1
|
Deng X, Yao Q, Horvath A, Jiang Z, Zhao J, Fischer T, Sugiyama T. The fission yeast ortholog of Coilin, Mug174, forms Cajal body-like nuclear condensates and is essential for cellular quiescence. Nucleic Acids Res 2024; 52:9174-9192. [PMID: 38828770 PMCID: PMC11347179 DOI: 10.1093/nar/gkae463] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2023] [Revised: 05/08/2024] [Accepted: 05/16/2024] [Indexed: 06/05/2024] Open
Abstract
The Cajal body, a nuclear condensate, is crucial for ribonucleoprotein assembly, including small nuclear RNPs (snRNPs). While Coilin has been identified as an integral component of Cajal bodies, its exact function remains unclear. Moreover, no Coilin ortholog has been found in unicellular organisms to date. This study unveils Mug174 (Meiosis-upregulated gene 174) as the Coilin ortholog in the fission yeast Schizosaccharomyces pombe. Mug174 forms phase-separated condensates in vitro and is often associated with the nucleolus and the cleavage body in vivo. The generation of Mug174 foci relies on the trimethylguanosine (TMG) synthase Tgs1. Moreover, Mug174 interacts with Tgs1 and U snRNAs. Deletion of the mug174+ gene in S. pombe causes diverse pleiotropic phenotypes, encompassing defects in vegetative growth, meiosis, pre-mRNA splicing, TMG capping of U snRNAs, and chromosome segregation. In addition, we identified weak homology between Mug174 and human Coilin. Notably, human Coilin expressed in fission yeast colocalizes with Mug174. Critically, Mug174 is indispensable for the maintenance of and transition from cellular quiescence. These findings highlight the Coilin ortholog in fission yeast and suggest that the Cajal body is implicated in cellular quiescence, thereby preventing human diseases.
Collapse
Affiliation(s)
- Xiaoling Deng
- School of Life Science and Technology, ShanghaiTech University, Shanghai 201210, China
| | - Qinglian Yao
- School of Life Science and Technology, ShanghaiTech University, Shanghai 201210, China
| | - Attila Horvath
- The John Curtin School of Medical Research, The Australian National University, Canberra 2601, Australia
| | - Ziling Jiang
- School of Life Science and Technology, ShanghaiTech University, Shanghai 201210, China
| | - Junjie Zhao
- School of Life Science and Technology, ShanghaiTech University, Shanghai 201210, China
| | - Tamás Fischer
- The John Curtin School of Medical Research, The Australian National University, Canberra 2601, Australia
| | - Tomoyasu Sugiyama
- School of Life Science and Technology, ShanghaiTech University, Shanghai 201210, China
| |
Collapse
|
2
|
Lozano-Durán R. Viral Recognition and Evasion in Plants. ANNUAL REVIEW OF PLANT BIOLOGY 2024; 75:655-677. [PMID: 39038248 DOI: 10.1146/annurev-arplant-060223-030224] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/24/2024]
Abstract
Viruses, causal agents of devastating diseases in plants, are obligate intracellular pathogens composed of a nucleic acid genome and a limited number of viral proteins. The diversity of plant viruses, their diminutive molecular nature, and their symplastic localization pose challenges to understanding the interplay between these pathogens and their hosts in the currently accepted framework of plant innate immunity. It is clear, nevertheless, that plants can recognize the presence of a virus and activate antiviral immune responses, although our knowledge of the breadth of invasion signals and the underpinning sensing events is far from complete. Below, I discuss some of the demonstrated or hypothesized mechanisms enabling viral recognition in plants, the step preceding the onset of antiviral immunity, as well as the strategies viruses have evolved to evade or suppress their detection.
Collapse
Affiliation(s)
- Rosa Lozano-Durán
- Center for Molecular Plant Biology (ZMBP), Eberhard-Karls University Tübingen, Tübingen, Germany;
| |
Collapse
|
3
|
Shang B, Li C, Zhang X. How intrinsically disordered proteins order plant gene silencing. Trends Genet 2024; 40:260-275. [PMID: 38296708 PMCID: PMC10932933 DOI: 10.1016/j.tig.2023.12.009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2023] [Revised: 12/25/2023] [Accepted: 12/29/2023] [Indexed: 02/02/2024]
Abstract
Intrinsically disordered proteins (IDPs) and proteins with intrinsically disordered regions (IDRs) possess low sequence complexity of amino acids and display non-globular tertiary structures. They can act as scaffolds, form regulatory hubs, or trigger biomolecular condensation to control diverse aspects of biology. Emerging evidence has recently implicated critical roles of IDPs and IDR-contained proteins in nuclear transcription and cytoplasmic post-transcriptional processes, among other molecular functions. We here summarize the concepts and organizing principles of IDPs. We then illustrate recent progress in understanding the roles of key IDPs in machineries that regulate transcriptional and post-transcriptional gene silencing (PTGS) in plants, aiming at highlighting new modes of action of IDPs in controlling biological processes.
Collapse
Affiliation(s)
- Baoshuan Shang
- National Key Laboratory of Cotton Bio-breeding and Integrated Utilization (Henan University), State Key Laboratory of Crop Stress Adaptation and Improvement, School of Life Sciences, Henan University, Kaifeng 475004, China; Department of Biochemistry and Biophysics, Texas A&M University, College Station, TX 77843, USA
| | - Changhao Li
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, TX 77843, USA
| | - Xiuren Zhang
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, TX 77843, USA; Department of Biology, Texas A&M University, College Station, TX 77843, USA.
| |
Collapse
|
4
|
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.
Collapse
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
| |
Collapse
|
5
|
Liang C, Wang X, He H, Xu C, Cui J. Beyond Loading: Functions of Plant ARGONAUTE Proteins. Int J Mol Sci 2023; 24:16054. [PMID: 38003244 PMCID: PMC10671604 DOI: 10.3390/ijms242216054] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2023] [Revised: 10/31/2023] [Accepted: 11/04/2023] [Indexed: 11/26/2023] Open
Abstract
ARGONAUTE (AGO) proteins are key components of the RNA-induced silencing complex (RISC) that mediates gene silencing in eukaryotes. Small-RNA (sRNA) cargoes are selectively loaded into different members of the AGO protein family and then target complementary sequences to in-duce transcriptional repression, mRNA cleavage, or translation inhibition. Previous reviews have mainly focused on the traditional roles of AGOs in specific biological processes or on the molecular mechanisms of sRNA sorting. In this review, we summarize the biological significance of canonical sRNA loading, including the balance among distinct sRNA pathways, cross-regulation of different RISC activities during plant development and defense, and, especially, the emerging roles of AGOs in sRNA movement. We also discuss recent advances in novel non-canonical functions of plant AGOs. Perspectives for future functional studies of this evolutionarily conserved eukaryotic protein family will facilitate a more comprehensive understanding of the multi-faceted AGO proteins.
Collapse
Affiliation(s)
| | | | | | | | - Jie Cui
- Guangdong Provincial Key Laboratory for Plant Epigenetics, College of Life Sciences and Oceanography, Shenzhen University, Shenzhen 518060, China; (C.L.); (X.W.); (H.H.); (C.X.)
| |
Collapse
|
6
|
Taliansky ME, Love AJ, Kołowerzo-Lubnau A, Smoliński DJ. Cajal bodies: Evolutionarily conserved nuclear biomolecular condensates with properties unique to plants. THE PLANT CELL 2023; 35:3214-3235. [PMID: 37202374 PMCID: PMC10473218 DOI: 10.1093/plcell/koad140] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/05/2023] [Revised: 04/24/2023] [Accepted: 04/27/2023] [Indexed: 05/20/2023]
Abstract
Proper orchestration of the thousands of biochemical processes that are essential to the life of every cell requires highly organized cellular compartmentalization of dedicated microenvironments. There are 2 ways to create this intracellular segregation to optimize cellular function. One way is to create specific organelles, enclosed spaces bounded by lipid membranes that regulate macromolecular flux in and out of the compartment. A second way is via membraneless biomolecular condensates that form due to to liquid-liquid phase separation. Although research on these membraneless condensates has historically been performed using animal and fungal systems, recent studies have explored basic principles governing the assembly, properties, and functions of membraneless compartments in plants. In this review, we discuss how phase separation is involved in a variety of key processes occurring in Cajal bodies (CBs), a type of biomolecular condensate found in nuclei. These processes include RNA metabolism, formation of ribonucleoproteins involved in transcription, RNA splicing, ribosome biogenesis, and telomere maintenance. Besides these primary roles of CBs, we discuss unique plant-specific functions of CBs in RNA-based regulatory pathways such as nonsense-mediated mRNA decay, mRNA retention, and RNA silencing. Finally, we summarize recent progress and discuss the functions of CBs in responses to pathogen attacks and abiotic stresses, responses that may be regulated via mechanisms governed by polyADP-ribosylation. Thus, plant CBs are emerging as highly complex and multifunctional biomolecular condensates that are involved in a surprisingly diverse range of molecular mechanisms that we are just beginning to appreciate.
Collapse
Affiliation(s)
| | - Andrew J Love
- The James Hutton Institute, Invergowrie, Dundee DD2 5DA, UK
| | - Agnieszka Kołowerzo-Lubnau
- Department of Cellular and Molecular Biology, Nicolaus Copernicus University, Lwowska 1, 87-100 Torun, Poland
- Centre for Modern Interdisciplinary Technologies, Nicolaus Copernicus University, Wilenska 4, 87-100 Torun, Poland
| | - Dariusz Jan Smoliński
- Department of Cellular and Molecular Biology, Nicolaus Copernicus University, Lwowska 1, 87-100 Torun, Poland
- Centre for Modern Interdisciplinary Technologies, Nicolaus Copernicus University, Wilenska 4, 87-100 Torun, Poland
| |
Collapse
|
7
|
Abulfaraj AA, Alhoraibi HM, Mariappan K, Bigeard J, Zhang H, Almeida-Trapp M, Artyukh O, Abdulhakim F, Parween S, Pflieger D, Blilou I, Hirt H, Rayapuram N. Analysis of the Arabidopsis coilin mutant reveals a positive role of AtCOILIN in plant immunity. PLANT PHYSIOLOGY 2022; 190:745-761. [PMID: 35674377 PMCID: PMC9434284 DOI: 10.1093/plphys/kiac280] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/20/2022] [Accepted: 05/18/2022] [Indexed: 06/15/2023]
Abstract
Biogenesis of ribonucleoproteins occurs in dynamic subnuclear compartments called Cajal bodies (CBs). COILIN is a critical scaffolding component essential for CB formation, composition, and activity. We recently showed that Arabidopsis (Arabidopsis thaliana) AtCOILIN is phosphorylated in response to bacterial elicitor treatment. Here, we further investigated the role of AtCOILIN in plant innate immunity. Atcoilin mutants are compromised in defense responses to bacterial pathogens. Besides confirming a role of AtCOILIN in alternative splicing (AS), Atcoilin showed differential expression of genes that are distinct from those of AS, including factors involved in RNA biogenesis, metabolism, plant immunity, and phytohormones. Atcoilin mutant plants have reduced levels of defense phytohormones. As expected, the mutant plants were more sensitive to the necrotrophic fungal pathogen Botrytis cinerea. Our findings reveal an important role for AtCOILIN in innate plant immunity.
Collapse
Affiliation(s)
- Aala A Abulfaraj
- Biological Sciences Department, College of Science & Arts, King Abdulaziz University, Rabigh 21911, Saudi Arabia
| | - Hanna M Alhoraibi
- Department of Biochemistry, Faculty of Science, King Abdulaziz University, 21551 Jeddah, Saudi Arabia
| | - Kiruthiga Mariappan
- Division of Biological and Environmental Sciences and Engineering, King Abdullah University of Science and Technology, Thuwal 23955, Saudi Arabia
| | - Jean Bigeard
- Institute of Plant Sciences Paris Saclay (IPS2), CNRS, INRAE, Univ Evry, Université Paris-Saclay, Université de Paris, Orsay 91405, France
| | - Huoming Zhang
- Corelabs, King Abdullah University of Science and Technology, Thuwal 23955, Saudi Arabia
| | - Marilia Almeida-Trapp
- Division of Biological and Environmental Sciences and Engineering, King Abdullah University of Science and Technology, Thuwal 23955, Saudi Arabia
| | - Olga Artyukh
- Division of Biological and Environmental Sciences and Engineering, King Abdullah University of Science and Technology, Thuwal 23955, Saudi Arabia
| | - Fatimah Abdulhakim
- Division of Biological and Environmental Sciences and Engineering, King Abdullah University of Science and Technology, Thuwal 23955, Saudi Arabia
| | - Sabiha Parween
- Division of Biological and Environmental Sciences and Engineering, King Abdullah University of Science and Technology, Thuwal 23955, Saudi Arabia
| | - Delphine Pflieger
- Universite Grenoble Alpes, INSERM, CEA, UMR BioSanté U1292, CNRS, CEA, FR2048 38000, Grenoble, France
| | - Ikram Blilou
- Division of Biological and Environmental Sciences and Engineering, King Abdullah University of Science and Technology, Thuwal 23955, Saudi Arabia
| | | | | |
Collapse
|
8
|
Muñoz-Díaz E, Sáez-Vásquez J. Nuclear dynamics: Formation of bodies and trafficking in plant nuclei. FRONTIERS IN PLANT SCIENCE 2022; 13:984163. [PMID: 36082296 PMCID: PMC9445803 DOI: 10.3389/fpls.2022.984163] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/01/2022] [Accepted: 08/04/2022] [Indexed: 06/01/2023]
Abstract
The existence of the nucleus distinguishes prokaryotes and eukaryotes. Apart from containing most of the genetic material, the nucleus possesses several nuclear bodies composed of protein and RNA molecules. The nucleus is separated from the cytoplasm by a double membrane, regulating the trafficking of molecules in- and outwards. Here, we investigate the composition and function of the different plant nuclear bodies and molecular clues involved in nuclear trafficking. The behavior of the nucleolus, Cajal bodies, dicing bodies, nuclear speckles, cyclophilin-containing bodies, photobodies and DNA damage foci is analyzed in response to different abiotic stresses. Furthermore, we research the literature to collect the different protein localization signals that rule nucleocytoplasmic trafficking. These signals include the different types of nuclear localization signals (NLSs) for nuclear import, and the nuclear export signals (NESs) for nuclear export. In contrast to these unidirectional-movement signals, the existence of nucleocytoplasmic shuttling signals (NSSs) allows bidirectional movement through the nuclear envelope. Likewise, nucleolar signals are also described, which mainly include the nucleolar localization signals (NoLSs) controlling nucleolar import. In contrast, few examples of nucleolar export signals, called nucleoplasmic localization signals (NpLSs) or nucleolar export signals (NoESs), have been reported. The existence of consensus sequences for these localization signals led to the generation of prediction tools, allowing the detection of these signals from an amino acid sequence. Additionally, the effect of high temperatures as well as different post-translational modifications in nuclear and nucleolar import and export is discussed.
Collapse
Affiliation(s)
- Eduardo Muñoz-Díaz
- Centre National de la Recherche Scientifique (CNRS), Laboratoire Génome et Développement des Plantes, UMR 5096, Perpignan, France
- Univ. Perpignan Via Domitia, Laboratoire Génome et Développement des Plantes, UMR 5096, Perpignan, France
| | - Julio Sáez-Vásquez
- Centre National de la Recherche Scientifique (CNRS), Laboratoire Génome et Développement des Plantes, UMR 5096, Perpignan, France
- Univ. Perpignan Via Domitia, Laboratoire Génome et Développement des Plantes, UMR 5096, Perpignan, France
| |
Collapse
|
9
|
Wang L, Lozano-Duran R. Arabidopsis AGO4 loses its Cajal body localization when heterologously expressed in Nicotiana benthamiana. Commun Integr Biol 2022; 15:88-91. [PMID: 35356538 PMCID: PMC8959500 DOI: 10.1080/19420889.2022.2051843] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
In plants, the RNA-directed DNA methylation (RdDM) pathway plays a major role in establishing DNA methylation. At least some components of the RdDM machinery, including the central component AGO4, are known to concentrate in a subnuclear compartment called the Cajal body in the model plant Arabidopsis thaliana. The molecular underpinnings of Cajal body localization, however, have remained elusive so far. Here, we found that Arabidopsis AGO4 (AtAGO4) fused to GFP does not present its typical Cajal body localization, when transiently expressed in Nicotiana benthamiana. Nevertheless, the endogenous AGO4 protein from N. benthamiana shows a clear accumulation in the Cajal body. Thus, our results suggest that the Cajal body localization of AtAGO4 requires specific molecular machinery that cannot be replaced by orthologues in N. benthamiana. This study presents an experimental system that could lead to mechanistic insights into the targeting of proteins to and localization in the Cajal body in plants.
Collapse
Affiliation(s)
- Liping Wang
- Shanghai Center for Plant Stress Biology, Center for Excellence in Molecular Plant Science, Chinese Academy of Sciences, Shanghai, China
| | - Rosa Lozano-Duran
- Shanghai Center for Plant Stress Biology, Center for Excellence in Molecular Plant Science, Chinese Academy of Sciences, Shanghai, China.,Department of Plant Biochemistry, Centre for Plant Molecular Biology (ZMBP), Eberhard Karls University, Tübingen, Germany
| |
Collapse
|
10
|
Lei Z, Wang L, Kim EY, Cho J. Phase separation of chromatin and small RNA pathways in plants. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2021; 108:1256-1265. [PMID: 34585805 DOI: 10.1111/tpj.15517] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/18/2021] [Revised: 09/18/2021] [Accepted: 09/25/2021] [Indexed: 06/13/2023]
Abstract
Gene expression can be modulated by epigenetic mechanisms, including chromatin modifications and small regulatory RNAs. These pathways are unevenly distributed within a cell and usually take place in specific intracellular regions. Unfortunately, the fundamental driving force and biological relevance of such spatial differentiation is largely unknown. Liquid-liquid phase separation (LLPS) is a natural propensity of demixing liquid phases and has been recently suggested to mediate the formation of biomolecular condensates that are relevant to diverse cellular processes. LLPS provides a mechanistic explanation for the self-assembly of subcellular structures by which the efficiency and specificity of certain cellular reactions are achieved. In plants, LLPS has been observed for several key factors in the chromatin and small RNA pathways. For example, the formation of facultative and obligate heterochromatin involves the LLPS of multiple relevant factors. In addition, phase separation is observed in a set of proteins acting in microRNA biogenesis and the small interfering RNA pathway. In this Focused Review, we highlight and discuss the recent findings regarding phase separation in the epigenetic mechanisms of plants.
Collapse
Affiliation(s)
- Zhen Lei
- National Key Laboratory of Plant Molecular Genetics, CAS Center for Excellence in Molecular Plant Sciences (CEMPS), Shanghai Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Shanghai, 200032, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Ling Wang
- National Key Laboratory of Plant Molecular Genetics, CAS Center for Excellence in Molecular Plant Sciences (CEMPS), Shanghai Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Shanghai, 200032, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Eun Yu Kim
- National Key Laboratory of Plant Molecular Genetics, CAS Center for Excellence in Molecular Plant Sciences (CEMPS), Shanghai Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Shanghai, 200032, China
| | - Jungnam Cho
- National Key Laboratory of Plant Molecular Genetics, CAS Center for Excellence in Molecular Plant Sciences (CEMPS), Shanghai Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Shanghai, 200032, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
- CAS-JIC Centre of Excellence for Plant and Microbial Science (CEPAMS), Chinese Academy of Sciences, Shanghai, 200032, China
| |
Collapse
|
11
|
Jiang J, Liu J, Sanders D, Qian S, Ren W, Song J, Liu F, Zhong X. UVR8 interacts with de novo DNA methyltransferase and suppresses DNA methylation in Arabidopsis. NATURE PLANTS 2021; 7:184-197. [PMID: 33495557 PMCID: PMC7889724 DOI: 10.1038/s41477-020-00843-4] [Citation(s) in RCA: 31] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/15/2020] [Accepted: 12/17/2020] [Indexed: 05/03/2023]
Abstract
DNA methylation is an important epigenetic gene regulatory mechanism conserved in eukaryotes. Emerging evidence shows DNA methylation alterations in response to environmental cues. However, the mechanism of how cells sense these signals and reprogramme the methylation landscape is poorly understood. Here, we uncovered a connection between ultraviolet B (UVB) signalling and DNA methylation involving UVB photoreceptor (UV RESISTANCE LOCUS 8 (UVR8)) and a de novo DNA methyltransferase (DOMAINS REARRANGED METHYLTRANSFERASE 2 (DRM2)) in Arabidopsis. We demonstrated that UVB acts through UVR8 to inhibit DRM2-mediated DNA methylation and transcriptional de-repression. Interestingly, DNA transposons with high DNA methylation are more sensitive to UVB irradiation. Mechanistically, UVR8 interacts with and negatively regulates DRM2 by preventing its chromatin association and inhibiting the methyltransferase activity. Collectively, this study identifies UVB as a potent inhibitor of DNA methylation and provides mechanistic insights into how signalling transduction cascades intertwine with chromatin to guide genome functions.
Collapse
Affiliation(s)
- Jianjun Jiang
- Institute of Plant Protection, Jiangsu Academy of Agricultural Sciences, Jiangsu Key Laboratory for Food Quality and Safety-State Key Laboratory Cultivation Base of Ministry of Science and Technology, Nanjing, Jiangsu, China
- Laboratory of Genetics & Wisconsin Institute for Discovery, University of Wisconsin-Madison, Madison, WI, USA
| | - Jie Liu
- Laboratory of Genetics & Wisconsin Institute for Discovery, University of Wisconsin-Madison, Madison, WI, USA
| | - Dean Sanders
- Laboratory of Genetics & Wisconsin Institute for Discovery, University of Wisconsin-Madison, Madison, WI, USA
| | - Shuiming Qian
- Laboratory of Genetics & Wisconsin Institute for Discovery, University of Wisconsin-Madison, Madison, WI, USA
| | - Wendan Ren
- Department of Biochemistry, University of California, Riverside, CA, USA
| | - Jikui Song
- Department of Biochemistry, University of California, Riverside, CA, USA
| | - Fengquan Liu
- Institute of Plant Protection, Jiangsu Academy of Agricultural Sciences, Jiangsu Key Laboratory for Food Quality and Safety-State Key Laboratory Cultivation Base of Ministry of Science and Technology, Nanjing, Jiangsu, China.
| | - Xuehua Zhong
- Laboratory of Genetics & Wisconsin Institute for Discovery, University of Wisconsin-Madison, Madison, WI, USA.
| |
Collapse
|
12
|
Wang L, Ding Y, He L, Zhang G, Zhu JK, Lozano-Duran R. A virus-encoded protein suppresses methylation of the viral genome through its interaction with AGO4 in the Cajal body. eLife 2020; 9:e55542. [PMID: 33064077 PMCID: PMC7567605 DOI: 10.7554/elife.55542] [Citation(s) in RCA: 34] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2020] [Accepted: 09/23/2020] [Indexed: 12/11/2022] Open
Abstract
In plants, establishment of de novo DNA methylation is regulated by the RNA-directed DNA methylation (RdDM) pathway. RdDM machinery is known to concentrate in the Cajal body, but the biological significance of this localization has remained elusive. Here, we show that the antiviral methylation of the Tomato yellow leaf curl virus (TYLCV) genome requires the Cajal body in Nicotiana benthamiana cells. Methylation of the viral genome is countered by a virus-encoded protein, V2, which interacts with the central RdDM component AGO4, interfering with its binding to the viral DNA; Cajal body localization of the V2-AGO4 interaction is necessary for the viral protein to exert this function. Taken together, our results draw a long sought-after functional connection between RdDM, the Cajal body, and antiviral DNA methylation, paving the way for a deeper understanding of DNA methylation and antiviral defences in plants.
Collapse
Affiliation(s)
- Liping Wang
- Shanghai Center for Plant Stress Biology, Center for Excellence in Molecular Plant Sciences, Chinese Academy of SciencesBeijingChina
- University of the Chinese Academy of SciencesBeijingChina
| | - Yi Ding
- Shanghai Center for Plant Stress Biology, Center for Excellence in Molecular Plant Sciences, Chinese Academy of SciencesBeijingChina
- University of the Chinese Academy of SciencesBeijingChina
| | - Li He
- Shanghai Center for Plant Stress Biology, Center for Excellence in Molecular Plant Sciences, Chinese Academy of SciencesBeijingChina
| | - Guiping Zhang
- Shanghai Center for Plant Stress Biology, Center for Excellence in Molecular Plant Sciences, Chinese Academy of SciencesBeijingChina
| | - Jian-Kang Zhu
- Shanghai Center for Plant Stress Biology, Center for Excellence in Molecular Plant Sciences, Chinese Academy of SciencesBeijingChina
| | - Rosa Lozano-Duran
- Shanghai Center for Plant Stress Biology, Center for Excellence in Molecular Plant Sciences, Chinese Academy of SciencesBeijingChina
| |
Collapse
|
13
|
Emenecker RJ, Holehouse AS, Strader LC. Emerging Roles for Phase Separation in Plants. Dev Cell 2020; 55:69-83. [PMID: 33049212 PMCID: PMC7577370 DOI: 10.1016/j.devcel.2020.09.010] [Citation(s) in RCA: 72] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2020] [Revised: 08/19/2020] [Accepted: 09/02/2020] [Indexed: 12/12/2022]
Abstract
The plant cell internal environment is a dynamic, intricate landscape composed of many intracellular compartments. Cells organize some cellular components through formation of biomolecular condensates-non-stoichiometric assemblies of protein and/or nucleic acids. In many cases, phase separation appears to either underly or contribute to the formation of biomolecular condensates. Many canonical membraneless compartments within animal cells form in a manner that is at least consistent with phase separation, including nucleoli, stress granules, Cajal bodies, and numerous additional bodies, regulated by developmental and environmental stimuli. In this Review, we examine the emerging roles for phase separation in plants. Further, drawing on studies carried out in other organisms, we identify cellular phenomenon in plants that might also arise via phase separation. We propose that plants make use of phase separation to a much greater extent than has been previously appreciated, implicating phase separation as an evolutionarily ancient mechanism for cellular organization.
Collapse
Affiliation(s)
- Ryan J Emenecker
- Department of Biology, Washington University, St. Louis, MO 63130, USA; Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO 63110, USA; Center for Science and Engineering Living Systems (CSELS), Washington University, St. Louis, MO 63130, USA; Center for Engineering Mechanobiology, Washington University, St. Louis, MO 63130, USA
| | - Alex S Holehouse
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO 63110, USA; Center for Science and Engineering Living Systems (CSELS), Washington University, St. Louis, MO 63130, USA.
| | - Lucia C Strader
- Center for Science and Engineering Living Systems (CSELS), Washington University, St. Louis, MO 63130, USA; Center for Engineering Mechanobiology, Washington University, St. Louis, MO 63130, USA; Department of Biology, Duke University, Durham, NC 27708, USA.
| |
Collapse
|
14
|
Ding Y, Lozano-Durán R. The Cajal Body in Plant-Virus Interactions. Viruses 2020; 12:E250. [PMID: 32102236 PMCID: PMC7077289 DOI: 10.3390/v12020250] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2020] [Revised: 02/14/2020] [Accepted: 02/18/2020] [Indexed: 01/23/2023] Open
Abstract
Cajal bodies (CBs) are nuclear membraneless bodies composed of proteins and RNA. Although it is known that CBs play a role in RNA metabolism and the formation of functional ribonucleoprotein (RNP) particles, the whole breadth of CB functions is far from being fully elucidated. In this short review, we will summarize and discuss the growing body of evidence pointing to an involvement of this subnuclear compartment in plant-virus interactions.
Collapse
Affiliation(s)
- Yi Ding
- Shanghai Center for Plant Stress Biology, Chinese Academy of Sciences, Shanghai 201602, China;
- Center for Excellence in Molecular Plant Science, Chinese Academy of Sciences, Shanghai 201602, China
- University of the Chinese Academy of Sciences, Beijing 100049, China
| | - Rosa Lozano-Durán
- Shanghai Center for Plant Stress Biology, Chinese Academy of Sciences, Shanghai 201602, China;
- Center for Excellence in Molecular Plant Science, Chinese Academy of Sciences, Shanghai 201602, China
| |
Collapse
|
15
|
Sheu-Gruttadauria J, MacRae IJ. Phase Transitions in the Assembly and Function of Human miRISC. Cell 2018; 173:946-957.e16. [PMID: 29576456 DOI: 10.1016/j.cell.2018.02.051] [Citation(s) in RCA: 178] [Impact Index Per Article: 29.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2017] [Revised: 12/08/2017] [Accepted: 02/21/2018] [Indexed: 12/16/2022]
Abstract
miRISC is a multi-protein assembly that uses microRNAs (miRNAs) to identify mRNAs targeted for repression. Dozens of miRISC-associated proteins have been identified, and interactions between many factors have been examined in detail. However, the physical nature of the complex remains unknown. Here, we show that two core protein components of human miRISC, Argonaute2 (Ago2) and TNRC6B, condense into phase-separated droplets in vitro and in live cells. Phase separation is promoted by multivalent interactions between the glycine/tryptophan (GW)-rich domain of TNRC6B and three evenly spaced tryptophan-binding pockets in the Ago2 PIWI domain. miRISC droplets formed in vitro recruit deadenylation factors and sequester target RNAs from the bulk solution. The condensation of miRISC is accompanied by accelerated deadenylation of target RNAs bound to Ago2. The combined results may explain how miRISC silences mRNAs of varying size and structure and provide experimental evidence that protein-mediated phase separation can facilitate an RNA processing reaction.
Collapse
Affiliation(s)
- Jessica Sheu-Gruttadauria
- Department of Integrative Structural and Computational Biology, The Scripps Research Institute, La Jolla, CA 92037, USA
| | - Ian J MacRae
- Department of Integrative Structural and Computational Biology, The Scripps Research Institute, La Jolla, CA 92037, USA.
| |
Collapse
|
16
|
Love AJ, Yu C, Petukhova NV, Kalinina NO, Chen J, Taliansky ME. Cajal bodies and their role in plant stress and disease responses. RNA Biol 2017; 14:779-790. [PMID: 27726481 PMCID: PMC5519230 DOI: 10.1080/15476286.2016.1243650] [Citation(s) in RCA: 43] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2016] [Revised: 09/19/2016] [Accepted: 09/27/2016] [Indexed: 12/11/2022] Open
Abstract
Cajal bodies (CBs) are distinct sub-nuclear structures that are present in eukaryotic living cells and are often associated with the nucleolus. CBs play important roles in RNA metabolism and formation of RNPs involved in transcription, splicing, ribosome biogenesis, and telomere maintenance. Besides these primary roles, CBs appear to be involved in additional functions that may not be directly related to RNA metabolism and RNP biogenesis. In this review, we assess possible roles of plant CBs in RNA regulatory pathways such as nonsense-mediated mRNA decay and RNA silencing. We also summarize recent progress and discuss new non-canonical functions of plant CBs in responses to stress and disease. It is hypothesized that CBs can regulate these responses via their interaction with poly(ADP ribose)polymerase (PARP), which is known to play an important role in various physiological processes including responses to biotic and abiotic stresses. It is suggested that CBs and their components modify PARP activities and functions.
Collapse
Affiliation(s)
- Andrew J. Love
- Cell and Molecular Sciences, James Hutton Institute, Invergowrie, Dundee, UK
| | - Chulang Yu
- State Key Laboratory Breeding Base for Sustainable Pest and Disease Control, Key Laboratory of Biotechnology in Plant Protection of MOA and Zhejiang Province, Institute of Virology and Biotechnology, Zhejiang Academy of Agricultural Sciences, Hangzhou, China
| | | | - Natalia O. Kalinina
- A.N. Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Leninskie Gory, Moscow, Russia
| | - Jianping Chen
- State Key Laboratory Breeding Base for Sustainable Pest and Disease Control, Key Laboratory of Biotechnology in Plant Protection of MOA and Zhejiang Province, Institute of Virology and Biotechnology, Zhejiang Academy of Agricultural Sciences, Hangzhou, China
| | - Michael E. Taliansky
- Cell and Molecular Sciences, James Hutton Institute, Invergowrie, Dundee, UK
- State Key Laboratory Breeding Base for Sustainable Pest and Disease Control, Key Laboratory of Biotechnology in Plant Protection of MOA and Zhejiang Province, Institute of Virology and Biotechnology, Zhejiang Academy of Agricultural Sciences, Hangzhou, China
| |
Collapse
|
17
|
Bi X, Cheng YJ, Hu B, Ma X, Wu R, Wang JW, Liu C. Nonrandom domain organization of the Arabidopsis genome at the nuclear periphery. Genome Res 2017; 27:1162-1173. [PMID: 28385710 PMCID: PMC5495068 DOI: 10.1101/gr.215186.116] [Citation(s) in RCA: 83] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2016] [Accepted: 04/05/2017] [Indexed: 12/12/2022]
Abstract
The nuclear space is not a homogeneous biochemical environment. Many studies have demonstrated that the transcriptional activity of a gene is linked to its positioning within the nuclear space. Following the discovery of lamin-associated domains (LADs), which are transcriptionally repressed chromatin regions, the nonrandom positioning of chromatin at the nuclear periphery and its biological relevance have been studied extensively in animals. However, it remains unknown whether comparable chromatin organizations exist in plants. Here, using a strategy using restriction enzyme-mediated chromatin immunoprecipitation, we present genome-wide identification of nonrandom domain organization of chromatin at the peripheral zone of Arabidopsis thaliana nuclei. We show that in various tissues, 10%-20% of the regions on the chromosome arms are anchored at the nuclear periphery, and these regions largely overlap between different tissues. Unlike LADs in animals, the identified domains in plants are not gene-poor or A/T-rich. These domains are enriched with silenced protein-coding genes, transposable element genes, and heterochromatic marks, which collectively define a repressed environment. In addition, these domains strongly correlate with our genome-wide chromatin interaction data set (Hi-C) by largely explaining the patterns of chromatin compartments, revealed on Hi-C maps. Moreover, our results reveal a spatial compartment of different DNA methylation pathways that regulate silencing of transposable elements, where the CHH methylation of transposable elements located at the nuclear periphery and in the interior are preferentially mediated by CMT2 and DRM methyltransferases, respectively. Taken together, the results demonstrate functional partitioning of the Arabidopsis genome in the nuclear space.
Collapse
Affiliation(s)
- Xiuli Bi
- Center for Plant Molecular Biology (ZMBP), University of Tübingen, Tübingen 72076, Germany
| | - Ying-Juan Cheng
- National Key Laboratory of Plant Molecular Genetics (NKLPMG), CAS Center for Excellence in Molecular Plant Sciences, Institute of Plant Physiology and Ecology (SIPPE), Shanghai Institutes for Biological Sciences (SIBS), Shanghai 200032, People's Republic of China.,University of Chinese Academy of Sciences, Shanghai 200032, People's Republic of China
| | - Bo Hu
- Center for Plant Molecular Biology (ZMBP), University of Tübingen, Tübingen 72076, Germany
| | - Xiaoli Ma
- Center for Plant Molecular Biology (ZMBP), University of Tübingen, Tübingen 72076, Germany
| | - Rui Wu
- Department of Molecular Biology, Max Planck Institute for Developmental Biology, Tübingen 72076, Germany
| | - Jia-Wei Wang
- National Key Laboratory of Plant Molecular Genetics (NKLPMG), CAS Center for Excellence in Molecular Plant Sciences, Institute of Plant Physiology and Ecology (SIPPE), Shanghai Institutes for Biological Sciences (SIBS), Shanghai 200032, People's Republic of China
| | - Chang Liu
- Center for Plant Molecular Biology (ZMBP), University of Tübingen, Tübingen 72076, Germany
| |
Collapse
|
18
|
Alves CS, Vicentini R, Duarte GT, Pinoti VF, Vincentz M, Nogueira FTS. Genome-wide identification and characterization of tRNA-derived RNA fragments in land plants. PLANT MOLECULAR BIOLOGY 2017; 93:35-48. [PMID: 27681945 DOI: 10.1007/s11103-016-0545-9] [Citation(s) in RCA: 56] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/20/2016] [Accepted: 09/19/2016] [Indexed: 05/06/2023]
Abstract
The manuscript by Alves et al. entitled "Genome-wide identification and characterization of tRNA-derived RNA fragments in land plants" describes the identification and characterization of tRNAderived sRNA fragments in plants. By combining bioinformatic analysis and genetic and molecular approaches, we show that tRF biogenesis does not rely on canonical microRNA/siRNA processing machinery (i.e., independent of DICER-LIKE proteins). Moreover, we provide evidences that the Arabidopsis S-like Ribonuclease 1 (RNS1) might be involved in the biogenesis of tRFs. Detailed analyses showed that plant tRFs are sorted into different types of ARGONAUTE proteins and that they have potential target candidate genes. Our work advances the understanding of the tRF biology in plants by providing evidences that plant and animal tRFs shared common features and raising the hypothesis that an interplay between tRFs and other sRNAs might be important to fine-tune gene expression and protein biosynthesis in plant cells. Small RNA (sRNA) fragments derived from tRNAs (3'-loop, 5'-loop, anti-codon loop), named tRFs, have been reported in several organisms, including humans and plants. Although they may interfere with gene expression, their biogenesis and biological functions in plants remain poorly understood. Here, we capitalized on small RNA sequencing data from distinct species such as Arabidopsis thaliana, Oryza sativa, and Physcomitrella patens to examine the diversity of plant tRFs and provide insight into their properties. In silico analyzes of 19 to 25-nt tRFs derived from 5' (tRF-5s) and 3'CCA (tRF-3s) tRNA loops in these three evolutionary distant species showed that they are conserved and their abundance did not correlate with the number of genomic copies of the parental tRNAs. Moreover, tRF-5 is the most abundant variant in all three species. In silico and in vivo expression analyses unraveled differential accumulation of tRFs in Arabidopsis tissues/organs, suggesting that they are not byproducts of tRNA degradation. We also verified that the biogenesis of most Arabidopsis 19-25 nt tRF-5s and tRF-3s is not primarily dependent on DICER-LIKE proteins, though they seem to be associated with ARGONAUTE proteins and have few potential targets. Finally, we provide evidence that Arabidopsis ribonuclease RNS1 might be involved in the processing and/or degradation of tRFs. Our data support the notion that an interplay between tRFs and other sRNAs might be important to fine tune gene expression and protein biosynthesis in plant cells.
Collapse
Affiliation(s)
- Cristiane S Alves
- Departamento de Genetica, Instituto de Biociencias, Universidade Estadual Paulista (UNESP), Distrito de Rubião Jr., s/n, Botucatu, SP, 18618-970, Brazil
- Laboratorio de Genetica Molecular do Desenvolvimento Vegetal, Departamento de Ciencias Biologicas, ESALQ/USP, Avenida Pádua Dias s/n, 11, Piracicaba, SP, 13418-900, Brazil
| | - Renato Vicentini
- Laboratorio de Bioinformatica e Biologia de Sistemas, Departamento de Genetica, Evoluçao e Bioagentes, Universidade Estadual de Campinas (Unicamp), Campinas, SP, Brazil
| | - Gustavo T Duarte
- Centro de Biologia Molecular e Engenharia Genetica (CBMEG), Universidade Estadual de Campinas (Unicamp), Campinas, SP, Brazil
| | - Vitor F Pinoti
- Departamento de Genetica, Instituto de Biociencias, Universidade Estadual Paulista (UNESP), Distrito de Rubião Jr., s/n, Botucatu, SP, 18618-970, Brazil
| | - Michel Vincentz
- Centro de Biologia Molecular e Engenharia Genetica (CBMEG), Universidade Estadual de Campinas (Unicamp), Campinas, SP, Brazil
| | - Fabio T S Nogueira
- Laboratorio de Genetica Molecular do Desenvolvimento Vegetal, Departamento de Ciencias Biologicas, ESALQ/USP, Avenida Pádua Dias s/n, 11, Piracicaba, SP, 13418-900, Brazil.
| |
Collapse
|
19
|
Limited Contribution of DNA Methylation Variation to Expression Regulation in Arabidopsis thaliana. PLoS Genet 2016; 12:e1006141. [PMID: 27398721 PMCID: PMC4939946 DOI: 10.1371/journal.pgen.1006141] [Citation(s) in RCA: 68] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2015] [Accepted: 06/03/2016] [Indexed: 11/19/2022] Open
Abstract
The extent to which epigenetic variation affects complex traits in natural populations is not known. We addressed this question using transcriptome and DNA methylation data from a sample of 135 sequenced A. thaliana accessions. Across individuals, expression was significantly associated with cis-methylation for hundreds of genes, and many of these associations remained significant after taking SNP effects into account. The pattern of correlations differed markedly between gene body methylation and transposable element methylation. The former was usually positively correlated with expression, and the latter usually negatively correlated, although exceptions were found in both cases. Finally, we developed graphical models of causality that adapt to a sample with heavy population structure, and used them to show that while methylation appears to affect gene expression more often than expression affects methylation, there is also strong support for both being independently controlled. In conclusion, although we find clear evidence for epigenetic regulation, both the number of loci affected and the magnitude of the effects appear to be small compared to the effect of SNPs. It has been demonstrated experimentally that epigenetic variation, in particular DNA methylation, can transmit information across generations. However, it is difficult to evaluate the importance of such effects in natural populations due to complex genetic background effects, making experimental the separation of genetic and epigenetic effects challenging. Here we use quantitative genetic models to test whether epigenetic variation plays a significant role in gene expression variation once genetic variation has been taken into account. In addition, we devise and apply methods that go beyond a simple association framework in order to infer causal relationships. Our results suggest a significant but small epigenetic contribution to expression regulation.
Collapse
|
20
|
Fang X, Qi Y. RNAi in Plants: An Argonaute-Centered View. THE PLANT CELL 2016; 28:272-85. [PMID: 26869699 PMCID: PMC4790879 DOI: 10.1105/tpc.15.00920] [Citation(s) in RCA: 197] [Impact Index Per Article: 24.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/28/2015] [Revised: 12/29/2015] [Accepted: 02/10/2016] [Indexed: 05/18/2023]
Abstract
Argonaute (AGO) family proteins are effectors of RNAi in eukaryotes. AGOs bind small RNAs and use them as guides to silence target genes or transposable elements at the transcriptional or posttranscriptional level. Eukaryotic AGO proteins share common structural and biochemical properties and function through conserved core mechanisms in RNAi pathways, yet plant AGOs have evolved specialized and diversified functions. This Review covers the general features of AGO proteins and highlights recent progress toward our understanding of the mechanisms and functions of plant AGOs.
Collapse
Affiliation(s)
- Xiaofeng Fang
- Center for Plant Biology, School of Life Sciences, Tsinghua University, Beijing 100084, China Tsinghua-Peking Center for Life Sciences, Beijing 100084, China
| | - Yijun Qi
- Center for Plant Biology, School of Life Sciences, Tsinghua University, Beijing 100084, China Tsinghua-Peking Center for Life Sciences, Beijing 100084, China
| |
Collapse
|
21
|
A One Precursor One siRNA Model for Pol IV-Dependent siRNA Biogenesis. Cell 2016; 163:445-55. [PMID: 26451488 DOI: 10.1016/j.cell.2015.09.032] [Citation(s) in RCA: 180] [Impact Index Per Article: 22.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2015] [Revised: 08/14/2015] [Accepted: 09/11/2015] [Indexed: 01/07/2023]
Abstract
RNA-directed DNA methylation in Arabidopsis thaliana is driven by the plant-specific RNA Polymerase IV (Pol IV). It has been assumed that a Pol IV transcript can give rise to multiple 24-nt small interfering RNAs (siRNAs) that target DNA methylation. Here, we demonstrate that Pol IV-dependent RNAs (P4RNAs) from wild-type Arabidopsis are surprisingly short in length (30 to 40 nt) and mirror 24-nt siRNAs in distribution, abundance, strand bias, and 5'-adenine preference. P4RNAs exhibit transcription start sites similar to Pol II products and are featured with 5'-monophosphates and 3'-misincorporated nucleotides. The 3'-misincorporation preferentially occurs at methylated cytosines on the template DNA strand, suggesting a co-transcriptional feedback to siRNA biogenesis by DNA methylation to reinforce silencing locally. These results highlight an unusual mechanism of Pol IV transcription and suggest a "one precursor, one siRNA" model for the biogenesis of 24-nt siRNAs in Arabidopsis.
Collapse
|
22
|
Movahedi A, Sun W, Zhang J, Wu X, Mousavi M, Mohammadi K, Yin T, Zhuge Q. RNA-directed DNA methylation in plants. PLANT CELL REPORTS 2015; 34:1857-1862. [PMID: 26183954 DOI: 10.1007/s00299-015-1839-0] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/29/2015] [Accepted: 07/06/2015] [Indexed: 06/04/2023]
Abstract
In plants, many small interfering RNAs (siRNAs) direct de novo methylation by DNA methyltransferase. DNA methylation typically occurs by RNA-directed DNA methylation (RdDM), which directs transcriptional gene silencing of transposons and endogenous transgenes. RdDM is driven by non-coding RNAs (ncRNAs) produced by DNA-dependent RNA polymerases IV and V (PolIV and PolV). The production of siRNAs is initiated by PolIV and ncRNAs produced by PolIV are precursors of 24-nucleotide siRNAs. In contrast, ncRNAs produced by PolV are involved in scaffolding RNAs. In this review, we summarize recent studies of RdDM. In particular, we focus on the mechanisms involved in chromatin remodeling by PolIV and PolV.
Collapse
Affiliation(s)
- Ali Movahedi
- Co-Innovation Center for Sustainable Forestry in Southern China, Nanjing Forestry University, Nanjing, 210037, China
| | - Weibu Sun
- Co-Innovation Center for Sustainable Forestry in Southern China, Nanjing Forestry University, Nanjing, 210037, China
| | - Jiaxin Zhang
- Co-Innovation Center for Sustainable Forestry in Southern China, Nanjing Forestry University, Nanjing, 210037, China
| | - Xiaolong Wu
- Co-Innovation Center for Sustainable Forestry in Southern China, Nanjing Forestry University, Nanjing, 210037, China
| | - Mohaddesseh Mousavi
- Co-Innovation Center for Sustainable Forestry in Southern China, Nanjing Forestry University, Nanjing, 210037, China
| | - Kourosh Mohammadi
- Co-Innovation Center for Sustainable Forestry in Southern China, Nanjing Forestry University, Nanjing, 210037, China
| | - Tongming Yin
- Co-Innovation Center for Sustainable Forestry in Southern China, Nanjing Forestry University, Nanjing, 210037, China
| | - Qiang Zhuge
- Co-Innovation Center for Sustainable Forestry in Southern China, Nanjing Forestry University, Nanjing, 210037, China.
| |
Collapse
|
23
|
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.
Collapse
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
| |
Collapse
|
24
|
Duan CG, Zhang H, Tang K, Zhu X, Qian W, Hou YJ, Wang B, Lang Z, Zhao Y, Wang X, Wang P, Zhou J, Liang G, Liu N, Wang C, Zhu JK. Specific but interdependent functions for Arabidopsis AGO4 and AGO6 in RNA-directed DNA methylation. EMBO J 2014; 34:581-92. [PMID: 25527293 DOI: 10.15252/embj.201489453] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Argonaute (AGO) family proteins are conserved key components of small RNA-induced silencing pathways. In the RNA-directed DNA methylation (RdDM) pathway in Arabidopsis, AGO6 is generally considered to be redundant with AGO4. In this report, our comprehensive, genomewide analyses of AGO4- and AGO6-dependent DNA methylation revealed that redundancy is unexpectedly negligible in the genetic interactions between AGO4 and AGO6. Immunofluorescence revealed that AGO4 and AGO6 differ in their subnuclear co-localization with RNA polymerases required for RdDM. Pol II and AGO6 are absent from perinucleolar foci, where Pol V and AGO4 are co-localized. In the nucleoplasm, AGO4 displays a strong co-localization with Pol II, whereas AGO6 co-localizes with Pol V. These patterns suggest that RdDM is mediated by distinct, spatially regulated combinations of AGO proteins and RNA polymerases. Consistently, Pol II physically interacts with AGO4 but not AGO6, and the levels of Pol V-dependent scaffold RNAs and Pol V chromatin occupancy are strongly correlated with AGO6 but not AGO4. Our results suggest that AGO4 and AGO6 mainly act sequentially in mediating small RNA-directed DNA methylation.
Collapse
Affiliation(s)
- Cheng-Guo Duan
- Department of Horticulture and Landscape Architecture, Purdue University, West Lafayette, IN, USA
| | - Huiming Zhang
- Department of Horticulture and Landscape Architecture, Purdue University, West Lafayette, IN, USA
| | - Kai Tang
- Department of Horticulture and Landscape Architecture, Purdue University, West Lafayette, IN, USA
| | - Xiaohong Zhu
- Department of Horticulture and Landscape Architecture, Purdue University, West Lafayette, IN, USA
| | - Weiqiang Qian
- Shanghai Center for Plant Stress Biology, Shanghai Institute of Biological Sciences Chinese Academy of Sciences, Shanghai, China
| | - Yueh-Ju Hou
- Department of Horticulture and Landscape Architecture, Purdue University, West Lafayette, IN, USA
| | - Bangshing Wang
- Department of Horticulture and Landscape Architecture, Purdue University, West Lafayette, IN, USA
| | - Zhaobo Lang
- Department of Horticulture and Landscape Architecture, Purdue University, West Lafayette, IN, USA
| | - Yang Zhao
- Department of Horticulture and Landscape Architecture, Purdue University, West Lafayette, IN, USA Shanghai Center for Plant Stress Biology, Shanghai Institute of Biological Sciences Chinese Academy of Sciences, Shanghai, China
| | - Xingang Wang
- Department of Horticulture and Landscape Architecture, Purdue University, West Lafayette, IN, USA
| | - Pengcheng Wang
- Department of Horticulture and Landscape Architecture, Purdue University, West Lafayette, IN, USA
| | - Jianping Zhou
- School of Life Science and Technology University of Electronic Science and Technology of China, Chengdu Sichuan, China
| | - Gaimei Liang
- Dryland Agriculture Research Center, Shanxi Academy of Agricultural Sciences, Taiyuan Shanxi, China
| | - Na Liu
- Department of Horticulture, Laboratory of Genetics Resources & Functional Improvement for Horticultural Plant Zhejiang University, Hangzhou Zhejiang, China
| | - Chunguo Wang
- College of Life Sciences Nankai University, Tianjin, China
| | - Jian-Kang Zhu
- Department of Horticulture and Landscape Architecture, Purdue University, West Lafayette, IN, USA Shanghai Center for Plant Stress Biology, Shanghai Institute of Biological Sciences Chinese Academy of Sciences, Shanghai, China
| |
Collapse
|
25
|
Zhang H, Zhu JK. Emerging roles of RNA processing factors in regulating long non-coding RNAs. RNA Biol 2014; 11:793-7. [PMID: 25144332 DOI: 10.4161/rna.29731] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Long non-coding RNAs (lncRNAs) can be important regulators of various biological processes such as RNA-directed DNA methylation (RdDM). In the RdDM pathway, recruitment of the DNA methylation complex is mediated through complementary pairing between scaffold RNAs and Argonaute-associated siRNAs. Scaffold RNAs are chromatin-associated lncRNAs transcribed by RNA polymerase Pol V or Pol II, while siRNAs originate from Pol IV- or Pol II-dependent production of lncRNAs. In contrast to the vast literature on co-transcriptional and post-transcriptional processing of mRNAs, information is limited for lncRNA regulation that enables their production and function. Recently Arabidopsis RRP6L1, a plant paralog of the conserved nuclear RNA surveillance protein Rrp6, was shown to mediate RdDM through retention of lncRNAs in the chromatin, thereby revealing that accumulation of functional lncRNAs requires more than simply RNA polymerases. By focusing on the canonical RdDM pathway, here we summarize recent evidence that indicate co-transcriptional and/or post-transcriptional regulation of lncRNAs, and highlight the emerging theme of lncRNA regulation by RNA processing factors.
Collapse
Affiliation(s)
- Huiming Zhang
- Department of Horticulture and Landscape Architecture; Purdue University; West Lafayette, IN USA
| | - Jian-Kang Zhu
- Department of Horticulture and Landscape Architecture; Purdue University; West Lafayette, IN USA; Shanghai Center for Plant Stress Biology; Shanghai Institute of Biological Sciences; Chinese Academy of Sciences; Beijing, PR China
| |
Collapse
|
26
|
Li CH, Chiang CP, Yang JY, Ma CJ, Chen YC, Yen HE. RING-type ubiquitin ligase McCPN1 catalyzes UBC8-dependent protein ubiquitination and interacts with Argonaute 4 in halophyte ice plant. PLANT PHYSIOLOGY AND BIOCHEMISTRY : PPB 2014; 80:211-9. [PMID: 24811676 DOI: 10.1016/j.plaphy.2014.04.006] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/16/2014] [Accepted: 04/09/2014] [Indexed: 05/08/2023]
Abstract
RING-type copines are a small family of plant-specific RING-type ubiquitin ligases. They contain an N-terminal myristoylation site for membrane anchoring, a central copine domain for substrate recognition, and a C-terminal RING domain for E2 docking. RING-type copine McCPN1 (copine1) from halophyte ice plant (Mesembryanthemum crystallinum L.) was previously identified from a salt-induced cDNA library. In this work, we characterize the activity, expression, and localization of McCPN1 in ice plant. An in vitro ubiquitination assay of McCPN1 was performed using two ice plant UBCs, McUBC1 and McUBC2, characterized from the same salt-induced cDNA library. The results showed that McUBC2, a member of the UBC8 family, stimulated the autoubiquitination activity of McCPN1, while McUBC1, a homolog of the UBC35 family, did not. The results indicate that McCPN1 has selective E2-dependent E3 ligase activity. We found that McCPN1 localizes primarily on the plasma membrane and in the nucleus of plant cells. Under salt stress, the accumulation of McCPN1 in the roots increases. A yeast two-hybrid screen was used to search for potential McCPN1-interacting partners using a library constructed from salt-stressed ice plants. Screening with full-length McCPN1 identified several independent clones containing partial Argonaute 4 (AGO4) sequence. Subsequent agro-infiltration, protoplast two-hybrid analysis, and bimolecular fluorescence complementation assay confirmed that McCPN1 and AGO4 interacted in vivo in the nucleus of plant cells. The possible involvement of a catalyzed degradation of AGO4 by McCPN1 in response to salt stress is discussed.
Collapse
Affiliation(s)
- Chang-Hua Li
- Department of Life Sciences, National Chung Hsing University, Taichung 40227, Taiwan.
| | - Chih-Pin Chiang
- Department of Life Sciences, National Chung Hsing University, Taichung 40227, Taiwan.
| | - Jun-Yi Yang
- Institute of Biochemistry, National Chung Hsing University, Taichung 40227, Taiwan.
| | - Chia-Jou Ma
- Department of Life Sciences, National Chung Hsing University, Taichung 40227, Taiwan.
| | - Yu-Chan Chen
- Department of Life Sciences, National Chung Hsing University, Taichung 40227, Taiwan.
| | - Hungchen Emilie Yen
- Department of Life Sciences, National Chung Hsing University, Taichung 40227, Taiwan.
| |
Collapse
|
27
|
Connecting the dots of RNA-directed DNA methylation in Arabidopsis thaliana. Chromosome Res 2014; 22:225-40. [PMID: 24846724 DOI: 10.1007/s10577-014-9425-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
Noncoding RNAs are the rising stars of genome regulation and are crucial to an organism's metabolism, development, and defense. One of their most notable functions is its ability to direct epigenetic modifications through small RNA molecules to specific genomic regions, ensuring transcriptional regulation, proper genome organization, and maintenance of genome integrity. Here, we review the current knowledge of the spatial organization of the Arabidopsis thaliana RNA-directed DNA methylation pathway within the cell nucleus, which, while known to be essential for the proper establishment of epigenetic modifications, remains poorly understood. We will also discuss possible future cytological approaches that have the potential of unveiling functional insights into how small RNA-directed epigenetics is regulated through the spatiotemporal regulation of its major components within the cell.
Collapse
|
28
|
Huang CF, Zhu JK. RNA Splicing Factors and RNA-Directed DNA Methylation. BIOLOGY 2014; 3:243-54. [PMID: 24833507 PMCID: PMC4085605 DOI: 10.3390/biology3020243] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/17/2014] [Revised: 03/18/2014] [Accepted: 03/20/2014] [Indexed: 11/16/2022]
Abstract
RNA-directed histone and/or DNA modification is a conserved mechanism for the establishment of epigenetic marks from yeasts and plants to mammals. The heterochromation formation in yeast is mediated by RNAi-directed silencing mechanism, while the establishment of DNA methylation in plants is through the RNA-directed DNA methylation (RdDM) pathway. Recently, splicing factors are reported to be involved in both RNAi-directed heterochromatin formation in yeast and the RdDM pathway in plants. In yeast, splicing factors may provide a platform for facilitating the siRNA generation through an interaction with RDRC and thereby affect the heterochromatin formation, whereas in plants, various splicing factors seem to act at different steps in the RdDM pathway.
Collapse
Affiliation(s)
- Chao-Feng Huang
- State Key Laboratory of Crop Genetics and Germplasm Enhancement, College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing 210095, China.
| | - Jian-Kang Zhu
- Shanghai Center for Plant Stress Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China.
| |
Collapse
|
29
|
Raja P, Jackel JN, Li S, Heard IM, Bisaro DM. Arabidopsis double-stranded RNA binding protein DRB3 participates in methylation-mediated defense against geminiviruses. J Virol 2014. [PMID: 24352449 DOI: 10.1128/jvi.02305-2313] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/30/2023] Open
Abstract
UNLABELLED Arabidopsis encodes five double-stranded RNA binding (DRB) proteins. DRB1 and DRB2 are involved in microRNA (miRNA) biogenesis, while DRB4 functions in cytoplasmic posttranscriptional small interfering RNA (siRNA) pathways. DRB3 and DRB5 are not involved in double-stranded RNA (dsRNA) processing but assist in silencing transcripts targeted by DRB2-associated miRNAs. The goal of this study was to determine which, if any, of the DRB proteins might also participate in a nuclear siRNA pathway that leads to geminivirus genome methylation. Here, we demonstrate that DRB3 functions with Dicer-like 3 (DCL3) and Argonaute 4 (AGO4) in methylation-mediated antiviral defense. Plants employ repressive viral genome methylation as an epigenetic defense against geminiviruses, using an RNA-directed DNA methylation (RdDM) pathway similar to that used to suppress endogenous invasive DNAs such as transposons. Chromatin methylation inhibits virus replication and transcription, and methylation-deficient host plants are hypersusceptible to geminivirus infection. Using a panel of drb mutants, we found that drb3 plants uniquely exhibit a similar hypersensitivity and that viral genome methylation is substantially reduced in drb3 compared to wild-type plants. In addition, like dcl3 and ago4 mutants, drb3 plants fail to recover from infection and cannot accomplish the viral genome hypermethylation that is invariably observed in asymptomatic, recovered tissues. Small RNA analysis, bimolecular fluorescence complementation, and coimmunoprecipitation experiments show that DRB3 acts downstream of siRNA biogenesis and suggest that it associates with DCL3 and AGO4 in distinct subnuclear compartments. These studies reveal that in addition to its previously established role in the miRNA pathway, DRB3 also functions in antiviral RdDM. IMPORTANCE Plants use RNA-directed DNA methylation (RdDM) as an epigenetic defense against geminiviruses. RNA silencing pathways in Arabidopsis include five double-stranded RNA binding proteins (DRBs) related to Drosophila R2D2 and mammalian TRBP and PACT. While DRB proteins have defined roles in miRNA and cytoplasmic siRNA pathways, a role in nuclear RdDM was elusive. Here, we used the geminivirus system to show that DRB3 is involved in methylation-mediated antiviral defense. Beginning with a panel of Arabidopsis drb mutants, we demonstrated that drb3 plants uniquely show enhanced susceptibility to geminiviruses. Further, like dcl3 and ago4 mutants, drb3 plants fail to hypermethylate the viral genome, a requirement for host recovery. We also show that DRB3 physically interacts with the RdDM pathway components DCL3 and AGO4 in the nucleus. This work highlights the utility of geminiviruses as models for de novo RdDM and places DRB3 protein in this fundamental epigenetic pathway.
Collapse
Affiliation(s)
- Priya Raja
- Department of Molecular Genetics, Center for Applied Plant Sciences, and Center for RNA Biology, The Ohio State University, Columbus, Ohio, USA
| | | | | | | | | |
Collapse
|
30
|
Guo T, Fang Y. Functional organization and dynamics of the cell nucleus. FRONTIERS IN PLANT SCIENCE 2014; 5:378. [PMID: 25161658 PMCID: PMC4130368 DOI: 10.3389/fpls.2014.00378] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/16/2014] [Accepted: 07/16/2014] [Indexed: 05/16/2023]
Abstract
The eukaryotic cell nucleus enclosed within the nuclear envelope harbors organized chromatin territories and various nuclear bodies as sub-nuclear compartments. This higher-order nuclear organization provides a unique environment to regulate the genome during replication, transcription, maintenance, and other processes. In this review, we focus on the plant four-dimensional nuclear organization, its dynamics and function in response to signals during development or stress.
Collapse
Affiliation(s)
| | - Yuda Fang
- *Correspondence: Yuda Fang, National key Laboratory of Plant Molecular Genetics, Shanghai Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, 300 Fenglin Road, Shanghai 200032, China e-mail:
| |
Collapse
|
31
|
Arabidopsis double-stranded RNA binding protein DRB3 participates in methylation-mediated defense against geminiviruses. J Virol 2013; 88:2611-22. [PMID: 24352449 DOI: 10.1128/jvi.02305-13] [Citation(s) in RCA: 91] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
UNLABELLED Arabidopsis encodes five double-stranded RNA binding (DRB) proteins. DRB1 and DRB2 are involved in microRNA (miRNA) biogenesis, while DRB4 functions in cytoplasmic posttranscriptional small interfering RNA (siRNA) pathways. DRB3 and DRB5 are not involved in double-stranded RNA (dsRNA) processing but assist in silencing transcripts targeted by DRB2-associated miRNAs. The goal of this study was to determine which, if any, of the DRB proteins might also participate in a nuclear siRNA pathway that leads to geminivirus genome methylation. Here, we demonstrate that DRB3 functions with Dicer-like 3 (DCL3) and Argonaute 4 (AGO4) in methylation-mediated antiviral defense. Plants employ repressive viral genome methylation as an epigenetic defense against geminiviruses, using an RNA-directed DNA methylation (RdDM) pathway similar to that used to suppress endogenous invasive DNAs such as transposons. Chromatin methylation inhibits virus replication and transcription, and methylation-deficient host plants are hypersusceptible to geminivirus infection. Using a panel of drb mutants, we found that drb3 plants uniquely exhibit a similar hypersensitivity and that viral genome methylation is substantially reduced in drb3 compared to wild-type plants. In addition, like dcl3 and ago4 mutants, drb3 plants fail to recover from infection and cannot accomplish the viral genome hypermethylation that is invariably observed in asymptomatic, recovered tissues. Small RNA analysis, bimolecular fluorescence complementation, and coimmunoprecipitation experiments show that DRB3 acts downstream of siRNA biogenesis and suggest that it associates with DCL3 and AGO4 in distinct subnuclear compartments. These studies reveal that in addition to its previously established role in the miRNA pathway, DRB3 also functions in antiviral RdDM. IMPORTANCE Plants use RNA-directed DNA methylation (RdDM) as an epigenetic defense against geminiviruses. RNA silencing pathways in Arabidopsis include five double-stranded RNA binding proteins (DRBs) related to Drosophila R2D2 and mammalian TRBP and PACT. While DRB proteins have defined roles in miRNA and cytoplasmic siRNA pathways, a role in nuclear RdDM was elusive. Here, we used the geminivirus system to show that DRB3 is involved in methylation-mediated antiviral defense. Beginning with a panel of Arabidopsis drb mutants, we demonstrated that drb3 plants uniquely show enhanced susceptibility to geminiviruses. Further, like dcl3 and ago4 mutants, drb3 plants fail to hypermethylate the viral genome, a requirement for host recovery. We also show that DRB3 physically interacts with the RdDM pathway components DCL3 and AGO4 in the nucleus. This work highlights the utility of geminiviruses as models for de novo RdDM and places DRB3 protein in this fundamental epigenetic pathway.
Collapse
|
32
|
Xian Z, Yang Y, Huang W, Tang N, Wang X, Li Z. Molecular cloning and characterisation of SlAGO family in tomato. BMC PLANT BIOLOGY 2013; 13:126. [PMID: 24011258 PMCID: PMC3847217 DOI: 10.1186/1471-2229-13-126] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/16/2013] [Accepted: 08/30/2013] [Indexed: 05/27/2023]
Abstract
BACKGROUND AGO (Argonaute) protein participates in plant developmental processes and virus defense as a core element of transcriptional regulator or/and post-transcriptional regulator in RNA induced silencing complex (RISC), which is guided by small RNAs to repress target genes expression. Previously, it was revealed that 15 putative AGO genes in tomato genome. RESULTS In present study, out of 15 detected SlAGO genes, only SlAGO4C and SlAGO15 couldn't be detected in roots, stems, leaves, buds, flowers and fruit of tomato by 30 cycles of PCR. SlAGO7 could be detected in early stage of fruit (-2 dpa, 0 dpa and 4 dpa), but it was significantly down-regulated in fruit collected on the 6 days post anthesis. Moreover, SlAGO5 could only be detected in reproductive tissues and SlAGO4D was specifically detected in fruit. According to blast result with miRNA database, three SlAGO genes harbored complementary sequences to miR168 (SlAGO1A and SlAGO1B) or miR403 (SlAGO2A). 5' RACE (Rapid amplification of cDNA ends) mapping was used to detect the 3' cleavage products of SlAGO mRNAs. In addition, subcellular localization of SlAGO proteins was detected. Our results showed that most SlAGO proteins localized to nucleus and cytoplasm. Importantly, nuclear membrane localization of AGO proteins was observed. Furthermore, mutated miR168 complementary site of SlAGO1A resulted in expanded localization of SlAGO1A, indicating that miR168 regulated localization of SlAGO1A. CONCLUSIONS Our results contribute to demonstration of potential roles of these newly isolated AGO family in tomato developmental processes and proved the conserved relationships between AGO genes and miRNAs in tomato, which might play important roles in tomato development and virus defense.
Collapse
Affiliation(s)
- Zhiqiang Xian
- Genetic Engineering Research Center, School of Life Sciences, Chongqing University, Chongqing 400044, People’s Republic of China
| | - Yingwu Yang
- Genetic Engineering Research Center, School of Life Sciences, Chongqing University, Chongqing 400044, People’s Republic of China
| | - Wei Huang
- Genetic Engineering Research Center, School of Life Sciences, Chongqing University, Chongqing 400044, People’s Republic of China
| | - Ning Tang
- Genetic Engineering Research Center, School of Life Sciences, Chongqing University, Chongqing 400044, People’s Republic of China
| | - Xinyu Wang
- Genetic Engineering Research Center, School of Life Sciences, Chongqing University, Chongqing 400044, People’s Republic of China
| | - Zhengguo Li
- Genetic Engineering Research Center, School of Life Sciences, Chongqing University, Chongqing 400044, People’s Republic of China
| |
Collapse
|
33
|
Brabbs TR, He Z, Hogg K, Kamenski A, Li Y, Paszkiewicz KH, Moore KA, O'Toole P, Graham IA, Jones L. The stochastic silencing phenotype of Arabidopsis morc6 mutants reveals a role in efficient RNA-directed DNA methylation. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2013; 75:836-46. [PMID: 23675613 DOI: 10.1111/tpj.12246] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/27/2013] [Accepted: 05/09/2013] [Indexed: 05/18/2023]
Abstract
The RNA-directed DNA methylation (RdDM) pathway is of central importance to the initiation and maintenance of transcriptional gene silencing in plants. DNA methylation is directed to target sequences by a mechanism that involves production of small RNAs by RNA polymerase IV and long non-coding RNAs by RNA polymerase V. DNA methylation then leads to recruitment of histone-modifying enzymes, followed by establishment of a silenced chromatin state. Recently MORC6, a member of the microrchidia (MORC) family of adenosine triphosphatases (ATPases), has been shown to be involved in transcriptional gene silencing. However, reports differ regarding whether MORC6 is involved in RdDM itself or acts downstream of DNA methylation to enable formation of higher-order chromatin structure. Here we demonstrate that MORC6 is required for efficient RdDM at some target loci, and, using a GFP reporter system, we found that morc6 mutants show a stochastic silencing phenotype. By using cell sorting to separate silenced and unsilenced cells, we show that release of silencing at this locus is associated with a loss of DNA methylation. Thus our data support a view that MORC6 influences RdDM and that it is not acting downstream of DNA methylation. For some loci, efficient initiation or maintenance of DNA methylation may depend on the ability to form higher-order chromatin structure.
Collapse
Affiliation(s)
- Thomas R Brabbs
- Department of Biology, University of York, YO10 5DD, York, UK
| | | | | | | | | | | | | | | | | | | |
Collapse
|
34
|
De Novo Methyltransferase, OsDRM2, Interacts with the ATP-Dependent RNA Helicase, OseIF4A, in Rice. J Mol Biol 2013; 425:2853-66. [DOI: 10.1016/j.jmb.2013.05.021] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2013] [Revised: 05/17/2013] [Accepted: 05/28/2013] [Indexed: 12/12/2022]
|
35
|
Dou K, Huang CF, Ma ZY, Zhang CJ, Zhou JX, Huang HW, Cai T, Tang K, Zhu JK, He XJ. The PRP6-like splicing factor STA1 is involved in RNA-directed DNA methylation by facilitating the production of Pol V-dependent scaffold RNAs. Nucleic Acids Res 2013; 41:8489-502. [PMID: 23877244 PMCID: PMC3794598 DOI: 10.1093/nar/gkt639] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
DNA methylation is a conserved epigenetic marker in plants and animals. In Arabidopsis, DNA methylation can be established through an RNA-directed DNA methylation (RdDM) pathway. By screening for suppressors of ros1, we identified STA1, a PRP6-like splicing factor, as a new RdDM regulator. Whole-genome bisulfite sequencing suggested that STA1 and the RdDM pathway share a large number of common targets in the Arabidopsis genome. Small RNA deep sequencing demonstrated that STA1 is predominantly involved in the accumulation of the siRNAs that depend on both Pol IV and Pol V. Moreover, the sta1 mutation partially reduces the levels of Pol V-dependent RNA transcripts. Immunolocalization assay indicated that STA1 signals are exclusively present in the Cajal body and overlap with AGO4 in most nuclei. STA1 signals are also partially overlap with NRPE1. Localization of STA1 to AGO4 and NRPE1 signals is probably related to the function of STA1 in the RdDM pathway. Based on these results, we propose that STA1 acts downstream of siRNA biogenesis and facilitates the production of Pol V-dependent RNA transcripts in the RdDM pathway.
Collapse
Affiliation(s)
- Kun Dou
- National Institute of Biological Sciences, Beijing 102206, China, College of Life Science, Beijing Normal University, Beijing 100875, China, Shanghai Center for Plant Stress Biology and Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China and Department of Horticulture and Landscape Architecture, Purdue University, West Lafayette, IN 47907, USA
| | | | | | | | | | | | | | | | | | | |
Collapse
|
36
|
Pontes O, Vitins A, Ream TS, Hong E, Pikaard CS, Costa-Nunes P. Intersection of small RNA pathways in Arabidopsis thaliana sub-nuclear domains. PLoS One 2013; 8:e65652. [PMID: 23776518 PMCID: PMC3680462 DOI: 10.1371/journal.pone.0065652] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2012] [Accepted: 04/25/2013] [Indexed: 12/22/2022] Open
Abstract
In Arabidopsis thaliana, functionally diverse small RNA (smRNA) pathways bring about decreased RNA accumulation of target genes via several different mechanisms. Cytological experiments have suggested that the processing of microRNAs (miRNAs) and heterochromatic small interfering RNAs (hc-siRNAs) occurs within a specific nuclear domain that can present Cajal Body (CB) characteristics. It is unclear whether single or multiple smRNA-related domains are found within the same CB and how specialization of the smRNA pathways is determined within this specific sub-compartment. To ascertain whether nuclear smRNA centers are spatially related, we localized key proteins required for siRNA or miRNA biogenesis by immunofluorescence analysis. The intranuclear distribution of the proteins revealed that hc-siRNA, miRNA and trans-acting siRNA (ta-siRNA) pathway proteins accumulate and colocalize within a sub-nuclear structure in the nucleolar periphery. Furthermore, colocalization of miRNA- and siRNA-pathway members with CB markers, and reduced wild-type localization patterns in CB mutants indicates that proper nuclear localization of these proteins requires CB integrity. We hypothesize that these nuclear domains could be important for RNA silencing and may partially explain the functional redundancies and interactions among components of the same protein family. The CB may be the place in the nucleus where Dicer-generated smRNA precursors are processed and assigned to a specific pathway, and where storage, recycling or assembly of RNA interference components takes place.
Collapse
Affiliation(s)
- Olga Pontes
- Department of Biology, University of New Mexico, Albuquerque, New Mexico, United States of America.
| | | | | | | | | | | |
Collapse
|
37
|
Woolcock KJ, Bühler M. Nuclear organisation and RNAi in fission yeast. Curr Opin Cell Biol 2013; 25:372-7. [DOI: 10.1016/j.ceb.2013.02.004] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2012] [Accepted: 02/05/2013] [Indexed: 12/20/2022]
|
38
|
The splicing machinery promotes RNA-directed DNA methylation and transcriptional silencing in Arabidopsis. EMBO J 2013; 32:1128-40. [PMID: 23524848 DOI: 10.1038/emboj.2013.49] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2012] [Accepted: 02/07/2013] [Indexed: 12/15/2022] Open
Abstract
DNA methylation in transposons and other DNA repeats is conserved in plants as well as in animals. In Arabidopsis thaliana, an RNA-directed DNA methylation (RdDM) pathway directs de novo DNA methylation. We performed a forward genetic screen for suppressors of the DNA demethylase mutant ros1 and identified a novel Zinc-finger and OCRE domain-containing Protein 1 (ZOP1) that promotes Pol IV-dependent siRNA accumulation, DNA methylation, and transcriptional silencing. Whole-genome methods disclosed the genome-wide effects of zop1 on Pol IV-dependent siRNA accumulation and DNA methylation, suggesting that ZOP1 has both RdDM-dependent and -independent roles in transcriptional silencing. We demonstrated that ZOP1 is a pre-mRNA splicing factor that associates with several typical components of the splicing machinery as well as with Pol II. Immunofluorescence assay revealed that ZOP1 overlaps with Cajal body and is partially colocalized with NRPE1 and DRM2. Moreover, we found that the other development-defective splicing mutants tested including mac3a3b, mos4, mos12 and mos14 show defects in RdDM and transcriptional silencing. We propose that the splicing machinery rather than specific splicing factors is involved in promoting RdDM and transcriptional silencing.
Collapse
|
39
|
Zhang H, Zhu JK. Seeing the forest for the trees: a wide perspective on RNA-directed DNA methylation. Genes Dev 2012; 26:1769-73. [PMID: 22895250 DOI: 10.1101/gad.200410.112] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
In this issue of Genes & Development, Wierzbicki and colleagues (pp. 1825-1836) examine the current model of RNA-directed DNA methylation (RdDM) by determining genome-wide distributions of RNA polymerase V (Pol V) occupancy, siRNAs, and DNA methylation. Their data support the key role of base-pairing between Pol V transcripts and siRNAs in targeting de novo DNA methylation. Importantly, the study also reveals unexpected complexity and provides a global view of the RdDM pathway.
Collapse
Affiliation(s)
- Huiming Zhang
- Department of Horticulture and Landscape Architecture, Purdue University, West Lafayette, Indiana 47907, USA
| | | |
Collapse
|
40
|
Stunnenberg R, Bühler M. A detour to mature. Mol Cell 2012; 46:719-21. [PMID: 22749397 DOI: 10.1016/j.molcel.2012.06.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
In this issue of Molecular Cell, Ye et al. (2012) show an unexpected cytoplasmic assembly of Arabidopsis ARGONAUTE4/siRNA complexes and that siRNA binding could facilitate the nuclear import of mature AGO4/siRNA complexes, revealing a key regulatory process during RNA-directed DNA methylation (RdDM).
Collapse
Affiliation(s)
- Rieka Stunnenberg
- Friedrich Miescher Institute for Biomedical Research, Maulbeerstrasse 66, 4058 Basel, Switzerland
| | | |
Collapse
|
41
|
Abstract
Given the widespread impact of RNA silencing on the Arabidopsis thaliana genome, it is indeed remarkable that this means of gene regulation went undiscovered for so long. Since the publication of landmark papers in 1998 (Fire et al., Nature 391:806-811, 1998; Waterhouse et al., Proc Natl Acad Sci U S A 95:13959-13964, 1998), intense research efforts have resulted in much progress from the speculation of Mello and colleagues that "the mechanisms underlying RNA interference probably exist for a biological purpose" (Fire et al., Nature 391:806-811, 1998). Across the eukaryotic kingdom, with the notable exception of Saccharomyces cerevisiae (Moazed, Science 326:544-550, 2009), the importance of small RNA-driven gene regulation has been recognized and implicated in central developmental processes as well as in aberrant and diseased states. Plants have by far the most complex RNA-based control of gene expression (Wang et al., Floriculture, ornamental and plant biotechnology, vol. III, 2006). Four distinct RNA silencing pathways have been recognized in plants, albeit with considerable conservation of the molecular components. These pathways are directed by various small RNA species, including microRNAs (miRNAs), trans-acting small interfering RNAs (siRNA) (ta-siRNAs), repeat-associated siRNAs (ra-siRNAs), and natural antisense transcript siRNAs (nat-siRNAs). The effective functionality of each of these pathways appear to be fundamental to the integrity of A. thaliana. Furthermore, in response to viral invasion, plants synthesize viral sRNAs as a means of defense. This process may in fact reflect the ancient origins of RNA silencing: plants may have evolved RNA silencing pathways as a defense mechanism against foreign nucleic acid species in the absence of an immune system (Wang and Metzlaff, Curr Opin Plant Biol 8:216-222, 2005). The generation of viral siRNAs is a particularly interesting illustration of RNA silencing as it provides a context to explore the potential to harness a naturally occurring system to the end goal of artificially engineering viral resistance.
Collapse
|
42
|
Azevedo J, Cooke R, Lagrange T. Taking RISCs with Ago hookers. CURRENT OPINION IN PLANT BIOLOGY 2011; 14:594-600. [PMID: 21807551 DOI: 10.1016/j.pbi.2011.07.002] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/09/2011] [Revised: 07/08/2011] [Accepted: 07/08/2011] [Indexed: 05/31/2023]
Abstract
Argonautes are central and common components of crucial effectors of RNA silencing pathways. Although earlier steps in these pathways, such as small RNA biogenesis and their loading into AGO, have been quite well described, our knowledge on regulation of the action of AGO and their partners is still poor. Recent breakthroughs have highlighted the existence in many eukaryotes of an evolutionarily conserved motif, the Ago-hook, in factors implicated in AGO action. Furthermore, it has been shown that certain plant pathogen proteins have co-opted the Ago-hook as a means of evasion of plant defense systems. Here we discuss the roles and properties of Ago-hook proteins in divergent RNAi-related pathways.
Collapse
Affiliation(s)
- Jacinthe Azevedo
- Laboratoire Génome et Développement des Plantes, Centre National de la Recherche Scientifique/Université de Perpignan, Perpignan, France
| | | | | |
Collapse
|
43
|
Law JA, Jacobsen SE. Establishing, maintaining and modifying DNA methylation patterns in plants and animals. Nat Rev Genet 2011; 11:204-20. [PMID: 20142834 DOI: 10.1038/nrg2719] [Citation(s) in RCA: 2489] [Impact Index Per Article: 191.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Cytosine DNA methylation is a stable epigenetic mark that is crucial for diverse biological processes, including gene and transposon silencing, imprinting and X chromosome inactivation. Recent findings in plants and animals have greatly increased our understanding of the pathways used to accurately target, maintain and modify patterns of DNA methylation and have revealed unanticipated mechanistic similarities between these organisms. Key roles have emerged for small RNAs, proteins with domains that bind methylated DNA and DNA glycosylases in these processes. Drawing on insights from both plants and animals should deepen our understanding of the regulation and biological significance of DNA methylation.
Collapse
Affiliation(s)
- Julie A Law
- Department of Molecular, Cell and Developmental Biology, University of California-Los Angeles, 90095-1606, USA
| | | |
Collapse
|
44
|
Zhang H, Zhu JK. RNA-directed DNA methylation. CURRENT OPINION IN PLANT BIOLOGY 2011; 14:142-7. [PMID: 21420348 PMCID: PMC3096526 DOI: 10.1016/j.pbi.2011.02.003] [Citation(s) in RCA: 174] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/12/2010] [Revised: 01/11/2011] [Accepted: 02/21/2011] [Indexed: 05/19/2023]
Abstract
DNA methylation is an important epigenetic mechanism for silencing transposons and other repetitive elements, and for stable repression of specific transgenes and endogenous genes. Plants can utilize small interfering RNAs (siRNAs) to guide de novo DNA methyltransferases for the establishment of sequence-specific DNA methylation. Genetic and biochemical approaches have identified many components involved in RNA-directed DNA methylation (RdDM). These components function in one or more of the following three aspects: biogenesis of siRNAs, production of scaffold RNAs, and the assembly of an effector complex that involves the complementary pairing between the guide siRNAs and nascent scaffold RNAs and that recruits the DNA methyltransferases. Recent studies not only unveiled new molecular players and novel interactions, but also suggested spatial and temporal segregation of the RdDM process within the nucleus.
Collapse
Affiliation(s)
- Huiming Zhang
- Department of Botany and Plant Sciences, Institute for Integrative Genome Biology, University of California, Riverside, CA 92521, USA
| | - Jian-Kang Zhu
- Department of Botany and Plant Sciences, Institute for Integrative Genome Biology, University of California, Riverside, CA 92521, USA
- corresponding author: Zhu, Jian-Kang ()
| |
Collapse
|
45
|
Pantaleo V. Plant RNA silencing in viral defence. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2011; 722:39-58. [PMID: 21915781 DOI: 10.1007/978-1-4614-0332-6_3] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
RNA silencing is described in plants and insects as a defence mechanism against foreign nucleic acids, such as invading viruses. The RNA silencing-based antiviral defence involves the production of virus-derived small interfering RNAs and their association to effector proteins, which together drive the sequence specific inactivation of viruses. The entire process of antiviral defence 'borrows' several plant factors involved in other specialized RNA silencing endogenous pathways. Different viruses use variable strategies to infect different host plants, which render the antiviral RNA silencing a complex phenomenon far to be completely clarified. This chapter reports current advances in understanding the main steps of the plant's RNA-silencing response to viral invasion and discusses some of the key questions still to be answered.
Collapse
|
46
|
The de novo cytosine methyltransferase DRM2 requires intact UBA domains and a catalytically mutated paralog DRM3 during RNA-directed DNA methylation in Arabidopsis thaliana. PLoS Genet 2010; 6:e1001182. [PMID: 21060858 PMCID: PMC2965745 DOI: 10.1371/journal.pgen.1001182] [Citation(s) in RCA: 80] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2010] [Accepted: 09/28/2010] [Indexed: 11/19/2022] Open
Abstract
Eukaryotic DNA cytosine methylation can be used to transcriptionally silence repetitive sequences, including transposons and retroviruses. This silencing is stable between cell generations as cytosine methylation is maintained epigenetically through DNA replication. The Arabidopsis thaliana Dnmt3 cytosine methyltransferase ortholog DOMAINS rearranged methyltransferase2 (DRM2) is required for establishment of small interfering RNA (siRNA) directed DNA methylation. In mammals PIWI proteins and piRNA act in a convergently evolved RNA-directed DNA methylation system that is required to repress transposon expression in the germ line. De novo methylation may also be independent of RNA interference and small RNAs, as in Neurospora crassa. Here we identify a clade of catalytically mutated DRM2 paralogs in flowering plant genomes, which in A.thaliana we term domains rearranged methyltransferase3 (DRM3). Despite being catalytically mutated, DRM3 is required for normal maintenance of non-CG DNA methylation, establishment of RNA-directed DNA methylation triggered by repeat sequences and accumulation of repeat-associated small RNAs. Although the mammalian catalytically inactive Dnmt3L paralogs act in an analogous manner, phylogenetic analysis indicates that the DRM and Dnmt3 protein families diverged independently in plants and animals. We also show by site-directed mutagenesis that both the DRM2 N-terminal UBA domains and C-terminal methyltransferase domain are required for normal RNA-directed DNA methylation, supporting an essential targeting function for the UBA domains. These results suggest that plant and mammalian RNA-directed DNA methylation systems consist of a combination of ancestral and convergent features.
Collapse
|
47
|
|
48
|
An RNA polymerase II- and AGO4-associated protein acts in RNA-directed DNA methylation. Nature 2010; 465:106-9. [PMID: 20410883 PMCID: PMC2865564 DOI: 10.1038/nature09025] [Citation(s) in RCA: 181] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2009] [Accepted: 03/22/2010] [Indexed: 01/06/2023]
Abstract
DNA methylation is an important epigenetic mark in many eukaryotes1-5. In plants, 24-nt small interfering RNAs (siRNAs) bound to the effector protein, Argonaute 4 (AGO4) can direct de novo DNA methylation by the methyltransferase DRM22,4-6. Here we report a new regulator of RNA-directed DNA methylation (RdDM) in Arabidopsis: RDM1. Loss-of-function mutations in the RDM1 gene impair the accumulation of 24-nt siRNAs, reduce DNA methylation, and release transcriptional gene silencing at RdDM target loci. RDM1 encodes a small protein that appears to bind single-stranded methyl DNA, and associates and co-localizes with RNA polymerase II, AGO4 and DRM2 in the nucleus. Our results suggest that RDM1 is a component of the RdDM effector complex and may play a role in linking siRNA production with pre-existing or de novo cytosine methylation. Our results also suggest that although RDM1 and Pol V may function together at some RdDM target sites in the peri-nucleolar siRNA processing center, Pol II rather than Pol V is associated with the RdDM effector complex at target sites in the nucleoplasm.
Collapse
|
49
|
Emmerth S, Schober H, Gaidatzis D, Roloff T, Jacobeit K, Bühler M. Nuclear retention of fission yeast dicer is a prerequisite for RNAi-mediated heterochromatin assembly. Dev Cell 2010; 18:102-13. [PMID: 20152181 DOI: 10.1016/j.devcel.2009.11.011] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2009] [Revised: 10/24/2009] [Accepted: 11/25/2009] [Indexed: 12/20/2022]
Abstract
RNaseIII ribonucleases act at the heart of RNA silencing pathways by processing precursor RNAs into mature microRNAs and siRNAs. In the fission yeast Schizosaccharomyces pombe, siRNAs are generated by the RNaseIII enzyme Dcr1 and are required for heterochromatin formation at centromeres. In this study, we have analyzed the subcellular localization of Dcr1 and found that it accumulates in the nucleus and is enriched at the nuclear periphery. Nuclear accumulation of Dcr1 depends on a short motif that impedes nuclear export promoted by the double-stranded RNA binding domain of Dcr1. Absence of this motif renders Dcr1 mainly cytoplasmic and is accompanied by remarkable changes in gene expression and failure to assemble heterochromatin. Our findings suggest that Dicer proteins are shuttling proteins and that the steady-state subcellular levels can be shifted toward either compartment.
Collapse
Affiliation(s)
- Stephan Emmerth
- Friedrich Miescher Institute for Biomedical Research, Maulbeerstrasse 66, CH-4058 Basel, Switzerland
| | | | | | | | | | | |
Collapse
|
50
|
Abstract
Plant defense responses against pathogens are mediated by activation and repression of a large array of genes. Host endogenous small RNAs are essential in this gene expression reprogramming process. Here, we discuss recent findings on pathogen-regulated host microRNAs (miRNAs) and small interfering RNAs (siRNAs) and their roles in plant-microbe interaction. We further introduce small RNA pathway components, including Dicer-like proteins (DCLs), double-stranded RNA (dsRNA) binding protein, RNA-dependent RNA polymerases (RDRs), small RNA methyltransferase HEN1, and Argonaute (AGO) proteins, that contribute to plant immune responses. The strategies that pathogens have evolved to suppress host small RNA pathways are also discussed. Collectively, host small RNAs and RNA silencing machinery constitute a critical layer of defense in regulating the interaction of pathogens with plants.
Collapse
Affiliation(s)
- Surekha Katiyar-Agarwal
- Department of Plant Molecular Biology, University of Delhi South Campus, New Delhi 110021, India
| | - Hailing Jin
- Departments of Plant Pathology and Microbiology, Center for Plant Cell Biology, Institute for Integrative Genome Biology, University of California, Riverside, California 92521
| |
Collapse
|