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Li Q, Liu Y, Zhang X. Biomolecular condensates in plant RNA silencing: insights into formation, function, and stress responses. THE PLANT CELL 2024; 36:227-245. [PMID: 37772963 PMCID: PMC10827315 DOI: 10.1093/plcell/koad254] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/19/2023] [Revised: 09/14/2023] [Accepted: 09/14/2023] [Indexed: 09/30/2023]
Abstract
Biomolecular condensates are dynamic structures formed through diverse mechanisms, including liquid-liquid phase separation. These condensates have emerged as crucial regulators of cellular processes in eukaryotic cells, enabling the compartmentalization of specific biological reactions while allowing for dynamic exchange of molecules with the surrounding environment. RNA silencing, a conserved gene regulatory mechanism mediated by small RNAs (sRNAs), plays pivotal roles in various biological processes. Multiple types of biomolecular condensate, including dicing bodies, processing bodies, small interfering RNA bodies, and Cajal bodies, have been identified as key players in RNA silencing pathways. These biomolecular condensates provide spatial compartmentation for the biogenesis, loading, action, and turnover of small RNAs. Moreover, they actively respond to stresses, such as viral infections, and modulate RNA silencing activities during stress responses. This review summarizes recent advances in understanding of dicing bodies and other biomolecular condensates involved in RNA silencing. We explore their formation, roles in RNA silencing, and contributions to antiviral resistance responses. This comprehensive overview provides insights into the functional significance of biomolecular condensates in RNA silencing and expands our understanding of their roles in gene expression and stress responses in plants.
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Affiliation(s)
- Qi Li
- State Key Laboratory of Integrated Management of Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences, Beijing, China
- CAS Center for Excellence in Biotic Interactions, University of Chinese Academy of Sciences, Beijing, China
| | - Yang Liu
- State Key Laboratory of Integrated Management of Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences, Beijing, China
- CAS Center for Excellence in Biotic Interactions, University of Chinese Academy of Sciences, Beijing, China
| | - Xiaoming Zhang
- State Key Laboratory of Integrated Management of Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences, Beijing, China
- CAS Center for Excellence in Biotic Interactions, University of Chinese Academy of Sciences, Beijing, China
- HainanYazhou Bay Seed Lab, Sanya, China
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2
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Lettin L, Erbay B, Blair GE. Viruses and Cajal Bodies: A Critical Cellular Target in Virus Infection? Viruses 2023; 15:2311. [PMID: 38140552 PMCID: PMC10747631 DOI: 10.3390/v15122311] [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: 10/12/2023] [Revised: 11/22/2023] [Accepted: 11/23/2023] [Indexed: 12/24/2023] Open
Abstract
Nuclear bodies (NBs) are dynamic structures present in eukaryotic cell nuclei. They are not bounded by membranes and are often considered biomolecular condensates, defined structurally and functionally by the localisation of core components. Nuclear architecture can be reorganised during normal cellular processes such as the cell cycle as well as in response to cellular stress. Many plant and animal viruses target their proteins to NBs, in some cases triggering their structural disruption and redistribution. Although not all such interactions have been well characterised, subversion of NBs and their functions may form a key part of the life cycle of eukaryotic viruses that require the nucleus for their replication. This review will focus on Cajal bodies (CBs) and the viruses that target them. Since CBs are dynamic structures, other NBs (principally nucleoli and promyelocytic leukaemia, PML and bodies), whose components interact with CBs, will also be considered. As well as providing important insights into key virus-host cell interactions, studies on Cajal and associated NBs may identify novel cellular targets for development of antiviral compounds.
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Affiliation(s)
- Lucy Lettin
- School of Molecular and Cellular Biology, University of Leeds, Leeds LS2 9JT, UK (B.E.)
| | - Bilgi Erbay
- School of Molecular and Cellular Biology, University of Leeds, Leeds LS2 9JT, UK (B.E.)
- Moleküler Biyoloji ve Genetik Bölümü, Fen Fakültesi, Van Yuzuncu Yil University, Van 65140, Türkiye
| | - G. Eric Blair
- School of Molecular and Cellular Biology, University of Leeds, Leeds LS2 9JT, UK (B.E.)
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3
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Taliansky ME, Love AJ, Kołowerzo-Lubnau A, Smoliński DJ. Cajal bodies: Evolutionarily conserved nuclear biomolecular condensates with properties unique to plants. THE PLANT CELL 2023; 35:3214-3235. [PMID: 37202374 PMCID: PMC10473218 DOI: 10.1093/plcell/koad140] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/05/2023] [Revised: 04/24/2023] [Accepted: 04/27/2023] [Indexed: 05/20/2023]
Abstract
Proper orchestration of the thousands of biochemical processes that are essential to the life of every cell requires highly organized cellular compartmentalization of dedicated microenvironments. There are 2 ways to create this intracellular segregation to optimize cellular function. One way is to create specific organelles, enclosed spaces bounded by lipid membranes that regulate macromolecular flux in and out of the compartment. A second way is via membraneless biomolecular condensates that form due to to liquid-liquid phase separation. Although research on these membraneless condensates has historically been performed using animal and fungal systems, recent studies have explored basic principles governing the assembly, properties, and functions of membraneless compartments in plants. In this review, we discuss how phase separation is involved in a variety of key processes occurring in Cajal bodies (CBs), a type of biomolecular condensate found in nuclei. These processes include RNA metabolism, formation of ribonucleoproteins involved in transcription, RNA splicing, ribosome biogenesis, and telomere maintenance. Besides these primary roles of CBs, we discuss unique plant-specific functions of CBs in RNA-based regulatory pathways such as nonsense-mediated mRNA decay, mRNA retention, and RNA silencing. Finally, we summarize recent progress and discuss the functions of CBs in responses to pathogen attacks and abiotic stresses, responses that may be regulated via mechanisms governed by polyADP-ribosylation. Thus, plant CBs are emerging as highly complex and multifunctional biomolecular condensates that are involved in a surprisingly diverse range of molecular mechanisms that we are just beginning to appreciate.
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Affiliation(s)
| | - Andrew J Love
- The James Hutton Institute, Invergowrie, Dundee DD2 5DA, UK
| | - Agnieszka Kołowerzo-Lubnau
- Department of Cellular and Molecular Biology, Nicolaus Copernicus University, Lwowska 1, 87-100 Torun, Poland
- Centre for Modern Interdisciplinary Technologies, Nicolaus Copernicus University, Wilenska 4, 87-100 Torun, Poland
| | - Dariusz Jan Smoliński
- Department of Cellular and Molecular Biology, Nicolaus Copernicus University, Lwowska 1, 87-100 Torun, Poland
- Centre for Modern Interdisciplinary Technologies, Nicolaus Copernicus University, Wilenska 4, 87-100 Torun, Poland
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4
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Moreno P, López C, Ruiz-Ruiz S, Peña L, Guerri J. From the smallest to the largest subcellular plant pathogen: Citrus tristeza virus and its unique p23 protein. Virus Res 2022; 314:198755. [PMID: 35341876 DOI: 10.1016/j.virusres.2022.198755] [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: 12/22/2021] [Revised: 02/07/2022] [Accepted: 03/23/2022] [Indexed: 10/18/2022]
Abstract
Knowledge on diseases caused by Citrus tristeza virus (CTV) has greatly increased in last decades after their etiology was demonstrated in the past seventies. Professor Ricardo Flores substantially contributed to these advances in topics like: i) improvement of virus purification to obtain biologically active virions, ii) sequencing mild CTV isolates for genetic comparisons with sequences of moderate or severe isolates and genetic engineering, iii) analysis of genetic variation of both CTV genomic RNA ends and features of the highly variable 5' end that allow accommodating this variation within a conserved secondary structure, iv) studies on the structure, subcellular localization and biological functions of the CTV-unique p23 protein, and v) potential use of p23 and other 3'-proximal regions of the CTV genome to develop transgenic citrus resistant to the virus. Here we review his main achievements on these topics and how they contributed to deeper understanding of CTV biology and to new potential measures for disease control.
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Affiliation(s)
- Pedro Moreno
- Instituto Valenciano de Investigaciones Agrarias (IVIA), Moncada, 46113-Valencia, Spain. (Retired).
| | - Carmelo López
- Instituto de Conservación y Mejora de la Agrodiversidad Valenciana (COMAV), Universitat Politècnica de València, 46022-Valencia, Spain
| | - Susana Ruiz-Ruiz
- Unidad Mixta de Investigación en Genómica y Salud, Fundación para el Fomento de la Investigación Sanitaria y Biomédica de la Comunitat Valenciana (FISABIO), 46022-Valencia, Spain
| | - Leandro Peña
- Instituto de Biología Molecular y Celular de Plantas (IBMCP). Consejo Superior de Investigaciones Científicas (CSIC)-Universidad Politécnica de Valencia (UPV), 46022-Valencia, Spain
| | - José Guerri
- Instituto Valenciano de Investigaciones Agrarias (IVIA), Moncada, 46113-Valencia, Spain. (Retired)
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In Memoriam of Ricardo Flores: The Career, Achievements, and Legacy of an inspirational plant virologist. Virus Res 2022. [DOI: 10.1016/j.virusres.2022.198718] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
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García B, Bedoya L, García JA, Rodamilans B. An Importin-β-like Protein from Nicotiana benthamiana Interacts with the RNA Silencing Suppressor P1b of the Cucumber Vein Yellowing Virus, Modulating Its Activity. Viruses 2021; 13:2406. [PMID: 34960675 PMCID: PMC8706682 DOI: 10.3390/v13122406] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2021] [Revised: 11/26/2021] [Accepted: 11/29/2021] [Indexed: 11/26/2022] Open
Abstract
During a plant viral infection, host-pathogen interactions are critical for successful replication and propagation of the virus through the plant. RNA silencing suppressors (RSSs) are key players of this interplay, and they often interact with different host proteins, developing multiple functions. In the Potyviridae family, viruses produce two main RSSs, HCPro and type B P1 proteins. We focused our efforts on the less known P1b of cucumber vein yellowing virus (CVYV), a type B P1 protein, to try to identify possible factors that could play a relevant role during viral infection. We used a chimeric expression system based on plum pox virus (PPV) encoding a tagged CVYV P1b in place of the canonical HCPro. We used that tag to purify P1b in Nicotiana-benthamiana-infected plants and identified by mass spectrometry an importin-β-like protein similar to importin 7 of Arabidopsis thaliana. We further confirmed the interaction by bimolecular fluorescence complementation assays and defined its nuclear localization in the cell. Further analyses showed a possible role of this N. benthamiana homolog of Importin 7 as a modulator of the RNA silencing suppression activity of P1b.
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Affiliation(s)
| | | | | | - Bernardo Rodamilans
- Centro Nacional de Biotecnología CNB, Consejo Superior de Investigaciones Científicas CSIC, 28049 Madrid, Spain; (B.G.); (L.B.); (J.A.G.)
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Ambrós S, Gómez-Muñoz N, Giménez-Santamarina S, Sánchez-Vicente J, Navarro-López J, Martínez F, Daròs JA, Rodrigo G. Molecular signatures of silencing suppression degeneracy from a complex RNA virus. PLoS Comput Biol 2021; 17:e1009166. [PMID: 34181647 PMCID: PMC8270454 DOI: 10.1371/journal.pcbi.1009166] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2020] [Revised: 07/09/2021] [Accepted: 06/09/2021] [Indexed: 11/21/2022] Open
Abstract
As genomic architectures become more complex, they begin to accumulate degenerate and redundant elements. However, analyses of the molecular mechanisms underlying these genetic architecture features remain scarce, especially in compact but sufficiently complex genomes. In the present study, we followed a proteomic approach together with a computational network analysis to reveal molecular signatures of protein function degeneracy from a plant virus (as virus-host protein-protein interactions). We employed affinity purification coupled to mass spectrometry to detect several host factors interacting with two proteins of Citrus tristeza virus (p20 and p25) that are known to function as RNA silencing suppressors, using an experimental system of transient expression in a model plant. The study was expanded by considering two different isolates of the virus, and some key interactions were confirmed by bimolecular fluorescence complementation assays. We found that p20 and p25 target a common set of plant proteins including chloroplastic proteins and translation factors. Moreover, we noted that even specific targets of each viral protein overlap in function. Notably, we identified argonaute proteins (key players in RNA silencing) as reliable targets of p20. Furthermore, we found that these viral proteins preferentially do not target hubs in the host protein interactome, but elements that can transfer information by bridging different parts of the interactome. Overall, our results demonstrate that two distinct proteins encoded in the same viral genome that overlap in function also overlap in their interactions with the cell proteome, thereby highlighting an overlooked connection from a degenerate viral system.
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Affiliation(s)
- Silvia Ambrós
- Centro de Protección Vegetal y Biotecnología, Instituto Valenciano de Investigaciones Agrarias (IVIA), Moncada, Spain
- Instituto de Biología Molecular y Celular de Plantas (IBMCP), CSIC–Universitat Politècnica de València, València, Spain
- Instituto de Biología Integrativa de Sistemas (I2SysBio), CSIC–Universitat de València, Paterna, Spain
| | - Neus Gómez-Muñoz
- Centro de Protección Vegetal y Biotecnología, Instituto Valenciano de Investigaciones Agrarias (IVIA), Moncada, Spain
| | - Silvia Giménez-Santamarina
- Instituto de Biología Molecular y Celular de Plantas (IBMCP), CSIC–Universitat Politècnica de València, València, Spain
| | - Javier Sánchez-Vicente
- Instituto de Biología Molecular y Celular de Plantas (IBMCP), CSIC–Universitat Politècnica de València, València, Spain
| | - Josep Navarro-López
- Centro de Protección Vegetal y Biotecnología, Instituto Valenciano de Investigaciones Agrarias (IVIA), Moncada, Spain
| | - Fernando Martínez
- Instituto de Biología Molecular y Celular de Plantas (IBMCP), CSIC–Universitat Politècnica de València, València, Spain
| | - José-Antonio Daròs
- Instituto de Biología Molecular y Celular de Plantas (IBMCP), CSIC–Universitat Politècnica de València, València, Spain
| | - Guillermo Rodrigo
- Instituto de Biología Molecular y Celular de Plantas (IBMCP), CSIC–Universitat Politècnica de València, València, Spain
- Instituto de Biología Integrativa de Sistemas (I2SysBio), CSIC–Universitat de València, Paterna, Spain
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Yang Z, Zhang Y, Wang G, Wen S, Wang Y, Li L, Xiao F, Hong N. The p23 of Citrus Tristeza Virus Interacts with Host FKBP-Type Peptidyl-Prolylcis-Trans Isomerase 17-2 and Is Involved in the Intracellular Movement of the Viral Coat Protein. Cells 2021; 10:934. [PMID: 33920690 PMCID: PMC8073322 DOI: 10.3390/cells10040934] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2021] [Revised: 04/12/2021] [Accepted: 04/15/2021] [Indexed: 11/17/2022] Open
Abstract
Citrus tristeza virus is a member of the genus Closterovirus in the family Closteroviridae. The p23 of citrus tristeza virus (CTV) is a multifunctional protein and RNA silencing suppressor. In this study, we identified a p23 interacting partner, FK506-binding protein (FKBP) 17-2, from Citrus aurantifolia (CaFKBP17-2), a susceptible host, and Nicotiana benthamiana (NbFKBP17-2), an experimental host for CTV. The interaction of p23 with CaFKBP17-2 and NbFKBP17-2 were individually confirmed by yeast two-hybrid (Y2H) and bimolecular fluorescence complementation (BiFC) assays. Subcellular localization tests showed that the viral p23 translocated FKBP17-2 from chloroplasts to the plasmodesmata of epidermal cells of N. benthamiana leaves. The knocked-down expression level of NbFKBP17-2 mRNA resulted in a decreased CTV titer in N. benthamiana plants. Further, BiFC and Y2H assays showed that NbFKBP17-2 also interacted with the coat protein (CP) of CTV, and the complexes of CP/NbFKBP17-2 rapidly moved in the cytoplasm. Moreover, p23 guided the CP/NbFKBP17-2 complexes to move along the cell wall. To the best of our knowledge, this is the first report of viral proteins interacting with FKBP17-2 encoded by plants. Our results provide insights for further revealing the mechanism of the CTV CP protein movement.
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Affiliation(s)
- Zuokun Yang
- Key Lab of Plant Pathology of Hubei Province, College of Plant Science and Technology, Huazhong Agricultural University, Wuhan 430070, China; (Z.Y.); (Y.Z.); (G.W.); (S.W.); (Y.W.); (L.L.); (F.X.)
- Key Laboratory of Horticultural Crop (Fruit Trees) Biology and Germplasm Creation of the Ministry of Agriculture, Wuhan 430070, China
| | - Yongle Zhang
- Key Lab of Plant Pathology of Hubei Province, College of Plant Science and Technology, Huazhong Agricultural University, Wuhan 430070, China; (Z.Y.); (Y.Z.); (G.W.); (S.W.); (Y.W.); (L.L.); (F.X.)
- Key Laboratory of Horticultural Crop (Fruit Trees) Biology and Germplasm Creation of the Ministry of Agriculture, Wuhan 430070, China
| | - Guoping Wang
- Key Lab of Plant Pathology of Hubei Province, College of Plant Science and Technology, Huazhong Agricultural University, Wuhan 430070, China; (Z.Y.); (Y.Z.); (G.W.); (S.W.); (Y.W.); (L.L.); (F.X.)
- Key Laboratory of Horticultural Crop (Fruit Trees) Biology and Germplasm Creation of the Ministry of Agriculture, Wuhan 430070, China
| | - Shaohua Wen
- Key Lab of Plant Pathology of Hubei Province, College of Plant Science and Technology, Huazhong Agricultural University, Wuhan 430070, China; (Z.Y.); (Y.Z.); (G.W.); (S.W.); (Y.W.); (L.L.); (F.X.)
- National Biopesticide Engineering Research Centre, Hubei Biopesticide Engineering Research Centre, Hubei Academy of Agricultural Sciences, Wuhan 430064, China
| | - Yanxiang Wang
- Key Lab of Plant Pathology of Hubei Province, College of Plant Science and Technology, Huazhong Agricultural University, Wuhan 430070, China; (Z.Y.); (Y.Z.); (G.W.); (S.W.); (Y.W.); (L.L.); (F.X.)
- Key Laboratory of Horticultural Crop (Fruit Trees) Biology and Germplasm Creation of the Ministry of Agriculture, Wuhan 430070, China
| | - Liu Li
- Key Lab of Plant Pathology of Hubei Province, College of Plant Science and Technology, Huazhong Agricultural University, Wuhan 430070, China; (Z.Y.); (Y.Z.); (G.W.); (S.W.); (Y.W.); (L.L.); (F.X.)
- Key Laboratory of Horticultural Crop (Fruit Trees) Biology and Germplasm Creation of the Ministry of Agriculture, Wuhan 430070, China
| | - Feng Xiao
- Key Lab of Plant Pathology of Hubei Province, College of Plant Science and Technology, Huazhong Agricultural University, Wuhan 430070, China; (Z.Y.); (Y.Z.); (G.W.); (S.W.); (Y.W.); (L.L.); (F.X.)
- Key Laboratory of Horticultural Crop (Fruit Trees) Biology and Germplasm Creation of the Ministry of Agriculture, Wuhan 430070, China
| | - Ni Hong
- Key Lab of Plant Pathology of Hubei Province, College of Plant Science and Technology, Huazhong Agricultural University, Wuhan 430070, China; (Z.Y.); (Y.Z.); (G.W.); (S.W.); (Y.W.); (L.L.); (F.X.)
- Key Laboratory of Horticultural Crop (Fruit Trees) Biology and Germplasm Creation of the Ministry of Agriculture, Wuhan 430070, China
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Carpino C, Ferriol Safont I, Elvira‐González L, Medina V, Rubio L, Peri E, Davino S, Galipienso Torregrosa L. RNA2-encoded VP37 protein of Broad bean wilt virus 1 is a determinant of pathogenicity, host susceptibility, and a suppressor of post-transcriptional gene silencing. MOLECULAR PLANT PATHOLOGY 2020; 21:1421-1435. [PMID: 32936537 PMCID: PMC7549002 DOI: 10.1111/mpp.12979] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/18/2020] [Revised: 07/02/2020] [Accepted: 07/02/2020] [Indexed: 06/01/2023]
Abstract
Broad bean wilt virus 1 (BBWV-1, genus Fabavirus, family Secoviridae) is a bipartite, single-stranded positive-sense RNA virus infecting many horticultural and ornamental crops worldwide. RNA1 encodes proteins involved in viral replication whereas RNA2 encodes two coat proteins (the large and small coat proteins) and two putative movement proteins (MPs) of different sizes with overlapping C-terminal regions. In this work, we determined the role played by the small putative BBWV-1 MP (VP37) on virus pathogenicity, host specificity, and suppression of post-transcriptional gene silencing (PTGS). We engineered a BBWV-1 35S-driven full-length cDNA infectious clone corresponding to BBWV-1 RNA1 and RNA2 (pBBWV1-Wt) and generated a mutant knocking out VP37 (pBBWV1-G492C). Agroinfiltration assays showed that pBBWV1-Wt, as the original BBWV-1 isolate, infected broad bean, tomato, pepper, and Nicotiana benthamiana, whereas pBBWV1-G492C did not infect pepper and tomato systemically. Also, pBBWV1-G492C induced milder symptoms in broad bean and N. benthamiana than pBBWV1-Wt. Differential retrotranscription and amplification of the (+) and (-) strands showed that pBBWV1-G492C replicated in the agroinfiltrated leaves of pepper but not in tomato. All this suggests that VP37 is a determinant of pathogenicity and host specificity. Transient expression of VP37 through a potato virus X (PVX) vector enhanced PVX symptoms and induced systemic necrosis associated with programmed cell death in N. benthamiana plants. Finally, VP37 was identified as a viral suppressor of RNA silencing by transient expression in N. benthamiana 16c plants and movement complementation of a viral construct based on turnip crinkle virus (pTCV-GFP).
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Affiliation(s)
- Caterina Carpino
- Instituto Valenciano de Investigaciones AgrariasValenciaSpain
- Department of Agricultural, Food and Forestry ScienceUniversity of PalermoPalermoItaly
| | | | - Laura Elvira‐González
- Instituto Valenciano de Investigaciones AgrariasValenciaSpain
- Departamento de BiotecnologíaEscuela Técnica Superior de Ingeniería NaturalUniversitat Politècnica de ValènciaValenciaSpain
| | - Vicente Medina
- Departamento de Producción Vegetal y Ciencia ForestalUniversitat de LleidaLleidaSpain
| | - Luis Rubio
- Instituto Valenciano de Investigaciones AgrariasValenciaSpain
| | - Ezio Peri
- Department of Agricultural, Food and Forestry ScienceUniversity of PalermoPalermoItaly
| | - Salvatore Davino
- Department of Agricultural, Food and Forestry ScienceUniversity of PalermoPalermoItaly
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10
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Liu H, Wang G, Yang Z, Wang Y, Zhang Z, Li L, Waqas M, Hong N, Liu H, Wang G, Hong N, Hong J, Zhang J, Xu L, Qi L. Identification and Characterization of a Pear Chlorotic Leaf Spot-Associated Virus, a Novel Emaravirus Associated with a Severe Disease of Pear Trees in China. PLANT DISEASE 2020; 104:2786-2798. [PMID: 32997610 DOI: 10.1094/pdis-01-20-0040-re] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Pear chlorotic leaf spot (PCLS) is a recently emerged disease of commercially cultivated sandy pear (Pyrus pyrifolia) trees in central and southern China. By integrating high-throughput sequencing and conventional Sanger sequencing of reverse-transcription (RT)-PCR products, a novel emaravirus infecting pear trees was identified and molecularly characterized. The virus was provisionally named pear chlorotic leaf spot-associated virus (PCLSaV). PCLSaV shows the typical molecular features of members of the genus Emaravirus in the family Fimoviridae. It has a genome composed of at least five negative-sense RNA segments, with each containing a single open reading frame and two complementary 13-nucleotide stretches at the 5' and 3' termini. PCLSaV shows a close phylogenetic relationship with recognized emaraviruses but forms a separate clade. Moreover, double-membrane-bound bodies were observed in PCLSaV-infected tissues and in extracts of PCLSaV-infected leaves. For the first time, our study revealed the profile distribution of viral RNA reads from the RNA-seq libraries of three samples along the RNA1 to RNA5 of an emaravirus. Field surveys combined with specific RT-PCR assays revealed the presence of PCLSaV in almost all PCLS-diseased pear samples, strongly supporting the association of the virus with the PCLS disease. This study revealed the first emaravirus infecting pear trees and its association with a severe pear chlorotic leaf disease.
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Affiliation(s)
- Huazhen Liu
- Key Lab of Crop Disease Monitoring and Safety Control in Hubei Province, College of Plant Science and Technology, Huazhong Agricultural University, Wuhan, Hubei 430070, China
| | - Guoping Wang
- Key Lab of Crop Disease Monitoring and Safety Control in Hubei Province, College of Plant Science and Technology, Huazhong Agricultural University, Wuhan, Hubei 430070, China
| | - Zuokun Yang
- Key Lab of Crop Disease Monitoring and Safety Control in Hubei Province, College of Plant Science and Technology, Huazhong Agricultural University, Wuhan, Hubei 430070, China
| | - Yanxiang Wang
- Key Lab of Crop Disease Monitoring and Safety Control in Hubei Province, College of Plant Science and Technology, Huazhong Agricultural University, Wuhan, Hubei 430070, China
| | - Zhe Zhang
- Key Lab of Crop Disease Monitoring and Safety Control in Hubei Province, College of Plant Science and Technology, Huazhong Agricultural University, Wuhan, Hubei 430070, China
| | - Longhui Li
- Key Lab of Crop Disease Monitoring and Safety Control in Hubei Province, College of Plant Science and Technology, Huazhong Agricultural University, Wuhan, Hubei 430070, China
| | - Muhammad Waqas
- Key Lab of Crop Disease Monitoring and Safety Control in Hubei Province, College of Plant Science and Technology, Huazhong Agricultural University, Wuhan, Hubei 430070, China
| | - Ni Hong
- Key Lab of Crop Disease Monitoring and Safety Control in Hubei Province, College of Plant Science and Technology, Huazhong Agricultural University, Wuhan, Hubei 430070, China
| | - Huazhen Liu
- Key Laboratory of Horticultural Plant Biology, Ministry of Education, Huazhong Agricultural University, Wuhan, Hubei 430070, China
| | - Guoping Wang
- Key Laboratory of Horticultural Plant Biology, Ministry of Education, Huazhong Agricultural University, Wuhan, Hubei 430070, China
| | - Ni Hong
- Key Laboratory of Horticultural Plant Biology, Ministry of Education, Huazhong Agricultural University, Wuhan, Hubei 430070, China
| | - Jian Hong
- Analysis Center of Agrobiology and Environmental Sciences, Zhejiang University, Hangzhou, Zhejiang 317502, China
| | - Jinguo Zhang
- National Sand Pear Germplasm Repository in Wuchang, Research Institute of Fruit and Tea, Hubei Academy of Agricultural Science, Wuhan, Hubei 430064, China
| | - Lei Xu
- Jiangxi Academy of Agricultural Sciences, Nanchang, Jiangxi 330200, China
| | - Liying Qi
- Jiangxi Academy of Agricultural Sciences, Nanchang, Jiangxi 330200, China
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Davino S, Ruiz-Ruiz S, Serra P, Forment J, Flores R. Revisiting the cysteine-rich proteins encoded in the 3'-proximal open reading frame of the positive-sense single-stranded RNA of some monopartite filamentous plant viruses: functional dissection of p15 from grapevine virus B. Arch Virol 2020; 165:2229-2239. [PMID: 32676682 DOI: 10.1007/s00705-020-04729-w] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2020] [Accepted: 06/09/2020] [Indexed: 10/23/2022]
Abstract
A reexamination of proteins with conserved cysteines and basic amino acids encoded by the 3'-proximal gene of the positive-sense single-stranded RNA of some monopartite filamentous plant viruses has been carried out. The cysteines are involved in a putative Zn-finger domain, which, together with the basic amino acids, form part of the nuclear or nucleolar localization signals. An in-depth study of one of these proteins, p15 from grapevine B virus (GVB), has shown: (i) a three-dimensional structure with four α-helices predicted by two independent in silico approaches, (ii) the nucleolus as the main accumulation site by applying confocal laser microscopy to a fusion between p15 and the green fluorescent protein, (iii) the involvement of the basic amino acids and the putative Zn-finger domain, mapping at the N-terminal region of p15, in the nucleolar localization signal, as revealed by the effect of six alanine substitution mutations, (iv) the p15 suppressor function of sense-mediated RNA silencing as revealed by agroinfiltration in a transgenic line of Nicotiana benthamiana, and (v) the enhancer activity of p15 on viral pathogenicity in N. benthamiana when expressed from a potato virus X vector. In addition, we elaborate on an evolutionary scenario for these filamentous viruses, invoking takeover by a common ancestor(s) of viral or host genes coding for those cysteine-rich proteins, followed by divergence, which would also explain why they are encoded in the 3'-proximal gene of the genomic single-stranded viral RNA.
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Affiliation(s)
- Salvatore Davino
- Instituto de Biologia Molecular y Celular de Plantas (UPV-CSIC), Universidad Politécnica de Valencia, Avenida de los Naranjos, 46022, Valencia, Spain
- Department of Agricultural, Food and Forest Sciences, University of Palermo, Viale delle Scienze Building 5, 90128, Palermo, Italy
| | - Susana Ruiz-Ruiz
- Instituto de Biologia Molecular y Celular de Plantas (UPV-CSIC), Universidad Politécnica de Valencia, Avenida de los Naranjos, 46022, Valencia, Spain
| | - Pedro Serra
- Instituto de Biologia Molecular y Celular de Plantas (UPV-CSIC), Universidad Politécnica de Valencia, Avenida de los Naranjos, 46022, Valencia, Spain
| | - Javier Forment
- Instituto de Biologia Molecular y Celular de Plantas (UPV-CSIC), Universidad Politécnica de Valencia, Avenida de los Naranjos, 46022, Valencia, Spain
| | - Ricardo Flores
- Instituto de Biologia Molecular y Celular de Plantas (UPV-CSIC), Universidad Politécnica de Valencia, Avenida de los Naranjos, 46022, Valencia, Spain.
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12
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Zhang CW, Liu Q, Zeng Q, Huang WT, Wang Q, Cheng YQ. p24 G1 Encoded by Grapevine Leafroll-Associated Virus 1 Suppresses RNA Silencing and Elicits Hypersensitive Response-Like Necrosis in Nicotiana Species. Viruses 2020; 12:E1111. [PMID: 33007975 PMCID: PMC7601950 DOI: 10.3390/v12101111] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2020] [Revised: 09/19/2020] [Accepted: 09/29/2020] [Indexed: 01/21/2023] Open
Abstract
Grapevine leafroll-associated virus 1 (GLRaV-1) is a major pathogen associated with grapevine leafroll disease. However, the molecular mechanisms underlying GLRaV-1 interactions with plant cells are unclear. Using Agrobacterium infiltration-mediated RNA-silencing assays, we demonstrated that GLRaV-1 p24 protein (p24G1) acts as an RNA-silencing suppressor (RSS), inhibiting local and systemic RNA silencing. Electrophoretic mobility shift assays showed that p24G1 binds double-stranded 21-nucleotide small interfering RNA (siRNA), and that siRNA binding is required but not sufficient for its RSS activity. p24G1 localizes in the nucleus and can self-interact through its amino acid 10 to 210 region. Dimerization is needed for p24G1 interaction with importin α1 before moving to the nucleus, but is not required for its siRNA binding and RSS activity. Expression of p24G1 from a binary pGD vector or potato virus X-based vector elicited a strong hypersensitive response in Nicotiana species, indicating that p24G1 may be a factor in pathogenesis. Furthermore, p24G1 function in pathogenesis required its RSS activity, dimerization and nuclear localization. In addition, the region of amino acids 122-139 played a crucial role in the nuclear import, siRNA binding, silencing suppression and pathogenic activity of p24G1. These results contribute to our understanding of the molecular mechanisms underlying GLRaV-1 infection.
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Affiliation(s)
- Chen-Wei Zhang
- Department of Pomology, China Agricultural University, Beijing 100193, China; (C.-W.Z.); (Q.L.); (Q.Z.); (W.-T.H.)
- Key Laboratory of Viticulture and Enology, Ministry of Agriculture, Beijing 100083, China
| | - Qing Liu
- Department of Pomology, China Agricultural University, Beijing 100193, China; (C.-W.Z.); (Q.L.); (Q.Z.); (W.-T.H.)
- Key Laboratory of Viticulture and Enology, Ministry of Agriculture, Beijing 100083, China
| | - Qi Zeng
- Department of Pomology, China Agricultural University, Beijing 100193, China; (C.-W.Z.); (Q.L.); (Q.Z.); (W.-T.H.)
- Key Laboratory of Viticulture and Enology, Ministry of Agriculture, Beijing 100083, China
| | - Wen-Ting Huang
- Department of Pomology, China Agricultural University, Beijing 100193, China; (C.-W.Z.); (Q.L.); (Q.Z.); (W.-T.H.)
- Key Laboratory of Viticulture and Enology, Ministry of Agriculture, Beijing 100083, China
| | - Qi Wang
- Department of Plant Pathology, China Agricultural University, Beijing 100193, China;
| | - Yu-Qin Cheng
- Department of Pomology, China Agricultural University, Beijing 100193, China; (C.-W.Z.); (Q.L.); (Q.Z.); (W.-T.H.)
- Key Laboratory of Viticulture and Enology, Ministry of Agriculture, Beijing 100083, China
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13
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Sanfaçon H. Modulation of disease severity by plant positive-strand RNA viruses: The complex interplay of multifunctional viral proteins, subviral RNAs and virus-associated RNAs with plant signaling pathways and defense responses. Adv Virus Res 2020; 107:87-131. [PMID: 32711736 DOI: 10.1016/bs.aivir.2020.04.003] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Plant viruses induce a range of symptoms of varying intensity, ranging from severe systemic necrosis to mild or asymptomatic infection. Several evolutionary constraints drive virus virulence, including the dependence of viruses on host factors to complete their infection cycle, the requirement to counteract or evade plant antiviral defense responses and the mode of virus transmission. Viruses have developed an array of strategies to modulate disease severity. Accumulating evidence has highlighted not only the multifunctional role that viral proteins play in disrupting or highjacking plant factors, hormone signaling pathways and intracellular organelles, but also the interaction networks between viral proteins, subviral RNAs and/or other viral-associated RNAs that regulate disease severity. This review focusses on positive-strand RNA viruses, which constitute the majority of characterized plant viruses. Using well-characterized viruses with different genome types as examples, recent advances are discussed as well as knowledge gaps and opportunities for further research.
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Affiliation(s)
- Hélène Sanfaçon
- Summerland Research and Development Centre, Agriculture and Agri-Food Canada, Summerland, BC, Canada.
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14
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Dao TNM, Kang SH, Bak A, Folimonova SY. A Non-Conserved p33 Protein of Citrus Tristeza Virus Interacts with Multiple Viral Partners. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2020; 33:859-870. [PMID: 32141354 DOI: 10.1094/mpmi-11-19-0328-fi] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
The RNA genome of citrus tristeza virus (CTV), one of the most damaging viral pathogens of citrus, contains 12 open reading frames resulting in production of at least 19 proteins. Previous studies on the intraviral interactome of CTV revealed self-interaction of the viral RNA-dependent RNA polymerase, the major coat protein (CP), p20, p23, and p33 proteins, while heterologous interactions between the CTV proteins have not been characterized. In this work, we examined interactions between the p33 protein, a nonconserved protein of CTV, which performs multiple functions in the virus infection cycle and is needed for virus ability to infect the extended host range, with other CTV proteins shown to mediate virus interactions with its plant hosts. Using yeast two-hybrid, bimolecular fluorescence complementation, and coimmunoprecipitation assays, we demonstrated that p33 interacts with three viral proteins, i.e., CP, p20, and p23, in vivo and in planta. Coexpression of p33, which is an integral membrane protein, resulted in a shift in the localization of the p20 and p23 proteins toward the subcellular crude-membrane fraction. Upon CTV infection, the four proteins colocalized in the CTV replication factories. In addition, three of them, CP, p20, and p23, were found in the p33-formed membranous structures. Using bioinformatic analyses and mutagenesis, we found that the N-terminus of p33 is involved in the interactions with all three protein partners. A potential role of these interactions in virus ability to infect the extended host range is discussed.
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Affiliation(s)
- Thi Nguyet Minh Dao
- University of Florida, Plant Pathology Department, Gainesville, FL 32611, U.S.A
| | - Sung-Hwan Kang
- University of Florida, Plant Pathology Department, Gainesville, FL 32611, U.S.A
| | - Aurélie Bak
- University of Florida, Plant Pathology Department, Gainesville, FL 32611, U.S.A
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15
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Ding Y, Lozano-Durán R. The Cajal Body in Plant-Virus Interactions. Viruses 2020; 12:E250. [PMID: 32102236 PMCID: PMC7077289 DOI: 10.3390/v12020250] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2020] [Revised: 02/14/2020] [Accepted: 02/18/2020] [Indexed: 01/23/2023] Open
Abstract
Cajal bodies (CBs) are nuclear membraneless bodies composed of proteins and RNA. Although it is known that CBs play a role in RNA metabolism and the formation of functional ribonucleoprotein (RNP) particles, the whole breadth of CB functions is far from being fully elucidated. In this short review, we will summarize and discuss the growing body of evidence pointing to an involvement of this subnuclear compartment in plant-virus interactions.
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Affiliation(s)
- Yi Ding
- Shanghai Center for Plant Stress Biology, Chinese Academy of Sciences, Shanghai 201602, China;
- Center for Excellence in Molecular Plant Science, Chinese Academy of Sciences, Shanghai 201602, China
- University of the Chinese Academy of Sciences, Beijing 100049, China
| | - Rosa Lozano-Durán
- Shanghai Center for Plant Stress Biology, Chinese Academy of Sciences, Shanghai 201602, China;
- Center for Excellence in Molecular Plant Science, Chinese Academy of Sciences, Shanghai 201602, China
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16
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Identification and Characterization of the Nucleolar Localization Signal of Autographa californica Multiple Nucleopolyhedrovirus LEF5. J Virol 2020; 94:JVI.01891-19. [PMID: 31776271 DOI: 10.1128/jvi.01891-19] [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] [Received: 11/08/2019] [Accepted: 11/19/2019] [Indexed: 11/20/2022] Open
Abstract
Autographa californica multiple nucleopolyhedrovirus (AcMNPV) late expression factor 5 (LEF5) is highly conserved in all sequenced baculovirus genomes and plays an important role in production of infectious viral progeny. In this study, nucleolar localization of AcMNPV LEF5 was characterized. Through transcriptome analysis, we identified two putative nucleolar proteins, Spodoptera frugiperda nucleostemin (SfNS) and fibrillarin (SfFBL), from Sf9 cells. Immunofluorescence analysis demonstrated that SfNS and SfFBL were localized to the nucleolus. AcMNPV infection resulted in reorganization of the nucleoli of infected cells. Colocalization of LEF5 and SfNS showed that AcMNPV LEF5 was localized to the nucleolus in Sf9 cells. Bioinformatic analysis revealed that basic amino acids of LEF5 are enriched at residues 184 to 213 and may contain a nucleolar localization signal (NoLS). Green fluorescent protein (GFP) fused to NoLS of AcMNPV LEF5 localized to the nucleoli of transfected cells. Multiple-point mutation analysis demonstrated that amino acid residues 197 to 204 are important for nucleolar localization of LEF5. To identify whether the NoLS in AcMNPV LEF5 is important for production of viral progeny, a lef5-null AcMNPV bacmid was constructed; several NoLS-mutated LEF5 proteins were reinserted into the lef5-null AcMNPV bacmid with a GFP reporter. The constructs containing point mutations at residues 185 to 189 or 197 to 204 in AcMNPV LEF5 resulted in reduction in production of infectious viral progeny and occlusion body yield in bacmid-transfected cells. Together, these data suggested that AcMNPV LEF5 contains an NoLS, which is important for nucleolar localization of LEF5, progeny production, and occlusion body production.IMPORTANCE Many viruses, including human and plant viruses, target nucleolar functions as part of their infection strategy. However, nucleolar localization for baculovirus proteins has not yet been characterized. In this study, two nucleolar proteins, SfNS and SfFBL, were identified in Sf9 cells. Our results showed that Autographa californica multiple nucleopolyhedrovirus (AcMNPV) infection resulted in redistribution of the nucleoli of infected cells. We demonstrated that AcMNPV late expression factor 5 (LEF5) could localize to the nucleolus and contains a nucleolar localization signal (NoLS), which is important for nucleolar localization of AcMNPV LEF5 and for production of viral progeny and yield of occlusion bodies.
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17
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Maree HJ, Blouin AG, Diaz-Lara A, Mostert I, Al Rwahnih M, Candresse T. Status of the current vitivirus taxonomy. Arch Virol 2019; 165:451-458. [PMID: 31845154 DOI: 10.1007/s00705-019-04500-w] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2019] [Accepted: 11/12/2019] [Indexed: 11/25/2022]
Abstract
Since the establishment of the genus Vitivirus, several additional viruses have been sequenced and proposed to represent new species of this genus. Currently, the International Committee on Taxonomy of Viruses recognizes 15 vitivirus species. The report of new vitiviruses that fail to completely adhere to the species demarcation criteria, the incorporation of non-vitivirus grapevine viruses in the unofficial "naming system", and the existence of non-grapevine vitiviruses lead to inconsistencies in classification. In this report, we give a brief overview of vitiviruses and use currently available information to clarify the present status of the vitivirus taxonomy.
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Affiliation(s)
- H J Maree
- Department of Genetics, Stellenbosch University, Private Bag X1, Matieland, 7602, South Africa.
- Citrus Research International, P.O. Box 2201, Matieland, 7602, South Africa.
| | - A G Blouin
- Integrated and Urban Plant Pathology Laboratory, Gembloux Agro-Bio Tech, University of Liège, 5030, Gembloux, Belgium
- The New Zealand Institute for Plant and Food Research Limited, Private Bag 92169, Auckland, 1142, New Zealand
| | - A Diaz-Lara
- Department of Plant Pathology, University of California-Davis, Davis, CA, 95616, USA
| | - I Mostert
- Department of Genetics, Stellenbosch University, Private Bag X1, Matieland, 7602, South Africa
| | - M Al Rwahnih
- Department of Plant Pathology, University of California-Davis, Davis, CA, 95616, USA
| | - T Candresse
- INRAE, Univ. Bordeaux, UMR BFP, 33882, Villenave d'Ornon Cedex, France
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18
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Wang X, Luo C, Xu Y, Zhang C, Bao M, Dou J, Wang Q, Cheng Y. Expression of the p24 silencing suppressor of Grapevine leafroll-associated virus 2 from Potato virus X or Barley stripe mosaic virus vector elicits hypersensitive responses in Nicotiana benthamiana. PLANT PHYSIOLOGY AND BIOCHEMISTRY : PPB 2019; 142:34-42. [PMID: 31255907 DOI: 10.1016/j.plaphy.2019.06.033] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/08/2019] [Revised: 05/24/2019] [Accepted: 06/23/2019] [Indexed: 06/09/2023]
Abstract
The 24-kDa protein (p24) encoded by Grapevine leafroll-associated virus 2 (GLRaV-2) is an RNA-silencing suppressor (RSS), but its effect on active viral infection is unclear. Using a Potato virus X (PVX)-based expression system, we demonstrated that p24 elicits lethal systemic necrosis in Nicotiana benthamiana, sharing typical characteristics of the hypersensitive response (HR), and that NbRAR1 (a cytoplasmic Zn2+-binding protein) is involved in the PVX-p24-mediated systemic necrosis. Moreover, expression of p24 from Barley stripe mosaic virus (BSMV) vector triggered local necrosis in infiltrated patches of N. benthamiana, likely inhibiting viral systemic spread. By deletion analysis, we demonstrated that amino acids (aa) 1 to 180, which are located in the region (aa 1-188) previously shown to be necessary for p24's RSS activity, is sufficient for p24 to elicit systemic necrosis in the context of PVX infection. Using substitution mutants, we revealed that silencing-suppression-defective mutants R2A and W54A induce only a mild necrotic response; two mutants without self-interaction ability previously shown to lose or retain weak suppression function also displayed decreased pathogenicity: W149A without RSS activity elicited a mild necrotic response, whereas V162H/L169H/L170H which retains weak RSS activity was able to induce systemic necrosis, but with a 1- to 2-day delay. Taken together, p24 plays an important role in GLRaV-2 pathogenesis, triggering HR-like necrosis in N. benthamiana plants when expressed from PVX or BSMV vector; both the silencing suppression and self-interaction are crucial for p24's pathogenicity activity, and the region of p24 for determining systemic necrosis is mapped to aa 1-180.
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Affiliation(s)
- Xianyou Wang
- Department of Pomology, China Agricultural University, Beijing, 100193, China; Key Laboratory of Viticulture and Enology, Ministry of Agriculture, Beijing, 100083, China
| | - Chen Luo
- Department of Pomology, China Agricultural University, Beijing, 100193, China; Key Laboratory of Viticulture and Enology, Ministry of Agriculture, Beijing, 100083, China
| | - Yanfei Xu
- DeLaval Tianjin Company, Tianjin, 300308, China
| | - Chenwei Zhang
- Department of Pomology, China Agricultural University, Beijing, 100193, China; Key Laboratory of Viticulture and Enology, Ministry of Agriculture, Beijing, 100083, China
| | - Mian Bao
- Department of Pomology, China Agricultural University, Beijing, 100193, China; Key Laboratory of Viticulture and Enology, Ministry of Agriculture, Beijing, 100083, China
| | - Junjie Dou
- Department of Pomology, China Agricultural University, Beijing, 100193, China; Key Laboratory of Viticulture and Enology, Ministry of Agriculture, Beijing, 100083, China
| | - Qi Wang
- Department of Plant Pathology, China Agricultural University, Beijing, 100193, China
| | - Yuqin Cheng
- Department of Pomology, China Agricultural University, Beijing, 100193, China; Key Laboratory of Viticulture and Enology, Ministry of Agriculture, Beijing, 100083, China.
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Identification of Key Residues Required for RNA Silencing Suppressor Activity of p23 Protein from a Mild Strain of Citrus Tristeza Virus. Viruses 2019; 11:v11090782. [PMID: 31450668 PMCID: PMC6784005 DOI: 10.3390/v11090782] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2019] [Revised: 08/18/2019] [Accepted: 08/23/2019] [Indexed: 12/16/2022] Open
Abstract
The severe strain of citrus tristeza virus (CTV) causes quick decline of citrus trees. However, the CTV mild strain causes no symptoms and commonly presents in citrus trees. Viral suppressor of RNA silencing (VSR) plays an important role in the successful invasion of viruses into plants. For CTV, VSR has mostly been studied in severe strains. In this study, the N4 mild strain in China was sequenced and found to have high sequence identity with the T30 strain. Furthermore, we verified the functions of three VSRs in the N4 strain, and p23 was found to be the most effective in terms of local silencing suppressor activity among the three CTV VSRs and localized to both nucleus and plasmodesmata, which is similar to CTV T36 strain. Several conserved amino acids were identified in p23. Mutation of E95A/V96A and M99A/L100AA impaired p23 protein stability. Consequently, these two mutants lost most of its suppressor activity and their protein levels could not be rescued by co-expressing p19. Q93A and R143A/E144A abolished p23 suppressor activity only and their protein levels increased to wild type level when co-expressed with p19. This work may facilitate a better understanding of the pathogenic mechanism of CTV mild strains.
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20
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Wieczorek P, Wrzesińska B, Frąckowiak P, Przybylska A, Obrępalska-Stęplowska A. Contribution of Tomato torrado virus Vp26 coat protein subunit to systemic necrosis induction and virus infectivity in Solanum lycopersicum. Virol J 2019; 16:9. [PMID: 30642343 PMCID: PMC6332883 DOI: 10.1186/s12985-019-1117-9] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2018] [Accepted: 01/06/2019] [Indexed: 12/28/2022] Open
Abstract
BACKGROUND Tomato torrado virus (ToTV) infection manifests with burn-like symptoms on leaves, leaflets and upper stem parts of susceptible infected plants. The symptoms caused by ToTV may be considered as one of the most severe virus-induced forms of systemic necrosis, which spreads within the whole plant and leads to a lethal phenotype. However, to date there are no data revealing which viral genes encode for a specific pathogenicity determinant that triggers the plant necrotic response for any torradovirus. In this study we evaluated the influence of three coat protein subunits of ToTV: Vp23, Vp26 and Vp35, transiently expressed from a PVX-based vector, and checked their association with the induction of systemic necrosis in infected Solanum lycopersicum L. (cv. Beta Lux), a natural host of ToTV. METHODS To estimate how ToTV coat protein subunits might contribute in plant response to virus infection we over-expressed the proteins from PVX-based vector in tomato and analyzed enzymatic activities related with plant defense response. By doing protein qualitative analysis performed by mass spectrometry we indicated the PR10 in protein fraction with induced ribonuclease activity. RESULTS We observed that only the Vp26 enhanced PVX pathogenicity causing severe necrosis of the infected plant. Moreover, we indicated increased RNase and oxidative activities in plants infected with PVX-Vp26 chimeras only. Importantly, we suspected that this increased RNase activity is associated with increased accumulation of PR10 mRNA and products of its translation. CONCLUSIONS On the basis of the obtained results, we indicated that Vp26 acts as the elicitor of hypersensitive response-like reactions of PVX-Vp26 manifesting with enhanced pathogenicity of the recombined PVX. This might be the first described suspected necrosis determinant of torradoviruses infecting tomatoes.
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Affiliation(s)
- Przemysław Wieczorek
- Department of Entomology, Animal Pests & Biotechnology, Institute of Plant Protection-National Research Institute, Władysława Węgorka 20 St, 60-318, Poznań, Poland
| | - Barbara Wrzesińska
- Department of Entomology, Animal Pests & Biotechnology, Institute of Plant Protection-National Research Institute, Władysława Węgorka 20 St, 60-318, Poznań, Poland
| | - Patryk Frąckowiak
- Department of Entomology, Animal Pests & Biotechnology, Institute of Plant Protection-National Research Institute, Władysława Węgorka 20 St, 60-318, Poznań, Poland
| | - Arnika Przybylska
- Department of Entomology, Animal Pests & Biotechnology, Institute of Plant Protection-National Research Institute, Władysława Węgorka 20 St, 60-318, Poznań, Poland
| | - Aleksandra Obrępalska-Stęplowska
- Department of Entomology, Animal Pests & Biotechnology, Institute of Plant Protection-National Research Institute, Władysława Węgorka 20 St, 60-318, Poznań, Poland.
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21
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RNA Interference: A Natural Immune System of Plants to Counteract Biotic Stressors. Cells 2019; 8:cells8010038. [PMID: 30634662 PMCID: PMC6356646 DOI: 10.3390/cells8010038] [Citation(s) in RCA: 59] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2018] [Revised: 01/01/2019] [Accepted: 01/07/2019] [Indexed: 02/06/2023] Open
Abstract
During plant-pathogen interactions, plants have to defend the living transposable elements from pathogens. In response to such elements, plants activate a variety of defense mechanisms to counteract the aggressiveness of biotic stressors. RNA interference (RNAi) is a key biological process in plants to inhibit gene expression both transcriptionally and post-transcriptionally, using three different groups of proteins to resist the virulence of pathogens. However, pathogens trigger an anti-silencing mechanism through the expression of suppressors to block host RNAi. The disruption of the silencing mechanism is a virulence strategy of pathogens to promote infection in the invaded hosts. In this review, we summarize the RNA silencing pathway, anti-silencing suppressors, and counter-defenses of plants to viral, fungal, and bacterial pathogens.
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22
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Ruiz-Ruiz S, Navarro B, Peña L, Navarro L, Moreno P, Di Serio F, Flores R. Citrus tristeza virus: Host RNA Silencing and Virus Counteraction. Methods Mol Biol 2019; 2015:195-207. [PMID: 31222705 DOI: 10.1007/978-1-4939-9558-5_14] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
To dissect the host RNA silencing response incited by citrus tristeza virus (CTV, genus Closterovirus), a (+) ssRNA of ~19300 nt, and the counter reaction deployed by the virus via its three RNA silencing suppressors (RSS), the small RNAs (sRNAs) of three virus-host combinations were deep sequenced. The subsequent analysis indicated that CTV sRNAs (1) constitute more than half of the total sRNAs in the susceptible Mexican lime and sweet orange, while only 3.5% in the restrictive sour orange; (2) are mostly of 21-22 nt, with those of (+) sense predominating slightly; and (3) derive from all the CTV genome, as evidenced by its entire recomposition from viral sRNA contigs but adopt an asymmetric pattern with a hotspot mapping at the 3'-terminal ~2500 nt. The citrus homologues of Arabidopsis Dicer-like (DCL) 4 and 2 most likely generate the 21 and 22 nt CTV sRNAs, respectively, by dicing the gRNA and the 3' co-terminal sgRNAs and, particularly, their double-stranded forms accumulating in infected cells. The plant sRNA profile, very similar and dominated by the 24 nt sRNAs in the three mock-inoculated controls, displayed a major reduction of the 24 nt sRNAs in Mexican lime and sweet orange, but not in sour orange. CTV infection also influences the levels of certain microRNAs.The high accumulation of CTV sRNAs in two of the citrus hosts examined suggests that it is not their synthesis, but their function, the target of the RSS encoded by CTV: p25 (intercellular), p23 (intracellular) and p20 (both). The two latter might block the loading of CTV sRNAs into the RNA silencing complex or interfere with it through alternative mechanisms. Of the three CTV RSS, p23 is the one that has been more thoroughly studied. It is a multifunctional RNA-binding protein with a putative Zn finger domain and basic motifs that (1) has no homologues in other closteroviruses, (2) accumulates in the nucleolus and plasmodesmata, (3) regulates the asymmetric balance of CTV (+) and (-) RNA strands, and (4) induces CTV syndromes and stimulates systemic infection in certain citrus species when expressed as a transgene ectopically or in phloem-associated cells.
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Affiliation(s)
- Susana Ruiz-Ruiz
- Instituto de Biología Molecular y Celular de Plantas, Universidad Politécnica de Valencia-Consejo Superior de Investigaciones Científicas, Valencia, Spain
| | - Beatriz Navarro
- Istituto per la Protezione Sostenibile delle Piante, Consiglio Nazionale delle Ricerche, Bari, Italy
| | - Leandro Peña
- Instituto de Biología Molecular y Celular de Plantas, Universidad Politécnica de Valencia-Consejo Superior de Investigaciones Científicas, Valencia, Spain.,Instituto Valenciano de Investigaciones Agrarias, Moncada, Spain
| | - Luis Navarro
- Centro de Protección Vegetal y Biotecnología, Instituto Valenciano de Investigaciones Agrarias (IVIA), Valencia, Spain
| | - Pedro Moreno
- Centro de Protección Vegetal y Biotecnología, Instituto Valenciano de Investigaciones Agrarias (IVIA), Valencia, Spain
| | - Francesco Di Serio
- Istituto per la Protezione Sostenibile delle Piante, Consiglio Nazionale delle Ricerche, Bari, Italy
| | - Ricardo Flores
- Instituto de Biología Molecular y Celular de Plantas, Universidad Politécnica de Valencia-Consejo Superior de Investigaciones Científicas, Valencia, Spain.
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Acanda Y, Wang C, Levy A. Gene Expression in Citrus Plant Cells Using Helios ® Gene Gun System for Particle Bombardment. Methods Mol Biol 2019; 2015:219-228. [PMID: 31222707 DOI: 10.1007/978-1-4939-9558-5_16] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
To understand how Citrus tristeza virus (CTV) replicates and moves inside the plant, it is critical to study the cellular interactions and localization of its encoded proteins. However, due to technical limitations, so far these studies have been limited to the nonnatural host Nicotiana benthamiana.Particle bombardment is a physical method to deliver nucleic acid and other biomolecules into the cells directly. The Helios® gene gun (Bio-Rad, Hercules, CA) is a handheld device that uses a low-pressure helium pulse to accelerate high-density, subcellular-sized particles into a wide variety of targets for in vivo and in vitro applications. Here, we describe a detail protocol for either transient or stable gene expression in citrus leaf cells using this gene gun. This protocol can be used to study protein-protein interactions and subcellular localization in different kinds of plant cells.
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Affiliation(s)
- Yosvanis Acanda
- Department of Plant Pathology, Citrus Research and Education Center, University of Florida, Lake Alfred, FL, USA
| | - Chunxia Wang
- Citrus Research and Education Center, University of Florida, Lake Alfred, FL, USA
| | - Amit Levy
- Department of Plant Pathology, Citrus Research and Education Center, University of Florida, Lake Alfred, FL, USA.
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Ruiz-Ruiz S, Spanò R, Navarro L, Moreno P, Peña L, Flores R. Citrus tristeza virus co-opts glyceraldehyde 3-phosphate dehydrogenase for its infectious cycle by interacting with the viral-encoded protein p23. PLANT MOLECULAR BIOLOGY 2018; 98:363-373. [PMID: 30392159 PMCID: PMC7088584 DOI: 10.1007/s11103-018-0783-0] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/14/2018] [Accepted: 10/01/2018] [Indexed: 05/03/2023]
Abstract
KEY MESSAGE Citrus tristeza virus encodes a unique protein, p23, with multiple functional roles that include co-option of the cytoplasmic glyceraldehyde 3-phosphate dehydrogenase to facilitate the viral infectious cycle. The genome of citrus tristeza virus (CTV), genus Closterovirus family Closteroviridae, is a single-stranded (+) RNA potentially encoding at least 17 proteins. One (p23), an RNA-binding protein of 209 amino acids with a putative Zn-finger and some basic motifs, displays singular features: (i) it has no homologues in other closteroviruses, (ii) it accumulates mainly in the nucleolus and Cajal bodies, and in plasmodesmata, and (iii) it mediates asymmetric accumulation of CTV RNA strands, intracellular suppression of RNA silencing, induction of some CTV syndromes and enhancement of systemic infection when expressed as a transgene ectopically or in phloem-associated cells in several Citrus spp. Here, a yeast two-hybrid screening of an expression library of Nicotiana benthamiana (a symptomatic experimental host for CTV), identified a transducin/WD40 domain protein and the cytosolic glyceraldehyde 3-phosphate dehydrogenase (GAPDH) as potential host interactors with p23. Bimolecular fluorescence complementation corroborated the p23-GAPDH interaction in planta and showed that p23 interacts with itself in the nucleolus, Cajal bodies and plasmodesmata, and with GAPDH in the cytoplasm (forming aggregates) and in plasmodesmata. The latter interaction was preserved in a p23 deletion mutant affecting the C-terminal domain, but not in two others affecting the Zn-finger and one internal basic motif. Virus-induced gene silencing of GAPDH mRNA resulted in a decrease of CTV titer as revealed by real-time RT-quantitative PCR and RNA gel-blot hybridization. Thus, like other viruses, CTV seems to co-opt GAPDH, via interaction with p23, to facilitate its infectious cycle.
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Affiliation(s)
- Susana Ruiz-Ruiz
- Instituto de Biología Molecular y Celular de Plantas, Consejo Superior de Investigaciones Científicas (CSIC)-Universidad Politécnica de Valencia (UPV), Valencia, Spain
| | - Roberta Spanò
- Instituto de Biología Molecular y Celular de Plantas, Consejo Superior de Investigaciones Científicas (CSIC)-Universidad Politécnica de Valencia (UPV), Valencia, Spain
- Dipartimento di Scienze del Suolo della Pianta e degli Alimenti, Università degli Studi di Bari "Aldo Moro", Bari, Italy
| | - Luis Navarro
- Instituto Valenciano de Investigaciones Agrarias (IVIA), Moncada, Valencia, Spain
| | - Pedro Moreno
- Instituto Valenciano de Investigaciones Agrarias (IVIA), Moncada, Valencia, Spain
| | - Leandro Peña
- Instituto de Biología Molecular y Celular de Plantas, Consejo Superior de Investigaciones Científicas (CSIC)-Universidad Politécnica de Valencia (UPV), Valencia, Spain
| | - Ricardo Flores
- Instituto de Biología Molecular y Celular de Plantas, Consejo Superior de Investigaciones Científicas (CSIC)-Universidad Politécnica de Valencia (UPV), Valencia, Spain.
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Fujita N, Komatsu K, Ayukawa Y, Matsuo Y, Hashimoto M, Netsu O, Teraoka T, Yamaji Y, Namba S, Arie T. N-terminal region of cysteine-rich protein (CRP) in carlaviruses is involved in the determination of symptom types. MOLECULAR PLANT PATHOLOGY 2018; 19:180-190. [PMID: 27868376 PMCID: PMC6638135 DOI: 10.1111/mpp.12513] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/04/2016] [Revised: 10/19/2016] [Accepted: 11/14/2016] [Indexed: 05/04/2023]
Abstract
Plant viruses in the genus Carlavirus include more than 65 members. Plants infected with carlaviruses exhibit various symptoms, including leaf malformation and plant stunting. Cysteine-rich protein (CRP) encoded by carlaviruses has been reported to be a pathogenicity determinant. Carlavirus CRPs contain two motifs in their central part: a nuclear localization signal (NLS) and a zinc finger motif (ZF). In addition to these two conserved motifs, carlavirus CRPs possess highly divergent, N-terminal, 34 amino acid residues with unknown function. In this study, to analyse the role of these distinct domains, we tested six carlavirus CRPs for their RNA silencing suppressor activity, ability to enhance the pathogenicity of a heterologous virus and effects on virus accumulation levels. Although all six tested carlavirus CRPs showed RNA silencing suppressor activity at similar levels, symptoms induced by the Potato virus X (PVX) heterogeneous system exhibited two different patterns: leaf malformation and whole-plant stunting. The expression of each carlavirus CRP enhanced PVX accumulation levels, which were not correlated with symptom patterns. PVX-expressing CRP with mutations in either NLS or ZF did not induce symptoms, suggesting that both motifs play critical roles in symptom expression. Further analysis using chimeric CRPs, in which the N-terminal region was replaced with the corresponding region of another CRP, suggested that the N-terminal region of carlavirus CRPs determined the exhibited symptom types. The up-regulation of a plant gene upp-L, which has been reported in a previous study, was also observed in this study; however, the expression level was not responsible for symptom types.
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Affiliation(s)
- Naoko Fujita
- Laboratory of Plant Pathology, Graduate School of AgricultureTokyo University of Agriculture and Technology (TUAT)183‐8509 FuchuJapan
- Laboratory of Plant Pathology, Department of Agricultural and Environmental Biology, Graduate School of Agricultural and Life SciencesThe University of Tokyo113‐8657 TokyoJapan
| | - Ken Komatsu
- Laboratory of Plant Pathology, Graduate School of AgricultureTokyo University of Agriculture and Technology (TUAT)183‐8509 FuchuJapan
| | - Yu Ayukawa
- Laboratory of Plant Pathology, Graduate School of AgricultureTokyo University of Agriculture and Technology (TUAT)183‐8509 FuchuJapan
- United Graduate School of Agricultural ScienceTokyo University of Agriculture and TechnologyFuchu183‐8509Japan
| | - Yuki Matsuo
- Laboratory of Plant Pathology, Graduate School of AgricultureTokyo University of Agriculture and Technology (TUAT)183‐8509 FuchuJapan
| | - Masayoshi Hashimoto
- Laboratory of Plant Pathology, Department of Agricultural and Environmental Biology, Graduate School of Agricultural and Life SciencesThe University of Tokyo113‐8657 TokyoJapan
| | - Osamu Netsu
- Laboratory of Plant Pathology, Department of Agricultural and Environmental Biology, Graduate School of Agricultural and Life SciencesThe University of Tokyo113‐8657 TokyoJapan
| | - Tohru Teraoka
- Laboratory of Plant Pathology, Graduate School of AgricultureTokyo University of Agriculture and Technology (TUAT)183‐8509 FuchuJapan
| | - Yasuyuki Yamaji
- Laboratory of Plant Pathology, Department of Agricultural and Environmental Biology, Graduate School of Agricultural and Life SciencesThe University of Tokyo113‐8657 TokyoJapan
| | - Shigetou Namba
- Laboratory of Plant Pathology, Department of Agricultural and Environmental Biology, Graduate School of Agricultural and Life SciencesThe University of Tokyo113‐8657 TokyoJapan
| | - Tsutomu Arie
- Laboratory of Plant Pathology, Graduate School of AgricultureTokyo University of Agriculture and Technology (TUAT)183‐8509 FuchuJapan
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26
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Gómez‐Muñoz N, Velázquez K, Vives MC, Ruiz‐Ruiz S, Pina JA, Flores R, Moreno P, Guerri J. The resistance of sour orange to Citrus tristeza virus is mediated by both the salicylic acid and RNA silencing defence pathways. MOLECULAR PLANT PATHOLOGY 2017; 18:1253-1266. [PMID: 27588892 PMCID: PMC6638288 DOI: 10.1111/mpp.12488] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/14/2016] [Revised: 08/26/2016] [Accepted: 08/30/2016] [Indexed: 05/08/2023]
Abstract
Citrus tristeza virus (CTV) induces in the field the decline and death of citrus varieties grafted on sour orange (SO) rootstock, which has forced the use of alternative decline-tolerant rootstocks in affected countries, despite the highly desirable agronomic features of the SO rootstock. Declining citrus plants display phloem necrosis below the bud union. In addition, SO is minimally susceptible to CTV compared with other citrus varieties, suggesting partial resistance of SO to CTV. Here, by silencing different citrus genes with a Citrus leaf blotch virus-based vector, we have examined the implication of the RNA silencing and salicylic acid (SA) defence pathways in the resistance of SO to CTV. Silencing of the genes RDR1, NPR1 and DCL2/DCL4, associated with these defence pathways, enhanced virus spread and accumulation in SO plants in comparison with non-silenced controls, whereas silencing of the genes NPR3/NPR4, associated with the hypersensitive response, produced a slight decrease in CTV accumulation and reduced stunting of SO grafted on CTV-infected rough lemon plants. We also found that the CTV RNA silencing suppressors p20 and p23 also suppress the SA signalling defence, with the suppressor activity being higher in the most virulent isolates.
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Affiliation(s)
- Neus Gómez‐Muñoz
- Instituto Valenciano de Investigaciones Agrarias (IVIA)Centro de Protección Vegetal y BiotecnologíaMoncada, Valencia46113Spain
| | - Karelia Velázquez
- Instituto Valenciano de Investigaciones Agrarias (IVIA)Centro de Protección Vegetal y BiotecnologíaMoncada, Valencia46113Spain
| | - María Carmen Vives
- Instituto Valenciano de Investigaciones Agrarias (IVIA)Centro de Protección Vegetal y BiotecnologíaMoncada, Valencia46113Spain
| | - Susana Ruiz‐Ruiz
- Instituto Valenciano de Investigaciones Agrarias (IVIA)Centro de Protección Vegetal y BiotecnologíaMoncada, Valencia46113Spain
| | - José Antonio Pina
- Instituto Valenciano de Investigaciones Agrarias (IVIA)Centro de Protección Vegetal y BiotecnologíaMoncada, Valencia46113Spain
| | - Ricardo Flores
- Instituto de Biología Molecular y Celular de Plantas (UPV‐CSIC), Universidad Politécnica de Valencia, Avenida de los NaranjosValencia46022Spain
| | - Pedro Moreno
- Instituto Valenciano de Investigaciones Agrarias (IVIA)Centro de Protección Vegetal y BiotecnologíaMoncada, Valencia46113Spain
| | - José Guerri
- Instituto Valenciano de Investigaciones Agrarias (IVIA)Centro de Protección Vegetal y BiotecnologíaMoncada, Valencia46113Spain
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27
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Soler N, Fagoaga C, López C, Moreno P, Navarro L, Flores R, Peña L. Symptoms induced by transgenic expression of p23 from Citrus tristeza virus in phloem-associated cells of Mexican lime mimic virus infection without the aberrations accompanying constitutive expression. MOLECULAR PLANT PATHOLOGY 2015; 16:388-99. [PMID: 25171669 PMCID: PMC6638416 DOI: 10.1111/mpp.12188] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/19/2023]
Abstract
Citrus tristeza virus (CTV) is phloem restricted in natural citrus hosts. The 23-kDa protein (p23) encoded by the virus is an RNA silencing suppressor and a pathogenicity determinant. The expression of p23, or its N-terminal 157-amino-acid fragment comprising the zinc finger and flanking basic motifs, driven by the constitutive 35S promoter of cauliflower mosaic virus, induces CTV-like symptoms and other aberrations in transgenic citrus. To better define the role of p23 in CTV pathogenesis, we compared the phenotypes of Mexican lime transformed with p23-derived transgenes from the severe T36 and mild T317 CTV isolates under the control of the phloem-specific promoter from Commelina yellow mottle virus (CoYMV) or the 35S promoter. Expression of the constructs restricted to the phloem induced a phenotype resembling CTV-specific symptoms (vein clearing and necrosis, and stem pitting), but not the non-specific aberrations (such as mature leaf epinasty and yellow pinpoints, growth cessation and apical necrosis) observed when p23 was ectopically expressed. Furthermore, vein necrosis and stem pitting in Mexican lime appeared to be specifically associated with p23 from T36. Phloem-specific accumulation of the p23Δ158-209(T36) fragment was sufficient to induce the same anomalies, indicating that the region comprising the N-terminal 157 amino acids of p23 is responsible (at least in part) for the vein clearing, stem pitting and, possibly, vein corking in this host.
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Affiliation(s)
- Nuria Soler
- Centro de Protección Vegetal y Biotecnología, Instituto Valenciano de Investigaciones Agrarias (IVIA), Apdo. Oficial, Moncada, Valencia, 46113, Spain
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28
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Deng XG, Peng XJ, Zhu F, Chen YJ, Zhu T, Qin SB, Xi DH, Lin HH. A critical domain of Sweet potato chlorotic fleck virus nucleotide-binding protein (NaBp) for RNA silencing suppression, nuclear localization and viral pathogenesis. MOLECULAR PLANT PATHOLOGY 2015; 16:365-75. [PMID: 25138489 PMCID: PMC6638403 DOI: 10.1111/mpp.12186] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
RNA silencing is an important mechanism of antiviral defence in plants. To counteract this resistance mechanism, many viruses have evolved RNA silencing suppressors. In this study, we analysed five proteins encoded by Sweet potato chlorotic fleck virus (SPCFV) for their abilities to suppress RNA silencing using a green fluorescent protein (GFP)-based transient expression assay in Nicotiana benthamiana line 16c plants. Our results showed that a putative nucleotide-binding protein (NaBp), but not other proteins encoded by the virus, could efficiently suppress local and systemic RNA silencing induced by either sense or double-stranded RNA (dsRNA) molecules. Deletion mutation analysis of NaBp demonstrated that the basic motif (an arginine-rich region) was critical for its RNA silencing suppression activity. Using confocal laser scanning microscopy imaging of transfected protoplasts expressing NaBp fused to GFP, we showed that NaBp accumulated predominantly in the nucleus. Mutational analysis of NaBp demonstrated that the basic motif represented part of the nuclear localization signal. In addition, we demonstrated that the basic motif in NaBp was a pathogenicity determinant in the Potato virus X (PVX) heterogeneous system. Overall, our results demonstrate that the basic motif of SPCFV NaBp plays a critical role in RNA silencing suppression, nuclear localization and viral pathogenesis.
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Affiliation(s)
- Xing-Guang Deng
- Ministry of Education Key Laboratory for Bio-Resource and Eco-Environment, College of Life Science, State Key Laboratory of Hydraulics and Mountain River Engineering, Sichuan University, Chengdu, Sichuan, 610064, China
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29
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Csorba T, Kontra L, Burgyán J. viral silencing suppressors: Tools forged to fine-tune host-pathogen coexistence. Virology 2015; 479-480:85-103. [DOI: 10.1016/j.virol.2015.02.028] [Citation(s) in RCA: 368] [Impact Index Per Article: 40.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2014] [Revised: 01/31/2015] [Accepted: 02/16/2015] [Indexed: 12/27/2022]
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30
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Viroids, the simplest RNA replicons: How they manipulate their hosts for being propagated and how their hosts react for containing the infection. Virus Res 2015; 209:136-45. [PMID: 25738582 DOI: 10.1016/j.virusres.2015.02.027] [Citation(s) in RCA: 66] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2014] [Revised: 02/23/2015] [Accepted: 02/23/2015] [Indexed: 12/31/2022]
Abstract
The discovery of viroids about 45 years ago heralded a revolution in Biology: small RNAs comprising around 350 nt were found to be able to replicate autonomously-and to incite diseases in certain plants-without encoding proteins, fundamental properties discriminating these infectious agents from viruses. The initial focus on the pathological effects usually accompanying infection by viroids soon shifted to their molecular features-they are circular molecules that fold upon themselves adopting compact secondary conformations-and then to how they manipulate their hosts to be propagated. Replication of viroids-in the nucleus or chloroplasts through a rolling-circle mechanism involving polymerization, cleavage and circularization of RNA strands-dealt three surprises: (i) certain RNA polymerases are redirected to accept RNA instead of their DNA templates, (ii) cleavage in chloroplastic viroids is not mediated by host enzymes but by hammerhead ribozymes, and (iii) circularization in nuclear viroids is catalyzed by a DNA ligase redirected to act upon RNA substrates. These enzymes (and ribozymes) are most probably assisted by host proteins, including transcription factors and RNA chaperones. Movement of viroids, first intracellularly and then to adjacent cells and distal plant parts, has turned out to be a tightly regulated process in which specific RNA structural motifs play a crucial role. More recently, the advent of RNA silencing has brought new views on how viroids may cause disease and on how their hosts react to contain the infection; additionally, viroid infection may be restricted by other mechanisms. Representing the lowest step on the biological size scale, viroids have also attracted considerable interest to get a tentative picture of the essential characteristics of the primitive replicons that populated the postulated RNA world.
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31
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Dawson WO, Bar-Joseph M, Garnsey SM, Moreno P. Citrus tristeza virus: making an ally from an enemy. ANNUAL REVIEW OF PHYTOPATHOLOGY 2015; 53:137-55. [PMID: 25973695 DOI: 10.1146/annurev-phyto-080614-120012] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
Virus diseases of perennial trees and vines have characteristics not amenable to study using small model annual plants. Unique disease symptoms such as graft incompatibilities and stem pitting cause considerable crop losses. Also, viruses in these long-living plants tend to accumulate complex populations of viruses and strains. Considerable progress has been made in understanding the biology and genetics of Citrus tristeza virus (CTV) and in developing it into a tool for crop protection and improvement. The diseases in tree and vine crops have commonalities for which CTV can be used to develop a baseline. The purpose of this review is to provide a necessary background of systems and reagents developed for CTV that can be used for continued progress in this area and to point out the value of the CTV-citrus system in answering important questions on plant-virus interactions and developing new methods for controlling plant diseases.
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Affiliation(s)
- William O Dawson
- Department of Plant Pathology, Citrus Research and Education Center, University of Florida, Lake Alfred, Florida 33850; ,
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32
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Rossi M, Vallino M, Abbà S, Ciuffo M, Balestrini R, Genre A, Turina M. The Importance of the KR-Rich Region of the Coat Protein of Ourmia melon virus for Host Specificity, Tissue Tropism, and Interference With Antiviral Defense. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2015; 28:30-41. [PMID: 25494356 DOI: 10.1094/mpmi-07-14-0197-r] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
The N-terminal region of the Ourmia melon virus (OuMV) coat protein (CP) contains a short lysine/arginine-rich (KR) region. By alanine scanning mutagenesis, we showed that the KR region influences pathogenicity and virulence of OuMV without altering viral particle assembly. A mutant, called OuMV6710, with three basic residue substitutions in the KR region, was impaired in the ability to maintain the initial systemic infection in Nicotiana benthamiana and to infect both cucumber and melon plants systemically. The integrity of this protein region was also crucial for encapsidation of viral genomic RNA; in fact, certain mutations within the KR region partially compromised the RNA encapsidation efficiency of the CP. In Arabidopsis thaliana Col-0, OuMV6710 was impaired in particle accumulation; however, this phenotype was abolished in dcl2/dcl4 and dcl2/dcl3/dcl4 Arabidopsis mutants defective for antiviral silencing. Moreover, in contrast to CPwt, in situ immunolocalization experiments indicated that CP6710 accumulates efficiently in the spongy mesophyll tissue of infected N. benthamiana and A. thaliana leaves but only occasionally infects palisade tissues. These results provided strong evidence of a crucial role for OuMV CP during viral infection and highlighted the relevance of the KR region in determining tissue tropism, host range, pathogenicity, and RNA affinity, which may be all correlated with a possible CP silencing-suppression activity.
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33
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Pérez-Cañamás M, Hernández C. Key importance of small RNA binding for the activity of a glycine-tryptophan (GW) motif-containing viral suppressor of RNA silencing. J Biol Chem 2014; 290:3106-20. [PMID: 25505185 DOI: 10.1074/jbc.m114.593707] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Viruses express viral suppressors of RNA silencing (VSRs) to counteract RNA silencing-based host defenses. Although virtually all stages of the antiviral silencing pathway can be inhibited by VSRs, small RNAs (sRNAs) and Argonaute (AGO) proteins seem to be the most frequent targets. Recently, GW/WG motifs of some VSRs have been proposed to dictate their suppressor function by mediating interaction with AGO(s). Here we have studied the VSR encoded by Pelargonium line pattern virus (family Tombusviridae). The results show that p37, the viral coat protein, blocks RNA silencing. Site-directed mutagenesis of some p37 sequence traits, including a conserved GW motif, allowed generation of suppressor-competent and -incompetent molecules and uncoupling of the VSR and particle assembly capacities. The engineered mutants were used to assess the importance of p37 functions for viral infection and the relative contribution of diverse molecular interactions to suppressor activity. Two main conclusions can be drawn: (i) the silencing suppression and encapsidation functions of p37 are both required for systemic Pelargonium line pattern virus infection, and (ii) the suppressor activity of p37 relies on the ability to bind sRNAs rather than on interaction with AGOs. The data also caution against potential misinterpretations of results due to overlap of sequence signals related to distinct protein properties. This is well illustrated by mutation of the GW motif in p37 that concurrently affects nucleolar localization, efficient interaction with AGO1, and sRNA binding capability. These concomitant effects could have been overlooked in other GW motif-containing suppressors, as we exemplify with the orthologous p38 of turnip crinkle virus.
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Affiliation(s)
- Miryam Pérez-Cañamás
- From the Instituto de Biología Molecular y Celular de Plantas (Consejo Superior de Investigaciones Científicas-Universidad Politécnica de Valencia), Ciudad Politécnica de la Innovación, Ed. 8E. Camino de Vera s/n, 46022 Valencia, Spain
| | - Carmen Hernández
- From the Instituto de Biología Molecular y Celular de Plantas (Consejo Superior de Investigaciones Científicas-Universidad Politécnica de Valencia), Ciudad Politécnica de la Innovación, Ed. 8E. Camino de Vera s/n, 46022 Valencia, Spain
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34
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Nchongboh CG, Wu GW, Hong N, Wang GP. Protein–protein interactions between proteins of Citrus tristeza virus isolates. Virus Genes 2014; 49:456-65. [DOI: 10.1007/s11262-014-1100-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2014] [Accepted: 06/20/2014] [Indexed: 12/01/2022]
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35
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Rossi M, Genre A, Turina M. Genetic dissection of a putative nucleolar localization signal in the coat protein of ourmia melon virus. Arch Virol 2014; 159:1187-92. [PMID: 24248258 DOI: 10.1007/s00705-013-1923-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2013] [Accepted: 11/07/2013] [Indexed: 10/26/2022]
Abstract
Ourmiaviruses became the object of recent attention for their unusual taxonomic placements among plant viruses. The ourmia melon virus (OuMV) RNA3 encodes a 22-kDa coat protein (CP). Besides its role in virion formation, the OuMV CP facilitates systemic virus spread. In Nicotiana benthamiana, an eGFP-CP fusion protein was localized in the nucleus and preferentially in the nucleolus. By bioinformatics analysis, we identified an arginine- and lysine-rich region at the N-terminus of the CP. Here, we demonstrate by deletion and alanine scanning mutagenesis that this region in the CP is responsible for its preferential accumulation in the nucleolus of host cells.
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Affiliation(s)
- M Rossi
- Sez. di Torino, CNR, Istituto di Virologia Vegetale, Strada delle Cacce 73, 10135, Torino, Italy
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36
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Serra P, Bani Hashemian SM, Fagoaga C, Romero J, Ruiz-Ruiz S, Gorris MT, Bertolini E, Duran-Vila N. Virus-viroid interactions: Citrus Tristeza Virus enhances the accumulation of Citrus Dwarfing Viroid in Mexican lime via virus-encoded silencing suppressors. J Virol 2014; 88:1394-7. [PMID: 24227850 PMCID: PMC3911637 DOI: 10.1128/jvi.02619-13] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2013] [Accepted: 11/08/2013] [Indexed: 11/20/2022] Open
Abstract
An assay to identify interactions between Citrus Dwarfing Viroid (CDVd) and Citrus Tristeza Virus (CTV) showed that viroid titer was enhanced by the coinfecting CTV in Mexican lime but not in etrog citron. Since CTV encodes three RNA silencing suppressors (RSSs), p23, p20 and p25, an assay using transgenic Mexican limes expressing each RSS revealed that p23 and, to a lesser extent, p25 recapitulated the effect observed with coinfections of CTV and CDVd.
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Affiliation(s)
- Pedro Serra
- Centro de Protección Vegetal y Biotecnología, Instituto Valenciano de Investigaciones Agrarias, Moncada, Valencia, Spain
- Instituto de Biología Molecular y Celular de Plantas (UPV-CSIC), Valencia, Spain
| | - Seyed M. Bani Hashemian
- Centro de Protección Vegetal y Biotecnología, Instituto Valenciano de Investigaciones Agrarias, Moncada, Valencia, Spain
- Iran Citrus Research Institute, Ramsar, Iran
| | - Carmen Fagoaga
- Centro de Protección Vegetal y Biotecnología, Instituto Valenciano de Investigaciones Agrarias, Moncada, Valencia, Spain
| | - Juan Romero
- Centro de Protección Vegetal y Biotecnología, Instituto Valenciano de Investigaciones Agrarias, Moncada, Valencia, Spain
| | - Susana Ruiz-Ruiz
- Instituto de Biología Molecular y Celular de Plantas (UPV-CSIC), Valencia, Spain
| | - Maria T. Gorris
- Centro de Protección Vegetal y Biotecnología, Instituto Valenciano de Investigaciones Agrarias, Moncada, Valencia, Spain
| | - Edson Bertolini
- Centro de Protección Vegetal y Biotecnología, Instituto Valenciano de Investigaciones Agrarias, Moncada, Valencia, Spain
| | - Núria Duran-Vila
- Centro de Protección Vegetal y Biotecnología, Instituto Valenciano de Investigaciones Agrarias, Moncada, Valencia, Spain
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Flores R, Ruiz-Ruiz S, Soler N, Sánchez-Navarro J, Fagoaga C, López C, Navarro L, Moreno P, Peña L. Citrus tristeza virus p23: a unique protein mediating key virus-host interactions. Front Microbiol 2013; 4:98. [PMID: 23653624 PMCID: PMC3642503 DOI: 10.3389/fmicb.2013.00098] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2013] [Accepted: 04/06/2013] [Indexed: 11/13/2022] Open
Abstract
The large RNA genome of Citrus tristeza virus (CTV; ca. 20 kb) contains 12 open reading frames, with the 3′-terminal one corresponding to a protein of 209 amino acids (p23) that is expressed from an abundant subgenomic RNA. p23, an RNA-binding protein with a putative zinc-finger domain and some basic motifs, is unique to CTV because no homologs have been found in other closteroviruses, including the type species of the genus Beet yellows virus (despite both viruses having many homologous genes). Consequently, p23 might have evolved for the specific interaction of CTV with its citrus hosts. From a functional perspective p23 has been involved in many roles: (i) regulation of the asymmetrical accumulation of CTV RNA strands, (ii) induction of the seedling yellows syndrome in sour orange and grapefruit, (iii) intracellular suppression of RNA silencing, (iv) elicitation of CTV-like symptoms when expressed ectopically as a transgene in several Citrus spp., and (v) enhancement of systemic infection (and virus accumulation) in sour orange and CTV release from the phloem in p23-expressing transgenic sweet and sour orange. Moreover, transformation of Mexican lime with intron-hairpin constructs designed for the co-inactivation of p23 and the two other CTV silencing suppressors results in complete resistance against the homologous virus. From a cellular point of view, recent data indicate that p23 accumulates preferentially in the nucleolus, being the first closterovirus protein with such a subcellular localization, as well as in plasmodesmata. These major accumulation sites most likely determine some of the functional roles of p23.
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Affiliation(s)
- Ricardo Flores
- Instituto de Biología Molecular y Celular de Plantas, Consejo Superior de investigaciones Científicas-Universidad Politécnica de Valencia Valencia, Spain
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