from using the optimized DNA template could accumulate significantly more NO3- than the original genes after 16 h incubation in 0.5 mM Na15NO3. Two-electrode voltage clamp analysis of the oocytes confirmed that the codon optimized template resulted in significantly larger currents when compared with the original rice cDNA. CONCLUSION The functional activity of a rice high affinity nitrate transporter in oocytes was improved by DNA codon optimization of the genes. This methodology offers the prospect for improved expression and better subsequent functional characterization of plant proteins in the Xenopus oocyte system.
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Affiliation(s)
- Huimin Feng
- State Key Laboratory of Crop Genetics and Germplasm Enhancement, College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing 210095, PR China
- Department of Metabolic Biology, John Innes Centre, Norwich Research Park NR4 7UH, UK
| | - Xiudong Xia
- State Key Laboratory of Crop Genetics and Germplasm Enhancement, College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing 210095, PR China
| | - Xiaorong Fan
- State Key Laboratory of Crop Genetics and Germplasm Enhancement, College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing 210095, PR China
- Department of Metabolic Biology, John Innes Centre, Norwich Research Park NR4 7UH, UK
| | - Guohua Xu
- State Key Laboratory of Crop Genetics and Germplasm Enhancement, College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing 210095, PR China
| | - Anthony J Miller
- Department of Metabolic Biology, John Innes Centre, Norwich Research Park NR4 7UH, UK
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25
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Debono MW. Dynamic protoneural networks in plants: a new approach of spontaneous extracellular potential variations. PLANT SIGNALING & BEHAVIOR 2013; 8:e24207. [PMID: 23603975 PMCID: PMC3907453 DOI: 10.4161/psb.24207] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/26/2013] [Revised: 03/05/2013] [Accepted: 03/05/2013] [Indexed: 05/23/2023]
Abstract
Taking as a basis of discussion Kalanchoe's spontaneous and evoked extracellular activities recorded at the whole plant level, we put the challenging questions: do these low-voltage variations, together with endocellular events, reflect integrative properties and complex behavior in plants? Does it reflect common perceptive systems in animal and plant species? Is the ability of plants to treat short-term variations and information transfer without nervous system relevant? Is a protoneural construction of the world by lower organisms possible? More generally, the aim of this paper is to reevaluate the probably underestimated role of plant surface potentials in the plant relation life, carefully comparing the biogenesis of both animal and plant organisms in the era of plant neurobiology. Knowing that surface potentials participate at least to morphogenesis, cell to cell coupling, long distance transmission and transduction of stimuli, some hypothesis are given indicating that plants have to be studied as environmental biosensors and non linear dynamic systems able to detect transitional states between perception and response to stimuli. This study is conducted in the frame of the "plasticity paradigm," which gives a theoretical model of evolutionary processes and suggests some hypothesis about the nature of complexity, information and behavior.
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Grewer C, Gameiro A, Mager T, Fendler K. Electrophysiological characterization of membrane transport proteins. Annu Rev Biophys 2013; 42:95-120. [PMID: 23451896 DOI: 10.1146/annurev-biophys-083012-130312] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Active transport in biological membranes has been traditionally studied using a variety of biochemical and biophysical techniques, including electrophysiology. This review focuses on aspects of electrophysiological methods that make them particularly suited for the investigation of transporter function. Two major approaches to electrical recording of transporter activity are discussed: (a) artificial planar lipid membranes, such as the black lipid membrane and solid supported membrane, which are useful for studies on bacterial transporters and transporters of intracellular compartments, and (b) patch clamp and voltage clamp techniques, which investigate transporters in native cellular membranes. The analytical power of these methods is highlighted by several examples of mechanistic studies of specific membrane proteins, including cytochrome c oxidase, NhaA Na(+)/H(+) exchanger, ClC-7 H(+)/Cl(-) exchanger, glutamate transporters, and neutral amino acid transporters. These examples reveal the wealth of mechanistic information that can be obtained when electrophysiological methods are used in combination with rapid perturbation approaches.
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Affiliation(s)
- Christof Grewer
- Department of Chemistry, Binghamton University, Binghamton, New York, 13902, USA.
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27
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Maksaev G, Haswell ES. MscS-Like10 is a stretch-activated ion channel from Arabidopsis thaliana with a preference for anions. Proc Natl Acad Sci U S A 2012; 109:19015-20. [PMID: 23112188 PMCID: PMC3503204 DOI: 10.1073/pnas.1213931109] [Citation(s) in RCA: 94] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Like many other organisms, plants are capable of sensing and responding to mechanical stimuli such as touch, osmotic pressure, and gravity. One mechanism for the perception of force is the activation of mechanosensitive (or stretch-activated) ion channels, and a number of mechanosensitive channel activities have been described in plant membranes. Based on their homology to the bacterial mechanosensitive channel MscS, the 10 MscS-Like (MSL) proteins of Arabidopsis thaliana have been hypothesized to form mechanosensitive channels in plant cell and organelle membranes. However, definitive proof that MSLs form mechanosensitive channels has been lacking. Here we used single-channel patch clamp electrophysiology to show that MSL10 is capable of providing a MS channel activity when heterologously expressed in Xenopus laevis oocytes. This channel had a conductance of ∼100 pS, consistent with the hypothesis that it underlies an activity previously observed in the plasma membrane of plant root cells. We found that MSL10 formed a channel with a moderate preference for anions, which was modulated by strongly positive and negative membrane potentials, and was reversibly inhibited by gadolinium, a known inhibitor of mechanosensitive channels. MSL10 demonstrated asymmetric activation/inactivation kinetics, with the channel closing at substantially lower tensions than channel opening. The electrophysiological characterization of MSL10 reported here provides insight into the evolution of structure and function of this important family of proteins.
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Affiliation(s)
- Grigory Maksaev
- Department of Biology, Washington University in St. Louis, St. Louis, MO 63130
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28
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Qin L, Guo Y, Chen L, Liang R, Gu M, Xu G, Zhao J, Walk T, Liao H. Functional characterization of 14 Pht1 family genes in yeast and their expressions in response to nutrient starvation in soybean. PLoS One 2012; 7:e47726. [PMID: 23133521 PMCID: PMC3485015 DOI: 10.1371/journal.pone.0047726] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2012] [Accepted: 09/20/2012] [Indexed: 12/26/2022] Open
Abstract
BACKGROUND Phosphorus (P) is essential for plant growth and development. Phosphate (Pi) transporter genes in the Pht1 family play important roles in Pi uptake and translocation in plants. Although Pht1 family genes have been well studied in model plants, little is known about their functions in soybean, an important legume crop worldwide. PRINCIPAL FINDINGS We identified and isolated a complete set of 14 Pi transporter genes (GmPT1-14) in the soybean genome and categorized them into two subfamilies based on phylogenetic analysis. Then, an experiment to elucidate Pi transport activity of the GmPTs was carried out using a yeast mutant defective in high-affinity Pi transport. Results showed that 12 of the 14 GmPTs were able to complement Pi uptake of the yeast mutant with Km values ranging from 25.7 to 116.3 µM, demonstrating that most of the GmPTs are high-affinity Pi transporters. Further results from qRT-PCR showed that the expressions of the 14 GmPTs differed not only in response to P availability in different tissues, but also to other nutrient stresses, including N, K and Fe deficiency, suggesting that besides functioning in Pi uptake and translocation, GmPTs might be involved in synergistic regulation of mineral nutrient homeostasis in soybean. CONCLUSIONS The comprehensive analysis of Pi transporter function in yeast and expression responses to nutrition starvation of Pht1 family genes in soybean revealed their involvement in other nutrient homeostasis besides P, which could help to better understand the regulation network among ion homeostasis in plants.
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Affiliation(s)
- Lu Qin
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, Root Biology Center, South China Agricultural University, Guangzhou, China
| | - Yongxiang Guo
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, Root Biology Center, South China Agricultural University, Guangzhou, China
| | - Liyu Chen
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, Root Biology Center, South China Agricultural University, Guangzhou, China
| | - Ruikang Liang
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, Root Biology Center, South China Agricultural University, Guangzhou, China
| | - Mian Gu
- State Key Laboratory of Crop Genetics and Germplasm Enhancement, College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing, China
| | - Guohua Xu
- State Key Laboratory of Crop Genetics and Germplasm Enhancement, College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing, China
| | - Jing Zhao
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, Root Biology Center, South China Agricultural University, Guangzhou, China
| | - Thomas Walk
- USDA-ARS, U.S. Pacific Basin Agricultural Research Center, Hilo, Hawaii, United States of America
| | - Hong Liao
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, Root Biology Center, South China Agricultural University, Guangzhou, China
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29
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Grégoire C, Rémus-Borel W, Vivancos J, Labbé C, Belzile F, Bélanger RR. Discovery of a multigene family of aquaporin silicon transporters in the primitive plant Equisetum arvense. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2012; 72:320-30. [PMID: 22712876 DOI: 10.1111/j.1365-313x.2012.05082.x] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
Plants benefit greatly from silicon (Si) absorption provided that they contain Si transporters. The latter have recently been identified in the roots of some higher plants known to accumulate high concentrations of Si, and all share a high level of sequence identity. In this study, we searched for transporters in the primitive vascular plant Equisetum arvense (horsetail), which is a valuable but neglected model plant for the study of Si absorption, as it has one of the highest Si concentrations in the plant kingdom. Our initial attempts to identify Si transporters based on sequence homology with transporters from higher plants proved unsuccessful, suggesting a divergent structure or property in horsetail transporters. Subsequently, through sequencing of the horsetail root transcriptome and a search using amino acid sequences conserved in plant aquaporins, we were able to identify a multigene family of aquaporin Si transporters. Comparison of known functional domains and phylogenetic analysis of sequences revealed that the horsetail proteins belong to a different group than higher-plant Si transporters. In particular, the newly identified proteins contain a STAR pore as opposed to the GSGR pore common to all previously identified Si transporters. In order to determine its functionality, the proteins were heterologously expressed in both Xenopus oocytes and Arabidopsis, and the results showed that the horsetail proteins are extremely efficient a transporting Si. These findings offer new insights into the elusive properties of Si and its absorption by plants.
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Affiliation(s)
- Caroline Grégoire
- Département de Phytologie-Faculté des Sciences de l'Agriculture et de l'Alimentation, Centre de Recherche en Horticulture, Université Laval, Pavillon Paul-Comtois, Québec City, QC G1V 0A6, Canada
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30
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Haferkamp I, Linka N. Functional expression and characterisation of membrane transport proteins. PLANT BIOLOGY (STUTTGART, GERMANY) 2012; 14:675-90. [PMID: 22639981 DOI: 10.1111/j.1438-8677.2012.00591.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
Membrane transporters set the framework organising the complexity of plant metabolism in cells, tissues and organisms. Their substrate specificity and controlled activity in different cells is a crucial part for plant metabolism to run pathways in concert. Transport proteins catalyse the uptake and exchange of ions, substrates, intermediates, products and cofactors across membranes. Given the large number of metabolites, a wide spectrum of transporters is required. The vast majority of in silico annotated membrane transporters in plant genomes, however, has not yet been functionally characterised. Hence, to understand the metabolic network as a whole, it is important to understand how transporters connect and control the metabolic pathways of plant cells. Heterologous expression and in vitro activity studies of recombinant transport proteins have highly improved their functional analysis in the last two decades. This review provides a comprehensive overview of the recent advances in membrane protein expression and functional characterisation using various host systems and transport assays.
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Affiliation(s)
- I Haferkamp
- Plant Physiology, Technical University of Kaiserslautern, Kaiserslautern, Germany Plant Biochemistry, Heinrich Heine University Düsseldorf, Düsseldorf, Germany
| | - N Linka
- Plant Physiology, Technical University of Kaiserslautern, Kaiserslautern, Germany Plant Biochemistry, Heinrich Heine University Düsseldorf, Düsseldorf, Germany
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31
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Ladwig F, Stahl M, Ludewig U, Hirner AA, Hammes UZ, Stadler R, Harter K, Koch W. Siliques are Red1 from Arabidopsis acts as a bidirectional amino acid transporter that is crucial for the amino acid homeostasis of siliques. PLANT PHYSIOLOGY 2012; 158:1643-55. [PMID: 22312005 PMCID: PMC3320175 DOI: 10.1104/pp.111.192583] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
Many membrane proteins are involved in the transport of nutrients in plants. While the import of amino acids into plant cells is, in principle, well understood, their export has been insufficiently described. Here, we present the identification and characterization of the membrane protein Siliques Are Red1 (SIAR1) from Arabidopsis (Arabidopsis thaliana) that is able to translocate amino acids bidirectionally into as well as out of the cell. Analyses in yeast and oocytes suggest a SIAR1-mediated export of amino acids. In Arabidopsis, SIAR1 localizes to the plasma membrane and is expressed in the vascular tissue, in the pericycle, in stamen, and in the chalazal seed coat of ovules and developing seeds. Mutant alleles of SIAR1 accumulate anthocyanins as a symptom of reduced amino acid content in the early stages of silique development. Our data demonstrate that the SIAR1-mediated export of amino acids plays an important role in organic nitrogen allocation and particularly in amino acid homeostasis in developing siliques.
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Affiliation(s)
- Friederike Ladwig
- Zentrum für Molekularbiologie der Pflanzen, Plant Physiology, D-72076 Tuebingen, Germany.
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32
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Rodríguez A, Benito B, Cagnac O. Using heterologous expression systems to characterize potassium and sodium transport activities. Methods Mol Biol 2012; 913:371-386. [PMID: 22895773 DOI: 10.1007/978-1-61779-986-0_25] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
The expression of plant transporters in simple well-characterized cell systems is an irreplaceable technique for gaining insights into the kinetic and energetic features of plant transporters. Among all the available expression systems, yeast cells offer the highest simplicity and have the capacity to mimic the in vivo properties of plant transporters. Here, we describe the use of yeast mutants to express K(+) and Na(+) plant transporters and discuss some experimental problems that can produce misleading results.
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Affiliation(s)
- Alonso Rodríguez
- Centro de Biotecnología y Genómica de Plantas, Universidad Politecnica de Madrid, Madrid, Spain.
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33
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Maksaev G, Haswell ES. Expression and characterization of the bacterial mechanosensitive channel MscS in Xenopus laevis oocytes. ACTA ACUST UNITED AC 2011; 138:641-9. [PMID: 22084416 PMCID: PMC3226970 DOI: 10.1085/jgp.201110723] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
We have successfully expressed and characterized mechanosensitive channel of small conductance (MscS) from Escherichia coli in oocytes of the African clawed frog, Xenopus laevis. MscS expressed in oocytes has the same single-channel conductance and voltage dependence as the channel in its native environment. Two hallmarks of MscS activity, the presence of conducting substates at high potentials and reversible adaptation to a sustained stimulus, are also exhibited by oocyte-expressed MscS. In addition to its ease of use, the oocyte system allows the user to work with relatively large patches, which could be an advantage for the visualization of membrane deformation. Furthermore, MscS can now be compared directly to its eukaryotic homologues or to other mechanosensitive channels that are not easily studied in E. coli.
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Affiliation(s)
- Grigory Maksaev
- Department of Biology, Washington University in Saint Louis, Saint Louis, MO 63130, USA
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34
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Richards R, Dempski RE. Examining the conformational dynamics of membrane proteins in situ with site-directed fluorescence labeling. J Vis Exp 2011:2627. [PMID: 21673634 PMCID: PMC3197104 DOI: 10.3791/2627] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Two electrode voltage clamp electrophysiology (TEVC) is a powerful tool to investigate the mechanism of ion transport1 for a wide variety of membrane proteins including ion channels2, ion pumps3, and transporters4. Recent developments have combined site-specific fluorophore labeling alongside TEVC to concurrently examine the conformational dynamics at specific residues and function of these proteins on the surface of single cells. We will describe a method to study the conformational dynamics of membrane proteins by simultaneously monitoring fluorescence and current changes using voltage-clamp fluorometry. This approach can be used to examine the molecular motion of membrane proteins site-specifically following cysteine replacement and site-directed fluorophore labeling5,6. Furthermore, this method provides an approach to determine distance constraints between specific residues7,8. This is achieved by selectively attaching donor and acceptor fluorophores to two mutated cysteine residues of interest. In brief, these experiments are performed following functional expression of the desired protein on the surface of Xenopus leavis oocytes. The large surface area of these oocytes enables facile functional measurements and a robust fluorescence signal5. It is also possible to readily change the extracellular conditions such as pH, ligand or cations/anions, which can provide further information on the mechanism of membrane proteins4. Finally, recent developments have also enabled the manipulation of select internal ions following co-expression with a second protein9. Our protocol is described in multiple parts. First, cysteine scanning mutagenesis proceeded by fluorophore labeling is completed at residues located at the interface of the transmembrane and extracellular domains. Subsequent experiments are designed to identify residues which demonstrate large changes in fluorescence intensity (<5%)3 upon a conformational change of the protein. Second, these changes in fluorescence intensity are compared to the kinetic parameters of the membrane protein in order to correlate the conformational dynamics to the function of the protein10. This enables a rigorous biophysical analysis of the molecular motion of the target protein. Lastly, two residues of the holoenzyme can be labeled with a donor and acceptor fluorophore in order to determine distance constraints using donor photodestruction methods. It is also possible to monitor the relative movement of protein subunits following labeling with a donor and acceptor fluorophore.
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Affiliation(s)
- Ryan Richards
- Department of Chemistry and Biochemistry, Worcester Polytechnic Institute
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35
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Preuss CP, Huang CY, Tyerman SD. Proton-coupled high-affinity phosphate transport revealed from heterologous characterization in Xenopus of barley-root plasma membrane transporter, HvPHT1;1. PLANT, CELL & ENVIRONMENT 2011; 34:681-9. [PMID: 21309796 DOI: 10.1111/j.1365-3040.2010.02272.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
High-affinity phosphate transporters mediate uptake of inorganic phosphate (P(i) ) from soil solution under low P(i) conditions. The electrophysiological properties of any plant high-affinity P(i) transporter have not been described yet. Here, we report the detailed characterization of electrophysiological properties of the barley P(i) transporter, HvPHT1;1 in Xenopus laevis oocytes. A very low K(m) value (1.9 µm) for phosphate transport was observed in HvPHT1;1, which falls within the concentration range observed for barley roots. Inward currents at negative membrane potentials were identified as nH+ :P(i)⁻ (n > 1) co-transport based on simultaneous P(i) radiotracer uptake, oocyte voltage clamping and pH dependence. HvPHT1;1 showed preferential selectivity for P(i) and arsenate, but no transport of the other oxyanions SO₄²⁻ and NO₃⁻. In addition, HvPHT1;1 locates to the plasma membrane when expressed in onion (Allium cepa L.) epidermal cells, and is highly expressed in root segments with dense hairs. The electrophysiological properties, plasma membrane localization and cell-specific expression pattern of HvPHT1;1 support its role in the uptake of P(i) under low P(i) conditions.
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Affiliation(s)
- Christian P Preuss
- School of Agriculture, Food and Wine, The University of Adelaide, South Australia, Australia
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36
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Horchani F, R`bia O, Hajri R, Aschi-Smit S. Retracted: Nitrogen Nutrition and Ammonium Toxicity in Higher Plants. ACTA ACUST UNITED AC 2010. [DOI: 10.3923/ijb.2011.1.16] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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37
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Preuss CP, Huang CY, Gilliham M, Tyerman SD. Channel-like characteristics of the low-affinity barley phosphate transporter PHT1;6 when expressed in Xenopus oocytes. PLANT PHYSIOLOGY 2010; 152:1431-41. [PMID: 20053709 PMCID: PMC2832247 DOI: 10.1104/pp.109.152009] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/06/2009] [Accepted: 12/22/2009] [Indexed: 05/18/2023]
Abstract
Remobilization of inorganic phosphate (P(i)) within a plant is critical for sustaining growth and seed production under external P(i) fluctuation. The barley (Hordeum vulgare) transporter HvPHT1;6 has been implicated in P(i) remobilization. In this report, we expressed HvPHT1;6 in Xenopus laevis oocytes, allowing detailed characterization of voltage-dependent fluxes and currents induced by HvPHT1;6. HvPHT1;6 increased efflux of P(i) near oocyte resting membrane potentials, dependent on external P(i) concentration. Time-dependent inward currents were observed when membrane potentials were more negative than -160 mV, which was consistent with nH(+):HPO(4)(2-) (n > 2) cotransport, based on simultaneous radiotracer and oocyte voltage clamping, dependent upon P(i) concentration gradient and pH. Time- and voltage-dependent inward currents through HvPHT1;6 were also observed for SO(4)(2-)and to a lesser degree for NO(3)(-)Cl(-)but not for malate. Inward and outward currents showed linear dependence on the concentration of external HPO(4)(2-)similar to low-affinity P(i) transport in plant studies. The electrophysiological properties of HvPHT1;6, which locates to the plasma membrane when expressed in onion (Allium cepa) epidermal cells, are consistent with its suggested role in the remobilization of P(i) in barley plants.
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Affiliation(s)
| | | | | | - Stephen D. Tyerman
- Australian Centre for Plant Functional Genomics, Glen Osmond, South Australia 5064, Australia (C.P.P., C.Y.H.); and School of Agriculture, Food, and Wine, University of Adelaide, Glen Osmond, South Australia 5064, Australia (C.P.P., C.Y.H., M.G., S.D.T.)
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38
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Liu Z. Roles of vertebrate aquaglyceroporins in arsenic transport and detoxification. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2010; 679:71-81. [PMID: 20666225 DOI: 10.1007/978-1-4419-6315-4_6] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Aquaporins are important channel proteins that are responsible for the balance of cellular osmolarity and nutrient transport in vertebrates. Recently, new functions of these ancient channels have been found in the conduction of metalloid arsenic (As). Chronic As exposure through contaminated water and food sources is associated with multiple human diseases and endangers millions of people's health worldwide. Therefore, identification of the As transport pathways is necessary to elucidate the mechanisms of As carcinogenesis. Arsenic detoxification systems have been studied in multiple vertebrates such as mammalian mouse, rat, humans and nonmammalian vertebrates. Multiple transporters and enzymes have been shown to be involved in As translocation and cellular transformation. In these vertebrates, members ofaquaglyceroporins, which include AQP7 in kidney and AQP9 in liver, catalyze uptake of inorganic trivalent arsenite [As(III)]. AQP9, the major liver aquaglyceroporin, conducts both inorganic As(III) and organic monomethylarsonous acid [MMA(III)], an intermediate that is generated during the cellular methylation. As a channel that facilitates a downhill movement of substances dependent on the concentration gradient, AQP9 may play an important role in the simultaneous influx of inorganic As(III) from blood to liver and efflux of As metabolite MMA(III) from liver to blood. In this chapter, we will discuss the function ofaquaglyceroporins ofvertebrates in uptake and detoxification of the metalloid As.
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Affiliation(s)
- Zijuan Liu
- Department of Biological Sciences, Oakland University, 2200 N. Squirrel Rd, Rochester, Michigan 48309, USA.
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39
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Boscari A, Clément M, Volkov V, Golldack D, Hybiak J, Miller AJ, Amtmann A, Fricke W. Potassium channels in barley: cloning, functional characterization and expression analyses in relation to leaf growth and development. PLANT, CELL & ENVIRONMENT 2009; 32:1761-77. [PMID: 19682291 DOI: 10.1111/j.1365-3040.2009.02033.x] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/19/2023]
Abstract
It is not known how the uptake and retention of the key osmolyte K(+) in cells are mediated in growing leaf tissue. In the present study on the growing leaf 3 of barley, we have cloned the full-length coding sequence of three genes which encode putative K(+) channels (HvAKT1, HvAKT2, HvKCO1/HvTPK1), and of one gene which encodes a putative K(+) transporter (HvHAK4). The functionality of the gene products of HvAKT1 and HvAKT2 was tested through expression in Xenopus laevis oocytes. Both are inward-rectifying K(+) channels which are inhibited by Cs(+). Function of HvAKT1 in oocytes requires co-expression of a calcineurin-interacting protein kinase (AtCIPK23) and a calcineurin B-like protein (AtCBL9) from Arabidopsis, showing cross-species complementation of function. In planta, HvAKT1 is expressed primarily in roots, but is also expressed in leaf tissue. HvAKT2 is expressed particularly in leaf tissue, and HvHAK4 is expressed particularly in growing leaf tissue. Within leaves, HvAKT1 and HvAKT2 are expressed predominantly in mesophyll. Expression of genes changes little in response to low external K(+) or salinity, despite major changes in K(+) concentrations and osmolality of cells. Possible contributions of HvAKT1, HvAKT2, HvKCO1 and HvHAK4 to regulation of K(+) relations of growing barley leaf cells are discussed.
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Affiliation(s)
- Alexandre Boscari
- Division of Biological Sciences, University of Paisley, Paisley PA1 2BE, UK
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Hossain SJ, Aoshima H, Koda H, Kiso Y. Review of Functional Studies of Beverage Components Acting on the Recombinant GABAANeuroreceptor, and Na+/Glucose Cotransporter-Response Using theXenopusOocyte Expression System and Electrophysiological Measurements. FOOD BIOTECHNOL 2007. [DOI: 10.1080/08905430701534081] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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Wei W, Alexandersson E, Golldack D, Miller AJ, Kjellbom PO, Fricke W. HvPIP1;6, a barley (Hordeum vulgare L.) plasma membrane water channel particularly expressed in growing compared with non-growing leaf tissues. PLANT & CELL PHYSIOLOGY 2007; 48:1132-47. [PMID: 17602190 DOI: 10.1093/pcp/pcm083] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
The aim of the present study was to identify water channel(s) which are expressed specifically in the growth zone of grass leaves and may facilitate growth-associated water uptake into cells. Previously, a gene had been described (HvEmip) which encodes a membrane intrinsic protein (MIP) and which is particularly expressed in the base 1 cm of barley primary leaves. The functionality of the encoding protein was not known. In the present study on leaf 3 of barley (Hordeum vulgare L.), a clone was isolated, termed HvPIP1;6, which has 99% amino acid sequence identity to HvEmip and belongs to the family of plasma membrane intrinsic proteins (PIPs). Expression of HvPIP1;6 was highest in the elongation zone, where it accounted for >85% of expression of known barley PIP1s. Within the elongation zone, faster grower regions showed higher expression than slower growing regions. Expression of HvPIP1;6 was confined to the epidermis, with some expression in neighboring mesophyll cells. Expression of HvPIP1;6 in Xenopus laevis oocytes increased osmotic water permeability 4- to 6-fold. Water channel activity was inhibited by pre-incubation of oocytes with 50 microM HgCl(2) and increased following incubation with the phosphatase inhibitor okadaic acid or the plant hormone ABA. Plasma membrane preparations were analyzed by Western blots using an antibody that recognized PIP1s. Levels of PIP1s were highest in the elongation and adjacent non-elongation zone. The developmental expression profile of HvPIP2;1, the only known barley water channel belonging to the PIP2 subgroup, was opposite to that of HvPIP1;6.
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Affiliation(s)
- Wenxue Wei
- Division of Biological Sciences, University of Paisley, Paisley PA1 2BE, UK
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Nour-Eldin HH, Nørholm MHH, Halkier BA. Screening for plant transporter function by expressing a normalized Arabidopsis full-length cDNA library in Xenopus oocytes. PLANT METHODS 2006; 2:17. [PMID: 17069646 PMCID: PMC1637106 DOI: 10.1186/1746-4811-2-17] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/15/2006] [Accepted: 10/27/2006] [Indexed: 05/02/2023]
Abstract
BACKGROUND We have developed a functional genomics approach based on expression cloning in Xenopus oocytes to identify plant transporter function. We utilized the full-length cDNA databases to generate a normalized library consisting of 239 full-length Arabidopsis thaliana transporter cDNAs. The genes were arranged into a 96-well format and optimized for expression in Xenopus oocytes by cloning each coding sequence into a Xenopus expression vector. RESULTS Injection of 96 in vitro transcribed cRNAs from the library in pools of columns and rows into oocytes and subsequent screening for glucose uptake activity identified three glucose transporters. One of these, AtSTP13, had not previously been experimentally characterized. CONCLUSION Expression of the library in Xenopus oocytes, combined with uptake assays, has great potential in assignment of plant transporter function and for identifying membrane transporters for the many plant metabolites where a transporter has not yet been identified.
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Affiliation(s)
- Hussam H Nour-Eldin
- Plant Biochemistry Laboratory, Center for Molecular Plant Physiology, The Royal Veterinary and Agricultural University, Thorvaldsensvej 40, DK-1871 Frederiksberg C, Denmark
| | - Morten HH Nørholm
- Plant Biochemistry Laboratory, Center for Molecular Plant Physiology, The Royal Veterinary and Agricultural University, Thorvaldsensvej 40, DK-1871 Frederiksberg C, Denmark
| | - Barbara A Halkier
- Plant Biochemistry Laboratory, Center for Molecular Plant Physiology, The Royal Veterinary and Agricultural University, Thorvaldsensvej 40, DK-1871 Frederiksberg C, Denmark
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Kobae Y, Mizutani M, Segami S, Maeshima M. Immunochemical analysis of aquaporin isoforms in Arabidopsis suspension-cultured cells. Biosci Biotechnol Biochem 2006; 70:980-7. [PMID: 16636467 DOI: 10.1271/bbb.70.980] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Aquaporins mediate the movement of water across biomembranes. Arabidopsis thaliana contains 35 aquaporins that belong to four subfamilies (PIP, TIP, SIP, and NIP). We investigated their expression profiles immunochemically in suspension-cultured Arabidopsis thaliana cells during growth and in response to salt and osmotic stresses. Protein amounts of all aquaporins were much lower in cultured cells than in the plant tissues. This is consistent with the low water permeability of protoplasts from cultured cells. After treatment with NaCl, the protein amounts of PIP2;1, PIP2;2, and PIP2;3 in the cells increased several-fold, and those of TIP1;1 and TIP1;2, 15- and 3-fold respectively. PIP1 did not change under the stress. Cell death began after 19 d in culture, accompanied by marked accumulation of PIPs and TIPs and a gradual decrease in SIPs. Our results suggest the followings: (i) Accumulation of aquaporin isoforms was individually regulated at low levels in single cells. (ii) At least PIP2;2, PIP2;3, TIP1;1, and TIP1;2 are stress-responsive aquaporins in suspension cells. (iii) A sudden increment of several members of PIP2 and TIP1 subfamilies might be related to cell death.
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Affiliation(s)
- Yoshihiro Kobae
- Laboratory of Cell Dynamics, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, Japan
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Norholm MHH, Nour-Eldin HH, Brodersen P, Mundy J, Halkier BA. Expression of the Arabidopsis high-affinity hexose transporter STP13 correlates with programmed cell death. FEBS Lett 2006; 580:2381-7. [PMID: 16616142 DOI: 10.1016/j.febslet.2006.03.064] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2005] [Revised: 03/07/2006] [Accepted: 03/21/2006] [Indexed: 11/17/2022]
Abstract
We report the biochemical characterization in Xenopus oocytes of the Arabidopsis thaliana membrane protein, STP13, as a high affinity, hexose-specific H(+)-symporter. Studies with kinase activators suggest that it is negatively regulated by phosphorylation. STP13 promoter GFP reporter lines show GFP expression only in the vascular tissue in emerging petals under non-stressed conditions. Quantitative PCR and the pSTP13-GFP plants show induction of STP13 in programmed cell death (PCD) obtained by treatments with the fungal toxin fumonisin B1 and the pathogen Pseudomonas syringae. A role for STP13 in PCD is supported by microarray data from e.g. plants undergoing senescence and a strong correlation between STP13 transcripts and the PCD phenotype in different accelerated cell death (acd11) mutants.
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Affiliation(s)
- Morten H H Norholm
- Plant Biochemistry Laboratory, center for Molecular Plant Physiology, the royal Veterinary and Agricultural University, Fredericksberg C, Denmark
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Tokmakov AA, Terazawa Y, Ikeda M, Shirouzu M, Yokoyama S. Coupled transcription-and-translation in Xenopus oocyte and egg extracts. J Biotechnol 2006; 125:557-64. [PMID: 16647777 DOI: 10.1016/j.jbiotec.2006.03.020] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2005] [Revised: 03/10/2006] [Accepted: 03/21/2006] [Indexed: 11/16/2022]
Abstract
Coinjection of T7 promoter-driven plasmids and T7 RNA polymerase (T7 RNAP) into Xenopus oocytes results in robust protein synthesis, due to simultaneous gene transcription-and-translation (TnT) in the oocyte cytoplasm [Geib, S., Sandoz, G., Carlier, E., V. Cornet, Cheynet-Sauvion, V., De Waard, M., 2001. A novel Xenopus oocyte expression system based on cytoplasmic coinjection of T7-driven plasmids and purified T7-RNA polymerase. Receptors Channels 7, 331-343; Tokmakov, A.A., Matsumoto, E., Shirouzu, M., Yokoyama, S., 2006. Coupled cytoplasmic transcription-and-translation--a method of choice for heterologous gene experession in Xenopus oocytes. J. Biotechnol. 122, 5-15]. In the present study, we demonstrate that the TnT reaction of protein synthesis can be reconstituted in cell-free extracts of Xenopus oocytes and eggs. Similar to the reaction in oocytes, the effective coupling of bacteriophage T7 RNAP-mediated transcription with the eukaryotic translation machinery takes place in the Xenopus oocyte and egg extracts. However, the kinetics of protein and RNA production in the extracts are quite different from those observed in oocytes. Potent RNA synthesis in the extracts starts immediately after the addition of T7 promoter-driven DNA and T7 RNAP and continues for about 30 min, followed by RNA degradation. The protein product is detectable in the extracts in 15 min after the initiation of the TnT reaction. Efficient protein synthesis in the extracts continues for about 1h. The productivity of this expression system can be boosted by the additions of an RNase inhibitor and an ATP-regeneration system, and by extract dilution. Kinetic analyses suggested that extending the lifetime of the extracts would further increase their productivity.
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Tilsner J, Kassner N, Struck C, Lohaus G. Amino acid contents and transport in oilseed rape (Brassica napus L.) under different nitrogen conditions. PLANTA 2005; 221:328-38. [PMID: 15599760 DOI: 10.1007/s00425-004-1446-8] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/05/2004] [Accepted: 11/03/2004] [Indexed: 05/03/2023]
Abstract
Oilseed rape (Brassica napus L.) needs very high nitrogen fertilizer inputs. Significant amounts of this nitrogen are lost during early leaf shedding and are a source of environmental and economic concern. The objective of this study was to investigate whether the remobilization of leaf amino acids could be limiting for nitrogen use efficiency. Therefore, amino acid concentrations were analyzed in subcellular compartments of leaf mesophyll cells of plants grown under low (0.5 mM NO3-) and high (4 mM NO3-) nitrogen supply. With high nitrogen supply, young leaves showed an elevated amino acid content, mainly in vacuoles. In old leaves, however, subcellular concentrations were similar under high and low nitrogen conditions, showing that the excess nitrogen had been exported during leaf development. The phloem sap contained up to 650 mM amino acids, more than four times as much than the cytosol of mesophyll cells, indicating a very efficient phloem-loading process. Three amino acid permeases, BnAAP1, BnAAP2, and BnAAP6, were identified and characterized. BnAAP1 and BnAAP6 mediated uptake of neutral and acidic amino acids into Xenopus laevis oocytes at the actual apoplastic substrate concentrations. All three transporters were expressed in leaves and the expression was still detectable during leaf senescence, with BnAAP1 and BnAAP2 mRNA levels increasing from mature to old leaves. We conclude that phloem loading of amino acids is not limiting for nitrogen remobilization from senescing leaves in oilseed rape.
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Affiliation(s)
- Jens Tilsner
- Biochemie der Pflanze, Göttinger Zentrum für Molekulare Biowissenschaften, Universität Göttingen, Justus-von-Liebig-Weg 11, 37077, Göttingen, Germany
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Ephritikhine G, Ferro M, Rolland N. Plant membrane proteomics. PLANT PHYSIOLOGY AND BIOCHEMISTRY : PPB 2004; 42:943-62. [PMID: 15707833 DOI: 10.1016/j.plaphy.2004.11.004] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/16/2004] [Accepted: 11/09/2004] [Indexed: 05/23/2023]
Abstract
Plant membrane proteins are involved in many different functions according to their location in the cell. For instance, the chloroplast has two membrane systems, thylakoids and envelope, with specialized membrane proteins for photosynthesis and metabolite and ion transporters, respectively. Although recent advances in sample preparation and analytical techniques have been achieved for the study of membrane proteins, the characterization of these proteins, especially the hydrophobic ones, is still challenging. The present review highlights recent advances in methodologies for identification of plant membrane proteins from purified subcellular structures. The interest of combining several complementary extraction procedures to take into account specific features of membrane proteins is discussed in the light of recent proteomics data, notably for chloroplast envelope, mitochondrial membranes and plasma membrane from Arabidopsis. These examples also illustrate how, on one hand, proteomics can feed bioinformatics for a better definition of prediction tools and, on the other hand, although prediction tools are not 100% reliable, they can give valuable information for biological investigations. In particular, membrane proteomics brings new insights over plant membrane systems, on both the membrane compartment where proteins are working and their putative cellular function.
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Affiliation(s)
- Geneviève Ephritikhine
- Institut des Sciences du Végétal, CNRS (UPR 2355), Bâtiment 22, avenue de la Terrasse, 91198 Gif sur Yvette cedex, France.
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Katsuhara M, Akiyama Y, Koshio K, Shibasaka M, Kasamo K. Functional analysis of water channels in barley roots. PLANT & CELL PHYSIOLOGY 2002; 43:885-93. [PMID: 12198191 DOI: 10.1093/pcp/pcf102] [Citation(s) in RCA: 106] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
We identified three genes homologous to water channels in the plasma membrane type subfamily from roots of barley seedlings. These genes were designated HvPIP2;1, HvPIP1;3, and HvPIP1;5 after comparison to Arabidopsis aquaporins. Competitive reverse transcription (RT)-PCR was applied in order to distinguish and to quantify their transcripts. The HvPIP2;1 transcript was the most abundant among the three in roots. Salt stress (200 mM NaCl) down-regulated HvPIP2;1 (transcript and protein), but had almost no effect on the expressions of HvPIP1;3, or HvPIP1;5. Approximately equal amounts of the transcripts of the three were detected in shoots, and salt stress enhanced the expression of HvPIP2;1 but not of HvPIP1;3, or HvPIP1;5. HvPIP2;1 protein was confirmed to be localized in the plasma membrane. Functional expression of HvPIP2;1 in Xenopus oocytes confirmed that HvPIP2;1 encoded an aquaporin that transports water. This water permeability was reduced by HgCl(2), which is a typical water channel inhibitor. This activity was not modified by some inhibitors against protein kinase and protein phosphatase.
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Affiliation(s)
- Maki Katsuhara
- Research Institute for Bioresources, Okayama University, Kurashiki, 710-0046 Japan.
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Quigley F, Rosenberg JM, Shachar-Hill Y, Bohnert HJ. From genome to function: the Arabidopsis aquaporins. Genome Biol 2002; 3:RESEARCH0001. [PMID: 11806824 PMCID: PMC150448 DOI: 10.1186/gb-2001-3-1-research0001] [Citation(s) in RCA: 145] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2001] [Revised: 09/03/2001] [Accepted: 10/08/2001] [Indexed: 11/28/2022] Open
Abstract
BACKGROUND In the post-genomic era newly sequenced genomes can be used to deduce organismal functions from our knowledge of other systems. Here we apply this approach to analyzing the aquaporin gene family in Arabidopsis thaliana. The aquaporins are intrinsic membrane proteins that have been characterized as facilitators of water flux. Originally termed major intrinsic proteins (MIPs), they are now also known as water channels, glycerol facilitators and aqua-glyceroporins, yet recent data suggest that they facilitate the movement of other low-molecular-weight metabolites as well. RESULTS The Arabidopsis genome contains 38 sequences with homology to aquaporin in four subfamilies, termed PIP, TIP, NIP and SIP. We have analyzed aquaporin family structure and expression using the A. thaliana genome sequence, and introduce a new NMR approach for the purpose of analyzing water movement in plant roots in vivo. CONCLUSIONS Our preliminary data indicate a strongly transcellular component for the flux of water in roots.
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Affiliation(s)
- Francoise Quigley
- Department of Biochemistry and Molecular Biophysics, University of Arizona, Tucson, AZ 85721, USA.
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