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Garcia S, Kovarik A, Maiwald S, Mann L, Schmidt N, Pascual-Díaz JP, Vitales D, Weber B, Heitkam T. The Dynamic Interplay Between Ribosomal DNA and Transposable Elements: A Perspective From Genomics and Cytogenetics. Mol Biol Evol 2024; 41:msae025. [PMID: 38306580 PMCID: PMC10946416 DOI: 10.1093/molbev/msae025] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2023] [Revised: 12/06/2023] [Accepted: 01/29/2024] [Indexed: 02/04/2024] Open
Abstract
Although both are salient features of genomes, at first glance ribosomal DNAs and transposable elements are genetic elements with not much in common: whereas ribosomal DNAs are mainly viewed as housekeeping genes that uphold all prime genome functions, transposable elements are generally portrayed as selfish and disruptive. These opposing characteristics are also mirrored in other attributes: organization in tandem (ribosomal DNAs) versus organization in a dispersed manner (transposable elements); evolution in a concerted manner (ribosomal DNAs) versus evolution by diversification (transposable elements); and activity that prolongs genomic stability (ribosomal DNAs) versus activity that shortens it (transposable elements). Re-visiting relevant instances in which ribosomal DNA-transposable element interactions have been reported, we note that both repeat types share at least four structural and functional hallmarks: (1) they are repetitive DNAs that shape genomes in evolutionary timescales, (2) they exchange structural motifs and can enter co-evolution processes, (3) they are tightly controlled genomic stress sensors playing key roles in senescence/aging, and (4) they share common epigenetic marks such as DNA methylation and histone modification. Here, we give an overview of the structural, functional, and evolutionary characteristics of both ribosomal DNAs and transposable elements, discuss their roles and interactions, and highlight trends and future directions as we move forward in understanding ribosomal DNA-transposable element associations.
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Affiliation(s)
- Sònia Garcia
- Institut Botànic de Barcelona (IBB), CSIC-CMCNB, 08038 Barcelona, Catalonia, Spain
| | - Ales Kovarik
- Institute of Biophysics, Academy of Sciences of the Czech Republic, 61265 Brno, Czech Republic
| | - Sophie Maiwald
- Faculty of Biology, Technische Universität Dresden, D-01069 Dresden, Germany
| | - Ludwig Mann
- Faculty of Biology, Technische Universität Dresden, D-01069 Dresden, Germany
| | - Nicola Schmidt
- Faculty of Biology, Technische Universität Dresden, D-01069 Dresden, Germany
| | | | - Daniel Vitales
- Institut Botànic de Barcelona (IBB), CSIC-CMCNB, 08038 Barcelona, Catalonia, Spain
- Laboratori de Botànica–Unitat Associada CSIC, Facultat de Farmàcia i Ciències de l’Alimentació, Universitat de Barcelona, 08028 Barcelona, Catalonia, Spain
| | - Beatrice Weber
- Faculty of Biology, Technische Universität Dresden, D-01069 Dresden, Germany
| | - Tony Heitkam
- Faculty of Biology, Technische Universität Dresden, D-01069 Dresden, Germany
- Institute of Biology, NAWI Graz, Karl-Franzens-Universität, A-8010 Graz, Austria
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2
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Mahelka V, Kopecký D, Majka J, Krak K. Uniparental expression of ribosomal RNA in × Festulolium grasses: a link between the genome and nucleolar dominance. FRONTIERS IN PLANT SCIENCE 2023; 14:1276252. [PMID: 37790792 PMCID: PMC10544908 DOI: 10.3389/fpls.2023.1276252] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/11/2023] [Accepted: 08/30/2023] [Indexed: 10/05/2023]
Abstract
Genome or genomic dominance (GD) is a phenomenon observed in hybrids when one parental genome becomes dominant over the other. It is manifested by the replacement of chromatin of the submissive genome by that of the dominant genome and by biased gene expression. Nucleolar dominance (ND) - the functional expression of only one parental set of ribosomal genes in hybrids - is another example of an intragenomic competitive process which, however, concerns ribosomal DNA only. Although GD and ND are relatively well understood, the nature and extent of their potential interdependence is mostly unknown. Here, we ask whether hybrids showing GD also exhibit ND and, if so, whether the dominant genome is the same. To test this, we used hybrids between Festuca and Lolium grasses (Festulolium), and between two Festuca species in which GD has been observed (with Lolium as the dominant genome in Festulolium and F. pratensis in interspecific Festuca hybrids). Using amplicon sequencing of ITS1 and ITS2 of the 45S ribosomal DNA (rDNA) cluster and molecular cytogenetics, we studied the organization and expression of rDNA in leaf tissue in five hybrid combinations, four generations and 31 genotypes [F. pratensis × L. multiflorum (F1, F2, F3, BC1), L. multiflorum × F. pratensis (F1), L. multiflorum × F. glaucescens (F2), L. perenne × F. pratensis (F1), F. glaucescens × F. pratensis (F1)]. We have found that instant ND occurs in Festulolium, where expression of Lolium-type rDNA reached nearly 100% in all F1 hybrids and was maintained through subsequent generations. Therefore, ND and GD in Festulolium are manifested by the same dominant genome (Lolium). We also confirmed the concordance between GD and ND in an interspecific cross between two Festuca species.
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Affiliation(s)
- Václav Mahelka
- Czech Academy of Sciences, Institute of Botany, Průhonice, Czechia
| | - David Kopecký
- Institute of Experimental Botany of the Czech Academy of Sciences, Centre of Plant Structural and Functional Genomics, Olomouc, Czechia
| | - Joanna Majka
- Institute of Experimental Botany of the Czech Academy of Sciences, Centre of Plant Structural and Functional Genomics, Olomouc, Czechia
| | - Karol Krak
- Czech Academy of Sciences, Institute of Botany, Průhonice, Czechia
- Faculty of Environmental Sciences, Czech University of Life Sciences Prague, Prague, Czechia
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Huang Y, Liu Y, Guo X, Fan C, Yi C, Shi Q, Su H, Liu C, Yuan J, Liu D, Yang W, Han F. New insights on the evolution of nucleolar dominance in newly resynthesized hexaploid wheat Triticum zhukovskyi. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2023; 115:1298-1315. [PMID: 37246611 DOI: 10.1111/tpj.16320] [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: 01/11/2023] [Revised: 05/11/2023] [Accepted: 05/23/2023] [Indexed: 05/30/2023]
Abstract
Nucleolar dominance (ND) is a widespread epigenetic phenomenon in hybridizations where nucleolus transcription fails at the nucleolus organizer region (NOR). However, the dynamics of NORs during the formation of Triticum zhukovskyi (GGAu Au Am Am ), another evolutionary branch of allohexaploid wheat, remains poorly understood. Here, we elucidated genetic and epigenetic changes occurring at the NOR loci within the Am , G, and D subgenomes during allopolyploidization by synthesizing hexaploid wheat GGAu Au Am Am and GGAu Au DD. In T. zhukovskyi, Au genome NORs from T. timopheevii (GGAu Au ) were lost, while the second incoming NORs from T. monococcum (Am Am ) were retained. Analysis of the synthesized T. zhukovskyi revealed that rRNA genes from the Am genome were silenced in F1 hybrids (GAu Am ) and remained inactive after genome doubling and subsequent self-pollinations. We observed increased DNA methylation accompanying the inactivation of NORs in the Am genome and found that silencing of NORs in the S1 generation could be reversed by a cytidine methylase inhibitor. Our findings provide insights into the ND process during the evolutionary period of T. zhukovskyi and highlight that inactive rDNA units may serve as a 'first reserve' in the form of R-loops, contributing to the successful evolution of T. zhukovskyi.
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Affiliation(s)
- Yuhong Huang
- State Key Laboratory of Plant Cell and Chromosome Engineering, Institute of Genetics and Developmental Biology, Innovation Academy for Seed Design, Chinese Academy of Sciences, Beijing, 100101, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Yang Liu
- State Key Laboratory of Plant Cell and Chromosome Engineering, Institute of Genetics and Developmental Biology, Innovation Academy for Seed Design, Chinese Academy of Sciences, Beijing, 100101, China
| | - Xianrui Guo
- State Key Laboratory of Plant Cell and Chromosome Engineering, Institute of Genetics and Developmental Biology, Innovation Academy for Seed Design, Chinese Academy of Sciences, Beijing, 100101, China
| | - Chaolan Fan
- State Key Laboratory of Plant Cell and Chromosome Engineering, Institute of Genetics and Developmental Biology, Innovation Academy for Seed Design, Chinese Academy of Sciences, Beijing, 100101, China
| | - Congyang Yi
- State Key Laboratory of Plant Cell and Chromosome Engineering, Institute of Genetics and Developmental Biology, Innovation Academy for Seed Design, Chinese Academy of Sciences, Beijing, 100101, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Qinghua Shi
- State Key Laboratory of Plant Cell and Chromosome Engineering, Institute of Genetics and Developmental Biology, Innovation Academy for Seed Design, Chinese Academy of Sciences, Beijing, 100101, China
| | - Handong Su
- Huazhong Agricultural University, Hubei, 430070, China
| | - Chang Liu
- State Key Laboratory of Plant Cell and Chromosome Engineering, Institute of Genetics and Developmental Biology, Innovation Academy for Seed Design, Chinese Academy of Sciences, Beijing, 100101, China
| | - Jing Yuan
- State Key Laboratory of Plant Cell and Chromosome Engineering, Institute of Genetics and Developmental Biology, Innovation Academy for Seed Design, Chinese Academy of Sciences, Beijing, 100101, China
| | - Dengcai Liu
- Triticeae Research Institute, Sichuan Agricultural University, Chengdu, 611130, China
| | - Wuyun Yang
- Crop Research Institute, Sichuan Academy of Agricultural Sciences, Chengdu, 610066, China
| | - Fangpu Han
- State Key Laboratory of Plant Cell and Chromosome Engineering, Institute of Genetics and Developmental Biology, Innovation Academy for Seed Design, Chinese Academy of Sciences, Beijing, 100101, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
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4
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Carvalho A, Lino A, Alves C, Lino C, Vareiro D, Lucas D, Afonso G, Costa J, Esteves M, Gaspar M, Bezerra M, Mendes V, Lima-Brito J. Combination of Iron and Zinc Enhanced the Root Cell Division, Mitotic Regularity and Nucleolar Activity of Hexaploid Triticale. PLANTS (BASEL, SWITZERLAND) 2023; 12:2517. [PMID: 37447076 DOI: 10.3390/plants12132517] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/01/2023] [Revised: 06/19/2023] [Accepted: 06/29/2023] [Indexed: 07/15/2023]
Abstract
Hexaploid triticale results from crosses between durum wheat and rye. Despite its high agronomic potential, triticale is mainly used for livestock feed. Triticale surpasses their parental species in adaptability and tolerance to abiotic and biotic stresses, being able to grow in acidic soils where a high amount of iron (Fe) and zinc (Zn) is typical. On the other hand, high amounts of these essential trace elements can be cytotoxic to bread wheat. The cytotoxicity induced by seed priming with a high concentration of Fe and Zn impaired root cell division and induced nucleolar changes in bread wheat. Such cytogenetic approaches were expedited and successfully determined cytotoxic and suited micronutrient dosages for wheat nutripriming. With this study, we intended to analyse the hexaploid triticale cv 'Douro' root mitotic cell cycle and nucleolar activity after seed priming performed with aqueous solutions of iron (Fe) and/or zinc (Zn), containing a concentration that was previously considered cytotoxic, to bread wheat and to infer the higher tolerance of triticale to these treatments. The overall cytogenetic data allowed us to conclude that the Fe + Zn treatment enhanced the root mitotic index (MI), mitosis regularity and nucleolar activity of 'Douro' relative to the control and the individual treatments performed with Fe or Zn alone. The Fe + Zn treatment might suit triticale biofortification through seed priming.
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Affiliation(s)
- Ana Carvalho
- Plant Cytogenomics Laboratory, Department of Genetics and Biotechnology, University of Trás-os-Montes and Alto Douro (UTAD), 5000-801 Vila Real, Portugal
- Centre for the Research and Technology of Agro-Environmental and Biological Sciences (CITAB), Institute for Innovation, Capacity Building and Sustainability of Agri-Food Production (Inov4Agro), UTAD, 5000-801 Vila Real, Portugal
| | - Alexandra Lino
- University of Trás-os-Montes and Alto Douro, 5000-801 Vila Real, Portugal
| | - Carolina Alves
- University of Trás-os-Montes and Alto Douro, 5000-801 Vila Real, Portugal
| | - Catarina Lino
- University of Trás-os-Montes and Alto Douro, 5000-801 Vila Real, Portugal
| | - Débora Vareiro
- University of Trás-os-Montes and Alto Douro, 5000-801 Vila Real, Portugal
| | - Diogo Lucas
- University of Trás-os-Montes and Alto Douro, 5000-801 Vila Real, Portugal
| | - Gabriela Afonso
- University of Trás-os-Montes and Alto Douro, 5000-801 Vila Real, Portugal
| | - José Costa
- University of Trás-os-Montes and Alto Douro, 5000-801 Vila Real, Portugal
| | - Margarida Esteves
- University of Trás-os-Montes and Alto Douro, 5000-801 Vila Real, Portugal
| | - Maria Gaspar
- University of Trás-os-Montes and Alto Douro, 5000-801 Vila Real, Portugal
| | - Mário Bezerra
- University of Trás-os-Montes and Alto Douro, 5000-801 Vila Real, Portugal
| | - Vladimir Mendes
- University of Trás-os-Montes and Alto Douro, 5000-801 Vila Real, Portugal
| | - José Lima-Brito
- Plant Cytogenomics Laboratory, Department of Genetics and Biotechnology, University of Trás-os-Montes and Alto Douro (UTAD), 5000-801 Vila Real, Portugal
- Centre for the Research and Technology of Agro-Environmental and Biological Sciences (CITAB), Institute for Innovation, Capacity Building and Sustainability of Agri-Food Production (Inov4Agro), UTAD, 5000-801 Vila Real, Portugal
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5
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Borowska-Zuchowska N, Mykhailyk S, Robaszkiewicz E, Matysiak N, Mielanczyk L, Wojnicz R, Kovarik A, Hasterok R. Switch them off or not: selective rRNA gene repression in grasses. TRENDS IN PLANT SCIENCE 2023; 28:661-672. [PMID: 36764871 DOI: 10.1016/j.tplants.2023.01.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/30/2022] [Revised: 12/31/2022] [Accepted: 01/11/2023] [Indexed: 05/13/2023]
Abstract
Nucleolar dominance (ND) is selective epigenetic silencing of 35-48S rDNA loci. In allopolyploids, it is frequently manifested at the cytogenetic level by the inactivation of nucleolar organiser region(s) (NORs) inherited from one or several evolutionary ancestors. Grasses are ecologically and economically one of the most important land plant groups, which have frequently evolved through hybridisation and polyploidisation events. Here we review common and unique features of ND phenomena in this monocot family from cytogenetic, molecular, and genomic perspectives. We highlight recent advances achieved by using an allotetraploid model grass, Brachypodium hybridum, where ND commonly occurs at a population level, and we cover modern genomic approaches that decipher structural features of core arrays of NORs.
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Affiliation(s)
- Natalia Borowska-Zuchowska
- Plant Cytogenetics and Molecular Biology Group, Institute of Biology, Biotechnology and Environmental Protection, Faculty of Natural Sciences, University of Silesia in Katowice, Katowice 40-032, Poland.
| | - Serhii Mykhailyk
- Plant Cytogenetics and Molecular Biology Group, Institute of Biology, Biotechnology and Environmental Protection, Faculty of Natural Sciences, University of Silesia in Katowice, Katowice 40-032, Poland
| | - Ewa Robaszkiewicz
- Plant Cytogenetics and Molecular Biology Group, Institute of Biology, Biotechnology and Environmental Protection, Faculty of Natural Sciences, University of Silesia in Katowice, Katowice 40-032, Poland
| | - Natalia Matysiak
- Department of Histology and Cell Pathology, the Medical University of Silesia in Katowice, School of Medicine with the Division of Dentistry, Zabrze, Poland
| | - Lukasz Mielanczyk
- Department of Histology and Cell Pathology, the Medical University of Silesia in Katowice, School of Medicine with the Division of Dentistry, Zabrze, Poland; Silesian Nanomicroscopy Centre in Zabrze, Silesia LabMed - Research and Implementation Centre, Medical University of Silesia, Katowice, Poland
| | - Romuald Wojnicz
- Department of Histology and Cell Pathology, the Medical University of Silesia in Katowice, School of Medicine with the Division of Dentistry, Zabrze, Poland; Silesian Nanomicroscopy Centre in Zabrze, Silesia LabMed - Research and Implementation Centre, Medical University of Silesia, Katowice, Poland
| | - Ales Kovarik
- Department of Molecular Epigenetics, Institute of Biophysics, Czech Academy of Sciences, CZ-61200 Brno, Czech Republic
| | - Robert Hasterok
- Plant Cytogenetics and Molecular Biology Group, Institute of Biology, Biotechnology and Environmental Protection, Faculty of Natural Sciences, University of Silesia in Katowice, Katowice 40-032, Poland.
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Levy AA, Feldman M. Evolution and origin of bread wheat. THE PLANT CELL 2022; 34:2549-2567. [PMID: 35512194 PMCID: PMC9252504 DOI: 10.1093/plcell/koac130] [Citation(s) in RCA: 51] [Impact Index Per Article: 25.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/10/2021] [Accepted: 03/18/2022] [Indexed: 05/12/2023]
Abstract
Bread wheat (Triticum aestivum, genome BBAADD) is a young hexaploid species formed only 8,500-9,000 years ago through hybridization between a domesticated free-threshing tetraploid progenitor, genome BBAA, and Aegilops tauschii, the diploid donor of the D subgenome. Very soon after its formation, it spread globally from its cradle in the fertile crescent into new habitats and climates, to become a staple food of humanity. This extraordinary global expansion was probably enabled by allopolyploidy that accelerated genetic novelty through the acquisition of new traits, new intergenomic interactions, and buffering of mutations, and by the attractiveness of bread wheat's large, tasty, and nutritious grain with high baking quality. New genome sequences suggest that the elusive donor of the B subgenome is a distinct (unknown or extinct) species rather than a mosaic genome. We discuss the origin of the diploid and tetraploid progenitors of bread wheat and the conflicting genetic and archaeological evidence on where it was formed and which species was its free-threshing tetraploid progenitor. Wheat experienced many environmental changes throughout its evolution, therefore, while it might adapt to current climatic changes, efforts are needed to better use and conserve the vast gene pool of wheat biodiversity on which our food security depends.
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Dang C, Zhang J, Dubcovsky J. High-resolution mapping of Yr78, an adult plant resistance gene to wheat stripe rust. THE PLANT GENOME 2022; 15:e20212. [PMID: 35470594 DOI: 10.1002/tpg2.20212] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/17/2022] [Accepted: 03/18/2022] [Indexed: 06/14/2023]
Abstract
Wheat stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), is responsible for significant yield losses worldwide, which can be minimized by the deployment of Pst resistance genes. Yr78 is an adult plant partial-resistance gene that has remained effective against the post-2000 virulent Pst races. In this study, we generated a high-resolution map of Yr78 based on 6,124 segregating chromosomes. We mapped Yr78 within a 0.05-cM interval on the short arm of chromosome 6B, which corresponds to an 11.16 Mb region between TraesCS6B02G116200 and TraesCS6B02G118000 in the 'Chinese Spring' Ref Seq. v1.1 genome. This interval is likely larger because it includes the unassembled NOR-B2 region, which may have contributed to the low recombination rate detected in this region. The Yr78 candidate region includes 15 genes that were prioritized for future functional studies based on their annotated function and polymorphisms between susceptible and resistant genotypes. Using exome capture data, we identified five major haplotypes in the candidate gene region, with the H1 haplotype associated with Yr78. The H1 haplotype was not detected in tetraploid wheat (Triticum turgidum L.) but was found in ∼30% of the common wheat cultivars (Triticum aestivum L.), suggesting that the associated resistance to stripe rust may have favored the selection of this haplotype. We developed two diagnostic molecular markers for the H1 haplotype that will facilitate the deployment of Yr78 in wheat breeding programs.
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Affiliation(s)
- Chen Dang
- Dep. of Plant Sciences, Univ. of California, Davis, CA, 95616, USA
| | - Junli Zhang
- Dep. of Plant Sciences, Univ. of California, Davis, CA, 95616, USA
| | - Jorge Dubcovsky
- Dep. of Plant Sciences, Univ. of California, Davis, CA, 95616, USA
- Howard Hughes Medical Institute, Chevy Chase, MD, 20815, USA
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von Well E, Booyse M, Fossey A. Effect of gamma irradiation on nucleolar activity in root tip cells of tetraploid Triticum turgidum ssp. durum L. PROTOPLASMA 2022; 259:453-468. [PMID: 34191122 DOI: 10.1007/s00709-021-01684-4] [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: 02/02/2021] [Accepted: 06/14/2021] [Indexed: 06/13/2023]
Abstract
Ionizing irradiation induces positive or negative changes in plant growth (M1) depending on the amount of irradiation applied to seeds or plant parts. The effect of 50-350 Gy gamma irradiation of kernels on nucleolar activity, as an indicator of metabolic activity, in root tip cells of tetraploid wheat Triticum turgidum ssp. durum L. cv. Orania (AABB) was investigated. The number of nucleoli present in nuclei and micronuclei as well as the mitotic index in the different irradiation dosages was used as an indicator of the cells entering mitosis, the chromosomes with nucleolar organizer regions that are active as well as chromosome doubling in the event of unsuccessful mitotic division. Nucleolar activity was investigated from 17.5 to 47.5 h after the onset of imbibition to study the first mitotic division and its consequences on the cells that were in G2 and G1 phases at the time of gamma irradiation. Untreated material produced a maximum of four nucleoli formed by the nucleolar organizing regions (NORs) on chromosomes 1B and 6B. In irradiated material, additional nucleoli were noted that are due to the activation of the NORs on chromosome 1A in micronuclei. The onset of mitosis was highly significantly retarded in comparison to the control due to checkpoints in the G2 phase for the repairing of damaged DNA. This study is the first to report on the appearance of nucleoli in micronuclei as well as activation of NORs in the micronuclei that are inactive in the nucleus and the effect of chromosome doubling on nucleolar activity in the event of unsuccessful mitotic division.
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Affiliation(s)
- Eben von Well
- ARC-Small Grain, Field Crops, Division, Private Bag X29, Bethlehem, 9700, South Africa.
| | - Mardé Booyse
- ARC-Biometry, Private Bag X5013, Stellenbosch, 7599, South Africa
| | - Annabel Fossey
- Central University of Technology, 1 Park Street, Bloemfontein, 9301, South Africa
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Tulpová Z, Kovařík A, Toegelová H, Navrátilová P, Kapustová V, Hřibová E, Vrána J, Macas J, Doležel J, Šimková H. Fine structure and transcription dynamics of bread wheat ribosomal DNA loci deciphered by a multi-omics approach. THE PLANT GENOME 2022; 15:e20191. [PMID: 35092350 DOI: 10.1002/tpg2.20191] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/31/2021] [Accepted: 12/16/2021] [Indexed: 06/14/2023]
Abstract
Three out of four RNA components of ribosomes are encoded by 45S ribosomal DNA (rDNA) loci, which are organized as long head-to-tail tandem arrays of nearly identical units, spanning several megabases of sequence. Due to this structure, the rDNA loci are the major sources of gaps in genome assemblies, and gene copy number, sequence composition, and expression status of particular arrays remain elusive, especially in complex genomes harboring multiple loci. Here we conducted a multi-omics study to decipher the 45S rDNA loci in hexaploid bread wheat. Coupling chromosomal genomics with optical mapping, we reconstructed individual rDNA arrays, enabling locus-specific analyses of transcription activity and methylation status from RNA- and bisulfite-sequencing data. We estimated a total of 6,650 rDNA units in the bread wheat genome, with approximately 2,321, 3,910, 253, and 50 gene copies located in short arms of chromosomes 1B, 6B, 5D, and 1A, respectively. Only 1B and 6B loci contributed substantially to rRNA transcription at a roughly 2:1 ratio. The ratio varied among five tissues analyzed (embryo, coleoptile, root tip, primary leaf, mature leaf), being the highest (2.64:1) in mature leaf and lowest (1.72:1) in coleoptile. Cytosine methylation was considerably higher in CHG context in the silenced 5D locus as compared with the active 1B and 6B loci. In conclusion, a fine genomic organization and tissue-specific expression of rDNA loci were deciphered, for the first time, in a complex polyploid species. The results are discussed in the context of wheat evolution and transcription regulation.
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Affiliation(s)
- Zuzana Tulpová
- Institute of Experimental Botany of the Czech Academy of Sciences, Centre of the Region Haná for Biotechnological and Agricultural Research, Olomouc, Czech Republic
| | - Aleš Kovařík
- Institute of Biophysics, Czech Academy of Sciences, Brno, Czech Republic
| | - Helena Toegelová
- Institute of Experimental Botany of the Czech Academy of Sciences, Centre of the Region Haná for Biotechnological and Agricultural Research, Olomouc, Czech Republic
| | - Pavla Navrátilová
- Institute of Experimental Botany of the Czech Academy of Sciences, Centre of the Region Haná for Biotechnological and Agricultural Research, Olomouc, Czech Republic
| | - Veronika Kapustová
- Institute of Experimental Botany of the Czech Academy of Sciences, Centre of the Region Haná for Biotechnological and Agricultural Research, Olomouc, Czech Republic
| | - Eva Hřibová
- Institute of Experimental Botany of the Czech Academy of Sciences, Centre of the Region Haná for Biotechnological and Agricultural Research, Olomouc, Czech Republic
| | - Jan Vrána
- Institute of Experimental Botany of the Czech Academy of Sciences, Centre of the Region Haná for Biotechnological and Agricultural Research, Olomouc, Czech Republic
| | - Jiří Macas
- Biology Centre, Institute of Plant Molecular Biology, Czech Academy of Sciences, České Budějovice, Czech Republic
| | - Jaroslav Doležel
- Institute of Experimental Botany of the Czech Academy of Sciences, Centre of the Region Haná for Biotechnological and Agricultural Research, Olomouc, Czech Republic
| | - Hana Šimková
- Institute of Experimental Botany of the Czech Academy of Sciences, Centre of the Region Haná for Biotechnological and Agricultural Research, Olomouc, Czech Republic
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10
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Appels R, Wang P, Islam S. Integrating Wheat Nucleolus Structure and Function: Variation in the Wheat Ribosomal RNA and Protein Genes. FRONTIERS IN PLANT SCIENCE 2021; 12:686586. [PMID: 35003148 PMCID: PMC8739226 DOI: 10.3389/fpls.2021.686586] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/27/2021] [Accepted: 11/08/2021] [Indexed: 06/13/2023]
Abstract
We review the coordinated production and integration of the RNA (ribosomal RNA, rRNA) and protein (ribosomal protein, RP) components of wheat cytoplasmic ribosomes in response to changes in genetic constitution, biotic and abiotic stresses. The components examined are highly conserved and identified with reference to model systems such as human, Arabidopsis, and rice, but have sufficient levels of differences in their DNA and amino acid sequences to form fingerprints or gene haplotypes that provide new markers to associate with phenotype variation. Specifically, it is argued that populations of ribosomes within a cell can comprise distinct complements of rRNA and RPs to form units with unique functionalities. The unique functionalities of ribosome populations within a cell can become central in situations of stress where they may preferentially translate mRNAs coding for proteins better suited to contributing to survival of the cell. In model systems where this concept has been developed, the engagement of initiation factors and elongation factors to account for variation in the translation machinery of the cell in response to stresses provided the precedents. The polyploid nature of wheat adds extra variation at each step of the synthesis and assembly of the rRNAs and RPs which can, as a result, potentially enhance its response to changing environments and disease threats.
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Affiliation(s)
- Rudi Appels
- AgriBio, Centre for AgriBioscience, La Trobe University, Bundoora, VIC, Australia
- Faculty of Veterinary and Agricultural Science, Melbourne, VIC, Australia
| | - Penghao Wang
- School of Veterinary and Life Sciences, Murdoch University, Murdoch, WA, Australia
| | - Shahidul Islam
- Centre for Crop Innovation, Food Futures Institute, Murdoch University, Murdoch, WA, Australia
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Hemleben V, Grierson D, Borisjuk N, Volkov RA, Kovarik A. Personal Perspectives on Plant Ribosomal RNA Genes Research: From Precursor-rRNA to Molecular Evolution. FRONTIERS IN PLANT SCIENCE 2021; 12:797348. [PMID: 34992624 PMCID: PMC8724763 DOI: 10.3389/fpls.2021.797348] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/18/2021] [Accepted: 11/26/2021] [Indexed: 06/13/2023]
Abstract
The history of rDNA research started almost 90 years ago when the geneticist, Barbara McClintock observed that in interphase nuclei of maize the nucleolus was formed in association with a specific region normally located near the end of a chromosome, which she called the nucleolar organizer region (NOR). Cytologists in the twentieth century recognized the nucleolus as a common structure in all eukaryotic cells, using both light and electron microscopy and biochemical and genetic studies identified ribosomes as the subcellular sites of protein synthesis. In the mid- to late 1960s, the synthesis of nuclear-encoded rRNA was the only system in multicellular organisms where transcripts of known function could be isolated, and their synthesis and processing could be studied. Cytogenetic observations of NOR regions with altered structure in plant interspecific hybrids and detailed knowledge of structure and function of rDNA were prerequisites for studies of nucleolar dominance, epistatic interactions of rDNA loci, and epigenetic silencing. In this article, we focus on the early rDNA research in plants, performed mainly at the dawn of molecular biology in the 60 to 80-ties of the last century which presented a prequel to the modern genomic era. We discuss - from a personal view - the topics such as synthesis of rRNA precursor (35S pre-rRNA in plants), processing, and the organization of 35S and 5S rDNA. Cloning and sequencing led to the observation that the transcribed and processed regions of the rRNA genes vary enormously, even between populations and species, in comparison with the more conserved regions coding for the mature rRNAs. Epigenetic phenomena and the impact of hybridization and allopolyploidy on rDNA expression and homogenization are discussed. This historical view of scientific progress and achievements sets the scene for the other articles highlighting the immense progress in rDNA research published in this special issue of Frontiers in Plant Science on "Molecular organization, evolution, and function of ribosomal DNA."
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Affiliation(s)
- Vera Hemleben
- Center of Plant Molecular Biology (ZMBP), University of Tübingen, Tübingen, Germany
| | - Donald Grierson
- Plant and Crop Sciences Division, School of Biosciences, University of Nottingham, Sutton Bonington Campus, Loughborough, United Kingdom
| | - Nikolai Borisjuk
- School of Life Sciences, Huaiyin Normal University, Huai'an, China
| | - Roman A. Volkov
- Department of Molecular Genetics and Biotechnology, Yuriy Fedkovych Chernivtsi National University, Chernivtsi, Ukraine
| | - Ales Kovarik
- Laboratory of Molecular Epigenetics, Institute of Biophysics, Academy of Sciences of the Czech Republic, Brno, Czechia
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Vekemans X, Castric V, Hipperson H, Müller NA, Westerdahl H, Cronk Q. Whole-genome sequencing and genome regions of special interest: Lessons from major histocompatibility complex, sex determination, and plant self-incompatibility. Mol Ecol 2021; 30:6072-6086. [PMID: 34137092 PMCID: PMC9290700 DOI: 10.1111/mec.16020] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2021] [Revised: 05/31/2021] [Accepted: 06/07/2021] [Indexed: 11/27/2022]
Abstract
Whole‐genome sequencing of non‐model organisms is now widely accessible and has allowed a range of questions in the field of molecular ecology to be investigated with greater power. However, some genomic regions that are of high biological interest remain problematic for assembly and data‐handling. Three such regions are the major histocompatibility complex (MHC), sex‐determining regions (SDRs) and the plant self‐incompatibility locus (S‐locus). Using these as examples, we illustrate the challenges of both assembling and resequencing these highly polymorphic regions and how bioinformatic and technological developments are enabling new approaches to their study. Mapping short‐read sequences against multiple alternative references improves genotyping comprehensiveness at the S‐locus thereby contributing to more accurate assessments of allelic frequencies. Long‐read sequencing, producing reads of several tens to hundreds of kilobase pairs in length, facilitates the assembly of such regions as single sequences can span the multiple duplicated gene copies of the MHC region, and sequence through repetitive stretches and translocations in SDRs and S‐locus haplotypes. These advances are adding value to short‐read genome resequencing approaches by allowing, for example, more accurate haplotype phasing across longer regions. Finally, we assessed further technical improvements, such as nanopore adaptive sequencing and bioinformatic tools using pangenomes, which have the potential to further expand our knowledge of a number of genomic regions that remain challenging to study with classical resequencing approaches.
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Affiliation(s)
| | | | - Helen Hipperson
- Department of Animal and Plant Sciences, University of Sheffield, Sheffield, UK
| | - Niels A Müller
- Thünen Institute of Forest Genetics, Grosshansdorf, Germany
| | - Helena Westerdahl
- Molecular Ecology and Evolution Laboratory, Department of Biology, Lund University, Lund, Sweden
| | - Quentin Cronk
- Department of Botany and Biodiversity Research Centre, University of British Columbia, Vancouver, BC, Canada
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Kapustová V, Tulpová Z, Toegelová H, Novák P, Macas J, Karafiátová M, Hřibová E, Doležel J, Šimková H. The Dark Matter of Large Cereal Genomes: Long Tandem Repeats. Int J Mol Sci 2019; 20:E2483. [PMID: 31137466 PMCID: PMC6567227 DOI: 10.3390/ijms20102483] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2019] [Revised: 05/15/2019] [Accepted: 05/16/2019] [Indexed: 01/08/2023] Open
Abstract
Reference genomes of important cereals, including barley, emmer wheat and bread wheat, were released recently. Their comparison with genome size estimates obtained by flow cytometry indicated that the assemblies represent not more than 88-98% of the complete genome. This work is aimed at identifying the missing parts in two cereal genomes and proposing techniques to make the assemblies more complete. We focused on tandemly organised repetitive sequences, known to be underrepresented in genome assemblies generated from short-read sequence data. Our study found arrays of three tandem repeats with unit sizes of 1242 to 2726 bp present in the bread wheat reference genome generated from short reads. However, this and another wheat genome assembly employing long PacBio reads failed in integrating correctly the 2726-bp repeat in the pseudomolecule context. This suggests that tandem repeats of this size, frequently incorporated in unassigned scaffolds, may contribute to shrinking of pseudomolecules without reducing size of the entire assembly. We demonstrate how this missing information may be added to the pseudomolecules with the aid of nanopore sequencing of individual BAC clones and optical mapping. Using the latter technique, we identified and localised a 470-kb long array of 45S ribosomal DNA absent from the reference genome of barley.
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Affiliation(s)
- Veronika Kapustová
- Institute of Experimental Botany, Centre of the Region Haná for Biotechnological and Agricultural Research, Šlechtitelů 31, CZ-78371 Olomouc, Czech Republic.
| | - Zuzana Tulpová
- Institute of Experimental Botany, Centre of the Region Haná for Biotechnological and Agricultural Research, Šlechtitelů 31, CZ-78371 Olomouc, Czech Republic.
| | - Helena Toegelová
- Institute of Experimental Botany, Centre of the Region Haná for Biotechnological and Agricultural Research, Šlechtitelů 31, CZ-78371 Olomouc, Czech Republic.
| | - Petr Novák
- Biology Centre, Czech Academy of Sciences, Institute of Plant Molecular Biology, Branišovská 31, CZ-37005 České Budějovice, Czech Republic.
| | - Jiří Macas
- Biology Centre, Czech Academy of Sciences, Institute of Plant Molecular Biology, Branišovská 31, CZ-37005 České Budějovice, Czech Republic.
| | - Miroslava Karafiátová
- Institute of Experimental Botany, Centre of the Region Haná for Biotechnological and Agricultural Research, Šlechtitelů 31, CZ-78371 Olomouc, Czech Republic.
| | - Eva Hřibová
- Institute of Experimental Botany, Centre of the Region Haná for Biotechnological and Agricultural Research, Šlechtitelů 31, CZ-78371 Olomouc, Czech Republic.
| | - Jaroslav Doležel
- Institute of Experimental Botany, Centre of the Region Haná for Biotechnological and Agricultural Research, Šlechtitelů 31, CZ-78371 Olomouc, Czech Republic.
| | - Hana Šimková
- Institute of Experimental Botany, Centre of the Region Haná for Biotechnological and Agricultural Research, Šlechtitelů 31, CZ-78371 Olomouc, Czech Republic.
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