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Crawshaw S, Murphy AM, Rowling PJE, Nietlispach D, Itzhaki LS, Carr JP. Investigating the Interactions of the Cucumber Mosaic Virus 2b Protein with the Viral 1a Replicase Component and the Cellular RNA Silencing Factor Argonaute 1. Viruses 2024; 16:676. [PMID: 38793558 PMCID: PMC11125589 DOI: 10.3390/v16050676] [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: 03/16/2024] [Revised: 04/13/2024] [Accepted: 04/16/2024] [Indexed: 05/26/2024] Open
Abstract
The cucumber mosaic virus (CMV) 2b protein is a suppressor of plant defenses and a pathogenicity determinant. Amongst the 2b protein's host targets is the RNA silencing factor Argonaute 1 (AGO1), which it binds to and inhibits. In Arabidopsis thaliana, if 2b-induced inhibition of AGO1 is too efficient, it induces reinforcement of antiviral silencing by AGO2 and triggers increased resistance against aphids, CMV's insect vectors. These effects would be deleterious to CMV replication and transmission, respectively, but are moderated by the CMV 1a protein, which sequesters sufficient 2b protein molecules into P-bodies to prevent excessive inhibition of AGO1. Mutant 2b protein variants were generated, and red and green fluorescent protein fusions were used to investigate subcellular colocalization with AGO1 and the 1a protein. The effects of mutations on complex formation with the 1a protein and AGO1 were investigated using bimolecular fluorescence complementation and co-immunoprecipitation assays. Although we found that residues 56-60 influenced the 2b protein's interactions with the 1a protein and AGO1, it appears unlikely that any single residue or sequence domain is solely responsible. In silico predictions of intrinsic disorder within the 2b protein secondary structure were supported by circular dichroism (CD) but not by nuclear magnetic resonance (NMR) spectroscopy. Intrinsic disorder provides a plausible model to explain the 2b protein's ability to interact with AGO1, the 1a protein, and other factors. However, the reasons for the conflicting conclusions provided by CD and NMR must first be resolved.
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Affiliation(s)
- Sam Crawshaw
- Department of Plant Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EA, UK; (S.C.); (A.M.M.)
| | - Alex M. Murphy
- Department of Plant Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EA, UK; (S.C.); (A.M.M.)
| | - Pamela J. E. Rowling
- Department of Pharmacology, University of Cambridge, Tennis Court Rd., Cambridge CB2 1PD, UK; (P.J.E.R.); (L.S.I.)
| | - Daniel Nietlispach
- Department of Biochemistry, University of Cambridge, Sanger Building, 80 Tennis Court Rd., Cambridge CB2 1GA, UK;
| | - Laura S. Itzhaki
- Department of Pharmacology, University of Cambridge, Tennis Court Rd., Cambridge CB2 1PD, UK; (P.J.E.R.); (L.S.I.)
| | - John P. Carr
- Department of Plant Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EA, UK; (S.C.); (A.M.M.)
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Kumari R, Kumar S, Leibman D, Abebie B, Shnaider Y, Ding S, Gal‐On A. Cucumber RDR1s and cucumber mosaic virus suppressor protein 2b association directs host defence in cucumber plants. MOLECULAR PLANT PATHOLOGY 2021; 22:1317-1331. [PMID: 34355485 PMCID: PMC8518566 DOI: 10.1111/mpp.13112] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/23/2021] [Revised: 07/03/2021] [Accepted: 07/05/2021] [Indexed: 05/27/2023]
Abstract
RNA-dependent RNA polymerases (RDRs) regulate important aspects of plant development and resistance to pathogens. The role of RDRs in virus resistance has been demonstrated using siRNA signal amplification and through the methylation of viral genomes. Cucumber (Cucumis sativus) has four RDR1 genes that are differentially induced during virus infection: CsRDR1a, CsRDR1b, and duplicated CsRDR1c1/c2. The mode of action of CsRDR1s during viral infection is unknown. Transient expression of the cucumber mosaic virus (CMV)-2b protein (the viral suppressor of RNA silencing) in cucumber protoplasts induced the expression of CsRDR1c, but not of CsRDR1a/1b. Results from the yeast two-hybrid system showed that CsRDR1 proteins interacted with CMV-2b and this was confirmed by bimolecular fluorescence complementation assays. In protoplasts, CsRDR1s localized in the cytoplasm as punctate spots. Colocalization experiments revealed that CsRDR1s and CMV-2b were uniformly dispersed throughout the cytoplasm, suggesting that CsRDR1s are redistributed as a result of interactions. Transient overexpression of individual CsRDR1a/1b genes in protoplasts reduced CMV accumulation, indicating their antiviral role. However, overexpression of CsRDR1c in protoplasts resulted in relatively higher accumulation of CMV and CMVΔ2b. In single cells, CsRDR1c enhances viral replication, leading to CMV accumulation and blocking secondary siRNA amplification of CsRDR1c by CMV-2b protein. This suggests that CMV-2b acts as both a transcription factor that induces CsRDR1c (controlling virus accumulation) and a suppressor of CsRDR1c activity.
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Affiliation(s)
- Reenu Kumari
- Department of Plant Pathology and Weed ResearchAgricultural Research OrganizationRishon LeZionIsrael
- College of Horticulture and ForestryDr YS Parmar University of Horticulture and ForestryMandiIndia
| | - Surender Kumar
- Department of Plant Pathology and Weed ResearchAgricultural Research OrganizationRishon LeZionIsrael
- Plant Virology Lab, Biotechnology DivisionCSIR‐Institute of Himalayan Bioresource TechnologyPalampurIndia
| | - Diana Leibman
- Department of Plant Pathology and Weed ResearchAgricultural Research OrganizationRishon LeZionIsrael
| | - Bekele Abebie
- Department of Plant Pathology and Weed ResearchAgricultural Research OrganizationRishon LeZionIsrael
| | - Yulia Shnaider
- Department of Plant Pathology and Weed ResearchAgricultural Research OrganizationRishon LeZionIsrael
| | - Shou‐Wei Ding
- Department of Plant Pathology and Microbiology & Institute for Integrative Genome BiologyUniversity of CaliforniaRiversideCaliforniaUSA
| | - Amit Gal‐On
- Department of Plant Pathology and Weed ResearchAgricultural Research OrganizationRishon LeZionIsrael
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Salánki K, Gellért Á, Nemes K, Divéki Z, Balázs E. Molecular Modeling for Better Understanding of Cucumovirus Pathology. Adv Virus Res 2018; 102:59-88. [PMID: 30266176 DOI: 10.1016/bs.aivir.2018.06.002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Abstract
Cucumber mosaic virus (CMV) is a small RNA virus capable of infecting a wide variety of plant species. The high economic losses due to the CMV infection made this virus a relevant subject of scientific studies, which were further facilitated by the small size of the viral genome. Hence, CMV also became a model organism to investigate the molecular mechanism of pathogenesis. All viral functions are dependent on intra- and intermolecular interactions between nucleic acids and proteins of the virus and the host. This review summarizes the recent data on molecular determinants of such interactions. A particular emphasis is given to the results obtained by utilizing molecular-based planning and modeling techniques.
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Affiliation(s)
- Katalin Salánki
- MTA ATK, Plant Protection Institute, Centre for Agricultural Research, Hungarian Academy of Sciences, Budapest, Hungary
| | - Ákos Gellért
- MTA ATK, Institute for Veterinary Medical Research, Centre for Agricultural Research, Hungarian Academy of Sciences, Budapest, Hungary
| | - Katalin Nemes
- MTA ATK, Plant Protection Institute, Centre for Agricultural Research, Hungarian Academy of Sciences, Budapest, Hungary
| | - Zoltán Divéki
- MTA ATK, Agricultural Institute, Centre for Agricultural Research, Hungarian Academy of Sciences, Budapest, Hungary
| | - Ervin Balázs
- MTA ATK, Agricultural Institute, Centre for Agricultural Research, Hungarian Academy of Sciences, Budapest, Hungary.
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Nemes K, Gellért Á, Balázs E, Salánki K. Alanine scanning of cucumber mosaic virus (CMV) 2b protein identifies different positions for cell-to-cell movement and gene silencing suppressor activity. PLoS One 2014; 9:e112095. [PMID: 25380036 PMCID: PMC4224413 DOI: 10.1371/journal.pone.0112095] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2014] [Accepted: 10/06/2014] [Indexed: 12/29/2022] Open
Abstract
The multifunctional 2b protein of CMV has a role in the long distance and local movement of the virus, in symptom formation, in evasion of defense mediated by salicylic acid as well as in suppression of RNA silencing. The role of conserved amino acid sequence domains were analyzed previously in the protein function, but comprehensive analysis of this protein was not carried out until recently. We have analyzed all over the 2b protein by alanine scanning mutagenesis changing three consecutive amino acids (aa) to alanine. We have identified eight aa triplets as key determinants of the 2b protein function in virus infection. Four of them (KKQ/22-24/AAA, QNR/31-33/AAA, RER/34-36/AAA, SPS/40-42/AAA) overlap with previously determined regions indispensable in gene silencing suppressor function. We have identified two additional triplets necessary for the suppressor function of the 2b protein (LPF/55-57/AAA, NVE/10-12/AAA), and two other positions were required for cell-to-cell movement of the virus (MEL/1-3/AAA, RHV/70-72/AAA), which are not essential for suppressor activity.
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Affiliation(s)
- Katalin Nemes
- Plant Protection Institute, Centre for Agricultural Research, Hungarian Academy of Sciences, Budapest, Hungary
- Department of Plant Pathology, Corvinus University of Budapest, Budapest, Hungary
| | - Ákos Gellért
- Agricultural Institute, Centre for Agricultural Research, Hungarian Academy of Sciences Department of Applied Genomics, Martonvásár, Hungary
| | - Ervin Balázs
- Agricultural Institute, Centre for Agricultural Research, Hungarian Academy of Sciences Department of Applied Genomics, Martonvásár, Hungary
| | - Katalin Salánki
- Plant Protection Institute, Centre for Agricultural Research, Hungarian Academy of Sciences, Budapest, Hungary
- Agricultural Biotechnology Center, Gödöllő, Hungary
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Zhou T, Murphy AM, Lewsey MG, Westwood JH, Zhang HM, González I, Canto T, Carr JP. Domains of the cucumber mosaic virus 2b silencing suppressor protein affecting inhibition of salicylic acid-induced resistance and priming of salicylic acid accumulation during infection. J Gen Virol 2014; 95:1408-1413. [PMID: 24633701 PMCID: PMC4027040 DOI: 10.1099/vir.0.063461-0] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2014] [Accepted: 03/13/2014] [Indexed: 11/18/2022] Open
Abstract
The cucumber mosaic virus (CMV) 2b silencing suppressor protein allows the virus to overcome resistance to replication and local movement in inoculated leaves of plants treated with salicylic acid (SA), a resistance-inducing plant hormone. In Arabidopsis thaliana plants systemically infected with CMV, the 2b protein also primes the induction of SA biosynthesis during this compatible interaction. We found that CMV infection of susceptible tobacco (Nicotiana tabacum) also induced SA accumulation. Utilization of mutant 2b proteins expressed during infection of tobacco showed that the N- and C-terminal domains, which had previously been implicated in regulation of symptom induction, were both required for subversion of SA-induced resistance, while all mutants tested except those affecting the putative phosphorylation domain had lost the ability to prime SA accumulation and expression of the SA-induced marker gene PR-1.
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Affiliation(s)
- Tao Zhou
- Department of Plant Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EA, UK
- Department of Plant Pathology, China Agricultural University, 2 Yuanmingyuan West Rd, Beijing 100193, PR China
| | - Alex M. Murphy
- Department of Plant Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EA, UK
| | - Mathew G. Lewsey
- Department of Plant Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EA, UK
| | - Jack H. Westwood
- Department of Plant Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EA, UK
| | - Heng-Mu Zhang
- Department of Plant Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EA, UK
- State Key Laboratory Breeding Base for Zhejiang Sustainable Pest and Disease Control, Institute of Virology and Biotechnology, Zhejiang Academy of Agricultural Sciences, 198 Shiqiao Rd, Hangzhou 310021, Zhejiang, PR China
| | - Inmaculada González
- Department of Plant Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EA, UK
- Centro de Investigaciones Biológicas, CIB, CSIC, Ramiro de Maeztu 9, 28040 Madrid, Spain
| | - Tomás Canto
- Centro de Investigaciones Biológicas, CIB, CSIC, Ramiro de Maeztu 9, 28040 Madrid, Spain
| | - John P. Carr
- Department of Plant Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EA, UK
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