1
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Wang L, Li H, Lei Z, Jeong DH, Cho J. The CARBON CATABOLITE REPRESSION 4A-mediated RNA deadenylation pathway acts on the transposon RNAs that are not regulated by small RNAs. THE NEW PHYTOLOGIST 2024; 241:1636-1645. [PMID: 38009859 DOI: 10.1111/nph.19435] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/24/2023] [Accepted: 11/13/2023] [Indexed: 11/29/2023]
Abstract
Transposable elements (TEs) are mobile genetic elements that can impair the host genome stability and integrity. It has been well documented that activated transposons in plants are suppressed by small interfering (si) RNAs. However, transposon repression by the cytoplasmic RNA surveillance system is unknown. Here, we show that mRNA deadenylation is critical for controlling transposons in Arabidopsis. Trimming of poly(A) tail is a rate-limiting step that precedes the RNA decay and is primarily mediated by the CARBON CATABOLITE REPRESSION 4 (CCR4)-NEGATIVE ON TATA-LESS (NOT) complex. We found that the loss of CCR4a leads to strong derepression and mobilization of TEs in Arabidopsis. Intriguingly, CCR4a regulates a largely distinct set of TEs from those controlled by RNA-dependent RNA Polymerase 6 (RDR6), a key enzyme that produces cytoplasmic siRNAs. This indicates that the cytoplasmic RNA quality control mechanism targets the TEs that are poorly recognized by the previously well-characterized RDR6-mediated pathway, and thereby augments the host genome stability. Our study suggests a hitherto unknown mechanism for transposon repression mediated by RNA deadenylation and unveils a complex nature of the host's strategy to maintain the genome integrity.
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Affiliation(s)
- Ling Wang
- National Key Laboratory of Plant Molecular Genetics, CAS Center for Excellence in Molecular Plant Sciences, Shanghai Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Shanghai, 200032, China
- University of Chinese Academy of Science, Beijing, 100049, China
| | - Hui Li
- National Key Laboratory of Plant Molecular Genetics, CAS Center for Excellence in Molecular Plant Sciences, Shanghai Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Shanghai, 200032, China
- University of Chinese Academy of Science, Beijing, 100049, China
| | - Zhen Lei
- National Key Laboratory of Plant Molecular Genetics, CAS Center for Excellence in Molecular Plant Sciences, Shanghai Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Shanghai, 200032, China
- University of Chinese Academy of Science, Beijing, 100049, China
| | - Dong-Hoon Jeong
- Department of Life Science, Hallym University, Chuncheon, 24252, Korea
- Multidisciplinary Genome Institute, Hallym University, Chuncheon, 24252, Korea
| | - Jungnam Cho
- Department of Biosciences, Durham University, Durham, DH1 3LE, UK
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2
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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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3
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Kim YJ. Crosstalk between RNA silencing and RNA quality control in plants. BMB Rep 2023; 56:321-325. [PMID: 37156633 PMCID: PMC10315563 DOI: 10.5483/bmbrep.2023-0049] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2023] [Revised: 04/20/2023] [Accepted: 05/04/2023] [Indexed: 06/06/2024] Open
Abstract
RNAs are pivotal molecules acting as messengers of genetic information and regulatory molecules for cellular development and survival. From birth to death, RNAs face constant cellular decision for the precise control of cellular function and activity. Most eukaryotic cells employ conserved machineries for RNA decay including RNA silencing and RNA quality control (RQC). In plants, RQC monitors endogenous RNAs and degrades aberrant and dysfunctional species, whereas RNA silencing promotes RNA degradation to repress the expression of selected endogenous RNAs or exogenous RNA derived from transgenes and virus. Interestingly, emerging evidences have indicated that RQC and RNA silencing interact with each by sharing target RNAs and regulatory components. Such interaction should be tightly organized for proper cellular survival. However, it is still elusive that how each machinery specifically recognizes target RNAs. In this review, we summarize recent advances on RNA silencing and RQC pathway and discuss potential mechanisms underlying the interaction between the two machineries. [BMB Reports 2023; 56(6): 321-325].
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Affiliation(s)
- Yun Ju Kim
- Department of Systems Biology, Yonsei University, Seoul 03722, Korea
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4
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Bazin J, Elvira-Matelot E, Blein T, Jauvion V, Bouteiller N, Cao J, Crespi MD, Vaucheret H. Synergistic action of the Arabidopsis spliceosome components PRP39a and SmD1b in promoting posttranscriptional transgene silencing. THE PLANT CELL 2023; 35:1917-1935. [PMID: 36970782 PMCID: PMC10226559 DOI: 10.1093/plcell/koad091] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/10/2022] [Revised: 03/03/2023] [Accepted: 03/07/2023] [Indexed: 05/30/2023]
Abstract
Besides regulating splicing, the conserved spliceosome component SmD1 (Small nuclear ribonucleoprotein D1)b promotes posttranscriptional silencing of sense transgenes (S-PTGS [post-transcriptional genesilencing]). Here, we show that the conserved spliceosome component PRP39 (Pre-mRNA-processing factor 39)a also plays a role in S-PTGS in Arabidopsis thaliana. However, PRP39a and SmD1b actions appear distinct in both splicing and S-PTGS. Indeed, RNAseq-based analysis of expression level and alternative splicing in prp39a and smd1b mutants identified different sets of deregulated transcripts and noncoding RNAs. Moreover, double mutant analyses involving prp39a or smd1b and RNA quality control (RQC) mutants revealed distinct genetic interactions for SmD1b and PRP39a with nuclear RQC machineries, suggesting nonredundant roles in the RQC/PTGS interplay. Supporting this hypothesis, a prp39a smd1b double mutant exhibited enhanced suppression of S-PTGS compared to the single mutants. Because the prp39a and smd1b mutants (i) showed no major changes in the expression of PTGS or RQC components or in small RNA production and (ii) do not alter PTGS triggered by inverted-repeat transgenes directly producing dsRNA (IR-PTGS), PRP39a, and SmD1b appear to synergistically promote a step specific to S-PTGS. We propose that, independently from their specific roles in splicing, PRP39a and SmD1b limit 3'-to-5' and/or 5'-to-3' degradation of transgene-derived aberrant RNAs in the nucleus, thus favoring the export of aberrant RNAs to the cytoplasm where their conversion into double-stranded RNA (dsRNA) initiates S-PTGS.
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Affiliation(s)
- Jérémie Bazin
- Institute of Plant Sciences Paris-Saclay (IPS2), CNRS, INRAE, Universités Paris-Sud, Evry, Paris-Diderot, Sorbonne Paris-Cité, Paris-Saclay, Bâtiment 630, 91405 Orsay, France
| | - Emilie Elvira-Matelot
- Université Paris-Saclay, INRAE, AgroParisTech, Institut Jean-Pierre Bourgin (IJPB), 78000 Versailles, France
| | - Thomas Blein
- Institute of Plant Sciences Paris-Saclay (IPS2), CNRS, INRAE, Universités Paris-Sud, Evry, Paris-Diderot, Sorbonne Paris-Cité, Paris-Saclay, Bâtiment 630, 91405 Orsay, France
| | - Vincent Jauvion
- Université Paris-Saclay, INRAE, AgroParisTech, Institut Jean-Pierre Bourgin (IJPB), 78000 Versailles, France
| | - Nathalie Bouteiller
- Université Paris-Saclay, INRAE, AgroParisTech, Institut Jean-Pierre Bourgin (IJPB), 78000 Versailles, France
| | - Jun Cao
- Department of Molecular Biology, Max Planck Institute for Developmental Biology, Spemannstrasse 35, 72076 Tübingen, Germany
| | - Martin D Crespi
- Institute of Plant Sciences Paris-Saclay (IPS2), CNRS, INRAE, Universités Paris-Sud, Evry, Paris-Diderot, Sorbonne Paris-Cité, Paris-Saclay, Bâtiment 630, 91405 Orsay, France
| | - Hervé Vaucheret
- Université Paris-Saclay, INRAE, AgroParisTech, Institut Jean-Pierre Bourgin (IJPB), 78000 Versailles, France
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5
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Hoffmann G, Mahboubi A, Bente H, Garcia D, Hanson J, Hafrén A. Arabidopsis RNA processing body components LSM1 and DCP5 aid in the evasion of translational repression during Cauliflower mosaic virus infection. THE PLANT CELL 2022; 34:3128-3147. [PMID: 35511183 PMCID: PMC9338796 DOI: 10.1093/plcell/koac132] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/15/2022] [Accepted: 04/24/2022] [Indexed: 06/14/2023]
Abstract
Viral infections impose extraordinary RNA stress, triggering cellular RNA surveillance pathways such as RNA decapping, nonsense-mediated decay, and RNA silencing. Viruses need to maneuver among these pathways to establish infection and succeed in producing high amounts of viral proteins. Processing bodies (PBs) are integral to RNA triage in eukaryotic cells, with several distinct RNA quality control pathways converging for selective RNA regulation. In this study, we investigated the role of Arabidopsis thaliana PBs during Cauliflower mosaic virus (CaMV) infection. We found that several PB components are co-opted into viral factories that support virus multiplication. This pro-viral role was not associated with RNA decay pathways but instead, we established that PB components are helpers in viral RNA translation. While CaMV is normally resilient to RNA silencing, dysfunctions in PB components expose the virus to this pathway, which is similar to previous observations for transgenes. Transgenes, however, undergo RNA quality control-dependent RNA degradation and transcriptional silencing, whereas CaMV RNA remains stable but becomes translationally repressed through decreased ribosome association, revealing a unique dependence among PBs, RNA silencing, and translational repression. Together, our study shows that PB components are co-opted by the virus to maintain efficient translation, a mechanism not associated with canonical PB functions.
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Affiliation(s)
- Gesa Hoffmann
- Department of Plant Biology, Uppsala BioCenter, Swedish University of Agricultural Sciences, Uppsala 75007, Sweden
- Linnean Center for Plant Biology, Uppsala 75007, Sweden
| | - Amir Mahboubi
- Department of Plant Physiology, Umeå Plant Science Centre, Umeå University, Umeå, Sweden
| | - Heinrich Bente
- Department of Plant Biology, Uppsala BioCenter, Swedish University of Agricultural Sciences, Uppsala 75007, Sweden
- Linnean Center for Plant Biology, Uppsala 75007, Sweden
| | - Damien Garcia
- Institut de Biologie Moléculaire des Plantes, CNRS, Université de Strasbourg, Strasbourg, France
| | - Johannes Hanson
- Department of Plant Physiology, Umeå Plant Science Centre, Umeå University, Umeå, Sweden
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6
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Zuo Z, Roux M, Rodriguez E, Petersen M. mRNA Decapping Factors LSM1 and PAT Paralogs Are Involved in Turnip Mosaic Virus Viral Infection. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2022; 35:125-130. [PMID: 35100808 DOI: 10.1094/mpmi-09-21-0220-sc] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Turnip mosaic virus is a devastating potyvirus infecting many economically important brassica crops. In response to this, the plant host engages its RNA silencing machinery, involving AGO proteins, as a prominent strategy to restrain turnip mosaic virus (TuMV) infection. It has also been shown that the mRNA decay components DCP2 and VCS partake in viral infection suppression. Here, we report that the mRNA decapping components LSM1, PAT1, PATH1, and PATH2 are essential for TuMV infection. More specifically, lsm1a/lsm1b double mutants and pat1/path1/path2 triple mutants in summ2 background exhibit resistance to TuMV. Concurrently, we observed that TuMV interferes with the decapping function of LSM1 and PAT proteins as the mRNA-decay target genes UGT87A2 and ASL9 accumulate during TuMV infection. Moreover, as TuMV coat protein can be specifically found in complexes with PAT proteins but not LSM1, this suggests that TuMV "hijacks" decapping components via PAT proteins to support viral infection.[Formula: see text] Copyright © 2022 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.
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Affiliation(s)
- Zhangli Zuo
- Department of Biology, Faculty of Science, University of Copenhagen, Copenhagen, Denmark
| | - Milena Roux
- Department of Biology, Faculty of Science, University of Copenhagen, Copenhagen, Denmark
| | - Eleazar Rodriguez
- Department of Biology, Faculty of Science, University of Copenhagen, Copenhagen, Denmark
| | - Morten Petersen
- Department of Biology, Faculty of Science, University of Copenhagen, Copenhagen, Denmark
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7
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Krzyszton M, Kufel J. Analysis of mRNA-derived siRNAs in mutants of mRNA maturation and surveillance pathways in Arabidopsis thaliana. Sci Rep 2022; 12:1474. [PMID: 35087200 PMCID: PMC8795450 DOI: 10.1038/s41598-022-05574-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2021] [Accepted: 01/14/2022] [Indexed: 02/05/2023] Open
Abstract
Defects in RNA maturation and RNA decay factors may generate substrates for the RNA interference machinery. This phenomenon was observed in plants where mutations in some RNA-related factors lead to the production of RNA-quality control small interfering RNAs and several mutants show enhanced silencing of reporter transgenes. To assess the potential of RNAi activation on endogenous transcripts, we sequenced small RNAs from a set of Arabidopsis thaliana mutants with defects in various RNA metabolism pathways. We observed a global production of siRNAs caused by inefficient pre-mRNA cleavage and polyadenylation leading to read-through transcription into downstream antisense genes. In addition, in the lsm1a lsm1b double mutant, we identified NIA1, SMXL5, and several miRNA-targeted mRNAs as producing siRNAs, a group of transcripts suggested being especially sensitive to deficiencies in RNA metabolism. However, in most cases, RNA metabolism perturbations do not lead to the widespread production of siRNA derived from mRNA molecules. This observation is contrary to multiple studies based on reporter transgenes and suggests that only a very high accumulation of defective mRNA species caused by specific mutations or substantial RNA processing defects trigger RNAi pathways.
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Affiliation(s)
- Michal Krzyszton
- Laboratory of Seeds Molecular Biology, Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Pawinskiego 5a, 02-106, Warsaw, Poland.
| | - Joanna Kufel
- Faculty of Biology, Institute of Genetics and Biotechnology, University of Warsaw, Pawinskiego 5a, 02-106, Warsaw, Poland.
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8
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Oberlin S, Rajeswaran R, Trasser M, Barragán-Borrero V, Schon MA, Plotnikova A, Loncsek L, Nodine MD, Marí-Ordóñez A, Voinnet O. Innate, translation-dependent silencing of an invasive transposon in Arabidopsis. EMBO Rep 2021; 23:e53400. [PMID: 34931432 PMCID: PMC8892269 DOI: 10.15252/embr.202153400] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2021] [Revised: 12/05/2021] [Accepted: 12/06/2021] [Indexed: 11/25/2022] Open
Abstract
Co‐evolution between hosts’ and parasites’ genomes shapes diverse pathways of acquired immunity based on silencing small (s)RNAs. In plants, sRNAs cause heterochromatinization, sequence degeneration, and, ultimately, loss of autonomy of most transposable elements (TEs). Recognition of newly invasive plant TEs, by contrast, involves an innate antiviral‐like silencing response. To investigate this response’s activation, we studied the single‐copy element EVADÉ (EVD), one of few representatives of the large Ty1/Copia family able to proliferate in Arabidopsis when epigenetically reactivated. In Ty1/Copia elements, a short subgenomic mRNA (shGAG) provides the necessary excess of structural GAG protein over the catalytic components encoded by the full‐length genomic flGAG‐POL. We show here that the predominant cytosolic distribution of shGAG strongly favors its translation over mostly nuclear flGAG‐POL. During this process, an unusually intense ribosomal stalling event coincides with mRNA breakage yielding unconventional 5’OH RNA fragments that evade RNA quality control. The starting point of sRNA production by RNA‐DEPENDENT‐RNA‐POLYMERASE‐6 (RDR6), exclusively on shGAG, occurs precisely at this breakage point. This hitherto‐unrecognized “translation‐dependent silencing” (TdS) is independent of codon usage or GC content and is not observed on TE remnants populating the Arabidopsis genome, consistent with their poor association, if any, with polysomes. We propose that TdS forms a primal defense against EVD de novo invasions that underlies its associated sRNA pattern.
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Affiliation(s)
- Stefan Oberlin
- Department of Biology, Swiss Federal Institute of Technology (ETH), Zurich, Switzerland
| | - Rajendran Rajeswaran
- Department of Biology, Swiss Federal Institute of Technology (ETH), Zurich, Switzerland
| | - Marieke Trasser
- Gregor Mendel Institute of Molecular Plant Biology (GMI) of the Austrian Academy of Sciences, Vienna, Austria.,Vienna BioCenter PhD Program, Doctoral School of the University of Vienna and Medical University of Vienna, Vienna, Austria
| | - Verónica Barragán-Borrero
- Department of Biology, Swiss Federal Institute of Technology (ETH), Zurich, Switzerland.,Gregor Mendel Institute of Molecular Plant Biology (GMI) of the Austrian Academy of Sciences, Vienna, Austria
| | - Michael A Schon
- Gregor Mendel Institute of Molecular Plant Biology (GMI) of the Austrian Academy of Sciences, Vienna, Austria
| | - Alexandra Plotnikova
- Gregor Mendel Institute of Molecular Plant Biology (GMI) of the Austrian Academy of Sciences, Vienna, Austria
| | - Lukas Loncsek
- Gregor Mendel Institute of Molecular Plant Biology (GMI) of the Austrian Academy of Sciences, Vienna, Austria
| | - Michael D Nodine
- Gregor Mendel Institute of Molecular Plant Biology (GMI) of the Austrian Academy of Sciences, Vienna, Austria.,Laboratory of Molecular Biology, Wageningen University, Wageningen, The Netherlands
| | - Arturo Marí-Ordóñez
- Department of Biology, Swiss Federal Institute of Technology (ETH), Zurich, Switzerland.,Gregor Mendel Institute of Molecular Plant Biology (GMI) of the Austrian Academy of Sciences, Vienna, Austria
| | - Olivier Voinnet
- Department of Biology, Swiss Federal Institute of Technology (ETH), Zurich, Switzerland
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9
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Butel N, Yu A, Le Masson I, Borges F, Elmayan T, Taochy C, Gursanscky NR, Cao J, Bi S, Sawyer A, Carroll BJ, Vaucheret H. Contrasting epigenetic control of transgenes and endogenous genes promotes post-transcriptional transgene silencing in Arabidopsis. Nat Commun 2021; 12:2787. [PMID: 33986281 PMCID: PMC8119426 DOI: 10.1038/s41467-021-22995-3] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2020] [Accepted: 04/06/2021] [Indexed: 11/20/2022] Open
Abstract
Transgenes that are stably expressed in plant genomes over many generations could be assumed to behave epigenetically the same as endogenous genes. Here, we report that whereas the histone H3K9me2 demethylase IBM1, but not the histone H3K4me3 demethylase JMJ14, counteracts DNA methylation of Arabidopsis endogenous genes, JMJ14, but not IBM1, counteracts DNA methylation of expressed transgenes. Additionally, JMJ14-mediated specific attenuation of transgene DNA methylation enhances the production of aberrant RNAs that readily induce systemic post-transcriptional transgene silencing (PTGS). Thus, the JMJ14 chromatin modifying complex maintains expressed transgenes in a probationary state of susceptibility to PTGS, suggesting that the host plant genome does not immediately accept expressed transgenes as being epigenetically the same as endogenous genes. Accumulating evidences point to a discrepancy in the epigenetic behaviour of transgenes and endogenous genes. Here, via characterization of mutants impaired in histone demethylases JMJ14 and IBM1, the authors show that transgenes and endogenous genes are regulated by different epigenetic mechanisms in Arabidopsis.
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Affiliation(s)
- Nicolas Butel
- Institut Jean-Pierre Bourgin, UMR 1318, INRAE, AgroParisTech, Université Paris-Saclay, Versailles, France.,Université Paris-Sud, Université Paris-Saclay, Orsay, France
| | - Agnès Yu
- Institut Jean-Pierre Bourgin, UMR 1318, INRAE, AgroParisTech, Université Paris-Saclay, Versailles, France
| | - Ivan Le Masson
- Institut Jean-Pierre Bourgin, UMR 1318, INRAE, AgroParisTech, Université Paris-Saclay, Versailles, France
| | - Filipe Borges
- Institut Jean-Pierre Bourgin, UMR 1318, INRAE, AgroParisTech, Université Paris-Saclay, Versailles, France
| | - Taline Elmayan
- Institut Jean-Pierre Bourgin, UMR 1318, INRAE, AgroParisTech, Université Paris-Saclay, Versailles, France
| | - Christelle Taochy
- Institut Jean-Pierre Bourgin, UMR 1318, INRAE, AgroParisTech, Université Paris-Saclay, Versailles, France.,School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, QLD, Australia
| | - Nial R Gursanscky
- School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, QLD, Australia
| | - Jiangling Cao
- School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, QLD, Australia
| | - Shengnan Bi
- School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, QLD, Australia
| | - Anne Sawyer
- School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, QLD, Australia.,Queensland Alliance for Agriculture and Food Innovation, The University of Queensland, Brisbane, QLD, Australia
| | - Bernard J Carroll
- School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, QLD, Australia.
| | - Hervé Vaucheret
- Institut Jean-Pierre Bourgin, UMR 1318, INRAE, AgroParisTech, Université Paris-Saclay, Versailles, France.
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10
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Zhang Y, Wu X, Yuan L. Distinct non-coding RNAs confer root-dependent sense transgene-induced post-transcriptional gene silencing and nitrogen-dependent post-transcriptional regulation to AtAMT1;1 transcripts in Arabidopsis roots. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2020; 102:823-837. [PMID: 31901180 DOI: 10.1111/tpj.14667] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/22/2019] [Revised: 12/19/2019] [Accepted: 12/23/2019] [Indexed: 06/10/2023]
Abstract
High-affinity ammonium uptake in roots mediate by AMT1-type ammonium transporters, which are tightly controlled at multiple regulatory levels for adapting various nitrogen availability. For Arabidopsis AtAMT1;1 gene, in addition to the transcriptional and post-translational controls, an organ-dependent and N-dependent post-transcriptional regulation was suggested as an additional regulatory step for fine tuning ammonium uptake, but the underlying mechanisms remain to be elucidated. Here, we showed that degradation of AtAMT1;1 transcript in roots of Pro35s:AtAMT1;1-transformed atamt1;1-1 Arabidopsis plants resulted from RDR6-dependent sense transgene-induced post-transcriptional gene silencing (S-PTGS). The siRNAs for S-PTGS may derive from the aberrant RNA, of which the production was co-determined by sequence feature and excessive expression of AtAMT1;1. Switching to the expression of AtAMT1;1 driven by ProAtUBQ10 or of AtAMT1;1 mutated at two siRNA-targeted hotspots reduced AtAMT1;1-specific siRNAs and overcame S-PTGS in roots. In roots of these lines, however, the steady-state transcript levels of AtAMT1;1 still significantly decreased under conditions of N-sufficiency compared with N-deficiency, confirming a N-dependent post-transcriptional regulatory manner. A crucial role of the 207-bp 3'-end sequence of AtAMT1;1 was further demonstrated by N-dependent accumulation of chimeric-AtAMT1;1 transcript in T-DNA insertion lines and of GFP-tagged chimeric-AtAMT1;1 transcript in transgenic lines. A novel non-coding RNA (ncRNA), which was highly abundant in N-sufficient roots, may target the above-identified 3'-end region for the degrading AtAMT1;1 transcript. This degradation could be prevented by a mutation on the AtAMT1;1 transcript at a potential cleavage site (+1458). These results suggested two distinct mechanisms of regulating AtAMT1;1 mRNA turnover by ncRNA for strictly control of ammonium uptake in roots.
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Affiliation(s)
- Yongjian Zhang
- Key Laboratory of Plant-Soil Interaction, MOE, College of Resources and Environmental Sciences, China Agricultural University, 100193, Beijing, China
| | - Xiangyu Wu
- Key Laboratory of Plant-Soil Interaction, MOE, College of Resources and Environmental Sciences, China Agricultural University, 100193, Beijing, China
| | - Lixing Yuan
- Key Laboratory of Plant-Soil Interaction, MOE, College of Resources and Environmental Sciences, China Agricultural University, 100193, Beijing, China
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11
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Xu M, Mazur MJ, Tao X, Kormelink R. Cellular RNA Hubs: Friends and Foes of Plant Viruses. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2020; 33:40-54. [PMID: 31415225 DOI: 10.1094/mpmi-06-19-0161-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
RNA granules are dynamic cellular foci that are widely spread in eukaryotic cells and play essential roles in cell growth and development, and immune and stress responses. Different types of granules can be distinguished, each with a specific function and playing a role in, for example, RNA transcription, modification, processing, decay, translation, and arrest. By means of communication and exchange of (shared) components, they form a large regulatory network in cells. Viruses have been reported to interact with one or more of these either cytoplasmic or nuclear granules, and act either proviral, to enable and support viral infection and facilitate viral movement, or antiviral, protecting or clearing hosts from viral infection. This review describes an overview and recent progress on cytoplasmic and nuclear RNA granules and their interplay with virus infection, first in animal systems and as a prelude to the status and current developments on plant viruses, which have been less well studied on this thus far.
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Affiliation(s)
- Min Xu
- Key Laboratory of Integrated Management of Crop Diseases and Pests, Ministry of Education, Department of Plant Pathology, Nanjing Agricultural University, Nanjing 210095, China
- Laboratory of Virology, Department of Plant Sciences, Wageningen University & Research, Droevendaalsesteeg 1, 6708PB Wageningen, The Netherlands
| | - Magdalena J Mazur
- Laboratory of Virology, Department of Plant Sciences, Wageningen University & Research, Droevendaalsesteeg 1, 6708PB Wageningen, The Netherlands
| | - Xiaorong Tao
- Key Laboratory of Integrated Management of Crop Diseases and Pests, Ministry of Education, Department of Plant Pathology, Nanjing Agricultural University, Nanjing 210095, China
| | - Richard Kormelink
- Laboratory of Virology, Department of Plant Sciences, Wageningen University & Research, Droevendaalsesteeg 1, 6708PB Wageningen, The Netherlands
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12
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de Felippes FF, Waterhouse PM. The Whys and Wherefores of Transitivity in Plants. FRONTIERS IN PLANT SCIENCE 2020; 11:579376. [PMID: 32983223 PMCID: PMC7488869 DOI: 10.3389/fpls.2020.579376] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/02/2020] [Accepted: 08/14/2020] [Indexed: 05/05/2023]
Abstract
Transitivity in plants is a mechanism that produces secondary small interfering RNAs (siRNAs) from a transcript targeted by primary small RNAs (sRNAs). It expands the silencing signal to additional sequences of the transcript. The process requires RNA-dependent RNA polymerases (RDRs), which convert single-stranded RNA targets into a double-stranded (ds) RNA, the precursor of siRNAs and is critical for effective and amplified responses to virus infection. It is also important for the production of endogenous secondary siRNAs, such as phased siRNAs (phasiRNAs), which regulate several genes involved in development and adaptation. Transitivity on endogenous transcripts is very specific, utilizing special primary sRNAs, such as miRNAs with unique features, and particular ARGONAUTEs. In contrast, transitivity on transgene and virus (exogenous) transcripts is more generic. This dichotomy of responses implies the existence of a mechanism that differentiates self from non-self targets. In this work, we examine the possible mechanistic process behind the dichotomy and the intriguing counter-intuitive directionality of transitive sequence-spread in plants.
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13
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Abstract
Plant virus genome replication and movement is dependent on host resources and factors. However, plants respond to virus infection through several mechanisms, such as autophagy, ubiquitination, mRNA decay and gene silencing, that target viral components. Viral factors work in synchrony with pro-viral host factors during the infection cycle and are targeted by antiviral responses. Accordingly, establishment of virus infection is genetically determined by the availability of the pro-viral factors necessary for genome replication and movement, and by the balance between plant defence and viral suppression of defence responses. Sequential requirement of pro-viral factors and the antagonistic activity of antiviral factors suggest a two-step model to explain plant-virus interactions. At each step of the infection process, host factors with antiviral activity have been identified. Here we review our current understanding of host factors with antiviral activity against plant viruses.
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Affiliation(s)
- Hernan Garcia‐Ruiz
- Nebraska Center for Virology, Department of Plant PathologyUniversity of Nebraska‐LincolnLincolnNE68503USA
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14
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Ma X, Zhou Y, Moffett P. Alterations in cellular RNA decapping dynamics affect tomato spotted wilt virus cap snatching and infection in Arabidopsis. THE NEW PHYTOLOGIST 2019; 224:789-803. [PMID: 31292958 DOI: 10.1111/nph.16049] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/01/2019] [Accepted: 06/27/2019] [Indexed: 06/09/2023]
Abstract
RNA processing and decay pathways have important impacts on RNA viruses, particularly animal-infecting bunyaviruses, which utilize a cap-snatching mechanism to translate their mRNAs. However, their effects on plant-infecting bunyaviruses have not been investigated. The roles of mRNA degradation and non-sense-mediated decay components, including DECAPPING 2 (DCP2), EXORIBONUCLEASE 4 (XRN4), ASYMMETRIC LEAVES2 (AS2) and UP-FRAMESHIFT 1 (UPF1) were investigated in infection of Arabidopsis thaliana by several RNA viruses, including the bunyavirus, tomato spotted wilt virus (TSWV). TSWV infection on mutants with decreased or increased RNA decapping ability resulted in increased and decreased susceptibility, respectively. By contrast, these mutations had the opposite, or no, effect on RNA viruses that use different mRNA capping strategies. Consistent with this, the RNA capping efficiency of TSWV mRNA was higher in a dcp2 mutant. Furthermore, the TSWV N protein partially colocalized with RNA processing body (PB) components and altering decapping activity by heat shock or coinfection with another virus resulted in corresponding changes in TSWV accumulation. The present results indicate that TSWV infection in plants depends on its ability to snatch caps from mRNAs destined for decapping in PBs and that genetic or environmental alteration of RNA processing dynamics can affect infection outcomes.
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Affiliation(s)
- Xiaofang Ma
- Institute of Plant Protection, Jiangsu Academy of Agricultural Sciences, Jiangsu Technical Service Center of Diagnosis and Detection for Plant Virus Diseases, no. 50 Zhongling Street, Nanjing, Jiangsu, 210014, China
- Centre SÈVE, Département de Biologie, Université de Sherbrooke, 2500 Blvd. de l' Université, Sherbrooke, QC, J1K 2R1, Canada
| | - Yijun Zhou
- Institute of Plant Protection, Jiangsu Academy of Agricultural Sciences, Jiangsu Technical Service Center of Diagnosis and Detection for Plant Virus Diseases, no. 50 Zhongling Street, Nanjing, Jiangsu, 210014, China
| | - Peter Moffett
- Centre SÈVE, Département de Biologie, Université de Sherbrooke, 2500 Blvd. de l' Université, Sherbrooke, QC, J1K 2R1, Canada
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15
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Taochy C, Yu A, Bouché N, Bouteiller N, Elmayan T, Dressel U, Carroll BJ, Vaucheret H. Post-transcriptional gene silencing triggers dispensable DNA methylation in gene body in Arabidopsis. Nucleic Acids Res 2019; 47:9104-9114. [PMID: 31372641 PMCID: PMC6753489 DOI: 10.1093/nar/gkz636] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2019] [Revised: 06/27/2019] [Accepted: 07/26/2019] [Indexed: 11/14/2022] Open
Abstract
Spontaneous post-transcriptional silencing of sense transgenes (S-PTGS) is established in each generation and is accompanied by DNA methylation, but the pathway of PTGS-dependent DNA methylation is unknown and so is its role. Here we show that CHH and CHG methylation coincides spatially and temporally with RDR6-dependent products derived from the central and 3' regions of the coding sequence, and requires the components of the RNA-directed DNA methylation (RdDM) pathway NRPE1, DRD1 and DRM2, but not CLSY1, NRPD1, RDR2 or DCL3, suggesting that RDR6-dependent products, namely long dsRNAs and/or siRNAs, trigger PTGS-dependent DNA methylation. Nevertheless, none of these RdDM components are required to establish S-PTGS or produce a systemic silencing signal. Moreover, preventing de novo DNA methylation in non-silenced transgenic tissues grafted onto homologous silenced tissues does not inhibit the triggering of PTGS. Overall, these data indicate that gene body DNA methylation is a consequence, not a cause, of PTGS, and rule out the hypothesis that a PTGS-associated DNA methylation signal is transmitted independent of a PTGS signal.
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Affiliation(s)
- Christelle Taochy
- Institut Jean-Pierre Bourgin, INRA, AgroParisTech, CNRS, Université Paris-Saclay, 78000, Versailles, France
- School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Qld 4072, Australia
| | - Agnès Yu
- Institut Jean-Pierre Bourgin, INRA, AgroParisTech, CNRS, Université Paris-Saclay, 78000, Versailles, France
| | - Nicolas Bouché
- Institut Jean-Pierre Bourgin, INRA, AgroParisTech, CNRS, Université Paris-Saclay, 78000, Versailles, France
| | - Nathalie Bouteiller
- Institut Jean-Pierre Bourgin, INRA, AgroParisTech, CNRS, Université Paris-Saclay, 78000, Versailles, France
| | - Taline Elmayan
- Institut Jean-Pierre Bourgin, INRA, AgroParisTech, CNRS, Université Paris-Saclay, 78000, Versailles, France
| | - Uwe Dressel
- School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Qld 4072, Australia
| | - Bernard J Carroll
- School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Qld 4072, Australia
| | - Hervé Vaucheret
- Institut Jean-Pierre Bourgin, INRA, AgroParisTech, CNRS, Université Paris-Saclay, 78000, Versailles, France
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16
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RNA-Targeted Antiviral Immunity: More Than Just RNA Silencing. Trends Microbiol 2019; 27:792-805. [PMID: 31213342 DOI: 10.1016/j.tim.2019.05.007] [Citation(s) in RCA: 88] [Impact Index Per Article: 17.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2019] [Revised: 05/08/2019] [Accepted: 05/15/2019] [Indexed: 11/21/2022]
Abstract
RNA silencing is a fundamental, evolutionarily conserved mechanism that regulates gene expression in eukaryotes. It also functions as a primary immune defense in microbes, such as viruses in plants. In addition to RNA silencing, RNA decay and RNA quality-control pathways are also two ancestral forms of intrinsic antiviral immunity, and the three RNA-targeted pathways may operate cooperatively for their antiviral function. Plant viruses encode viral suppressors of RNA silencing (VSRs) to suppress RNA silencing and facilitate virus infection. In response, plants may activate a counter-counter-defense mechanism to cope with VSR-mediated RNA silencing suppression. In this review, we summarize current knowledge of RNA silencing, RNA decay, and RNA quality control in antiviral defense, and highlight the mechanisms by which viruses compromise RNA-targeted immunity for their infection and survival in plants.
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17
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Kwasnik A, Wang VYF, Krzyszton M, Gozdek A, Zakrzewska-Placzek M, Stepniak K, Poznanski J, Tong L, Kufel J. Arabidopsis DXO1 links RNA turnover and chloroplast function independently of its enzymatic activity. Nucleic Acids Res 2019; 47:4751-4764. [PMID: 30949699 PMCID: PMC6511851 DOI: 10.1093/nar/gkz100] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2018] [Revised: 02/01/2019] [Accepted: 02/07/2019] [Indexed: 01/07/2023] Open
Abstract
The DXO family of proteins participates in eukaryotic mRNA 5'-end quality control, removal of non-canonical NAD+ cap and maturation of fungal rRNA precursors. In this work, we characterize the Arabidopsis thaliana DXO homolog, DXO1. We demonstrate that the plant-specific modification within the active site negatively affects 5'-end capping surveillance properties of DXO1, but has only a minor impact on its strong deNADding activity. Unexpectedly, catalytic activity does not contribute to striking morphological and molecular aberrations observed upon DXO1 knockout in plants, which include growth and pigmentation deficiency, global transcriptomic changes and accumulation of RNA quality control siRNAs. Conversely, these phenotypes depend on the plant-specific N-terminal extension of DXO1. Pale-green coloration of DXO1-deficient plants and our RNA-seq data reveal that DXO1 affects chloroplast-localized processes. We propose that DXO1 mediates the connection between RNA turnover and retrograde chloroplast-to-nucleus signaling independently of its deNADding properties.
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Affiliation(s)
- Aleksandra Kwasnik
- Institute of Genetics and Biotechnology, Faculty of Biology, University of Warsaw, Pawinskiego 5a, 02-106 Warsaw, Poland,Correspondence may also be addressed to Aleksandra Kwasnik. Tel: +48 22 5922245; Fax: +48 22 6584176;
| | - Vivien Ya-Fan Wang
- Department of Biological Sciences, Columbia University, New York, NY 10027, USA
| | - Michal Krzyszton
- Institute of Genetics and Biotechnology, Faculty of Biology, University of Warsaw, Pawinskiego 5a, 02-106 Warsaw, Poland
| | - Agnieszka Gozdek
- Institute of Genetics and Biotechnology, Faculty of Biology, University of Warsaw, Pawinskiego 5a, 02-106 Warsaw, Poland
| | - Monika Zakrzewska-Placzek
- Institute of Genetics and Biotechnology, Faculty of Biology, University of Warsaw, Pawinskiego 5a, 02-106 Warsaw, Poland
| | - Karolina Stepniak
- Institute of Genetics and Biotechnology, Faculty of Biology, University of Warsaw, Pawinskiego 5a, 02-106 Warsaw, Poland
| | - Jaroslaw Poznanski
- Institute of Biochemistry and Biophysics Polish Academy of Sciences, Pawinskiego 5a, 02-106 Warsaw, Poland
| | - Liang Tong
- Department of Biological Sciences, Columbia University, New York, NY 10027, USA,Correspondence may also be addressed to Liang Tong. Tel: +1 212 854 5203; Fax: +1 212 865 8246;
| | - Joanna Kufel
- Institute of Genetics and Biotechnology, Faculty of Biology, University of Warsaw, Pawinskiego 5a, 02-106 Warsaw, Poland,To whom correspondence should be addressed. Tel: +48 22 5922245; Fax: +48 22 6584176;
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18
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Abstract
Plant growth and productivity are greatly impacted by environmental stresses. Therefore, plants have evolved mechanisms which allow them to adapt to abiotic stresses through alterations in gene expression and metabolism. In recent years, studies have investigated the role of long noncoding RNA (lncRNA) in regulating gene expression in plants and characterized their involvement in various biological functions through their regulation of DNA methylation, DNA structural modifications, histone modifications, and RNA-RNA interactions. Genome-wide transcriptome analyses have identified various types of noncoding RNAs (ncRNAs) that respond to abiotic stress. These ncRNAs are in addition to the well-known housekeeping ncRNAs, such as rRNAs, tRNAs, snoRNAs, and snRNAs. In this review, recent research pertaining to the role of lncRNAs in the response of plants to abiotic stress is summarized and discussed.
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Affiliation(s)
- Akihiro Matsui
- Plant Genomic Network Research Team, RIKEN Center for Sustainable Resource Science, Yokohama, Kanagawa, Japan.
- Plant Epigenome Regulation Laboratory, RIKEN Cluster for Pioneering Research, Wako, Saitama, Japan.
| | - Motoaki Seki
- Plant Genomic Network Research Team, RIKEN Center for Sustainable Resource Science, Yokohama, Kanagawa, Japan.
- Plant Epigenome Regulation Laboratory, RIKEN Cluster for Pioneering Research, Wako, Saitama, Japan.
- Kihara Institute for Biological Research, Yokohama City University, Yokohama, Kanagawa, Japan.
- Core Research for Evolutional Science and Technology, Japan Science and Technology, Kawaguchi, Saitama, Japan.
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19
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Li F, Wang A. RNA decay is an antiviral defense in plants that is counteracted by viral RNA silencing suppressors. PLoS Pathog 2018; 14:e1007228. [PMID: 30075014 PMCID: PMC6101400 DOI: 10.1371/journal.ppat.1007228] [Citation(s) in RCA: 49] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2018] [Revised: 08/20/2018] [Accepted: 07/17/2018] [Indexed: 11/19/2022] Open
Abstract
Exonuclease-mediated RNA decay in plants is known to be involved primarily in endogenous RNA degradation, and several RNA decay components have been suggested to attenuate RNA silencing possibly through competing for RNA substrates. In this paper, we report that overexpression of key cytoplasmic 5'-3' RNA decay pathway gene-encoded proteins (5'RDGs) such as decapping protein 2 (DCP2) and exoribonuclease 4 (XRN4) in Nicotiana benthamiana fails to suppress sense transgene-induced post-transcriptional gene silencing (S-PTGS). On the contrary, knock-down of these 5'RDGs attenuates S-PTGS and supresses the generation of small interfering RNAs (siRNAs). We show that 5'RDGs degrade transgene transcripts via the RNA decay pathway when the S-PTGS pathway is disabled. Thus, RNA silencing and RNA decay degrade exogenous gene transcripts in a hierarchical and coordinated manner. Moreover, we present evidence that infection by turnip mosaic virus (TuMV) activates RNA decay and 5'RDGs also negatively regulate TuMV RNA accumulation. We reveal that RNA silencing and RNA decay can mediate degradation of TuMV RNA in the same way that they target transgene transcripts. Furthermore, we demonstrate that VPg and HC-Pro, the two known viral suppressors of RNA silencing (VSRs) of potyviruses, bind to DCP2 and XRN4, respectively, and the interactions compromise their antiviral function. Taken together, our data highlight the overlapping function of the RNA silencing and RNA decay pathways in plants, as evidenced by their hierarchical and concerted actions against exogenous and viral RNA, and VSRs not only counteract RNA silencing but also subvert RNA decay to promote viral infection.
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Affiliation(s)
- Fangfang Li
- London Research and Development Centre, Agriculture and Agri-Food Canada, London, Ontario, Canada
| | - Aiming Wang
- London Research and Development Centre, Agriculture and Agri-Food Canada, London, Ontario, Canada
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20
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Abstract
RNA interference (RNAi) is a mechanism conserved in eukaryotes, including fungi, that represses gene expression by means of small noncoding RNAs (sRNAs) of about 20 to 30 nucleotides. Its discovery is one of the most important scientific breakthroughs of the past 20 years, and it has revolutionized our perception of the functioning of the cell. Initially described and characterized in Neurospora crassa, the RNAi is widespread in fungi, suggesting that it plays important functions in the fungal kingdom. Several RNAi-related mechanisms for maintenance of genome integrity, particularly protection against exogenous nucleic acids such as mobile elements, have been described in several fungi, suggesting that this is the main function of RNAi in the fungal kingdom. However, an increasing number of fungal sRNAs with regulatory functions generated by specific RNAi pathways have been identified. Several mechanistic aspects of the biogenesis of these sRNAs are known, but their function in fungal development and physiology is scarce, except for remarkable examples such as Mucor circinelloides, in which specific sRNAs clearly regulate responses to environmental and endogenous signals. Despite the retention of RNAi in most species, some fungal groups and species lack an active RNAi mechanism, suggesting that its loss may provide some selective advantage. This article summarizes the current understanding of RNAi functions in the fungal kingdom.
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21
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Torres-Martínez S, Ruiz-Vázquez RM. The RNAi Universe in Fungi: A Varied Landscape of Small RNAs and Biological Functions. Annu Rev Microbiol 2017; 71:371-391. [PMID: 28657888 DOI: 10.1146/annurev-micro-090816-093352] [Citation(s) in RCA: 57] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
RNA interference (RNAi) is a conserved eukaryotic mechanism that uses small RNA molecules to suppress gene expression through sequence-specific messenger RNA degradation, translational repression, or transcriptional inhibition. In filamentous fungi, the protective function of RNAi in the maintenance of genome integrity is well known. However, knowledge of the regulatory role of RNAi in fungi has had to wait until the recent identification of different endogenous small RNA classes, which are generated by distinct RNAi pathways. In addition, RNAi research on new fungal models has uncovered the role of small RNAs and RNAi pathways in the regulation of diverse biological functions. In this review, we give an up-to-date overview of the different classes of small RNAs and RNAi pathways in fungi and their roles in the defense of genome integrity and regulation of fungal physiology and development, as well as in the interaction of fungi with biotic and abiotic environments.
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22
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Calo S, Nicolás FE, Lee SC, Vila A, Cervantes M, Torres-Martinez S, Ruiz-Vazquez RM, Cardenas ME, Heitman J. A non-canonical RNA degradation pathway suppresses RNAi-dependent epimutations in the human fungal pathogen Mucor circinelloides. PLoS Genet 2017; 13:e1006686. [PMID: 28339467 PMCID: PMC5384783 DOI: 10.1371/journal.pgen.1006686] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2016] [Revised: 04/07/2017] [Accepted: 03/13/2017] [Indexed: 11/21/2022] Open
Abstract
Mucorales are a group of basal fungi that includes the casual agents of the human emerging disease mucormycosis. Recent studies revealed that these pathogens activate an RNAi-based pathway to rapidly generate drug-resistant epimutant strains when exposed to stressful compounds such as the antifungal drug FK506. To elucidate the molecular mechanism of this epimutation pathway, we performed a genetic analysis in Mucor circinelloides that revealed an inhibitory role for the non-canonical RdRP-dependent Dicer-independent silencing pathway, which is an RNAi-based mechanism involved in mRNA degradation that was recently identified. Thus, mutations that specifically block the mRNA degradation pathway, such as those in the genes r3b2 and rdrp3, enhance the production of drug resistant epimutants, similar to the phenotype previously described for mutation of the gene rdrp1. Our genetic analysis also revealed two new specific components of the epimutation pathway related to the quelling induced protein (qip) and a Sad-3-like helicase (rnhA), as mutations in these genes prevented formation of drug-resistant epimutants. Remarkably, drug-resistant epimutant production was notably increased in M. circinelloides f. circinelloides isolates from humans or other animal hosts. The host-pathogen interaction could be a stressful environment in which the phenotypic plasticity provided by the epimutant pathway might provide an advantage for these strains. These results evoke a model whereby balanced regulation of two different RNAi pathways is determined by the activation of the RNAi-dependent epimutant pathway under stress conditions, or its repression when the regular maintenance of the mRNA degradation pathway operates under non-stress conditions. Mucormycosis is a fungal infection that is attracting the attention of both clinical and research communities because of the lack of effective antifungal treatments and its often fatal prognosis. Our previous studies revealed an RNAi-mediated epimutation mechanism that operates in the casual human fungal pathogens (Mucorales species) and which might underlie the lack of efficacy of some antifungal treatments. This epimutation mechanism represses the expression of antifungal drug target genes and thereby generates antifungal drug resistant strains. Here, we studied the regulation and identified new components of the epimutation pathway. We found that a newly identified mRNA degradation pathway, named the non-canonical RdRP-dependent Dicer-independent silencing pathway, exerts an inhibitory effect on the RNAi-mediated epimutation mechanism and operates during growth under non-stressful conditions. Interestingly, the RNAi-based epimutation mechanism is more active in M. circinelloides f. circinelloides isolates from human and other animal sources, suggesting that this mechanism may influence host-pathogen interactions. These results further our understanding of the mechanisms deployed by fungal pathogens to survive and adapt under stressful environmental conditions that may include the host niche.
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Affiliation(s)
- Silvia Calo
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, North Carolina, United States of America
| | - Francisco E. Nicolás
- Department of Genetics and Microbiology, Faculty of Biology, University of Murcia, Murcia, Spain
| | - Soo Chan Lee
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, North Carolina, United States of America
| | - Ana Vila
- Department of Genetics and Microbiology, Faculty of Biology, University of Murcia, Murcia, Spain
| | - Maria Cervantes
- Department of Genetics and Microbiology, Faculty of Biology, University of Murcia, Murcia, Spain
| | - Santiago Torres-Martinez
- Department of Genetics and Microbiology, Faculty of Biology, University of Murcia, Murcia, Spain
| | - Rosa M. Ruiz-Vazquez
- Department of Genetics and Microbiology, Faculty of Biology, University of Murcia, Murcia, Spain
| | - Maria E. Cardenas
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, North Carolina, United States of America
| | - Joseph Heitman
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, North Carolina, United States of America
- * E-mail:
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23
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Tsuzuki M, Motomura K, Kumakura N, Takeda A. Interconnections between mRNA degradation and RDR-dependent siRNA production in mRNA turnover in plants. JOURNAL OF PLANT RESEARCH 2017; 130:211-226. [PMID: 28197782 DOI: 10.1007/s10265-017-0906-8] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/24/2016] [Accepted: 12/08/2016] [Indexed: 06/06/2023]
Abstract
Accumulation of an mRNA species is determined by the balance between the synthesis and the degradation of the mRNA. Individual mRNA molecules are selectively and actively degraded through RNA degradation pathways, which include 5'-3' mRNA degradation pathway, 3'-5' mRNA degradation pathway, and RNA-dependent RNA polymerase-mediated mRNA degradation pathway. Recent studies have revealed that these RNA degradation pathways compete with each other in mRNA turnover in plants and that plants have a hidden layer of non-coding small-interfering RNA production from a set of mRNAs. In this review, we summarize the current information about plant mRNA degradation pathways in mRNA turnover and discuss the potential roles of a novel class of the endogenous siRNAs derived from plant mRNAs.
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Affiliation(s)
- Masayuki Tsuzuki
- Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, Tokyo, 153-8902, Japan
- Department of Molecular, Cellular and Developmental Biology, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Kazuki Motomura
- Institute of Transformative Bio-Molecules, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi, 464-8601, Japan
| | - Naoyoshi Kumakura
- Center for Sustainable Resource Science, RIKEN, Suehiro-cho 1-7-22, Tsurumi-ku, Yokohama, Kanagawa, 230-0045, Japan
| | - Atsushi Takeda
- Department of Biotechnology, Graduate School of Life Sciences, Ritsumeikan University, Shiga, 525-8577, Japan.
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24
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Li F, Zhao N, Li Z, Xu X, Wang Y, Yang X, Liu SS, Wang A, Zhou X. A calmodulin-like protein suppresses RNA silencing and promotes geminivirus infection by degrading SGS3 via the autophagy pathway in Nicotiana benthamiana. PLoS Pathog 2017; 13:e1006213. [PMID: 28212430 PMCID: PMC5333915 DOI: 10.1371/journal.ppat.1006213] [Citation(s) in RCA: 104] [Impact Index Per Article: 14.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2016] [Revised: 03/02/2017] [Accepted: 02/02/2017] [Indexed: 12/31/2022] Open
Abstract
A recently characterized calmodulin-like protein is an endogenous RNA silencing suppressor that suppresses sense-RNA induced post-transcriptional gene silencing (S-PTGS) and enhances virus infection, but the mechanism underlying calmodulin-like protein-mediated S-PTGS suppression is obscure. Here, we show that a calmodulin-like protein from Nicotiana benthamiana (NbCaM) interacts with Suppressor of Gene Silencing 3 (NbSGS3). Deletion analyses showed that domains essential for the interaction between NbSGS3 and NbCaM are also required for the subcellular localization of NbSGS3 and NbCaM suppressor activity. Overexpression of NbCaM reduced the number of NbSGS3-associated granules by degrading NbSGS3 protein accumulation in the cytoplasm. This NbCaM-mediated NbSGS3 degradation was sensitive to the autophagy inhibitors 3-methyladenine and E64d, and was compromised when key autophagy genes of the phosphatidylinositol 3-kinase (PI3K) complex were knocked down. Meanwhile, silencing of key autophagy genes within the PI3K complex inhibited geminivirus infection. Taken together these data suggest that NbCaM acts as a suppressor of RNA silencing by degrading NbSGS3 through the autophagy pathway.
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Affiliation(s)
- Fangfang Li
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, China
- State Key Laboratory of Rice Biology, Institute of Biotechnology, Zhejiang University, Hangzhou, Zhejiang, China
| | - Nan Zhao
- State Key Laboratory of Rice Biology, Institute of Biotechnology, Zhejiang University, Hangzhou, Zhejiang, China
| | - Zhenghe Li
- State Key Laboratory of Rice Biology, Institute of Biotechnology, Zhejiang University, Hangzhou, Zhejiang, China
| | - Xiongbiao Xu
- State Key Laboratory of Rice Biology, Institute of Biotechnology, Zhejiang University, Hangzhou, Zhejiang, China
| | - Yaqin Wang
- State Key Laboratory of Rice Biology, Institute of Biotechnology, Zhejiang University, Hangzhou, Zhejiang, China
| | - Xiuling Yang
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, China
| | - Shu-Sheng Liu
- Ministry of Agriculture Key Laboratory of Agricultural Entomology, Institute of Insect Sciences, Zhejiang University, Hangzhou, Zhejiang, China
| | - Aiming Wang
- Southern Crop Protection and Food Research Centre, Agriculture and Agri-Food Canada, London, Ontario, Canada
| | - Xueping Zhou
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, China
- State Key Laboratory of Rice Biology, Institute of Biotechnology, Zhejiang University, Hangzhou, Zhejiang, China
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25
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Kraner ME, Link K, Melzer M, Ekici AB, Uebe S, Tarazona P, Feussner I, Hofmann J, Sonnewald U. Choline transporter-like1 (CHER1) is crucial for plasmodesmata maturation in Arabidopsis thaliana. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2017; 89:394-406. [PMID: 27743414 DOI: 10.1111/tpj.13393] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/02/2016] [Revised: 09/30/2016] [Accepted: 10/03/2016] [Indexed: 05/05/2023]
Abstract
Plasmodesmata (PD) are microscopic pores connecting plant cells and enable cell-to-cell transport. Currently, little information is known about the molecular mechanisms regulating PD formation and development. To uncover components of PD development we made use of the 17 kDa movement protein (MP17) encoded by the Potato leafroll virus (PLRV). The protein is required for cell-to-cell movement of the virus and localises to complex PD. Forward genetic screening for Arabidopsis mutants with altered PD binding of MP17 revealed several mutant lines, while molecular genetics, biochemical and microscopic studies allowed further characterisation. Map-based cloning of one mutant revealed a point mutation in the choline transporter-like 1 (CHER1) protein, changing glycine247 into glutamate. Mutation in CHER1 resulted in a starch excess phenotype and stunted growth. Ultrastructure analysis of shoot apical meristems, developing and fully developed leaves showed reduced PD numbers and the absence of complex PD in fully developed leaves. This indicates that cher1 mutants are impaired in PD formation and development. Global lipid profiling revealed only slight modifications in the overall lipid composition, however, altered composition of PD-associated lipids cannot be ruled out. Thus, cher1 is devoid of complex PD in developed leaves and provides insights into the formation of complex PD at the molecular level.
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Affiliation(s)
- Max E Kraner
- Division of Biochemistry, Department of Biology, Friedrich-Alexander University Erlangen-Nuremberg, Staudtstraße 5, D-91058, Erlangen, Germany
| | - Katrin Link
- Division of Biochemistry, Department of Biology, Friedrich-Alexander University Erlangen-Nuremberg, Staudtstraße 5, D-91058, Erlangen, Germany
| | - Michael Melzer
- Department of Physiology and Cell Biology, Leibniz Institute of Plant Genetics and Crop Plant Research, Corrensstrasse 3, D-06466, Seeland, Gatersleben, OT, Germany
| | - Arif B Ekici
- Institute of Human Genetics, University Hospital Erlangen, Friedrich-Alexander University Erlangen-Nuremberg, D-91054, Erlangen, Germany
| | - Steffen Uebe
- Institute of Human Genetics, University Hospital Erlangen, Friedrich-Alexander University Erlangen-Nuremberg, D-91054, Erlangen, Germany
| | - Pablo Tarazona
- Department of Plant Biochemistry, Georg-August-University Goettingen, Albrecht-von-Haller-Institute for Plant Sciences, Justus-von-Liebig-Weg 11, D-37077, Goettingen, Germany
| | - Ivo Feussner
- Department of Plant Biochemistry, Georg-August-University Goettingen, Albrecht-von-Haller-Institute for Plant Sciences, Justus-von-Liebig-Weg 11, D-37077, Goettingen, Germany
- Department of Plant Biochemistry, Georg-August-University Goettingen, Goettingen Center for Molecular Biosciences (GZMB), Justus-von-Liebig-Weg 11, D-37077, Goettingen, Germany
| | - Jörg Hofmann
- Division of Biochemistry, Department of Biology, Friedrich-Alexander University Erlangen-Nuremberg, Staudtstraße 5, D-91058, Erlangen, Germany
| | - Uwe Sonnewald
- Division of Biochemistry, Department of Biology, Friedrich-Alexander University Erlangen-Nuremberg, Staudtstraße 5, D-91058, Erlangen, Germany
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Conti G, Zavallo D, Venturuzzi AL, Rodriguez MC, Crespi M, Asurmendi S. TMV induces RNA decay pathways to modulate gene silencing and disease symptoms. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2017; 89:73-84. [PMID: 27599263 DOI: 10.1111/tpj.13323] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/05/2016] [Revised: 08/23/2016] [Accepted: 08/31/2016] [Indexed: 06/06/2023]
Abstract
RNA decay pathways comprise a combination of RNA degradation mechanisms that are implicated in gene expression, development and defense responses in eukaryotes. These mechanisms are known as the RNA Quality Control or RQC pathways. In plants, another important RNA degradation mechanism is the post-transcriptional gene silencing (PTGS) mediated by small RNAs (siRNAs). Notably, the RQC pathway antagonizes PTGS by preventing the entry of dysfunctional mRNAs into the silencing pathway to avoid global degradation of mRNA by siRNAs. Viral transcripts must evade RNA degrading mechanisms, thus viruses encode PTGS suppressor proteins to counteract viral RNA silencing. Here, we demonstrate that tobacco plants infected with TMV and transgenic lines expressing TMV MP and CP (coat protein) proteins (which are not linked to the suppression of silencing) display increased transcriptional levels of RNA decay genes. These plants also showed accumulation of cytoplasmic RNA granules with altered structure, increased rates of RNA decay for transgenes and defective transgene PTGS amplification. Furthermore, knockdown of RRP41 or RRP43 RNA exosome components led to lower levels of TMV accumulation with milder symptoms after infection, several developmental defects and miRNA deregulation. Thus, we propose that TMV proteins induce RNA decay pathways (in particular exosome components) to impair antiviral PTGS and this defensive mechanism would constitute an additional counter-defense strategy that lead to disease symptoms.
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Affiliation(s)
- Gabriela Conti
- Instituto de Biotecnología, CICVyA, INTA, Hurlingham, Argentina
- CONICET, Hurlingham, Argentina
| | - Diego Zavallo
- Instituto de Biotecnología, CICVyA, INTA, Hurlingham, Argentina
| | - Andrea L Venturuzzi
- Instituto de Biotecnología, CICVyA, INTA, Hurlingham, Argentina
- CONICET, Hurlingham, Argentina
| | | | - Martin Crespi
- Institute of Plant Sciences Paris-Saclay, IPS2, CNRS, INRA, University Paris-Sud, Orsay, France
| | - Sebastian Asurmendi
- Instituto de Biotecnología, CICVyA, INTA, Hurlingham, Argentina
- CONICET, Hurlingham, Argentina
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Mäkinen K, Lõhmus A, Pollari M. Plant RNA Regulatory Network and RNA Granules in Virus Infection. FRONTIERS IN PLANT SCIENCE 2017; 8:2093. [PMID: 29312371 PMCID: PMC5732267 DOI: 10.3389/fpls.2017.02093] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/13/2017] [Accepted: 11/24/2017] [Indexed: 05/18/2023]
Abstract
Regulation of post-transcriptional gene expression on mRNA level in eukaryotic cells includes translocation, translation, translational repression, storage, mRNA decay, RNA silencing, and nonsense-mediated decay. These processes are associated with various RNA-binding proteins and cytoplasmic ribonucleoprotein complexes many of which are conserved across eukaryotes. Microscopically visible aggregations formed by ribonucleoprotein complexes are termed RNA granules. Stress granules where the translationally inactive mRNAs are stored and processing bodies where mRNA decay may occur present the most studied RNA granule types. Diverse RNP-granules are increasingly being assigned important roles in viral infections. Although the majority of the molecular level studies on the role of RNA granules in viral translation and replication have been conducted in mammalian systems, some studies link also plant virus infection to RNA granules. An increasing body of evidence indicates that plant viruses require components of stress granules and processing bodies for their replication and translation, but how extensively the cellular mRNA regulatory network is utilized by plant viruses has remained largely enigmatic. Antiviral RNA silencing, which is an important regulator of viral RNA stability and expression in plants, is commonly counteracted by viral suppressors of RNA silencing. Some of the RNA silencing suppressors localize to cellular RNA granules and have been proposed to carry out their suppression functions there. Moreover, plant nucleotide-binding leucine-rich repeat protein-mediated virus resistance has been linked to enhanced processing body formation and translational repression of viral RNA. Many interesting questions relate to how the pathways of antiviral RNA silencing leading to viral RNA degradation and/or repression of translation, suppression of RNA silencing and viral RNA translation converge in plants and how different RNA granules and their individual components contribute to these processes. In this review we discuss the roles of cellular RNA regulatory mechanisms and RNA granules in plant virus infection in the light of current knowledge and compare the findings to those made in animal virus studies.
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Liu L, Chen X. RNA Quality Control as a Key to Suppressing RNA Silencing of Endogenous Genes in Plants. MOLECULAR PLANT 2016; 9:826-36. [PMID: 27045817 PMCID: PMC5123867 DOI: 10.1016/j.molp.2016.03.011] [Citation(s) in RCA: 66] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/17/2016] [Revised: 03/10/2016] [Accepted: 03/14/2016] [Indexed: 05/19/2023]
Abstract
RNA quality control of endogenous RNAs is an integral part of eukaryotic gene expression and often relies on exonucleolytic degradation to eliminate dysfunctional transcripts. In parallel, exogenous and selected endogenous RNAs are degraded through RNA silencing, which is a genome defense mechanism used by many eukaryotes. In plants, RNA silencing is triggered by the production of double-stranded RNAs (dsRNAs) by RNA-DEPENDENT RNA POLYMERASEs (RDRs) and proceeds through small interfering (si) RNA-directed, ARGONAUTE (AGO)-mediated cleavage of homologous transcripts. Many studies revealed that plants avert inappropriate posttranscriptional gene silencing of endogenous coding genes by using RNA surveillance mechanisms as a safeguard to protect their transcriptome profiles. The tug of war between RNA surveillance and RNA silencing ensures the appropriate partitioning of endogenous RNA substrates among these degradation pathways. Here we review recent advances on RNA quality control and its role in the suppression of RNA silencing at endogenous genes and discuss the mechanisms underlying the crosstalk among these pathways.
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Affiliation(s)
- Lin Liu
- Guangdong Provincial Key Laboratory for Plant Epigenetics, College of Life Sciences and Oceanography, Shenzhen University, Shenzhen 518060, P.R. China; Department of Botany and Plant Sciences, Institute of Integrative Genome Biology, University of California, Riverside, CA 92521, USA
| | - Xuemei Chen
- Guangdong Provincial Key Laboratory for Plant Epigenetics, College of Life Sciences and Oceanography, Shenzhen University, Shenzhen 518060, P.R. China; Department of Botany and Plant Sciences, Institute of Integrative Genome Biology, University of California, Riverside, CA 92521, USA; Howard Hughes Medical Institute, University of California, Riverside, CA 92521, USA.
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Post-transcriptional gene silencing in plants: a double-edged sword. SCIENCE CHINA-LIFE SCIENCES 2015; 59:271-6. [PMID: 26718356 DOI: 10.1007/s11427-015-4972-7] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/18/2015] [Accepted: 09/08/2015] [Indexed: 01/08/2023]
Abstract
In plants, post-transcriptional gene silencing (PTGS) protects the genome from foreign genes and restricts the expression of certain endogenous genes for proper development. Here, we review the recent progress about how the unwanted PTGS is avoided in plants. As a decision-making step of PTGS, aberrant transcripts from most endogenous coding genes are strictly sorted to the bidirectional RNA decay pathways in cytoplasm but not to the short interference RNA (siRNA)-mediated PTGS, with the exception of a few development-relevant endogenous siRNA-producing genes. We also discuss a finely balanced PTGS threshold model that plants fully take advantage of the power of PTGS without self-harm.
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Hafrén A, Lõhmus A, Mäkinen K. Formation of Potato Virus A-Induced RNA Granules and Viral Translation Are Interrelated Processes Required for Optimal Virus Accumulation. PLoS Pathog 2015; 11:e1005314. [PMID: 26641460 PMCID: PMC4671561 DOI: 10.1371/journal.ppat.1005314] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2015] [Accepted: 11/09/2015] [Indexed: 11/24/2022] Open
Abstract
RNA granules are cellular structures, which play an important role in mRNA translation, storage, and degradation. Animal (+)RNA viruses often co-opt RNA granule proteins for viral reproduction. However, the role of RNA granules in plant viral infections is poorly understood. Here we use Potato virus A (PVA) as a model potyvirus and demonstrate that the helper component-proteinase (HCpro), the potyviral suppressor of RNA silencing, induces the formation of RNA granules. We used confocal microscopy to demonstrate the presence of host RNA binding proteins including acidic ribosomal protein P0, argonaute 1 (AGO1), oligouridylate-binding protein 1 (UBP1), varicose (VCS) and eukaryotic initiation factor iso4E (eIF(iso)4E) in these potyvirus-induced RNA granules. We show that the number of potyviral RNA granules is down-regulated by the genome-linked viral protein (VPg). We demonstrated previously that VPg is a virus-specific translational regulator that co-operates with potyviral RNA granule components P0 and eIF(iso)4E in PVA translation. In this study we show that HCpro and varicose, components of potyviral RNA granules, stimulate VPg-promoted translation of the PVA, whereas UBP1 inhibits this process. Hence, we propose that PVA translation operates via a pathway that is interrelated with potyviral RNA granules in PVA infection. The importance of these granules is evident from the strong reduction in viral RNA and coat protein amounts that follows knock down of potyviral RNA granule components. HCpro suppresses antiviral RNA silencing during infection, and our results allow us to propose that this is also the functional context of the potyviral RNA granules we describe in this study.
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Affiliation(s)
- Anders Hafrén
- Department of Food and Environmental Sciences, Viikki Plant Science Centre, University of Helsinki, Helsinki, Finland
| | - Andres Lõhmus
- Department of Food and Environmental Sciences, Viikki Plant Science Centre, University of Helsinki, Helsinki, Finland
| | - Kristiina Mäkinen
- Department of Food and Environmental Sciences, Viikki Plant Science Centre, University of Helsinki, Helsinki, Finland
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Abstract
Plant genomes encode various small RNAs that function in distinct, yet overlapping, genetic and epigenetic silencing pathways. However, the abundance and diversity of small-RNA classes varies among plant species, suggesting coevolution between environmental adaptations and gene-silencing mechanisms. Biogenesis of small RNAs in plants is well understood, but we are just beginning to uncover their intricate regulation and activity. Here, we discuss the biogenesis of plant small RNAs, such as microRNAs, secondary siRNAs and heterochromatic siRNAs, and their diverse cellular and developmental functions, including in reproductive transitions, genomic imprinting and paramutation. We also discuss the diversification of small-RNA-directed silencing pathways through the expansion of RNA-dependent RNA polymerases, DICER proteins and ARGONAUTE proteins.
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Geminivirus Activates ASYMMETRIC LEAVES 2 to Accelerate Cytoplasmic DCP2-Mediated mRNA Turnover and Weakens RNA Silencing in Arabidopsis. PLoS Pathog 2015; 11:e1005196. [PMID: 26431425 PMCID: PMC4592220 DOI: 10.1371/journal.ppat.1005196] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2014] [Accepted: 09/08/2015] [Indexed: 11/25/2022] Open
Abstract
Aberrant viral RNAs produced in infected plant cells serve as templates for the synthesis of dsRNAs. The derived virus-related small interfering RNAs (siRNA) mediate cleavage of viral RNAs by post-transcriptional gene silencing (PTGS), thus blocking virus multiplication. Here, we identified ASYMMETRIC LEAVES2 (AS2) as a new component of plant P body complex which mediates mRNA decapping and degradation. We found that AS2 promotes DCP2 decapping activity, accelerates mRNA turnover rate, inhibits siRNA accumulation and functions as an endogenous suppressor of PTGS. Consistent with these findings, as2 mutant plants are resistant to virus infection whereas AS2 over-expression plants are hypersensitive. The geminivirus nuclear shuttle protein BV1 protein, which shuttles between nuclei and cytoplasm, induces AS2 expression, causes nuclear exit of AS2 to activate DCP2 decapping activity and renders infected plants more sensitive to viruses. These principles of gene induction and shuttling of induced proteins to promote mRNA decapping in the cytosol may be used by viral pathogens to weaken antiviral defenses in host plants. In higher plants, aberrant RNAs generated during virus replication serve as templates to make small interfering RNAs. These small RNAs are used by host as a defense mechanism to cleave viral RNAs thereby blocking virus replication. The anti-virus defense is attenuated by the host cellular mRNA turnover machinery which clears aberrant RNAs. Viruses may use encoded component(s) to activate host cellular mRNA turnover for their own benefits. In this study, we identified ASYMMETRIC LEAVES2 (AS2) as an activator of mRNA decapping and degradation and an endogenous suppressor of virus silencing. We showed that the geminivirus BV1 protein induces AS2 expression, causes nuclear exit of AS2 to activate mRNA decapping activity and renders infected plants more sensitive to viruses. Similar mechanisms may be used by other viral pathogens to weaken antiviral defenses in host plants and also mammals.
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Zhang H, Zhu J. Protecting genes from RNA silencing by destroying aberrant transcripts. SCIENCE CHINA. LIFE SCIENCES 2015; 58:613-615. [PMID: 25994414 DOI: 10.1007/s11427-015-4871-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/06/2015] [Accepted: 05/08/2015] [Indexed: 06/04/2023]
Affiliation(s)
- Heng Zhang
- Shanghai Center for Plant Stress Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, 201602, China,
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Trieu TA, Calo S, Nicolás FE, Vila A, Moxon S, Dalmay T, Torres-Martínez S, Garre V, Ruiz-Vázquez RM. A non-canonical RNA silencing pathway promotes mRNA degradation in basal Fungi. PLoS Genet 2015; 11:e1005168. [PMID: 25875805 PMCID: PMC4395119 DOI: 10.1371/journal.pgen.1005168] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2015] [Accepted: 03/20/2015] [Indexed: 12/04/2022] Open
Abstract
The increasing knowledge on the functional relevance of endogenous small RNAs (esRNAs) as riboregulators has stimulated the identification and characterization of these molecules in numerous eukaryotes. In the basal fungus Mucor circinelloides, an emerging opportunistic human pathogen, esRNAs that regulate the expression of many protein coding genes have been described. These esRNAs share common machinery for their biogenesis consisting of an RNase III endonuclease Dicer, a single Argonaute protein and two RNA-dependent RNA polymerases. We show in this study that, besides participating in this canonical dicer-dependent RNA interference (RNAi) pathway, the rdrp genes are involved in a novel dicer-independent degradation process of endogenous mRNAs. The analysis of esRNAs accumulated in wild type and silencing mutants demonstrates that this new rdrp-dependent dicer-independent regulatory pathway, which does not produce sRNA molecules of discrete sizes, controls the expression of target genes promoting the specific degradation of mRNAs by a previously unknown RNase. This pathway mainly regulates conserved genes involved in metabolism and cellular processes and signaling, such as those required for heme biosynthesis, and controls responses to specific environmental signals. Searching the Mucor genome for candidate RNases to participate in this pathway, and functional analysis of the corresponding knockout mutants, identified a new protein, R3B2. This RNase III-like protein presents unique domain architecture, it is specifically found in basal fungi and, besides its relevant role in the rdrp-dependent dicer-independent pathway, it is also involved in the canonical dicer-dependent RNAi pathway, highlighting its crucial role in the biogenesis and function of regulatory esRNAs. The involvement of RdRPs in RNA degradation could represent the first evolutionary step towards the development of an RNAi mechanism and constitutes a genetic link between mRNA degradation and post-transcriptional gene silencing. Most eukaryotic organisms produce different classes of endogenous small RNA (esRNA) molecules that suppress gene expression through RNA interference (RNAi) pathways. These pathways, which may differ among organisms, are normally involved in genome defense, heterochromatin formation and regulation of genes involved in multiple cellular functions. In the basal fungus Mucor circinelloides, an opportunistic human pathogen, we previously demonstrated that biogenesis of a large group of esRNA molecules requires a basic RNAi machinery consisting of a Dicer-like protein, an Argonaute nuclease and two RNA-dependent RNA polymerases. This canonical dicer-dependent pathway regulates different cellular processes, such as vegetative sporulation. Besides those esRNAs generated by this canonical RNAi pathway, we have identified a new rdrp-dependent dicer-independent esRNA class. These esRNAs are produced by a degradation pathway in which the RdRP proteins signal specific transcripts that will be degraded by a newly identified RNase. This RNase, named R3B2, presents unique domain architecture, can only be found in basal fungi and it is also involved in the canonical dicer-dependent RNAi pathway. Our results expand the role of RdRPs in gene silencing and reveal the involvement of these proteins in a new RNA degradation process that could represent the first step in the evolution of RNAi.
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Affiliation(s)
- Trung Anh Trieu
- Department of Genetics and Microbiology, University of Murcia, Murcia, Spain
| | - Silvia Calo
- Department of Genetics and Microbiology, University of Murcia, Murcia, Spain
| | | | - Ana Vila
- Department of Genetics and Microbiology, University of Murcia, Murcia, Spain
| | - Simon Moxon
- The Genome Analysis Centre, University of East Anglia, Norwich, United Kingdom
| | - Tamas Dalmay
- School of Biological Sciences, University of East Anglia, Norwich, United Kingdom
| | | | - Victoriano Garre
- Department of Genetics and Microbiology, University of Murcia, Murcia, Spain
| | - Rosa M. Ruiz-Vázquez
- Department of Genetics and Microbiology, University of Murcia, Murcia, Spain
- * E-mail:
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Martínez de Alba AE, Moreno AB, Gabriel M, Mallory AC, Christ A, Bounon R, Balzergue S, Aubourg S, Gautheret D, Crespi MD, Vaucheret H, Maizel A. In plants, decapping prevents RDR6-dependent production of small interfering RNAs from endogenous mRNAs. Nucleic Acids Res 2015; 43:2902-13. [PMID: 25694514 PMCID: PMC4357720 DOI: 10.1093/nar/gkv119] [Citation(s) in RCA: 86] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2014] [Revised: 01/16/2015] [Accepted: 02/04/2015] [Indexed: 01/24/2023] Open
Abstract
Cytoplasmic degradation of endogenous RNAs is an integral part of RNA quality control (RQC) and often relies on the removal of the 5' cap structure and their subsequent 5' to 3' degradation in cytoplasmic processing (P-)bodies. In parallel, many eukaryotes degrade exogenous and selected endogenous RNAs through post-transcriptional gene silencing (PTGS). In plants, PTGS depends on small interfering (si)RNAs produced after the conversion of single-stranded RNAs to double-stranded RNAs by the cellular RNA-dependent RNA polymerase 6 (RDR6) in cytoplasmic siRNA-bodies. PTGS and RQC compete for transgene-derived RNAs, but it is unknown whether this competition also occurs for endogenous transcripts. We show that the lethality of decapping mutants is suppressed by impairing RDR6 activity. We establish that upon decapping impairment hundreds of endogenous mRNAs give rise to a new class of rqc-siRNAs, that over-accumulate when RQC processes are impaired, a subset of which depending on RDR6 for their production. We observe that P- and siRNA-bodies often are dynamically juxtaposed, potentially allowing for cross-talk of the two machineries. Our results suggest that the decapping of endogenous RNA limits their entry into the PTGS pathway. We anticipate that the rqc-siRNAs identified in decapping mutants represent a subset of a larger ensemble of endogenous siRNAs.
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MESH Headings
- Arabidopsis/genetics
- Arabidopsis/metabolism
- Arabidopsis Proteins/genetics
- Arabidopsis Proteins/metabolism
- Endoribonucleases/genetics
- Endoribonucleases/metabolism
- Gene Expression Regulation, Plant
- Mutation
- Oligonucleotide Array Sequence Analysis
- Plants, Genetically Modified
- RNA Caps/genetics
- RNA Caps/metabolism
- RNA Interference
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- RNA, Plant/genetics
- RNA, Plant/metabolism
- RNA, Small Interfering/genetics
- RNA, Small Interfering/metabolism
- RNA, Small Untranslated/genetics
- RNA, Small Untranslated/metabolism
- RNA-Dependent RNA Polymerase/genetics
- RNA-Dependent RNA Polymerase/metabolism
- Transcriptome
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Affiliation(s)
| | - Ana Beatriz Moreno
- Institut des Sciences du Végétal, CNRS UPR 2355, SPS Saclay Plant Sciences, Gif-sur-Yvette, France
| | - Marc Gabriel
- Institute for Integrative Biology of the Cell, UMR 9198 - Universite Paris-Sud, Gif-sur-Yvette, France
| | - Allison C Mallory
- Institut Jean-Pierre Bourgin UMR 1318, INRA, SPS Saclay Plant Sciences, Versailles, France
| | - Aurélie Christ
- Institut des Sciences du Végétal, CNRS UPR 2355, SPS Saclay Plant Sciences, Gif-sur-Yvette, France
| | - Rémi Bounon
- Unité de Recherche en Génomique Végétale, UMR INRA 1165-CNRS 8114-UEVE, Evry, France
| | - Sandrine Balzergue
- Unité de Recherche en Génomique Végétale, UMR INRA 1165-CNRS 8114-UEVE, Evry, France
| | - Sebastien Aubourg
- Unité de Recherche en Génomique Végétale, UMR INRA 1165-CNRS 8114-UEVE, Evry, France
| | - Daniel Gautheret
- Institute for Integrative Biology of the Cell, UMR 9198 - Universite Paris-Sud, Gif-sur-Yvette, France
| | - Martin D Crespi
- Institut des Sciences du Végétal, CNRS UPR 2355, SPS Saclay Plant Sciences, Gif-sur-Yvette, France
| | - Hervé Vaucheret
- Institut Jean-Pierre Bourgin UMR 1318, INRA, SPS Saclay Plant Sciences, Versailles, France
| | - Alexis Maizel
- Institut des Sciences du Végétal, CNRS UPR 2355, SPS Saclay Plant Sciences, Gif-sur-Yvette, France Center for Organismal Studies, University of Heidelberg, Germany
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36
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Ma X, Nicole MC, Meteignier LV, Hong N, Wang G, Moffett P. Different roles for RNA silencing and RNA processing components in virus recovery and virus-induced gene silencing in plants. JOURNAL OF EXPERIMENTAL BOTANY 2015; 66:919-32. [PMID: 25385769 DOI: 10.1093/jxb/eru447] [Citation(s) in RCA: 89] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
A major antiviral mechanism in plants is mediated by RNA silencing, which relies on the cleavage of viral dsRNA into virus-derived small interfering RNAs (vsiRNAs) by DICER-like enzymes. Members of the Argonaute (AGO) family of endonucleases then use these vsiRNA as guides to target viral RNA. This can result in a phenomenon known as recovery, whereby the plant silences viral gene expression and recovers from viral symptoms. Endogenous mRNAs can also be targeted by vsiRNAs in a phenomenon known as virus-induced gene silencing (VIGS). Although related to other RNA silencing mechanisms, it has not been established if recovery and VIGS are mediated by the same molecular mechanisms. We used tobacco rattle virus (TRV) carrying a fragment of the phytoene desaturase (PDS) gene (TRV-PDS) or expressing green fluorescent protein (TRV-GFP) as readouts for VIGS and recovery, respectively, in Arabidopsis ago mutants. Our results demonstrated roles for AGO2 and AGO4 in susceptibility to TRV, whereas VIGS of endogenous genes appeared to be largely mediated by AGO1. However, recovery appeared to be mediated by different components, as all the aforementioned mutants were able to recover from TRV-GFP inoculation. TRV RNAs from recovered plants associated less with ribosomes, suggesting that recovery involves translational repression of viral transcripts. Translationally repressed RNAs often accumulate in RNA processing bodies (PBs), where they are eventually processed by decapping enzymes. Consistent with this, we found that viral recovery induced increased PB formation and that a decapping mutant (DCP2) showed increased VIGS and virus RNA accumulation, indicating an important role for PBs in eliminating viral RNA.
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Affiliation(s)
- Xiaofang Ma
- State Key Laboratory of Agricultural Microbiology, Wuhan, Hubei 430070, PR China College of Plant Science and Technology, Huazhong Agricultural University, Wuhan, Hubei 430070, PR China Université de Sherbrooke, Département de Biologie, 2500 Boulevard de l'Université, Sherbrooke J1K 2R1, QC, Canada
| | - Marie-Claude Nicole
- Université de Sherbrooke, Département de Biologie, 2500 Boulevard de l'Université, Sherbrooke J1K 2R1, QC, Canada
| | - Louis-Valentin Meteignier
- Université de Sherbrooke, Département de Biologie, 2500 Boulevard de l'Université, Sherbrooke J1K 2R1, QC, Canada
| | - Ni Hong
- State Key Laboratory of Agricultural Microbiology, Wuhan, Hubei 430070, PR China College of Plant Science and Technology, Huazhong Agricultural University, Wuhan, Hubei 430070, PR China
| | - Guoping Wang
- State Key Laboratory of Agricultural Microbiology, Wuhan, Hubei 430070, PR China College of Plant Science and Technology, Huazhong Agricultural University, Wuhan, Hubei 430070, PR China
| | - Peter Moffett
- Université de Sherbrooke, Département de Biologie, 2500 Boulevard de l'Université, Sherbrooke J1K 2R1, QC, Canada
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Ruiz-Vázquez RM, Nicolás FE, Torres-Martínez S, Garre V. Distinct RNAi Pathways in the Regulation of Physiology and Development in the Fungus Mucor circinelloides. ADVANCES IN GENETICS 2015; 91:55-102. [DOI: 10.1016/bs.adgen.2015.07.002] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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Ivanov KI, Eskelin K, Lõhmus A, Mäkinen K. Molecular and cellular mechanisms underlying potyvirus infection. J Gen Virol 2014; 95:1415-1429. [DOI: 10.1099/vir.0.064220-0] [Citation(s) in RCA: 90] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Potyviruses represent one of the most economically important and widely distributed groups of plant viruses. Despite considerable progress towards understanding the cellular and molecular basis of their pathogenicity, many questions remain about the mechanisms by which potyviruses suppress host defences and create an optimal intracellular environment for viral translation, replication, assembly and spread. The review focuses on the multifunctional roles of potyviral proteins and their interplay with various host factors in different compartments of the infected cell. We place special emphasis on the recently discovered and currently putative mechanisms by which potyviruses subvert the normal functions of different cellular organelles in order to establish an efficient and productive infection.
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Affiliation(s)
- K. I. Ivanov
- Department of Food and Environmental Sciences, PO Box 56, 00014 University of Helsinki, Finland
| | - K. Eskelin
- Department of Food and Environmental Sciences, PO Box 56, 00014 University of Helsinki, Finland
| | - A. Lõhmus
- Department of Food and Environmental Sciences, PO Box 56, 00014 University of Helsinki, Finland
| | - K. Mäkinen
- Department of Food and Environmental Sciences, PO Box 56, 00014 University of Helsinki, Finland
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Mäkinen K, Hafrén A. Intracellular coordination of potyviral RNA functions in infection. FRONTIERS IN PLANT SCIENCE 2014; 5:110. [PMID: 24723931 PMCID: PMC3972461 DOI: 10.3389/fpls.2014.00110] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/29/2013] [Accepted: 03/07/2014] [Indexed: 05/26/2023]
Abstract
Establishment of an infection cycle requires mechanisms to allocate the genomes of (+)-stranded RNA viruses in a balanced ratio to translation, replication, encapsidation, and movement, as well as mechanisms to prevent translocation of viral RNA (vRNA) to cellular RNA degradation pathways. The ratio of vRNA allocated to various functions is likely balanced by the availability of regulatory proteins or competition of the interaction sites within regulatory ribonucleoprotein complexes. Due to the transient nature of viral processes and the interdependency between vRNA pathways, it is technically demanding to work out the exact molecular mechanisms underlying vRNA regulation. A substantial number of viral and host proteins have been identified that facilitate the steps that lead to the assembly of a functional potyviral RNA replication complex and their fusion with chloroplasts. Simultaneously with on-going viral replication, part of the replicated potyviral RNA enters movement pathways. Although not much is known about the processes of potyviral RNA release from viral replication complexes, the molecular interactions involved in these processes determine the fate of the replicated vRNA. Some viral and host cell proteins have been described that direct replicated potyviral RNA to translation to enable potyviral gene expression and productive infection. The antiviral defense of the cell causes vRNA degradation by RNA silencing. We hypothesize that also plant pathways involved in mRNA decay may have a role in the coordination of potyviral RNA expression. In this review, we discuss the roles of different potyviral and host proteins in the coordination of various potyviral RNA functions.
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Affiliation(s)
- Kristiina Mäkinen
- Department of Food and Environmental Sciences, University of HelsinkiHelsinki, Finland
| | - Anders Hafrén
- Department of Food and Environmental Sciences, University of HelsinkiHelsinki, Finland
- Department of Plant Biology and Forest Genetics, Swedish University of Agricultural SciencesUppsala, Sweden
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Shin MR, Natsuume M, Matsumoto T, Hanaoka M, Imai M, Iijima K, Oka SI, Adachi E, Kodama H. Sense transgene-induced post-transcriptional gene silencing in tobacco compromises the splicing of endogenous counterpart genes. PLoS One 2014; 9:e87869. [PMID: 24586294 PMCID: PMC3931610 DOI: 10.1371/journal.pone.0087869] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2013] [Accepted: 12/31/2013] [Indexed: 11/23/2022] Open
Abstract
Sense transgene-induced post-transcriptional gene silencing (S-PTGS) is thought to be a type of RNA silencing in which ARGONAUTE1 directs the small interfering RNA (siRNA)-mediated cleavage of a target mRNA in the cytoplasm. Here, we report that the altered splicing of endogenous counterpart genes is a main cause for the reduction of their mature mRNA levels. After the S-PTGS of a tobacco endoplasmic reticulum ω-3 fatty acid desaturase (NtFAD3) gene, 3'-truncated, polyadenylated endo-NtFAD3 transcripts and 5'-truncated, intron-containing endo-NtFAD3 transcripts were detected in the total RNA fraction. Although transcription proceeded until the last exon of the endogenous NtFAD3 gene, intron-containing NtFAD3 transcripts accumulated in the nucleus of the S-PTGS plants. Several intron-containing NtFAD3 transcripts harboring most of the exon sequences were generated when an endogenous silencing suppressor gene, rgs-CaM, was overexpressed in the S-PTGS plants. These intron-containing NtFAD3 splice variants were generated in the presence of NtFAD3 siRNAs that are homologous to the nucleotide sequences of these splice variants. The results of this study indicate that the inhibition of endo-NtFAD3 gene expression is primarily directed via the alteration of splicing and not by cytoplasmic slicer activity. Our results suggest that the transgene and intron-containing endogenous counterpart genes are differentially suppressed in S-PTGS plants.
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Affiliation(s)
- Mi-Rae Shin
- Graduate School of Advanced Integration Science, Chiba University, Inage-ku, Chiba, Japan
| | - Masaya Natsuume
- Graduate School of Horticulture, Chiba University, Chiba, Japan
| | - Takashi Matsumoto
- Genome Research Center, NODAI Research Institute, Tokyo University of Agriculture, Setagaya-ku, Tokyo, Japan
| | | | - Misaki Imai
- Genome Research Center, NODAI Research Institute, Tokyo University of Agriculture, Setagaya-ku, Tokyo, Japan
| | - Ken Iijima
- Department of Applied Biology and Chemistry, Tokyo University of Agriculture, Setagaya-ku, Tokyo, Japan
| | - Shin-ichiro Oka
- Graduate School of Horticulture, Chiba University, Chiba, Japan
| | - Eri Adachi
- Graduate School of Science and Technology, Chiba University, Inage-ku, Chiba, Japan
| | - Hiroaki Kodama
- Graduate School of Advanced Integration Science, Chiba University, Inage-ku, Chiba, Japan
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Moreno AB, Martínez de Alba AE, Bardou F, Crespi MD, Vaucheret H, Maizel A, Mallory AC. Cytoplasmic and nuclear quality control and turnover of single-stranded RNA modulate post-transcriptional gene silencing in plants. Nucleic Acids Res 2013; 41:4699-708. [PMID: 23482394 PMCID: PMC3632135 DOI: 10.1093/nar/gkt152] [Citation(s) in RCA: 90] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Eukaryotic RNA quality control (RQC) uses both endonucleolytic and exonucleolytic degradation to eliminate dysfunctional RNAs. In addition, endogenous and exogenous RNAs are degraded through post-transcriptional gene silencing (PTGS), which is triggered by the production of double-stranded (ds)RNAs and proceeds through short-interfering (si)RNA-directed ARGONAUTE-mediated endonucleolytic cleavage. Compromising cytoplasmic or nuclear 5'-3' exoribonuclease function enhances sense-transgene (S)-PTGS in Arabidopsis, suggesting that these pathways compete for similar RNA substrates. Here, we show that impairing nonsense-mediated decay, deadenylation or exosome activity enhanced S-PTGS, which requires host RNA-dependent RNA polymerase 6 (RDR6/SGS2/SDE1) and SUPPRESSOR OF GENE SILENCING 3 (SGS3) for the transformation of single-stranded RNA into dsRNA to trigger PTGS. However, these RQC mutations had no effect on inverted-repeat-PTGS, which directly produces hairpin dsRNA through transcription. Moreover, we show that these RQC factors are nuclear and cytoplasmic and are found in two RNA degradation foci in the cytoplasm: siRNA-bodies and processing-bodies. We propose a model of single-stranded RNA tug-of-war between RQC and S-PTGS that ensures the correct partitioning of RNA substrates among these RNA degradation pathways.
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Affiliation(s)
- Ana Beatriz Moreno
- Institut des Sciences du Végétal, CNRS UPR 2355, SPS Saclay Plant Sciences, 91198 Gif-sur-Yvette, France
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