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Valeeva LR, Abdulkina LR, Agabekian IA, Shakirov EV. Telomere biology and ribosome biogenesis: structural and functional interconnections. Biochem Cell Biol 2023; 101:394-409. [PMID: 36989538 DOI: 10.1139/bcb-2022-0383] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/31/2023] Open
Abstract
Telomeres are nucleoprotein structures that play a pivotal role in the protection and maintenance of eukaryotic chromosomes. Telomeres and the enzyme telomerase, which replenishes telomeric DNA lost during replication, are important factors necessary to ensure continued cell proliferation. Cell proliferation is also dependent on proper and efficient protein synthesis, which is carried out by ribosomes. Mutations in genes involved in either ribosome biogenesis or telomere biology result in cellular abnormalities and can cause human genetic diseases, defined as ribosomopathies and telomeropathies, respectively. Interestingly, recent discoveries indicate that many of the ribosome assembly and rRNA maturation factors have additional noncanonical functions in telomere biology. Similarly, several key proteins and enzymes involved in telomere biology, including telomerase, have unexpected roles in rRNA transcription and maturation. These observations point to an intriguing cross-talk mechanism potentially explaining the multiple pleiotropic symptoms of mutations in many causal genes identified in various telomeropathy and ribosomopathy diseases. In this review, we provide a brief summary of eukaryotic telomere and rDNA loci structures, highlight several universal features of rRNA and telomerase biogenesis, evaluate intriguing interconnections between telomere biology and ribosome assembly, and conclude with an assessment of overlapping features of human diseases of telomeropathies and ribosomopathies.
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Affiliation(s)
- Liia R Valeeva
- Institute of Fundamental Medicine and Biology, Kazan Federal University, Kazan 420008, Republic of Tatarstan, Russia
- Department of Biological Sciences, College of Science, Marshall University, Huntington, WV 25701, USA
| | - Liliia R Abdulkina
- Institute of Fundamental Medicine and Biology, Kazan Federal University, Kazan 420008, Republic of Tatarstan, Russia
| | - Inna A Agabekian
- Institute of Fundamental Medicine and Biology, Kazan Federal University, Kazan 420008, Republic of Tatarstan, Russia
| | - Eugene V Shakirov
- Department of Biological Sciences, College of Science, Marshall University, Huntington, WV 25701, USA
- Department of Biomedical Sciences, Joan C. Edwards School of Medicine, Marshall University, Huntington, WV 25755, USA
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Plant Cytogenetics in the Micronuclei Investigation-The Past, Current Status, and Perspectives. Int J Mol Sci 2022; 23:ijms23031306. [PMID: 35163228 PMCID: PMC8836153 DOI: 10.3390/ijms23031306] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2021] [Revised: 01/22/2022] [Accepted: 01/22/2022] [Indexed: 01/27/2023] Open
Abstract
Cytogenetic approaches play an essential role as a quick evaluation of the first genetic effects after mutagenic treatment. Although labor-intensive and time-consuming, they are essential for the analyses of cytotoxic and genotoxic effects in mutagenesis and environmental monitoring. Over the years, conventional cytogenetic analyses were a part of routine laboratory testing in plant genotoxicity. Among the methods that are used to study genotoxicity in plants, the micronucleus test particularly represents a significant force. Currently, cytogenetic techniques go beyond the simple detection of chromosome aberrations. The intensive development of molecular biology and the significantly improved microscopic visualization and evaluation methods constituted significant support to traditional cytogenetics. Over the past years, distinct approaches have allowed an understanding the mechanisms of formation, structure, and genetic activity of the micronuclei. Although there are many studies on this topic in humans and animals, knowledge in plants is significantly limited. This article provides a comprehensive overview of the current knowledge on micronuclei characteristics in plants. We pay particular attention to how the recent contemporary achievements have influenced the understanding of micronuclei in plant cells. Together with the current progress, we present the latest applications of the micronucleus test in mutagenesis and assess the state of the environment.
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Tomaszewska P, Kosina R. Cytogenetic events in the endosperm of amphiploid Avena magna × A. longiglumis. JOURNAL OF PLANT RESEARCH 2021; 134:1047-1060. [PMID: 34057611 PMCID: PMC8364899 DOI: 10.1007/s10265-021-01314-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/13/2021] [Accepted: 05/19/2021] [Indexed: 05/13/2023]
Abstract
This study analysed cytogenetic events occurring in the syncytial endosperm of the Avena magna H. C. Murphy & Terrell × Avena longiglumis Durieu amphiploid, which is a product of two wild species having different genomes. Selection through the elimination of chromosomes and their fragments, including those translocated, decreased the level of ploidy in the endosperm below the expected 3n, leading to the modal number close to 2n. During intergenomic translocations, fragments of the heterochromatin-rich C-genome were transferred to the D and Al genomes. Terminal and non-reciprocal exchanges dominated, whereas other types of translocations, including microexchanges, were less common. Using two probes and by counterstaining with DAPI, the A. longiglumis and the rare exchanges between the D and Al genomes were detected by GISH. The large discontinuity in the probe labelling in the C chromosomes demonstrated inequality in the distribution of repetitive sequences along the chromosome and probable intragenomic rearrangements. In the nucleus, the spatial arrangement of genomes was non-random and showed a sectorial-concentric pattern, which can vary during the cell cycle, especially in the less stable tissue like the hybrid endosperm.
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Affiliation(s)
| | - Romuald Kosina
- Institute of Environmental Biology, University of Wrocław, Przybyszewskiego 63, 51-148, Wroclaw, Poland.
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Chaux-Jukic F, O'Donnell S, Craig RJ, Eberhard S, Vallon O, Xu Z. Architecture and evolution of subtelomeres in the unicellular green alga Chlamydomonas reinhardtii. Nucleic Acids Res 2021; 49:7571-7587. [PMID: 34165564 PMCID: PMC8287924 DOI: 10.1093/nar/gkab534] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2021] [Revised: 06/01/2021] [Accepted: 06/08/2021] [Indexed: 02/06/2023] Open
Abstract
In most eukaryotes, subtelomeres are dynamic genomic regions populated by multi-copy sequences of different origins, which can promote segmental duplications and chromosomal rearrangements. However, their repetitive nature has complicated the efforts to sequence them, analyse their structure and infer how they evolved. Here, we use recent genome assemblies of Chlamydomonas reinhardtii based on long-read sequencing to comprehensively describe the subtelomere architecture of the 17 chromosomes of this model unicellular green alga. We identify three main repeated elements present at subtelomeres, which we call Sultan, Subtile and Suber, alongside three chromosome extremities with ribosomal DNA as the only identified component of their subtelomeres. The most common architecture, present in 27 out of 34 subtelomeres, is a heterochromatic array of Sultan elements adjacent to the telomere, followed by a transcribed Spacer sequence, a G-rich microsatellite and transposable elements. Sequence similarity analyses suggest that Sultan elements underwent segmental duplications within each subtelomere and rearranged between subtelomeres at a much lower frequency. Analysis of other green algae reveals species-specific repeated elements that are shared across subtelomeres, with an overall organization similar to C. reinhardtii. This work uncovers the complexity and evolution of subtelomere architecture in green algae.
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Affiliation(s)
- Frédéric Chaux-Jukic
- Sorbonne Université, CNRS, UMR7238, Institut de Biologie Paris-Seine, Laboratory of Computational and Quantitative Biology, 75005 Paris, France
| | - Samuel O'Donnell
- Sorbonne Université, CNRS, UMR7238, Institut de Biologie Paris-Seine, Laboratory of Computational and Quantitative Biology, 75005 Paris, France
| | - Rory J Craig
- Institute of Evolutionary Biology, School of Biological Sciences, University of Edinburgh, EH9 3FL, Edinburgh, UK
| | - Stephan Eberhard
- Sorbonne Université, CNRS, UMR7141, Institut de Biologie Physico-Chimique, Laboratory of Chloroplast Biology and Light-Sensing in Microalgae, 75005 Paris, France
| | - Olivier Vallon
- Sorbonne Université, CNRS, UMR7141, Institut de Biologie Physico-Chimique, Laboratory of Chloroplast Biology and Light-Sensing in Microalgae, 75005 Paris, France
| | - Zhou Xu
- Sorbonne Université, CNRS, UMR7238, Institut de Biologie Paris-Seine, Laboratory of Computational and Quantitative Biology, 75005 Paris, France
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Kus A, Szymanowska-Pułka J, Kwasniewska J, Hasterok R. Detecting Brachypodium distachyon Chromosomes Bd4 and Bd5 in MH- and X-Ray-Induced Micronuclei Using mcFISH. Int J Mol Sci 2019; 20:ijms20112848. [PMID: 31212692 PMCID: PMC6612364 DOI: 10.3390/ijms20112848] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2019] [Revised: 05/22/2019] [Accepted: 06/08/2019] [Indexed: 12/18/2022] Open
Abstract
Micronuclei are biomarkers of genotoxic effects and chromosomal instability. They are formed when chromosome fragments or whole chromosomes fail to disjoin into daughter nuclei. We present qualitative and quantitative analyses of the involvement of specific chromosome regions of chromosomes Bd4 and Bd5 in the formation of micronuclei of Brachypodium distachyon root tip cells following maleic hydrazide (MH) treatment and X-radiation. This is visualised by cytomolecular approaches using bacterial artificial chromosome (BAC)-based multicolour fluorescence in situ hybridisation (mcFISH) in combination with 5S and 25S rDNA probes. The results showed that the long arm of submetacentric chromosome Bd4 forms micronuclei at twice the frequency of its short arm, suggesting that the former is more prone to double-strand breaks (DSBs). In contrast, no difference was observed in the frequency of micronuclei derived from the long and short arms of submetacentric chromosome Bd5. Interestingly, the proximal region of the short arm of Bd5 is more prone to DSBs than its distal part. This demonstrates that 5S rDNA and 35S rDNA loci are not "hot spots" for DNA breaks after the application of these mutagens.
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Affiliation(s)
- Arita Kus
- Department of Plant Anatomy and Cytology, Faculty of Biology and Environmental Protection, University of Silesia in Katowice, 28 Jagiellonska Street, 40-032 Katowice, Poland.
| | - Joanna Szymanowska-Pułka
- Department of Biophysics and Morphogenesis of Plants, Faculty of Biology and Environmental Protection, University of Silesia in Katowice, 28 Jagiellonska Street, 40-032 Katowice, Poland.
| | - Jolanta Kwasniewska
- Department of Plant Anatomy and Cytology, Faculty of Biology and Environmental Protection, University of Silesia in Katowice, 28 Jagiellonska Street, 40-032 Katowice, Poland.
| | - Robert Hasterok
- Department of Plant Anatomy and Cytology, Faculty of Biology and Environmental Protection, University of Silesia in Katowice, 28 Jagiellonska Street, 40-032 Katowice, Poland.
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Goffová I, Vágnerová R, Peška V, Franek M, Havlová K, Holá M, Zachová D, Fojtová M, Cuming A, Kamisugi Y, Angelis KJ, Fajkus J. Roles of RAD51 and RTEL1 in telomere and rDNA stability in Physcomitrella patens. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2019; 98:1090-1105. [PMID: 30834585 DOI: 10.1111/tpj.14304] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/23/2019] [Revised: 02/21/2019] [Accepted: 02/27/2019] [Indexed: 05/11/2023]
Abstract
Telomeres and ribosomal RNA genes (rDNA) are essential for cell survival and particularly sensitive to factors affecting genome stability. Here, we examine the role of RAD51 and its antagonist, RTEL1, in the moss Physcomitrella patens. In corresponding mutants, we analyse their sensitivity to DNA damage, the maintenance of telomeres and rDNA, and repair of double-stranded breaks (DSBs) induced by genotoxins with various modes of action. While the loss of RTEL1 results in rapid telomere shortening, concurrent loss of both RAD51 genes has no effect on telomere lengths. We further demonstrate here the linked arrangement of 5S and 45S rRNA genes in P. patens. The spacer between 5S and 18S rRNA genes, especially the region downstream from the transcription start site, shows conspicuous clustering of sites with a high propensity to form quadruplex (G4) structures. Copy numbers of 5S and 18S rDNA are reduced moderately in the pprtel1 mutant, and significantly in the double pprad51-1-2 mutant, with no progression during subsequent cultivation. While reductions in 45S rDNA copy numbers observed in pprtel1 and pprad51-1-2 plants apply also to 5S rDNA, changes in transcript levels are different for 45S and 5S rRNA, indicating their independent transcription by RNA polymerase I and III, respectively. The loss of SOL (Sog One-Like), a transcription factor regulating numerous genes involved in DSB repair, increases the rate of DSB repair in dividing as well as differentiated tissue, and through deactivation of G2/M cell-cycle checkpoint allows the cell-cycle progression manifested as a phenotype resistant to bleomycin.
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Affiliation(s)
- Ivana Goffová
- Laboratory of Functional Genomics and Proteomics, National Centre for Biomolecular Research, Faculty of Science, Masaryk University, Kotlářská 2, CZ-61137, Brno, Czech Republic
- Mendel Centre for Plant Genomics and Proteomics, Central European Institute of Technology, Masaryk University, Kamenice 5, CZ-62500, Brno, Czech Republic
| | - Radka Vágnerová
- The Czech Academy of Sciences, Institute of Experimental Botany, Na Karlovce 1, CZ-16000, Prague, Czech Republic
| | - Vratislav Peška
- The Czech Academy of Sciences, Institute of Biophysics, Královopolská 135, 612 65, Brno, Czech Republic
| | - Michal Franek
- Laboratory of Functional Genomics and Proteomics, National Centre for Biomolecular Research, Faculty of Science, Masaryk University, Kotlářská 2, CZ-61137, Brno, Czech Republic
- Mendel Centre for Plant Genomics and Proteomics, Central European Institute of Technology, Masaryk University, Kamenice 5, CZ-62500, Brno, Czech Republic
| | - Kateřina Havlová
- Laboratory of Functional Genomics and Proteomics, National Centre for Biomolecular Research, Faculty of Science, Masaryk University, Kotlářská 2, CZ-61137, Brno, Czech Republic
- Mendel Centre for Plant Genomics and Proteomics, Central European Institute of Technology, Masaryk University, Kamenice 5, CZ-62500, Brno, Czech Republic
| | - Marcela Holá
- The Czech Academy of Sciences, Institute of Experimental Botany, Na Karlovce 1, CZ-16000, Prague, Czech Republic
| | - Dagmar Zachová
- Laboratory of Functional Genomics and Proteomics, National Centre for Biomolecular Research, Faculty of Science, Masaryk University, Kotlářská 2, CZ-61137, Brno, Czech Republic
- Mendel Centre for Plant Genomics and Proteomics, Central European Institute of Technology, Masaryk University, Kamenice 5, CZ-62500, Brno, Czech Republic
| | - Miloslava Fojtová
- Laboratory of Functional Genomics and Proteomics, National Centre for Biomolecular Research, Faculty of Science, Masaryk University, Kotlářská 2, CZ-61137, Brno, Czech Republic
- Mendel Centre for Plant Genomics and Proteomics, Central European Institute of Technology, Masaryk University, Kamenice 5, CZ-62500, Brno, Czech Republic
| | - Andrew Cuming
- Centre for Plant Sciences, Faculty of Biological Sciences, University of Leeds, Leeds, LS2 9JT, UK
| | - Yasuko Kamisugi
- Centre for Plant Sciences, Faculty of Biological Sciences, University of Leeds, Leeds, LS2 9JT, UK
| | - Karel J Angelis
- The Czech Academy of Sciences, Institute of Experimental Botany, Na Karlovce 1, CZ-16000, Prague, Czech Republic
| | - Jiří Fajkus
- Laboratory of Functional Genomics and Proteomics, National Centre for Biomolecular Research, Faculty of Science, Masaryk University, Kotlářská 2, CZ-61137, Brno, Czech Republic
- Mendel Centre for Plant Genomics and Proteomics, Central European Institute of Technology, Masaryk University, Kamenice 5, CZ-62500, Brno, Czech Republic
- The Czech Academy of Sciences, Institute of Biophysics, Královopolská 135, 612 65, Brno, Czech Republic
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Kus A, Kwasniewska J, Szymanowska-Pułka J, Hasterok R. Dissecting the chromosomal composition of mutagen-induced micronuclei in Brachypodium distachyon using multicolour FISH. ANNALS OF BOTANY 2018; 122:1161-1171. [PMID: 29982446 PMCID: PMC6324755 DOI: 10.1093/aob/mcy115] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/31/2017] [Accepted: 06/01/2018] [Indexed: 06/08/2023]
Abstract
BACKGROUND AND AIMS Brachypodium distachyon (Brachypodium) is a model species for temperate cereals and other economically important grasses. Its favourable cytogenetic features and advanced molecular infrastructure make it a good model for understanding the mechanisms of instability of plant genomes after mutagenic treatment. The aim of this study was to qualitatively and quantitatively assess the composition and origin of micronuclei arising from genomic fracture, and to detect possible 'hot spots' for mutagen-induced DNA breaks. METHODS Seeds of Brachypodium were treated with maleic hydrazide (MH) or X-rays. The structure of mutagen-induced micronuclei was analysed in root-tip meristematic cells using multicolour fluorescence in situ hybridization (mcFISH) with various repetitive (5S rDNA, 25S rDNA, telomeric, centromeric) and low-repeat [small and large pools of bacterial artificial chromosome (BAC) clones specific for chromosome Bd1] DNA sequences. KEY RESULTS The majority of micronuclei derive from large, acentric fragments. X-rays caused more interstitial DNA breaks than MH. Double-strand breaks rarely occurred in distal chromosome regions. Bd1 contributed to the formation of more mutagen-induced micronuclei than expected from random chromosome involvement. CONCLUSIONS mcFISH with chromosome-specific BAC clones offers insight into micronuclei composition, in so far as it allows their origin and formation to be determined more specifically. A reliable assay for micronuclei composition is crucial for the development of modern genotoxicity tests using plant cells. The combination of mutagenic treatments and well-developed cytomolecular resources in Brachypodium make this model species very promising for plant mutagenesis research.
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Affiliation(s)
- Arita Kus
- Department of Plant Anatomy and Cytology, Faculty of Biology and Environmental Protection, University of Silesia in Katowice, Katowice, Poland
| | - Jolanta Kwasniewska
- Department of Plant Anatomy and Cytology, Faculty of Biology and Environmental Protection, University of Silesia in Katowice, Katowice, Poland
| | - Joanna Szymanowska-Pułka
- Department of Biophysics and Plant Morphogenesis, Faculty of Biology and Environmental Protection, University of Silesia in Katowice, Katowice, Poland
| | - Robert Hasterok
- Department of Plant Anatomy and Cytology, Faculty of Biology and Environmental Protection, University of Silesia in Katowice, Katowice, Poland
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Kus A, Kwasniewska J, Hasterok R. Brachypodium distachyon - A Useful Model in the Qualification of Mutagen-Induced Micronuclei Using Multicolor FISH. PLoS One 2017; 12:e0170618. [PMID: 28118403 PMCID: PMC5261735 DOI: 10.1371/journal.pone.0170618] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2016] [Accepted: 12/15/2016] [Indexed: 12/21/2022] Open
Abstract
Brachypodium distachyon (Brachypodium) is now intensively utilized as a model grass species in various biological studies. Its favorable cytological features create a unique foundation for a convenient system in mutagenesis, thereby potentially enabling the 'hot spots' and 'cold spots' of DNA damage in its genome to be analyzed. The aim of this study was to analyze the involvement of 5S rDNA, 25S rDNA, the Arabidopsis-type (TTTAGGG)n telomeric sequence and the Brachypodium-originated centromeric BAC clone CB33J12 in the micronuclei formation in Brachypodium root tip cells that were subjected to the chemical clastogenic agent maleic hydrazide (MH). To the best of our knowledge, this is the first use of a multicolor fluorescence in situ hybridization (mFISH) with four different DNA probes being used simultaneously to study plant mutagenesis. A quantitative analysis allowed ten types of micronuclei, which were characterized by the presence or absence of specific FISH signal(s), to be distinguished, thus enabling some specific rules governing the composition of the MH-induced micronuclei with the majority of them originating from the terminal regions of chromosomes, to be identified. The application of rDNA sequences as probes showed that 5S rDNA-bearing chromosomes are involved in micronuclei formation more frequently than the 25S rDNA-bearing chromosomes. These findings demonstrate the promising potential of Brachypodium to be a useful model organism to analyze the effects of various genotoxic agents on the plant nuclear genome stability, especially when the complex FISH-based and chromosome-specific approaches such as chromosome barcoding and chromosome painting will be applied in future studies.
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Affiliation(s)
- Arita Kus
- Department of Plant Anatomy and Cytology, Faculty of Biology and Environmental Protection, University of Silesia in Katowice, Katowice, Poland
| | - Jolanta Kwasniewska
- Department of Plant Anatomy and Cytology, Faculty of Biology and Environmental Protection, University of Silesia in Katowice, Katowice, Poland
| | - Robert Hasterok
- Department of Plant Anatomy and Cytology, Faculty of Biology and Environmental Protection, University of Silesia in Katowice, Katowice, Poland
- * E-mail:
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Chen YJC, Wang HJ, Jauh GY. Dual Role of a SAS10/C1D Family Protein in Ribosomal RNA Gene Expression and Processing Is Essential for Reproduction in Arabidopsis thaliana. PLoS Genet 2016; 12:e1006408. [PMID: 27792779 PMCID: PMC5085252 DOI: 10.1371/journal.pgen.1006408] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2016] [Accepted: 10/06/2016] [Indexed: 12/20/2022] Open
Abstract
In eukaryotic cells, ribosomal RNAs (rRNAs) are transcribed, processed, and assembled with ribosomal proteins in the nucleolus. Regulatory mechanisms of rRNA gene (rDNA) transcription and processing remain elusive in plants, especially their connection to nucleolar organization. We performed an in silico screen for essential genes of unknown function in Arabidopsis thaliana and identified Thallo (THAL) encoding a SAS10/C1D family protein. THAL disruption caused enlarged nucleoli in arrested embryos, aberrant processing of precursor rRNAs at the 5' External Transcribed Spacer, and repression of the major rDNA variant (VAR1). THAL overexpression lines showed de-repression of VAR1 and overall reversed effects on rRNA processing sites. Strikingly, THAL overexpression also induced formation of multiple nucleoli per nucleus phenotypic of mutants of heterochromatin factors. THAL physically associated with histone chaperone Nucleolin 1 (NUC1), histone-binding NUC2, and histone demethylase Jumonji 14 (JMJ14) in bimolecular fluorescence complementation assay, suggesting that it participates in chromatin regulation. Furthermore, investigation of truncated THAL proteins revealed that the SAS10 C-terminal domain is likely important for its function in chromatin configuration. THAL also interacted with putative Small Subunit processome components, including previously unreported Arabidopsis homologue of yeast M Phase Phosphoprotein 10 (MPP10). Our results uncovering the dual role of THAL in transcription and processing events critical for proper rRNA biogenesis and nucleolar organization during reproduction are the first to define the function of SAS10/C1D family members in plants.
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Affiliation(s)
- Ying-Jiun C. Chen
- Institute of Plant and Microbial Biology, Academia Sinica, Taipei, Taiwan
- Molecular and Biological Agricultural Sciences Program, Taiwan International Graduate Program, Academia Sinica and National Chung Hsing University, Taichung, Taiwan
- Graduate Institute of Biotechnology, National Chung-Hsing University, Taichung, Taiwan
| | - Huei-Jing Wang
- Institute of Plant and Microbial Biology, Academia Sinica, Taipei, Taiwan
| | - Guang-Yuh Jauh
- Institute of Plant and Microbial Biology, Academia Sinica, Taipei, Taiwan
- Molecular and Biological Agricultural Sciences Program, Taiwan International Graduate Program, Academia Sinica and National Chung Hsing University, Taichung, Taiwan
- Biotechnology Center, National Chung-Hsing University, Taichung, Taiwan
- * E-mail:
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Fajkus P, Peška V, Sitová Z, Fulnečková J, Dvořáčková M, Gogela R, Sýkorová E, Hapala J, Fajkus J. Allium telomeres unmasked: the unusual telomeric sequence (CTCGGTTATGGG)n is synthesized by telomerase. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2016; 85:337-47. [PMID: 26716914 DOI: 10.1111/tpj.13115] [Citation(s) in RCA: 58] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/19/2015] [Revised: 12/17/2015] [Accepted: 12/22/2015] [Indexed: 05/25/2023]
Abstract
Phylogenetic divergence in Asparagales plants is associated with switches in telomere sequences. The last switch occurred with divergence of the genus Allium (Amaryllidaceae) from the other Allioideae (formerly Alliaceae) genera, resulting in uncharacterized telomeres maintained by an unknown mechanism. To characterize the unknown Allium telomeres, we applied a combination of bioinformatic processing of transcriptomic and genomic data with standard approaches in telomere biology such as BAL31 sensitivity tests, terminal restriction fragment analysis, the telomere repeat amplification protocol (TRAP), and fluorescence in situ hybridization (FISH). Using these methods, we characterize the unusual telomeric sequence (CTCGGTTATGGG)n present in Allium species, demonstrate its synthesis by telomerase, and characterize the telomerase reverse transcriptase (TERT) subunit of Allium cepa. Our findings open up the possibility of studying the molecular details of the evolutionary genetic change in Allium telomeres and its possible role in speciation. Experimental studies addressing the implications of this change in terms of the interplay of telomere components may now be designed to shed more light on telomere functions and evolution in general.
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Affiliation(s)
- Petr Fajkus
- Mendel Centre for Plant Genomics and Proteomics, Central European Institute of Technology, Masaryk University, Kamenice 5, CZ-62500, Brno, Czech Republic
- Institute of Biophysics, Czech Academy of Sciences, Královopolská 135, CZ-61265, Brno, Czech Republic
| | - Vratislav Peška
- Institute of Biophysics, Czech Academy of Sciences, Královopolská 135, CZ-61265, Brno, Czech Republic
| | - Zdeňka Sitová
- Mendel Centre for Plant Genomics and Proteomics, Central European Institute of Technology, Masaryk University, Kamenice 5, CZ-62500, Brno, Czech Republic
| | - Jana Fulnečková
- Institute of Biophysics, Czech Academy of Sciences, Královopolská 135, CZ-61265, Brno, Czech Republic
| | - Martina Dvořáčková
- Mendel Centre for Plant Genomics and Proteomics, Central European Institute of Technology, Masaryk University, Kamenice 5, CZ-62500, Brno, Czech Republic
- Institute of Biophysics, Czech Academy of Sciences, Královopolská 135, CZ-61265, Brno, Czech Republic
| | - Roman Gogela
- Mendel Centre for Plant Genomics and Proteomics, Central European Institute of Technology, Masaryk University, Kamenice 5, CZ-62500, Brno, Czech Republic
| | - Eva Sýkorová
- Institute of Biophysics, Czech Academy of Sciences, Královopolská 135, CZ-61265, Brno, Czech Republic
| | - Jan Hapala
- Mendel Centre for Plant Genomics and Proteomics, Central European Institute of Technology, Masaryk University, Kamenice 5, CZ-62500, Brno, Czech Republic
| | - Jiří Fajkus
- Mendel Centre for Plant Genomics and Proteomics, Central European Institute of Technology, Masaryk University, Kamenice 5, CZ-62500, Brno, Czech Republic
- Laboratory of Functional Genomics and Proteomics, National Centre for Biomolecular Research, Faculty of Science, Masaryk University, Kamenice 5, CZ-62500, Brno, Czech Republic
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Dvořáčková M, Fojtová M, Fajkus J. Chromatin dynamics of plant telomeres and ribosomal genes. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2015; 83:18-37. [PMID: 25752316 DOI: 10.1111/tpj.12822] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/28/2015] [Revised: 03/03/2015] [Accepted: 03/03/2015] [Indexed: 05/03/2023]
Abstract
Telomeres and genes encoding 45S ribosomal RNA (rDNA) are frequently located adjacent to each other on eukaryotic chromosomes. Although their primary roles are different, they show striking similarities with respect to their features and additional functions. Both genome domains have remarkably dynamic chromatin structures. Both are hypersensitive to dysfunctional histone chaperones, responding at the genomic and epigenomic levels. Both generate non-coding transcripts that, in addition to their epigenetic roles, may induce gross chromosomal rearrangements. Both give rise to chromosomal fragile sites, as their replication is intrinsically problematic. However, at the same time, both are essential for maintenance of genomic stability and integrity. Here we discuss the structural and functional inter-connectivity of telomeres and rDNA, with a focus on recent results obtained in plants.
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Affiliation(s)
- Martina Dvořáčková
- Mendel Centre for Plant Genomics and Proteomics, Central European Institute of Technology, Kamenice 5, 62500, Brno, Czech Republic
- Faculty of Science, Masaryk University, Kamenice 5, 62500, Brno, Czech Republic
- Institute of Biophysics, Academy of Sciences of the Czech Republic, Královopolská 135, 61265, Brno, Czech Republic
| | - Miloslava Fojtová
- Mendel Centre for Plant Genomics and Proteomics, Central European Institute of Technology, Kamenice 5, 62500, Brno, Czech Republic
- Faculty of Science, Masaryk University, Kamenice 5, 62500, Brno, Czech Republic
- Institute of Biophysics, Academy of Sciences of the Czech Republic, Královopolská 135, 61265, Brno, Czech Republic
| | - Jiří Fajkus
- Mendel Centre for Plant Genomics and Proteomics, Central European Institute of Technology, Kamenice 5, 62500, Brno, Czech Republic
- Faculty of Science, Masaryk University, Kamenice 5, 62500, Brno, Czech Republic
- Institute of Biophysics, Academy of Sciences of the Czech Republic, Královopolská 135, 61265, Brno, Czech Republic
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12
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A telomerase-independent component of telomere loss in chromatin assembly factor 1 mutants of Arabidopsis thaliana. Chromosoma 2013; 122:285-93. [PMID: 23564254 DOI: 10.1007/s00412-013-0400-6] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2013] [Revised: 02/14/2013] [Accepted: 02/19/2013] [Indexed: 01/23/2023]
Abstract
Dysfunction of chromatin assembly factor 1 in FASCIATA mutants (fas) of Arabidopsis thaliana results in progressive loss of telomeric DNA. Although replicative telomere shortening is typically associated with incomplete resynthesis of their ends by telomerase, no change in telomerase activity could be detected in vitro in extracts from fas mutants. Besides a possible telomerase malfunction, the telomere shortening in fas mutants could presumably be due to problems with conventional replication of telomeres. To distinguish between the possible contribution of suboptimal function of telomerase in fas mutants under in vivo conditions and problems in conventional telomere replication, we crossed fas and tert (telomerase reverse transcriptase) knockout mutants and analyzed telomere shortening in segregated fas mutants, tert mutants, and double fas tert mutants in parallel. We demonstrate that fas tert knockouts show greater replicative telomere shortening than that observed even in the complete absence of telomerase (tert mutants). While the effect of tert and fas mutations on telomere lengths in double mutants is additive, manifestations of telomere dysfunction in double fas tert mutants (frequency of anaphase bridges, onset of chromosome end fusions, and common involvement of 45S rDNA in chromosome fusion sites) are similar to those in tert mutants. We conclude that in addition to possible impairment of telomerase action, a further mechanism contributes to telomere shortening in fas mutants.
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13
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Singh M, Barman AS. Chromosome breakages associated with 45S ribosomal DNA sequences in spotted snakehead fish Channa punctatus. Mol Biol Rep 2012; 40:723-9. [PMID: 23065230 DOI: 10.1007/s11033-012-2112-z] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2012] [Accepted: 10/03/2012] [Indexed: 10/27/2022]
Abstract
It is well known that transcriptionally inactive rRNA genes are correlated with DNA hyper-methylation and histone hypo-methylation and there is clear evidence in humans that DNA and histone modification which alter chromatin structure are related to chromosome fragility. Very little is known about the biological cause of 45S rDNA fragility. In this report we characterized the chromosome breakage or gap associated with 45S rDNA in a fish species Channa punctatus. The rDNA mapping in C. punctatus, showed many chromosome breakages or gap formations, and all occurred exclusively in the 45S rDNA sites in anterior kidney cells. We observed that the number of chromosomes plus chromosome fragments was often more than the expected 32 in most cells. Total 67 % metaphase spread showed the expected or normal 32 chromosomes, while 33 % metaphase spread showed 33 and/or 34 chromosomes and/or chromosome fragments. The chromosome lesions observed in this study are very similar cytologically to that of fragile sites observed in human chromosomes. Possible causes for the spontaneous expression of fragile sites and their potential biological significance are also discussed in present report.
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Affiliation(s)
- Mamta Singh
- Department of Fish Genetics and Reproduction, College of Fisheries (Central Agriculture University) Lembucherra, Tripura (W) 799210, India.
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14
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Najdekrova L, Siroky J. NBS1 plays a synergistic role with telomerase in the maintenance of telomeres in Arabidopsis thaliana. BMC PLANT BIOLOGY 2012; 12:167. [PMID: 22985462 PMCID: PMC3490983 DOI: 10.1186/1471-2229-12-167] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/30/2012] [Accepted: 09/10/2012] [Indexed: 05/29/2023]
Abstract
BACKGROUND Telomeres, as elaborate nucleo-protein complexes, ensure chromosomal stability. When impaired, the ends of linear chromosomes can be recognised by cellular repair mechanisms as double-strand DNA breaks and can be healed by non-homologous-end-joining activities to produce dicentric chromosomes. During cell divisions, particularly during anaphase, dicentrics can break, thus producing naked chromosome tips susceptible to additional unwanted chromosome fusion. Many telomere-building protein complexes are associated with telomeres to ensure their proper capping function. It has been found however, that a number of repair complexes also contribute to telomere stability. RESULTS We used Arabidopsis thaliana to study the possible functions of the DNA repair subunit, NBS1, in telomere homeostasis using knockout nbs1 mutants. The results showed that although NBS1-deficient plants were viable, lacked any sign of developmental aberration and produced fertile seeds through many generations upon self-fertilisation, plants also missing the functional telomerase (double mutants), rapidly, within three generations, displayed severe developmental defects. Cytogenetic inspection of cycling somatic cells revealed a very early onset of massive genome instability. Molecular methods used for examining the length of telomeres in double homozygous mutants detected much faster telomere shortening than in plants deficient in telomerase gene alone. CONCLUSIONS Our findings suggest that NBS1 acts in concert with telomerase and plays a profound role in plant telomere renewal.
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Affiliation(s)
- Lucie Najdekrova
- Department of Plant Developmental Genetics, Institute of Biophysics of the Czech Academy of Sciences, Kralovopolska 135, Brno, 61265, Czech Republic
| | - Jiri Siroky
- Department of Plant Developmental Genetics, Institute of Biophysics of the Czech Academy of Sciences, Kralovopolska 135, Brno, 61265, Czech Republic
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15
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Huang M, Li H, Zhang L, Gao F, Wang P, Hu Y, Yan S, Zhao L, Zhang Q, Tan J, Liu X, He S, Li L. Plant 45S rDNA clusters are fragile sites and their instability is associated with epigenetic alterations. PLoS One 2012; 7:e35139. [PMID: 22509394 PMCID: PMC3324429 DOI: 10.1371/journal.pone.0035139] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2011] [Accepted: 03/08/2012] [Indexed: 12/14/2022] Open
Abstract
Our previous study demonstrated that 45S ribosomal DNA (45S rDNA) clusters were chromosome fragile sites expressed spontaneously in Lolium. In this study, fragile phenotypes of 45S rDNA were observed under aphidicolin (APH) incubation in several plant species. Further actinomycin D (ActD) treatment showed that transcriptional stress might interfere with chromatin packaging, resulting in 45S rDNA fragile expression. These data identified 45S rDNA sites as replication-dependent as well as transcription-dependent fragile sites in plants. In the presence of ActD, a dramatic switch to an open chromatin conformation and accumulated incomplete 5′ end of the external transcribed spacer (5′ETS) transcripts were observed, accompanied by decreased DNA methylation, decreased levels of histone H3, and increased histone acetylation and levels of H3K4me2, suggesting that these epigenetic alterations are associated with failure of 45S rDNA condensation. Furthermore, the finding that γ-H2AX was accumulated at 45S rDNA sites following ActD treatment suggested that the DNA damage signaling pathway was associated with the appearance of 45S rDNA fragile phenotypes. Our data provide a link between 45S rDNA transcription and chromatin-packaging defects and open the door for further identifying the molecular mechanism involved.
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Affiliation(s)
- Min Huang
- State Key Laboratory of Hybrid Rice, College of Life Sciences, Wuhan University, Wuhan, China
| | - Hui Li
- State Key Laboratory of Hybrid Rice, College of Life Sciences, Wuhan University, Wuhan, China
| | - Lu Zhang
- State Key Laboratory of Hybrid Rice, College of Life Sciences, Wuhan University, Wuhan, China
| | - Fei Gao
- State Key Laboratory of Hybrid Rice, College of Life Sciences, Wuhan University, Wuhan, China
| | - Pu Wang
- State Key Laboratory of Hybrid Rice, College of Life Sciences, Wuhan University, Wuhan, China
| | - Yong Hu
- State Key Laboratory of Hybrid Rice, College of Life Sciences, Wuhan University, Wuhan, China
| | - Shihan Yan
- State Key Laboratory of Hybrid Rice, College of Life Sciences, Wuhan University, Wuhan, China
| | - Lin Zhao
- State Key Laboratory of Hybrid Rice, College of Life Sciences, Wuhan University, Wuhan, China
| | - Qi Zhang
- State Key Laboratory of Hybrid Rice, College of Life Sciences, Wuhan University, Wuhan, China
| | - Junjun Tan
- State Key Laboratory of Hybrid Rice, College of Life Sciences, Wuhan University, Wuhan, China
| | - Xincheng Liu
- State Key Laboratory of Hybrid Rice, College of Life Sciences, Wuhan University, Wuhan, China
| | - Shibin He
- State Key Laboratory of Hybrid Rice, College of Life Sciences, Wuhan University, Wuhan, China
| | - Lijia Li
- State Key Laboratory of Hybrid Rice, College of Life Sciences, Wuhan University, Wuhan, China
- * E-mail:
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16
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Abstract
Critically shortened telomeres can be subjected to DNA repair events that generate end-to-end chromosome fusions. The resulting dicentric chromosomes can enter breakage-fusion-bridge cycles, thereby impeding elucidation of the structures of the initial fusion events and a mechanistic understanding of their genesis. Current models for the molecular basis of fusion of critically shortened, uncapped telomeres rely on PCR assays that typically capture fusion breakpoints created by direct ligation of chromosome ends. Here we use independent approaches that rely on distinctive features of Caenorhabditis elegans to study the frequency of direct end-to-end chromosome fusion in telomerase mutants: (1) holocentric chromosomes that allow for genetic isolation of stable end-to-end fusions and (2) unique subtelomeric sequences that allow for thorough PCR analysis of samples of genomic DNA harboring multiple end-to-end fusions. Surprisingly, only a minority of end-to-end fusion events resulted from direct end joining with no additional genome rearrangements. We also demonstrate that deficiency for the C. elegans Ku DNA repair heterodimer does not affect telomere length or cause synthetic effects in the absence of telomerase.
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17
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Riehs N, Akimcheva S, Puizina J, Bulankova P, Idol RA, Siroky J, Schleiffer A, Schweizer D, Shippen DE, Riha K. Arabidopsis SMG7 protein is required for exit from meiosis. J Cell Sci 2008; 121:2208-16. [PMID: 18544632 DOI: 10.1242/jcs.027862] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Meiosis consists of two nuclear divisions that are separated by a short interkinesis. Here we show that the SMG7 protein, which plays an evolutionarily conserved role in nonsense-mediated RNA decay (NMD) in animals and yeast, is essential for the progression from anaphase to telophase in the second meiotic division in Arabidopsis. Arabidopsis SMG7 is an essential gene, the disruption of which causes embryonic lethality. Plants carrying a hypomorphic smg7 mutation exhibit an elevated level of transcripts containing premature stop codons. This suggests that the role of SMG7 in NMD is conserved in plants. Furthermore, hypomorphic smg7 alleles render mutant plants sterile by causing an unusual cell-cycle arrest in anaphase II that is characterized by delayed chromosome decondensation and aberrant rearrangement of the meiotic spindle. The smg7 phenotype was mimicked by exposing meiocytes to the proteasome inhibitor MG115. Together, these data indicate that SMG7 counteracts cyclin-dependent kinase (CDK) activity at the end of meiosis, and reveal a novel link between SMG7 and regulation of the meiotic cell cycle.
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Affiliation(s)
- Nina Riehs
- Gregor Mendel Institute of Molecular Plant Biology, Austrian Academy of Sciences, Dr Bohr-Gasse 3, 1030 Vienna, Austria
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18
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Raskina O, Barber JC, Nevo E, Belyayev A. Repetitive DNA and chromosomal rearrangements: speciation-related events in plant genomes. Cytogenet Genome Res 2008; 120:351-7. [PMID: 18504364 DOI: 10.1159/000121084] [Citation(s) in RCA: 181] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/09/2007] [Indexed: 11/19/2022] Open
Abstract
Chromosomal change is one of the more hotly debated potential mechanisms of speciation. It has long been argued over whether--and to what degree--changes in chromosome structure contribute to reproductive isolation and, ultimately, speciation. In this review we do not aim to completely analyze accumulated data about chromosomal speciation but wish to draw attention to several critical points of speciation-related chromosomal change, namely: (a) interrelations between chromosomal rearrangements and repetitive DNA fraction; (b) mobility of ribosomal DNA clusters; and (c) rDNA and transposable elements as perpetual generators of genome instability.
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Affiliation(s)
- O Raskina
- Institute of Evolution, University of Haifa, Israel
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19
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Huang J, Ma L, Yang F, Fei SZ, Li L. 45S rDNA regions are chromosome fragile sites expressed as gaps in vitro on metaphase chromosomes of root-tip meristematic cells in Lolium spp. PLoS One 2008; 3:e2167. [PMID: 18478113 PMCID: PMC2366065 DOI: 10.1371/journal.pone.0002167] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2008] [Accepted: 03/26/2008] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND In humans, chromosome fragile sites are regions that are especially prone to forming non-staining gaps, constrictions or breaks in one or both of the chromatids on metaphase chromosomes either spontaneously or following partial inhibition of DNA synthesis and have been well identified. So far, no plant chromosome fragile sites similar to those in human chromosomes have been reported. METHODS AND RESULTS During the course of cytological mapping of rDNA on ryegrass chromosomes, we found that the number of chromosomes plus chromosome fragments was often more than the expected 14 in most cells for Lolium perenne L. cv. Player by close cytological examination using a routine chromosome preparation procedure. Further fluorescent in situ hybridization (FISH) using 45S rDNA as a probe indicated that the root-tip cells having more than a 14-chromosome plus chromosome fragment count were a result of chromosome breakage or gap formation in vitro (referred to as chromosome lesions) at 45S rDNA sites, and 86% of the cells exhibited chromosome breaks or gaps and all occurred at the sites of 45S rDNA in Lolium perenne L. cv. Player, as well as in L. multiflorum Lam. cv. Top One. Chromatin depletion or decondensation occurred at various locations within the 45S rDNA regions, suggesting heterogeneity of lesions of 45S rDNA sites with respect to their position within the rDNA region. CONCLUSIONS The chromosome lesions observed in this study are very similar cytologically to that of fragile sites observed in human chromosomes, and thus we conclude that the high frequency of chromosome lesions in vitro in Lolium species is the result of the expression of 45S rDNA fragile sites. Possible causes for the spontaneous expression of fragile sites and their potential biological significance are discussed.
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Affiliation(s)
- Jing Huang
- Key Laboratory of Ministry of Education (MOE) for Plant Development Biology, College of Life Sciences, Wuhan University, Wuhan, China
| | - Lu Ma
- Key Laboratory of Ministry of Education (MOE) for Plant Development Biology, College of Life Sciences, Wuhan University, Wuhan, China
| | - Fei Yang
- Key Laboratory of Ministry of Education (MOE) for Plant Development Biology, College of Life Sciences, Wuhan University, Wuhan, China
| | - Shui-zhang Fei
- Department of Horticulture and Interdepartmental Plant Physiology and Molecular Biology, Iowa State University, Ames, Iowa, United States of America
| | - Lijia Li
- Key Laboratory of Ministry of Education (MOE) for Plant Development Biology, College of Life Sciences, Wuhan University, Wuhan, China
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20
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Růcková E, Friml J, Procházková Schrumpfová P, Fajkus J. Role of alternative telomere lengthening unmasked in telomerase knock-out mutant plants. PLANT MOLECULAR BIOLOGY 2008; 66:637-46. [PMID: 18239859 DOI: 10.1007/s11103-008-9295-7] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/23/2007] [Accepted: 01/14/2008] [Indexed: 05/23/2023]
Abstract
Telomeres in many eukaryotes are maintained by telomerase in whose absence telomere shortening occurs. However, telomerase-deficient Arabidopsis thaliana mutants (Attert (-/-)) show extremely low rates of telomere shortening per plant generation (250-500 bp), which does not correspond to the expected outcome of replicative telomere shortening resulting from ca. 1,000 meristem cell divisions per seed-to-seed generation. To investigate the influence of the number of cell divisions per seed-to-seed generation, Attert (-/-) mutant plants were propagated from seeds coming either from the lower-most or the upper-most siliques (L- and U-plants) and the length of their telomeres were followed over several generations. The rate of telomere shortening was faster in U-plants, than in L-plants, as would be expected from their higher number of cell divisions per generation. However, this trend was observed only in telomeres whose initial length is relatively high and the differences decreased with progressive general telomere shortening over generations. But in generation 4, the L-plants frequently show a net telomere elongation, while the U-plants fail to do so. We propose that this is due to the activation of alternative telomere lengthening (ALT), a process which is activated in early embryonic development in both U- and L-plants, but is overridden in U-plants due to their higher number of cell divisions per generation. These data demonstrate what so far has only been speculated, that in the absence of telomerase, the number of cell divisions within one generation influences the control of telomere lengths. These results also reveal a fast and efficient activation of ALT mechanism(s) in response to the loss of telomerase activity and imply that ALT is probably involved also in normal plant development.
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Affiliation(s)
- Eva Růcková
- Department of Functional Genomics and Proteomics, Faculty of Science, Masaryk University, Building A2-ILBIT, Kamenice 5, 625 00 Brno, Czech Republic
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21
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Bi K, Bogart JP, Fu J. Genealogical relationships of southern Ontario polyploid unisexual salamanders (genus Ambystoma) inferred from intergenomic exchanges and major rDNA cytotypes. Chromosome Res 2008; 16:275-89. [DOI: 10.1007/s10577-007-1192-4] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2007] [Revised: 11/28/2007] [Accepted: 11/28/2007] [Indexed: 11/30/2022]
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22
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Siroky J. Chromosome landmarks as tools to study the genome of Arabidopsis thaliana. Cytogenet Genome Res 2008; 120:202-9. [DOI: 10.1159/000121068] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/17/2007] [Indexed: 12/17/2022] Open
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23
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Gernand D, Golczyk H, Rutten T, Ilnicki T, Houben A, Joachimiak AJ. Tissue culture triggers chromosome alterations, amplification, and transposition of repeat sequences in Allium fistulosum. Genome 2007; 50:435-42. [PMID: 17612612 DOI: 10.1139/g07-023] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Structural alterations in nuclei and chromosomes of cells derived from callus culture of Allium fistulosum have been studied with fluorescent in situ hybridization (FISH) using 5S ribosomal DNA (rDNA), 45S rDNA, and 375-bp repeat probes. A high frequency of chromosome abnormalities was found to be caused by the loss of telomere-located 375-bp repeats, chromosome fusion, and subsequent breakage-fusion-bridge cycles. Products of chromosome fusions and monocentric and regularly shaped chromosomes showed additional 375-bp repeat and 45S rDNA clusters at unusual sites, suggesting dynamic copy-number changes and transposition of these repeats. Southern hybridization revealed no differences in the 375-bp repeat and 45S rDNA repeat array order or the degree of methylation between DNA isolated from leaves or tissue-culture cells. In addition, protruding, spike-like structures positive for 375-bp repeats were identified on the surface of different-sized nuclei. Transmission electron microscopy analysis revealed the accumulation of densely packed chromatin within spike-like structures. Because root calyptra cells showed similar structures, it is likely that heterochromatic spike-like structures are a feature of nondividing cells at the onset of programmed cell death.
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Affiliation(s)
- Dorota Gernand
- Leibniz-Institute of Plant Genetics and Crop Plant Research (IPK), 06466 Gatersleben, Germany
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24
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Juchimiuk J, Hering B, Maluszynska J. Multicolour FISH in an analysis of chromosome aberrations induced by N-nitroso-N-methylurea and maleic hydrazide in barley cells. J Appl Genet 2007; 48:99-106. [PMID: 17495342 DOI: 10.1007/bf03194666] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
The present study is a rare example of a detailed characterization of chromosomal aberrations by identification of individual chromosomes (or chromosome arms) involved in their formation in plant cells by using fluorescent in situ hybridization (FISH). In addition, the first application of more than 2 DNA probes in FISH experiments in order to analyse chromosomal aberrations in plant cells is presented. Simultaneous FISH with 5S and 25S rDNA and, after reprobing of preparations, telomeric and centromeric DNA sequences as probes, were used to compare the cytogenetic effects of 2 chemical mutagens: N-nitroso-N-methylurea (MNU) and maleic hydrazide (MH) on root tip meristem cells of Hordeum vulgare (2n=14). The micronucleus (MN) test combined with FISH allowed the quantitative analysis of the involvement of specific chromosome fragments in micronuclei formation and thus enabled the possible origin of mutagen-induced micronuclei to be explained. Terminal deletions were most frequently caused by MH and MNU. The analysis of the frequency of micronuclei with signals of the investigated DNA probes showed differences between the frequency of MH- and MNU-induced micronuclei with specific signals. The micronuclei with 2 signals, telomeric DNA and rDNA (5S and/or 25S rDNA), were the most frequently observed in the case of both mutagens, but with a higher frequency after treatment with MH (46%) than MNU (37%). Also, 10% of MH-induced micronuclei were characterized by the presence of only telomere DNA sequences, whereas there were almost 3-fold more in the case of MNU-induced micronuclei (28%). Additionally, by using FISH with the same probes, an attempt was made to identify the origin of chromosome fragments in mitotic anaphase.
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Affiliation(s)
- Jolanta Juchimiuk
- Department of Plant Anatomy and Cytology, University of Silesia, Jagiellonska 28, 40-032 Katowice, Poland.
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25
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Schranz ME, Windsor AJ, Song BH, Lawton-Rauh A, Mitchell-Olds T. Comparative genetic mapping in Boechera stricta, a close relative of Arabidopsis. PLANT PHYSIOLOGY 2007; 144:286-98. [PMID: 17369426 PMCID: PMC1913784 DOI: 10.1104/pp.107.096685] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/29/2007] [Accepted: 02/28/2007] [Indexed: 05/14/2023]
Abstract
The angiosperm family Brassicaceae contains both the research model Arabidopsis (Arabidopsis thaliana) and the agricultural genus Brassica. Comparative genomics in the Brassicaceae has largely focused on direct comparisons between Arabidopsis and the species of interest. However, the reduced genome size and chromosome number (n = 5) of Arabidopsis complicates comparisons. Arabidopsis shows extensive genome and chromosome reshuffling compared to its close relatives Arabidopsis lyrata and Capsella rubella, both with n = 8. To facilitate comparative genomics across the Brassicaceae we recently outlined a system of 24 conserved chromosomal blocks based on their positions in an ancestral karyotype of n = 8, rather than by their position in Arabidopsis. In this report we use this system as a tool to understand genome structure and evolution in Boechera stricta (n = 7). B. stricta is a diploid, sexual, and highly self-fertilizing species occurring in mostly montane regions of western North America. We have created an F(2) genetic map of B. stricta based on 192 individuals scored at 196 microsatellite and candidate gene loci. Single-nucleotide polymorphism genotyping of 94 of the loci was done simultaneously using an Illumina bead array. The total map length is 725.8 cM, with an average marker spacing of 3.9 cM. There are no gaps greater than 19.3 cM. The chromosomal reduction from n = 8 to n = 7 and other genomic changes in B. stricta likely involved a pericentric inversion, a chromosomal fusion, and two reciprocal translocations that are easily visualized using the genomic blocks. Our genetic map will facilitate the analysis of ecologically relevant quantitative variation in Boechera. Sequence data from this article can be found in the GenBank/EMBL data libraries under accession numbers DU 667459 to DU 708532.
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Affiliation(s)
- M Eric Schranz
- Department of Biology, Duke University, Durham, NC 27708, USA.
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26
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Mokros P, Vrbsky J, Siroky J. Identification of chromosomal fusion sites in Arabidopsis mutants using sequential bicolour BAC-FISH. Genome 2007; 49:1036-42. [PMID: 17036078 DOI: 10.1139/g06-082] [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] [Indexed: 11/22/2022]
Abstract
Double stranded chromosomal breaks are repaired by homologous recombination or nonhomologous end joining (NHEJ). When broken chromosome ends are fused together by NHEJ, the resulting dicentric chromosomes can be detected as anaphase bridges during the subsequent mitosis. Telomeres in the absence of functional telomerase shorten, became unprotected, and are eventually recognized by the cell repair system as double stranded breaks. As result, chromosomes of Arabidopsis thaliana plants that are deficient in the gene for telomerase reverse transcriptase (TERT) are prone to chromosome fusions. We use Arabidopsis tert-/- mutants as a model system for analyzing terminal chromosome fusions. Here we report a novel and sensitive cytogenetic assay for the identification and characterization of chromosome-terminal fusion events by employing fluorescence in situ hybridization (FISH) with multiple probes and a repeated hybridization approach. A mixture of chromosome-specific subtelomeric probes is applied successively in 3 FISH reactions to the slides containing mitotic anaphase figures with anaphase bridges. Each figure is registered by a CCD camera after each in situ hybridization procedure. By comparing the signals presented on the bridge in successive images the assessment of the particular chromosome arms involved in fusion is possible. This experimental setup enables unambiguous identification of individual chromosome ends employed in fusion events.
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Affiliation(s)
- Petr Mokros
- Laboratory of Plant Developmental Genetics, Institute of Biophysics, Academy Sciences of the Czech Republic, Brno, Czech Republic
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27
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Nicolas SD, Le Mignon G, Eber F, Coriton O, Monod H, Clouet V, Huteau V, Lostanlen A, Delourme R, Chalhoub B, Ryder CD, Chèvre AM, Jenczewski E. Homeologous recombination plays a major role in chromosome rearrangements that occur during meiosis of Brassica napus haploids. Genetics 2006; 175:487-503. [PMID: 17151256 PMCID: PMC1800630 DOI: 10.1534/genetics.106.062968] [Citation(s) in RCA: 86] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
Chromosomal rearrangements can be triggered by recombination between distinct but related regions. Brassica napus (AACC; 2n = 38) is a recent allopolyploid species whose progenitor genomes are widely replicated. In this article, we analyze the extent to which chromosomal rearrangements originate from homeologous recombination during meiosis of haploid B. napus (n = 19) by genotyping progenies of haploid x euploid B. napus with molecular markers. Our study focuses on three pairs of homeologous regions selected for their differing levels of divergence (N1/N11, N3/N13, and N9/N18). We show that a high number of chromosomal rearrangements occur during meiosis of B. napus haploid and are transmitted by first division restitution (FDR)-like unreduced gametes to their progeny; half of the progeny of Darmor-bzh haploids display duplications and/or losses in the chromosomal regions being studied. We demonstrate that half of these rearrangements are due to recombination between regions of primary homeology, which represents a 10- to 100-fold increase compared to the frequency of homeologous recombination measured in euploid lines. Some of the other rearrangements certainly result from recombination between paralogous regions because we observed an average of one to two autosyndetic A-A and/or C-C bivalents at metaphase I of the B. napus haploid. These results are discussed in the context of genome evolution of B. napus.
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Affiliation(s)
- Stéphane D Nicolas
- UMR INRA-Agrocampus Rennes, Amélioration des Plantes et Biotechnologies Végétales, 35653 Le Rheu, France
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Lysak MA, Berr A, Pecinka A, Schmidt R, McBreen K, Schubert I. Mechanisms of chromosome number reduction in Arabidopsis thaliana and related Brassicaceae species. Proc Natl Acad Sci U S A 2006; 103:5224-9. [PMID: 16549785 PMCID: PMC1458822 DOI: 10.1073/pnas.0510791103] [Citation(s) in RCA: 252] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2005] [Indexed: 11/18/2022] Open
Abstract
Evolution of chromosome complements can be resolved by genome sequencing, comparative genetic mapping, and comparative chromosome painting. Previously, comparison of genetic maps and gene-based phylogenies suggested that the karyotypes of Arabidopsis thaliana (n = 5) and of related species with six or seven chromosome pairs were derived from an ancestral karyotype with eight chromosome pairs. To test this hypothesis, we applied multicolor chromosome painting using contiguous bacterial artificial chromosome pools of A. thaliana arranged according to the genetic maps of Arabidopsis lyrata and Capsella rubella (both n = 8) to A. thaliana, A. lyrata, Neslia paniculata, Turritis glabra, and Hornungia alpina. This approach allowed us to map the A. lyrata centromeres as a prerequisite to defining a putative ancestral karyotype (n = 8) and to elucidate the evolutionary mechanisms that shaped the karyotype of A. thaliana and its relatives. We conclude that chromosome "fusions" in A. thaliana resulted from (i) generation of acrocentric chromosomes by pericentric inversions, (ii) reciprocal translocation between two chromosomes (one or both acrocentric), and (iii) elimination of a minichromosome that arose in addition to the "fusion chromosome." Comparative chromosome painting applied to N. paniculata (n = 7), T. glabra (n = 6), and H. alpina (n = 6), for which genetic maps are not available, revealed chromosomal colinearity between all species tested and allowed us to reconstruct the evolution of their chromosomes from a putative ancestral karyotype (n = 8). Although involving different ancestral chromosomes, chromosome number reduction followed similar routes as found within the genus Arabidopsis.
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Affiliation(s)
- Martin A Lysak
- Jodrell Laboratory, Royal Botanic Gardens, Kew, Richmond TW9 3AB, United Kingdom.
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Cheung I, Schertzer M, Rose A, Lansdorp PM. High incidence of rapid telomere loss in telomerase-deficient Caenorhabditis elegans. Nucleic Acids Res 2006; 34:96-103. [PMID: 16407328 PMCID: PMC1326242 DOI: 10.1093/nar/gkj417] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Telomerase is essential to maintain telomere length in most eukaryotes. Other functions for telomerase have been proposed but molecular mechanisms remain unclear. We studied Caenorhabditis elegans with a mutation in the trt-1 telomerase reverse transcriptase gene. Mutant animals showed a progressive decrease in brood size and typically failed to reproduce after five generations. Using PCR analysis to measure the length of individual telomere repeat tracks on the left arm of chromosome V we observed that trt-1 mutants lost ∼125bp of telomeric DNA per generation. Chromosome fusions involving complex recombination reactions were observed in late generations. Strikingly, trt-1 mutant animals displayed a high frequency of telomeres with many fewer repeats than average. Such outlying short telomeres were not observed in mrt-2 mutants displaying progressive telomere loss very similar to trt-1 mutants. We speculate that, apart from maintaining the average telomere length, telomerase is required to prevent or repair sporadic telomere truncations that are unrelated to the typical ‘end-replication’ problems.
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Affiliation(s)
- Iris Cheung
- Terry Fox Laboratory, BC Cancer AgencyAvenue, Vancouver, BC, Canada V5Z 1L3
- Department of Medical Genetics, University of British ColumbiaVancouver, BC, Canada V6T 1Z3
| | - Michael Schertzer
- Terry Fox Laboratory, BC Cancer AgencyAvenue, Vancouver, BC, Canada V5Z 1L3
| | - Ann Rose
- Department of Medical Genetics, University of British ColumbiaVancouver, BC, Canada V6T 1Z3
| | - Peter M. Lansdorp
- Terry Fox Laboratory, BC Cancer AgencyAvenue, Vancouver, BC, Canada V5Z 1L3
- Department of Medicine, University of British ColumbiaVancouver, BC, Canada V5Z 4E3
- To whom correspondence should be addressed. Tel: +1 604 675 8135; Fax: +1 604 877 0712;
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Watson JM, Bulankova P, Riha K, Shippen DE, Vyskot B. Telomerase-independent cell survival in Arabidopsis thaliana. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2005; 43:662-74. [PMID: 16115064 DOI: 10.1111/j.1365-313x.2005.02479.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Telomerase is the reverse transcriptase responsible for the maintenance of telomeric repeat sequences in most species that have been studied. Inactivation of telomerase causes telomere shortening and results in the loss of the telomere's protective function, which in mammals leads to cell-cycle arrest and apoptosis. Experiments performed on Arabidopsis thaliana mutants lacking telomerase activity revealed their unusually high tolerance for genome instability. Here we present molecular and cytogenetic analysis of two cell lines (A and B) derived from seeds of late-generation telomerase-deficient A. thaliana. These cultures have survived for about 3 years and are still viable. However, neither culture has adapted mechanisms to maintain terminal telomeric repeats. One culture (B) suffers from severe growth irregularities and a high degree of mortality. Karyological analysis revealed dramatic genomic rearrangements, a large variation in ploidy, and an extremely high percentage of anaphase bridges. The second cell line (A) survived an apparent crisis and phenotypically appears wild-type with respect to growth and morphology. Despite these indications of genome stabilization, a high percentage of anaphase bridges was observed in the A line. We conclude that the restructured chromosome termini provide the A line with partial protection from end-joining repair activities, thus allowing normal growth.
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Affiliation(s)
- J Matthew Watson
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas 77843-3258, USA
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Abstract
This paper examines telomeres from an evolutionary perspective. In the monocot plant order Asparagales two evolutionary switch-points in telomere sequence are known. The first occurred when the Arabidopsis-type telomere was replaced by a telomere based on a repeat motif more typical of vertebrates. The replacement is associated with telomerase activity, but the telomerase has low fidelity and this may have implications for the binding of telomeric proteins. At the second evolutionary switch-point, the telomere and its mode of synthesis are replaced by an unknown mechanism. Elsewhere in plants (Sessia, Vestia, Cestrum) and in arthropods, the telomere "typical" of the group is lost. Probably many other groups with "unusual" telomeres will be found. We question whether telomerase is indeed the original end-maintenance system and point to other candidate processes involving t-loops, t-circles, rolling circle replication and recombination. Possible evolutionary outcomes arising from the loss of telomerase activity in alternative lengthening of telomere (ALT) systems are discussed. We propose that elongation of minisatellite repeats using recombination/replication processes initially substitutes for the loss of telomerase function. Then in more established ALT groups, subtelomeric satellite repeats may replace the telomeric minisatellite repeat whilst maintaining the recombination/replication mechanisms for telomere elongation. Thereafter a retrotransposition-based end-maintenance system may become established. The influence of changing sequence motifs on the properties of the telomere cap is discussed. The DNA and protein components of telomeres should be regarded--as with any other chromosome elements--as evolving and co-evolving over time and responding to changes in the genome and to environmental stresses. We describe how telomere dysfunction, resulting in end-to-end chromosome fusions, can have a profound effect on chromosome evolution and perhaps even speciation.
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Affiliation(s)
- Jirí Fajkus
- Laboratory of Functional Genomics and Proteomics, Faculty of Science, Masaryk University Brno, Královopolská 135, CZ-61265 Brno, Czech Republic.
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Heacock M, Spangler E, Riha K, Puizina J, Shippen DE. Molecular analysis of telomere fusions in Arabidopsis: multiple pathways for chromosome end-joining. EMBO J 2004; 23:2304-13. [PMID: 15141167 PMCID: PMC419913 DOI: 10.1038/sj.emboj.7600236] [Citation(s) in RCA: 138] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2004] [Accepted: 04/21/2004] [Indexed: 11/09/2022] Open
Abstract
End-to-end fusion of critically shortened telomeres in higher eucaryotes is presumed to be mediated by nonhomologous end-joining (NHEJ). Here we describe two PCR-based methods to monitor telomere length and examine the fate of dysfunctional telomeres in Arabidopsis lacking the catalytic subunit of telomerase (TERT) and the DNA repair proteins Ku70 and Mre11. Primer extension telomere repeat amplification relies on the presence of an intact G-overhang, and thus measures functional telomere length. The minimum functional telomere length detected was 300-400 bp. PCR amplification and sequence analysis of chromosome fusion junctions revealed exonucleolytic digestion of dysfunctional ends prior to fusion. In ku70 tert mutants, there was a greater incidence of microhomology at the fusion junction than in tert mutants. In triple ku70 tert mre11 mutants, chromosome fusions were still detected, but microhomology at the junction was no longer favored. These data indicate that both Ku70 and Mre11 contribute to fusion of critically shortened telomeres in higher eucaryotes. Furthermore, Arabidopsis processes critically shortened telomeres as double-strand breaks, using a variety of end-joining pathways.
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Affiliation(s)
- Michelle Heacock
- Department of Biochemistry and Biophysics, Texas A&M University, TAMU, College Station, TX, USA
| | - Elizabeth Spangler
- Department of Biochemistry and Biophysics, Texas A&M University, TAMU, College Station, TX, USA
- Department of Veterinary Pathobiology, Texas A&M University, College Station, TX, USA
| | - Karel Riha
- Gregor Mendel Institute of Molecular Plant Biology, Austrian Academy of Sciences Rennweg 14, Vienna, Austria
| | - Jasna Puizina
- Gregor Mendel Institute of Molecular Plant Biology, Austrian Academy of Sciences Rennweg 14, Vienna, Austria
| | - Dorothy E Shippen
- Department of Biochemistry and Biophysics, Texas A&M University, TAMU, College Station, TX, USA
- Department of Biochemistry and Biophysics, Texas A&M University, 2128 TAMU, College Station, TX 77843-2128, USA. Tel.: +1 979 862 2342; Fax: +1 979 845 9274; E-mail:
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Lengerova M, Kejnovsky E, Hobza R, Macas J, Grant SR, Vyskot B. Multicolor FISH mapping of the dioecious model plant, Silene latifolia. TAG. THEORETICAL AND APPLIED GENETICS. THEORETISCHE UND ANGEWANDTE GENETIK 2004; 108:1193-9. [PMID: 14727034 DOI: 10.1007/s00122-003-1568-6] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/02/2003] [Accepted: 12/04/2003] [Indexed: 05/18/2023]
Abstract
Silene latifolia is a key plant model in the study of sex determination and sex chromosome evolution. Current studies have been based on genetic mapping of the sequences linked to sex chromosomes with analysis of their characters and relative positions on the X and Y chromosomes. Until recently, very few DNA sequences have been physically mapped to the sex chromosomes of S. latifolia. We have carried out multicolor fluorescent in situ hybridization (FISH) analysis of S. latifolia chromosomes based on the presence and intensity of FISH signals on individual chromosomes. We have generated new markers by constructing and screening a sample bacterial artificial chromosome (BAC) library for appropriate FISH probes. Five newly isolated BAC clones yielded discrete signals on the chromosomes: two were specific for one autosome pair and three hybridized preferentially to the sex chromosomes. We present the FISH hybridization patterns of these five BAC inserts together with previously described repetitive sequences (X-43.1, 25S rDNA and 5S rDNA) and use them to analyze the S. latifolia karyotype. The autosomes of S. latifolia are difficult to distinguish based on their relative arm lengths. Using one BAC insert and the three repetitive sequences, we have constructed a standard FISH karyotype that can be used to distinguish all autosome pairs. We also analyze the hybridization patterns of these sequences on the sex chromosomes and discuss the utility of the karyotype mapping strategy presented to study sex chromosome evolution and Y chromosome degeneration.
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Affiliation(s)
- M Lengerova
- Institute of Biophysics, Academy of Sciences of the Czech Republic, Kralovopolska 135, 612 65 Brno, Czech Republic
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