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Zhang P, Mbodj A, Soundiramourtty A, Llauro C, Ghesquière A, Ingouff M, Keith Slotkin R, Pontvianne F, Catoni M, Mirouze M. Extrachromosomal circular DNA and structural variants highlight genome instability in Arabidopsis epigenetic mutants. Nat Commun 2023; 14:5236. [PMID: 37640706 PMCID: PMC10462705 DOI: 10.1038/s41467-023-41023-0] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2022] [Accepted: 08/21/2023] [Indexed: 08/31/2023] Open
Abstract
Abundant extrachromosomal circular DNA (eccDNA) is associated with transposable element (TE) activity. However, how the eccDNA compartment is controlled by epigenetic regulations and what is its impact on the genome is understudied. Here, using long reads, we sequence both the eccDNA compartment and the genome of Arabidopsis thaliana mutant plants affected in DNA methylation and post-transcriptional gene silencing. We detect a high load of TE-derived eccDNA with truncated and chimeric forms. On the genomic side, on top of truncated and full length TE neo-insertions, we detect complex structural variations (SVs) notably at a disease resistance cluster being a natural hotspot of SV. Finally, we serendipitously identify large tandem duplications in hypomethylated plants, suggesting that SVs could have been overlooked in epigenetic mutants. We propose that a high eccDNA load may alter DNA repair pathways leading to genome instability and the accumulation of SVs, at least in plants.
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Affiliation(s)
- Panpan Zhang
- Institut de Recherche pour le Développement (IRD), Laboratory of Plant Genome and Development, Perpignan, France
- EMR269 MANGO (CNRS/IRD/UPVD), Laboratory of Plant Genome and Development, Perpignan, France
- University of Montpellier, Montpellier, France
| | - Assane Mbodj
- Institut de Recherche pour le Développement (IRD), Laboratory of Plant Genome and Development, Perpignan, France
- EMR269 MANGO (CNRS/IRD/UPVD), Laboratory of Plant Genome and Development, Perpignan, France
| | - Abirami Soundiramourtty
- EMR269 MANGO (CNRS/IRD/UPVD), Laboratory of Plant Genome and Development, Perpignan, France
- University of Perpignan, Perpignan, France
| | - Christel Llauro
- EMR269 MANGO (CNRS/IRD/UPVD), Laboratory of Plant Genome and Development, Perpignan, France
- Centre National de la Recherche Scientifique (CNRS), Laboratory of Plant Genome and Development, Perpignan, France
| | - Alain Ghesquière
- DIADE, University of Montpellier, IRD, CIRAD, Montpellier, France
| | - Mathieu Ingouff
- DIADE, University of Montpellier, IRD, CIRAD, Montpellier, France
| | - R Keith Slotkin
- Donald Danforth Plant Science Center, St. Louis, MO, 63132, USA
- Division of Biological Sciences, University of Missouri, Columbia, MO, 65211, USA
| | - Frédéric Pontvianne
- Centre National de la Recherche Scientifique (CNRS), Laboratory of Plant Genome and Development, Perpignan, France
| | - Marco Catoni
- School of Biosciences, University of Birmingham, Birmingham, B15 2TT, UK
| | - Marie Mirouze
- Institut de Recherche pour le Développement (IRD), Laboratory of Plant Genome and Development, Perpignan, France.
- EMR269 MANGO (CNRS/IRD/UPVD), Laboratory of Plant Genome and Development, Perpignan, France.
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2
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Merkulov P, Egorova E, Kirov I. Composition and Structure of Arabidopsis thaliana Extrachromosomal Circular DNAs Revealed by Nanopore Sequencing. PLANTS (BASEL, SWITZERLAND) 2023; 12:plants12112178. [PMID: 37299157 DOI: 10.3390/plants12112178] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/02/2023] [Revised: 05/19/2023] [Accepted: 05/29/2023] [Indexed: 06/12/2023]
Abstract
Extrachromosomal circular DNAs (eccDNAs) are enigmatic DNA molecules that have been detected in a range of organisms. In plants, eccDNAs have various genomic origins and may be derived from transposable elements. The structures of individual eccDNA molecules and their dynamics in response to stress are poorly understood. In this study, we showed that nanopore sequencing is a useful tool for the detection and structural analysis of eccDNA molecules. Applying nanopore sequencing to the eccDNA molecules of epigenetically stressed Arabidopsis plants grown under various stress treatments (heat, abscisic acid, and flagellin), we showed that TE-derived eccDNA quantity and structure vary dramatically between individual TEs. Epigenetic stress alone did not cause eccDNA up-regulation, whereas its combination with heat stress triggered the generation of full-length and various truncated eccDNAs of the ONSEN element. We showed that the ratio between full-length and truncated eccDNAs is TE- and condition-dependent. Our work paves the way for further elucidation of the structural features of eccDNAs and their connections with various biological processes, such as eccDNA transcription and eccDNA-mediated TE silencing.
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Affiliation(s)
- Pavel Merkulov
- Moscow Institute of Physics and Technology, 141701 Dolgoprudny, Russia
- All-Russia Research Institute of Agricultural Biotechnology, 127550 Moscow, Russia
| | - Ekaterina Egorova
- All-Russia Research Institute of Agricultural Biotechnology, 127550 Moscow, Russia
| | - Ilya Kirov
- Moscow Institute of Physics and Technology, 141701 Dolgoprudny, Russia
- All-Russia Research Institute of Agricultural Biotechnology, 127550 Moscow, Russia
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3
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Bajus M, Macko-Podgórni A, Grzebelus D, Baránek M. A review of strategies used to identify transposition events in plant genomes. FRONTIERS IN PLANT SCIENCE 2022; 13:1080993. [PMID: 36531345 PMCID: PMC9751208 DOI: 10.3389/fpls.2022.1080993] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/26/2022] [Accepted: 11/17/2022] [Indexed: 06/17/2023]
Abstract
Transposable elements (TEs) were initially considered redundant and dubbed 'junk DNA'. However, more recently they were recognized as an essential element of genome plasticity. In nature, they frequently become active upon exposition of the host to stress conditions. Even though most transposition events are neutral or even deleterious, occasionally they may happen to be beneficial, resulting in genetic novelty providing better fitness to the host. Hence, TE mobilization may promote adaptability and, in the long run, act as a significant evolutionary force. There are many examples of TE insertions resulting in increased tolerance to stresses or in novel features of crops which are appealing to the consumer. Possibly, TE-driven de novo variability could be utilized for crop improvement. However, in order to systematically study the mechanisms of TE/host interactions, it is necessary to have suitable tools to globally monitor any ongoing TE mobilization. With the development of novel potent technologies, new high-throughput strategies for studying TE dynamics are emerging. Here, we present currently available methods applied to monitor the activity of TEs in plants. We divide them on the basis of their operational principles, the position of target molecules in the process of transposition and their ability to capture real cases of actively transposing elements. Their possible theoretical and practical drawbacks are also discussed. Finally, conceivable strategies and combinations of methods resulting in an improved performance are proposed.
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Affiliation(s)
- Marko Bajus
- Mendeleum—Institute of Genetics, Faculty of Horticulture, Mendel University in Brno, Lednice, Czechia
| | - Alicja Macko-Podgórni
- Department of Plant Biology and Biotechnology, Faculty of Biotechnology and Horticulture, University of Agriculture in Krakow, Kraków, Poland
| | - Dariusz Grzebelus
- Department of Plant Biology and Biotechnology, Faculty of Biotechnology and Horticulture, University of Agriculture in Krakow, Kraków, Poland
| | - Miroslav Baránek
- Mendeleum—Institute of Genetics, Faculty of Horticulture, Mendel University in Brno, Lednice, Czechia
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Peng H, Mirouze M, Bucher E. Extrachromosomal circular DNA: A neglected nucleic acid molecule in plants. CURRENT OPINION IN PLANT BIOLOGY 2022; 69:102263. [PMID: 35872391 DOI: 10.1016/j.pbi.2022.102263] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/25/2022] [Revised: 06/15/2022] [Accepted: 06/19/2022] [Indexed: 06/15/2023]
Abstract
Throughout the years, most plant genomic studies were focused on nuclear chromosomes. Extrachromosomal circular DNA (eccDNA) has largely been neglected for decades since its discovery in 1965. While initial research showed that eccDNAs can originate from highly repetitive sequences, recent findings show that many regions of the genome can contribute to the eccDNA pool. Currently, the biological functions of eccDNAs, if any, are a mystery but recent studies have indicated that they can be regulated by different genomic loci and contribute to stress response and adaptation. In this review, we outline current relevant technological developments facilitating eccDNA identification and the latest discoveries about eccDNAs in plants. Finally, we explore the probable functions and future research directions that could be undertaken with respect to different eccDNA sources.
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Affiliation(s)
- Haoran Peng
- Crop Genome Dynamics Group, Agroscope Changins, 1260, Nyon, Switzerland; Department of Botany and Plant Biology, Section of Biology, Faculty of Science, University of Geneva, 1211, Geneva, Switzerland
| | - Marie Mirouze
- Institut de Recherche pour le Développement (IRD), EMR269 MANGO, Université de Perpignan, 66860 Perpignan, France; Laboratory of Plant Genome and Development, Université de Perpignan, 66860, Perpignan, France.
| | - Etienne Bucher
- Crop Genome Dynamics Group, Agroscope Changins, 1260, Nyon, Switzerland.
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5
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Kwolek K, Kędzierska P, Hankiewicz M, Mirouze M, Panaud O, Grzebelus D, Macko‐Podgórni A. Diverse and mobile: eccDNA-based identification of carrot low-copy-number LTR retrotransposons active in callus cultures. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2022; 110:1811-1828. [PMID: 35426957 PMCID: PMC9324142 DOI: 10.1111/tpj.15773] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/21/2021] [Revised: 03/15/2022] [Accepted: 03/29/2022] [Indexed: 05/28/2023]
Abstract
Long terminal repeat retrotransposons (LTR-RTs) are mobilized via an RNA intermediate using a 'copy and paste' mechanism, and account for the majority of repetitive DNA in plant genomes. As a side effect of mobilization, the formation of LTR-RT-derived extrachromosomal circular DNAs (eccDNAs) occurs. Thus, high-throughput sequencing of eccDNA can be used to identify active LTR-RTs in plant genomes. Despite the release of a reference genome assembly, carrot LTR-RTs have not yet been thoroughly characterized. LTR-RTs are abundant and diverse in the carrot genome. We identified 5976 carrot LTR-RTs, 2053 and 1660 of which were attributed to Copia and Gypsy superfamilies, respectively. They were further classified into lineages, families and subfamilies. More diverse LTR-RT lineages, i.e. lineages comprising many low-copy-number subfamilies, were more frequently associated with genic regions. Certain LTR-RT lineages have been recently active in Daucus carota. In particular, low-copy-number LTR-RT subfamilies, e.g. those belonging to the DcAle lineage, have significantly contributed to carrot genome diversity as a result of continuing activity. We utilized eccDNA sequencing to identify and characterize two DcAle subfamilies, Alex1 and Alex3, active in carrot callus. We documented 14 and 32 de novo insertions of Alex1 and Alex3, respectively, which were positioned in non-repetitive regions.
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Affiliation(s)
- Kornelia Kwolek
- Department of Plant Biology and Biotechnology, Faculty of Biotechnology and HorticultureUniversity of Agriculture in Krakow31 120KrakowPoland
| | - Patrycja Kędzierska
- Department of Plant Biology and Biotechnology, Faculty of Biotechnology and HorticultureUniversity of Agriculture in Krakow31 120KrakowPoland
| | - Magdalena Hankiewicz
- Department of Plant Biology and Biotechnology, Faculty of Biotechnology and HorticultureUniversity of Agriculture in Krakow31 120KrakowPoland
| | - Marie Mirouze
- Laboratoire Génome et Développement des Plantes, UMR 5096 CNRS/UPVDUniversité de PerpignanVia Domitia, 52 Avenue Paul Alduy66 860Perpignan CedexFrance
- IRD, EMR IRD‐CNRS‐UPVD ‘MANGO’Université de PerpignanPerpignanFrance
| | - Olivier Panaud
- Laboratoire Génome et Développement des Plantes, UMR 5096 CNRS/UPVDUniversité de PerpignanVia Domitia, 52 Avenue Paul Alduy66 860Perpignan CedexFrance
| | - Dariusz Grzebelus
- Department of Plant Biology and Biotechnology, Faculty of Biotechnology and HorticultureUniversity of Agriculture in Krakow31 120KrakowPoland
| | - Alicja Macko‐Podgórni
- Department of Plant Biology and Biotechnology, Faculty of Biotechnology and HorticultureUniversity of Agriculture in Krakow31 120KrakowPoland
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Zhang P, Peng H, Llauro C, Bucher E, Mirouze M. ecc_finder: A Robust and Accurate Tool for Detecting Extrachromosomal Circular DNA From Sequencing Data. FRONTIERS IN PLANT SCIENCE 2021; 12:743742. [PMID: 34925397 PMCID: PMC8672306 DOI: 10.3389/fpls.2021.743742] [Citation(s) in RCA: 26] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/19/2021] [Accepted: 10/25/2021] [Indexed: 06/06/2023]
Abstract
Extrachromosomal circular DNA (eccDNA) has been observed in different species for decades, and more and more evidence shows that this specific type of DNA molecules may play an important role in rapid adaptation. Therefore, characterizing the full landscape of eccDNA has become critical, and there are several protocols for enriching eccDNAs and performing short-read or long-read sequencing. However, there is currently no available bioinformatic tool to identify eccDNAs from Nanopore reads. More importantly, the current tools based on Illumina short reads lack an efficient standardized pipeline notably to identify eccDNA originating from repeated loci and cannot be applied to very large genomes. Here, we introduce a comprehensive tool to solve both of these two issues. Applying ecc_finder to eccDNA-seq data (either mobilome-seq, Circle-Seq and CIDER-seq) from Arabidopsis, human, and wheat (with genome sizes ranging from 120Mb to 17 Gb), we document the improvement of computational time, sensitivity, and accuracy and demonstrate ecc_finder wide applicability and functionality.
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Affiliation(s)
- Panpan Zhang
- Institut de Recherche pour le Développement (IRD), Montpellier, France
- Laboratory of Plant Genome and Development, University of Perpignan, Perpignan, France
| | - Haoran Peng
- Crop Genome Dynamics Group, Agroscope Changins, Nyon, Switzerland
- Department of Botany and Plant Biology, Section of Biology, Faculty of Science, University of Geneva, Geneva, Switzerland
| | - Christel Llauro
- Laboratory of Plant Genome and Development, University of Perpignan, Perpignan, France
- Laboratory of Plant Genome and Development, Centre National de la Recherche Scientifique (CNRS), Perpignan, France
| | - Etienne Bucher
- Crop Genome Dynamics Group, Agroscope Changins, Nyon, Switzerland
| | - Marie Mirouze
- Institut de Recherche pour le Développement (IRD), Montpellier, France
- Laboratory of Plant Genome and Development, University of Perpignan, Perpignan, France
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7
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Molin WT, Patterson EL, Saski CA. Homogeneity among glyphosate-resistant Amaranthus palmeri in geographically distant locations. PLoS One 2020; 15:e0233813. [PMID: 32903277 PMCID: PMC7480871 DOI: 10.1371/journal.pone.0233813] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2020] [Accepted: 08/10/2020] [Indexed: 02/06/2023] Open
Abstract
Since the initial report of glyphosate-resistant (GR) Amaranthus palmeri S. Watson in 2006, resistant populations have been reported in 28 states. The mechanism of resistance is amplification of a 399-kb extrachromosomal circular DNA, called the EPSPS replicon, and is unique to glyphosate-resistant plants. The replicon contains a single copy of the 10-kb 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) gene which causes the concomitant increased expression of EPSP synthase, the target enzyme of glyphosate. It is not known whether the resistance by this amplification mechanism evolved once and then spread across the country or evolved independently in several locations. To compare genomic representation and variation across the EPSPS replicon, whole genome shotgun sequencing (WGS) and mapping of sequences from both GR and susceptible (GS) biotypes to the replicon consensus sequence was performed. Sampling of GR biotypes from AZ, KS, GA, MD and DE and GS biotypes from AZ, KS and GA revealed complete contiguity and deep representation with sequences from GR plants, but lack of homogeneity and contiguity with breaks in coverage were observed with sequences from GS biotypes. The high sequence conservation among GR biotypes with very few polymorphisms which were widely distributed across the USA further supports the hypothesis that glyphosate resistance most likely originated from a single population. We show that the replicon from different populations was unique to GR plants and had similar levels of amplification.
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Affiliation(s)
- William T. Molin
- Crop Production Systems Research Unit, United States Department of Agriculture, Stoneville, Mississippi, United States of America
| | - Eric L. Patterson
- Department of Plant, Soil, and Microbial Sciences, Michigan State University, East Lansing, Michigan, United States of America
| | - Christopher A. Saski
- Department of Plant and Environmental Sciences, Clemson University, Clemson, South Carolina, United States of America
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Lancíková V, Žiarovská J. Inter-retrotransposon amplified polymorphism markers revealed long terminal repeat retrotransposon insertion polymorphism in flax cultivated on the experimental fields around Chernobyl. JOURNAL OF ENVIRONMENTAL SCIENCE AND HEALTH. PART A, TOXIC/HAZARDOUS SUBSTANCES & ENVIRONMENTAL ENGINEERING 2020; 55:957-963. [PMID: 32378983 DOI: 10.1080/10934529.2020.1760016] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/27/2020] [Revised: 04/14/2020] [Accepted: 04/16/2020] [Indexed: 06/11/2023]
Abstract
Ionizing radiation in environment comes from various natural and anthropogenic sources. The effect of radioactivity released after the CNPP (Chernobyl Nuclear Power Plant) on plant systems remains of great interest. Even now, more than three decades after the nuclear accident, the long-lived radionuclides represent a strong stress factor. Herein, the emphasis has been placed on analysis of genetic variability represented by activation of LTR (Long Terminal Repeat)-retrotransposons. Polymorphism in LTR-retrotransposon insertions has been investigated throughout the genome of two flax varieties, Kyivskyi and Bethune. For this purpose, two retrotransposon-based marker techniques, IRAP (Inter-Retrotransposon Amplified Polymorphism) and iPBS (inter-Primer Binding Site), have been employed. The hypothesis that chronic radioactive stress may induce mechanism of retransposition has been supported by the activation of FL9, FL11 and FL12 LTR-retrotransposons in flax seeds harvested from radioactive environment. Out of two retrotransposon-based approaches, IRAP appears to be more suitable for identification of LTR-retrotransposon polymorphism. Even though the LTR-retrotransposon polymorphism was identified, the results suggest the high level of plant adaptation in the radioactive Chernobyl area. However, it is not really surprising that plants developed an effective strategy to survive in radio-contaminated environment over the past 30 years.
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Affiliation(s)
- Veronika Lancíková
- Plant Science and Biodiversity Center, Institute of Plant Genetics and Biotechnology, Slovak Academy of Sciences, Nitra, Slovakia
| | - Jana Žiarovská
- Department of Genetics and Plant Breeding, Faculty of Agrobiology and Food Resources, Slovak University of Agriculture, Nitra, Slovakia
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Sequencing the extrachromosomal circular mobilome reveals retrotransposon activity in plants. PLoS Genet 2017; 13:e1006630. [PMID: 28212378 PMCID: PMC5338827 DOI: 10.1371/journal.pgen.1006630] [Citation(s) in RCA: 89] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2016] [Revised: 03/06/2017] [Accepted: 02/10/2017] [Indexed: 11/19/2022] Open
Abstract
Retrotransposons are mobile genetic elements abundant in plant and animal genomes. While efficiently silenced by the epigenetic machinery, they can be reactivated upon stress or during development. Their level of transcription not reflecting their transposition ability, it is thus difficult to evaluate their contribution to the active mobilome. Here we applied a simple methodology based on the high throughput sequencing of extrachromosomal circular DNA (eccDNA) forms of active retrotransposons to characterize the repertoire of mobile retrotransposons in plants. This method successfully identified known active retrotransposons in both Arabidopsis and rice material where the epigenome is destabilized. When applying mobilome-seq to developmental stages in wild type rice, we identified PopRice as a highly active retrotransposon producing eccDNA forms in the wild type endosperm. The mobilome-seq strategy opens new routes for the characterization of a yet unexplored fraction of plant genomes.
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Pulkkinen E, Haapa-Paananen S, Turakainen H, Savilahti H. A set of mini-Mu transposons for versatile cloning of circular DNA and novel dual-transposon strategy for increased efficiency. Plasmid 2016; 86:46-53. [PMID: 27387339 DOI: 10.1016/j.plasmid.2016.07.002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2016] [Revised: 06/29/2016] [Accepted: 07/02/2016] [Indexed: 12/22/2022]
Abstract
Mu transposition-based cloning of DNA circles employs in vitro transposition reaction to deliver both the plasmid origin of replication and a selectable marker into the target DNA of interest. We report here the construction of a platform for the purpose that contains ten mini-Mu transposons with five different replication origins, enabling a variety of research approaches for the discovery and study of circular DNA. We also demonstrate that the simultaneous use of two transposons, one with the origin of replication and the other with selectable marker, is beneficial as it improves the cloning efficiency by reducing the fraction of autointegration-derived plasmid clones. The constructed transposons now provide a set of new tools for the studies on DNA circles and widen the applicability of Mu transposition based approaches to clone circular DNA from various sources.
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Affiliation(s)
- Elsi Pulkkinen
- Division of Genetics and Physiology, Department of Biology, University of Turku, Vesilinnantie 5, FI-20500 Turku, Finland
| | - Saija Haapa-Paananen
- Division of Genetics and Physiology, Department of Biology, University of Turku, Vesilinnantie 5, FI-20500 Turku, Finland
| | - Hilkka Turakainen
- Institute of Biotechnology, Viikki Biocenter, P.O. Box 56, Viikinkaari 9, FI-00014, University of Helsinki, Helsinki, Finland
| | - Harri Savilahti
- Division of Genetics and Physiology, Department of Biology, University of Turku, Vesilinnantie 5, FI-20500 Turku, Finland; Institute of Biotechnology, Viikki Biocenter, P.O. Box 56, Viikinkaari 9, FI-00014, University of Helsinki, Helsinki, Finland.
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MuA-mediated in vitro cloning of circular DNA: transpositional autointegration and the effect of MuB. Mol Genet Genomics 2016; 291:1181-91. [DOI: 10.1007/s00438-016-1175-2] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2015] [Accepted: 01/21/2016] [Indexed: 11/26/2022]
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Cavrak VV, Lettner N, Jamge S, Kosarewicz A, Bayer LM, Mittelsten Scheid O. How a retrotransposon exploits the plant's heat stress response for its activation. PLoS Genet 2014; 10:e1004115. [PMID: 24497839 PMCID: PMC3907296 DOI: 10.1371/journal.pgen.1004115] [Citation(s) in RCA: 210] [Impact Index Per Article: 21.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2013] [Accepted: 11/28/2013] [Indexed: 11/18/2022] Open
Abstract
Retrotransposons are major components of plant and animal genomes. They amplify by reverse transcription and reintegration into the host genome but their activity is usually epigenetically silenced. In plants, genomic copies of retrotransposons are typically associated with repressive chromatin modifications installed and maintained by RNA-directed DNA methylation. To escape this tight control, retrotransposons employ various strategies to avoid epigenetic silencing. Here we describe the mechanism developed by ONSEN, an LTR-copia type retrotransposon in Arabidopsis thaliana. ONSEN has acquired a heat-responsive element recognized by plant-derived heat stress defense factors, resulting in transcription and production of full length extrachromosomal DNA under elevated temperatures. Further, the ONSEN promoter is free of CG and CHG sites, and the reduction of DNA methylation at the CHH sites is not sufficient to activate the element. Since dividing cells have a more pronounced heat response, the extrachromosomal ONSEN DNA, capable of reintegrating into the genome, accumulates preferentially in the meristematic tissue of the shoot. The recruitment of a major plant heat shock transcription factor in periods of heat stress exploits the plant's heat stress response to achieve the transposon's activation, making it impossible for the host to respond appropriately to stress without losing control over the invader. Transposons are programmed to amplify within their host genomes. In defense, hosts have evolved mechanisms to impede transposon activation, often by epigenetic transcriptional silencing. A constant and likely unending arms race between host and invader has brought about different strategies to mutually counteract the tricks of the other. Several such strategies are combined in one transposon in the Arabidopsis genome. Its promoter is devoid of symmetric sites necessary for stable maintenance of repressive DNA methylation, and a reduction of methylation at the remaining cytosines does not activate the element. More sophisticated still: its promoter shares a sequence motif with heat stress-responsive plant genes and is recognized by a heat-induced plant transcription factor. Whenever the plants must activate their heat stress defense under high temperatures, the transposon is able to generate new extrachromosomal DNA copies that can potentially integrate into new sites of the genome. In addition, the heat response is especially strong in tissue with dividing cells, which form consequently the largest amount of extrachromosomal transposon copies. We see this as an example of a “wolf in sheep's clothing” strategy, whereby the transposon becomes visible as such only under specific stress conditions of its host.
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Affiliation(s)
- Vladimir V. Cavrak
- Gregor Mendel Institute of Molecular Plant Biology, Austrian Academy of Sciences, Vienna, Austria
| | - Nicole Lettner
- Gregor Mendel Institute of Molecular Plant Biology, Austrian Academy of Sciences, Vienna, Austria
| | - Suraj Jamge
- Gregor Mendel Institute of Molecular Plant Biology, Austrian Academy of Sciences, Vienna, Austria
| | - Agata Kosarewicz
- Research Institute of Molecular Pathology, Vienna, Austria; and Institute of Molecular Biotechnology, Austrian Academy of Sciences, Vienna, Austria
| | - Laura Maria Bayer
- Gregor Mendel Institute of Molecular Plant Biology, Austrian Academy of Sciences, Vienna, Austria
| | - Ortrun Mittelsten Scheid
- Gregor Mendel Institute of Molecular Plant Biology, Austrian Academy of Sciences, Vienna, Austria
- * E-mail:
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13
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An siRNA pathway prevents transgenerational retrotransposition in plants subjected to stress. Nature 2011; 472:115-9. [PMID: 21399627 DOI: 10.1038/nature09861] [Citation(s) in RCA: 411] [Impact Index Per Article: 31.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2010] [Accepted: 01/13/2011] [Indexed: 11/09/2022]
Abstract
Eukaryotic genomes consist to a significant extent of retrotransposons that are suppressed by host epigenetic mechanisms, preventing their uncontrolled propagation. However, it is not clear how this is achieved. Here we show that in Arabidopsis seedlings subjected to heat stress, a copia-type retrotransposon named ONSEN (Japanese 'hot spring') not only became transcriptionally active but also synthesized extrachromosomal DNA copies. Heat-induced ONSEN accumulation was stimulated in mutants impaired in the biogenesis of small interfering RNAs (siRNAs); however, there was no evidence of transposition occurring in vegetative tissues. After stress, both ONSEN transcripts and extrachromosomal DNA gradually decayed and were no longer detected after 20-30 days. Surprisingly, a high frequency of new ONSEN insertions was observed in the progeny of stressed plants deficient in siRNAs. Insertion patterns revealed that this transgenerational retrotransposition occurred during flower development and before gametogenesis. Therefore in plants with compromised siRNA biogenesis, memory of stress was maintained throughout development, priming ONSEN to transpose during differentiation of generative organs. Retrotransposition was not observed in the progeny of wild-type plants subjected to stress or in non-stressed mutant controls, pointing to a crucial role of the siRNA pathway in restricting retrotransposition triggered by environmental stress. Finally, we found that natural and experimentally induced variants in ONSEN insertions confer heat responsiveness to nearby genes, and therefore mobility bursts may generate novel, stress-responsive regulatory gene networks.
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Tissue culture-induced novel epialleles of a Myb transcription factor encoded by pericarp color1 in maize. Genetics 2010; 186:843-55. [PMID: 20823340 DOI: 10.1534/genetics.110.117929] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
Plants regenerated from tissue culture often display somaclonal variation, that is, somatic and often meiotically heritable phenotypic variation that can result from both genetic and epigenetic modifications. To better understand the molecular basis of somaclonal variation, we have characterized four unique tissue culture-derived epialleles of the pericarp color1 (p1) gene of maize (Zea mays L.). The progenitor p1 allele, P1-wr, is composed of multiple head-to-tail tandemly arranged copies of the complete gene unit and specifies brick-red phlobaphene pigmentation in the cob glumes. The novel epialleles identified in progeny plants regenerated from tissue culture showed partial to complete loss of p1 function indicated by pink or colorless cob glumes. Loss of pigmentation was correlated with nearly complete loss of p1 steady-state transcripts. DNA gel-blot analysis and genomic bisulfite sequencing showed that silencing of the epialleles was associated with hypermethylation of a region in the second intron of P1-wr. Presence of Unstable factor for orange1 (Ufo1), an unlinked epigenetic modifier of p1, restored the cob glume pigmentation in the silenced alleles, and such reactivation was accompanied by hypomethylation of the p1 sequence. This observation confirmed that silencing of the epialleles is indeed due to epigenetic modifications and that the p1 epialleles were capable of functioning in the presence of the correct trans-acting factors. While the low-copy regions of the genome generally undergo hypomethylation during tissue culture, our study shows that the tandemly repeated genes are also prone to hypermethylation and epigenetic silencing.
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O'Brochta DA, Stosic CD, Pilitt K, Subramanian RA, Hice RH, Atkinson PW. Transpositionally active episomal hAT elements. BMC Mol Biol 2009; 10:108. [PMID: 20003420 PMCID: PMC2803484 DOI: 10.1186/1471-2199-10-108] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2009] [Accepted: 12/14/2009] [Indexed: 01/31/2023] Open
Abstract
Background hAT elements and V(D)J recombination may have evolved from a common ancestral transposable element system. Extrachromosomal, circular forms of transposable elements (referred to here as episomal forms) have been reported yet their biological significance remains unknown. V(D)J signal joints, which resemble episomal transposable elements, have been considered non-recombinogenic products of V(D)J recombination and a safe way to dispose of excised chromosomal sequences. V(D)J signal joints can, however, participate in recombination reactions and the purpose of this study was to determine if hobo and Hermes episomal elements are also recombinogenic. Results Up to 50% of hobo/Hermes episomes contained two intact, inverted-terminal repeats and 86% of these contained from 1-1000 bp of intercalary DNA. Episomal hobo/Hermes elements were recovered from Musca domestica (a natural host of Hermes), Drosophila melanogaster (a natural host of hobo) and transgenic Drosophila melanogaster and Aedes aegypti (with autonomous Hermes elements). Episomal Hermes elements were recovered from unfertilized eggs of M. domestica and D. melanogaster demonstrating their potential for extrachromosomal, maternal transmission. Reintegration of episomal Hermes elements was observed in vitro and in vivo and the presence of Hermes episomes resulted in lower rates of canonical Hermes transposition in vivo. Conclusion Episomal hobo/Hermes elements are common products of element excision and can be maternally transmitted. Episomal forms of Hermes are capable of integration and also of influencing the transposition of canonical elements suggesting biological roles for these extrachromosomal elements in element transmission and regulation.
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Affiliation(s)
- David A O'Brochta
- Center for Biosystems Research, University of Maryland Biotechnology Institute, Rockville, MD 20850, USA.
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16
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Cohen S, Houben A, Segal D. Extrachromosomal circular DNA derived from tandemly repeated genomic sequences in plants. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2008; 53:1027-1034. [PMID: 18088310 DOI: 10.1111/j.1365-313x.2007.03394.x] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
Extrachromosomal circular DNA (eccDNA) is one characteristic of the plasticity of the eukaryotic genome. It was found in various non-plant organisms from yeast to humans. EccDNA is heterogeneous in size and contains sequences derived primarily from repetitive chromosomal DNA. Here, we report the occurrence of eccDNA in small and large genome plant species, as identified using two-dimensional gel electrophoresis. We show that eccDNA is readily detected in both Arabidopsis thaliana and Brachycome dichromosomatica, reflecting a normal phenomenon that occurs in wild-type plants. The size of plant eccDNA ranges from > 2 kb to < 20 kb, which is similar to the sizes found in other organisms. These DNA molecules correspond to 5S ribosomal DNA (rDNA), non-coding chromosomal high-copy tandem repeats and telomeric DNA of both species. Circular multimers of the repeating unit of 5S rDNA were identified in both species. In addition, similar multimers were also demonstrated with the B. dichromosomatica repetitive element Bdm29. Such circular multimers of tandem repeats were found in animal models, suggesting a common mechanism for eccDNA formation among eukaryotes. This mechanism may involve looping-out via intrachromosomal homologous recombination. The implications of these results on genome plasticity and evolutionary processes are discussed.
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Affiliation(s)
- Sarit Cohen
- Department of Molecular Microbiology and Biotechnology, Tel Aviv University, Tel Aviv, Israel.
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Rohr CJB, Ranson H, Wang X, Besansky NJ. Structure and evolution of mtanga, a retrotransposon actively expressed on the Y chromosome of the African malaria vector Anopheles gambiae. Mol Biol Evol 2002; 19:149-62. [PMID: 11801743 DOI: 10.1093/oxfordjournals.molbev.a004067] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Here we report the discovery of a novel family of long terminal repeat (LTR)-retrotransposons designated mtanga-Y, specific to the Y chromosome of the African malaria vector, Anopheles gambiae. mtanga-Y elements represent the first Y-linked sequences and the first members of the Ty1-copia superfamily of retrotransposons described from this mosquito. Analysis of a full-length 4,284-bp element revealed the presence of two intact overlapping open reading frames bounded by LTRs of 119 bp. Evidence suggests that the elements are capable of retrotransposition, as transcripts and potential replication intermediates (one-LTR circles) were detected. However, the approximately 12 copies of mtanga-Y appear to be clustered rather than dispersed on the Y chromosome. Absent from the Y chromosome of four sibling species (A. arabiensis, A. quadriannulatus, A. melas, and A. merus), similar, but often defective, mtanga elements are present elsewhere in these genomes, as well as in A. gambiae. These data are consistent with a relatively recent invasion of the A. gambiae Y chromosome by an intact element. The presence of functional mtanga-Y elements suggests that the Y chromosome may be a source, not just a sink, for retrotransposons.
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Affiliation(s)
- Cherise J B Rohr
- Department of Biological Sciences, University of Notre Dame, IN 46556, USA
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18
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Takeda S, Sugimoto K, Kakutani T, Hirochika H. Linear DNA intermediates of the Tto1 retrotransposon in Gag particles accumulated in stressed tobacco and Arabidopsis thaliana. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2001; 28:307-17. [PMID: 11722773 DOI: 10.1046/j.1365-313x.2001.01151.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
The active transcription of some plant retrotransposons under diverse stress conditions suggests active transposition. However, transposition has been demonstrated only during tissue/cell culture. To examine whether transposition is activated under conditions other than tissue/cell culture, DNA intermediates for retrotransposition of the tobacco retrotransposon Tto1 were analysed. Using transgenic Arabidopsis callus expressing high levels of Tto1 RNA in a ddm1 hypomethylation mutant background, the existence of extrachromosomal Tto1 linear DNA molecules in a Gag-particle fraction was demonstrated. By combination with ligation-mediated PCR amplification, we detected Tto1 linear DNA molecules in particle fractions from callus and methyl jasmonate-treated leaves of tobacco, but not from non-stressed leaves. Tto1 DNA intermediates could not be detected in the tobacco corolla where Tto1 is expressed. These results indicate that the transcriptional activation of Tto1 by defence-related stresses leads to the synthesis of DNA intermediates, whereas post-transcriptional suppression of Tto1 activity is suggested in the corolla.
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Affiliation(s)
- S Takeda
- Molecular Genetics Department, National Institute of Agrobiological Sciences, Tsukuba, Ibaraki 305-8602, Japan
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19
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Okamoto H, Hirochika H. Efficient insertion mutagenesis of Arabidopsis by tissue culture-induced activation of the tobacco retrotransposon Tto1. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2000; 23:291-304. [PMID: 10929123 DOI: 10.1046/j.1365-313x.2000.00779.x] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
The tobacco retrotransposon Tto1 is one of a few active retrotransposons in plants. Its transposition is activated by tissue culture and is primarily regulated at the transcriptional level. Here we demonstrate that Tto1 introduced in Arabidopsis is also activated by tissue culture. Transcription of Tto1 was induced by tissue culture and driven by its LTR promoter. Transposed copies of Tto1 were observed in almost all of the plants regenerated from the explants cultured for only 1 week. A total of 255 independent regenerated lines have been produced, and the average copy number of transposed Tto1 in these lines is estimated to be 3.2. Sequences flanking Tto1 were amplified by thermal asymmetric interlaced (TAIL)-PCR. Of 165 independent amplified products, 123 showed significant homology to known genes or hypothetical protein genes. The insertion sites of Tto1 are spread over all chromosomes and the target site sequence shows moderate consensus. Taken together, these results indicate that Tto1 can be used as a tool for efficient insertion mutagenesis of Arabidopsis which is especially suitable as a reverse genetics system.
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Affiliation(s)
- H Okamoto
- Department of Molecular Genetics, National Institute of Agrobiological Resources, Kannondai 2-1-2, Tsukuba, Ibaraki 305-8602, Japan
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Abstract
Retrotransposons are mobile genetic elements that transpose through reverse transcription of an RNA intermediate. Retrotransposons are ubiquitous in plants and play a major role in plant gene and genome evolution. In many cases, retrotransposons comprise over 50% of nuclear DNA content, a situation that can arise in just a few million years. Plant retrotransposons are structurally and functionally similar to the retrotransposons and retroviruses that are found in other eukaryotic organisms. However, there are important differences in the genomic organization of retrotransposons in plants compared to some other eukaryotes, including their often-high copy numbers, their extensively heterogeneous populations, and their chromosomal dispersion patterns. Recent studies are providing valuable insights into the mechanisms involved in regulating the expression and transposition of retrotransposons. This review describes the structure, genomic organization, expression, regulation, and evolution of retrotransposons, and discusses both their contributions to plant genome evolution and their use as genetic tools in plant biology.
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Affiliation(s)
- A Kumar
- Scottish Crop Research Institute, Invergowrie, Dundee, Scotland.
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Takeda S, Sugimoto K, Otsuki H, Hirochika H. A 13-bp cis-regulatory element in the LTR promoter of the tobacco retrotransposon Tto1 is involved in responsiveness to tissue culture, wounding, methyl jasmonate and fungal elicitors. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 1999; 18:383-93. [PMID: 10406122 DOI: 10.1046/j.1365-313x.1999.00460.x] [Citation(s) in RCA: 107] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
The tobacco Tto1 is one of the few active LTR-retrotransposons of plants, and its transposition is activated by tissue culture and is primarily regulated at the transcriptional level. The expression of Tto1 RNA can also be activated by various stresses, including viral infection, wounding, and treatment with jasmonate, a signal molecule of plant defence responses. It is shown here that the Tto1 LTR promoter is responsible for a high level of expression in cultured tissues of transgenic tobacco plants. We demonstrate that a 13-bp repeated motif (TGGTAGGTGAGAT) in the LTR functions as a cis-regulatory element, which confers the responsiveness to tissue culture, wounding and methyl jasmonate. Fungal elicitors also activate the promoter containing multiple copies of the 13-bp motif. Expression mediated by the 13-bp motif is activated markedly by okadaic acid and moderately by K252a, so that both phosphorylation and dephosphorylation of proteins are possibly involved in the signalling pathways. Interestingly, the 13-bp motif contains a conserved motif, Box L (also called AC-I or H-box like sequence) which has been shown to be involved in the expression of phenylpropanoid synthetic genes. Moreover, extended homologies are found between promoters of Tto1 and an asparagus defence gene, AoPR1, suggesting a possibility that the ancient insertion of an ancestral Tto1-related retrotransposon has provided some of the promoter/regulatory sequences, including the 13-bp motif-related sequence, of the AoPR1 gene. Based on the structural and functional similarity between the two promoters, a possible evolutionary role of the regulatory sequences of LTR-retrotransposons is discussed.
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Affiliation(s)
- S Takeda
- Department of Molecular Genetics, National Institute of Agrobiological Resources, Ibaraki, Japan
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Feuerbach F, Drouaud J, Lucas H. Retrovirus-like end processing of the tobacco Tnt1 retrotransposon linear intermediates of replication. J Virol 1997; 71:4005-15. [PMID: 9094678 PMCID: PMC191553 DOI: 10.1128/jvi.71.5.4005-4015.1997] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
The tobacco retrotransposon Tnt1 can transpose through an RNA intermediate in the heterologous host Arabidopsis thaliana. We report here the identification and characterization of extrachromosomal linear and circular DNA forms of Tnt1 in this heterologous host. Our results demonstrate that Tnt1 linear intermediates possess two extra base pairs at each end compared with Tnt1's integrated forms. Prior to integration into the host genome, the two terminal nucleotides at the 3' end of these linear intermediates are removed, as in the case of the yeast Ty3 retrotransposon and of retroviruses. Our data, together with those from recent studies of Ty3, reinforce the idea that 3' dinucleotide cleavage is not restricted to retroviral integrases and is probably a feature shared by many different retrotransposons' enzymes.
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Affiliation(s)
- F Feuerbach
- Laboratoire de Biologie Cellulaire, Institut National de la Recherche Agronomique, Versailles, France
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