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Bobik K, Burch-Smith TM. Chloroplast signaling within, between and beyond cells. FRONTIERS IN PLANT SCIENCE 2015; 6:781. [PMID: 26500659 PMCID: PMC4593955 DOI: 10.3389/fpls.2015.00781] [Citation(s) in RCA: 129] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/31/2015] [Accepted: 09/10/2015] [Indexed: 05/18/2023]
Abstract
The most conspicuous function of plastids is the oxygenic photosynthesis of chloroplasts, yet plastids are super-factories that produce a plethora of compounds that are indispensable for proper plant physiology and development. Given their origins as free-living prokaryotes, it is not surprising that plastids possess their own genomes whose expression is essential to plastid function. This semi-autonomous character of plastids requires the existence of sophisticated regulatory mechanisms that provide reliable communication between them and other cellular compartments. Such intracellular signaling is necessary for coordinating whole-cell responses to constantly varying environmental cues and cellular metabolic needs. This is achieved by plastids acting as receivers and transmitters of specific signals that coordinate expression of the nuclear and plastid genomes according to particular needs. In this review we will consider the so-called retrograde signaling occurring between plastids and nuclei, and between plastids and other organelles. Another important role of the plastid we will discuss is the involvement of plastid signaling in biotic and abiotic stress that, in addition to influencing retrograde signaling, has direct effects on several cellular compartments including the cell wall. We will also review recent evidence pointing to an intriguing function of chloroplasts in regulating intercellular symplasmic transport. Finally, we consider an intriguing yet less widely known aspect of plant biology, chloroplast signaling from the perspective of the entire plant. Thus, accumulating evidence highlights that chloroplasts, with their complex signaling pathways, provide a mechanism for exquisite regulation of plant development, metabolism and responses to the environment. As chloroplast processes are targeted for engineering for improved productivity the effect of such modifications on chloroplast signaling will have to be carefully considered in order to avoid unintended consequences on plant growth and development.
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Affiliation(s)
| | - Tessa M. Burch-Smith
- *Correspondence: Tessa M. Burch-Smith, Department of Biochemistry, Cellular and Molecular Biology, University of Tennessee, 1414 Cumberland Avenue, M407 Walters Life Science, Knoxville, TN 37932, USA,
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Schattat MH, Barton KA, Mathur J. The myth of interconnected plastids and related phenomena. PROTOPLASMA 2015; 252:359-71. [PMID: 24965372 DOI: 10.1007/s00709-014-0666-4] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/10/2014] [Accepted: 06/12/2014] [Indexed: 05/08/2023]
Abstract
Studies spread over nearly two and a half centuries have identified the primary plastid in autotrophic algae and plants as a pleomorphic, multifunctional organelle comprising of a double-membrane envelope enclosing an organization of internal membranes submerged in a watery stroma. All plastid units have been observed extending and retracting thin stroma-filled tubules named stromules sporadically. Observations on living plant cells often convey the impression that stromules connect two or more independent plastids with each other. When photo-bleaching techniques were used to suggest that macromolecules such as the green fluorescent protein could flow between already interconnected plastids, for many people this impression changed to conviction. However, it was noticed only recently that the concept of protein flow between plastids rests solely on the words "interconnected plastids" for which details have never been provided. We have critically reviewed botanical literature dating back to the 1880s for understanding this term and the phenomena that have become associated with it. We find that while meticulously detailed ontogenic studies spanning nearly 150 years have established the plastid as a singular unit organelle, there is no experimental support for the idea that interconnected plastids exist under normal conditions of growth and development. In this review, while we consider several possibilities that might allow a single elongated plastid to be misinterpreted as two or more interconnected plastids, our final conclusion is that the concept of direct protein flow between plastids is based on an unfounded assumption.
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Affiliation(s)
- Martin H Schattat
- Martin-Luther-Universität Halle-Wittenberg Pflanzenphysiologie, Weinbergweg 10, 06120, Halle (Saale), Germany,
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Liu L, Chung HY, Lacatus G, Baliji S, Ruan J, Sunter G. Altered expression of Arabidopsis genes in response to a multifunctional geminivirus pathogenicity protein. BMC PLANT BIOLOGY 2014; 14:302. [PMID: 25403083 PMCID: PMC4253603 DOI: 10.1186/s12870-014-0302-7] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/01/2014] [Accepted: 10/23/2014] [Indexed: 05/11/2023]
Abstract
BACKGROUND Geminivirus AC2 is a multifunctional protein that acts as a pathogenicity factor. Transcriptional regulation by AC2 appears to be mediated through interaction with a plant specific DNA binding protein, PEAPOD2 (PPD2), that specifically binds to sequences known to mediate activation of the CP promoter of Cabbage leaf curl virus (CaLCuV) and Tomato golden mosaic virus (TGMV). Suppression of both basal and innate immune responses by AC2 in plants is mediated through inactivation of SnRK1.2, an Arabidopsis SNF1 related protein kinase, and adenosine kinase (ADK). An indirect promoter targeting strategy, via AC2-host dsDNA binding protein interactions, and inactivation of SnRK1.2-mediated defense responses could provide the opportunity for geminiviruses to alter host gene expression and in turn, reprogram the host to support virus infection. The goal of this study was to identify changes in the transcriptome of Arabidopsis induced by the transcription activation function of AC2 and the inactivation of SnRK1.2. RESULTS Using full-length and truncated AC2 proteins, microarray analyses identified 834 genes differentially expressed in response to the transcriptional regulatory function of the AC2 protein at one and two days post treatment. We also identified 499 genes differentially expressed in response to inactivation of SnRK1.2 by the AC2 protein at one and two days post treatment. Network analysis of these two sets of differentially regulated genes identified several networks consisting of between four and eight highly connected genes. Quantitative real-time PCR analysis validated the microarray expression results for 10 out of 11 genes tested. CONCLUSIONS It is becoming increasingly apparent that geminiviruses manipulate the host in several ways to facilitate an environment conducive to infection, predominantly through the use of multifunctional proteins. Our approach of identifying networks of highly connected genes that are potentially co-regulated by geminiviruses during infection will allow us to identify novel pathways of co-regulated genes that are stimulated in response to pathogen infection in general, and virus infection in particular.
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Affiliation(s)
- Lu Liu
- />Department of Computer Science, The University of Texas at San Antonio, One UTSA Circle, San Antonio, TX USA
| | - Ho Yong Chung
- />Department of Biology, The University of Texas at San Antonio, One UTSA Circle, San Antonio, TX USA
| | - Gabriela Lacatus
- />Current address: Scripps Health/Hematology/Oncology Division, 15004 Innovation Drive, San Diego, CA 92128 USA
| | - Surendranath Baliji
- />Current address: Bayer CropScience Vegetable Seeds, 7087 East Peltier Road, Acampo, California 95220 USA
| | - Jianhua Ruan
- />Department of Computer Science, The University of Texas at San Antonio, One UTSA Circle, San Antonio, TX USA
| | - Garry Sunter
- />Department of Biology, The University of Texas at San Antonio, One UTSA Circle, San Antonio, TX USA
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Erickson JL, Ziegler J, Guevara D, Abel S, Klösgen RB, Mathur J, Rothstein SJ, Schattat MH. Agrobacterium-derived cytokinin influences plastid morphology and starch accumulation in Nicotiana benthamiana during transient assays. BMC PLANT BIOLOGY 2014; 14:127. [PMID: 24886417 PMCID: PMC4062310 DOI: 10.1186/1471-2229-14-127] [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] [Received: 11/26/2013] [Accepted: 04/24/2014] [Indexed: 05/06/2023]
Abstract
BACKGROUND Agrobacterium tumefaciens-based transient assays have become a common tool for answering questions related to protein localization and gene expression in a cellular context. The use of these assays assumes that the transiently transformed cells are observed under relatively authentic physiological conditions and maintain 'normal' sub-cellular behaviour. Although this premise is widely accepted, the question of whether cellular organization and organelle morphology is altered in Agrobacterium-infiltrated cells has not been examined in detail. The first indications of an altered sub-cellular environment came from our observation that a common laboratory strain, GV3101(pMP90), caused a drastic increase in stromule frequency. Stromules, or 'stroma-filled-tubules' emanate from the surface of plastids and are sensitive to a variety of biotic and abiotic stresses. Starting from this observation, the goal of our experiments was to further characterize the changes to the cell resulting from short-term bacterial infestation, and to identify the factor responsible for eliciting these changes. RESULTS Using a protocol typical of transient assays we evaluated the impact of GV3101(pMP90) infiltration on chloroplast behaviour and morphology in Nicotiana benthamiana. Our experiments confirmed that GV3101(pMP90) consistently induces stromules and alters plastid position relative to the nucleus. These effects were found to be the result of strain-dependant secretion of cytokinin and its accumulation in the plant tissue. Bacterial production of the hormone was found to be dependant on the presence of a trans-zeatin synthase gene (tzs) located on the Ti plasmid of GV3101(pMP90). Bacteria-derived cytokinins were also correlated with changes to both soluble sugar level and starch accumulation. CONCLUSION Although we have chosen to focus on how transient Agrobacterium infestation alters plastid based parameters, these changes to the morphology and position of a single organelle, combined with the measured increases in sugar and starch content, suggest global changes to cell physiology. This indicates that cells visualized during transient assays may not be as 'normal' as was previously assumed. Our results suggest that the impact of the bacteria can be minimized by choosing Agrobacterium strains devoid of the tzs gene, but that the alterations to sub-cellular organization and cell carbohydrate status cannot be completely avoided using this strategy.
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Affiliation(s)
- Jessica L Erickson
- Abteilung Pflanzen Physiologie, Institut für Biologie-Pflanzenphysiologie, Martin-Luther-Universität Halle-Wittenberg, Weinbergweg 10, Halle/Saale 06120, Germany
| | - Jörg Ziegler
- Abteilung Molekulare Signalverarbeitung, Leibniz-Institut für Pflanzenbiochemie, Weinberg 3, Halle/Saale 06120, Germany
| | - David Guevara
- Present Address: Pioneer Hi-Bred, 12111 Mississauga Rd, Georgetown, ON L7G 4S7, Canada
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON N1G 2 W1, Canada
| | - Steffen Abel
- Abteilung Molekulare Signalverarbeitung, Leibniz-Institut für Pflanzenbiochemie, Weinberg 3, Halle/Saale 06120, Germany
| | - Ralf B Klösgen
- Abteilung Pflanzen Physiologie, Institut für Biologie-Pflanzenphysiologie, Martin-Luther-Universität Halle-Wittenberg, Weinbergweg 10, Halle/Saale 06120, Germany
| | - Jaideep Mathur
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON N1G 2 W1, Canada
| | - Steven J Rothstein
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON N1G 2 W1, Canada
| | - Martin H Schattat
- Abteilung Pflanzen Physiologie, Institut für Biologie-Pflanzenphysiologie, Martin-Luther-Universität Halle-Wittenberg, Weinbergweg 10, Halle/Saale 06120, Germany
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON N1G 2 W1, Canada
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Abstract
Plastid division is fundamental to the biology of plant cells. Division by binary fission entails the coordinated assembly and constriction of four concentric rings, two internal and two external to the organelle. The internal FtsZ ring and external dynamin-like ARC5/DRP5B ring are connected across the two envelopes by the membrane proteins ARC6, PARC6, PDV1, and PDV2. Assembly-stimulated GTPase activity drives constriction of the FtsZ and ARC5/DRP5B rings, which together with the plastid-dividing rings pull and squeeze the envelope membranes until the two daughter plastids are formed, with the final separation requiring additional proteins. The positioning of the division machinery is controlled by the chloroplast Min system, which confines FtsZ-ring formation to the plastid midpoint. The dynamic morphology of plastids, especially nongreen plastids, is also considered here, particularly in relation to the production of stromules and plastid-derived vesicles and their possible roles in cellular communication and plastid functionality.
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Hanley-Bowdoin L, Bejarano ER, Robertson D, Mansoor S. Geminiviruses: masters at redirecting and reprogramming plant processes. Nat Rev Microbiol 2013; 11:777-88. [DOI: 10.1038/nrmicro3117] [Citation(s) in RCA: 484] [Impact Index Per Article: 44.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
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Wang W, Zhang Y, Wen Y, Berkey R, Ma X, Pan Z, Bendigeri D, King H, Zhang Q, Xiao S. A comprehensive mutational analysis of the Arabidopsis resistance protein RPW8.2 reveals key amino acids for defense activation and protein targeting. THE PLANT CELL 2013; 25:4242-61. [PMID: 24151293 PMCID: PMC3877822 DOI: 10.1105/tpc.113.117226] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/07/2013] [Revised: 09/15/2013] [Accepted: 09/24/2013] [Indexed: 05/18/2023]
Abstract
The Arabidopsis thaliana resistance to powdery mildew8.2 (RPW8.2) protein is specifically targeted to the extrahaustorial membrane (EHM) encasing the haustorium, or fungal feeding structure, where RPW8.2 activates broad-spectrum resistance against powdery mildew pathogens. How RPW8.2 activates defenses at a precise subcellular locale is not known. Here, we report a comprehensive mutational analysis in which more than 100 RPW8.2 mutants were functionally evaluated for their defense and trafficking properties. We show that three amino acid residues (i.e., threonine-64, valine-68, and aspartic acid-116) are critical for RPW8.2-mediated cell death and resistance to powdery mildew (Golovinomyces cichoracearum UCSC1). Also, we reveal that two arginine (R)- or lysine (K)-enriched short motifs (i.e., R/K-R/K-x-R/K) make up the likely core EHM-targeting signals, which, together with the N-terminal transmembrane domain, define a minimal sequence of 60 amino acids that is necessary and sufficient for EHM localization. In addition, some RPW8.2 mutants localize to the nucleus and/or to a potentially novel membrane that wraps around plastids or plastid-derived stromules. Results from this study not only reveal critical amino acid elements in RPW8.2 that enable haustorium-targeted trafficking and defense, but also provide evidence for the existence of a specific, EHM-oriented membrane trafficking pathway in leaf epidermal cells invaded by powdery mildew.
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Affiliation(s)
- Wenming Wang
- Rice Research Institute, Sichuan Agricultural University, Chengdu 611130, China
- Institute for Bioscience and Biotechnology Research, University of Maryland, Rockville, Maryland 20850
| | - Yi Zhang
- Institute for Bioscience and Biotechnology Research, University of Maryland, Rockville, Maryland 20850
| | - Yingqiang Wen
- Institute for Bioscience and Biotechnology Research, University of Maryland, Rockville, Maryland 20850
- State Key Laboratory of Crop Stress Biology for Arid Areas and College of Horticulture, Northwest A&F University, Yangling, Shaanxi 712100, China
| | - Robert Berkey
- Institute for Bioscience and Biotechnology Research, University of Maryland, Rockville, Maryland 20850
| | - Xianfeng Ma
- Rice Research Institute, Sichuan Agricultural University, Chengdu 611130, China
- Institute for Bioscience and Biotechnology Research, University of Maryland, Rockville, Maryland 20850
| | - Zhiyong Pan
- Institute for Bioscience and Biotechnology Research, University of Maryland, Rockville, Maryland 20850
- National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, Wuhan 430070, China
| | - Dipti Bendigeri
- Institute for Bioscience and Biotechnology Research, University of Maryland, Rockville, Maryland 20850
| | - Harlan King
- Institute for Bioscience and Biotechnology Research, University of Maryland, Rockville, Maryland 20850
| | - Qiong Zhang
- Institute for Bioscience and Biotechnology Research, University of Maryland, Rockville, Maryland 20850
| | - Shunyuan Xiao
- Institute for Bioscience and Biotechnology Research, University of Maryland, Rockville, Maryland 20850
- Department of Plant Science and Landscape Architecture, University of Maryland, College Park, Maryland 20742
- Address correspondence to
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Abstract
Geminiviruses are a family of plant viruses that cause economically important plant diseases worldwide. These viruses have circular single-stranded DNA genomes and four to eight genes that are expressed from both strands of the double-stranded DNA replicative intermediate. The transcription of these genes occurs under the control of two bidirectional promoters and one monodirectional promoter. The viral proteins function to facilitate virus replication, virus movement, the assembly of virus-specific nucleoprotein particles, vector transmission and to counteract plant host defence responses. Recent research findings have provided new insights into the structure and function of these proteins and have identified numerous host interacting partners. Most of the viral proteins have been shown to be multifunctional, participating in multiple events during the infection cycle and have, indeed, evolved coordinated interactions with host proteins to ensure a successful infection. Here, an up-to-date review of viral protein structure and function is presented, and some areas requiring further research are identified.
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Affiliation(s)
- Vincent N Fondong
- Department of Biological Sciences, Delaware State University, 1200 North DuPont Highway, Dover, DE 19901, USA.
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Gorovits R, Moshe A, Ghanim M, Czosnek H. Recruitment of the host plant heat shock protein 70 by Tomato yellow leaf curl virus coat protein is required for virus infection. PLoS One 2013; 8:e70280. [PMID: 23894631 PMCID: PMC3720902 DOI: 10.1371/journal.pone.0070280] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2013] [Accepted: 06/20/2013] [Indexed: 11/19/2022] Open
Abstract
A functional capsid protein (CP) is essential for host plant infection and insect transmission of Tomato yellow leaf curl virus (TYLCV) and other monopartite begomoviruses. We have previously shown that TYLCV CP specifically interacts with the heat shock protein 70 (HSP70) of the virus insect vector, Bemisia tabaci. Here we demonstrate that during the development of tomato plant infection with TYLCV, a significant amount of HSP70 shifts from a soluble form into insoluble aggregates. CP and HSP70 co-localize in these aggregates, first in the cytoplasm, then in the nucleus of cells associated with the vascular system. CP-HSP70 interaction was demonstrated by co-immunopreciptation in cytoplasmic - but not in nuclear extracts from leaf and stem. Inhibition of HSP70 expression by quercetin caused a decrease in the amount of nuclear CP aggregates and a re-localization of a GFP-CP fusion protein from the nucleus to the cytoplasm. HSP70 inactivation resulted in a decrease of TYLCV DNA levels, demonstrating the role of HSP70 in TYLCV multiplication in planta. The current study reveals for the first time the involvement of plant HSP70 in TYLCV CP intracellular movement. As described earlier, nuclear aggregates contained TYLCV DNA-CP complexes and infectious virions. Showing that HSP70 localizes in these large nuclear aggregates infers that these structures operate as nuclear virus factories.
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Affiliation(s)
- Rena Gorovits
- Institute of Plant Sciences and Genetics in Agriculture, Robert H. Smith Faculty of Agriculture, Food and Environment, Hebrew University of Jerusalem, Rehovot, Israel.
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Laliberté JF, Moffett P, Sanfaçon H, Wang A, Nelson RS, Schoelz JE. e-Book on plant virus infection-a cell biology perspective. FRONTIERS IN PLANT SCIENCE 2013; 4:203. [PMID: 23785382 PMCID: PMC3683628 DOI: 10.3389/fpls.2013.00203] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/22/2013] [Accepted: 05/31/2013] [Indexed: 05/29/2023]
Affiliation(s)
- Jean-François Laliberté
- INRS-Institut Armand-Frappier, Institut National de la Recherche ScientifiqueLaval, QC, Canada
| | - Peter Moffett
- Département de biologie, Université de SherbrookeSherbrooke, QC, Canada
| | - Hélène Sanfaçon
- Pacific Agri-Food Research Centre, Agriculture and Agri-Food CanadaSummerland, BC, Canada
| | - Aiming Wang
- Pacific Agri-Food Research Centre, Agriculture and Agri-Food CanadaSummerland, BC, Canada
| | | | - James E. Schoelz
- Division of Plant Sciences, University of MissouriColumbia, MO, USA
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