1
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Beringer M, Choudhury RR, Mandáková T, Grünig S, Poretti M, Leitch IJ, Lysak MA, Parisod C. Biased Retention of Environment-Responsive Genes Following Genome Fractionation. Mol Biol Evol 2024; 41:msae155. [PMID: 39073781 PMCID: PMC11306978 DOI: 10.1093/molbev/msae155] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2024] [Revised: 07/05/2024] [Accepted: 07/11/2024] [Indexed: 07/30/2024] Open
Abstract
The molecular underpinnings and consequences of cycles of whole-genome duplication (WGD) and subsequent gene loss through subgenome fractionation remain largely elusive. Endogenous drivers, such as transposable elements (TEs), have been postulated to shape genome-wide dominance and biased fractionation, leading to a conserved least-fractionated (LF) subgenome and a degenerated most-fractionated (MF) subgenome. In contrast, the role of exogenous factors, such as those induced by environmental stresses, has been overlooked. In this study, a chromosome-scale assembly of the alpine buckler mustard (Biscutella laevigata; Brassicaceae) that underwent a WGD event about 11 million years ago is coupled with transcriptional responses to heat, cold, drought, and herbivory to assess how gene expression is associated with differential gene retention across the MF and LF subgenomes. Counteracting the impact of TEs in reducing the expression and retention of nearby genes across the MF subgenome, dosage balance is highlighted as a main endogenous promoter of the retention of duplicated gene products under purifying selection. Consistent with the "turn a hobby into a job" model, about one-third of environment-responsive duplicates exhibit novel expression patterns, with one copy typically remaining conditionally expressed, whereas the other copy has evolved constitutive expression, highlighting exogenous factors as a major driver of gene retention. Showing uneven patterns of fractionation, with regions remaining unbiased, but with others showing high bias and significant enrichment in environment-responsive genes, this mesopolyploid genome presents evolutionary signatures consistent with an interplay of endogenous and exogenous factors having driven gene content following WGD-fractionation cycles.
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Affiliation(s)
- Marc Beringer
- Department of Biology, University of Fribourg, Chemin du Musée 10, 1700 Fribourg, Switzerland
- Institute of Plant Sciences, University of Bern, Altenbergrain 21, 3013 Bern, Switzerland
| | - Rimjhim Roy Choudhury
- Department of Biology, University of Fribourg, Chemin du Musée 10, 1700 Fribourg, Switzerland
- Institute of Plant Sciences, University of Bern, Altenbergrain 21, 3013 Bern, Switzerland
| | - Terezie Mandáková
- Central European Institute of Technology, Masaryk University, 625 00 Brno, Czech Republic
| | - Sandra Grünig
- Department of Biology, University of Fribourg, Chemin du Musée 10, 1700 Fribourg, Switzerland
- Institute of Plant Sciences, University of Bern, Altenbergrain 21, 3013 Bern, Switzerland
| | - Manuel Poretti
- Department of Biology, University of Fribourg, Chemin du Musée 10, 1700 Fribourg, Switzerland
| | | | - Martin A Lysak
- Central European Institute of Technology, Masaryk University, 625 00 Brno, Czech Republic
| | - Christian Parisod
- Department of Biology, University of Fribourg, Chemin du Musée 10, 1700 Fribourg, Switzerland
- Institute of Plant Sciences, University of Bern, Altenbergrain 21, 3013 Bern, Switzerland
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2
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Benson CW, Sheltra MR, Maughan PJ, Jellen EN, Robbins MD, Bushman BS, Patterson EL, Hall ND, Huff DR. Homoeologous evolution of the allotetraploid genome of Poa annua L. BMC Genomics 2023; 24:350. [PMID: 37365554 DOI: 10.1186/s12864-023-09456-5] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2023] [Accepted: 06/15/2023] [Indexed: 06/28/2023] Open
Abstract
BACKGROUND Poa annua (annual bluegrass) is an allotetraploid turfgrass, an agronomically significant weed, and one of the most widely dispersed plant species on earth. Here, we report the chromosome-scale genome assemblies of P. annua's diploid progenitors, P. infirma and P. supina, and use multi-omic analyses spanning all three species to better understand P. annua's evolutionary novelty. RESULTS We find that the diploids diverged from their common ancestor 5.5 - 6.3 million years ago and hybridized to form P. annua ≤ 50,000 years ago. The diploid genomes are similar in chromosome structure and most notably distinguished by the divergent evolutionary histories of their transposable elements, leading to a 1.7 × difference in genome size. In allotetraploid P. annua, we find biased movement of retrotransposons from the larger (A) subgenome to the smaller (B) subgenome. We show that P. annua's B subgenome is preferentially accumulating genes and that its genes are more highly expressed. Whole-genome resequencing of several additional P. annua accessions revealed large-scale chromosomal rearrangements characterized by extensive TE-downsizing and evidence to support the Genome Balance Hypothesis. CONCLUSIONS The divergent evolutions of the diploid progenitors played a central role in conferring onto P. annua its remarkable phenotypic plasticity. We find that plant genes (guided by selection and drift) and transposable elements (mostly guided by host immunity) each respond to polyploidy in unique ways and that P. annua uses whole-genome duplication to purge highly parasitized heterochromatic sequences. The findings and genomic resources presented here will enable the development of homoeolog-specific markers for accelerated weed science and turfgrass breeding.
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Affiliation(s)
- Christopher W Benson
- Department of Plant Science, Pennsylvania State University, University Park, PA, USA.
- Intercollegiate Graduate Degree Program in Plant Biology, Pennsylvania State University, University Park, PA, USA.
| | - Matthew R Sheltra
- Department of Plant Science, Pennsylvania State University, University Park, PA, USA
- Intercollegiate Graduate Degree Program in Plant Biology, Pennsylvania State University, University Park, PA, USA
| | - Peter J Maughan
- Department of Plant and Wildlife Sciences, Brigham Young University, Logan, UT, USA
| | - Eric N Jellen
- Department of Plant and Wildlife Sciences, Brigham Young University, Logan, UT, USA
| | | | | | - Eric L Patterson
- Department of Plant, Soil, and Microbial Sciences, Michigan State University, East Lansing, MI, USA
| | - Nathan D Hall
- Department of Plant, Soil, and Microbial Sciences, Michigan State University, East Lansing, MI, USA
| | - David R Huff
- Department of Plant Science, Pennsylvania State University, University Park, PA, USA.
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3
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Vershinin AV, Elisafenko EA, Evtushenko EV. Genetic Redundancy in Rye Shows in a Variety of Ways. PLANTS (BASEL, SWITZERLAND) 2023; 12:282. [PMID: 36678994 PMCID: PMC9862056 DOI: 10.3390/plants12020282] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/29/2022] [Revised: 12/28/2022] [Accepted: 01/04/2023] [Indexed: 06/17/2023]
Abstract
Fifty years ago Susumu Ohno formulated the famous C-value paradox, which states that there is no correlation between the physical sizes of the genome, i.e., the amount of DNA, and the complexity of the organism, and highlighted the problem of genome redundancy. DNA that does not have a positive effect on the fitness of organisms has been characterized as "junk or selfish DNA". The controversial concept of junk DNA remains viable. Rye is a convenient subject for yet another test of the correctness and scientific significance of this concept. The genome of cultivated rye, Secale cereale L., is considered one of the largest among species of the tribe Triticeae and thus it tops the average angiosperm genome and the genomes of its closest evolutionary neighbors, such as species of barley, Hordeum (by approximately 30-35%), and diploid wheat species, Triticum (approximately 25%). The review provides an analysis of the structural organization of various regions of rye chromosomes with a description of the molecular mechanisms contributing to their size increase during evolution and the classes of DNA sequences involved in these processes. The history of the development of the concept of eukaryotic genome redundancy is traced and the current state of this problem is discussed.
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Affiliation(s)
- Alexander V. Vershinin
- Institute of Molecular and Cellular Biology, SB RAS, Acad. Lavrentiev Ave. 8/2, 630090 Novosibirsk, Russia
| | - Evgeny A. Elisafenko
- Institute of Molecular and Cellular Biology, SB RAS, Acad. Lavrentiev Ave. 8/2, 630090 Novosibirsk, Russia
- Institute of Cytology and Genetics, SB RAS, Acad. Lavrentiev Ave. 10, 630090 Novosibirsk, Russia
| | - Elena V. Evtushenko
- Institute of Molecular and Cellular Biology, SB RAS, Acad. Lavrentiev Ave. 8/2, 630090 Novosibirsk, Russia
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4
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Fagundes NJ, Bisso-Machado R, Figueiredo PI, Varal M, Zani AL. OUP accepted manuscript. Genome Biol Evol 2022; 14:6583081. [PMID: 35535669 PMCID: PMC9086759 DOI: 10.1093/gbe/evac055] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/16/2022] [Indexed: 11/12/2022] Open
Abstract
“Junk DNA” is a popular yet controversial concept that states that organisms carry in their genomes DNA that has no positive impact on their fitness. Nonetheless, biochemical functions have been identified for an increasing fraction of DNA elements traditionally seen as “Junk DNA”. These findings have been interpreted as fundamentally undermining the “Junk DNA” concept. Here, we reinforce previous arguments that this interpretation relies on an inadequate concept of biological function that does not consider the selected effect of a given genomic structure, which is central to the “Junk DNA” concept. Next, we suggest that another (though ignored) confounding factor is that the discussion about biological functions includes two different dimensions: a horizontal, ecological dimension that reflects how a given genomic element affects fitness in a specific time, and a vertical, temporal dimension that reflects how a given genomic element persisted along time. We suggest that “Junk DNA” should be used exclusively relative to the horizontal dimension, while for the vertical dimension, we propose a new term, “Spam DNA”, that reflects the fact that a given genomic element may persist in the genome even if not selected for on their origin. Importantly, these concepts are complementary. An element can be both “Spam DNA” and “Junk DNA”, and “Spam DNA” can also be recruited to perform evolved biological functions, as illustrated in processes of exaptation or constructive neutral evolution.
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Affiliation(s)
| | - Rafael Bisso-Machado
- Postgraduate Program in Genetics and Molecular Biology, Institute of Biosciences, Federal University of Rio Grande do Sul, Porto Alegre, Brazil
| | - Pedro I.C.C. Figueiredo
- Postgraduate Program in Genetics and Molecular Biology, Institute of Biosciences, Federal University of Rio Grande do Sul, Porto Alegre, Brazil
| | - Maikel Varal
- Postgraduate Program in Genetics and Molecular Biology, Institute of Biosciences, Federal University of Rio Grande do Sul, Porto Alegre, Brazil
| | - André L.S. Zani
- Postgraduate Program in Genetics and Molecular Biology, Institute of Biosciences, Federal University of Rio Grande do Sul, Porto Alegre, Brazil
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5
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Birchler JA, Veitia RA. One Hundred Years of Gene Balance: How Stoichiometric Issues Affect Gene Expression, Genome Evolution, and Quantitative Traits. Cytogenet Genome Res 2021; 161:529-550. [PMID: 34814143 DOI: 10.1159/000519592] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2021] [Accepted: 09/13/2021] [Indexed: 11/19/2022] Open
Abstract
A century ago experiments with the flowering plant Datura stramonium and the fruit fly Drosophila melanogaster revealed that adding an extra chromosome to a karyotype was much more detrimental than adding a whole set of chromosomes. This phenomenon was referred to as gene balance and has been recapitulated across eukaryotic species. Here, we retrace some developments in this field. Molecular studies suggest that the basis of balance involves stoichiometric relationships of multi-component interactions. This concept has implication for the mechanisms controlling gene expression, genome evolution, sex chromosome evolution/dosage compensation, speciation mechanisms, and the underlying genetics of quantitative traits.
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Affiliation(s)
- James A Birchler
- Division of Biological Sciences, University of Missouri, Columbia, Missouri, USA
| | - Reiner A Veitia
- Université de Paris, Paris, France.,Institut Jacques Monod, Université de Paris/CNRS, Paris, France.,Institut de Biologie F. Jacob, Commissariat à l'Energie Atomique, Université Paris-Saclay, Fontenay aux Roses, France
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6
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Nicolau M, Picault N, Moissiard G. The Evolutionary Volte-Face of Transposable Elements: From Harmful Jumping Genes to Major Drivers of Genetic Innovation. Cells 2021; 10:cells10112952. [PMID: 34831175 PMCID: PMC8616336 DOI: 10.3390/cells10112952] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2021] [Revised: 10/20/2021] [Accepted: 10/20/2021] [Indexed: 12/25/2022] Open
Abstract
Transposable elements (TEs) are self-replicating DNA elements that constitute major fractions of eukaryote genomes. Their ability to transpose can modify the genome structure with potentially deleterious effects. To repress TE activity, host cells have developed numerous strategies, including epigenetic pathways, such as DNA methylation or histone modifications. Although TE neo-insertions are mostly deleterious or neutral, they can become advantageous for the host under specific circumstances. The phenomenon leading to the appropriation of TE-derived sequences by the host is known as TE exaptation or co-option. TE exaptation can be of different natures, through the production of coding or non-coding DNA sequences with ultimately an adaptive benefit for the host. In this review, we first give new insights into the silencing pathways controlling TE activity. We then discuss a model to explain how, under specific environmental conditions, TEs are unleashed, leading to a TE burst and neo-insertions, with potential benefits for the host. Finally, we review our current knowledge of coding and non-coding TE exaptation by providing several examples in various organisms and describing a method to identify TE co-option events.
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Affiliation(s)
- Melody Nicolau
- LGDP-UMR5096, CNRS, 66860 Perpignan, France; (M.N.); (N.P.)
- LGDP-UMR5096, Université de Perpignan Via Domitia, 66860 Perpignan, France
| | - Nathalie Picault
- LGDP-UMR5096, CNRS, 66860 Perpignan, France; (M.N.); (N.P.)
- LGDP-UMR5096, Université de Perpignan Via Domitia, 66860 Perpignan, France
| | - Guillaume Moissiard
- LGDP-UMR5096, CNRS, 66860 Perpignan, France; (M.N.); (N.P.)
- LGDP-UMR5096, Université de Perpignan Via Domitia, 66860 Perpignan, France
- Correspondence:
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7
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Flavell RB. Perspective: 50 years of plant chromosome biology. PLANT PHYSIOLOGY 2021; 185:731-753. [PMID: 33604616 PMCID: PMC8133586 DOI: 10.1093/plphys/kiaa108] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/15/2020] [Accepted: 12/04/2020] [Indexed: 06/12/2023]
Abstract
The past 50 years has been the greatest era of plant science discovery, and most of the discoveries have emerged from or been facilitated by our knowledge of plant chromosomes. At last we have descriptive and mechanistic outlines of the information in chromosomes that programs plant life. We had almost no such information 50 years ago when few had isolated DNA from any plant species. The important features of genes have been revealed through whole genome comparative genomics and testing of variants using transgenesis. Progress has been enabled by the development of technologies that had to be invented and then become widely available. Arabidopsis (Arabidopsis thaliana) and rice (Oryza sativa) have played extraordinary roles as model species. Unexpected evolutionary dramas were uncovered when learning that chromosomes have to manage constantly the vast numbers of potentially mutagenic families of transposons and other repeated sequences. The chromatin-based transcriptional and epigenetic mechanisms that co-evolved to manage the evolutionary drama as well as gene expression and 3-D nuclear architecture have been elucidated these past 20 years. This perspective traces some of the major developments with which I have become particularly familiar while seeking ways to improve crop plants. I draw some conclusions from this look-back over 50 years during which the scientific community has (i) exposed how chromosomes guard, readout, control, recombine, and transmit information that programs plant species, large and small, weed and crop, and (ii) modified the information in chromosomes for the purposes of genetic, physiological, and developmental analyses and plant improvement.
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Affiliation(s)
- Richard B Flavell
- International Wheat Yield Partnership, 1500 Research Parkway, College Station, TX 77843, USA
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8
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Recent advancement of NGS technologies to detect active transposable elements in plants. Genes Genomics 2021; 43:289-294. [PMID: 33555503 DOI: 10.1007/s13258-021-01040-z] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2020] [Accepted: 01/04/2021] [Indexed: 12/28/2022]
Abstract
BACKGROUND Unlike peoples' belief that transposable elements (TEs) are "junk DNAs" or "genomic parasites", TEs are essential genomic elements that bring about genetic diversity and enable evolution of a species. In fact, transposons are major constituent of chromosome in crop genomes, particularly in major cereal crops, the primary type of which is long terminal repeat (LTR) retrotransposon. Since TE mobilization can be controlled by specific environmental stimulation and as the result can generate novel genetic variations, it has been suggested that controlled mobilization of TEs can be a plausible method for crop breeding. To achieve this goal, series of sequencing techniques have been recently established to identify TEs that are active in mobility. These methods target and detect extrachromosomal DNAs (ecDNAs), which are final products of integration. The newly identified TEs by these methods exhibit strong transpositional activity which can generate novel genetic diversity and provide useful breeding resources. CONCLUSIONS In this mini review, we summarize and introduce ALE-seq, mobilome-seq, and VLP DNA-seq techniques employed to detect active TEs in plants.
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9
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Lunardon A, Johnson NR, Hagerott E, Phifer T, Polydore S, Coruh C, Axtell MJ. Integrated annotations and analyses of small RNA-producing loci from 47 diverse plants. Genome Res 2020; 30:497-513. [PMID: 32179590 PMCID: PMC7111516 DOI: 10.1101/gr.256750.119] [Citation(s) in RCA: 39] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2019] [Accepted: 01/27/2020] [Indexed: 01/25/2023]
Abstract
Plant endogenous small RNAs (sRNAs) are important regulators of gene expression. There are two broad categories of plant sRNAs: microRNAs (miRNAs) and endogenous short interfering RNAs (siRNAs). MicroRNA loci are relatively well-annotated but compose only a small minority of the total sRNA pool; siRNA locus annotations have lagged far behind. Here, we used a large data set of published and newly generated sRNA sequencing data (1333 sRNA-seq libraries containing more than 20 billion reads) and a uniform bioinformatic pipeline to produce comprehensive sRNA locus annotations of 47 diverse plants, yielding more than 2.7 million sRNA loci. The two most numerous classes of siRNA loci produced mainly 24- and 21-nucleotide (nt) siRNAs, respectively. Most often, 24-nt-dominated siRNA loci occurred in intergenic regions, especially at the 5′-flanking regions of protein-coding genes. In contrast, 21-nt-dominated siRNA loci were most often derived from double-stranded RNA precursors copied from spliced mRNAs. Genic 21-nt-dominated loci were especially common from disease resistance genes, including from a large number of monocots. Individual siRNA sequences of all types showed very little conservation across species, whereas mature miRNAs were more likely to be conserved. We developed a web server where our data and several search and analysis tools are freely accessible.
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Affiliation(s)
- Alice Lunardon
- Department of Biology, The Pennsylvania State University, University Park, Pennsylvania 16802, USA
| | - Nathan R Johnson
- Department of Biology, The Pennsylvania State University, University Park, Pennsylvania 16802, USA.,Huck Institutes of the Life Sciences, The Pennsylvania State University, University Park, Pennsylvania 16802, USA
| | - Emily Hagerott
- Department of Biology, Knox College, Galesburg, Illinois 61401, USA
| | - Tamia Phifer
- Department of Biology, Knox College, Galesburg, Illinois 61401, USA
| | - Seth Polydore
- Department of Biology, The Pennsylvania State University, University Park, Pennsylvania 16802, USA.,Huck Institutes of the Life Sciences, The Pennsylvania State University, University Park, Pennsylvania 16802, USA
| | - Ceyda Coruh
- Department of Biology, The Pennsylvania State University, University Park, Pennsylvania 16802, USA.,Huck Institutes of the Life Sciences, The Pennsylvania State University, University Park, Pennsylvania 16802, USA
| | - Michael J Axtell
- Department of Biology, The Pennsylvania State University, University Park, Pennsylvania 16802, USA.,Huck Institutes of the Life Sciences, The Pennsylvania State University, University Park, Pennsylvania 16802, USA
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10
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Hatje K, Mühlhausen S, Simm D, Kollmar M. The Protein-Coding Human Genome: Annotating High-Hanging Fruits. Bioessays 2019; 41:e1900066. [PMID: 31544971 DOI: 10.1002/bies.201900066] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2019] [Revised: 08/07/2019] [Indexed: 12/19/2022]
Abstract
The major transcript variants of human protein-coding genes are annotated to a certain degree of accuracy combining manual curation, transcript data, and proteomics evidence. However, there is considerable disagreement on the annotation of about 2000 genes-they can be protein-coding, noncoding, or pseudogenes-and on the annotation of most of the predicted alternative transcripts. Pure transcriptome mapping approaches seem to be limited in discriminating functional expression from noise. These limitations have partially been overcome by dedicated algorithms to detect alternative spliced micro-exons and wobble splice variants. Recently, knowledge about splice mechanism and protein structure are incorporated into an algorithm to predict neighboring homologous exons, often spliced in a mutually exclusive manner. Predicted exons are evaluated by transcript data, structural compatibility, and evolutionary conservation, revealing hundreds of novel coding exons and splice mechanism re-assignments. The emerging human pan-genome is necessitating distinctive annotations incorporating differences between individuals and between populations.
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Affiliation(s)
- Klas Hatje
- Roche Pharmaceutical Research and Early Development, Pharmaceutical Sciences, Roche Innovation Center Basel, F. Hoffmann-La Roche Ltd., Grenzacherstr. 124, 4070, Basel, Switzerland
| | - Stefanie Mühlhausen
- Group Systems Biology of Motor Proteins, Department of NMR-based Structural Biology, Max-Planck-Institute for Biophysical Chemistry, Am Fassberg 11, 37077, Göttingen, Germany
| | - Dominic Simm
- Group Systems Biology of Motor Proteins, Department of NMR-based Structural Biology, Max-Planck-Institute for Biophysical Chemistry, Am Fassberg 11, 37077, Göttingen, Germany.,Theoretical Computer Science and Algorithmic Methods, Institute of Computer Science, Georg-August-University Göttingen, Goldschmidtstr. 7, 37077, Göttingen, Germany
| | - Martin Kollmar
- Group Systems Biology of Motor Proteins, Department of NMR-based Structural Biology, Max-Planck-Institute for Biophysical Chemistry, Am Fassberg 11, 37077, Göttingen, Germany
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11
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He Y, Tian S, Tian P. Fundamental asymmetry of insertions and deletions in genomes size evolution. J Theor Biol 2019; 482:109983. [PMID: 31445016 DOI: 10.1016/j.jtbi.2019.08.014] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2019] [Revised: 08/18/2019] [Accepted: 08/21/2019] [Indexed: 12/01/2022]
Abstract
The origin of large genomes that underlies the long standing "C-value enigma" is only partially explained by selfish DNA. We investigated insertions and deletions (indels) of nucleotides and discussed their relevance in size evolution of random biological sequences (RBS) and genomes. By developing a probabilistic model of RBS based on size evolution of expandable sites in a thought perfect genome, it was found that insertion bias engenders exponential increase of average RBS sizes. When combined with existing large segments of genome that are not subject to selection pressure (e.g. selfish DNA), such insertion bias results in explosive expansion of genomes, and therefore helps explain the "C value enigma" besides selfish DNA. Such increase of RBS size is caused by the fundamental asymmetry of indels, with insertions result in more available sites and deletions result in less deletable nucleotides. In qualitative agreement with the size distribution of known genomes, tails of RBS size distributions exhibit exponential decay with probabilities of larger RBS segments being smaller. Unsurprisingly, a slight deletion bias (higher deletions probabilities) results in a slow decrease of average RBS size and may lead to their eventual vanishing. Contrary to intuition, strictly balanced insertion and deletion results in linearly increasing instead of completely fixed RBS size. Nonetheless, such slow linear increase of average RBS sizes with time are small in magnitude and are consequently not influential on genome size evolution, and certainly not a major contributor for the "C-value enigma". Our model suggested that insertion bias of nucleotides may provide complementary explanation for large genomes besides selfish DNA. The fundamental indel asymmetry is applicable for all forms of genomic insertions and deletions. Long-lasting exponential increase of genome size present energy and material requirement that is impossible to sustain. We therefore concluded that if there were explosively accelerating expansion caused by significant effective insertion bias for any survival species, it must have occurred sporadically. Our model also provided an explanation for the observed proportional evolution of genome size.
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Affiliation(s)
- Yang He
- School of Life Sciences, Jilin University Changchun, 2699 Qianjin Street, China 130012
| | - Suyan Tian
- Division of Clinical Epidemiology, First Hospital of The Jilin University, 71 Xinmin Street, Changchun, China, 130021.
| | - Pu Tian
- School of Life Sciences and MOE Key laboratory of Molecular Enzymology and Engineering, Jilin University 2699 Qianjin Street, Changchun, China 130012.
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12
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Huynh S, Marcussen T, Felber F, Parisod C. Hybridization preceded radiation in diploid wheats. Mol Phylogenet Evol 2019; 139:106554. [PMID: 31288105 DOI: 10.1016/j.ympev.2019.106554] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2019] [Revised: 07/03/2019] [Accepted: 07/03/2019] [Indexed: 01/06/2023]
Abstract
Evolutionary relationships among the Aegilops-Triticum relatives of cultivated wheats have been difficult to resolve owing to incomplete lineage sorting and reticulate evolution. Recent studies have suggested that the wheat D-genome lineage (progenitor of Ae. tauschii) originated through homoploid hybridization between the A-genome lineage (progenitor of Triticum s.str.) and the B-genome lineage (progenitor of Ae. speltoides). This scenario of reticulation has been debated, calling for adequate phylogenetic analyses based on comprehensive sampling. To reconstruct the evolution of Aegilops-Triticum diploids, we here combined high-throughput sequencing of 38 nuclear low-copy loci of multiple accessions of all 13 species with inferences of the species phylogeny using the full-parameterized MCMC_SEQ method. Phylogenies recovered a monophyletic Aegilops-Triticum lineage that began diversifying ~6.6 Ma ago and gave rise to four sublineages, i.e. the A- (2 species), B- (1 species), D- (9 species) and T- (Ae. mutica) genome lineage. Full-parameterized phylogenies as well as patterns of tree dilation and tree compression supported a hybrid origin of the D-genome lineage from A and B ~3.0-4.0 Ma ago, and did not indicate additional hybridization events. Conflicting ABBA-BABA tests suggestive of further reticulation were shown here to result from ancestral population structure rather than hybridization. This comprehensive and dated phylogeny of wheat relatives indicates that the origin of the hybrid D-genome was followed by intense diversification into the majority of extant diploid as well as allopolyploid wild wheats.
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Affiliation(s)
- Stella Huynh
- Institute of Biology, University of Neuchâtel, Switzerland
| | - Thomas Marcussen
- Centre for Ecological and Evolutionary Synthesis, University of Oslo, Norway
| | - François Felber
- Institute of Biology, University of Neuchâtel, Switzerland; Musée et Jardins botaniques cantonaux de Lausanne et Pont-de-Nant, Switzerland
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13
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Bourque G, Burns KH, Gehring M, Gorbunova V, Seluanov A, Hammell M, Imbeault M, Izsvák Z, Levin HL, Macfarlan TS, Mager DL, Feschotte C. Ten things you should know about transposable elements. Genome Biol 2018; 19:199. [PMID: 30454069 PMCID: PMC6240941 DOI: 10.1186/s13059-018-1577-z] [Citation(s) in RCA: 643] [Impact Index Per Article: 107.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Transposable elements (TEs) are major components of eukaryotic genomes. However, the extent of their impact on genome evolution, function, and disease remain a matter of intense interrogation. The rise of genomics and large-scale functional assays has shed new light on the multi-faceted activities of TEs and implies that they should no longer be marginalized. Here, we introduce the fundamental properties of TEs and their complex interactions with their cellular environment, which are crucial to understanding their impact and manifold consequences for organismal biology. While we draw examples primarily from mammalian systems, the core concepts outlined here are relevant to a broad range of organisms.
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Affiliation(s)
- Guillaume Bourque
- Department of Human Genetics, McGill University, Montréal, Québec, H3A 0G1, Canada.
- Canadian Center for Computational Genomics, McGill University, Montréal, Québec, H3A 0G1, Canada.
| | - Kathleen H Burns
- Department of Pathology, Johns Hopkins University School of Medicine, Baltimore, MD, 21205, USA
| | - Mary Gehring
- Whitehead Institute for Biomedical Research and Department of Biology, Massachusetts Institute of Technology, Cambridge, MA, 02142, USA
| | - Vera Gorbunova
- Department of Biology, University of Rochester, Rochester, NY, 14627, USA
| | - Andrei Seluanov
- Department of Biology, University of Rochester, Rochester, NY, 14627, USA
| | - Molly Hammell
- Cold Spring Harbor Laboratory, Cold Spring Harbor, NY, 11724, USA
| | - Michaël Imbeault
- Department of Genetics, University of Cambridge, Cambridge, CB2 3EH, UK
| | - Zsuzsanna Izsvák
- Max Delbrück Center for Molecular Medicine in the Helmholtz Association, 13125, Berlin, Germany
| | - Henry L Levin
- The Eunice Kennedy Shriver National Institute of Child Health and Human Development, The National Institutes of Health, Bethesda, Maryland, USA
| | - Todd S Macfarlan
- The Eunice Kennedy Shriver National Institute of Child Health and Human Development, The National Institutes of Health, Bethesda, Maryland, USA
| | - Dixie L Mager
- Terry Fox Laboratory, British Columbia Cancer Agency and Department of Medical Genetics, University of BC, Vancouver, BC, V5Z1L3, Canada
| | - Cédric Feschotte
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY, 14850, USA.
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14
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Huang HR, Liu JJ, Xu Y, Lascoux M, Ge XJ, Wright SI. Homeologue-specific expression divergence in the recently formed tetraploid Capsella bursa-pastoris (Brassicaceae). THE NEW PHYTOLOGIST 2018; 220:624-635. [PMID: 30028022 DOI: 10.1111/nph.15299] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/03/2018] [Accepted: 05/31/2018] [Indexed: 06/08/2023]
Abstract
Following allopolyploid formation, extensive genome evolution occurs, with the eventual loss of many homeologous gene copies. Although this process of diploidization has occurred many times independently, the evolutionary forces determining the probability and rate of gene loss remain poorly understood. Here, we conduct genome and transcriptome sequencing in a broad sample of Chinese accessions of Capsella bursa-pastoris, a recently formed allotetraploid. Our whole genome data reveal three groups of these accessions: an Eastern group from low-altitude regions, a Western group from high-altitude regions, and a much more differentiated Northwestern group. Population differentiation in total expression was limited among closely related populations; by contrast, the relative expression of the two homeologous copies closely mirrors the genome-wide SNP divergence. Consistent with this, we observe a negative correlation between expression changes in the two homeologues. However, genes showing population genomic evidence for adaptive evolution do not show an enrichment for expression divergence between homeologues, providing no clear evidence for adaptive shifts in relative gene expression. Overall, these patterns suggest that neutral drift may contribute to the population differentiation in the expression of the homeologues, and drive eventual gene loss over longer periods of time.
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Affiliation(s)
- Hui-Run Huang
- Key Laboratory of Plant Resources Conservation and Sustainable Utilization, South China Botanical Garden, the Chinese Academy of Sciences, Guangzhou, 510650, China
- Guangdong Provincial Key Laboratory of Applied Botany, South China Botanical Garden, the Chinese Academy of Sciences, Guangzhou, 510650, China
| | - Jia-Jia Liu
- Key Laboratory of Plant Resources Conservation and Sustainable Utilization, South China Botanical Garden, the Chinese Academy of Sciences, Guangzhou, 510650, China
- Guangdong Provincial Key Laboratory of Applied Botany, South China Botanical Garden, the Chinese Academy of Sciences, Guangzhou, 510650, China
| | - Yong Xu
- Key Laboratory of Plant Resources Conservation and Sustainable Utilization, South China Botanical Garden, the Chinese Academy of Sciences, Guangzhou, 510650, China
- Guangdong Provincial Key Laboratory of Applied Botany, South China Botanical Garden, the Chinese Academy of Sciences, Guangzhou, 510650, China
| | - Martin Lascoux
- Department of Ecology and Genetics, Evolutionary Biology Centre, Science for Life Laboratory, Uppsala University, Uppsala, 75236, Sweden
| | - Xue-Jun Ge
- Key Laboratory of Plant Resources Conservation and Sustainable Utilization, South China Botanical Garden, the Chinese Academy of Sciences, Guangzhou, 510650, China
- Guangdong Provincial Key Laboratory of Applied Botany, South China Botanical Garden, the Chinese Academy of Sciences, Guangzhou, 510650, China
| | - Stephen I Wright
- Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, M5S 3B2, ON, Canada
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15
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Baduel P, Bray S, Vallejo-Marin M, Kolář F, Yant L. The “Polyploid Hop”: Shifting Challenges and Opportunities Over the Evolutionary Lifespan of Genome Duplications. Front Ecol Evol 2018. [DOI: 10.3389/fevo.2018.00117] [Citation(s) in RCA: 68] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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16
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Song MJ, Schaack S. Evolutionary Conflict between Mobile DNA and Host Genomes. Am Nat 2018; 192:263-273. [DOI: 10.1086/698482] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
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17
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Morata J, Tormo M, Alexiou KG, Vives C, Ramos-Onsins SE, Garcia-Mas J, Casacuberta JM. The Evolutionary Consequences of Transposon-Related Pericentromer Expansion in Melon. Genome Biol Evol 2018; 10:1584-1595. [PMID: 29901717 PMCID: PMC6009578 DOI: 10.1093/gbe/evy115] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/04/2018] [Indexed: 12/16/2022] Open
Abstract
Transposable elements (TEs) are a major driver of plant genome evolution. A part from being a rich source of new genes and regulatory sequences, TEs can also affect plant genome evolution by modifying genome size and shaping chromosome structure. TEs tend to concentrate in heterochromatic pericentromeric regions and their proliferation may expand these regions. Here, we show that after the split of melon and cucumber, TEs have expanded the pericentromeric regions of melon chromosomes that, probably as a consequence, show a very low recombination frequency. In contrast, TEs have not proliferated to a high extent in cucumber, which has small TE-dense pericentromeric regions and shows a relatively constant recombination rate along chromosomes. These differences in chromosome structure also translate in differences in gene nucleotide diversity. Although gene nucleotide diversity is essentially constant along cucumber chromosomes, melon chromosomes show a bimodal pattern of genetic variability, with a gene-poor region where variability is negatively correlated with gene density. Interestingly, genes are not homogeneously distributed in melon, and the high variable low-recombining pericentromeric regions show a higher concentration of melon-specific genes whereas genes shared with cucumber and other plants are essentially found in gene-rich chromosomal arms. The results presented here suggest that melon pericentromeric regions may allow gene sequences to evolve more freely than in other chromosomal compartments which may allow new ORFs to arise and eventually be selected. These results show that TEs can drastically change the structure of chromosomes creating different chromosomal compartments imposing different constraints for gene evolution.
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Affiliation(s)
- Jordi Morata
- Center for Research in Agricultural Genomics, CRAG (CSIC-IRTA-UAB-UB), Campus UAB, Cerdanyola del Vallès, Barcelona, Spain
| | - Marc Tormo
- Center for Research in Agricultural Genomics, CRAG (CSIC-IRTA-UAB-UB), Campus UAB, Cerdanyola del Vallès, Barcelona, Spain
| | - Konstantinos G Alexiou
- Institut de Recerca i Tecnologia Agroalimentàries, Center for Research in Agricultural Genomics, CRAG (CSIC-IRTA-UAB-UB), Campus UAB, Cerdanyola del Vallès, Barcelona, Spain
| | - Cristina Vives
- Center for Research in Agricultural Genomics, CRAG (CSIC-IRTA-UAB-UB), Campus UAB, Cerdanyola del Vallès, Barcelona, Spain
| | - Sebastián E Ramos-Onsins
- Center for Research in Agricultural Genomics, CRAG (CSIC-IRTA-UAB-UB), Campus UAB, Cerdanyola del Vallès, Barcelona, Spain
| | - Jordi Garcia-Mas
- Institut de Recerca i Tecnologia Agroalimentàries, Center for Research in Agricultural Genomics, CRAG (CSIC-IRTA-UAB-UB), Campus UAB, Cerdanyola del Vallès, Barcelona, Spain
| | - Josep M Casacuberta
- Center for Research in Agricultural Genomics, CRAG (CSIC-IRTA-UAB-UB), Campus UAB, Cerdanyola del Vallès, Barcelona, Spain
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18
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Same-Sex Twin Pair Phenotypic Correlations are Consistent with Human Y Chromosome Promoting Phenotypic Heterogeneity. Evol Biol 2018. [DOI: 10.1007/s11692-018-9454-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/16/2022]
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19
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Forestan C, Farinati S, Aiese Cigliano R, Lunardon A, Sanseverino W, Varotto S. Maize RNA PolIV affects the expression of genes with nearby TE insertions and has a genome-wide repressive impact on transcription. BMC PLANT BIOLOGY 2017; 17:161. [PMID: 29025411 PMCID: PMC5639751 DOI: 10.1186/s12870-017-1108-1] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/12/2017] [Accepted: 10/04/2017] [Indexed: 05/09/2023]
Abstract
BACKGROUND RNA-directed DNA methylation (RdDM) is a plant-specific epigenetic process that relies on the RNA polymerase IV (Pol IV) for the production of 24 nucleotide small interfering RNAs (siRNA) that guide the cytosine methylation and silencing of genes and transposons. Zea mays RPD1/RMR6 gene encodes the largest subunit of Pol IV and is required for normal plant development, paramutation, transcriptional repression of certain transposable elements (TEs) and transcriptional regulation of specific alleles. RESULTS In this study we applied a total RNA-Seq approach to compare the B73 and rpd1/rmr6 leaf transcriptomes. Although previous studies indicated that loss of siRNAs production in RdDM mutants provokes a strong loss of CHH DNA methylation but not massive gene or TEs transcriptional activation in both Arabidopsis and maize, our total RNA-Seq analysis of rpd1/rmr6 transcriptome reveals that loss of Pol IV activity causes a global increase in the transcribed fraction of the maize genome. Our results point to the genes with nearby TE insertions as being the most strongly affected by Pol IV-mediated gene silencing. TEs modulation of nearby gene expression is linked to alternative methylation profiles on gene flanking regions, and these profiles are strictly dependent on specific characteristics of the TE member inserted. Although Pol IV is essential for the biogenesis of siRNAs, the genes with associated siRNA loci are less affected by the pol IV mutation. CONCLUSIONS This deep and integrated analysis of gene expression, TEs distribution, smallRNA targeting and DNA methylation levels, reveals that loss of Pol IV activity globally affects genome regulation, pointing at TEs as modulator of nearby gene expression and indicating the existence of multiple level epigenetic silencing mechanisms. Our results also suggest a predominant role of the Pol IV-mediated RdDM pathway in genome dominance regulation, and subgenome stability and evolution in maize.
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Affiliation(s)
- Cristian Forestan
- Department of Agronomy, Food, Natural resources, Animals and Environment, University of Padova, Viale dell’Università 16, 35020 Legnaro, PD Italy
| | - Silvia Farinati
- Department of Agronomy, Food, Natural resources, Animals and Environment, University of Padova, Viale dell’Università 16, 35020 Legnaro, PD Italy
| | | | - Alice Lunardon
- Department of Agronomy, Food, Natural resources, Animals and Environment, University of Padova, Viale dell’Università 16, 35020 Legnaro, PD Italy
- Present Address: Department of Biology and Huck Institutes of the Life Sciences, Penn State University, University Park, Pennsylvania, PA 16802 USA
| | | | - Serena Varotto
- Department of Agronomy, Food, Natural resources, Animals and Environment, University of Padova, Viale dell’Università 16, 35020 Legnaro, PD Italy
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20
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Vicient CM, Casacuberta JM. Impact of transposable elements on polyploid plant genomes. ANNALS OF BOTANY 2017; 120:195-207. [PMID: 28854566 PMCID: PMC5737689 DOI: 10.1093/aob/mcx078] [Citation(s) in RCA: 143] [Impact Index Per Article: 20.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/10/2017] [Accepted: 05/23/2017] [Indexed: 05/18/2023]
Abstract
BACKGROUND The growing wealth of knowledge on whole-plant genome sequences is highlighting the key role of transposable elements (TEs) in plant evolution, as a driver of drastic changes in genome size and as a source of an important number of new coding and regulatory sequences. Together with polyploidization events, TEs should thus be considered the major players in evolution of plants. SCOPE This review outlines the major mechanisms by which TEs impact plant genome evolution and how polyploidy events can affect these impacts, and vice versa. These include direct effects on genes, by providing them with new coding or regulatory sequences, an effect on the epigenetic status of the chromatin close to genes, and more subtle effects by imposing diverse evolutionary constraints to different chromosomal regions. These effects are particularly relevant after polyploidization events. Polyploidization often induces bursts of transposition probably due to a relaxation in their epigenetic control, and, in the short term, this can increase the rate of gene mutations and changes in gene regulation due to the insertion of TEs next to or into genes. Over longer times, TE bursts may induce global changes in genome structure due to inter-element recombination including losses of large genome regions and chromosomal rearrangements that reduce the genome size and the chromosome number as part of a process called diploidization. CONCLUSIONS TEs play an essential role in genome and gene evolution, in particular after polyploidization events. Polyploidization can induce TE activity that may explain part of the new phenotypes observed. TEs may also play a role in the diploidization that follows polyploidization events. However, the extent to which TEs contribute to diploidization and fractionation bias remains unclear. Investigating the multiple factors controlling TE dynamics and the nature of ancient and recent polyploid genomes may shed light on these processes.
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Affiliation(s)
- Carlos M. Vicient
- Center for Research in Agricultural Genomics, CRAG (CSIC-IRTA-UAB-UB), Campus UAB, Cerdanyola del Vallès, 08193 Barcelona, Spain
- For correspondence. E-mail
| | - Josep M. Casacuberta
- Center for Research in Agricultural Genomics, CRAG (CSIC-IRTA-UAB-UB), Campus UAB, Cerdanyola del Vallès, 08193 Barcelona, Spain
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21
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Alix K, Gérard PR, Schwarzacher T, Heslop-Harrison JS(P. Polyploidy and interspecific hybridization: partners for adaptation, speciation and evolution in plants. ANNALS OF BOTANY 2017; 120:183-194. [PMID: 28854567 PMCID: PMC5737848 DOI: 10.1093/aob/mcx079] [Citation(s) in RCA: 167] [Impact Index Per Article: 23.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/14/2017] [Accepted: 05/31/2017] [Indexed: 05/15/2023]
Abstract
BACKGROUND Polyploidy or whole-genome duplication is now recognized as being present in almost all lineages of higher plants, with multiple rounds of polyploidy occurring in most extant species. The ancient evolutionary events have been identified through genome sequence analysis, while recent hybridization events are found in about half of the world's crops and wild species. Building from this new paradigm for understanding plant evolution, the papers in this Special Issue address questions about polyploidy in ecology, adaptation, reproduction and speciation of wild and cultivated plants from diverse ecosystems. Other papers, including this review, consider genomic aspects of polyploidy. APPROACHES Discovery of the evolutionary consequences of new, evolutionarily recent and ancient polyploidy requires a range of approaches. Large-scale studies of both single species and whole ecosystems, with hundreds to tens of thousands of individuals, sometimes involving 'garden' or transplant experiments, are important for studying adaptation. Molecular studies of genomes are needed to measure diversity in genotypes, showing ancestors, the nature and number of polyploidy and backcross events that have occurred, and allowing analysis of gene expression and transposable element activation. Speciation events and the impact of reticulate evolution require comprehensive phylogenetic analyses and can be assisted by resynthesis of hybrids. In this Special Issue, we include studies ranging in scope from experimental and genomic, through ecological to more theoretical. CONCLUSIONS The success of polyploidy, displacing the diploid ancestors of almost all plants, is well illustrated by the huge angiosperm diversity that is assumed to originate from recurrent polyploidization events. Strikingly, polyploidization often occurred prior to or simultaneously with major evolutionary transitions and adaptive radiation of species, supporting the concept that polyploidy plays a predominant role in bursts of adaptive speciation. Polyploidy results in immediate genetic redundancy and represents, with the emergence of new gene functions, an important source of novelty. Along with recombination, gene mutation, transposon activity and chromosomal rearrangement, polyploidy and whole-genome duplication act as drivers of evolution and divergence in plant behaviour and gene function, enabling diversification, speciation and hence plant evolution.
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Affiliation(s)
- Karine Alix
- GQE – Le Moulon, INRA, Université Paris-Sud, CNRS, AgroParisTech, Université Paris-Saclay, 91190 Gif-sur-Yvette, France
- For correspondence. E-mail
| | - Pierre R. Gérard
- GQE – Le Moulon, INRA, Université Paris-Sud, CNRS, AgroParisTech, Université Paris-Saclay, 91190 Gif-sur-Yvette, France
| | - Trude Schwarzacher
- Department of Genetics and Genome Biology, University of Leicester, Leicester, UK
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22
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Sequencing the extrachromosomal circular mobilome reveals retrotransposon activity in plants. PLoS Genet 2017; 13:e1006630. [PMID: 28212378 PMCID: PMC5338827 DOI: 10.1371/journal.pgen.1006630] [Citation(s) in RCA: 89] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2016] [Revised: 03/06/2017] [Accepted: 02/10/2017] [Indexed: 11/19/2022] Open
Abstract
Retrotransposons are mobile genetic elements abundant in plant and animal genomes. While efficiently silenced by the epigenetic machinery, they can be reactivated upon stress or during development. Their level of transcription not reflecting their transposition ability, it is thus difficult to evaluate their contribution to the active mobilome. Here we applied a simple methodology based on the high throughput sequencing of extrachromosomal circular DNA (eccDNA) forms of active retrotransposons to characterize the repertoire of mobile retrotransposons in plants. This method successfully identified known active retrotransposons in both Arabidopsis and rice material where the epigenome is destabilized. When applying mobilome-seq to developmental stages in wild type rice, we identified PopRice as a highly active retrotransposon producing eccDNA forms in the wild type endosperm. The mobilome-seq strategy opens new routes for the characterization of a yet unexplored fraction of plant genomes.
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23
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Michael TP, Bryant D, Gutierrez R, Borisjuk N, Chu P, Zhang H, Xia J, Zhou J, Peng H, El Baidouri M, Ten Hallers B, Hastie AR, Liang T, Acosta K, Gilbert S, McEntee C, Jackson SA, Mockler TC, Zhang W, Lam E. Comprehensive definition of genome features in Spirodela polyrhiza by high-depth physical mapping and short-read DNA sequencing strategies. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2017; 89:617-635. [PMID: 27754575 DOI: 10.1111/tpj.13400] [Citation(s) in RCA: 70] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/10/2016] [Revised: 10/05/2016] [Accepted: 10/07/2016] [Indexed: 05/15/2023]
Abstract
Spirodela polyrhiza is a fast-growing aquatic monocot with highly reduced morphology, genome size and number of protein-coding genes. Considering these biological features of Spirodela and its basal position in the monocot lineage, understanding its genome architecture could shed light on plant adaptation and genome evolution. Like many draft genomes, however, the 158-Mb Spirodela genome sequence has not been resolved to chromosomes, and important genome characteristics have not been defined. Here we deployed rapid genome-wide physical maps combined with high-coverage short-read sequencing to resolve the 20 chromosomes of Spirodela and to empirically delineate its genome features. Our data revealed a dramatic reduction in the number of the rDNA repeat units in Spirodela to fewer than 100, which is even fewer than that reported for yeast. Consistent with its unique phylogenetic position, small RNA sequencing revealed 29 Spirodela-specific microRNA, with only two being shared with Elaeis guineensis (oil palm) and Musa balbisiana (banana). Combining DNA methylation data and small RNA sequencing enabled the accurate prediction of 20.5% long terminal repeats (LTRs) that doubled the previous estimate, and revealed a high Solo:Intact LTR ratio of 8.2. Interestingly, we found that Spirodela has the lowest global DNA methylation levels (9%) of any plant species tested. Taken together our results reveal a genome that has undergone reduction, likely through eliminating non-essential protein coding genes, rDNA and LTRs. In addition to delineating the genome features of this unique plant, the methodologies described and large-scale genome resources from this work will enable future evolutionary and functional studies of this basal monocot family.
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Affiliation(s)
- Todd P Michael
- Department of Plant Biology & Pathology, Rutgers University, New Brunswick, NJ, USA
- IBIS Bioscience, Carlsbad, CA, USA
| | - Douglas Bryant
- IBIS Bioscience, Carlsbad, CA, USA
- Donald Danforth Center for Plant Science, St. Louis, MO, USA
| | - Ryan Gutierrez
- Department of Plant Biology & Pathology, Rutgers University, New Brunswick, NJ, USA
| | - Nikolai Borisjuk
- Department of Plant Biology & Pathology, Rutgers University, New Brunswick, NJ, USA
| | - Philomena Chu
- Department of Plant Biology & Pathology, Rutgers University, New Brunswick, NJ, USA
| | - Hanzhong Zhang
- Department of Plant Biology & Pathology, Rutgers University, New Brunswick, NJ, USA
| | - Jing Xia
- Institute for Systems Biology, Jianghan University, Wuhan, China
- Department of Computer Science and Engineering, Washington University, St. Louis, MO, USA
| | - Junfei Zhou
- Institute for Systems Biology, Jianghan University, Wuhan, China
| | - Hai Peng
- Institute for Systems Biology, Jianghan University, Wuhan, China
| | - Moaine El Baidouri
- Center for Applied Genetic Technologies, University of Georgia, Athens, GA, USA
| | | | | | | | - Kenneth Acosta
- Department of Plant Biology & Pathology, Rutgers University, New Brunswick, NJ, USA
| | - Sarah Gilbert
- Department of Plant Biology & Pathology, Rutgers University, New Brunswick, NJ, USA
| | | | - Scott A Jackson
- Center for Applied Genetic Technologies, University of Georgia, Athens, GA, USA
| | - Todd C Mockler
- Donald Danforth Center for Plant Science, St. Louis, MO, USA
| | - Weixiong Zhang
- Institute for Systems Biology, Jianghan University, Wuhan, China
- Department of Computer Science and Engineering, Washington University, St. Louis, MO, USA
| | - Eric Lam
- Department of Plant Biology & Pathology, Rutgers University, New Brunswick, NJ, USA
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24
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Freeling M. Picking up the Ball at the K/Pg Boundary: The Distribution of Ancient Polyploidies in the Plant Phylogenetic Tree as a Spandrel of Asexuality with Occasional Sex. THE PLANT CELL 2017; 29:202-206. [PMID: 28213362 PMCID: PMC5354197 DOI: 10.1105/tpc.16.00836] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/07/2016] [Revised: 01/05/2017] [Accepted: 02/15/2017] [Indexed: 05/23/2023]
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25
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Schubert I, Vu GTH. Genome Stability and Evolution: Attempting a Holistic View. TRENDS IN PLANT SCIENCE 2016; 21:749-757. [PMID: 27427334 DOI: 10.1016/j.tplants.2016.06.003] [Citation(s) in RCA: 94] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/24/2016] [Revised: 06/06/2016] [Accepted: 06/15/2016] [Indexed: 05/02/2023]
Abstract
The reason why the DNA content, chromosome number and shape, and gene content of eukaryotic genomes vary independently remains a matter of speculation. The same is true for the questions of whether there is a general tendency for increase or decrease of genome size and chromosome number and whether genome size and/or chromosome number have an adaptive value and, if so, what this value is. Here we assume that three strategies of genome evolution (shrinkage, expansion, and equilibrium) have developed to find the optimal balance between genomic stability and plasticity. We suggest various modes of DNA double-strand break (DSB) repair in combination with whole-genome duplication (WGD) and dysploid chromosome number alteration to explain the different strategies of genome size and karyotype evolution.
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Affiliation(s)
- Ingo Schubert
- Leibniz Institute of Plant Genetics and Crop Plant Research (IPK), D 06466 Gatersleben, Stadt Seeland, Germany.
| | - Giang T H Vu
- Leibniz Institute of Plant Genetics and Crop Plant Research (IPK), D 06466 Gatersleben, Stadt Seeland, Germany
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26
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Freeling M, Scanlon MJ, Fowler JE. Fractionation and subfunctionalization following genome duplications: mechanisms that drive gene content and their consequences. Curr Opin Genet Dev 2015; 35:110-8. [PMID: 26657818 DOI: 10.1016/j.gde.2015.11.002] [Citation(s) in RCA: 66] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2015] [Revised: 11/09/2015] [Accepted: 11/09/2015] [Indexed: 12/11/2022]
Abstract
A gene's duplication relaxes selection. Loss of duplicate, low-function DNA (fractionation) sometimes follows, mostly by deletion in plants, but mostly via the pseudogene pathway in fish and other clades with smaller population sizes. Subfunctionalization--the founding term of the Xfunctionalization lexicon--while not the general cause of differences in duplicate gene retention, becomes primary as the number of a gene's cis-regulatory sites increases. Balanced gene drive explains retention for the average gene. Both maintenance-of-balance and subfunctionalization drive gene content nonrandomly, and currently fall outside of our accepted Theory of Evolution. The 'typical' mutation encountered by a gene duplicate is not a neutral loss-of-function; dominant mutations (Muller's lexicon; these are not neutral) abound, and confound X functionalization terms like 'neofunctionalization'. Confusion of words may cause confusion of thought. As with many plants, fish tetraploidies provide a higher throughput surrogate-genetic method to infer function from human and other vertebrate ENCODE-like regulatory sites.
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Affiliation(s)
- Michael Freeling
- Department of Plant and Microbial Biology, Univ. California, Berkeley, CA 94720, United States.
| | - Michael J Scanlon
- Section of Plant Biology, Cornell University, Ithaca, NY 14853, United States
| | - John E Fowler
- Department of Botany and Plant Pathology, Oregon State University, Corvallis, OR 97331, United States
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27
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VanBuren R, Bryant D, Edger PP, Tang H, Burgess D, Challabathula D, Spittle K, Hall R, Gu J, Lyons E, Freeling M, Bartels D, Ten Hallers B, Hastie A, Michael TP, Mockler TC. Single-molecule sequencing of the desiccation-tolerant grass Oropetium thomaeum. Nature 2015; 527:508-11. [PMID: 26560029 DOI: 10.1038/nature15714] [Citation(s) in RCA: 192] [Impact Index Per Article: 21.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2015] [Accepted: 09/10/2015] [Indexed: 12/20/2022]
Abstract
Plant genomes, and eukaryotic genomes in general, are typically repetitive, polyploid and heterozygous, which complicates genome assembly. The short read lengths of early Sanger and current next-generation sequencing platforms hinder assembly through complex repeat regions, and many draft and reference genomes are fragmented, lacking skewed GC and repetitive intergenic sequences, which are gaining importance due to projects like the Encyclopedia of DNA Elements (ENCODE). Here we report the whole-genome sequencing and assembly of the desiccation-tolerant grass Oropetium thomaeum. Using only single-molecule real-time sequencing, which generates long (>16 kilobases) reads with random errors, we assembled 99% (244 megabases) of the Oropetium genome into 625 contigs with an N50 length of 2.4 megabases. Oropetium is an example of a 'near-complete' draft genome which includes gapless coverage over gene space as well as intergenic sequences such as centromeres, telomeres, transposable elements and rRNA clusters that are typically unassembled in draft genomes. Oropetium has 28,466 protein-coding genes and 43% repeat sequences, yet with 30% more compact euchromatic regions it is the smallest known grass genome. The Oropetium genome demonstrates the utility of single-molecule real-time sequencing for assembling high-quality plant and other eukaryotic genomes, and serves as a valuable resource for the plant comparative genomics community.
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Affiliation(s)
- Robert VanBuren
- Donald Danforth Plant Science Center, St Louis, Missouri 63132, USA
| | - Doug Bryant
- Donald Danforth Plant Science Center, St Louis, Missouri 63132, USA
| | - Patrick P Edger
- Department of Plant and Microbial Biology, University of California Berkeley, Berkeley, California 94720, USA.,Department of Horticulture, Michigan State University, East Lansing, Michigan 48823, USA
| | - Haibao Tang
- iPlant Collaborative, School of Plant Sciences, University of Arizona, Tucson, Arizona 85721, USA.,Center for Genomics and Biotechnology, Haixia Institute of Science and Technology (HIST), Fujian Agriculture and Forestry University, Fuzhou 350002, China
| | - Diane Burgess
- Department of Plant and Microbial Biology, University of California Berkeley, Berkeley, California 94720, USA
| | | | | | - Richard Hall
- Pacific Biosciences, Menlo Park, California 94025, USA
| | - Jenny Gu
- Pacific Biosciences, Menlo Park, California 94025, USA
| | - Eric Lyons
- iPlant Collaborative, School of Plant Sciences, University of Arizona, Tucson, Arizona 85721, USA
| | - Michael Freeling
- Department of Plant and Microbial Biology, University of California Berkeley, Berkeley, California 94720, USA
| | | | | | - Alex Hastie
- BioNano Genomics, San Diego, California 92121, USA
| | | | - Todd C Mockler
- Donald Danforth Plant Science Center, St Louis, Missouri 63132, USA
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Burgess DG, Xu J, Freeling M. Advances in understanding cis regulation of the plant gene with an emphasis on comparative genomics. CURRENT OPINION IN PLANT BIOLOGY 2015; 27:141-7. [PMID: 26247124 DOI: 10.1016/j.pbi.2015.07.001] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/01/2015] [Revised: 06/26/2015] [Accepted: 07/07/2015] [Indexed: 05/07/2023]
Abstract
The plant gene model remains largely an extrapolation from animals, with the cis functional unit, the gene, cast as a dynamic looping structure. Molecular genetics with model plants continues to make advances; highlighted here are quantitative-occupancy results from the Arabidopsis thaliana (Arabidopsis) Phytochrome-Interacting bHLH transcription Factors (PIF) quartet. Compared to this complex snapshot, results from chromatin occupancy and other Encyclopedia of DNA Elements (ENCODE)-like approaches increase our transcription factor-motif cognate library, but regulation cannot by itself be inferred from binding. Complementary published Arabidopsis conserved noncoding sequence lists are compared, evaluated, merged, and released. Comparative genomic approaches have identified a cis modifier of a gene's expression-hypothetically, a transposon-based 'rheostat'-that works in all cells, times and places.
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Affiliation(s)
- Diane G Burgess
- Department of Plant and Microbial Biology, University of California, Berkeley 94720, United States.
| | - Jie Xu
- Maize Research Institute, Sichuan Agricultural University, Wenjiang, Sichuan 611130, China
| | - Michael Freeling
- Department of Plant and Microbial Biology, University of California, Berkeley 94720, United States
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