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Schmidt N, Sielemann K, Breitenbach S, Fuchs J, Pucker B, Weisshaar B, Holtgräwe D, Heitkam T. Repeat turnover meets stable chromosomes: repetitive DNA sequences mark speciation and gene pool boundaries in sugar beet and wild beets. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2024; 118:171-190. [PMID: 38128038 DOI: 10.1111/tpj.16599] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/09/2023] [Revised: 12/05/2023] [Accepted: 12/08/2023] [Indexed: 12/23/2023]
Abstract
Sugar beet and its wild relatives share a base chromosome number of nine and similar chromosome morphologies. Yet, interspecific breeding is impeded by chromosome and sequence divergence that is still not fully understood. Since repetitive DNAs are among the fastest evolving parts of the genome, we investigated, if repeatome innovations and losses are linked to chromosomal differentiation and speciation. We traced genome and chromosome-wide evolution across 13 beet species comprising all sections of the genera Beta and Patellifolia. For this, we combined short and long read sequencing, flow cytometry, and cytogenetics to build a comprehensive framework that spans the complete scale from DNA to chromosome to genome. Genome sizes and repeat profiles reflect the separation into three gene pools with contrasting evolutionary patterns. Among all repeats, satellite DNAs harbor most genomic variability, leading to fundamentally different centromere architectures, ranging from chromosomal uniformity in Beta and Patellifolia to the formation of patchwork chromosomes in Corollinae/Nanae. We show that repetitive DNAs are causal for the genome expansions and contractions across the beet genera, providing insights into the genomic underpinnings of beet speciation. Satellite DNAs in particular vary considerably between beet genomes, leading to the evolution of distinct chromosomal setups in the three gene pools, likely contributing to the barriers in beet breeding. Thus, with their isokaryotypic chromosome sets, beet genomes present an ideal system for studying the link between repeats, genomic variability, and chromosomal differentiation and provide a theoretical fundament for understanding barriers in any crop breeding effort.
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Affiliation(s)
- Nicola Schmidt
- Faculty of Biology, Technische Universität Dresden, 01069, Dresden, Germany
| | - Katharina Sielemann
- Genetics and Genomics of Plants, Center for Biotechnology (CeBiTec) & Faculty of Biology, Bielefeld University, 33615, Bielefeld, Germany
- Graduate School DILS, Bielefeld Institute for Bioinformatics Infrastructure (BIBI), Bielefeld University, 33615, Bielefeld, Germany
| | - Sarah Breitenbach
- Faculty of Biology, Technische Universität Dresden, 01069, Dresden, Germany
| | - Jörg Fuchs
- Leibniz Institute of Plant Genetics and Crop Plant Research (IPK) Gatersleben, 06466, Stadt Seeland, Germany
| | - Boas Pucker
- Plant Biotechnology and Bioinformatics, Institute of Plant Biology & Braunschweig Integrated Centre of Systems Biology (BRICS), TU Braunschweig, 38106, Braunschweig, Germany
| | - Bernd Weisshaar
- Genetics and Genomics of Plants, Center for Biotechnology (CeBiTec) & Faculty of Biology, Bielefeld University, 33615, Bielefeld, Germany
| | - Daniela Holtgräwe
- Genetics and Genomics of Plants, Center for Biotechnology (CeBiTec) & Faculty of Biology, Bielefeld University, 33615, Bielefeld, Germany
| | - Tony Heitkam
- Faculty of Biology, Technische Universität Dresden, 01069, Dresden, Germany
- Institute of Biology, NAWI Graz, Karl-Franzens-Universität, A-8010 Graz, Graz, Austria
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2
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Islam-Faridi N, Hodnett GL, Zhebentyayeva T, Georgi LL, Sisco PH, Hebard FV, Nelson CD. Cyto-molecular characterization of rDNA and chromatin composition in the NOR-associated satellite in Chestnut (Castanea spp.). Sci Rep 2024; 14:980. [PMID: 38225361 PMCID: PMC10789788 DOI: 10.1038/s41598-023-45879-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2022] [Accepted: 10/25/2023] [Indexed: 01/17/2024] Open
Abstract
The American chestnut (Castanea dentata, 2n = 2x = 24), once known as the "King of the Appalachian Forest", was decimated by chestnut blight during the first half of the twentieth century by an invasive fungus (Cryphonectria parasitica). The Chinese chestnut (C. mollissima, 2n = 2x = 24), in contrast to American chestnut, is resistant to this blight. Efforts are being made to transfer this resistance to American chestnut through backcross breeding and genetic engineering. Both chestnut genomes have been genetically mapped and recently sequenced to facilitate gene discovery efforts aimed at assisting molecular breeding and genetic engineering. To complement and extend this genomic work, we analyzed the distribution and organization of their ribosomal DNAs (35S and 5S rDNA), and the chromatin composition of the nucleolus organizing region (NOR)-associated satellites. Using fluorescent in situ hybridization (FISH), we have identified two 35S (one major and one minor) and one 5S rDNA sites. The major 35S rDNA sites are terminal and sub-terminal in American and Chinese chestnuts, respectively, originating at the end of the short arm of the chromosome, extending through the secondary constriction and into the satellites. An additional 5S locus was identified in certain Chinese chestnut accessions, and it was linked distally to the major 35S site. The NOR-associated satellite in Chinese chestnut was found to comprise a proximal region packed with 35S rDNA and a distinct distal heterochromatic region. In contrast, the American chestnut satellite was relatively small and devoid of the distal heterochromatic region.
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Affiliation(s)
- Nurul Islam-Faridi
- Forest Tree Molecular Cytogenetics Laboratory, Southern Institute of Forest Genetics, USDA Forest Service, Southern Research Station, Texas A&M University, College Station, TX, 77843, USA.
| | - George L Hodnett
- Department of Soil and Crop Sciences, Texas A&M University, College Station, TX, 77843, USA
| | - Tetyana Zhebentyayeva
- The Schatz Center for Tree Molecular Genetics, Department of Ecosystem Science and Management, The Pennsylvania State University, University Park, PA, 16802, USA
- Department of Forestry and Natural Resources, University of Kentucky, Lexington, KY, 40546, USA
| | - Laura L Georgi
- Meadowview Research Farms, The American Chestnut Foundation, 29010 Hawthorne Drive, Meadowview, VA, 24361, USA
| | - Paul H Sisco
- The American Chestnut Foundation, 50 North Merrimon Ave., Suite 115, Asheville, NC, 28804, USA
| | - Frederick V Hebard
- Meadowview Research Farms, The American Chestnut Foundation, 29010 Hawthorne Drive, Meadowview, VA, 24361, USA
| | - C Dana Nelson
- USDA Forest Service, Southern Research Station, Forest Health Research and Education Center, Lexington, KY, 40546, USA
- USDA Forest Service, Southern Institute of Forest Genetics, Harrison Experimental Forest, 23332 Success Road, Saucier, MS, 39574, USA
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3
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Kumar A, Harloff HJ, Melzer S, Leineweber J, Defant B, Jung C. A rhomboid-like protease gene from an interspecies translocation confers resistance to cyst nematodes. THE NEW PHYTOLOGIST 2021; 231:801-813. [PMID: 33866563 DOI: 10.1111/nph.17394] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/18/2021] [Accepted: 04/01/2021] [Indexed: 05/10/2023]
Abstract
Plant-parasitic nematodes are severe pests in crop production worldwide. Chemical control of nematodes has been continuously reduced in recent decades owing to environmental and health concerns. Therefore, breeding nematode-resistant crops is an important aim if we are to secure harvests. The beet cyst nematode impairs root development and causes severe losses in sugar beet production. The only sources for resistance are distantly related wild species of the genus Patellifolia. Nematode resistance had been introduced into the beet genome via translocations from P. procumbens. We sequenced three translocations and identified the translocation breakpoints. By comparative sequence analysis of three translocations, we localized the resistance gene Hs4 within a region c. 230 kb in size. A candidate gene was characterized by CRISPR-Cas-mediated knockout and overexpression in susceptible roots. The gene encodes a rhomboid-like protease, which is predicted to be bound to the endoplasmic reticulum. Gene knockout resulted in complete loss of resistance, while overexpression caused resistance. The data confirm that the Hs4 gene alone protects against the pest. Thus, it constitutes a previously unknown mechanism of plants to combat parasitic nematodes. Its function in a nonrelated species suggests that the gene can confer resistance in crop species from different plant families.
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Affiliation(s)
- Avneesh Kumar
- Plant Breeding Institute, Christian-Albrechts-University of Kiel, Olshausenstrasse 40, Kiel, D-24098, Germany
| | - Hans-Joachim Harloff
- Plant Breeding Institute, Christian-Albrechts-University of Kiel, Olshausenstrasse 40, Kiel, D-24098, Germany
| | - Siegbert Melzer
- Plant Breeding Institute, Christian-Albrechts-University of Kiel, Olshausenstrasse 40, Kiel, D-24098, Germany
| | - Johanna Leineweber
- Plant Breeding Institute, Christian-Albrechts-University of Kiel, Olshausenstrasse 40, Kiel, D-24098, Germany
| | - Birgit Defant
- Plant Breeding Institute, Christian-Albrechts-University of Kiel, Olshausenstrasse 40, Kiel, D-24098, Germany
| | - Christian Jung
- Plant Breeding Institute, Christian-Albrechts-University of Kiel, Olshausenstrasse 40, Kiel, D-24098, Germany
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Orzechowska M, Majka M, Weiss-Schneeweiss H, Kovařík A, Borowska-Zuchowska N, Kolano B. Organization and evolution of two repetitive sequences, 18-24J and 12-13P, in the genome of Chenopodium (Amaranthaceae). Genome 2018; 61:643-652. [PMID: 30067084 DOI: 10.1139/gen-2018-0044] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
The abundance and chromosomal organization of two repetitive sequences named 12-13P and 18-24J were analyzed in 24 diploid and nine polyploid species of Chenopodium s.l., with special attention to Chenopodium s.s. Both sequences were predominantly present in species of Chenopodium s.s.; however, differences in the amplification levels were observed among the species. The 12-13P repeat was highly amplified in all of the analyzed Eurasian species, whereas the American diploids showed a marked variation in the amplification levels. The 12-13P repeat contains a tandemly arranged 40 bp minisatellite element forming a large proportion of the genome of Chenopodium (up to 3.5%). FISH revealed its localization to the pericentromeric regions of the chromosomes. The chromosomal distribution of 12-13P delivered additional chromosomal marker for B-genome diploids. The 18-24J repeat showed a dispersed organization in all of the chromosomes of the analyzed diploid species and the Eurasian tetraploids. In the American allotetraploids (C. quinoa, C. berlandieri) and Eurasian allohexaploids (e.g., C. album) very intense hybridization signals of 18-24J were observed only on 18 chromosomes that belong to the B subgenome of these polyploids. Combined cytogenetic and molecular analyses suggests that reorganization of these two repeats accompanied the diversification and speciation of diploid (especially A genome) and polyploid species of Chenopodium s.s.
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Affiliation(s)
- Maja Orzechowska
- a Department of Plant Anatomy and Cytology, University of Silesia, Jagiellonska 28,40-032 Katowice, Poland
| | - Maciej Majka
- a Department of Plant Anatomy and Cytology, University of Silesia, Jagiellonska 28,40-032 Katowice, Poland
| | - Hanna Weiss-Schneeweiss
- b Department of Botany and Biodiversity Research, University of Vienna, Rennweg 14, Vienna, Austria
| | - Ales Kovařík
- c Department of Molecular Epigenetics, Institute of Biophysics, Academy of Sciences of the Czech Republic, Královopolská 135, CZ-61265 Brno, Czech Republic
| | - Natalia Borowska-Zuchowska
- a Department of Plant Anatomy and Cytology, University of Silesia, Jagiellonska 28,40-032 Katowice, Poland
| | - Bozena Kolano
- a Department of Plant Anatomy and Cytology, University of Silesia, Jagiellonska 28,40-032 Katowice, Poland
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5
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Seijo G, Samoluk SS, Ortiz AM, Silvestri MC, Chalup L, Robledo G, Lavia GI. Cytological Features of Peanut Genome. COMPENDIUM OF PLANT GENOMES 2017. [DOI: 10.1007/978-3-319-63935-2_4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
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6
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Schmidt M, Hense S, Minoche AE, Dohm JC, Himmelbauer H, Schmidt T, Zakrzewski F. Cytosine methylation of an ancient satellite family in the wild beet Beta procumbens. Cytogenet Genome Res 2014; 143:157-67. [PMID: 24994030 DOI: 10.1159/000363485] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
DNA methylation is an essential epigenetic feature for the regulation and maintenance of heterochromatin. Satellite DNA is a repetitive sequence component that often occurs in large arrays in heterochromatin of subtelomeric, intercalary and centromeric regions. Knowledge about the methylation status of satellite DNA is important for understanding the role of repetitive DNA in heterochromatization. In this study, we investigated the cytosine methylation of the ancient satellite family pEV in the wild beet Beta procumbens. The pEV satellite is widespread in species-specific pEV subfamilies in the genus Beta and most likely originated before the radiation of the Betoideae and Chenopodioideae. In B. procumbens, the pEV subfamily occurs abundantly and spans intercalary and centromeric regions. To uncover its cytosine methylation, we performed chromosome-wide immunostaining and bisulfite sequencing of pEV satellite repeats. We found that CG and CHG sites are highly methylated while CHH sites show only low levels of methylation. As a consequence of the low frequency of CG and CHG sites and the preferential occurrence of most cytosines in the CHH motif in pEV monomers, this satellite family displays only low levels of total cytosine methylation.
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Affiliation(s)
- Martin Schmidt
- Department of Plant Cell and Molecular Biology, TU Dresden, Dresden, Germany
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7
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Čížková J, Hřibová E, Humplíková L, Christelová P, Suchánková P, Doležel J. Molecular analysis and genomic organization of major DNA satellites in banana (Musa spp.). PLoS One 2013; 8:e54808. [PMID: 23372772 PMCID: PMC3553004 DOI: 10.1371/journal.pone.0054808] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2012] [Accepted: 12/17/2012] [Indexed: 02/03/2023] Open
Abstract
Satellite DNA sequences consist of tandemly arranged repetitive units up to thousands nucleotides long in head-to-tail orientation. The evolutionary processes by which satellites arise and evolve include unequal crossing over, gene conversion, transposition and extra chromosomal circular DNA formation. Large blocks of satellite DNA are often observed in heterochromatic regions of chromosomes and are a typical component of centromeric and telomeric regions. Satellite-rich loci may show specific banding patterns and facilitate chromosome identification and analysis of structural chromosome changes. Unlike many other genomes, nuclear genomes of banana (Musa spp.) are poor in satellite DNA and the information on this class of DNA remains limited. The banana cultivars are seed sterile clones originating mostly from natural intra-specific crosses within M. acuminata (A genome) and inter-specific crosses between M. acuminata and M. balbisiana (B genome). Previous studies revealed the closely related nature of the A and B genomes, including similarities in repetitive DNA. In this study we focused on two main banana DNA satellites, which were previously identified in silico. Their genomic organization and molecular diversity was analyzed in a set of nineteen Musa accessions, including representatives of A, B and S (M. schizocarpa) genomes and their inter-specific hybrids. The two DNA satellites showed a high level of sequence conservation within, and a high homology between Musa species. FISH with probes for the satellite DNA sequences, rRNA genes and a single-copy BAC clone 2G17 resulted in characteristic chromosome banding patterns in M. acuminata and M. balbisiana which may aid in determining genomic constitution in interspecific hybrids. In addition to improving the knowledge on Musa satellite DNA, our study increases the number of cytogenetic markers and the number of individual chromosomes, which can be identified in Musa.
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Affiliation(s)
- Jana Čížková
- Institute of Experimental Botany, Centre of the Region Haná for Biotechnological and Agricultural Research, Olomouc, Czech Republic
| | - Eva Hřibová
- Institute of Experimental Botany, Centre of the Region Haná for Biotechnological and Agricultural Research, Olomouc, Czech Republic
| | - Lenka Humplíková
- Institute of Experimental Botany, Centre of the Region Haná for Biotechnological and Agricultural Research, Olomouc, Czech Republic
| | - Pavla Christelová
- Institute of Experimental Botany, Centre of the Region Haná for Biotechnological and Agricultural Research, Olomouc, Czech Republic
| | - Pavla Suchánková
- Institute of Experimental Botany, Centre of the Region Haná for Biotechnological and Agricultural Research, Olomouc, Czech Republic
| | - Jaroslav Doležel
- Institute of Experimental Botany, Centre of the Region Haná for Biotechnological and Agricultural Research, Olomouc, Czech Republic
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8
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Kolano B, Gardunia BW, Michalska M, Bonifacio A, Fairbanks D, Maughan PJ, Coleman CE, Stevens MR, Jellen EN, Maluszynska J. Chromosomal localization of two novel repetitive sequences isolated from the Chenopodium quinoa Willd. genome. Genome 2011; 54:710-7. [PMID: 21848446 DOI: 10.1139/g11-035] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The chromosomal organization of two novel repetitive DNA sequences isolated from the Chenopodium quinoa Willd. genome was analyzed across the genomes of selected Chenopodium species. Fluorescence in situ hybridization (FISH) analysis with the repetitive DNA clone 18-24J in the closely related allotetraploids C. quinoa and Chenopodium berlandieri Moq. (2n = 4x = 36) evidenced hybridization signals that were mainly present on 18 chromosomes; however, in the allohexaploid Chenopodium album L. (2n = 6x = 54), cross-hybridization was observed on all of the chromosomes. In situ hybridization with rRNA gene probes indicated that during the evolution of polyploidy, the chenopods lost some of their rDNA loci. Reprobing with rDNA indicated that in the subgenome labeled with 18-24J, one 35S rRNA locus and at least half of the 5S rDNA loci were present. A second analyzed sequence, 12-13P, localized exclusively in pericentromeric regions of each chromosome of C. quinoa and related species. The intensity of the FISH signals differed considerably among chromosomes. The pattern observed on C. quinoa chromosomes after FISH with 12-13P was very similar to GISH results, suggesting that the 12-13P sequence constitutes a major part of the repetitive DNA of C. quinoa.
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Affiliation(s)
- B Kolano
- Department of Plant Anatomy and Cytology, University of Silesia, Katowice, Poland.
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9
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Epigenetic profiling of heterochromatic satellite DNA. Chromosoma 2011; 120:409-22. [PMID: 21594600 DOI: 10.1007/s00412-011-0325-x] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2011] [Revised: 04/07/2011] [Accepted: 05/04/2011] [Indexed: 10/18/2022]
Abstract
Sugar beet (Beta vulgaris) chromosomes consist of large heterochromatic blocks in pericentromeric, centromeric, and intercalary regions comprised of two different highly abundant DNA satellite families. To investigate DNA methylation at single base resolution at heterochromatic regions, we applied a method for strand-specific bisulfite sequencing of more than 1,000 satellite monomers followed by statistical analyses. As a result, we uncovered diversity in the distribution of different methylation patterns in both satellite families. Heavily methylated CG and CHG (H=A, T, or C) sites occur more frequently in intercalary heterochromatin, while CHH sites, with the exception of CAA, are only sparsely methylated, in both intercalary and pericentromeric/centromeric heterochromatin. We show that the difference in DNA methylation intensity is correlated to unequal distribution of heterochromatic histone H3 methylation marks. While clusters of H3K9me2 were absent from pericentromeric heterochromatin and restricted only to intercalary heterochromatic regions, H3K9me1 and H3K27me1 were observed in all types of heterochromatin. By sequencing of a small RNA library consisting of 6.76 million small RNAs, we identified small interfering RNAs (siRNAs) of 24 nucleotides in size which originated from both strands of the satellite DNAs. We hypothesize an involvement of these siRNAs in the regulation of DNA and histone methylation for maintaining heterochromatin.
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Koukalova B, Moraes AP, Renny-Byfield S, Matyasek R, Leitch AR, Kovarik A. Fall and rise of satellite repeats in allopolyploids of Nicotiana over c. 5 million years. THE NEW PHYTOLOGIST 2010; 186:148-60. [PMID: 19968801 DOI: 10.1111/j.1469-8137.2009.03101.x] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
Allopolyploids represent natural experiments in which DNA sequences from different species are combined into a single nucleus and then coevolve, enabling us to follow the parental genomes, their interactions and evolution over time. Here, we examine the fate of satellite DNA over 5 million yr of divergence in plant genus Nicotiana (family Solanaceae). We isolated subtelomeric, tandemly repeated satellite DNA from Nicotiana diploid and allopolyploid species and analysed patterns of inheritance and divergence by sequence analysis, Southern blot hybridization and fluorescent in situ hybridization (FISH). We observed that parental satellite sequences redistribute around the genome in allopolyploids of Nicotiana section Polydicliae, formed c. 1 million yr ago (Mya), and that new satellite repeats evolved and amplified in section Repandae, which was formed c. 5 Mya. In some cases that process involved the complete replacement of parental satellite sequences. The rate of satellite repeat replacement is faster than theoretical predictions assuming the mechanism involved is unequal recombination and crossing-over. Instead we propose that this mechanism occurs with the deletion of large chromatin blocks and reamplification, perhaps via rolling circle replication.
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Affiliation(s)
- Blazena Koukalova
- Institute of Biophysics, Academy of Sciences of the Czech Republic, CZ-612 65 Brno, Czech Republic
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11
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Weber B, Wenke T, Frömmel U, Schmidt T, Heitkam T. The Ty1-copia families SALIRE and Cotzilla populating the Beta vulgaris genome show remarkable differences in abundance, chromosomal distribution, and age. Chromosome Res 2009; 18:247-63. [DOI: 10.1007/s10577-009-9104-4] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2009] [Accepted: 11/25/2009] [Indexed: 01/22/2023]
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12
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Nested Ty3-gypsy retrotransposons of a single Beta procumbens centromere contain a putative chromodomain. Chromosome Res 2009; 17:379-96. [PMID: 19322668 DOI: 10.1007/s10577-009-9029-y] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2008] [Revised: 01/12/2009] [Accepted: 01/12/2009] [Indexed: 12/18/2022]
Abstract
LTR retrotransposons belong to a major group of DNA sequences that are often localized in plant centromeres. Using BAC inserts originating from the centromere of a monosomic wild beet (Beta procumbens) chromosome fragment in Beta vulgaris, two complete LTR retrotransposons were identified. Both elements, designated Beetle1 and Beetle2, possess a coding region with genes in the order characteristic for Ty3-gypsy retrotransposons. Beetle1 and Beetle2 have a chromodomain in the C-terminus of the integrase gene and are highly similar to the centromeric retrotransposons (CRs) of rice, maize, and barley. Both retroelements were localized in the centromeric region of B. procumbens chromosomes by fluorescence in-situ hybridization. They can therefore be classified as centromere-specific chromoviruses. PCR analysis using RNA as template indicated that Beetle1 and Beetle2 are transcriptionally active. On the basis of the sequence diversity between the LTR sequences, it was estimated that Beetle1 and Beetle2 transposed within the last 60,000 years and 130,000 years, respectively. The centromeric localization of Beetle1 and Beetle2 and their transcriptional activity combined with high sequence conservation within each family play an important structural role in the centromeres of B. procumbens chromosomes.
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Chromosomal localization of a novel repetitive sequence in the Chenopodium quinoa genome. J Appl Genet 2009; 49:313-20. [PMID: 19029678 DOI: 10.1007/bf03195629] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
In this study, a novel repetitive sequence pTaq10 was isolated from the Taq I digest of the genomic DNA of the pseudocereal Chenopodium quinoa. Sequence analysis indicated that this 286-bp monomer is not homologous to any known retroelement sequence. FISH and Southern blot analysis showed that this sequence is characterized by an interspersed genomic organization. After FISH, hybridization signals were observed as small dots spread throughout all of the chromosomes. pTaq hybridization signals were excluded from 45S rRNA gene loci, but they partly overlapped with 5S rDNA loci. pTaq10 is not a species-specific sequence, as it was also detected in C. berlandieri.
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Kuykendall D, Shao J, Trimmer K. A Nest of LTR Retrotransposons Adjacent the Disease Resistance-Priming Gene NPR1 in Beta vulgaris L. U.S. Hybrid H20. INTERNATIONAL JOURNAL OF PLANT GENOMICS 2009; 2009:576742. [PMID: 19390694 PMCID: PMC2669250 DOI: 10.1155/2009/576742] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/26/2008] [Accepted: 01/25/2009] [Indexed: 05/02/2023]
Abstract
A nest of long terminal repeat (LTR) retrotransposons (RTRs), discovered by LTR_STRUC analysis, is near core genes encoding the NPR1 disease resistance-activating factor and a heat-shock-factor-(HSF-) like protein in sugarbeet hybrid US H20. SCHULTE, a 10 833 bp LTR retrotransposon, with 1372 bp LTRs that are 0.7% divergent, has two ORFs with unexpected introns but encoding a reverse transcriptase with rve and Rvt2 domains similar to Ty1/copia-type retrotransposons and a hypothetical protein. SCHULTE produced significant nucleotide BLAST alignments with repeat DNA elements from all four families of plants represented in the TIGR plant repeat database (PRD); the best nucleotide sequence alignment was to ToRTL1 in Lycopersicon esculentum. A second sugarbeet LTR retrotransposon, SCHMIDT, 11 565 bp in length, has 2561 bp LTRs that share 100% identity with each other and share 98-99% nucleotide sequence identity over 10% of their length with DRVs, a family of highly repetitive, relatively small DNA sequences that are widely dispersed over the sugarbeet genome. SCHMIDT encodes a complete gypsy-like polyprotein in a single ORF. Analysis using LTR_STRUC of an in silico deletion of both of the above two LTR retrotransposons found that SCHULTE and SCHMIDT had inserted within an older LTR retrotransposon, resulting in a nest that is only about 10 Kb upstream of NPR1 in sugarbeet hybrid US H20.
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Affiliation(s)
- David Kuykendall
- Molecular Plant Pathology Laboratory, ARS, USDA, Beltsville, MD 20705, USA
- *David Kuykendall:
| | - Jonathan Shao
- Molecular Plant Pathology Laboratory, ARS, USDA, Beltsville, MD 20705, USA
| | - Kenneth Trimmer
- Molecular Plant Pathology Laboratory, ARS, USDA, Beltsville, MD 20705, USA
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15
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Schwarzacher T. Fluorescent in situ hybridization to detect transgene integration into plant genomes. Methods Mol Biol 2008; 478:227-46. [PMID: 19009449 DOI: 10.1007/978-1-59745-379-0_14] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
Fluorescent chromosome analysis technologies have advanced our understanding of genome organization during the last 30 years and have enabled the investigation of DNA organization and structure as well as the evolution of chromosomes. Fluorescent chromosome staining allows even small chromosomes to be visualized, characterized by their composition and morphology, and counted. Aneuploidies and polyploidies can be established for species, breeding lines, and individuals, including changes occurring during hybridization or tissue culture and transformation protocols. Fluorescent in situ hybridization correlates molecular information of a DNA sequence with its physical location on chromosomes and genomes. It thus allows determination of the physical position of sequences and often is the only means to determine the abundance and distribution of DNA sequences that are difficult to map with any other molecular method or would require segregation analysis, in particular multicopy or repetitive DNA. Equally, it is often the best way to establish the incorporation of transgenes, their numbers, and physical organization along chromosomes. This chapter presents protocols for probe and chromosome preparation, fluorescent in situ hybridization, chromosome staining, and the analysis of results.
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Menzel G, Dechyeva D, Wenke T, Holtgräwe D, Weisshaar B, Schmidt T. Diversity of a complex centromeric satellite and molecular characterization of dispersed sequence families in sugar beet (Beta vulgaris). ANNALS OF BOTANY 2008; 102:521-30. [PMID: 18682437 PMCID: PMC2701778 DOI: 10.1093/aob/mcn131] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
BACKGROUND AND AIMS The aim of this work was the identification and molecular characterization of novel sugar beet (Beta vulgaris) repetitive sequences to unravel the impact of repetitive DNA on size and evolution of Beta genomes via amplification and diversification. METHODS Genomic DNA and a pool of B. vulgaris repetitive sequences were separately used as probes for a screening of high-density filters from a B. vulgaris plasmid library. Novel repetitive motifs were identified by sequencing and further used as probes for Southern analyses in the genus Beta. Chromosomal localization of the repeats was analysed by fluorescent in situ hybridization on chromosomes of B. vulgaris and two other species of the section Beta. KEY RESULTS Two dispersed repetitive families pDvul1 and pDvul2 and the tandemly arranged repeat family pRv1 were isolated from a sugar beet plasmid library. The dispersed repetitive families pDvul1 and pDvul2 were identified in all four sections of the genus Beta. The members of the pDvul1 and pDvul2 family are scattered over all B. vulgaris chromosomes, although amplified to a different extent. The pRv1 satellite repeat is exclusively present in species of the section Beta. The centromeric satellite pBV1 by structural variations of the monomer and interspersion of pRv1 units forms complex satellite structures, which are amplified in different degrees on the centromeres of 12 chromosomes of the three species of the Beta section. CONCLUSIONS The complexity of the pBV1 satellite family observed in the section Beta of the genus Beta and, in particular, the strong amplification of the pBV1/pRv1 satellite in the domesticated B. vulgaris indicates the dynamics of centromeric satellite evolution during species radiation within the genus. The dispersed repeat families pDvul1 and pDvul2 might represent derivatives of transposable elements.
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Affiliation(s)
- Gerhard Menzel
- Institute of Botany, Dresden University of Technology, D-01062 Dresden, Germany
| | - Daryna Dechyeva
- Institute of Botany, Dresden University of Technology, D-01062 Dresden, Germany
| | - Torsten Wenke
- Institute of Botany, Dresden University of Technology, D-01062 Dresden, Germany
| | - Daniela Holtgräwe
- Institute of Genome Research, University of Bielefeld, D-33594 Bielefeld, Germany
| | - Bernd Weisshaar
- Institute of Genome Research, University of Bielefeld, D-33594 Bielefeld, Germany
| | - Thomas Schmidt
- Institute of Botany, Dresden University of Technology, D-01062 Dresden, Germany
- For correspondence. E-mail
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Navrátilová A, Koblížková A, Macas J. Survey of extrachromosomal circular DNA derived from plant satellite repeats. BMC PLANT BIOLOGY 2008; 8:90. [PMID: 18721471 PMCID: PMC2543021 DOI: 10.1186/1471-2229-8-90] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/29/2008] [Accepted: 08/22/2008] [Indexed: 05/19/2023]
Abstract
BACKGROUND Satellite repeats represent one of the most dynamic components of higher plant genomes, undergoing rapid evolutionary changes of their nucleotide sequences and abundance in a genome. However, the exact molecular mechanisms driving these changes and their eventual regulation are mostly unknown. It has been proposed that amplification and homogenization of satellite DNA could be facilitated by extrachromosomal circular DNA (eccDNA) molecules originated by recombination-based excision from satellite repeat arrays. While the models including eccDNA are attractive for their potential to explain rapid turnover of satellite DNA, the existence of satellite repeat-derived eccDNA has not yet been systematically studied in a wider range of plant genomes. RESULTS We performed a survey of eccDNA corresponding to nine different families and three subfamilies of satellite repeats in ten species from various genera of higher plants (Arabidopsis, Oryza, Pisum, Secale, Triticum and Vicia). The repeats selected for this study differed in their monomer length, abundance, and chromosomal localization in individual species. Using two-dimensional agarose gel electrophoresis followed by Southern blotting, eccDNA molecules corresponding to all examined satellites were detected. EccDNA occurred in the form of nicked circles ranging from hundreds to over eight thousand nucleotides in size. Within this range the circular molecules occurred preferentially in discrete size intervals corresponding to multiples of monomer or higher-order repeat lengths. CONCLUSION This work demonstrated that satellite repeat-derived eccDNA is common in plant genomes and thus it can be seriously considered as a potential intermediate in processes driving satellite repeat evolution. The observed size distribution of circular molecules suggests that they are most likely generated by molecular mechanisms based on homologous recombination requiring long stretches of sequence similarity.
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Affiliation(s)
- Alice Navrátilová
- Biology Centre ASCR, Institute of Plant Molecular Biology, Branišovská 31, České Budějovice, CZ-37005, Czech Republic
| | - Andrea Koblížková
- Biology Centre ASCR, Institute of Plant Molecular Biology, Branišovská 31, České Budějovice, CZ-37005, Czech Republic
| | - Jiří Macas
- Biology Centre ASCR, Institute of Plant Molecular Biology, Branišovská 31, České Budějovice, CZ-37005, Czech Republic
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Dechyeva D, Schmidt T. Molecular organization of terminal repetitive DNA in Beta species. Chromosome Res 2007; 14:881-97. [PMID: 17195925 DOI: 10.1007/s10577-006-1096-8] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2006] [Revised: 10/19/2007] [Accepted: 10/19/2006] [Indexed: 09/29/2022]
Abstract
We have isolated families of subtelomeric satellite DNA sequences from species of four sections of the genus Beta and from spinach, a related Chenopodiaceae. Twenty-five clones were sequenced and representative repeats of each family were characterized by Southern blotting and FISH. The families of ApaI restriction satellite repeats were designated pAv34, pAc34, the families of RsaI repeats pRp34, pRn34 and pRs34. The repeating units are 344-362 bp long and 45.7-98.8% homologous with a clear species-specific divergence. Each satellite monomer consists of two subrepeats SR1 and SR2 of 165-184 bp, respectively. The repeats of each subrepeat group are highly identical across species, but share only a homology of 40.8-54.8% with members of the other subrepeat group. Two evolutionary steps could be supposed in the phylogeny of the subtelomeric satellite family: the diversification of an ancestor satellite into groups representing SR1 and SR2 in the progenitor of Beta and Spinacea species, followed by the dimerization and diversification of the resulting 360 bp repeats into section-specific satellite DNA families during species radiation. The chromosomal localization of telomeric, subtelomeric and rDNA tandem repeats was investigated by multi-colour FISH. High-resolution analysis by fibre FISH revealed a unique physical organization of B. vulgaris chromosome ends with telomeric DNA and subtelomeric satellites extending over a maximum of 63 kb and 125 kb, respectively.
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Affiliation(s)
- Daryna Dechyeva
- Institute of Botany, Dresden University of Technology, Zellescher Weg 20b, 01062 Dresden, Germany
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19
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Menzel G, Dechyeva D, Keller H, Lange C, Himmelbauer H, Schmidt T. Mobilization and evolutionary history of miniature inverted-repeat transposable elements (MITEs) in Beta vulgaris L. Chromosome Res 2007; 14:831-44. [PMID: 17171577 DOI: 10.1007/s10577-006-1090-1] [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] [Received: 08/15/2006] [Revised: 09/18/2006] [Accepted: 09/18/2006] [Indexed: 10/23/2022]
Abstract
We have identified three families of miniature inverted-repeat transposable elements (VulMITEs) in the genome of sugar beet (Beta vulgaris L.), evidently derived from a member of the Vulmar family of mariner transposons. While VulMITEs I are typical stowaway-like MITEs, VulMITEs II and VulMITEs III are rearranged stowaway elements of increased size. The integration of divergent moderately and highly repetitive sequences into VulMITEs II and, in particular in VulMITEs III, respectively, shows that amplification of repetitive DNA by MITEs contribute to the increase of genome size with possible implications for plant genome evolution. Fluorescent in-situ hybridization (FISH), for the first time visualizing stowaway MITE distribution on plant chromosomes, revealed a dispersed localization of VulMITEs along all B. vulgaris chromosomes. Analysis of the flanking sequences identified a dispersed repeat as target site for the integration of the stowaway element VulMITE I. Recent transposition of VulMITE I, which most likely occurred during the domestication of cultivated beets, was concluded from insertional polymorphisms between different B. vulgaris cultivars and species.
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Affiliation(s)
- Gerhard Menzel
- Institute of Botany, Dresden University of Technology, D-01062, Dresden, Germany
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Weiss-Schneeweiss H, Schneeweiss GM, Stuessy TF, Mabuchi T, Park JM, Jang CG, Sun BY. Chromosomal stasis in diploids contrasts with genome restructuring in auto- and allopolyploid taxa of Hepatica (Ranunculaceae). THE NEW PHYTOLOGIST 2007; 174:669-682. [PMID: 17447921 DOI: 10.1111/j.1469-8137.2007.02019.x] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
Polyploidization and chromosomal rearrangements are recognized as major forces in plant evolution. Their role is investigated in the disjunctly distributed northern hemisphere Hepatica (Ranunculaceae). Chromosome numbers, karyotype morphology, banding patterns, 5S and 35S rDNA localization in all known species were investigated and interpreted in a phylogenetic context established from nuclear internal transcribed spacer (ITS) and plastid matK sequences. All species had a chromosome base number of x = 7. The karyotype was symmetric and showed little variation among diploids with one locus each of 5S and 35S rDNA, except for interpopulational variation concerning 35S rDNA loci number and localization in H. asiatica. Tetraploids exhibited chromosomal changes, including asymmetry and/or loss of rDNA loci. Nuclear and plastid sequences resulted in incongruent topologies because of the positions of some tetraploid taxa. The diversification of Hepatica occurred not earlier than the Pliocene. Genome restructuring, especially involving 35S rDNA, within a few million yr or less characterizes evolution of both auto- and allopolyploids and of the diploid species H. asiatica, which is the presumptive ancestor of two other diploid species.
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Affiliation(s)
| | - Gerald M Schneeweiss
- Department of Biogeography and Botanical Garden, University of Vienna, Rennweg 14, A-1030 Vienna, Austria
| | - Tod F Stuessy
- Department of Systematic and Evolutionary Botany, and
| | - Tomoo Mabuchi
- 2-11-5 Sagami-ohno, Sagamihara, Kanagawa 228-0803, Japan
| | - Jeong-Mi Park
- Department of Systematic and Evolutionary Botany, and
| | - Chang-Gee Jang
- Department of Systematic and Evolutionary Botany, and
- Department of Biology Education, College of Education, Kongju National University, Kongju, Chungnam, 314-701, Republic of Korea
| | - Byung-Yun Sun
- Faculty of Biological Sciences, Chonbuk National University, Chonju, 561-756, Republic of Korea
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Macas J, Navrátilová A, Koblízková A. Sequence homogenization and chromosomal localization of VicTR-B satellites differ between closely related Vicia species. Chromosoma 2006; 115:437-47. [PMID: 16788823 DOI: 10.1007/s00412-006-0070-8] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2006] [Revised: 05/04/2006] [Accepted: 05/05/2006] [Indexed: 11/28/2022]
Abstract
Satellite sequences of the VicTR-B family are specific for the genus Vicia (Leguminosae), but their abundance varies among the species, being the highest in Vicia sativa and Vicia grandiflora. In this study, we have sequenced multiple randomly cloned VicTR-B fragments from these two species and analyzed their sequence variability, periodicity, and chromosomal localization. We have found that V. sativa VicTR-B sequences are homogeneous with respect to their nucleotide sequences and periodicity (monomers of 38 bp), whereas V. grandiflora repeats are considerably more variable, occurring in at least four distinct sequence subfamilies. Although the periodicity of 38 bp was conserved in most of the V. grandiflora sequences, one of the subfamilies was composed of higher-order repeats of 186 bp, which originated from a pentamer of the basic repeated unit. Individual VicTR-B subfamilies were preferentially located in either intercalary or subtelomeric regions of chromosomes. Interestingly, two V. grandiflora subfamilies with the highest similarity to V. sativa VicTR-B sequences were located in intercalary heterochromatic bands, showing similar chromosomal distribution as the majority of VicTR-B repeats in V. sativa. The other two V. grandiflora subfamilies showing a considerable divergence from V. sativa sequences were found to be accumulated at subtelomeric regions of V. grandiflora chromosomes.
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Affiliation(s)
- Jirí Macas
- Institute of Plant Molecular Biology, Branisovská 31, Ceské Budejovice, 37005, Czech Republic.
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Schulte D, Cai D, Kleine M, Fan L, Wang S, Jung C. A complete physical map of a wild beet (Beta procumbens) translocation in sugar beet. Mol Genet Genomics 2006; 275:504-11. [PMID: 16496176 DOI: 10.1007/s00438-006-0108-x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2005] [Accepted: 01/28/2006] [Indexed: 10/25/2022]
Abstract
Two sugar beet lines carry homologous translocations of the wild beet Beta procumbens. Long-range restriction mapping with rare cutting enzymes revealed that both translocations are different in size, however, an overlapping region of about 350 kb could be identified. Both lines are resistant to the beet cyst nematode but only TR520 carries the previously cloned resistance gene Hs1pro-1. Hence, a second gene for nematode resistance (Hs1-1) must be located within this region. A bacterial artificial chromosome (BAC) library was constructed from line TR520. The library was screened with a number of B. procumbens specific probes and 61 BAC clones were identified. Five BAC clones formed a minimal tiling path of 580 kb to cover the overlapping region between both translocations including the translocation breakpoint. The five BACs from the overlapping region and one additional BAC distal from that contig were sequenced. The total sequence length from the five BACs of the overlapping region amounted to 524 kb which is 74.35% of the total insert size of these BACs. The frequency of retrotransposon sequences ranged between 14.7 and 43.3%. A total of 133 ORFs were identified, none of these showed similarity to known disease resistance genes. Of these, 12 ORFs showed homology to genes involved in biotic stress resistance reactions or to transcription factors. This paper demonstrates how genome specific probes can be employed for cloning an alien gene introgression into a cultivated species.
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Affiliation(s)
- Daniela Schulte
- Plant Breeding Institute, Christian-Albrechts-University Kiel, Olshausenstr. 40, 24098, Kiel, Germany
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23
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Contento A, Heslop-Harrison JS, Schwarzacher T. Diversity of a major repetitive DNA sequence in diploid and polyploid Triticeae. Cytogenet Genome Res 2005; 109:34-42. [PMID: 15753556 DOI: 10.1159/000082379] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2004] [Indexed: 11/19/2022] Open
Abstract
About 90 members of a major tandemly repeated DNA sequence family originally described in rye as pSc119.2 have been isolated from 11 diploid and polyploid Triticeae species using primers from along the length of the sequence for PCR amplification. Alignment and similarity analysis showed that the 120-bp repeat unit family is diverse with single nucleotide changes and few insertions and deletions occurring throughout the sequence, with no characteristic genome or species-specific variants having developed during evolution of the extant genomes. Fluorescent in situ hybridization showed that each of the large blocks of the repeat at chromosomal sites harboured many variants of the 120-bp repeat. There were substantial copy number differences between genomes, with abundant sub-terminal sites in rye, interstitial sites in the B genome of wheat, and relatively few sites in the A and D genome. We conclude that sequence homogenization events have not been operative in this repeat and that the common ancestor of the Triticeae tribe had multiple sequences of the 120-bp repeat with a range of variation not unlike that seen within and between species today. This diversity has been maintained when sites are moved within the genome and in all species since their divergence within the Triticeae.
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Affiliation(s)
- A Contento
- Department of Biology, University of Leicester, Leicester, UK
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Meagher TR, Vassiliadis C. Phenotypic impacts of repetitive DNA in flowering plants. THE NEW PHYTOLOGIST 2005; 168:71-80. [PMID: 16159322 DOI: 10.1111/j.1469-8137.2005.01527.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
The discovery that nuclear DNA content varies widely among species, and even within species, was unexpected because it was thought that the number of genes required for an organism should be common across taxa. We now know that the bulk of nuclear DNA content variation is caused by repetitive DNA sequences characterized according to the nature of repeat (tandem vs dispersed) or chromosomal location/mechanism of replication (pericentromeric, telomeric or subtelomeric, microsatellites, minisatellites, satellites, transposable elements, retroelements). Variation in repetitive DNA, manifested as variation in nuclear DNA content, has been shown to have broad ecological and life-history consequences. For example, large genome size appears to limit fitness in extreme environmental conditions. Within species, variation in DNA content has been coupled to growth and development, such as maturation time in crop species. In Silene latifolia, DNA content is negatively correlated with flower size, a character that, in turn, has well documented ecological significance. These intraspecific studies suggest a connection between repetitive DNA and quantitative genetic determination of continuous characters. Novel insights into mechanisms by which repetitive DNA influences phenotype will lead to models of evolutionary change that extend well beyond the conventional view of evolution by allelic substitution.
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Affiliation(s)
- Thomas R Meagher
- Centre for Evolution, Genes & Genomics, School of Biology, Sir Harold Mitchell Building, University of St Andrews, St Andrews, Fife KY16 9TH, UK.
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Jacobs G, Dechyeva D, Menzel G, Dombrowski C, Schmidt T. Molecular characterization of Vulmar1, a complete mariner transposon of sugar beet and diversity of mariner- and En/Spm-like sequences in the genus Beta. Genome 2004; 47:1192-201. [PMID: 15644978 DOI: 10.1139/g04-067] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Transposons of the Tc1-mariner superfamily are widespread in eukaryotic genomes. We have isolated the mariner element Vulmar1 from Beta vulgaris L., which is 3909 bp long and bordered by perfect terminal inverted repeats of 32 bp with homology to terminal inverted repeats of transposons from soybean and rice. According to a characteristic amino acid signature, Vulmar1 can be assigned to the DD39D group of mariner transposons. Vulmar1 is flanked by a 5'-TA-3' target site duplication that is typical for mariner transposons. Southern hybridization revealed that mariner-like copies are highly abundant in Beta species, and sequence analysis of 10 transposase fragments from representative species of the four Beta sections revealed an identity between 34% and 100% after conceptual translation. By fluorescent in situ hybridization, Vulmar1 was detected in distal euchromatin as well as in some intercalary and pericentromeric regions of all B. vulgaris chromosomes. In addition, using PCR, we were able to amplify fragments of the transposase gene of En/Spm-like transposons in the genus Beta. En/Spm-like transposase sequences are highly amplified in four Beta sections and showed a considerable degree of conservation (88.5-100%) at the protein level, while the homology to corresponding regions of En/Spm transposons of other plant species ranges from 49.5% to 62.5%. By fluorescent in situ hybridization, En/Spm-like transposon signals of strong intensity were detected on all chromosomes of B. vulgaris.
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Affiliation(s)
- Gunnar Jacobs
- Plant Molecular Cytogenetics Group, Institute of Crop Science and Plant Breeding, Christian-Albrechts University of Kiel, D-24098 Kiel, Germany
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Abstract
In situ hybridization is a powerful and unique technique that correlates molecular information of a DNA sequence with its physical location along chromosomes and genomes. It thus provides valuable information about physical map position of sequences and often is the only means to determine abundance and distribution of repetitive sequences making up the majority of most genomes. Repeated DNA sequences, composed of units of a few to a thousand base pairs in size, occur in blocks (tandem or satellite repeats) or are dispersed (including transposable elements) throughout the genome. They are often the most variable components of a genome, often being species and, occasionally, chromosome specific. Their variability arises through amplification, diversification and dispersion, as well as homogenization and loss; there is a remarkable correlation of molecular sequence features with chromosomal organization including the length of repeat units, their higher order structures, chromosomal locations, and dispersion mechanisms. Our understanding of the structure, function, organization, and evolution of genomes and their evolving repetitive components enabled many new cytogenetic applications to both medicine and agriculture, particularly in diagnosis and plant breeding.Key words: repetitive DNA, genome organization, sequence evolution, telomere, centromere.
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