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Sandor A, Samalova M, Brandizzi F, Kriechbaumer V, Moore I, Fricker MD, Sweetlove LJ. Characterization of intracellular membrane structures derived from a massive expansion of endoplasmic reticulum (ER) membrane due to synthetic ER-membrane-resident polyproteins. J Exp Bot 2024; 75:45-59. [PMID: 37715992 PMCID: PMC10735356 DOI: 10.1093/jxb/erad364] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/04/2023] [Accepted: 09/15/2023] [Indexed: 09/18/2023]
Abstract
The endoplasmic reticulum (ER) is a dynamic organelle that is amenable to major restructuring. Introduction of recombinant ER-membrane-resident proteins that form homo oligomers is a known method of inducing ER proliferation: interaction of the proteins with each other alters the local structure of the ER network, leading to the formation large aggregations of expanded ER, sometimes leading to the formation of organized smooth endoplasmic reticulum (OSER). However, these membrane structures formed by ER proliferation are poorly characterized and this hampers their potential development for plant synthetic biology. Here, we characterize a range of ER-derived membranous compartments in tobacco and show how the nature of the polyproteins introduced into the ER membrane affect the morphology of the final compartment. We show that a cytosol-facing oligomerization domain is an essential component for compartment formation. Using fluorescence recovery after photobleaching, we demonstrate that although the compartment retains a connection to the ER, a diffusional barrier exists to both the ER and the cytosol associated with the compartment. Using quantitative image analysis, we also show that the presence of the compartment does not disrupt the rest of the ER network. Moreover, we demonstrate that it is possible to recruit a heterologous, bacterial enzyme to the compartment, and for the enzyme to accumulate to high levels. Finally, transgenic Arabidopsis constitutively expressing the compartment-forming polyproteins grew and developed normally under standard conditions.
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Affiliation(s)
- Andras Sandor
- Department of Biology, University of Oxford, South Parks Road, Oxford, UK
| | - Marketa Samalova
- Department of Experimental Biology, Masaryk University, Brno, Czech Republic
| | - Federica Brandizzi
- MSU-DOE Plant Research Laboratory, Department of Plant Biology, Michigan State University, East Lansing, Michigan, USA
| | - Verena Kriechbaumer
- Department of Biological and Medical Sciences, Oxford Brookes University, Oxford, UK
| | - Ian Moore
- Department of Biology, University of Oxford, South Parks Road, Oxford, UK
| | - Mark D Fricker
- Department of Biology, University of Oxford, South Parks Road, Oxford, UK
| | - Lee J Sweetlove
- Department of Biology, University of Oxford, South Parks Road, Oxford, UK
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2
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Samalova M, Melnikava A, Elsayad K, Peaucelle A, Gahurova E, Gumulec J, Spyroglou I, Zemlyanskaya EV, Ubogoeva EV, Balkova D, Demko M, Blavet N, Alexiou P, Benes V, Mouille G, Hejatko J. Hormone-regulated expansins: Expression, localization, and cell wall biomechanics in Arabidopsis root growth. Plant Physiol 2023; 194:209-228. [PMID: 37073485 PMCID: PMC10762514 DOI: 10.1093/plphys/kiad228] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/06/2023] [Revised: 03/24/2023] [Accepted: 03/24/2023] [Indexed: 05/03/2023]
Abstract
Expansins facilitate cell expansion by mediating pH-dependent cell wall (CW) loosening. However, the role of expansins in controlling CW biomechanical properties in specific tissues and organs remains elusive. We monitored hormonal responsiveness and spatial specificity of expression and localization of expansins predicted to be the direct targets of cytokinin signaling in Arabidopsis (Arabidopsis thaliana). We found EXPANSIN1 (EXPA1) homogenously distributed throughout the CW of columella/lateral root cap, while EXPA10 and EXPA14 localized predominantly at 3-cell boundaries in the epidermis/cortex in various root zones. EXPA15 revealed cell-type-specific combination of homogenous vs. 3-cell boundaries localization. By comparing Brillouin frequency shift and AFM-measured Young's modulus, we demonstrated Brillouin light scattering (BLS) as a tool suitable for non-invasive in vivo quantitative assessment of CW viscoelasticity. Using both BLS and AFM, we showed that EXPA1 overexpression upregulated CW stiffness in the root transition zone (TZ). The dexamethasone-controlled EXPA1 overexpression induced fast changes in the transcription of numerous CW-associated genes, including several EXPAs and XYLOGLUCAN:XYLOGLUCOSYL TRANSFERASEs (XTHs), and associated with rapid pectin methylesterification determined by in situ Fourier-transform infrared spectroscopy in the root TZ. The EXPA1-induced CW remodeling is associated with the shortening of the root apical meristem, leading to root growth arrest. Based on our results, we propose that expansins control root growth by a delicate orchestration of CW biomechanical properties, possibly regulating both CW loosening and CW remodeling.
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Affiliation(s)
- Marketa Samalova
- CEITEC – Central European Institute of Technology, Masaryk University, Brno 625 00, Czech Republic
- Department of Experimental Biology, Faculty of Science, Masaryk University, Brno 625 00, Czech Republic
| | - Alesia Melnikava
- CEITEC – Central European Institute of Technology, Masaryk University, Brno 625 00, Czech Republic
- National Centre for Biomolecular Research, Faculty of Science, Masaryk University, Brno 625 00, Czech Republic
| | - Kareem Elsayad
- Division of Anatomy, Centre for Anatomy & Cell Biology, Medical University of Vienna, Vienna 1090, Austria
| | | | - Evelina Gahurova
- CEITEC – Central European Institute of Technology, Masaryk University, Brno 625 00, Czech Republic
- National Centre for Biomolecular Research, Faculty of Science, Masaryk University, Brno 625 00, Czech Republic
| | - Jaromir Gumulec
- Department of Pathological Physiology, Faculty of Medicine, Masaryk University, Brno 625 00, Czech Republic
| | - Ioannis Spyroglou
- CEITEC – Central European Institute of Technology, Masaryk University, Brno 625 00, Czech Republic
| | - Elena V Zemlyanskaya
- Department of Natural Sciences, Novosibirsk State University, Novosibirsk 630073, Russia
- Institute of Cytology and Genetics, Siberian Branch of Russian Academy of Sciences, Novosibirsk 630090, Russia
| | - Elena V Ubogoeva
- Institute of Cytology and Genetics, Siberian Branch of Russian Academy of Sciences, Novosibirsk 630090, Russia
| | - Darina Balkova
- CEITEC – Central European Institute of Technology, Masaryk University, Brno 625 00, Czech Republic
- Department of Experimental Biology, Faculty of Science, Masaryk University, Brno 625 00, Czech Republic
| | - Martin Demko
- CEITEC – Central European Institute of Technology, Masaryk University, Brno 625 00, Czech Republic
| | - Nicolas Blavet
- CEITEC – Central European Institute of Technology, Masaryk University, Brno 625 00, Czech Republic
| | - Panagiotis Alexiou
- CEITEC – Central European Institute of Technology, Masaryk University, Brno 625 00, Czech Republic
| | - Vladimir Benes
- Genomics Core Facility, European Molecular Biology Laboratory, Heidelberg 69117, Germany
| | | | - Jan Hejatko
- CEITEC – Central European Institute of Technology, Masaryk University, Brno 625 00, Czech Republic
- National Centre for Biomolecular Research, Faculty of Science, Masaryk University, Brno 625 00, Czech Republic
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3
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Samalova M, Flamant P, Beau R, Bromley M, Moya-Nilges M, Fontaine T, Latgé JP, Mouyna I. The New GPI-Anchored Protein, SwgA, Is Involved in Nitrogen Metabolism in the Pathogenic Filamentous Fungus Aspergillus fumigatus. J Fungi (Basel) 2023; 9:256. [PMID: 36836370 PMCID: PMC9960506 DOI: 10.3390/jof9020256] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2023] [Revised: 02/09/2023] [Accepted: 02/10/2023] [Indexed: 02/17/2023] Open
Abstract
GPI-anchored proteins display very diverse biological (biochemical and immunological) functions. An in silico analysis has revealed that the genome of Aspergillus fumigatus contains 86 genes coding for putative GPI-anchored proteins (GPI-APs). Past research has demonstrated the involvement of GPI-APs in cell wall remodeling, virulence, and adhesion. We analyzed a new GPI-anchored protein called SwgA. We showed that this protein is mainly present in the Clavati of Aspergillus and is absent from yeasts and other molds. The protein, localized in the membrane of A. fumigatus, is involved in germination, growth, and morphogenesis, and is associated with nitrogen metabolism and thermosensitivity. swgA is controlled by the nitrogen regulator AreA. This current study indicates that GPI-APs have more general functions in fungal metabolism than cell wall biosynthesis.
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Affiliation(s)
- Marketa Samalova
- Unité des Aspergillus, Département de Mycologie Institut Pasteur, 25-28 rue du Docteur Roux, CEDEX 15, 75724 Paris, France
| | - Patricia Flamant
- Unité des Aspergillus, Département de Mycologie Institut Pasteur, 25-28 rue du Docteur Roux, CEDEX 15, 75724 Paris, France
| | - Rémi Beau
- Unité des Aspergillus, Département de Mycologie Institut Pasteur, 25-28 rue du Docteur Roux, CEDEX 15, 75724 Paris, France
| | - Mike Bromley
- Manchester Fungal Infection Group, Division of Infection, Immunity and Respiratory Medicine, Faculty of Biology, Medicine and Health, University of Manchester, CTF Building, Grafton Street, Manchester M13 9NT, UK
| | - Maryse Moya-Nilges
- Unité Technologie et Service Bioimagerie Ultrastructurale (UTechS UBI), Institut Pasteur, 28 rue du Docteur Roux, 75015 Paris, France
| | - Thierry Fontaine
- Unité des Aspergillus, Département de Mycologie Institut Pasteur, 25-28 rue du Docteur Roux, CEDEX 15, 75724 Paris, France
| | - Jean-Paul Latgé
- Unité des Aspergillus, Département de Mycologie Institut Pasteur, 25-28 rue du Docteur Roux, CEDEX 15, 75724 Paris, France
| | - Isabelle Mouyna
- Unité des Aspergillus, Département de Mycologie Institut Pasteur, 25-28 rue du Docteur Roux, CEDEX 15, 75724 Paris, France
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4
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Samalova M, Gahurova E, Hejatko J. Expansin-mediated developmental and adaptive responses: A matter of cell wall biomechanics? Quant Plant Biol 2022; 3:e11. [PMID: 37077967 PMCID: PMC10095946 DOI: 10.1017/qpb.2022.6] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/30/2021] [Revised: 03/16/2022] [Accepted: 03/29/2022] [Indexed: 05/03/2023]
Abstract
Biomechanical properties of the cell wall (CW) are important for many developmental and adaptive responses in plants. Expansins were shown to mediate pH-dependent CW enlargement via a process called CW loosening. Here, we provide a brief overview of expansin occurrence in plant and non-plant species, their structure and mode of action including the role of hormone-regulated CW acidification in the control of expansin activity. We depict the historical as well as recent CW models, discuss the role of expansins in the CW biomechanics and address the developmental importance of expansin-regulated CW loosening in cell elongation and new primordia formation. We summarise the data published so far on the role of expansins in the abiotic stress response as well as the rather scarce evidence and hypotheses on the possible mechanisms underlying expansin-mediated abiotic stress resistance. Finally, we wrap it up by highlighting possible future directions in expansin research.
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Affiliation(s)
- Marketa Samalova
- CEITEC - Central European Institute of Technology, Masaryk University, Brno, Czech Republic
- Department of Experimental Biology, Faculty of Science, Masaryk University, Brno, Czech Republic
| | - Evelina Gahurova
- CEITEC - Central European Institute of Technology, Masaryk University, Brno, Czech Republic
- National Centre for Biotechnological Research, Faculty of Science, Masaryk University, Brno, Czech Republic
| | - Jan Hejatko
- CEITEC - Central European Institute of Technology, Masaryk University, Brno, Czech Republic
- National Centre for Biotechnological Research, Faculty of Science, Masaryk University, Brno, Czech Republic
- Author for correspondence: J. Hejatko, E-mail:
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5
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Samalova M, Moore I. The steroid-inducible pOp6/LhGR gene expression system is fast, sensitive and does not cause plant growth defects in rice (Oryza sativa). BMC Plant Biol 2021; 21:461. [PMID: 34627147 PMCID: PMC8501728 DOI: 10.1186/s12870-021-03241-w] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/01/2021] [Accepted: 09/28/2021] [Indexed: 06/13/2023]
Abstract
Inducible systems for transgene expression activated by a chemical inducer or an inducer of non-plant origin are desirable tools for both basic plant research and biotechnology. Although, the technology has been widely exploited in dicotyledonous model plants such as Arabidopsis, it has not been optimised for use with the monocotyledonous model species, namely rice. We have adapted the dexamethasone-inducible pOp6/LhGR system for rice and the results indicated that it is fast, sensitive and tightly regulated, with high levels of induction that remain stable over several generations. Most importantly, we have shown that the system does not cause negative growth defects in vitro or in soil grown plants. Interestingly in the process of testing, we found that another steroid, triamcinolone acetonide, is a more potent inducer in rice than dexamethasone. We present serious considerations for the construct design to avoid undesirable effects caused by the system in plants, leakiness and possible silencing, as well as simple steps to maximize translation efficiency of a gene of interest. Finally, we compare the performance of the pOp6/LhGR system with other chemically inducible systems tested in rice in terms of the properties of an ideal inducible system.
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Affiliation(s)
- Marketa Samalova
- Department of Experimental Biology, Masaryk University, Brno, Czech Republic.
| | - Ian Moore
- Department of Plant Sciences, Oxford University, Oxford, UK
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6
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Samalova M, Kirchhelle C, Moore I. Universal Methods for Transgene Induction Using the Dexamethasone-Inducible Transcription Activation System pOp6/LhGR in Arabidopsis and Other Plant Species. ACTA ACUST UNITED AC 2019; 4:e20089. [PMID: 30860661 DOI: 10.1002/cppb.20089] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Use of chemically inducible systems for transgene expression is a crucial requirement for modern plant biology research, as it allows (1) expression of transgenes that compromise plant viability or fertility when constitutively expressed and (2) spatiotemporal control of transgene expression levels. We describe the stringently regulated and highly responsive dexamethasone-inducible gene expression system pOp6/LhGR, which comprises the chimeric transcription activator LhGR and the corresponding pOp6 promoter. Upon induction, the LhGR activator binds to the pOp6 promoter and induces expression of the target gene of interest. We provide detailed protocols for inducing transgene expression at different developmental stages and in different plant species and discuss dexamethasone stability and use of its analogs. We also introduce new, versatile, GATEWAY-compatible binary vectors that are now available for the pOp6/LhGR system. © 2019 by John Wiley & Sons, Inc.
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Affiliation(s)
| | | | - Ian Moore
- Department of Plant Sciences, University of Oxford, Oxford, United Kingdom
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7
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Samalova M, Mélida H, Vilaplana F, Bulone V, Soanes DM, Talbot NJ, Gurr SJ. The β-1,3-glucanosyltransferases (Gels) affect the structure of the rice blast fungal cell wall during appressorium-mediated plant infection. Cell Microbiol 2016; 19. [PMID: 27568483 PMCID: PMC5396357 DOI: 10.1111/cmi.12659] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2016] [Revised: 08/23/2016] [Accepted: 08/24/2016] [Indexed: 12/02/2022]
Abstract
The fungal wall is pivotal for cell shape and function, and in interfacial protection during host infection and environmental challenge. Here, we provide the first description of the carbohydrate composition and structure of the cell wall of the rice blast fungus Magnaporthe oryzae. We focus on the family of glucan elongation proteins (Gels) and characterize five putative β‐1,3‐glucan glucanosyltransferases that each carry the Glycoside Hydrolase 72 signature. We generated targeted deletion mutants of all Gel isoforms, that is, the GH72+, which carry a putative carbohydrate‐binding module, and the GH72− Gels, without this motif. We reveal that M. oryzaeGH72+GELs are expressed in spores and during both infective and vegetative growth, but each individual Gel enzymes are dispensable for pathogenicity. Further, we demonstrated that a Δgel1Δgel3Δgel4 null mutant has a modified cell wall in which 1,3‐glucans have a higher degree of polymerization and are less branched than the wild‐type strain. The mutant showed significant differences in global patterns of gene expression, a hyper‐branching phenotype and no sporulation, and thus was unable to cause rice blast lesions (except via wounded tissues). We conclude that Gel proteins play significant roles in structural modification of the fungal cell wall during appressorium‐mediated plant infection.
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Affiliation(s)
| | - Hugo Mélida
- Division of Glycoscience, School of Biotechnology, Royal Institute of Technology (KTH), Stockholm, Sweden.,Centre for Plant Biotechnology and Genomics, Universidad Politécnica de Madrid, Madrid, Spain
| | - Francisco Vilaplana
- Division of Glycoscience, School of Biotechnology, Royal Institute of Technology (KTH), Stockholm, Sweden
| | - Vincent Bulone
- Division of Glycoscience, School of Biotechnology, Royal Institute of Technology (KTH), Stockholm, Sweden.,ARC Centre of Excellence in Plant Cell Walls and School of Agriculture, Food and Wine, University of Adelaide, Urrbrae, South Australia, Australia
| | - Darren M Soanes
- School of Biosciences, College of Life and Environmental Sciences, University of Exeter, Exeter, UK
| | - Nicholas J Talbot
- School of Biosciences, College of Life and Environmental Sciences, University of Exeter, Exeter, UK
| | - Sarah J Gurr
- Department of Plant Sciences, University of Oxford, Oxford, UK.,School of Biosciences, College of Life and Environmental Sciences, University of Exeter, Exeter, UK
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8
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Samalova M, Meyer AJ, Gurr SJ, Fricker MD. Robust anti-oxidant defences in the rice blast fungus Magnaporthe oryzae confer tolerance to the host oxidative burst. New Phytol 2014; 201:556-573. [PMID: 24117971 DOI: 10.1111/nph.12530] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/07/2013] [Accepted: 08/20/2013] [Indexed: 05/22/2023]
Abstract
Plants respond to pathogen attack via a rapid burst of reactive oxygen species (ROS). However, ROS are also produced by fungal metabolism and are required for the development of infection structures in Magnaporthe oryzae. To obtain a better understanding of redox regulation in M. oryzae, we measured the amount and redox potential of glutathione (E(GSH)), as the major cytoplasmic anti-oxidant, the rates of ROS production, and mitochondrial activity using multi-channel four-dimensional (x,y,z,t) confocal imaging of Grx1-roGFP2 and fluorescent reporters during spore germination, appressorium formation and infection. High levels of mitochondrial activity and ROS were localized to the growing germ tube and appressorium, but E(GSH) was highly reduced and tightly regulated during development. Furthermore, germlings were extremely resistant to external H2O2 exposure ex planta. EGSH remained highly reduced during successful infection of the susceptible rice cultivar CO39. By contrast, there was a dramatic reduction in the infection of resistant (IR68) rice, but the sparse hyphae that did form also maintained a similar reduced E(GSH). We conclude that M. oryzae has a robust anti-oxidant defence system and maintains tight control of EGSH despite substantial oxidative challenge. Furthermore, the magnitude of the host oxidative burst alone does not stress the pathogen sufficiently to prevent infection in this pathosystem.
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Affiliation(s)
- Marketa Samalova
- Department of Plant Sciences, University of Oxford, South Parks Road, Oxford, OX1 3RB, UK
| | - Andreas J Meyer
- INRES, Universität Bonn, Friedrich-Ebert-Allee 144, D-53113, Bonn, Germany
| | - Sarah J Gurr
- Department of Plant Sciences, University of Oxford, South Parks Road, Oxford, OX1 3RB, UK
- Biosciences, University of Exeter, Devon, EX4 4QD, UK
| | - Mark D Fricker
- Department of Plant Sciences, University of Oxford, South Parks Road, Oxford, OX1 3RB, UK
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9
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Samalova M, Johnson J, Illes M, Kelly S, Fricker M, Gurr S. Nitric oxide generated by the rice blast fungus Magnaporthe oryzae drives plant infection. New Phytol 2013; 197:207-222. [PMID: 23072575 DOI: 10.1111/j.1469-8137.2012.04368.x] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/20/2012] [Accepted: 08/31/2012] [Indexed: 05/10/2023]
Abstract
Plant-derived nitric oxide (NO) triggers defence, priming the onset of the hypersensitive response and restricting pathogen ingress during incompatibility. However, little is known about the role of pathogen-produced NO during pre-infection development and infection. We sought evidence for NO production by the rice blast fungus during early infection. NO production was measured using fluorescence of DAR-4M and the role of NO assessed using NO scavengers. The synthesis of NO was investigated by targeted knockout of genes potentially involved in NO synthesis, including nitric oxide synthase-like genes (NOL2 and NOL3) and nitrate (NIA1) and nitrite reductase (NII1), generating single and double Δnia1Δnii1, Δnia1Δnol3, and Δnol2Δnol3 mutants. We demonstrate that Magnaporthe oryzae generates NO during germination and in early development. Removal of NO delays germling development and reduces disease lesion numbers. NO is not generated by the candidate proteins tested, nor by other arginine-dependent NO systems, by polyamine oxidase activity or non-enzymatically by low pH. Furthermore, we show that, while NIA1 and NII1 are essential for nitrate assimilation, NIA1, NII1, NOL2 and NOL3 are all dispensable for pathogenicity. Development of M. oryzae and initiation of infection are critically dependent on fungal NO synthesis, but its mode of generation remains obscure.
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Affiliation(s)
- Marketa Samalova
- Department of Plant Sciences, University of Oxford, South Parks Road, Oxford, OX1 3RB, UK
| | - Jasper Johnson
- Department of Plant Sciences, University of Oxford, South Parks Road, Oxford, OX1 3RB, UK
| | - Mary Illes
- Department of Plant Sciences, University of Oxford, South Parks Road, Oxford, OX1 3RB, UK
| | - Steven Kelly
- Department of Plant Sciences, University of Oxford, South Parks Road, Oxford, OX1 3RB, UK
| | - Mark Fricker
- Department of Plant Sciences, University of Oxford, South Parks Road, Oxford, OX1 3RB, UK
| | - Sarah Gurr
- Department of Plant Sciences, University of Oxford, South Parks Road, Oxford, OX1 3RB, UK
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10
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Pinheiro H, Samalova M, Geldner N, Chory J, Martinez A, Moore I. Genetic evidence that the higher plant Rab-D1 and Rab-D2 GTPases exhibit distinct but overlapping interactions in the early secretory pathway. J Cell Sci 2009; 122:3749-58. [PMID: 19789181 DOI: 10.1242/jcs.050625] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
GTPases of the Rab1 subclass are essential for membrane traffic between the endoplasmic reticulum (ER) and Golgi complex in animals, fungi and plants. Rab1-related proteins in higher plants are unusual because sequence comparisons divide them into two putative subclasses, Rab-D1 and Rab-D2, that are conserved in monocots and dicots. We tested the hypothesis that the Rab-D1 and Rab-D2 proteins of Arabidopsis represent functionally distinct groups. RAB-D1 and RAB-D2a each targeted fluorescent proteins to the same punctate structures associated with the Golgi stacks and trans-Golgi-network. Dominant-inhibitory N121I mutants of each protein inhibited traffic of diverse cargo proteins at the ER but they appeared to act via distinct biochemical pathways as biosynthetic traffic in cells expressing either of the N121I mutants could be restored by coexpressing the wild-type form of the same subclass but not the other subclass. The same interaction was observed in transgenic seedlings expressing RAB-D1 [N121I]. Insertional mutants confirmed that the three Arabidopsis Rab-D2 genes were extensively redundant and collectively performed an essential function that could not be provided by RAB-D1, which was non-essential. However, plants lacking RAB-D1, RAB-D2b and RAB-D2c were short and bushy with low fertility, indicating that the Rab-D1 and Rab-D2 subclasses have overlapping functions.
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Affiliation(s)
- Hazel Pinheiro
- Department of Plant Sciences, University of Oxford, South Parks Road, Oxford OX1 3RB, UK
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11
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Green M, Williamson P, Samalova M, Davis J, Brovelli S, Dobson P, Cacialli F. Synthesis of type II/type I CdTe/CdS/ZnS quantum dots and their use in cellular imaging. ACTA ACUST UNITED AC 2009. [DOI: 10.1039/b913292a] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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12
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Abstract
Fluorescent protein markers are widely used to report plant membrane traffic; however, effective protocols to quantify fluorescence or marker expression are lacking. Here the 20 residue self-cleaving 2A peptide from Foot and Mouth Disease Virus was used to construct polyproteins that expressed a trafficked marker in fixed stoichiometry with a reference protein in a different cellular compartment. Various pairs of compartments were simultaneously targeted. Together with a bespoke image analysis tool, these constructs allowed biosynthetic membrane traffic to be assayed with markedly improved sensitivity, dynamic range and statistical significance using protocols compatible with the common plant transfection and transgenic systems. As marker and effector expression could be monitored in populations or individual cells, saturation phenomena could be avoided and stochastic or epigenetic influences could be controlled. Surprisingly, mutational analysis of the ratiometric assay constructs revealed that the 2A peptide was dispensable for efficient cleavage of polyproteins carrying a single internal signal peptide, whereas the signal peptide was essential. In contrast, a construct bearing two signal peptide/anchors required 2A for efficient separation and stability, but 2A caused the amino-terminal moiety of such fusions to be mis-sorted to the vacuole. A model to account for the behaviour of 2A in these and other studies in plants is proposed.
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Affiliation(s)
- Marketa Samalova
- Department of Plant Sciences, University of Oxford, South Parks Road, Oxford OX1 3RB, UK
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13
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Abstract
Several vector systems are available for tissue-specific transactivation or chemical induction of transgene expression in plants. The choice facing researchers is which promoter system to commit to as this determines the range and characteristics of the expression resources available. The decision will not be the same for all species or applications. We present some general discussion on the use of these technologies and review in detail the properties in various (mainly angiosperm) species of the most promising: mGal4:VP16/UAS and pOp/LhG4 for transactivation, and the alc-switch, GVE/VGE, GVG, pOp6/LhGR, and XVE systems for chemical induction.
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Affiliation(s)
- Ian Moore
- Department of Plant Sciences, University of Oxford, South Parks Road, Oxford, OX1 3RB, UK.
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Craft J, Samalova M, Baroux C, Townley H, Martinez A, Jepson I, Tsiantis M, Moore I. New pOp/LhG4 vectors for stringent glucocorticoid-dependent transgene expression in Arabidopsis. Plant J 2005; 41:899-918. [PMID: 15743453 DOI: 10.1111/j.1365-313x.2005.02342.x] [Citation(s) in RCA: 144] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
To facilitate glucocorticoid-inducible transgene expression from the pOp promoter in Arabidopsis the ligand-binding domain of a rat glucocorticoid receptor (GR LBD) was fused to the amino terminus of the synthetic transcription factor LhG4 to generate LhGR-N. Fusions bearing the GR LBD at other positions in LhG4 exhibited incomplete repression or inefficient induction. LhGR-N was stringently repressed in the absence of exogenous glucocorticoid but was fully activated by addition of 2 microm dexamethasone which resulted in 1000-fold increase in GUS reporter activity. Half maximal induction was achieved with 0.2 microm dexamethasone. Reporter transcripts were detectable within 2 h of dexamethasone application and peaked 4-10 h later. Neither LhGR-N nor dexamethasone affected seedling development although ethanol retarded development when used as a solvent for dexamethasone. The efficiency of the pOp target promoter was improved 10- to 20-fold by incorporating six copies of the ideal lac operator with sufficient inter-operator spacing to allow simultaneous occupancy. Introduction of the TMV Omega sequence into the 5'UTR resulted in a further 10-fold increase in dexamethasone-inducible reporter activity and an increase in the induction factor to 10(4). Although promoters containing the TMV Omega sequence exhibited slightly increased basal expression levels in the absence of dexamethasone, stringent regulation of the cytokinin biosynthetic gene ipt was achieved with all promoters. Despite the severity of the induced ipt phenotypes, transcripts for the KNOX homoeodomain transcription factors BREVIPEDICELLUS and SHOOTMERISTEMLESS were not significantly increased within 48 h of dexamethasone application to seedlings.
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Affiliation(s)
- Judith Craft
- Department of Plant Sciences, University of Oxford, South Parks Rd, Oxford, OX1 3RB, UK
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Samalova M, Brzobohaty B, Moore I. pOp6/LhGR: a stringently regulated and highly responsive dexamethasone-inducible gene expression system for tobacco. Plant J 2005; 41:919-35. [PMID: 15743454 DOI: 10.1111/j.1365-313x.2005.02341.x] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
We describe pOp/LhGR, a dexamethasone-inducible derivative of the pOp/LhG4 transcription activation system, and its use in tobacco to regulate expression of uidA (encoding beta-glucuronidase; GUS) and the cytokinin-biosnythetic gene ipt. The pOp/LhGR system exhibited stringent regulation and strong induced phenotypes in soil and tissue culture. In conjunction with an improved target promoter, pOp6, that carries six copies of an optimized lac operator sequence the pOp6/LhGR system directed induced GUS activities that exceeded those obtained with pOp/LhG4 or the CaMV 35S promoter but without increased uninduced activity. A single dose of dexamethasone was sufficient to direct cytotoxic levels of ipt expression in soil-grown plants although uninduced plants grew normally throughout a complete life cycle. In vitro, induced transcripts were detectable within an hour of dexamethasone application and 1 nM dexamethasone was sufficient for half maximal induction of GUS activity. Various methods of dexamethasone application were successfully applied under tissue culture and greenhouse conditions. We observed no inhibitory effects of dexamethasone or LhGR on plant development even with the highest concentrations of inducer, although tobacco seedlings were adversely affected by ethanol used as a solvent for dexamethasone stock solutions. The pOp/LhGR system provides a highly sensitive, efficient, and tightly regulated chemically inducible transgene expression system for tobacco plants.
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Affiliation(s)
- Marketa Samalova
- Department of Plant Sciences, University of Oxford, South Parks Rd, Oxford OX1 3RB, UK
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