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Mandáková T, Krumpolcová A, Matyášek R, Volkov R, Lysak MA, Kovařík A. Uniparental silencing of 5S rRNA genes in plant allopolyploids - insights from Cardamine (Brassicaceae). THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2024. [PMID: 38838061 DOI: 10.1111/tpj.16850] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/26/2024] [Revised: 04/30/2024] [Accepted: 05/14/2024] [Indexed: 06/07/2024]
Abstract
While the phenomenon of uniparental silencing of 35S rDNA in interspecific hybrids and allopolyploids is well documented, there is a notable absence of information regarding whether such silencing extends to the 5S RNA component of ribosomes. To address this gap in knowledge, we analyzed the 5S and 35S rDNA expression in Cardamine (Brassicaceae) allopolyploids, namely C. × insueta (2n = 3x = 24, genome composition RRA), C. flexuosa (2n = 4x = 32, AAHH), and C. scutata (2n = 4x = 32, PPAA) which share a common diploid ancestor (AA). We employed high-throughput sequencing of transcriptomes and genomes and phylogenetic analyses of 5S rRNA variants. The genomic organization of rDNA was further scrutinized through clustering and fluorescence in situ hybridization. In the C. × insueta allotriploid, we observed uniparental dominant expression of 5S and 35S rDNA loci. In the C. flexuosa and C. scutata allotetraploids, the expression pattern differed, with the 35S rDNA being expressed from the A subgenome, whereas the 5S rDNA was expressed from the partner subgenome. Both C. flexuosa and C. scutata but not C. × insueta showed copy and locus number changes. We conclude that in stabilized allopolyploids, transcription of ribosomal RNA components occurs from different subgenomes. This phenomenon appears to result in the formation of chimeric ribosomes comprising rRNA molecules derived from distinct parental origins. We speculate that the interplay of epigenetic silencing and rDNA rearrangements introduces an additional layer of variation in multimolecule ribosomal complexes, potentially contributing to the evolutionary success of allopolyploids.
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Affiliation(s)
- Terezie Mandáková
- Central European Institute of Technology (CEITEC), Masaryk University, 625 00, Brno, Czech Republic
- Department of Experimental Biology, Faculty of Science, Masaryk University, 611 37, Brno, Czech Republic
| | - Alice Krumpolcová
- Department of Experimental Biology, Faculty of Science, Masaryk University, 611 37, Brno, Czech Republic
- Department of Molecular Epigenetics, Institute of Biophysics, Academy of Sciences of the Czech Republic, 612 00, Brno, Czech Republic
| | - Roman Matyášek
- Department of Molecular Epigenetics, Institute of Biophysics, Academy of Sciences of the Czech Republic, 612 00, Brno, Czech Republic
| | - Roman Volkov
- Department of Molecular Genetics and Biotechnology, Yuriy Fedkovych Chernivtsi National University, 58012, Chernivtsi, Ukraine
| | - Martin A Lysak
- Central European Institute of Technology (CEITEC), Masaryk University, 625 00, Brno, Czech Republic
- Faculty of Science, National Centre for Biomolecular Research, Masaryk University, 625 00, Brno, Czech Republic
| | - Ales Kovařík
- Department of Molecular Epigenetics, Institute of Biophysics, Academy of Sciences of the Czech Republic, 612 00, Brno, Czech Republic
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2
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Schnitzler CE, Chang ES, Waletich J, Quiroga-Artigas G, Wong WY, Nguyen AD, Barreira SN, Doonan LB, Gonzalez P, Koren S, Gahan JM, Sanders SM, Bradshaw B, DuBuc TQ, Febrimarsa, de Jong D, Nawrocki EP, Larson A, Klasfeld S, Gornik SG, Moreland RT, Wolfsberg TG, Phillippy AM, Mullikin JC, Simakov O, Cartwright P, Nicotra M, Frank U, Baxevanis AD. The genome of the colonial hydroid Hydractinia reveals that their stem cells use a toolkit of evolutionarily shared genes with all animals. Genome Res 2024; 34:498-513. [PMID: 38508693 PMCID: PMC11067881 DOI: 10.1101/gr.278382.123] [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: 08/25/2023] [Accepted: 03/07/2024] [Indexed: 03/22/2024]
Abstract
Hydractinia is a colonial marine hydroid that shows remarkable biological properties, including the capacity to regenerate its entire body throughout its lifetime, a process made possible by its adult migratory stem cells, known as i-cells. Here, we provide an in-depth characterization of the genomic structure and gene content of two Hydractinia species, Hydractinia symbiolongicarpus and Hydractinia echinata, placing them in a comparative evolutionary framework with other cnidarian genomes. We also generated and annotated a single-cell transcriptomic atlas for adult male H. symbiolongicarpus and identified cell-type markers for all major cell types, including key i-cell markers. Orthology analyses based on the markers revealed that Hydractinia's i-cells are highly enriched in genes that are widely shared amongst animals, a striking finding given that Hydractinia has a higher proportion of phylum-specific genes than any of the other 41 animals in our orthology analysis. These results indicate that Hydractinia's stem cells and early progenitor cells may use a toolkit shared with all animals, making it a promising model organism for future exploration of stem cell biology and regenerative medicine. The genomic and transcriptomic resources for Hydractinia presented here will enable further studies of their regenerative capacity, colonial morphology, and ability to distinguish self from nonself.
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Affiliation(s)
- Christine E Schnitzler
- Whitney Laboratory for Marine Bioscience, University of Florida, St. Augustine, Florida 32080, USA
- Department of Biology, University of Florida, Gainesville, Florida 32611, USA
| | - E Sally Chang
- Division of Intramural Research, National Human Genome Research Institute, National Institutes of Health, Bethesda, Maryland 20892, USA
- National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Justin Waletich
- Whitney Laboratory for Marine Bioscience, University of Florida, St. Augustine, Florida 32080, USA
- Department of Biology, University of Florida, Gainesville, Florida 32611, USA
| | - Gonzalo Quiroga-Artigas
- Whitney Laboratory for Marine Bioscience, University of Florida, St. Augustine, Florida 32080, USA
- Department of Biology, University of Florida, Gainesville, Florida 32611, USA
- Centre de Recherche en Biologie cellulaire de Montpellier (CRBM), Université de Montpellier, Centre National de la Recherche Scientifique, 34293 Montpellier CEDEX 05, France
| | - Wai Yee Wong
- Department for Neurosciences and Developmental Biology, University of Vienna, 1030 Vienna, Austria
| | - Anh-Dao Nguyen
- Division of Intramural Research, National Human Genome Research Institute, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Sofia N Barreira
- Division of Intramural Research, National Human Genome Research Institute, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Liam B Doonan
- Centre for Chromosome Biology, College of Science and Engineering, University of Galway, Galway H91 W2TY, Ireland
| | - Paul Gonzalez
- Division of Intramural Research, National Human Genome Research Institute, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Sergey Koren
- Division of Intramural Research, National Human Genome Research Institute, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - James M Gahan
- Centre for Chromosome Biology, College of Science and Engineering, University of Galway, Galway H91 W2TY, Ireland
- Department of Biochemistry, University of Oxford, Oxford OX1 3QU, United Kingdom
| | - Steven M Sanders
- Department of Surgery, Thomas E. Starzl Transplantation Institute, University of Pittsburgh, Pittsburgh, Pennsylvania 15261, USA
- Pittsburgh Center for Evolutionary Biology and Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania 15261, USA
| | - Brian Bradshaw
- Centre for Chromosome Biology, College of Science and Engineering, University of Galway, Galway H91 W2TY, Ireland
| | - Timothy Q DuBuc
- Centre for Chromosome Biology, College of Science and Engineering, University of Galway, Galway H91 W2TY, Ireland
- Department of Biology, Swarthmore College, Swarthmore, Pennsylvania 19081, USA
| | - Febrimarsa
- Centre for Chromosome Biology, College of Science and Engineering, University of Galway, Galway H91 W2TY, Ireland
- Pharmaceutical Biology Laboratory, Faculty of Pharmacy, Universitas Muhammadiyah Surakarta, Jawa Tengah 57169, Indonesia
| | - Danielle de Jong
- Whitney Laboratory for Marine Bioscience, University of Florida, St. Augustine, Florida 32080, USA
- Department of Biology, University of Florida, Gainesville, Florida 32611, USA
| | - Eric P Nawrocki
- National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Alexandra Larson
- Whitney Laboratory for Marine Bioscience, University of Florida, St. Augustine, Florida 32080, USA
| | - Samantha Klasfeld
- Division of Intramural Research, National Human Genome Research Institute, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Sebastian G Gornik
- Centre for Chromosome Biology, College of Science and Engineering, University of Galway, Galway H91 W2TY, Ireland
- Center for Organismal Studies, University of Heidelberg, 69117 Heidelberg, Germany
| | - R Travis Moreland
- Division of Intramural Research, National Human Genome Research Institute, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Tyra G Wolfsberg
- Division of Intramural Research, National Human Genome Research Institute, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Adam M Phillippy
- Division of Intramural Research, National Human Genome Research Institute, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - James C Mullikin
- Division of Intramural Research, National Human Genome Research Institute, National Institutes of Health, Bethesda, Maryland 20892, USA
- NIH Intramural Sequencing Center, Rockville, Maryland 20852, USA
| | - Oleg Simakov
- Department for Neurosciences and Developmental Biology, University of Vienna, 1030 Vienna, Austria
| | - Paulyn Cartwright
- Department of Evolution and Ecology, University of Kansas, Lawrence, Kansas 66045, USA
| | - Matthew Nicotra
- Department of Surgery, Thomas E. Starzl Transplantation Institute, University of Pittsburgh, Pittsburgh, Pennsylvania 15261, USA
- Pittsburgh Center for Evolutionary Biology and Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania 15261, USA
| | - Uri Frank
- Centre for Chromosome Biology, College of Science and Engineering, University of Galway, Galway H91 W2TY, Ireland
| | - Andreas D Baxevanis
- Division of Intramural Research, National Human Genome Research Institute, National Institutes of Health, Bethesda, Maryland 20892, USA;
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3
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Cao L, Chen P, Hou X, Ma J, Yang N, Lu Y, Huang H. rDNA and mtDNA analysis for the identification of genetic characters in the hybrid grouper derived from hybridization of Cromileptes altivelis (female) × Epinephelus lanceolatus (male). BMC Genom Data 2024; 25:5. [PMID: 38216865 PMCID: PMC10787421 DOI: 10.1186/s12863-023-01188-5] [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: 08/09/2023] [Accepted: 12/20/2023] [Indexed: 01/14/2024] Open
Abstract
BACKGROUND Hybridization is a useful strategy to produce offspring with more desirable phenotypic characteristics than those of parents. The hybrid grouper derived from the cross of Cromileptes altivelis (♀, 2n = 48) with Epinephelus lanceolatus (♂, 2n = 48) exhibits improved growth compared with its female parent, which makes it valuable to aquaculture. However, the genetic traits of the hybrid grouper are poorly understood. RESULTS The observations showed that the hybrid grouper was diploid (2n = 48) and displayed intermediate morphology with the parent's measurable characteristics. The ribosomal DNA (rDNA) and mitochondria DNA (mtDNA) were characterized at molecular and phylogenetic level. High similarity and low genetic distance of 5S rDNA and mtDNA sequences between the hybrid grouper and C. altivelis showed that the hybrid grouper had a closer genetic relationship with female parents. The reconstructed phylogenetic tree based on COI gene and D-loop region of mtDNA recovered that mtDNA was maternally inherited in the hybrid grouper. Additionally, the DNA methylation level of 5S rDNA intergenic spacers (IGS) sequence was tested in here. The results showed that the DNA methylation status of the hybrid grouper was significantly lower than that of C. altivelis. CONCLUSION Results of this study provide important data on the genetic characteristics of the hybrid derived from the cross of C. altivelis and E. lanceolatus, and contribute the knowledge of both evolution and marine fish breeding.
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Affiliation(s)
- Liu Cao
- Yazhou Bay Innovation Institute, Sanya, 572022, China
- Key Laboratory of Utilization and Conservation for Tropical Marine Bioresources of Ministry of Education, Sanya, 572022, China
- Hainan Key Laboratory for Conservation and Utilization of Tropical Marine Fishery Resources, Sanya, 572022, China
- Hainan Tropical Ocean University, Sanya, 572022, China
| | - Pan Chen
- Key Laboratory of Utilization and Conservation for Tropical Marine Bioresources of Ministry of Education, Sanya, 572022, China
- Hainan Key Laboratory for Conservation and Utilization of Tropical Marine Fishery Resources, Sanya, 572022, China
- Hainan Tropical Ocean University, Sanya, 572022, China
| | - Xingrong Hou
- Yazhou Bay Innovation Institute, Sanya, 572022, China
- Key Laboratory of Utilization and Conservation for Tropical Marine Bioresources of Ministry of Education, Sanya, 572022, China
- Hainan Key Laboratory for Conservation and Utilization of Tropical Marine Fishery Resources, Sanya, 572022, China
- Hainan Tropical Ocean University, Sanya, 572022, China
| | - Jun Ma
- Yazhou Bay Innovation Institute, Sanya, 572022, China
- Key Laboratory of Utilization and Conservation for Tropical Marine Bioresources of Ministry of Education, Sanya, 572022, China
- Hainan Key Laboratory for Conservation and Utilization of Tropical Marine Fishery Resources, Sanya, 572022, China
- Hainan Tropical Ocean University, Sanya, 572022, China
| | - Ning Yang
- Yazhou Bay Innovation Institute, Sanya, 572022, China
- Key Laboratory of Utilization and Conservation for Tropical Marine Bioresources of Ministry of Education, Sanya, 572022, China
- Hainan Key Laboratory for Conservation and Utilization of Tropical Marine Fishery Resources, Sanya, 572022, China
- Hainan Tropical Ocean University, Sanya, 572022, China
| | - Yan Lu
- Hainan Tropical Ocean University, Sanya, 572022, China
| | - Hai Huang
- Yazhou Bay Innovation Institute, Sanya, 572022, China.
- Key Laboratory of Utilization and Conservation for Tropical Marine Bioresources of Ministry of Education, Sanya, 572022, China.
- Hainan Key Laboratory for Conservation and Utilization of Tropical Marine Fishery Resources, Sanya, 572022, China.
- Hainan Tropical Ocean University, Sanya, 572022, China.
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4
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Schnitzler CE, Chang ES, Waletich J, Quiroga-Artigas G, Wong WY, Nguyen AD, Barreira SN, Doonan L, Gonzalez P, Koren S, Gahan JM, Sanders SM, Bradshaw B, DuBuc TQ, Febrimarsa, de Jong D, Nawrocki EP, Larson A, Klasfeld S, Gornik SG, Moreland RT, Wolfsberg TG, Phillippy AM, Mullikin JC, Simakov O, Cartwright P, Nicotra M, Frank U, Baxevanis AD. The genome of the colonial hydroid Hydractinia reveals their stem cells utilize a toolkit of evolutionarily shared genes with all animals. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.08.25.554815. [PMID: 37786714 PMCID: PMC10541594 DOI: 10.1101/2023.08.25.554815] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/04/2023]
Abstract
Hydractinia is a colonial marine hydroid that exhibits remarkable biological properties, including the capacity to regenerate its entire body throughout its lifetime, a process made possible by its adult migratory stem cells, known as i-cells. Here, we provide an in-depth characterization of the genomic structure and gene content of two Hydractinia species, H. symbiolongicarpus and H. echinata, placing them in a comparative evolutionary framework with other cnidarian genomes. We also generated and annotated a single-cell transcriptomic atlas for adult male H. symbiolongicarpus and identified cell type markers for all major cell types, including key i-cell markers. Orthology analyses based on the markers revealed that Hydractinia's i-cells are highly enriched in genes that are widely shared amongst animals, a striking finding given that Hydractinia has a higher proportion of phylum-specific genes than any of the other 41 animals in our orthology analysis. These results indicate that Hydractinia's stem cells and early progenitor cells may use a toolkit shared with all animals, making it a promising model organism for future exploration of stem cell biology and regenerative medicine. The genomic and transcriptomic resources for Hydractinia presented here will enable further studies of their regenerative capacity, colonial morphology, and ability to distinguish self from non-self.
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Affiliation(s)
- Christine E Schnitzler
- Whitney Laboratory for Marine Bioscience, University of Florida, St. Augustine, FL 32080, USA
- Department of Biology, University of Florida, Gainesville, FL 32611, USA
| | - E Sally Chang
- Division of Intramural Research, National Human Genome Research Institute, National Institutes of Health, Bethesda, MD 20892, USA
- National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, MD 20892, USA
| | - Justin Waletich
- Whitney Laboratory for Marine Bioscience, University of Florida, St. Augustine, FL 32080, USA
- Department of Biology, University of Florida, Gainesville, FL 32611, USA
| | - Gonzalo Quiroga-Artigas
- Whitney Laboratory for Marine Bioscience, University of Florida, St. Augustine, FL 32080, USA
- Department of Biology, University of Florida, Gainesville, FL 32611, USA
- Centre de Recherche en Biologie cellulaire de Montpellier (CRBM), Université de Montpellier, Centre National de la Recherche Scientifique, 34293 Montpellier CEDEX 05, France
| | - Wai Yee Wong
- Department of Molecular Evolution and Development, Faculty of Life Science, University of Vienna, A-1090 Vienna, Austria
| | - Anh-Dao Nguyen
- Division of Intramural Research, National Human Genome Research Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Sofia N Barreira
- Division of Intramural Research, National Human Genome Research Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Liam Doonan
- Centre for Chromosome Biology, College of Science and Engineering, University of Galway, Galway, Ireland
| | - Paul Gonzalez
- Division of Intramural Research, National Human Genome Research Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Sergey Koren
- Division of Intramural Research, National Human Genome Research Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - James M Gahan
- Centre for Chromosome Biology, College of Science and Engineering, University of Galway, Galway, Ireland
- Department of Biochemistry, University of Oxford, Oxford, UK
| | - Steven M Sanders
- Department of Surgery, Thomas E. Starzl Transplantation Institute, University of Pittsburgh, Pittsburgh, PA 15261, USA
- Pittsburgh Center for Evolutionary Biology and Medicine, University of Pittsburgh, Pittsburgh, PA 15261, USA
| | - Brian Bradshaw
- Centre for Chromosome Biology, College of Science and Engineering, University of Galway, Galway, Ireland
| | - Timothy Q DuBuc
- Centre for Chromosome Biology, College of Science and Engineering, University of Galway, Galway, Ireland
- Swarthmore College, Swarthmore, PA 19081, USA
| | - Febrimarsa
- Centre for Chromosome Biology, College of Science and Engineering, University of Galway, Galway, Ireland
| | - Danielle de Jong
- Whitney Laboratory for Marine Bioscience, University of Florida, St. Augustine, FL 32080, USA
- Department of Biology, University of Florida, Gainesville, FL 32611, USA
| | - Eric P Nawrocki
- National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, MD 20892, USA
| | - Alexandra Larson
- Whitney Laboratory for Marine Bioscience, University of Florida, St. Augustine, FL 32080, USA
| | - Samantha Klasfeld
- Division of Intramural Research, National Human Genome Research Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Sebastian G Gornik
- Centre for Chromosome Biology, College of Science and Engineering, University of Galway, Galway, Ireland
- Centre for Organismal Studies, University of Heidelberg, Germany
| | - R Travis Moreland
- Division of Intramural Research, National Human Genome Research Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Tyra G Wolfsberg
- Division of Intramural Research, National Human Genome Research Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Adam M Phillippy
- Division of Intramural Research, National Human Genome Research Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - James C Mullikin
- Division of Intramural Research, National Human Genome Research Institute, National Institutes of Health, Bethesda, MD 20892, USA
- NIH Intramural Sequencing Center, Rockville, MD 20852, USA
| | - Oleg Simakov
- Department of Molecular Evolution and Development, Faculty of Life Science, University of Vienna, A-1090 Vienna, Austria
| | - Paulyn Cartwright
- Department of Evolution and Ecology, University of Kansas, Lawrence, KS 66045, USA
| | - Matthew Nicotra
- Department of Surgery, Thomas E. Starzl Transplantation Institute, University of Pittsburgh, Pittsburgh, PA 15261, USA
- Pittsburgh Center for Evolutionary Biology and Medicine, University of Pittsburgh, Pittsburgh, PA 15261, USA
| | - Uri Frank
- Centre for Chromosome Biology, College of Science and Engineering, University of Galway, Galway, Ireland
| | - Andreas D Baxevanis
- Division of Intramural Research, National Human Genome Research Institute, National Institutes of Health, Bethesda, MD 20892, USA
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5
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Wang Y, Chen Y, Wei Q, Chen X, Wan H, Sun C. Characterization of repetitive sequences in Dendrobium officinale and comparative chromosomal structures in Dendrobium species using FISH. Gene 2022; 846:146869. [PMID: 36075328 DOI: 10.1016/j.gene.2022.146869] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2022] [Revised: 08/26/2022] [Accepted: 09/01/2022] [Indexed: 11/04/2022]
Abstract
Tandem repeats are one of the most conserved features in the eukaryote genomes. Dendrobium is the third largest genus in family Orchidaceae compromising over 1,200 species. However, the organization of repetitive sequences in Dendrobium species remains unclear. In this study, we performed the identification and characterization of the tandem repeats in D. officinale genome using graph-based clustering and Fluorescence in situ hybridization (FISH). Six major clusters including five satellite DNAs (DofSat1-5) and one 5S rDNA repeat (Dof5S) were identified as tandem repeats. The tandem organization of DofSat5 was verified by PCR amplification and southern blotting. The chromosomal locations of the repetitive DNAs in D. officinale were investigated by FISH using the tandem repeats and oligos probes. The results showed that each of the DofSat5, 5S and 45S rDNA had one pair of strong signals on D. officinale chromosomes. The distribution of repetitive DNAs along chromosomes was also investigated based on genomic in situ hybridization (GISH) among four Dendrobium species. The results suggested complex chromosomal fusion/segmentation and rearrangements during the evolution of Dendrobium species. In conclusion, the present study provides new landmarks for unequival differentiation of the Dendrobium chromosomes and facilitate the understanding the chromosome evolution in Dendrobium speceis.
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Affiliation(s)
- Yunzhu Wang
- Institute of Horticulture Research, Zhejiang Academy of Agricultural Sciences, Hangzhou 310021, China.
| | - Yue Chen
- Institute of Horticulture Research, Zhejiang Academy of Agricultural Sciences, Hangzhou 310021, China.
| | - Qingzhen Wei
- Institute of Vegetable Research, Zhejiang Academy of Agricultural Sciences, Hangzhou 310021, China.
| | - Xiaoyang Chen
- Seed Management Terminal of Zhejiang, Hangzhou 310021, China.
| | - Hongjian Wan
- Institute of Vegetable Research, Zhejiang Academy of Agricultural Sciences, Hangzhou 310021, China.
| | - Chongbo Sun
- Institute of Horticulture Research, Zhejiang Academy of Agricultural Sciences, Hangzhou 310021, China.
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Scoppola A, Cardoni S, Marcussen T, Simeone MC. Complex Scenarios of Reticulation, Polyploidization, and Species Diversity within Annual Pansies of Subsect. Bracteolatae (Viola Sect. Melanium, Violaceae) in Italy: Insights from 5S-IGS High-Throughput Sequencing and Plastid DNA Variation. PLANTS 2022; 11:plants11101294. [PMID: 35631718 PMCID: PMC9147628 DOI: 10.3390/plants11101294] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/03/2022] [Revised: 04/02/2022] [Accepted: 05/11/2022] [Indexed: 01/02/2023]
Abstract
Viola sect. Melanium, the so-called pansy, is an allopolyploid morphologically well-defined lineage of ca. 110 perennial and annual species in the northern hemisphere, characterized by markedly complex genomic configurations. Five annual pansies occur in Italy, four of which are morphologically very similar and belong to the informal ‘V. tricolor species complex’: V. arvensis (2n = 34), V. hymettia (2n = 16), V. kitaibeliana (2n = 16), and V. tricolor (2n = 26). Their field recognition is difficult and reflects a long-debated taxonomy often resulting in doubtful records in field inventories and across European herbaria. The current lack of comprehensive intra- and interspecific comparative studies and a relative scarcity of appropriate genetic markers coupled with unambiguous cytological descriptions are hindering clear taxa circumscription and phylogenetic inferences within this group. In this work, we tested DNA sequence variation of three highly variable plastid markers and High-Throughput Sequencing (HTS) of the nuclear ribosomal 5S-IGS region in an attempt to decipher species identity within the V. tricolor species complex and to obtain an insight on their genome organization and evolution. Our results document the close relationships within this species group, a reliable molecular resolution for V. tricolor, and the common ancestry of V. arvensis and the poorly differentiated V. kitaibeliana and V. hymettia. Evidence of an important inter-population geographical divergence was recorded in V. tricolor and V. arvensis, pointing at the existence of different eco-cytotypes within these entities. Overall diversity patterns and the occurrence of two to four differently diverging 5S-IGS lineages are discussed in the light of the acknowledged taxonomy and genomic evolutive trajectories of sect. Melanium.
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Affiliation(s)
- Anna Scoppola
- Department of Agricultural and Forestry Sciences (DAFNE), Tuscia University, Via S. Camillo de Lellis, 01100 Viterbo, Italy; (A.S.); (M.C.S.)
| | - Simone Cardoni
- Department of Agricultural and Forestry Sciences (DAFNE), Tuscia University, Via S. Camillo de Lellis, 01100 Viterbo, Italy; (A.S.); (M.C.S.)
- Correspondence:
| | - Thomas Marcussen
- Department of Biosciences, Centre for Ecological and Evolutionary Synthesis (CEES), University of Oslo, P.O. Box 1066, NO-0316 Oslo, Norway;
| | - Marco Cosimo Simeone
- Department of Agricultural and Forestry Sciences (DAFNE), Tuscia University, Via S. Camillo de Lellis, 01100 Viterbo, Italy; (A.S.); (M.C.S.)
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7
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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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8
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Ishchenko OO, Bednarska IO, Panchuk ІІ. Application of 5S Ribosomal DNA for Molecular Taxonomy of Subtribe Loliinae (Poaceae). CYTOL GENET+ 2021. [DOI: 10.3103/s0095452721010096] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
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9
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Ishchenko OO, Mel’nyk VM, Parnikoza ІY, Budzhak VV, Panchuk ІІ, Kunakh VA, Volkov RA. Molecular Organization of 5S Ribosomal DNA and Taxonomic Status of Avenella flexuosa (L.) Drejer (Poaceae). CYTOL GENET+ 2021. [DOI: 10.3103/s0095452720060055] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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10
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Piredda R, Grimm GW, Schulze ED, Denk T, Simeone MC. High-throughput sequencing of 5S-IGS in oaks: Exploring intragenomic variation and algorithms to recognize target species in pure and mixed samples. Mol Ecol Resour 2020; 21:495-510. [PMID: 32997899 DOI: 10.1111/1755-0998.13264] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2020] [Revised: 08/28/2020] [Accepted: 09/01/2020] [Indexed: 11/30/2022]
Abstract
Measuring biological diversity is a crucial but difficult undertaking, as exemplified in oaks where complex patterns of morphological, ecological, biogeographical and genetic differentiation collide with traditional taxonomy, which measures biodiversity in number of species (or higher taxa). In this pilot study, we generated high-throughput sequencing amplicon data of the intergenic spacer of the 5S nuclear ribosomal DNA cistron (5S-IGS) in oaks, using six mock samples that differ in geographical origin, species composition and pool complexity. The potential of the marker for automated genotaxonomy applications was assessed using a reference data set of 1,770 5S-IGS cloned sequences, covering the entire taxonomic breadth and distribution range of western Eurasian Quercus, and applying similarity (blast) and evolutionary approaches (maximum-likelihood trees and Evolutionary Placement Algorithm). Both methods performed equally well, allowing correct identification of species in sections Ilex and Cerris in the pure and mixed samples, and main lineages shared by species of sect. Quercus. Application of different cut-off thresholds revealed that medium- to high-abundance (>10 or 25) sequences suffice for a net species identification of samples containing one or a few individuals. Lower thresholds identify phylogenetic correspondence with all target species in highly mixed samples (analogous to environmental bulk samples) and include rare variants pointing towards reticulation, incomplete lineage sorting, pseudogenic 5S units and in situ (natural) contamination. Our pipeline is highly promising for future assessments of intraspecific and interpopulation diversity, and of the genetic resources of natural ecosystems, which are fundamental to empower fast and solid biodiversity conservation programmes worldwide.
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Affiliation(s)
| | - Guido W Grimm
- Orléans, France.,Department of Palaeontology, University of Vienna, Vienna, Austria
| | | | - Thomas Denk
- Swedish Museum of Natural History, Stockholm, Sweden
| | - Marco Cosimo Simeone
- Dipartimento di Scienze Agrarie e Forestali (DAFNE), Università degli studi della Tuscia, Viterbo, Italy
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11
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First genome survey and repeatome analysis of Chrysopogon zizanioides based on next-generation sequencing. Biologia (Bratisl) 2020. [DOI: 10.2478/s11756-020-00517-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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12
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Tao B, Lo LJ, Peng J, He J. rDNA subtypes and their transcriptional expression in zebrafish at different developmental stages. Biochem Biophys Res Commun 2020; 529:819-825. [PMID: 32571523 DOI: 10.1016/j.bbrc.2020.05.196] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2020] [Accepted: 05/26/2020] [Indexed: 01/21/2023]
Abstract
Eukaryotic 18S, 5.8S and 28S rRNAs are processed from a single transcript transcribed from the 45S rDNA gene, which is normally tandemly arrayed over hundred copies in a genome. Recently, a maternal (M) subtype and a somatic (S) subtype of rDNA were identified in zebrafish, with M-subtype on chromosome 4 and S-subtype on chromosome 5. It appears that the M-subtype is only expressed in eggs whilst the expression of the S-subtype is coupled with the initiation of zygotic gene expression. In this report, we identified three novel but transcriptionally inactive 18S variants in zebrafish genome with chromosome location different from the M- and S-subtype, suggesting translocation of 18S rDNA fragment during zebrafish evolution. Furthermore, we confirmed that the unfertilized eggs only have the M-subtype transcripts while brain, heart and liver have only the S-subtype transcripts. Both the M- and S-subtype transcripts were detected in female gonad. Our results support that the expression of different subtypes of rDNA is differentially regulated to meet the requirement for 'specialized ribosomes' during different developmental stages.
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Affiliation(s)
- Boxiang Tao
- MOE Key Laboratory for Molecular Animal Nutrition, College of Animal Sciences, Zhejiang University, Hangzhou, 310058, China
| | - Li Jan Lo
- MOE Key Laboratory for Molecular Animal Nutrition, College of Animal Sciences, Zhejiang University, Hangzhou, 310058, China
| | - Jinrong Peng
- MOE Key Laboratory for Molecular Animal Nutrition, College of Animal Sciences, Zhejiang University, Hangzhou, 310058, China.
| | - Jin He
- MOE Key Laboratory for Molecular Animal Nutrition, College of Animal Sciences, Zhejiang University, Hangzhou, 310058, China.
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13
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Simon L, Rabanal FA, Dubos T, Oliver C, Lauber D, Poulet A, Vogt A, Mandlbauer A, Le Goff S, Sommer A, Duborjal H, Tatout C, Probst AV. Genetic and epigenetic variation in 5S ribosomal RNA genes reveals genome dynamics in Arabidopsis thaliana. Nucleic Acids Res 2019. [PMID: 29518237 PMCID: PMC5887818 DOI: 10.1093/nar/gky163] [Citation(s) in RCA: 42] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Organized in tandem repeat arrays in most eukaryotes and transcribed by RNA polymerase III, expression of 5S rRNA genes is under epigenetic control. To unveil mechanisms of transcriptional regulation, we obtained here in depth sequence information on 5S rRNA genes from the Arabidopsis thaliana genome and identified differential enrichment in epigenetic marks between the three 5S rDNA loci situated on chromosomes 3, 4 and 5. We reveal the chromosome 5 locus as the major source of an atypical, long 5S rRNA transcript characteristic of an open chromatin structure. 5S rRNA genes from this locus translocated in the Landsberg erecta ecotype as shown by linkage mapping and chromosome-specific FISH analysis. These variations in 5S rDNA locus organization cause changes in the spatial arrangement of chromosomes in the nucleus. Furthermore, 5S rRNA gene arrangements are highly dynamic with alterations in chromosomal positions through translocations in certain mutants of the RNA-directed DNA methylation pathway and important copy number variations among ecotypes. Finally, variations in 5S rRNA gene sequence, chromatin organization and transcripts indicate differential usage of 5S rDNA loci in distinct ecotypes. We suggest that both the usage of existing and new 5S rDNA loci resulting from translocations may impact neighboring chromatin organization.
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Affiliation(s)
- Lauriane Simon
- GReD, Université Clermont Auvergne, CNRS, INSERM, BP 38, 63001 Clermont-Ferrand, France
| | - Fernando A Rabanal
- Gregor Mendel Institute (GMI), Austrian Academy of Sciences, Vienna BioCenter (VBC), Dr. Bohr-Gasse 3, 1030 Vienna, Austria
| | - Tristan Dubos
- GReD, Université Clermont Auvergne, CNRS, INSERM, BP 38, 63001 Clermont-Ferrand, France
| | - Cecilia Oliver
- Departamento de Genética, Facultad de Biología, Universidad Complutense de Madrid, Madrid 28040, Spain
| | - Damien Lauber
- GReD, Université Clermont Auvergne, CNRS, INSERM, BP 38, 63001 Clermont-Ferrand, France
| | - Axel Poulet
- GReD, Université Clermont Auvergne, CNRS, INSERM, BP 38, 63001 Clermont-Ferrand, France
| | - Alexander Vogt
- Vienna Biocenter Core Facilities GmbH (VBCF), Dr. Bohr-Gasse 3, 1030 Vienna, Austria
| | - Ariane Mandlbauer
- Vienna Biocenter Core Facilities GmbH (VBCF), Dr. Bohr-Gasse 3, 1030 Vienna, Austria
| | - Samuel Le Goff
- GReD, Université Clermont Auvergne, CNRS, INSERM, BP 38, 63001 Clermont-Ferrand, France
| | - Andreas Sommer
- Vienna Biocenter Core Facilities GmbH (VBCF), Dr. Bohr-Gasse 3, 1030 Vienna, Austria
| | - Hervé Duborjal
- Plant Engineering Platform, BIOGEMMA, Route d'Ennezat Centre de Recherche de Chappes, 63720 Chappes, France
| | - Christophe Tatout
- GReD, Université Clermont Auvergne, CNRS, INSERM, BP 38, 63001 Clermont-Ferrand, France
| | - Aline V Probst
- GReD, Université Clermont Auvergne, CNRS, INSERM, BP 38, 63001 Clermont-Ferrand, France
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Samoluk SS, Chalup LMI, Chavarro C, Robledo G, Bertioli DJ, Jackson SA, Seijo G. Heterochromatin evolution in Arachis investigated through genome-wide analysis of repetitive DNA. PLANTA 2019; 249:1405-1415. [PMID: 30680457 DOI: 10.1007/s00425-019-03096-4] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/30/2018] [Accepted: 01/18/2019] [Indexed: 05/21/2023]
Abstract
The most conspicuous difference among chromosomes and genomes in Arachis species, the patterns of heterochromatin, was mainly modeled by differential amplification of different members of one superfamily of satellite DNAs. Divergence in repetitive DNA is a primary driving force for genome and chromosome evolution. Section Arachis is karyotypically diverse and has six different genomes. Arachis glandulifera (D genome) has the most asymmetric karyotype and the highest reproductive isolation compared to the well-known A and B genome species. These features make A. glandulifera an interesting model species for studying the main repetitive components that accompanied the genome and chromosome diversification in the section. Here, we performed a genome-wide analysis of repetitive sequences in A. glandulifera and investigated the chromosome distribution of the identified satellite DNA sequences (satDNAs). LTR retroelements, mainly the Ty3-gypsy families "Fidel/Feral" and "Pipoka/Pipa", were the most represented. Comparative analyses with the A and B genomes showed that many of the previously described transposable elements (TEs) were differently represented in the D genome, and that this variation accompanied changes in DNA content. In addition, four major satDNAs were characterized. Agla_CL8sat was the major component of pericentromeric heterochromatin, while Agla_CL39sat, Agla_CL69sat, and Agla_CL122sat were found in heterochromatic and/or euchromatic regions. Even though Agla_CL8sat belong to a different family than that of the major satDNA (ATR-2) found in the heterochromatin of the A, K, and F genomes, both satDNAs are members of the same superfamily. This finding suggests that closely related satDNAs of an ancestral library were differentially amplified leading to the major changes in the heterochromatin patterns that accompanied the karyotype and genome differentiation in Arachis.
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Affiliation(s)
- Sergio S Samoluk
- Facultad de Ciencias Agrarias, Instituto de Botánica del Nordeste (UNNE-CONICET), Corrientes, Argentina.
| | - Laura M I Chalup
- Facultad de Ciencias Agrarias, Instituto de Botánica del Nordeste (UNNE-CONICET), Corrientes, Argentina
| | - Carolina Chavarro
- Center for Applied Genetic Technologies, University of Georgia, Athens, GA, USA
| | - Germán Robledo
- Facultad de Ciencias Agrarias, Instituto de Botánica del Nordeste (UNNE-CONICET), Corrientes, Argentina
- Facultad de Ciencias Exactas y Naturales y Agrimensura, Universidad Nacional del Nordeste, Corrientes, Argentina
| | - David J Bertioli
- Center for Applied Genetic Technologies, University of Georgia, Athens, GA, USA
| | - Scott A Jackson
- Center for Applied Genetic Technologies, University of Georgia, Athens, GA, USA
| | - Guillermo Seijo
- Facultad de Ciencias Agrarias, Instituto de Botánica del Nordeste (UNNE-CONICET), Corrientes, Argentina
- Facultad de Ciencias Exactas y Naturales y Agrimensura, Universidad Nacional del Nordeste, Corrientes, Argentina
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15
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Ishchenko OO, Panchuk ІІ, Andreev ІO, Kunakh VA, Volkov RA. Molecular Organization of 5S Ribosomal DNА of Deschapmpsia antarctica. CYTOL GENET+ 2018. [DOI: 10.3103/s0095452718060105] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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16
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Tamayo-Ordóñez YJ, Narváez-Zapata JA, Tamayo-Ordóñez MC, Sánchez-Teyer LF. Retroelements and DNA Methylation Could Contribute to Diversity of 5S rDNA in Agave L. J Mol Evol 2018; 86:404-423. [DOI: 10.1007/s00239-018-9856-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2018] [Accepted: 07/03/2018] [Indexed: 01/21/2023]
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17
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Glugoski L, Giuliano-Caetano L, Moreira-Filho O, Vicari MR, Nogaroto V. Co-located hAT transposable element and 5S rDNA in an interstitial telomeric sequence suggest the formation of Robertsonian fusion in armored catfish. Gene 2018; 650:49-54. [DOI: 10.1016/j.gene.2018.01.099] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2017] [Revised: 01/23/2018] [Accepted: 01/31/2018] [Indexed: 01/12/2023]
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18
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Yang S, Qin X, Cheng C, Li Z, Lou Q, Li J, Chen J. Organization and evolution of four differentially amplified tandem repeats in the Cucumis hystrix genome. PLANTA 2017; 246:749-761. [PMID: 28668977 DOI: 10.1007/s00425-017-2716-6] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/26/2017] [Accepted: 05/29/2017] [Indexed: 05/18/2023]
Abstract
Three subtelomeric satellites and one interstitial 5S rDNA were characterized in Cucumis hystrix, and the pericentromeric signals of two C. hystrix subtelomeric satellites along C. sativus chromosomes supported the hypothesis of chromosome fusion in Cucumis. Tandem repeats are chromosome structural fractions consisting of highly repetitive sequences organized in large tandem arrays in most eukaryotes. Differentiation of tandem repeats directly affects the chromosome structure, which contributes to species formation and evolution. Cucumis hystrix (2n = 2x = 24) is the only wild Cucumis species grouped into the same subgenus with C. sativus (2n = 2x = 14), hence its phylogenetic position confers a vital role for C. hystrix to understand the chromosome evolution in Cucumis. However, our knowledge of C. hystrix tandem repeats is insufficient for a detailed understanding of the chromosome evolution in Cucumis. Based on de novo tandem repeat characterization using bioinformatics and in situ hybridization (ISH), we identified and characterized four differentially amplified tandem repeats, Cucumis hystrix satellite 1-3 (CuhySat1-CuhySat3) located at the subtelomeric regions of all chromosomes, and Cucumis hystrix 5S (Cuhy5S) located at the interstitial regions of one single chromosome pair. Comparative ISH mapping using CuhySat1-3 and Cuhy5S revealed high homology of tandem repeats between C. hystrix and C. sativus. Intriguingly, we found signal distribution variations of CuhySat2 and CuhySat3 on C. sativus chromosomes. In comparison to their subtelomeric signal distribution on C. hystrix chromosomes, CuhySat3 showed a pericentromeric signal distribution and CuhySat2 showed both subtelomeric and pericentromeric signal distributions on C. sativus chromosomes. This detailed characterization of four C. hystrix tandem repeats significantly widens our knowledge of the C. hystrix chromosome structure, and the observed signal distribution variations will be helpful for understanding the chromosome evolution of Cucumis.
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Affiliation(s)
- Shuqiong Yang
- State Key Lab of Crop Genetics and Germplasm Enhancement, College of Horticulture, Nanjing Agricultural University, Nanjing, 210095, China
| | - Xiaodong Qin
- State Key Lab of Crop Genetics and Germplasm Enhancement, College of Horticulture, Nanjing Agricultural University, Nanjing, 210095, China
| | - Chunyan Cheng
- State Key Lab of Crop Genetics and Germplasm Enhancement, College of Horticulture, Nanjing Agricultural University, Nanjing, 210095, China
| | - Ziang Li
- State Key Lab of Crop Genetics and Germplasm Enhancement, College of Horticulture, Nanjing Agricultural University, Nanjing, 210095, China
| | - Qunfeng Lou
- State Key Lab of Crop Genetics and Germplasm Enhancement, College of Horticulture, Nanjing Agricultural University, Nanjing, 210095, China
| | - Ji Li
- State Key Lab of Crop Genetics and Germplasm Enhancement, College of Horticulture, Nanjing Agricultural University, Nanjing, 210095, China
| | - Jinfeng Chen
- State Key Lab of Crop Genetics and Germplasm Enhancement, College of Horticulture, Nanjing Agricultural University, Nanjing, 210095, China.
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Higher-order organisation of extremely amplified, potentially functional and massively methylated 5S rDNA in European pikes (Esox sp.). BMC Genomics 2017; 18:391. [PMID: 28521734 PMCID: PMC5437419 DOI: 10.1186/s12864-017-3774-7] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2016] [Accepted: 05/09/2017] [Indexed: 12/16/2022] Open
Abstract
Background Pikes represent an important genus (Esox) harbouring a pre-duplication karyotype (2n = 2x = 50) of economically important salmonid pseudopolyploids. Here, we have characterized the 5S ribosomal RNA genes (rDNA) in Esox lucius and its closely related E. cisalpinus using cytogenetic, molecular and genomic approaches. Intragenomic homogeneity and copy number estimation was carried out using Illumina reads. The higher-order structure of rDNA arrays was investigated by the analysis of long PacBio reads. Position of loci on chromosomes was determined by FISH. DNA methylation was analysed by methylation-sensitive restriction enzymes. Results The 5S rDNA loci occupy exclusively (peri)centromeric regions on 30–38 acrocentric chromosomes in both E. lucius and E. cisalpinus. The large number of loci is accompanied by extreme amplification of genes (>20,000 copies), which is to the best of our knowledge one of the highest copy number of rRNA genes in animals ever reported. Conserved secondary structures of predicted 5S rRNAs indicate that most of the amplified genes are potentially functional. Only few SNPs were found in genic regions indicating their high homogeneity while intergenic spacers were more heterogeneous and several families were identified. Analysis of 10–30 kb-long molecules sequenced by the PacBio technology (containing about 40% of total 5S rDNA) revealed that the vast majority (96%) of genes are organised in large several kilobase-long blocks. Dispersed genes or short tandems were less common (4%). The adjacent 5S blocks were directly linked, separated by intervening DNA and even inverted. The 5S units differing in the intergenic spacers formed both homogeneous and heterogeneous (mixed) blocks indicating variable degree of homogenisation between the loci. Both E. lucius and E. cisalpinus 5S rDNA was heavily methylated at CG dinucleotides. Conclusions Extreme amplification of 5S rRNA genes in the Esox genome occurred in the absence of significant pseudogenisation suggesting its recent origin and/or intensive homogenisation processes. The dense methylation of units indicates that powerful epigenetic mechanisms have evolved in this group of fish to silence amplified genes. We discuss how the higher-order repeat structures impact on homogenisation of 5S rDNA in the genome. Electronic supplementary material The online version of this article (doi:10.1186/s12864-017-3774-7) contains supplementary material, which is available to authorized users.
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Barros AV, Wolski MAV, Nogaroto V, Almeida MC, Moreira-Filho O, Vicari MR. Fragile sites, dysfunctional telomere and chromosome fusions: What is 5S rDNA role? Gene 2017; 608:20-27. [DOI: 10.1016/j.gene.2017.01.013] [Citation(s) in RCA: 49] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2016] [Revised: 01/04/2017] [Accepted: 01/18/2017] [Indexed: 11/29/2022]
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Fujimoto S, Sugano SS, Kuwata K, Osakabe K, Matsunaga S. Visualization of specific repetitive genomic sequences with fluorescent TALEs in Arabidopsis thaliana. JOURNAL OF EXPERIMENTAL BOTANY 2016; 67:6101-6110. [PMID: 27811079 PMCID: PMC5100022 DOI: 10.1093/jxb/erw371] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Live imaging of the dynamics of nuclear organization provides the opportunity to uncover the mechanisms responsible for four-dimensional genome architecture. Here, we describe the use of fluorescent protein (FP) fusions of transcription activator-like effectors (TALEs) to visualize endogenous genomic sequences in Arabidopsis thaliana. The ability to engineer sequence-specific TALEs permits the investigation of precise genomic sequences. We could detect TALE-FP signals associated with centromeric, telomeric, and rDNA repeats and the signal distribution was consistent with that observed by fluorescent in situ hybridization. TALE-FPs are advantageous because they permit the observation of intact tissues. We used our TALE-FP method to investigate the nuclei of several multicellular plant tissues including roots, hypocotyls, leaves, and flowers. Because TALE-FPs permit live-cell imaging, we successfully observed the temporal dynamics of centromeres and telomeres in plant organs. Fusing TALEs to multimeric FPs enhanced the signal intensity when observing telomeres. We found that the mobility of telomeres was different in sub-nuclear regions. Transgenic plants stably expressing TALE-FPs will provide new insights into chromatin organization and dynamics in multicellular organisms.
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Affiliation(s)
- Satoru Fujimoto
- Department of Applied Biological Science, Faculty of Science and Technology, Tokyo University of Science, Noda, Chiba 278-8510, Japan
| | - Shigeo S Sugano
- Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan
- PRESTO, JST, Saitama 332-0012, Japan
| | - Keiko Kuwata
- Institute of Transformative Bio-Molecules, Nagoya University, Nagoya 464-8601, Japan
| | - Keishi Osakabe
- Faculty of Bioscience and Bioindustry, Tokushima University, Tokushima 770-8513, Japan
| | - Sachihiro Matsunaga
- Department of Applied Biological Science, Faculty of Science and Technology, Tokyo University of Science, Noda, Chiba 278-8510, Japan
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Simon L, Voisin M, Tatout C, Probst AV. Structure and Function of Centromeric and Pericentromeric Heterochromatin in Arabidopsis thaliana. FRONTIERS IN PLANT SCIENCE 2015; 6:1049. [PMID: 26648952 PMCID: PMC4663263 DOI: 10.3389/fpls.2015.01049] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/29/2015] [Accepted: 11/09/2015] [Indexed: 05/23/2023]
Abstract
The centromere is a specific chromosomal region where the kinetochore assembles to ensure the faithful segregation of sister chromatids during mitosis and meiosis. Centromeres are defined by a local enrichment of the specific histone variant CenH3 mostly at repetitive satellite sequences. A larger pericentromeric region containing repetitive sequences and transposable elements surrounds the centromere that adopts a particular chromatin state characterized by specific histone variants and post-translational modifications and forms a transcriptionally repressive chromosomal environment. In the model organism Arabidopsis thaliana centromeric and pericentromeric domains form conspicuous heterochromatin clusters called chromocenters in interphase. Here we discuss, using Arabidopsis as example, recent insight into mechanisms involved in maintenance and establishment of centromeric and pericentromeric chromatin signatures as well as in chromocenter formation.
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Affiliation(s)
| | - Maxime Voisin
- †These authors have contributed equally to this work.
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Heitkam T, Petrasch S, Zakrzewski F, Kögler A, Wenke T, Wanke S, Schmidt T. Next-generation sequencing reveals differentially amplified tandem repeats as a major genome component of Northern Europe’s oldest Camellia japonica. Chromosome Res 2015; 23:791-806. [DOI: 10.1007/s10577-015-9500-x] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2015] [Revised: 10/20/2015] [Accepted: 10/22/2015] [Indexed: 11/30/2022]
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O'Sullivan JM, Pai DA, Cridge AG, Engelke DR, Ganley ARD. The nucleolus: a raft adrift in the nuclear sea or the keystone in nuclear structure? Biomol Concepts 2015; 4:277-86. [PMID: 25436580 DOI: 10.1515/bmc-2012-0043] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2012] [Accepted: 12/21/2012] [Indexed: 11/15/2022] Open
Abstract
The nucleolus is a prominent nuclear structure that is the site of ribosomal RNA (rRNA) transcription, and hence ribosome biogenesis. Cellular demand for ribosomes, and hence rRNA, is tightly linked to cell growth and the rRNA makes up the majority of all the RNA within a cell. To fulfill the cellular demand for rRNA, the ribosomal RNA (rDNA) genes are amplified to high copy number and transcribed at very high rates. As such, understanding the rDNA has profound consequences for our comprehension of genome and transcriptional organization in cells. In this review, we address the question of whether the nucleolus is a raft adrift the sea of nuclear DNA, or actively contributes to genome organization. We present evidence supporting the idea that the nucleolus, and the rDNA contained therein, play more roles in the biology of the cell than simply ribosome biogenesis. We propose that the nucleolus and the rDNA are central factors in the spatial organization of the genome, and that rapid alterations in nucleolar structure in response to changing conditions manifest themselves in altered genomic structures that have functional consequences. Finally, we discuss some predictions that result from the nucleolus having a central role in nuclear organization.
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Galián JA, Rosato M, Rosselló JA. Partial Sequence Homogenization in the 5S Multigene Families May Generate Sequence Chimeras and Spurious Results in Phylogenetic Reconstructions. Syst Biol 2014; 63:219-30. [DOI: 10.1093/sysbio/syt101] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Affiliation(s)
- José A. Galián
- Jardín Botánico, Universidad de Valencia, c/Quart 80, E-46008 Valencia, Spain; and 2Marimurtra Bot. Garden, Carl Faust Fdn., PO Box 112, E-17300 Blanes, Catalonia, Spain
| | - Marcela Rosato
- Jardín Botánico, Universidad de Valencia, c/Quart 80, E-46008 Valencia, Spain; and 2Marimurtra Bot. Garden, Carl Faust Fdn., PO Box 112, E-17300 Blanes, Catalonia, Spain
| | - Josep A. Rosselló
- Jardín Botánico, Universidad de Valencia, c/Quart 80, E-46008 Valencia, Spain; and 2Marimurtra Bot. Garden, Carl Faust Fdn., PO Box 112, E-17300 Blanes, Catalonia, Spain
- Jardín Botánico, Universidad de Valencia, c/Quart 80, E-46008 Valencia, Spain; and 2Marimurtra Bot. Garden, Carl Faust Fdn., PO Box 112, E-17300 Blanes, Catalonia, Spain
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Bellavia D, Dimarco E, Naselli F, Caradonna F. DNA-methylation dependent regulation of embryo-specific 5S ribosomal DNA cluster transcription in adult tissues of sea urchin Paracentrotus lividus. Genomics 2013; 102:397-402. [PMID: 23933480 DOI: 10.1016/j.ygeno.2013.08.001] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2013] [Revised: 07/25/2013] [Accepted: 08/01/2013] [Indexed: 11/26/2022]
Abstract
We have previously reported a molecular and cytogenetic characterization of three different 5S rDNA clusters in the sea urchin Paracentrotus lividus and recently, demonstrated the presence of high heterogeneity in functional 5S rRNA. In this paper, we show some important distinctive data on 5S rRNA transcription for this organism. Using single strand conformation polymorphism (SSCP) analysis, we demonstrate the existence of two classes of 5S rRNA, one which is embryo-specific and encoded by the smallest (700 bp) cluster and the other which is expressed at every stage and encoded by longer clusters (900 and 950 bp). We also demonstrate that the embryo-specific class of 5S rRNA is expressed in oocytes and embryonic stages and is silenced in adult tissue and that this phenomenon appears to be due exclusively to DNA methylation, as indicated by sensitivity to 5-azacytidine, unlike Xenopus where this mechanism is necessary but not sufficient to maintain the silenced status.
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Affiliation(s)
- Daniele Bellavia
- Dipartimento di Scienze e Tecnologie Biologiche Chimiche e Farmaceutiche (STEBICEF), Sezione di Biologia Cellulare, Ed. 16, Università degli Studi di Palermo, V.le delle Scienze, 90128 Palermo, Italy; Istituto Ortopedico Rizzoli, c/o Dipartimento di Biopatologia e Biotecnologie Mediche e Forensi (DIBIMEF), Università degli Studi di Palermo, Via Divisi 81, 90133 Palermo, Italy.
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Structure, function and regulation of Transcription Factor IIIA: From Xenopus to Arabidopsis. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2013; 1829:274-82. [DOI: 10.1016/j.bbagrm.2012.10.013] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/24/2012] [Revised: 10/30/2012] [Accepted: 10/31/2012] [Indexed: 12/14/2022]
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Dimarco E, Cascone E, Bellavia D, Caradonna F. Functional variants of 5S rRNA in the ribosomes of common sea urchin Paracentrotus lividus. Gene 2012; 508:21-5. [PMID: 22967708 DOI: 10.1016/j.gene.2012.07.067] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2012] [Accepted: 07/30/2012] [Indexed: 11/28/2022]
Abstract
We have previously reported a molecular and cytogenetic characterization of three different 5S rDNA clusters in the sea urchin Paracentrotus lividus; this study, performed at DNA level only, lends itself as starting point to verify that these clusters could contain transcribed genes, then, to demonstrate the presence of heterogeneity at functional RNA level, also. In the present work we report in P. lividus ribosomes the existence of several transcribed variants of the 5S rRNA and we associate all transcribed variants to the cluster to which belong. Our finding is the first demonstration of the presence of high heterogeneity in functional 5S rRNA molecules in animal ribosomes, a feature that had been considered a peculiarity of some plants.
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Affiliation(s)
- Eufrosina Dimarco
- Dipartimento di Scienze e Tecnologie Molecolari e Biomolecolari (STEMBIO), Sezione di Biologia Cellulare, Università degli Studi di Palermo, V.le delle Scienze—90128 Palermo, Italy
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Layat E, Sáez-Vásquez J, Tourmente S. Regulation of Pol I-transcribed 45S rDNA and Pol III-transcribed 5S rDNA in Arabidopsis. PLANT & CELL PHYSIOLOGY 2012; 53:267-76. [PMID: 22173098 DOI: 10.1093/pcp/pcr177] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
The 18S, 5.8S and 25S rRNAs, which result from the 45S precursor, together with 5S rRNAs, are central components of the ribosome. The integration of one molecule of each rRNA per ribosome necessitates an elaborate coordination between transcriptions of the two ribosomal DNA (rDNA) families. Even though 5S rDNA is transcribed by RNA polymerase III and 45S rDNA by RNA polymerase I, the two rDNA families present certain similarities in their transcriptional regulation. This review aims to compare 5S and 45S rRNA genes in the plant model Arabidopsis thaliana in terms of organization, transcription and regulation, and draws parallels between the two rDNA families.
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Affiliation(s)
- Elodie Layat
- CNRS, UMR 6247 GReD, Clermont Université, INSERM U931, Aubière, France
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31
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Fernández-Tajes J, Méndez J. Two different size classes of 5S rDNA units coexisting in the same tandem array in the razor clam Ensis macha: is this region suitable for phylogeographic studies? Biochem Genet 2011; 47:775-88. [PMID: 19633947 DOI: 10.1007/s10528-009-9276-9] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2008] [Accepted: 01/05/2009] [Indexed: 11/29/2022]
Abstract
For a study of 5S ribosomal genes (rDNA) in the razor clam Ensis macha, the 5S rDNA region was amplified and sequenced. Two variants, so-called type I or short repeat (approximately 430 bp) and type II or long repeat (approximately 735 bp), appeared to be the main components of the 5S rDNA of this species. Their spacers differed markedly, both in length and nucleotide composition. The organization of the two variants was investigated by amplifying the genomic DNA with primers based on the sequence of the type I and type II spacers. PCR amplification products with primers EMLbF and EMSbR showed that the long and short repeats are associated within the same tandem array, suggesting an intermixed arrangement of both spacers. Nevertheless, amplifications carried out with inverse primers EMSinvF/R and EMLinvF/R revealed that some short and long repeats are contiguous in the same tandem array. This is the first report of the coexistence of two variable spacers in the same tandem array in bivalve mollusks.
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Affiliation(s)
- Juan Fernández-Tajes
- Department of Cell and Molecular Biology, Faculty of Sciences, University of A Coruña, Spain.
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Wicke S, Costa A, Muñoz J, Quandt D. Restless 5S: the re-arrangement(s) and evolution of the nuclear ribosomal DNA in land plants. Mol Phylogenet Evol 2011; 61:321-32. [PMID: 21757016 DOI: 10.1016/j.ympev.2011.06.023] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2010] [Revised: 06/23/2011] [Accepted: 06/27/2011] [Indexed: 01/16/2023]
Abstract
Among eukaryotes two types of nuclear ribosomal DNA (nrDNA) organization have been observed. Either all components, i.e. the small ribosomal subunit, 5.8S, large ribosomal subunit, and 5S occur tandemly arranged or the 5S rDNA forms a separate cluster of its own. Generalizations based on data derived from just a few model organisms have led to a superimposition of structural and evolutionary traits to the entire plant kingdom asserting that plants generally possess separate arrays. This study reveals that plant nrDNA organization into separate arrays is not a distinctive feature, but rather assignable almost solely to seed plants. We show that early diverging land plants and presumably streptophyte algae share a co-localization of all rRNA genes within one repeat unit. This raises the possibility that the state of rDNA gene co-localization had occurred in their common ancestor. Separate rDNA arrays were identified for all basal seed plants and water ferns, implying at least two independent 5S rDNA transposition events during land plant evolution. Screening for 5S derived Cassandra transposable elements which might have played a role during the transposition events, indicated that this retrotransposon is absent in early diverging vascular plants including early fern lineages. Thus, Cassandra can be rejected as a primary mechanism for 5S rDNA transposition in water ferns. However, the evolution of Cassandra and other eukaryotic 5S derived elements might have been a side effect of the 5S rDNA cluster formation. Structural analysis of the intergenic spacers of the ribosomal clusters revealed that transposition events partially affect spacer regions and suggests a slightly different transcription regulation of 5S rDNA in early land plants. 5S rDNA upstream regulatory elements are highly divergent or absent from the LSU-5S spacers of most early divergent land plant lineages. Several putative scenarios and mechanisms involved in the concerted relocation of hundreds of 5S rRNA gene copies are discussed.
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Affiliation(s)
- Susann Wicke
- Institute for Evolution and Biodiversity, University of Muenster, Huefferstr. 1, D-48149 Muenster, Germany.
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Sultana S, Bang JW, Choi HW. Organization of the 5S rRNA gene units in Korean Lilium species. Genes Genomics 2011. [DOI: 10.1007/s13258-010-0131-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Zhang ZW, Yuan S, Xu F, Yang H, Chen YE, Yuan M, Xu MY, Xue LW, Xu XC, Lin HH. Mg-protoporphyrin, haem and sugar signals double cellular total RNA against herbicide and high-light-derived oxidative stress. PLANT, CELL & ENVIRONMENT 2011; 34:1031-1042. [PMID: 21388419 DOI: 10.1111/j.1365-3040.2011.02302.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Cellular total RNA level is usually stable, although it may increase gradually during growth or seed germination, or decrease gradually under environmental stresses. However, we found that plant cell RNA could be doubled within 48 h in response to herbicide-induced Mg-protoporphyrin and heme accumulation or a high level of sugar treatment. This rapid RNA multiplication is important for effective cellular resistance to oxidative stress, such as high-light and herbicide co-stress conditions, where the plastid-signalling defective mutant gun1 shows an apparent phenotype (more severe photobleaching). Hexokinase is required for sugar-induced RNA multiplication. While both sugar and Mg-protoporphyrin IX require plastid protein GUN1 and a nuclear transcription factor ABI4, haem appears to function through an independent pathway to control RNA multiplication. The transcription co-factor CAAT binding protein mediates the rapid RNA multiplication in plant cells in all the cases.
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Affiliation(s)
- Zhong-Wei Zhang
- Ministry of Education Key Laboratory for Bio-Resource and Eco-Environment, College of Life Science, Sichuan University, Chengdu 610064, China
| | - Shu Yuan
- Ministry of Education Key Laboratory for Bio-Resource and Eco-Environment, College of Life Science, Sichuan University, Chengdu 610064, China
| | - Fei Xu
- Ministry of Education Key Laboratory for Bio-Resource and Eco-Environment, College of Life Science, Sichuan University, Chengdu 610064, China
| | - Hui Yang
- Ministry of Education Key Laboratory for Bio-Resource and Eco-Environment, College of Life Science, Sichuan University, Chengdu 610064, China
| | - Yang-Er Chen
- Ministry of Education Key Laboratory for Bio-Resource and Eco-Environment, College of Life Science, Sichuan University, Chengdu 610064, China
| | - Ming Yuan
- Ministry of Education Key Laboratory for Bio-Resource and Eco-Environment, College of Life Science, Sichuan University, Chengdu 610064, China
| | - Mo-Yun Xu
- Ministry of Education Key Laboratory for Bio-Resource and Eco-Environment, College of Life Science, Sichuan University, Chengdu 610064, China
| | - Li-Wei Xue
- Ministry of Education Key Laboratory for Bio-Resource and Eco-Environment, College of Life Science, Sichuan University, Chengdu 610064, China
| | - Xiao-Chao Xu
- Ministry of Education Key Laboratory for Bio-Resource and Eco-Environment, College of Life Science, Sichuan University, Chengdu 610064, China
| | - Hong-Hui Lin
- Ministry of Education Key Laboratory for Bio-Resource and Eco-Environment, College of Life Science, Sichuan University, Chengdu 610064, China
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Douet J, Tutois S, Tourmente S. A Pol V-mediated silencing, independent of RNA-directed DNA methylation, applies to 5S rDNA. PLoS Genet 2009; 5:e1000690. [PMID: 19834541 PMCID: PMC2754527 DOI: 10.1371/journal.pgen.1000690] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2009] [Accepted: 09/17/2009] [Indexed: 12/30/2022] Open
Abstract
The plant-specific RNA polymerases Pol IV and Pol V are essential to RNA–directed DNA methylation (RdDM), which also requires activities from RDR2 (RNA–Dependent RNA Polymerase 2), DCL3 (Dicer-Like 3), AGO4 (Argonaute), and DRM2 (Domains Rearranged Methyltransferase 2). RdDM is dedicated to the methylation of target sequences which include transposable elements, regulatory regions of several protein-coding genes, and 5S rRNA–encoding DNA (rDNA) arrays. In this paper, we have studied the expression of the 5S-210 transcript, a marker of silencing release at 5S RNA genes, to show a differential impact of RNA polymerases IV and V on 5S rDNA arrays during early development of the plant. Using a combination of molecular and cytological assays, we show that Pol IV, RDR2, DRM2, and Pol V, actors of the RdDM, are required to maintain a transcriptional silencing of 5S RNA genes at chromosomes 4 and 5. Moreover, we have shown a derepression associated to chromatin decondensation specific to the 5S array from chromosome 4 and restricted to the Pol V–loss of function. In conclusion, our results highlight a new role for Pol V on 5S rDNA, which is RdDM–independent and comes specifically at chromosome 4, in addition to the RdDM pathway. In plant genomes, the RNA–directed DNA methylation (RdDM) process induces de novo methylation of cytosines at repeated sequences. The RNA polymerases Pol IV and Pol V are two key components of the RdDM pathway. Pol IV acts with RDR2 (RNA–dependent RNA polymerase 2) and DCL3 (Dicer-Like protein 3) to generate short interfering RNAs (siRNAs). Pol V, in a partnership including AGO4 (Argonaute4) and DRM2 (Domains Rearranged Methyltransferase 2), drives DNA methylation at the targeted sequence. Changes in 5S (ribosomal DNA) rDNA methylation, 5S rDNA chromatin compaction, and 5S siRNA accumulation in Pol IV/V mutants have been reported. However, 5S rDNA arrays were considered together. In the present study, we observed an overexpression of the atypic 5S-210 transcript, restricted to the 5S rDNA array from chomosome 4. This derepression is specific to the Pol V–loss of function (and not to Pol IV) and comes in addition to the RdDM pathway. The Pol V–loss of function induces also the chromatin decondensation of the derepressed 5S locus at chomosome 4. Our results highlight a new role for Pol V which, suprisingly, appears to be Pol IV– and RdDM–independent.
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Affiliation(s)
- Julien Douet
- CNRS, UMR 6247 GReD, Clermont Université, INSERM U931, Aubière, France
| | - Sylvie Tutois
- CNRS, UMR 6247 GReD, Clermont Université, INSERM U931, Aubière, France
| | - Sylvette Tourmente
- CNRS, UMR 6247 GReD, Clermont Université, INSERM U931, Aubière, France
- * E-mail:
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Blevins T, Pontes O, Pikaard CS, Meins F. Heterochromatic siRNAs and DDM1 independently silence aberrant 5S rDNA transcripts in Arabidopsis. PLoS One 2009; 4:e5932. [PMID: 19529764 PMCID: PMC2691480 DOI: 10.1371/journal.pone.0005932] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2009] [Accepted: 05/11/2009] [Indexed: 12/22/2022] Open
Abstract
5S ribosomal RNA gene repeats are arranged in heterochromatic arrays (5S rDNA) situated near the centromeres of Arabidopsis chromosomes. The chromatin remodeling factor DDM1 is known to maintain 5S rDNA methylation patterns while silencing transcription through 5S rDNA intergenic spacers (IGS). We mapped small-interfering RNAs (siRNA) to a composite 5S rDNA repeat, revealing a high density of siRNAs matching silenced IGS transcripts. IGS transcript repression requires proteins of the heterochromatic siRNA pathway, including RNA polymerase IV (Pol IV), RNA-DEPENDENT RNA POLYMERASE 2 (RDR2) and DICER-LIKE 3 (DCL3). Using molecular and cytogenetic approaches, we show that the DDM1 and siRNA-dependent silencing effects are genetically independent. DDM1 suppresses production of the siRNAs, however, thereby limiting RNA-directed DNA methylation at 5S rDNA repeats. We conclude that DDM1 and siRNA-dependent silencing are overlapping processes that both repress aberrant 5S rDNA transcription and contribute to the heterochromatic state of 5S rDNA arrays.
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MESH Headings
- Arabidopsis/metabolism
- Arabidopsis Proteins/metabolism
- Chromatin/chemistry
- Computational Biology/methods
- Crosses, Genetic
- DNA, Intergenic
- DNA, Ribosomal/metabolism
- DNA-Binding Proteins/metabolism
- Gene Silencing
- Genes, Plant
- In Situ Hybridization, Fluorescence
- Models, Biological
- RNA, Ribosomal, 5S/metabolism
- RNA, Small Interfering/metabolism
- Transcription Factors/metabolism
- Transcription, Genetic
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Affiliation(s)
- Todd Blevins
- Friedrich Miescher Institute for Biomedical Research, Basel, Switzerland
| | - Olga Pontes
- Department of Biology, Washington University in St. Louis, St. Louis, Missouri, United States of America
| | - Craig S. Pikaard
- Department of Biology, Washington University in St. Louis, St. Louis, Missouri, United States of America
| | - Frederick Meins
- Friedrich Miescher Institute for Biomedical Research, Basel, Switzerland
- * E-mail:
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Abstract
We report a group of TRIMs (terminal-repeat retrotransposons in miniature), which are small nonautonomous retrotransposons. These elements, named Cassandra, universally carry conserved 5S RNA sequences and associated RNA polymerase (pol) III promoters and terminators in their long terminal repeats (LTRs). They were found in all vascular plants investigated. Uniquely for LTR retrotransposons, Cassandra produces noncapped, polyadenylated transcripts from the 5S pol III promoter. Capped, read-through transcripts containing Cassandra sequences can also be detected in RNA and in EST databases. The predicted Cassandra RNA 5S secondary structures resemble those for cellular 5S rRNA, with high information content specifically in the pol III promoter region. Genic integration sites are common for Cassandra, an unusual feature for abundant retrotransposons. The 5S in each LTR produces a tandem 5S arrangement with an inter-5S spacing resembling that of cellular 5S. The distribution of 5S genes is very variable in flowering plants and may be partially explained by Cassandra activity. Cassandra thus appears both to have adapted a ubiquitous cellular gene for ribosomal RNA for use as a promoter and to parasitize an as-yet-unidentified group of retrotransposons for the proteins needed in its lifecycle.
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Fulnecek J, Kovarik A. Low abundant spacer 5S rRNA transcripts are frequently polyadenylated in Nicotiana. Mol Genet Genomics 2007; 278:565-73. [PMID: 17671796 DOI: 10.1007/s00438-007-0273-6] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2007] [Revised: 06/22/2007] [Accepted: 06/27/2007] [Indexed: 10/23/2022]
Abstract
In plants, 5S rRNA genes (5S rDNA) encoding 120-nt structural RNA molecules of ribosomes are organized in tandem arrays comprising thousands of units. Failure to correctly terminate transcription would generate longer inaccurately processed transcripts interfering with ribosome biogenesis. Hence multiple termination signals occur immediately after the 5S rRNA coding sequence. To obtain information about the efficiency of termination of 5S rDNA transcription in plants we analyzed 5S rRNA pools in three Nicotiana species, N. sylvestris, N. tomentosiformis and N. tabacum. In addition to highly abundant 120-nt 5S rRNA transcripts, we also detected RNA species composed of a genic region and variable lengths of intergenic sequences. These genic-intergenic RNA molecules occur at a frequency severalfold lower than the mature 120-nt transcripts, and are posttranscriptionally modified by polyadenylation at their 3' end in contrast to 120-nt transcripts. An absence of 5S small RNAs (smRNA) argue against a dominant role for the smRNA biosynthesis pathway in the degradation of aberrant 5S rRNA in Nicotiana. This work is the first description of polyadenylated 5S rRNA species in higher eukaryotes originating from a read-through transcription into the intergenic spacer. We propose that polyadenylation may function in a "quality control" pathway ensuring that only correctly processed molecules enter the ribosome biogenesis.
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Affiliation(s)
- Jaroslav Fulnecek
- Institute of Biophysics, Academy of Sciences of the Czech Republic v.v.i, Kralovopolska 135, 612 65, Brno, Czech Republic.
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40
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Falistocco E, Passeri V, Marconi G. Investigations of 5S rDNA of Vitis vinifera L.: sequence analysis and physical mapping. Genome 2007; 50:927-38. [DOI: 10.1139/g07-070] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Here we report the first results of a study of 5S rDNA of Vitis vinifera . 5S rDNA sequences from seven genotypes were amplified by PCR, cloned, and sequenced. Three types of repeats were found. Two variants, denominated long repeat and short repeat, appeared to be the main components of the 5S rDNA of this species, since they were found in all genotypes analyzed. They differed markedly from each other in both the length and the nucleotide composition of the spacers. The third variant, classified as DEL short repeat, differs from the short repeat owing to a large deletion in the spacer region. It appears to be the most recent repeat type, since it was identified in only one genotype. The organization of the 5S rDNA repeat unit variants was investigated by amplifying the genomic DNA with primers designed on the sequence of the long and short spacers. The PCR-amplified fragments showed that the long repeat is associated with the other two repeats, indicating that in V. vinifera different repeat units coexist within the same tandem array. FISH analysis demonstrated that 5S rRNA genes are localized at a single locus. The variability of 5S rDNA repeats is discussed in relation to the putative allopolyploid origin of V. vinifera.
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Affiliation(s)
- E. Falistocco
- Dipartimento di Biologia Vegetale e Biotecnologie Agroambientali e Zootecniche, Università degli Studi di Perugia, Borgo XX Giugno, 06121 Perugia, Italy
| | - V. Passeri
- Dipartimento di Biologia Vegetale e Biotecnologie Agroambientali e Zootecniche, Università degli Studi di Perugia, Borgo XX Giugno, 06121 Perugia, Italy
| | - G. Marconi
- Dipartimento di Biologia Vegetale e Biotecnologie Agroambientali e Zootecniche, Università degli Studi di Perugia, Borgo XX Giugno, 06121 Perugia, Italy
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Lindhout BI, Fransz P, Tessadori F, Meckel T, Hooykaas PJ, van der Zaal BJ. Live cell imaging of repetitive DNA sequences via GFP-tagged polydactyl zinc finger proteins. Nucleic Acids Res 2007; 35:e107. [PMID: 17704126 PMCID: PMC2018617 DOI: 10.1093/nar/gkm618] [Citation(s) in RCA: 87] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
Several techniques are available to study chromosomes or chromosomal domains in nuclei of chemically fixed or living cells. Current methods to detect DNA sequences in vivo are limited to trans interactions between a DNA sequence and a transcription factor from natural systems. Here, we expand live cell imaging tools using a novel approach based on zinc finger-DNA recognition codes. We constructed several polydactyl zinc finger (PZF) DNA-binding domains aimed to recognize specific DNA sequences in Arabidopsis and mouse and fused these with GFP. Plants and mouse cells expressing PZF:GFP proteins were subsequently analyzed by confocal microscopy. For Arabidopsis, we designed a PZF:GFP protein aimed to specifically recognize a 9-bp sequence within centromeric 180-bp repeat and monitored centromeres in living roots. Similarly, in mouse cells a PZF:GFP protein was targeted to a 9-bp sequence in the major satellite repeat. Both PZF:GFP proteins localized in chromocenters which represent heterochromatin domains containing centromere and other tandem repeats. The number of PZF:GFP molecules per centromere in Arabidopsis, quantified with near single-molecule precision, approximated the number of expected binding sites. Our data demonstrate that live cell imaging of specific DNA sequences can be achieved with artificial zinc finger proteins in different organisms.
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Affiliation(s)
- Beatrice I. Lindhout
- Institute of Biology Leiden, Department of Molecular and Developmental Genetics, Clusius Laboratory, Leiden University, Wassenaarseweg 64, 2333 AL, Leiden, Swammerdam Institute for Life Sciences, University of Amsterdam, 1098 SM, Amsterdam and Physics of Life Processes, Leiden Institute of Physics, Leiden University, Niels Bohrweg 2, 2333 CA, Leiden, The Netherlands
| | - Paul Fransz
- Institute of Biology Leiden, Department of Molecular and Developmental Genetics, Clusius Laboratory, Leiden University, Wassenaarseweg 64, 2333 AL, Leiden, Swammerdam Institute for Life Sciences, University of Amsterdam, 1098 SM, Amsterdam and Physics of Life Processes, Leiden Institute of Physics, Leiden University, Niels Bohrweg 2, 2333 CA, Leiden, The Netherlands
| | - Federico Tessadori
- Institute of Biology Leiden, Department of Molecular and Developmental Genetics, Clusius Laboratory, Leiden University, Wassenaarseweg 64, 2333 AL, Leiden, Swammerdam Institute for Life Sciences, University of Amsterdam, 1098 SM, Amsterdam and Physics of Life Processes, Leiden Institute of Physics, Leiden University, Niels Bohrweg 2, 2333 CA, Leiden, The Netherlands
| | - Tobias Meckel
- Institute of Biology Leiden, Department of Molecular and Developmental Genetics, Clusius Laboratory, Leiden University, Wassenaarseweg 64, 2333 AL, Leiden, Swammerdam Institute for Life Sciences, University of Amsterdam, 1098 SM, Amsterdam and Physics of Life Processes, Leiden Institute of Physics, Leiden University, Niels Bohrweg 2, 2333 CA, Leiden, The Netherlands
| | - Paul J.J. Hooykaas
- Institute of Biology Leiden, Department of Molecular and Developmental Genetics, Clusius Laboratory, Leiden University, Wassenaarseweg 64, 2333 AL, Leiden, Swammerdam Institute for Life Sciences, University of Amsterdam, 1098 SM, Amsterdam and Physics of Life Processes, Leiden Institute of Physics, Leiden University, Niels Bohrweg 2, 2333 CA, Leiden, The Netherlands
| | - Bert J. van der Zaal
- Institute of Biology Leiden, Department of Molecular and Developmental Genetics, Clusius Laboratory, Leiden University, Wassenaarseweg 64, 2333 AL, Leiden, Swammerdam Institute for Life Sciences, University of Amsterdam, 1098 SM, Amsterdam and Physics of Life Processes, Leiden Institute of Physics, Leiden University, Niels Bohrweg 2, 2333 CA, Leiden, The Netherlands
- *To whom correspondence should be addressed. +31 71 527 4760+31 71 527 4999
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42
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Davison J, Tyagi A, Comai L. Large-scale polymorphism of heterochromatic repeats in the DNA of Arabidopsis thaliana. BMC PLANT BIOLOGY 2007; 7:44. [PMID: 17705842 PMCID: PMC2000876 DOI: 10.1186/1471-2229-7-44] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/17/2007] [Accepted: 08/16/2007] [Indexed: 05/16/2023]
Abstract
BACKGROUND The composition of the individual eukaryote's genome and its variation within a species remain poorly defined. Even for a sequenced genome such as that of the model plant Arabidopsis thaliana accession Col-0, the large arrays of heterochromatic repeats are incompletely sequenced, with gaps of uncertain size persisting in them. RESULTS Using geographically separate populations of A. thaliana, we assayed variation in the heterochromatic repeat arrays using two independent methods and identified significant polymorphism among them, with variation by as much as a factor of two in the centromeric 180 bp repeat, in the 45S rDNA arrays and in the Athila retroelements. In the accession with highest genome size as measured by flow cytometry, Loh-0, we found more than a two-fold increase in 5S RNA gene copies relative to Col-0; results from fluorescence in situ hybridization with 5S probes were consistent with the existence of size polymorphism between Loh-0 and Col-0 at the 5S loci. Comparative genomic hybridization results of Loh-0 and Col-0 did not support contiguous variation in copy number of protein-coding genes on the scale needed to explain their observed genome size difference. We developed a computational data model to test whether the variation we measured in the repeat fractions could account for the different genome sizes determined with flow cytometry, and found that this proposed relationship could account for about 50% of the variance in genome size among the accessions. CONCLUSION Our analyses are consistent with substantial repeat number polymorphism for 5S and 45S ribosomal genes among accession of A. thaliana. Differences are also suggested for centromeric and pericentromeric repeats. Our analysis also points to the difficulties in measuring the repeated fraction of the genome and suggests that independent validation of genome size should be sought in addition to flow cytometric measurements.
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Affiliation(s)
- Jerry Davison
- University of Washington, Department of Biology, Box 355325, Seattle, WA 98195-5325, USA
| | - Anand Tyagi
- University of the South Pacific, School of Pure and Applied Sciences, Department of Biology, PO Box 1168, Suva, Fiji
| | - Luca Comai
- University of California at Davis, Section of Plant Biology and the UC Davis Genome Center,451 E. Health Sciences Drive, Davis, CA 95616, USA
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Tessadori F, Chupeau MC, Chupeau Y, Knip M, Germann S, van Driel R, Fransz P, Gaudin V. Large-scale dissociation and sequential reassembly of pericentric heterochromatin in dedifferentiated Arabidopsis cells. J Cell Sci 2007; 120:1200-8. [PMID: 17376962 DOI: 10.1242/jcs.000026] [Citation(s) in RCA: 115] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Chromocenters in Arabidopsis thaliana are discrete nuclear domains of mainly pericentric heterochromatin. They are characterized by the presence of repetitive sequences, methylated DNA and dimethylated histone H3K9. Here we show that dedifferentiation of specialized mesophyll cells into undifferentiated protoplasts is accompanied by the disruption of chromocenter structures. The dramatic reduction of heterochromatin involves the decondensation of all major repeat regions, also including the centromeric 180 bp tandem repeats. Only the 45S rDNA repeat remained in a partly compact state in most cells. Remarkably, the epigenetic indicators for heterochromatin, DNA methylation and H3K9 dimethylation, did not change upon decondensation. Furthermore, the decondensation of pericentric heterochromatin did not result in transcriptional reactivation of silent genomic elements. The decondensation process was reversible upon prolonged culturing. Strikingly, recondensation of heterochromatin into chromocenters is a stepwise process. Compaction of the tandemly arranged 45S rDNA regions occurs first, followed by the centromeric 180 bp and the 5S rDNA repeats and finally the dispersed repeats, including transposons. The sequence of reassembly seems to be correlated to the size of the repeat domains. Our results indicate that different types of pericentromeric repeats form different types of heterochromatin, which subsequently merge to form a chromocenter.
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Affiliation(s)
- Federico Tessadori
- Nuclear Organization Group, Swammerdam Institute for Life Sciences, University of Amsterdam, BioCentrum Amsterdam, Kruislaan 318, 1098SM Amsterdam, The Netherlands
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Berr A, Schubert I. Interphase chromosome arrangement in Arabidopsis thaliana is similar in differentiated and meristematic tissues and shows a transient mirror symmetry after nuclear division. Genetics 2007; 176:853-63. [PMID: 17409060 PMCID: PMC1894613 DOI: 10.1534/genetics.107.073270] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2007] [Accepted: 03/15/2007] [Indexed: 12/21/2022] Open
Abstract
Whole-mount fluorescence in situ hybridization (FISH) was applied to Arabidopsis thaliana seedlings to determine the three-dimensional (3D) interphase chromosome territory (CT) arrangement and heterochromatin location within the positional context of entire tissues or in particular cell types of morphologically well-preserved seedlings. The interphase chromosome arrangement was found to be similar between all inspected meristematic and differentiated root and shoot cells, indicating a lack of a gross reorganization during differentiation. The predominantly random CT arrangement (except for a more frequent association of the homologous chromosomes bearing a nucleolus organizer) and the peripheric location of centromeric heterochromatin were as previously observed for flow-sorted nuclei, but centromeres tend to fuse more often in nonendoreduplicating cells and NORs in differentiated cells. After mitosis, sister nuclei revealed a symmetric arrangement of homologous CTs waning with the progress of the cell cycle or in the course of differentiation. Thus, the interphase chromosome arrangement in A. thaliana nuclei seems to be constrained mainly by morphological features such as nuclear shape, presence or absence of a nucleolus organizer on chromosomes, nucleolar volume, and/or endopolyploidy level.
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Affiliation(s)
| | - Ingo Schubert
- Leibniz-Institute of Plant Genetics and Crop Plant Research (IPK), D-06466 Gatersleben, Germany
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Douet J, Tourmente S. Transcription of the 5S rRNA heterochromatic genes is epigenetically controlled in Arabidopsis thaliana and Xenopus laevis. Heredity (Edinb) 2007; 99:5-13. [PMID: 17487217 DOI: 10.1038/sj.hdy.6800964] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
5S ribosomal DNA is a highly conserved tandemly repeated multigenic family. As suggested for a long time, we have shown that only a fraction of the 5S rRNA genes are expressed in Arabidopsis thaliana. In Xenopus laevis, there is a developmental control of the expression of the 5S rRNA genes with only one of the two 5S rDNA families expressed during oogenesis. For both Arabidopsis and Xenopus, the strongest transcription of 5S rRNA, respectively in the seed and during oogenesis is correlated with heterogeneity in the transcribed 5S rRNAs. Epigenetic mechanisms such as modification of the chromatin structure are involved in the transcriptional regulation of the 5S rRNA genes in both organisms. In Arabidopsis, two silencing pathways, methylation-dependent (RNAi) and methylation-independent (MOM pathway), are involved in the silencing of a 5S rDNA fraction.
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Affiliation(s)
- J Douet
- Unité Mixte de Recherche CNRS 6547 BIOMOVE, Université Blaise Pascal, Aubière Cedex, France
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Vaillant I, Tutois S, Cuvillier C, Schubert I, Tourmente S. Regulation of Arabidopsis thaliana 5S rRNA Genes. PLANT & CELL PHYSIOLOGY 2007; 48:745-52. [PMID: 17412735 DOI: 10.1093/pcp/pcm043] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
The Arabidopsis thaliana genome comprises around 1,000 copies of 5S rRNA genes encoding both major and minor 5S rRNAs. In mature wild-type leaves, the minor 5S rRNA genes are silent. Using different mutants of DNA methyltransferases (met1, cmt3 and met1 cmt3), components of the RNAi pathway (ago4) or post-translational histone modifier (hda6/sil1), we show that the corresponding proteins are needed to maintain proper methylation patterns at heterochromatic 5S rDNA repeats. Using reverse transcription-PCR and cytological analyses, we report that a decrease of 5S rDNA methylation at CG or CNG sites in these mutants leads to the release of 5S rRNA gene silencing which occurred without detectable changes of the 5S rDNA chromatin structure. In spite of severely reduced DNA methylation, the met1 cmt3 double mutant revealed no increase in minor 5S rRNA transcripts. Furthermore, the release of silencing of minor 5S rDNAs can be achieved without increased formation of euchromatic loops by 5S rDNA, and is independent from the global heterochromatin content. Additionally, fluorescence in situ hybridization with centromeric 180 bp repeats confirmed that these highly repetitive sequences, in spite of their elevated transcriptional activity in the DNA methyltransferase mutants (met1, cmt3 and met1 cmt3), remain within chromocenters of the mutant nuclei.
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Affiliation(s)
- Isabelle Vaillant
- Unité Mixte de Recherche CNRS 6547 BIOMOVE, Université Blaise Pascal, 24 Avenue des Landais, F-63177 Aubière Cedex, France
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Cross I, Rebordinos L. 5S rDNA and U2 snRNA are linked in the genome of Crassostrea angulata and Crassostrea gigas oysters: does the (CT)n.(GA)n microsatellite stabilize this novel linkage of large tandem arrays? Genome 2007; 48:1116-9. [PMID: 16391680 DOI: 10.1139/g05-075] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The 5S rRNA genes from 2 species of the Ostreidae family, Crassostrea angulata and Crassostrea gigas, were molecularly characterized. The genes were amplified, cloned, and sequenced. The results revealed a 5S rDNA tandem array with a nucleotide sequence in an inverted position within the nontranscribed spacer region that corresponded to the U2 small nuclear RNA (snRNA) gene. The sequence analysis indicated that both genes could be functionally active. The presence of the microsatellite (CT)n x (GA)n at the 3' end of both genes and the possible involvement of concerted evolution are discussed.
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Affiliation(s)
- I Cross
- Laboratorio de Genética, Facultad de Ciencias del Mar y Ambientales, Universidad de Cádiz, Spain
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Abstract
RNA polymerase III (pol III) transcribes many essential, small, noncoding RNAs, including the 5S rRNAs and tRNAs. While most pol III-transcribed genes are found scattered throughout the linear chromosome maps or in multiple linear clusters, there is increasing evidence that many of these genes prefer to be spatially clustered, often at or near the nucleolus. This association could create an environment that fosters the coregulation of transcription by pol III with transcription of the large ribosomal RNA repeats by RNA polymerase I (pol I) within the nucleolus. Given the high number of pol III-transcribed genes in all eukaryotic genomes, the spatial organization of these genes is likely to affect a large portion of the other genes in a genome. In this Survey and Summary we analyze the reports regarding the spatial organization of pol III genes and address the potential influence of this organization on transcriptional regulation.
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Affiliation(s)
| | - David R. Engelke
- To whom correspondence should be addressed. Tel: +1 734 763 0641; Fax:+1 734 763 7799;
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Cabral JS, Felix LP, Guerra M. Heterochromatin diversity and its co-localization with 5S and 45S rDNA sites in chromosomes of four Maxillaria species (Orchidaceae). Genet Mol Biol 2006. [DOI: 10.1590/s1415-47572006000400015] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
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50
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Simon DM, Hummel CL, Sheeley SL, Bhattacharya D. Heterogeneity of intron presence or absence in rDNA genes of the lichen species Physcia aipolia and P. stellaris. Curr Genet 2005; 47:389-99. [PMID: 15868149 DOI: 10.1007/s00294-005-0581-5] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2005] [Revised: 03/22/2005] [Accepted: 03/29/2005] [Indexed: 10/25/2022]
Abstract
Intron origin and evolution are of high interest, yet the rates of insertion and loss are unclear. To investigate their spread, we studied ribosomal (r)DNA introns from the closely related lichens Physcia aipolia and P. stellaris. Both taxa are replete with rDNA spliceosomal introns and autocatalytic group I introns, many of which show presence/absence polymorphism when screened with the PCR approach. This initially suggested that Physcia could be a model for studying intron retention and loss. However, during the course of a population-level analysis, we discovered widespread intron presence/absence heterogeneity within lichen thalli. To address this result, we sequenced multiple clones encoding nuclear rDNA and the single-copy elongation factor-1alpha (EF-1alpha) from individual thalli. These data showed extensive rDNA heterogeneity within individuals, rather than the presence of multiple fungi within a thallus. Our results suggest that considerable care must be taken when interpreting intron presence/absence in lichen rDNA, an observation that has general implications for the study of rDNA intron evolution.
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Affiliation(s)
- Dawn M Simon
- Department of Biological Sciences and Roy J. Carver Center for Comparative Genomics, University of Iowa, 312 Biology Building, Iowa City, IA 52242-1324, USA
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