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Roelfs KU, Känel A, Twyman RM, Prüfer D, Schulze Gronover C. Epigenetic variation in early and late flowering plants of the rubber-producing Russian dandelion Taraxacum koksaghyz provides insights into the regulation of flowering time. Sci Rep 2024; 14:4283. [PMID: 38383610 PMCID: PMC10881582 DOI: 10.1038/s41598-024-54862-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2023] [Accepted: 02/17/2024] [Indexed: 02/23/2024] Open
Abstract
The Russian dandelion (Taraxacum koksaghyz) grows in temperate zones and produces large amounts of poly(cis-1,4-isoprene) in its roots, making it an attractive alternative source of natural rubber. Most T. koksaghyz plants require vernalization to trigger flower development, whereas early flowering varieties that have lost their vernalization dependence are more suitable for breeding and domestication. To provide insight into the regulation of flowering time in T. koksaghyz, we induced epigenetic variation by in vitro cultivation and applied epigenomic and transcriptomic analysis to the resulting early flowering plants and late flowering controls, allowing us to identify differences in methylation patterns and gene expression that correlated with flowering. This led to the identification of candidate genes homologous to vernalization and photoperiodism response genes in other plants, as well as epigenetic modifications that may contribute to the control of flower development. Some of the candidate genes were homologous to known floral regulators, including those that directly or indirectly regulate the major flowering control gene FT. Our atlas of genes can be used as a starting point to investigate mechanisms that control flowering time in T. koksaghyz in greater detail and to develop new breeding varieties that are more suited to domestication.
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Affiliation(s)
- Kai-Uwe Roelfs
- Fraunhofer Institute for Molecular Biology and Applied Ecology IME, 48149, Münster, Germany
| | - Andrea Känel
- Institute of Plant Biology and Biotechnology, University of Münster, 48143, Münster, Germany
| | | | - Dirk Prüfer
- Fraunhofer Institute for Molecular Biology and Applied Ecology IME, 48149, Münster, Germany
- Institute of Plant Biology and Biotechnology, University of Münster, 48143, Münster, Germany
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Kojima KK. Helenus and Ajax, Two Groups of Non-Autonomous LTR Retrotransposons, Represent a New Type of Small RNA Gene-Derived Mobile Elements. BIOLOGY 2024; 13:119. [PMID: 38392337 PMCID: PMC10886601 DOI: 10.3390/biology13020119] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/14/2023] [Revised: 02/06/2024] [Accepted: 02/10/2024] [Indexed: 02/24/2024]
Abstract
Terminal repeat retrotransposons in miniature (TRIMs) are short non-autonomous long terminal repeat (LTR) retrotransposons found from various eukaryotes. Cassandra is a unique TRIM lineage which contains a 5S rRNA-derived sequence in its LTRs. Here, two new groups of TRIMs, designated Helenus and Ajax, are reported based on bioinformatics analysis and the usage of Repbase. Helenus is found from fungi, animals, and plants, and its LTRs contain a tRNA-like sequence. It includes two LTRs and between them, a primer-binding site (PBS) and polypurine tract (PPT) exist. Fungal and plant Helenus generate 5 bp target site duplications (TSDs) upon integration, while animal Helenus generates 4 bp TSDs. Ajax includes a 5S rRNA-derived sequence in its LTR and is found from two nemertean genomes. Ajax generates 5 bp TSDs upon integration. These results suggest that despite their unique promoters, Helenus and Ajax are TRIMs whose transposition is dependent on autonomous LTR retrotransposon. These TRIMs can originate through an insertion of SINE in an LTR of TRIM. The discovery of Helenus and Ajax suggests the presence of TRIMs with a promoter for RNA polymerase III derived from a small RNA gene, which is here collectively termed TRIMp3.
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Affiliation(s)
- Kenji K Kojima
- Genetic Information Research Institute, Cupertino, CA 95014, USA
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Laspisa D, Illa-Berenguer E, Bang S, Schmitz RJ, Parrott W, Wallace J. Mining the Utricularia gibba genome for insulator-like elements for genetic engineering. FRONTIERS IN PLANT SCIENCE 2023; 14:1279231. [PMID: 38023853 PMCID: PMC10663240 DOI: 10.3389/fpls.2023.1279231] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/17/2023] [Accepted: 10/16/2023] [Indexed: 12/01/2023]
Abstract
Introduction Gene expression is often controlled via cis-regulatory elements (CREs) that modulate the production of transcripts. For multi-gene genetic engineering and synthetic biology, precise control of transcription is crucial, both to insulate the transgenes from unwanted native regulation and to prevent readthrough or cross-regulation of transgenes within a multi-gene cassette. To prevent this activity, insulator-like elements, more properly referred to as transcriptional blockers, could be inserted to separate the transgenes so that they are independently regulated. However, only a few validated insulator-like elements are available for plants, and they tend to be larger than ideal. Methods To identify additional potential insulator-like sequences, we conducted a genome-wide analysis of Utricularia gibba (humped bladderwort), one of the smallest known plant genomes, with genes that are naturally close together. The 10 best insulator-like candidates were evaluated in vivo for insulator-like activity. Results We identified a total of 4,656 intergenic regions with expression profiles suggesting insulator-like activity. Comparisons of these regions across 45 other plant species (representing Monocots, Asterids, and Rosids) show low levels of syntenic conservation of these regions. Genome-wide analysis of unmethylated regions (UMRs) indicates ~87% of the targeted regions are unmethylated; however, interpretation of this is complicated because U. gibba has remarkably low levels of methylation across the genome, so that large UMRs frequently extend over multiple genes and intergenic spaces. We also could not identify any conserved motifs among our selected intergenic regions or shared with existing insulator-like elements for plants. Despite this lack of conservation, however, testing of 10 selected intergenic regions for insulator-like activity found two elements on par with a previously published element (EXOB) while being significantly smaller. Discussion Given the small number of insulator-like elements currently available for plants, our results make a significant addition to available tools. The high hit rate (2 out of 10) also implies that more useful sequences are likely present in our selected intergenic regions; additional validation work will be required to identify which will be most useful for plant genetic engineering.
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Affiliation(s)
- Daniel Laspisa
- Center for Applied Genetic Technologies, University of Georgia, Athens, GA, United States
| | - Eudald Illa-Berenguer
- Center for Applied Genetic Technologies, University of Georgia, Athens, GA, United States
| | - Sohyun Bang
- Institute of Bioinformatics, University of Georgia, Athens, GA, United States
| | - Robert J. Schmitz
- Department of Genetics, University of Georgia, Athens, GA, United States
| | - Wayne Parrott
- Center for Applied Genetic Technologies, University of Georgia, Athens, GA, United States
- Department of Crop & Soil Science & Institute of Plant Breeding, Genetics and Genomics, University of Georgia, Athens, GA, United States
| | - Jason Wallace
- Center for Applied Genetic Technologies, University of Georgia, Athens, GA, United States
- Institute of Bioinformatics, University of Georgia, Athens, GA, United States
- Department of Crop & Soil Science & Institute of Plant Breeding, Genetics and Genomics, University of Georgia, Athens, GA, United States
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Orozco-Arias S, Dupeyron M, Gutiérrez-Duque D, Tabares-Soto R, Guyot R. High nucleotide similarity of three Copia lineage LTR retrotransposons among plant genomes. Genome 2023; 66:51-61. [PMID: 36623262 DOI: 10.1139/gen-2022-0026] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Transposable elements (TEs) are mobile elements found in the majority of eukaryotic genomes. TEs deeply impact the structure and evolution of chromosomes and can induce mutations affecting coding genes. In plants, the major group of TEs is long terminal repeat retrotransposons (LTR-RTs). They are classified into superfamilies (Gypsy, Copia) and subclassified into lineages. Horizontal transfer (HT), defined as the nonsexual transmission of genetic material between species, is a process allowing LTR-RTs to invade a new genome. Although this phenomenon was considered rare, recent studies demonstrate numerous transfers of LTR-RTs. This study aims to determine which LTR-RT lineages are shared with high similarity among 69 plant genomes. We identified and classified 88 450 LTR-RTs and determined 143 cases of high similarities between pairs of genomes. Most of them involved three Copia lineages (Oryco/Ivana, Retrofit/Ale, and Tork/Tar/Ikeros). A detailed analysis of three cases of high similarities involving Tork/Tar/Ikeros group shows an uneven distribution in the phylogeny of the elements and incongruence with between phylogenetic trees topologies, indicating they could be originated from HTs. Overall, our results suggest that LTR-RT Copia lineages share outstanding similarity between distant species and may likely be involved in HT mechanisms more frequent than initially estimated.
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Affiliation(s)
- Simon Orozco-Arias
- Department of Computer Sciences, Universidad Autónoma de Manizales, Colombia.,Department of Systems and Informatics, Universidad de Caldas, Colombia
| | - Mathilde Dupeyron
- Institut de Recherche pour le Développement, IRD, CIRAD, Université de Montpellier, France
| | | | - Reinel Tabares-Soto
- Department of Systems and Informatics, Universidad de Caldas, Colombia.,Department of Electronics and Automatization, Universidad Autónoma de Manizales, Colombia
| | - Romain Guyot
- Institut de Recherche pour le Développement, IRD, CIRAD, Université de Montpellier, France.,Department of Electronics and Automatization, Universidad Autónoma de Manizales, Colombia
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Viroids and Viroid-like Circular RNAs: Do They Descend from Primordial Replicators? LIFE (BASEL, SWITZERLAND) 2022; 12:life12010103. [PMID: 35054497 PMCID: PMC8781251 DOI: 10.3390/life12010103] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/21/2021] [Revised: 01/10/2022] [Accepted: 01/11/2022] [Indexed: 01/09/2023]
Abstract
Viroids are a unique class of plant pathogens that consist of small circular RNA molecules, between 220 and 450 nucleotides in size. Viroids encode no proteins and are the smallest known infectious agents. Viroids replicate via the rolling circle mechanism, producing multimeric intermediates which are cleaved to unit length either by ribozymes formed from both polarities of the viroid genomic RNA or by coopted host RNAses. Many viroid-like small circular RNAs are satellites of plant RNA viruses. Ribozyviruses, represented by human hepatitis delta virus, are larger viroid-like circular RNAs that additionally encode the viral nucleocapsid protein. It has been proposed that viroids are direct descendants of primordial RNA replicons that were present in the hypothetical RNA world. We argue, however, that much later origin of viroids, possibly, from recently discovered mobile genetic elements known as retrozymes, is a far more parsimonious evolutionary scenario. Nevertheless, viroids and viroid-like circular RNAs are minimal replicators that are likely to be close to the theoretical lower limit of replicator size and arguably comprise the paradigm for replicator emergence. Thus, although viroid-like replicators are unlikely to be direct descendants of primordial RNA replicators, the study of the diversity and evolution of these ultimate genetic parasites can yield insights into the earliest stages of the evolution of life.
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Methylation patterns of Tf2 retrotransposons linked to rapid adaptive stress response in the brown planthopper (Nilaparvata lugens). Genomics 2021; 113:4214-4226. [PMID: 34774681 DOI: 10.1016/j.ygeno.2021.11.007] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2021] [Revised: 10/12/2021] [Accepted: 11/07/2021] [Indexed: 11/23/2022]
Abstract
Transposable elements (TEs) exhibit vast diversity across insect orders and are one of the major factors driving insect evolution and speciation. Presence of TEs can be both beneficial and deleterious to their host. While it is well-established that TEs impact life-history traits, adaptations and survivability of insects under hostile environments, the influence of the ecological niche on TE-landscape remains unclear. Here, we analysed the dynamics of Tf2 retrotransposons in the brown planthopper (BPH), under environmental fluctuations. BPH, a major pest of rice, is found in almost all rice-growing ecosystems. We believe genome plasticity, attributed to TEs, has allowed BPH to adapt and colonise novel ecological niches. Our study revealed bimodal age-distribution for Tf2 elements in BPH, indicating the occurrence of two major transpositional events in its evolutionary history and their contribution in shaping BPH genome. While TEs can provide genome flexibility and facilitate adaptations, they impose massive load on the genome. Hence, we investigated the involvement of methylation in modulating transposition in BPH. We performed comparative analyses of the methylation patterns of Tf2 elements in BPH feeding on resistant- and susceptible-rice varieties, and also under pesticide stress, across different life-stages. Results confirmed that methylation, particularly in non-CG context, is involved in TE regulation and dynamics under stress. Furthermore, we observed differential methylation for BPH adults and nymphs, emphasising the importance of screening juvenile life-stages in understanding adaptive-stress-responses in insects. Collectively, this study enhances our understanding of the role of transposons in influencing the evolutionary trajectory and survival strategies of BPH across generations.
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Targeted designing functional markers revealed the role of retrotransposon derived miRNAs as mobile epigenetic regulators in adaptation responses of pistachio. Sci Rep 2021; 11:19751. [PMID: 34611187 PMCID: PMC8492636 DOI: 10.1038/s41598-021-98402-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2021] [Accepted: 09/06/2021] [Indexed: 02/08/2023] Open
Abstract
We developed novel miRNA-based markers based on salt responsive miRNA sequences to detect polymorphisms in miRNA sequences and locations. The validation of 76 combined miRNA + miRNA and miRNA + ISSR markers in the three extreme pistachio populations led to the identification of three selected markers that could link salt tolerance phenotype to genotype and divided pistachio genotypes and Pistacia species into three clusters. This novel functional marker system, in addition to more efficient performance, has higher polymorphisms than previous miRNA-based marker systems. The functional importance of the target gene of five miRNAs in the structure of the three selected markers in regulation of different genes such as ECA2, ALA10, PFK, PHT1;4, PTR3, KUP2, GRAS, TCP, bHLH, PHD finger, PLATZ and genes involved in developmental, signaling and biosynthetic processes shows that the polymorphism associated with these selected miRNAs can make a significant phenotypic difference between salt sensitive and tolerant pistachio genotypes. The sequencing results of selected bands showed the presence of conserved miRNAs in the structure of the mitochondrial genome. Further notable findings of this study are that the sequences of PCR products of two selected markers were annotated as Gypsy and Copia retrotransposable elements. The transposition of retrotransposons with related miRNAs by increasing the number of miRNA copies and changing their location between nuclear and organellar genomes can affect the regulatory activity of these molecules. These findings show the crucial role of retrotransposon-derived miRNAs as mobile epigenetic regulators between intracellular genomes in regulating salt stress responses as well as creating new and tolerant phenotypes for adaptation to environmental conditions.
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Orozco-Arias S, Jaimes PA, Candamil MS, Jiménez-Varón CF, Tabares-Soto R, Isaza G, Guyot R. InpactorDB: A Classified Lineage-Level Plant LTR Retrotransposon Reference Library for Free-Alignment Methods Based on Machine Learning. Genes (Basel) 2021; 12:genes12020190. [PMID: 33525408 PMCID: PMC7910972 DOI: 10.3390/genes12020190] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2020] [Revised: 01/21/2021] [Accepted: 01/22/2021] [Indexed: 12/04/2022] Open
Abstract
Long terminal repeat (LTR) retrotransposons are mobile elements that constitute the major fraction of most plant genomes. The identification and annotation of these elements via bioinformatics approaches represent a major challenge in the era of massive plant genome sequencing. In addition to their involvement in genome size variation, LTR retrotransposons are also associated with the function and structure of different chromosomal regions and can alter the function of coding regions, among others. Several sequence databases of plant LTR retrotransposons are available for public access, such as PGSB and RepetDB, or restricted access such as Repbase. Although these databases are useful to identify LTR-RTs in new genomes by similarity, the elements of these databases are not fully classified to the lineage (also called family) level. Here, we present InpactorDB, a semi-curated dataset composed of 130,439 elements from 195 plant genomes (belonging to 108 plant species) classified to the lineage level. This dataset has been used to train two deep neural networks (i.e., one fully connected and one convolutional) for the rapid classification of these elements. In lineage-level classification approaches, we obtain up to 98% performance, indicated by the F1-score, precision and recall scores.
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Affiliation(s)
- Simon Orozco-Arias
- Department of Computer Science, Universidad Autónoma de Manizales, 170002 Manizales, Colombia; (P.A.J.); (M.S.C.)
- Department of Systems and Informatics, Universidad de Caldas, 170002 Manizales, Colombia;
- Correspondence: (S.O.-A.); (R.G.)
| | - Paula A. Jaimes
- Department of Computer Science, Universidad Autónoma de Manizales, 170002 Manizales, Colombia; (P.A.J.); (M.S.C.)
| | - Mariana S. Candamil
- Department of Computer Science, Universidad Autónoma de Manizales, 170002 Manizales, Colombia; (P.A.J.); (M.S.C.)
| | | | - Reinel Tabares-Soto
- Department of Electronics and Automation, Universidad Autónoma de Manizales, 170002 Manizales, Colombia;
| | - Gustavo Isaza
- Department of Systems and Informatics, Universidad de Caldas, 170002 Manizales, Colombia;
| | - Romain Guyot
- Department of Electronics and Automation, Universidad Autónoma de Manizales, 170002 Manizales, Colombia;
- Institut de Recherche pour le Développement, CIRAD, University of Montpellier, 34394 Montpellier, France
- Correspondence: (S.O.-A.); (R.G.)
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Maiwald S, Weber B, Seibt KM, Schmidt T, Heitkam T. The Cassandra retrotransposon landscape in sugar beet (Beta vulgaris) and related Amaranthaceae: recombination and re-shuffling lead to a high structural variability. ANNALS OF BOTANY 2021; 127:91-109. [PMID: 33009553 PMCID: PMC7750724 DOI: 10.1093/aob/mcaa176] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/28/2020] [Accepted: 09/28/2020] [Indexed: 05/26/2023]
Abstract
BACKGROUND AND AIMS Plant genomes contain many retrotransposons and their derivatives, which are subject to rapid sequence turnover. As non-autonomous retrotransposons do not encode any proteins, they experience reduced selective constraints leading to their diversification into multiple families, usually limited to a few closely related species. In contrast, the non-coding Cassandra terminal repeat retrotransposons in miniature (TRIMs) are widespread in many plants. Their hallmark is a conserved 5S rDNA-derived promoter in their long terminal repeats (LTRs). As sugar beet (Beta vulgaris) has a well-described LTR retrotransposon landscape, we aim to characterize TRIMs in beet and related genomes. METHODS We identified Cassandra retrotransposons in the sugar beet reference genome and characterized their structural relationships. Genomic organization, chromosomal localization, and distribution of Cassandra-TRIMs across the Amaranthaceae were verified by Southern and fluorescent in situ hybridization. KEY RESULTS All 638 Cassandra sequences in the sugar beet genome contain conserved LTRs and thus constitute a single family. Nevertheless, variable internal regions required a subdivision into two Cassandra subfamilies within B. vulgaris. The related Chenopodium quinoa harbours a third subfamily. These subfamilies vary in their distribution within Amaranthaceae genomes, their insertion times and the degree of silencing by small RNAs. Cassandra retrotransposons gave rise to many structural variants, such as solo LTRs or tandemly arranged Cassandra retrotransposons. These Cassandra derivatives point to an interplay of template switch and recombination processes - mechanisms that likely caused Cassandra's subfamily formation and diversification. CONCLUSIONS We traced the evolution of Cassandra in the Amaranthaceae and detected a considerable variability within the short internal regions, whereas the LTRs are strongly conserved in sequence and length. Presumably these hallmarks make Cassandra a prime target for unequal recombination, resulting in the observed structural diversity, an example of the impact of LTR-mediated evolutionary mechanisms on the host genome.
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Affiliation(s)
- Sophie Maiwald
- Institute of Botany, Technische Universität Dresden, Dresden, Germany
| | - Beatrice Weber
- Institute of Botany, Technische Universität Dresden, Dresden, Germany
| | - Kathrin M Seibt
- Institute of Botany, Technische Universität Dresden, Dresden, Germany
| | - Thomas Schmidt
- Institute of Botany, Technische Universität Dresden, Dresden, Germany
| | - Tony Heitkam
- Institute of Botany, Technische Universität Dresden, Dresden, Germany
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A Singular and Widespread Group of Mobile Genetic Elements: RNA Circles with Autocatalytic Ribozymes. Cells 2020; 9:cells9122555. [PMID: 33260527 PMCID: PMC7761336 DOI: 10.3390/cells9122555] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2020] [Revised: 11/19/2020] [Accepted: 11/26/2020] [Indexed: 11/16/2022] Open
Abstract
Circular DNAs, such as most prokaryotic and phage genomes, are a frequent form of nucleic acids, whereas circular RNAs had been regarded as unusual macromolecules until very recently. The first reported RNA circles were the family of small infectious genomes of viroids and circular RNA (circRNA) satellites of plant viruses, some of which contain small self-cleaving RNA motifs, such as the hammerhead (HHR) and hairpin ribozymes. A similar infectious circRNA, the unique human hepatitis delta virus (HDV), is another viral satellite that also encodes self-cleaving motifs called HDV ribozymes. Very recently, different animals have been reported to contain HDV-like circRNAs with typical HDV ribozymes, but also conserved HHR motifs, as we describe here. On the other hand, eukaryotic and prokaryotic genomes encode sequences able to self-excise as circRNAs, like the autocatalytic Group I and II introns, which are widespread genomic mobile elements. In the 1990s, the first circRNAs encoded in a mammalian genome were anecdotally reported, but their abundance and importance have not been unveiled until recently. These gene-encoded circRNAs are produced by events of alternative splicing in a process generally known as backsplicing. However, we have found a second natural pathway of circRNA expression conserved in numerous plant and animal genomes, which efficiently promotes the accumulation of small non-coding RNA circles through the participation of HHRs. Most of these genome-encoded circRNAs with HHRs are the transposition intermediates of a novel family of non-autonomous retrotransposons called retrozymes, with intriguing potential as new forms of gene regulation.
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Setiawan AB, Teo CH, Kikuchi S, Sassa H, Kato K, Koba T. Chromosomal Locations of a Non-LTR Retrotransposon, Menolird18, in Cucumis melo and Cucumis sativus, and Its Implication on Genome Evolution of Cucumis Species. Cytogenet Genome Res 2020; 160:554-564. [DOI: 10.1159/000511119] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2020] [Accepted: 07/07/2020] [Indexed: 11/19/2022] Open
Abstract
Mobile elements are major regulators of genome evolution through their effects on genome size and chromosome structure in higher organisms. Non-long terminal repeat (non-LTR) retrotransposons, one of the subclasses of transposons, are specifically inserted into repetitive DNA sequences. While studies on the insertion of non-LTR retrotransposons into ribosomal RNA genes and other repetitive DNA sequences have been reported in the animal kingdom, studies in the plant kingdom are limited. Here, using FISH, we confirmed that <i>Menolird18</i>, a member of LINE (long interspersed nuclear element) in non-LTR retrotransposons and found in <i>Cucumis melo</i>, was inserted into ITS and ETS (internal and external transcribed spacers) regions of 18S rDNA in melon and cucumber. Beside the 18S rDNA regions, <i>Menolird18</i> was also detected in all centromeric regions of melon, while it was located at pericentromeric and sub-telomeric regions in cucumber. The fact that FISH signals of <i>Menolird18</i> were found in centromeric and rDNA regions of mitotic chromosomes suggests that <i>Menolird18</i> is a rDNA and centromere-specific non-LTR retrotransposon in melon. Our findings are the first report on a non-LTR retrotransposon that is highly conserved in 2 different plant species, melon and cucumber. The clear distinction of chromosomal localization of <i>Menolird18</i> in melon and cucumber implies that it might have been involved in the evolutionary processes of the melon (<i>C. melo</i>) and cucumber (<i>C. sativus</i>) genomes.
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The unusual dRemp retrotransposon is abundant, highly mutagenic, and mobilized only in the second pollen mitosis of some maize lines. Proc Natl Acad Sci U S A 2020; 117:18091-18098. [PMID: 32661148 DOI: 10.1073/pnas.2010234117] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
The frequent mutations recovered recently from the pollen of select maize lines resulted from the meiotic mobilization of specific low-copy number long-terminal repeat (LTR) retrotransposons, which differ among lines. Mutations that arise at male meiosis produce kernels with concordant mutant phenotypes in both endosperm and embryo because the two sperms that participate in double fertilization are genetically identical. Those are in a majority. However, a small minority of kernels with a mutant endosperm carry a nonconcordant normal embryo, pointing to a postmeiotic or microgametophytic origin. In this study, we have identified the basis for those nonconcordant mutations. We find that all are produced by transposition of a defective LTR retrotransposon that we have termed dRemp (defective retroelement mobile in pollen). This element has several unique properties. Unlike the mutagenic LTR retrotransposons identified previously, dRemp is present in hundreds of copies in all sequenced lines. It seems to transpose only at the second pollen mitosis because all dRemp insertion mutants are nonconcordant yet recoverable in either the endosperm or the embryo. Although it does not move in most lines, dRemp is highly mobile in the Corn Belt inbred M14, identified earlier by breeders as being highly unstable. Lastly, it can be recovered in an array of structures, ranging from solo LTRs to tandem dRemp repeats containing several internal LTRs, suggestive of extensive recombination during retrotransposition. These results shed further light on the spontaneous mutation process and on the possible basis for inbred instability in maize.
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Orozco-Arias S, Isaza G, Guyot R. Retrotransposons in Plant Genomes: Structure, Identification, and Classification through Bioinformatics and Machine Learning. Int J Mol Sci 2019; 20:E3837. [PMID: 31390781 PMCID: PMC6696364 DOI: 10.3390/ijms20153837] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2019] [Revised: 07/31/2019] [Accepted: 08/02/2019] [Indexed: 01/26/2023] Open
Abstract
Transposable elements (TEs) are genomic units able to move within the genome of virtually all organisms. Due to their natural repetitive numbers and their high structural diversity, the identification and classification of TEs remain a challenge in sequenced genomes. Although TEs were initially regarded as "junk DNA", it has been demonstrated that they play key roles in chromosome structures, gene expression, and regulation, as well as adaptation and evolution. A highly reliable annotation of these elements is, therefore, crucial to better understand genome functions and their evolution. To date, much bioinformatics software has been developed to address TE detection and classification processes, but many problematic aspects remain, such as the reliability, precision, and speed of the analyses. Machine learning and deep learning are algorithms that can make automatic predictions and decisions in a wide variety of scientific applications. They have been tested in bioinformatics and, more specifically for TEs, classification with encouraging results. In this review, we will discuss important aspects of TEs, such as their structure, importance in the evolution and architecture of the host, and their current classifications and nomenclatures. We will also address current methods and their limitations in identifying and classifying TEs.
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Affiliation(s)
- Simon Orozco-Arias
- Department of Computer Science, Universidad Autónoma de Manizales, Manizales 170001, Colombia
- Department of Systems and Informatics, Universidad de Caldas, Manizales 170001, Colombia
| | - Gustavo Isaza
- Department of Systems and Informatics, Universidad de Caldas, Manizales 170001, Colombia
| | - Romain Guyot
- Department of Electronics and Automatization, Universidad Autónoma de Manizales, Manizales 170001, Colombia.
- Institut de Recherche pour le Développement, CIRAD, University Montpellier, 34000 Montpellier, France.
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Sahebi M, Hanafi MM, van Wijnen AJ, Rice D, Rafii MY, Azizi P, Osman M, Taheri S, Bakar MFA, Isa MNM, Noor YM. Contribution of transposable elements in the plant's genome. Gene 2018; 665:155-166. [PMID: 29684486 DOI: 10.1016/j.gene.2018.04.050] [Citation(s) in RCA: 43] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2017] [Revised: 04/04/2018] [Accepted: 04/18/2018] [Indexed: 12/26/2022]
Abstract
Plants maintain extensive growth flexibility under different environmental conditions, allowing them to continuously and rapidly adapt to alterations in their environment. A large portion of many plant genomes consists of transposable elements (TEs) that create new genetic variations within plant species. Different types of mutations may be created by TEs in plants. Many TEs can avoid the host's defense mechanisms and survive alterations in transposition activity, internal sequence and target site. Thus, plant genomes are expected to utilize a variety of mechanisms to tolerate TEs that are near or within genes. TEs affect the expression of not only nearby genes but also unlinked inserted genes. TEs can create new promoters, leading to novel expression patterns or alternative coding regions to generate alternate transcripts in plant species. TEs can also provide novel cis-acting regulatory elements that act as enhancers or inserts within original enhancers that are required for transcription. Thus, the regulation of plant gene expression is strongly managed by the insertion of TEs into nearby genes. TEs can also lead to chromatin modifications and thereby affect gene expression in plants. TEs are able to generate new genes and modify existing gene structures by duplicating, mobilizing and recombining gene fragments. They can also facilitate cellular functions by sharing their transposase-coding regions. Hence, TE insertions can not only act as simple mutagens but can also alter the elementary functions of the plant genome. Here, we review recent discoveries concerning the contribution of TEs to gene expression in plant genomes and discuss the different mechanisms by which TEs can affect plant gene expression and reduce host defense mechanisms.
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Affiliation(s)
- Mahbod Sahebi
- Laboratory of Climate-Smart Food Crop Production, Institute of Tropical Agriculture and Food Security, Universiti Putra Malaysia, 43400 Serdang, Selangor, Malaysia.
| | - Mohamed M Hanafi
- Laboratory of Climate-Smart Food Crop Production, Institute of Tropical Agriculture and Food Security, Universiti Putra Malaysia, 43400 Serdang, Selangor, Malaysia; Laboratory of Plantation Science and Technology, Institute of Plantation Studies, Universiti Putra Malaysia, 43400 Serdang, Selangor, Malaysia; Department of Land Management, Faculty of Agriculture, Universiti Putra Malaysia, 43400 Serdang, Selangor, Malaysia.
| | | | - David Rice
- Department of Molecular Biology & Biotecnology, University of Sheffield, United Kingdom
| | - M Y Rafii
- Laboratory of Climate-Smart Food Crop Production, Institute of Tropical Agriculture and Food Security, Universiti Putra Malaysia, 43400 Serdang, Selangor, Malaysia
| | - Parisa Azizi
- Department of Crop Science, Faculty of Agriculture, Universiti Putra Malaysia, 43400 Serdang, Selangor, Malaysia
| | - Mohamad Osman
- Department of Crop Science, Faculty of Agriculture, Universiti Putra Malaysia, 43400 Serdang, Selangor, Malaysia
| | - Sima Taheri
- Department of Crop Science, Faculty of Agriculture, Universiti Putra Malaysia, 43400 Serdang, Selangor, Malaysia
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15
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Ou S, Jiang N. LTR_retriever: A Highly Accurate and Sensitive Program for Identification of Long Terminal Repeat Retrotransposons. PLANT PHYSIOLOGY 2018; 176:1410-1422. [PMID: 29233850 PMCID: PMC5813529 DOI: 10.1104/pp.17.01310] [Citation(s) in RCA: 552] [Impact Index Per Article: 92.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/13/2017] [Accepted: 12/10/2017] [Indexed: 05/18/2023]
Abstract
Long terminal repeat retrotransposons (LTR-RTs) are prevalent in plant genomes. The identification of LTR-RTs is critical for achieving high-quality gene annotation. Based on the well-conserved structure, multiple programs were developed for the de novo identification of LTR-RTs; however, these programs are associated with low specificity and high false discovery rates. Here, we report LTR_retriever, a multithreading-empowered Perl program that identifies LTR-RTs and generates high-quality LTR libraries from genomic sequences. LTR_retriever demonstrated significant improvements by achieving high levels of sensitivity (91%), specificity (97%), accuracy (96%), and precision (90%) in rice (Oryza sativa). LTR_retriever is also compatible with long sequencing reads. With 40k self-corrected PacBio reads equivalent to 4.5× genome coverage in Arabidopsis (Arabidopsis thaliana), the constructed LTR library showed excellent sensitivity and specificity. In addition to canonical LTR-RTs with 5'-TG…CA-3' termini, LTR_retriever also identifies noncanonical LTR-RTs (non-TGCA), which have been largely ignored in genome-wide studies. We identified seven types of noncanonical LTRs from 42 out of 50 plant genomes. The majority of noncanonical LTRs are Copia elements, with which the LTR is four times shorter than that of other Copia elements, which may be a result of their target specificity. Strikingly, non-TGCA Copia elements are often located in genic regions and preferentially insert nearby or within genes, indicating their impact on the evolution of genes and their potential as mutagenesis tools.
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Affiliation(s)
- Shujun Ou
- Department of Horticulture, Michigan State University, East Lansing, Michigan 48824
| | - Ning Jiang
- Department of Horticulture, Michigan State University, East Lansing, Michigan 48824
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16
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Circular RNAs Biogenesis in Eukaryotes Through Self-Cleaving Hammerhead Ribozymes. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2018; 1087:53-63. [PMID: 30259357 DOI: 10.1007/978-981-13-1426-1_5] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Circular DNAs are frequent genomic molecules, especially among the simplest life beings, whereas circular RNAs have been regarded as weird nucleic acids in biology. Now we know that eukaryotes are able to express circRNAs, mostly derived from backsplicing mechanisms, and playing different biological roles such as regulation of RNA splicing and transcription, among others. However, a second natural and highly efficient pathway for the expression in vivo of circRNAs has been recently reported, which allows the accumulation of abundant small (100-1000 nt) non-coding RNA circles through the participation of small self-cleaving RNAs or ribozymes called hammerhead ribozymes. These genome-encoded circRNAs with ribozymes seem to be a new family of small and nonautonomous retrotransposable elements of plants and animals (so-called retrozymes), which will offer functional clues to the biology and evolution of circular RNA molecules as well as new biotechnological tools in this emerging field.
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17
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de Castro Nunes R, Orozco-Arias S, Crouzillat D, Mueller LA, Strickler SR, Descombes P, Fournier C, Moine D, de Kochko A, Yuyama PM, Vanzela ALL, Guyot R. Structure and Distribution of Centromeric Retrotransposons at Diploid and Allotetraploid Coffea Centromeric and Pericentromeric Regions. FRONTIERS IN PLANT SCIENCE 2018; 9:175. [PMID: 29497436 PMCID: PMC5818461 DOI: 10.3389/fpls.2018.00175] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/20/2017] [Accepted: 01/30/2018] [Indexed: 05/18/2023]
Abstract
Centromeric regions of plants are generally composed of large array of satellites from a specific lineage of Gypsy LTR-retrotransposons, called Centromeric Retrotransposons. Repeated sequences interact with a specific H3 histone, playing a crucial function on kinetochore formation. To study the structure and composition of centromeric regions in the genus Coffea, we annotated and classified Centromeric Retrotransposons sequences from the allotetraploid C. arabica genome and its two diploid ancestors: Coffea canephora and C. eugenioides. Ten distinct CRC (Centromeric Retrotransposons in Coffea) families were found. The sequence mapping and FISH experiments of CRC Reverse Transcriptase domains in C. canephora, C. eugenioides, and C. arabica clearly indicate a strong and specific targeting mainly onto proximal chromosome regions, which can be associated also with heterochromatin. PacBio genome sequence analyses of putative centromeric regions on C. arabica and C. canephora chromosomes showed an exceptional density of one family of CRC elements, and the complete absence of satellite arrays, contrasting with usual structure of plant centromeres. Altogether, our data suggest a specific centromere organization in Coffea, contrasting with other plant genomes.
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Affiliation(s)
- Renata de Castro Nunes
- Laboratory of Cytogenetics and Plant Diversity, Department of General Biology, Center for Biological Sciences, State University of Londrina, Londrina, Brazil
| | - Simon Orozco-Arias
- Department of Electronics and Automatization, Universidad Autónoma de Manizales, Colombia
| | | | - Lukas A. Mueller
- Boyce Thompson Institute, Cornell University, Ithaca, NY, United States
| | - Suzy R. Strickler
- Boyce Thompson Institute, Cornell University, Ithaca, NY, United States
| | | | | | - Deborah Moine
- Nestlé Institute of Health Sciences, Lausanne, Switzerland
| | - Alexandre de Kochko
- Institut de Recherche pour le Développement, UMR DIADE, EvoGec, Montpellier, France
| | - Priscila M. Yuyama
- Laboratory of Cytogenetics and Plant Diversity, Department of General Biology, Center for Biological Sciences, State University of Londrina, Londrina, Brazil
| | - André L. L. Vanzela
- Laboratory of Cytogenetics and Plant Diversity, Department of General Biology, Center for Biological Sciences, State University of Londrina, Londrina, Brazil
- *Correspondence: André L. L. Vanzela
| | - Romain Guyot
- Department of Electronics and Automatization, Universidad Autónoma de Manizales, Colombia
- Institut de Recherche pour le Développement, CIRAD, Univ. Montpellier, UMR IPME, Montpellier, France
- Romain Guyot
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18
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de la Peña M, Cervera A. Circular RNAs with hammerhead ribozymes encoded in eukaryotic genomes: The enemy at home. RNA Biol 2017; 14:985-991. [PMID: 28448743 PMCID: PMC5680766 DOI: 10.1080/15476286.2017.1321730] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
A new family of non-autonomous retrotransposons with self-cleaving hammerhead ribozymes, the so called retrozymes, has recently been found encoded in diverse plant genomes. These retroelements can be actively transcribed, and their RNAs accumulate in the cells as abundant non-coding circular RNAs (circRNAs) of small size (600–1000 nt). Related circRNAs with self-cleaving ribozymes had already been described in plants, and belong to a group of infectious RNA agents with an uncertain origin: the viroids and viroid-like satellites of plant RNA viruses. These pathogenic circRNAs show many structural similarities with retrozyme circRNAs, and both have been found to occur in flowering plants as heterogeneous RNA molecules of positive and negative polarities. Taking all these data together, we hypothesize that circRNAs encoded by genomic retrozymes could have given origin to infectious circRNAs with self-cleaving ribozymes. Moreover, we propose that retrozymes in time could have evolved from the ancient family of Penelope-like retroelements, which also harbour hammerhead ribozymes. Putative retrozyme sequences with hammerhead ribozymes have been detected as well in metazoan genomes, opening the door to a common occurrence of circRNAs with self-cleaving motifs among eukaryotes.
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Affiliation(s)
- Marcos de la Peña
- a Instituto de Biología Molecular y Celular de Plantas (Consejo Superior de Investigaciones Científicas-Universitat Politècnica de València) C/ Ingeniero Fausto Elio s/n , Valencia , Spain
| | - Amelia Cervera
- a Instituto de Biología Molecular y Celular de Plantas (Consejo Superior de Investigaciones Científicas-Universitat Politècnica de València) C/ Ingeniero Fausto Elio s/n , Valencia , Spain
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19
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Cervera A, Urbina D, de la Peña M. Retrozymes are a unique family of non-autonomous retrotransposons with hammerhead ribozymes that propagate in plants through circular RNAs. Genome Biol 2016; 17:135. [PMID: 27339130 PMCID: PMC4918200 DOI: 10.1186/s13059-016-1002-4] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2016] [Accepted: 06/07/2016] [Indexed: 11/16/2022] Open
Abstract
Background Catalytic RNAs, or ribozymes, are regarded as fossils of a prebiotic RNA world that have remained in the genomes of modern organisms. The simplest ribozymes are the small self-cleaving RNAs, like the hammerhead ribozyme, which have been historically considered biological oddities restricted to some RNA pathogens. Recent data, however, indicate that small self-cleaving ribozymes are widespread in genomes, although their functions are still unknown. Results We reveal that hammerhead ribozyme sequences in plant genomes form part of a new family of small non-autonomous retrotransposons with hammerhead ribozymes, referred to as retrozymes. These elements contain two long terminal repeats of approximately 350 bp, each harbouring a hammerhead ribozyme that delimitates a variable region of 600–1000 bp with no coding capacity. Retrozymes are actively transcribed, which gives rise to heterogeneous linear and circular RNAs that accumulate differentially depending on the tissue or developmental stage of the plant. Genomic and transcriptomic retrozyme sequences are highly heterogeneous and share almost no sequence homology among species except the hammerhead ribozyme motif and two small conserved domains typical of Ty3-gypsy long terminal repeat retrotransposons. Moreover, we detected the presence of RNAs of both retrozyme polarities, which suggests events of independent RNA-RNA rolling-circle replication and evolution, similarly to that of infectious circular RNAs like viroids and viral satellite RNAs. Conclusions Our work reveals that circular RNAs with hammerhead ribozymes are frequently occurring molecules in plant and, most likely, metazoan transcriptomes, which explains the ubiquity of these genomic ribozymes and suggests a feasible source for the emergence of circular RNA plant pathogens. Electronic supplementary material The online version of this article (doi:10.1186/s13059-016-1002-4) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Amelia Cervera
- IBMCP (CSIC-UPV). C/Ingeniero Fausto Elio s/n, 46022, Valencia, Spain
| | - Denisse Urbina
- IBMCP (CSIC-UPV). C/Ingeniero Fausto Elio s/n, 46022, Valencia, Spain
| | - Marcos de la Peña
- IBMCP (CSIC-UPV). C/Ingeniero Fausto Elio s/n, 46022, Valencia, Spain.
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20
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Sigman MJ, Slotkin RK. The First Rule of Plant Transposable Element Silencing: Location, Location, Location. THE PLANT CELL 2016; 28:304-13. [PMID: 26869697 PMCID: PMC4790875 DOI: 10.1105/tpc.15.00869] [Citation(s) in RCA: 113] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/09/2015] [Revised: 12/18/2015] [Accepted: 02/10/2016] [Indexed: 05/18/2023]
Abstract
Transposable elements (TEs) are mobile units of DNA that comprise large portions of plant genomes. Besides creating mutations via transposition and contributing to genome size, TEs play key roles in chromosome architecture and gene regulation. TE activity is repressed by overlapping mechanisms of chromatin condensation, epigenetic transcriptional silencing, and targeting by small interfering RNAs. The specific regulation of different TEs, as well as their different roles in chromosome architecture and gene regulation, is specified by where on the chromosome the TE is located: near a gene, within a gene, in a pericentromere/TE island, or at the centromere core. In this Review, we investigate the silencing mechanisms responsible for inhibiting TE activity for each of these chromosomal contexts, emphasizing that chromosomal location is the first rule dictating the specific regulation of each TE.
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Affiliation(s)
- Meredith J Sigman
- Department of Molecular Genetics and Center for RNA Biology, The Ohio State University, Columbus, Ohio 43210
| | - R Keith Slotkin
- Department of Molecular Genetics and Center for RNA Biology, The Ohio State University, Columbus, Ohio 43210
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21
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Hsu YC, Wang CS, Lin YR, Wu YP. Structural Diversity of a Novel LTR Retrotransposon, RTPOSON, in the Genus Oryza. Evol Bioinform Online 2016; 12:29-40. [PMID: 26819544 PMCID: PMC4718150 DOI: 10.4137/ebo.s35158] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2015] [Revised: 11/08/2015] [Accepted: 11/16/2015] [Indexed: 11/16/2022] Open
Abstract
Retrotransposons with long terminal repeats (LTRs) are the most abundant transposable elements in plant genomes. A novel LTR retrotransposon named RTPOSON primarily occurs in the genus Oryza and in several species of the Poaceae family. RTPOSON has been identified in the Ty1-copia group of retrotransposons because two of its open reading frames encode an uncharacterized protein and UBN2_2 and zinc knuckle, respectively. More than 700 RTPOSONs were identified in Oryza genomes; 127 RTPOSONs with LTRs and gag-pol elements were classified into three subgroups. The subgroup RTPOSON_sub3 had the smallest DNA size and 97% (32/33) of RTPOSON elements from Oryza punctata are classified in this group. The insertion time of these RTPOSONs varied and their proliferation occurred within the last 8 Mya, with two bursting periods within the last 1.5–5.0 Mya. A total of 37 different orthologous insertions of RTPOSONs, with different nested transposable elements and gene fragments, were identified by comparing the genomes of ssp. japonica cv. Nipponbare and ssp. indica cv. 93–11. A part of intact RTPOSON elements was evolved independently after the divergence of indica and japonica. In addition, intact RTPOSONs and homologous fragments were preferentially retained or integrated in genic regions. This novel LTR retrotransposon, RTPOSON, might have an impact on genome evolution, genic innovation, and genetic variation.
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Affiliation(s)
- Yu-Chia Hsu
- Department of Agronomy, Chiayi Agricultural Experiment Station, Taiwan Agricultural Research Institute, Chiayi, Taiwan
| | - Chang-Sheng Wang
- Department of Agronomy, National Chung Hsing University, Taichung, Taiwan
| | - Yann-Rong Lin
- Department of Agronomy, National Taiwan University, Taipei, Taiwan
| | - Yong-Pei Wu
- Department of Agronomy, Chiayi Agricultural Experiment Station, Taiwan Agricultural Research Institute, Chiayi, Taiwan
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22
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Gao D, Li Y, Kim KD, Abernathy B, Jackson SA. Landscape and evolutionary dynamics of terminal repeat retrotransposons in miniature in plant genomes. Genome Biol 2016; 17:7. [PMID: 26781660 PMCID: PMC4717578 DOI: 10.1186/s13059-015-0867-y] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2015] [Accepted: 12/29/2015] [Indexed: 12/05/2022] Open
Abstract
Background Terminal repeat retrotransposons in miniature (TRIMs) are a unique group of small long terminal repeat retrotransposons that are difficult to identify. Thus far, only a few TRIMs have been characterized in the euphyllophytes, and their evolutionary and biological significance as well as their transposition mechanisms are poorly understood. Results Using a combination of de novo and homology-based methods, we annotate TRIMs in 48 plant genome sequences, spanning land plants to algae. The TRIMs are grouped into 156 families including 145 that were previously undefined. Notably, we identify the first TRIMs in a lycophyte and non-vascular plants. The majority of the TRIM families are highly conserved and shared within and between plant families. Unlike other long terminal repeat retrotransposons, TRIMs are enriched in or near genes; they are also targeted by sRNAs between 21 and 24 nucleotides in length, and are frequently found in CG body-methylated genes. Importantly, we also identify putative autonomous retrotransposons and very recent transpositions of a TRIM element in Oryza sativa. Conclusions We perform the most comprehensive analysis of TRIM transposons thus far and report that TRIMs are ubiquitous across plant genomes. Our results show that TRIMs are more frequently associated with large and CG body-methylated genes that have undergone strong purifying selection. Our findings also indicate that TRIMs are likely derived from internal deletions of large long terminal repeat retrotransposons. Finally, our data and methodology are important resources for the characterization and evolutionary and genomic studies of long terminal repeat retrotransposons in other genomes. Electronic supplementary material The online version of this article (doi:10.1186/s13059-015-0867-y) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Dongying Gao
- Center for Applied Genetic Technologies, University of Georgia, 111 Riverbend Road, Athens, GA, 30602, USA.
| | - Yupeng Li
- Center for Applied Genetic Technologies, University of Georgia, 111 Riverbend Road, Athens, GA, 30602, USA.
| | - Kyung Do Kim
- Center for Applied Genetic Technologies, University of Georgia, 111 Riverbend Road, Athens, GA, 30602, USA.
| | - Brian Abernathy
- Center for Applied Genetic Technologies, University of Georgia, 111 Riverbend Road, Athens, GA, 30602, USA.
| | - Scott A Jackson
- Center for Applied Genetic Technologies, University of Georgia, 111 Riverbend Road, Athens, GA, 30602, USA.
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23
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Zhao D, Ferguson AA, Jiang N. What makes up plant genomes: The vanishing line between transposable elements and genes. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2015; 1859:366-80. [PMID: 26709091 DOI: 10.1016/j.bbagrm.2015.12.005] [Citation(s) in RCA: 48] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/17/2015] [Revised: 12/09/2015] [Accepted: 12/11/2015] [Indexed: 02/07/2023]
Abstract
The ultimate source of evolution is mutation. As the largest component in plant genomes, transposable elements (TEs) create numerous types of mutations that cannot be mimicked by other genetic mechanisms. When TEs insert into genomic sequences, they influence the expression of nearby genes as well as genes unlinked to the insertion. TEs can duplicate, mobilize, and recombine normal genes or gene fragments, with the potential to generate new genes or modify the structure of existing genes. TEs also donate their transposase coding regions for cellular functions in a process called TE domestication. Despite the host defense against TE activity, a subset of TEs survived and thrived through discreet selection of transposition activity, target site, element size, and the internal sequence. Finally, TEs have established strategies to reduce the efficacy of host defense system by increasing the cost of silencing TEs. This review discusses the recent progress in the area of plant TEs with a focus on the interaction between TEs and genes.
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Affiliation(s)
- Dongyan Zhao
- Department of Horticulture, Michigan State University, 1066 Bogue Street, East Lansing, MI 48824, USA
| | - Ann A Ferguson
- Department of Horticulture, Michigan State University, 1066 Bogue Street, East Lansing, MI 48824, USA
| | - Ning Jiang
- Department of Horticulture, Michigan State University, 1066 Bogue Street, East Lansing, MI 48824, USA.
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Yin H, Du J, Wu J, Wei S, Xu Y, Tao S, Wu J, Zhang S. Genome-wide Annotation and Comparative Analysis of Long Terminal Repeat Retrotransposons between Pear Species of P. bretschneideri and P. Communis. Sci Rep 2015; 5:17644. [PMID: 26631625 PMCID: PMC4668562 DOI: 10.1038/srep17644] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2015] [Accepted: 11/03/2015] [Indexed: 12/02/2022] Open
Abstract
Recent sequencing of the Oriental pear (P. bretschneideri Rehd.) genome and the availability of the draft genome sequence of Occidental pear (P. communis L.), has provided a good opportunity to characterize the abundance, distribution, timing, and evolution of long terminal repeat retrotransposons (LTR-RTs) in these two important fruit plants. Here, a total of 7247 LTR-RTs, which can be classified into 148 families, have been identified in the assembled Oriental pear genome. Unlike in other plant genomes, approximately 90% of these elements were found to be randomly distributed along the pear chromosomes. Further analysis revealed that the amplification timeframe of elements varies dramatically in different families, super-families and lineages, and the Copia-like elements have highest activity in the recent 0.5 million years (Mys). The data also showed that two genomes evolved with similar evolutionary rates after their split from the common ancestor ~0.77–1.66 million years ago (Mya). Overall, the data provided here will be a valuable resource for further investigating the impact of transposable elements on gene structure, expression, and epigenetic modification in the pear genomes.
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Affiliation(s)
- Hao Yin
- Center of Pear Engineering Technology Research, State Key Laboratory of Crop Genetics and Germplasm Enhancement, Nanjing Agricultural University, Nanjing 210095, Jiangsu, China
| | - Jianchang Du
- Institute of Biotechnology, Jiangsu Academy of Agricultural Sciences, Nanjing 210014, Jiangsu, China
| | - Jun Wu
- Center of Pear Engineering Technology Research, State Key Laboratory of Crop Genetics and Germplasm Enhancement, Nanjing Agricultural University, Nanjing 210095, Jiangsu, China
| | - Shuwei Wei
- Center of Pear Engineering Technology Research, State Key Laboratory of Crop Genetics and Germplasm Enhancement, Nanjing Agricultural University, Nanjing 210095, Jiangsu, China
| | - Yingxiu Xu
- Institute of Biotechnology, Jiangsu Academy of Agricultural Sciences, Nanjing 210014, Jiangsu, China
| | - Shutian Tao
- Center of Pear Engineering Technology Research, State Key Laboratory of Crop Genetics and Germplasm Enhancement, Nanjing Agricultural University, Nanjing 210095, Jiangsu, China
| | - Juyou Wu
- Center of Pear Engineering Technology Research, State Key Laboratory of Crop Genetics and Germplasm Enhancement, Nanjing Agricultural University, Nanjing 210095, Jiangsu, China
| | - Shaoling Zhang
- Center of Pear Engineering Technology Research, State Key Laboratory of Crop Genetics and Germplasm Enhancement, Nanjing Agricultural University, Nanjing 210095, Jiangsu, China
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25
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Cytogenetic and Sequence Analyses of Mitochondrial DNA Insertions in Nuclear Chromosomes of Maize. G3-GENES GENOMES GENETICS 2015; 5:2229-39. [PMID: 26333837 PMCID: PMC4632043 DOI: 10.1534/g3.115.020677] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The transfer of mitochondrial DNA (mtDNA) into nuclear genomes is a regularly occurring process that has been observed in many species. Few studies, however, have focused on the variation of nuclear-mtDNA sequences (NUMTs) within a species. This study examined mtDNA insertions within chromosomes of a diverse set of Zea mays ssp. mays (maize) inbred lines by the use of fluorescence in situ hybridization. A relatively large NUMT on the long arm of chromosome 9 (9L) was identified at approximately the same position in four inbred lines (B73, M825, HP301, and Oh7B). Further examination of the similarly positioned 9L NUMT in two lines, B73 and M825, indicated that the large size of these sites is due to the presence of a majority of the mitochondrial genome; however, only portions of this NUMT (~252 kb total) were found in the publically available B73 nuclear sequence for chromosome 9. Fiber-fluorescence in situ hybridization analysis estimated the size of the B73 9L NUMT to be ~1.8 Mb and revealed that the NUMT is methylated. Two regions of mtDNA (2.4 kb and 3.3 kb) within the 9L NUMT are not present in the B73 mitochondrial NB genome; however, these 2.4-kb and 3.3-kb segments are present in other Zea mitochondrial genomes, including that of Zea mays ssp. parviglumis, a progenitor of domesticated maize.
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26
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Marcon HS, Domingues DS, Silva JC, Borges RJ, Matioli FF, Fontes MRDM, Marino CL. Transcriptionally active LTR retrotransposons in Eucalyptus genus are differentially expressed and insertionally polymorphic. BMC PLANT BIOLOGY 2015; 15:198. [PMID: 26268941 PMCID: PMC4535378 DOI: 10.1186/s12870-015-0550-1] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/23/2015] [Accepted: 06/12/2015] [Indexed: 06/01/2023]
Abstract
BACKGROUND In Eucalyptus genus, studies on genome composition and transposable elements (TEs) are particularly scarce. Nearly half of the recently released Eucalyptus grandis genome is composed by retrotransposons and this data provides an important opportunity to understand TE dynamics in Eucalyptus genome and transcriptome. RESULTS We characterized nine families of transcriptionally active LTR retrotransposons from Copia and Gypsy superfamilies in Eucalyptus grandis genome and we depicted genomic distribution and copy number in two Eucalyptus species. We also evaluated genomic polymorphism and transcriptional profile in three organs of five Eucalyptus species. We observed contrasting genomic and transcriptional behavior in the same family among different species. RLC_egMax_1 was the most prevalent family and RLC_egAngela_1 was the family with the lowest copy number. Most families of both superfamilies have their insertions occurring <3 million years, except one Copia family, RLC_egBianca_1. Protein theoretical models suggest different properties between Copia and Gypsy domains. IRAP and REMAP markers suggested genomic polymorphisms among Eucalyptus species. Using EST analysis and qRT-PCRs, we observed transcriptional activity in several tissues and in all evaluated species. In some families, osmotic stress increases transcript values. CONCLUSION Our strategy was successful in isolating transcriptionally active retrotransposons in Eucalyptus, and each family has a particular genomic and transcriptional pattern. Overall, our results show that retrotransposon activity have differentially affected genome and transcriptome among Eucalyptus species.
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Affiliation(s)
- Helena Sanches Marcon
- Departamento de Genética, Instituto de Biociências, Universidade Estadual Paulista - UNESP, Botucatu, Brazil.
- Programa de Pós-graduação em Ciências Biológicas (Genética), Universidade Estadual Paulista - UNESP, Botucatu, Brazil.
| | - Douglas Silva Domingues
- Programa de Pós-graduação em Ciências Biológicas (Genética), Universidade Estadual Paulista - UNESP, Botucatu, Brazil.
- Departamento de Botânica, Instituto de Biociências, Universidade Estadual Paulista - UNESP, Rio Claro, Brazil.
| | - Juliana Costa Silva
- Plant Biotechnology Laboratory, Instituto Agronômico do Paraná - IAPAR, Londrina, Brazil.
| | - Rafael Junqueira Borges
- Programa de Pós-graduação em Ciências Biológicas (Genética), Universidade Estadual Paulista - UNESP, Botucatu, Brazil.
- Departamento de Física e Biofísica, Instituto de Biociências, Universidade Estadual Paulista - UNESP, Botucatu, Brazil and INCTTOX-CNPq, Brazil.
| | - Fábio Filippi Matioli
- Departamento de Física e Biofísica, Instituto de Biociências, Universidade Estadual Paulista - UNESP, Botucatu, Brazil and INCTTOX-CNPq, Brazil.
| | - Marcos Roberto de Mattos Fontes
- Programa de Pós-graduação em Ciências Biológicas (Genética), Universidade Estadual Paulista - UNESP, Botucatu, Brazil.
- Departamento de Física e Biofísica, Instituto de Biociências, Universidade Estadual Paulista - UNESP, Botucatu, Brazil and INCTTOX-CNPq, Brazil.
| | - Celso Luis Marino
- Departamento de Genética, Instituto de Biociências, Universidade Estadual Paulista - UNESP, Botucatu, Brazil.
- Programa de Pós-graduação em Ciências Biológicas (Genética), Universidade Estadual Paulista - UNESP, Botucatu, Brazil.
- Instituto de Biotecnologia da UNESP - IBTEC, Botucatu, Brazil.
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Zuccolo A, Scofield DG, De Paoli E, Morgante M. The Ty1-copia LTR retroelement family PARTC is highly conserved in conifers over 200 MY of evolution. Gene 2015; 568:89-99. [PMID: 25982862 DOI: 10.1016/j.gene.2015.05.028] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2015] [Revised: 04/06/2015] [Accepted: 05/11/2015] [Indexed: 11/26/2022]
Abstract
Long Terminal Repeat retroelements (LTR-RTs) are a major component of many plant genomes. Although well studied and described in angiosperms, their features and dynamics are poorly understood in gymnosperms. Representative complete copies of a Ty1-copia element isolate in Picea abies and named PARTC were identified in six other conifer species (Picea glauca, Pinus sylvestris, Pinus taeda, Abies sibirica, Taxus baccata and Juniperus communis) covering more than 200 million years of evolution. Here we characterized the structure of this element, assessed its abundance across conifers, studied the modes and timing of its amplification, and evaluated the degree of conservation of its extant copies at nucleotide level over distant species. We demonstrated that the element is ancient, abundant, widespread and its paralogous copies are present in the genera Picea, Pinus and Abies as an LTR-RT family. The amplification leading to the extant copies of PARTC occurred over long evolutionary times spanning 10s of MY and mostly took place after the speciation of the conifers analyzed. The level of conservation of PARTC is striking and may be explained by low substitution rates and limited removal mechanisms for LTR-RTs. These PARTC features and dynamics are representative of a more general scenario for LTR-RTs in gymnosperms quite different from that characterizing the vast majority of LTR-RT elements in angiosperms.
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Affiliation(s)
- Andrea Zuccolo
- Institute of Life Sciences, Scuola Superiore Sant'Anna, 56127 Pisa, Italy; Istituto di Genomica Applicata, Via J. Linussio 51, 33100 Udine, Italy.
| | - Douglas G Scofield
- Department of Evolutionary Biology, Evolutionary Biology Centre, Uppsala University, SE-75236 Uppsala, Sweden
| | - Emanuele De Paoli
- Università degli Studi di Udine, Via delle Scienze 208, 33100 Udine, Italy
| | - Michele Morgante
- Istituto di Genomica Applicata, Via J. Linussio 51, 33100 Udine, Italy; Università degli Studi di Udine, Via delle Scienze 208, 33100 Udine, Italy
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Grandbastien MA. LTR retrotransposons, handy hitchhikers of plant regulation and stress response. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2015; 1849:403-16. [DOI: 10.1016/j.bbagrm.2014.07.017] [Citation(s) in RCA: 110] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/26/2014] [Revised: 07/21/2014] [Accepted: 07/23/2014] [Indexed: 11/30/2022]
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Luchetti A. terMITEs: miniature inverted-repeat transposable elements (MITEs) in the termite genome (Blattodea: Termitoidae). Mol Genet Genomics 2015; 290:1499-509. [PMID: 25711308 DOI: 10.1007/s00438-015-1010-1] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2014] [Accepted: 02/12/2015] [Indexed: 11/28/2022]
Abstract
Transposable elements (TEs) are discrete DNA sequences which are able to replicate and jump into different genomic locations. Miniature inverted-repeats TEs (MITEs) are non-autonomous DNA elements whose origin is still poorly understood. Recently, some MITEs were found to contain core repeats that can be arranged in tandem arrays; in some instances, these arrays have even given rise to satellite DNAs in the (peri)centromeric region of the host chromosomes. I report the discovery and analysis of three new MITEs found in the genome of several termite species (hence the name terMITEs) in two different families. For two of the MITEs (terMITE1-Tc1/mariner superfamily; terMITE2-piggyBac superfamily), evidence of past mobility was retrieved. Moreover, these two MITEs contained core repeats, 16 bp and 114 bp long respectively, exhibiting copy number variation. In terMITE2, the tandem duplication appeared associated with element degeneration, in line with a recently proposed evolutionary model on MITEs and the origin of tandem arrays. Concerning their genomic distribution, terMITE1 and terMITE3 appeared more frequently inserted close to coding regions while terMITE2 was mostly associated with TEs. Although MITEs are commonly distributed in coding regions, terMITE2 distribution is in line with that of other insects' piggyBac-related elements and of other small TEs found in termite genomes. This has been explained through insertional preference rather than through selective processes. Data presented here add to the knowledge on the poorly exploited polyneopteran genomes and will provide an interesting framework in which to study TEs' evolution and host's life history traits.
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Affiliation(s)
- Andrea Luchetti
- Dipartimento di Scienze Biologiche, Geologiche e Ambientali, Università di Bologna, via Selmi 3, 40126, Bologna, Italy,
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30
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Paszkowski J. Controlled activation of retrotransposition for plant breeding. Curr Opin Biotechnol 2015; 32:200-206. [PMID: 25615932 DOI: 10.1016/j.copbio.2015.01.003] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2014] [Revised: 12/30/2014] [Accepted: 01/05/2015] [Indexed: 12/16/2022]
Abstract
Plant genomes consist to a large extent of transposable elements (TEs), predominantly retrotransposons. Their accumulation through periodic transposition bursts has shaped the structure and regulatory organization of plant genomes, often contributing to phenotypic traits. Transposon-generated phenotypes selected by humans during plant domestication have been maintained under strict selection during subsequent plant breeding. Our knowledge of the epigenetic, environmental, and developmental regulation of TE activity has advanced considerably in recent years. Here I will consider TEs as an attractive endogenous source of genetic variation that can be liberated in a controlled fashion and thus offer novel phenotypic diversity to be selected for crop improvement.
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Affiliation(s)
- Jerzy Paszkowski
- The Sainsbury Laboratory, University of Cambridge, Cambridge CB2 1LR, United Kingdom.
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31
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Yin H, Du J, Li L, Jin C, Fan L, Li M, Wu J, Zhang S. Comparative genomic analysis reveals multiple long terminal repeats, lineage-specific amplification, and frequent interelement recombination for Cassandra retrotransposon in pear (Pyrus bretschneideri Rehd.). Genome Biol Evol 2014; 6:1423-36. [PMID: 24899073 PMCID: PMC4079214 DOI: 10.1093/gbe/evu114] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Cassandra transposable elements belong to a specific group of terminal-repeat retrotransposons in miniature (TRIM). Although Cassandra TRIM elements have been found in almost all vascular plants, detailed investigations on the nature, abundance, amplification timeframe, and evolution have not been performed in an individual genome. We therefore conducted a comprehensive analysis of Cassandra retrotransposons using the newly sequenced pear genome along with four other Rosaceae species, including apple, peach, mei, and woodland strawberry. Our data reveal several interesting findings for this particular retrotransposon family: 1) A large number of the intact copies contain three, four, or five long terminal repeats (LTRs) (∼20% in pear); 2) intact copies and solo LTRs with or without target site duplications are both common (∼80% vs. 20%) in each genome; 3) the elements exhibit an overall unbiased distribution among the chromosomes; 4) the elements are most successfully amplified in pear (5,032 copies); and 5) the evolutionary relationships of these elements vary among different lineages, species, and evolutionary time. These results indicate that Cassandra retrotransposons contain more complex structures (elements with multiple LTRs) than what we have known previously, and that frequent interelement unequal recombination followed by transposition may play a critical role in shaping and reshaping host genomes. Thus this study provides insights into the property, propensity, and molecular mechanisms governing the formation and amplification of Cassandra retrotransposons, and enhances our understanding of the structural variation, evolutionary history, and transposition process of LTR retrotransposons in plants.
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Affiliation(s)
- Hao Yin
- State Key Laboratory of Crop Genetics and Germplasm Enhancement, College of Horticulture, Nanjing Agricultural University, China
| | - Jianchang Du
- Bioinformatics Group, Institute of Industrial Crops, Jiangsu Academy of Agricultural Sciences, Nanjing, China
| | - Leiting Li
- State Key Laboratory of Crop Genetics and Germplasm Enhancement, College of Horticulture, Nanjing Agricultural University, China
| | - Cong Jin
- State Key Laboratory of Crop Genetics and Germplasm Enhancement, College of Horticulture, Nanjing Agricultural University, China
| | - Lian Fan
- State Key Laboratory of Crop Genetics and Germplasm Enhancement, College of Horticulture, Nanjing Agricultural University, China
| | - Meng Li
- State Key Laboratory of Crop Genetics and Germplasm Enhancement, College of Horticulture, Nanjing Agricultural University, China
| | - Jun Wu
- State Key Laboratory of Crop Genetics and Germplasm Enhancement, College of Horticulture, Nanjing Agricultural University, China
| | - Shaoling Zhang
- State Key Laboratory of Crop Genetics and Germplasm Enhancement, College of Horticulture, Nanjing Agricultural University, China
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Li A, Liu D, Wu J, Zhao X, Hao M, Geng S, Yan J, Jiang X, Zhang L, Wu J, Yin L, Zhang R, Wu L, Zheng Y, Mao L. mRNA and Small RNA Transcriptomes Reveal Insights into Dynamic Homoeolog Regulation of Allopolyploid Heterosis in Nascent Hexaploid Wheat. THE PLANT CELL 2014; 26:1878-1900. [PMID: 24838975 PMCID: PMC4079356 DOI: 10.1105/tpc.114.124388] [Citation(s) in RCA: 199] [Impact Index Per Article: 19.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/20/2014] [Revised: 03/28/2014] [Accepted: 04/28/2014] [Indexed: 05/18/2023]
Abstract
Nascent allohexaploid wheat may represent the initial genetic state of common wheat (Triticum aestivum), which arose as a hybrid between Triticum turgidum (AABB) and Aegilops tauschii (DD) and by chromosome doubling and outcompeted its parents in growth vigor and adaptability. To better understand the molecular basis for this success, we performed mRNA and small RNA transcriptome analyses in nascent allohexaploid wheat and its following generations, their progenitors, and the natural allohexaploid cultivar Chinese Spring, with the assistance of recently published A and D genome sequences. We found that nonadditively expressed protein-coding genes were rare but relevant to growth vigor. Moreover, a high proportion of protein-coding genes exhibited parental expression level dominance, with genes for which the total homoeolog expression level in the progeny was similar to that in T. turgidum potentially participating in development and those with similar expression to that in Ae. tauschii involved in adaptation. In addition, a high proportion of microRNAs showed nonadditive expression upon polyploidization, potentially leading to differential expression of important target genes. Furthermore, increased small interfering RNA density was observed for transposable element-associated D homoeologs in the allohexaploid progeny, which may account for biased repression of D homoeologs. Together, our data provide insights into small RNA-mediated dynamic homoeolog regulation mechanisms that may contribute to heterosis in nascent hexaploid wheat.
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Affiliation(s)
- Aili Li
- National Key Facility for Crop Gene Resources and Genetic Improvement, Institute of Crop Science, Chinese Academy of Agricultural Sciences, Beijing 100081, China
| | - Dengcai Liu
- Triticeae Research Institute, Sichuan Agricultural University, Chengdu, Sichuan 611130, China
| | - Jun Wu
- Novogene Bioinformatics Institute, Beijing 100083, China
| | - Xubo Zhao
- National Key Facility for Crop Gene Resources and Genetic Improvement, Institute of Crop Science, Chinese Academy of Agricultural Sciences, Beijing 100081, China
| | - Ming Hao
- Triticeae Research Institute, Sichuan Agricultural University, Chengdu, Sichuan 611130, China
| | - Shuaifeng Geng
- National Key Facility for Crop Gene Resources and Genetic Improvement, Institute of Crop Science, Chinese Academy of Agricultural Sciences, Beijing 100081, China
| | - Jun Yan
- Novogene Bioinformatics Institute, Beijing 100083, China
| | - Xiaoxue Jiang
- Novogene Bioinformatics Institute, Beijing 100083, China
| | - Lianquan Zhang
- Triticeae Research Institute, Sichuan Agricultural University, Chengdu, Sichuan 611130, China
| | - Junyan Wu
- National Key Facility for Crop Gene Resources and Genetic Improvement, Institute of Crop Science, Chinese Academy of Agricultural Sciences, Beijing 100081, China
| | - Lingjie Yin
- National Key Facility for Crop Gene Resources and Genetic Improvement, Institute of Crop Science, Chinese Academy of Agricultural Sciences, Beijing 100081, China
| | - Rongzhi Zhang
- National Key Facility for Crop Gene Resources and Genetic Improvement, Institute of Crop Science, Chinese Academy of Agricultural Sciences, Beijing 100081, China
| | - Liang Wu
- National Key Facility for Crop Gene Resources and Genetic Improvement, Institute of Crop Science, Chinese Academy of Agricultural Sciences, Beijing 100081, China
| | - Youliang Zheng
- Triticeae Research Institute, Sichuan Agricultural University, Chengdu, Sichuan 611130, China
| | - Long Mao
- National Key Facility for Crop Gene Resources and Genetic Improvement, Institute of Crop Science, Chinese Academy of Agricultural Sciences, Beijing 100081, China
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Uthup TK, Saha T, Ravindran M, Bini K. Impact of an intragenic retrotransposon on the structural integrity and evolution of a major isoprenoid biosynthesis pathway gene in Hevea brasiliensis. PLANT PHYSIOLOGY AND BIOCHEMISTRY : PPB 2013; 73:176-88. [PMID: 24128694 DOI: 10.1016/j.plaphy.2013.09.004] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/02/2013] [Accepted: 09/10/2013] [Indexed: 05/01/2023]
Abstract
Isoprenoids belong to a large family of structurally and functionally different natural compounds found universally from prokaryotes to higher animals and plants. In Hevea brasiliensis, the commercially important cis-polyisoprene (rubber) is synthesised as part of its defence mechanism in addition to other common isoprenoids like phytosterols, growth hormones etc. Farnesyl diphosphate synthase (FDPS) is a key enzyme in this process which catalyses the conversion of isoprene units into polyisoprene. Although prior sequence information is available, the structural variants of the FDPS gene presently existing in Hevea population are largely unknown. Since gene structure has a major role in gene regulation, extensive sequence analysis of this gene from different genotypes was carried out to identify the prevailing structural variants. We identified several SNPs and large indels which were associated with a partial transposable element (TE). Modification of key regulatory motifs and splice sites induced by the retroelement was also identified in the first intron. Screening of popular rubber clones, wild germplasm accessions and Hevea species revealed that the retroelement is responsible for the generation of new alleles with varying degrees of sequence homology. Segregation analysis of a progeny population confirmed that the alleles are not paralogs and are inherited in a Mendelian mode. Our findings suggest that the first intron of the FDPS gene has been subjected to various chromosomal rearrangements due to the interaction of a retrotransposon, resulting in novel alleles which may substantially contribute towards the evolution of this major gene in rubber. Moreover, the results indicate the possible existence of a retrotransposon-mediated epigenetic gene regulatory mechanism in Hevea.
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Affiliation(s)
- Thomas Kadampanattu Uthup
- Genome Analysis Laboratory, Rubber Research Institute of India, Rubber Board, P O, Kottayam, Kerala Pin-686009, India.
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Piednoël M, Carrete-Vega G, Renner SS. Characterization of the LTR retrotransposon repertoire of a plant clade of six diploid and one tetraploid species. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2013; 75:699-709. [PMID: 23663083 DOI: 10.1111/tpj.12233] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/08/2013] [Accepted: 05/02/2013] [Indexed: 05/10/2023]
Abstract
Comparisons of closely related species are needed to understand the fine-scale dynamics of retrotransposon evolution in flowering plants. Towards this goal, we classified the long terminal repeat (LTR) retrotransposons from six diploid and one tetraploid species of Orobanchaceae. The study species are the autotrophic, non-parasitic Lindenbergia philippensis (as an out-group) and six closely related holoparasitic species of Orobanche [O. crenata, O. cumana, O. gracilis (tetraploid) and O. pancicii] and Phelipanche (P. lavandulacea and P. ramosa). All major plant LTR retrotransposon clades could be identified, and appear to be inherited from a common ancestor. Species of Orobanche, but not Phelipanche, are enriched in Ty3/Gypsy retrotransposons due to a diversification of elements, especially chromoviruses. This is particularly striking in O. gracilis, where tetraploidization seems to have contributed to the Ty3/Gypsy enrichment and led to the emergence of seven large species-specific families of chromoviruses. The preferential insertion of chromoviruses in heterochromatin via their chromodomains might have favored their diversification and enrichment. Our phylogenetic analyses of LTR retrotransposons from Orobanchaceae also revealed that the Bianca clade of Ty1/Copia and the SMART-related elements are much more widely distributed among angiosperms than previously known.
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Affiliation(s)
- Mathieu Piednoël
- Systematic Botany and Mycology, University of Munich (LMU), Munich, 80638, Germany.
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35
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Jiang SY, Ramachandran S. Genome-wide survey and comparative analysis of LTR retrotransposons and their captured genes in rice and sorghum. PLoS One 2013; 8:e71118. [PMID: 23923055 PMCID: PMC3726574 DOI: 10.1371/journal.pone.0071118] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2013] [Accepted: 06/26/2013] [Indexed: 01/09/2023] Open
Abstract
Long terminal repeat (LTR) retrotransposons are the major class I mobile elements in plants. They play crucial roles in gene expansion, diversification and evolution. However, their captured genes are yet to be genome-widely identified and characterized in most of plants although many genomes have been completely sequenced. In this study, we have identified 7,043 and 23,915 full-length LTR retrotransposons in the rice and sorghum genomes, respectively. High percentages of rice full-length LTR retrotransposons were distributed near centromeric region in each of the chromosomes. In contrast, sorghum full-length LTR retrotransposons were not enriched in centromere regions. This dissimilarity could be due to the discrepant retrotransposition during and after divergence from their common ancestor thus might be contributing to species divergence. A total of 672 and 1,343 genes have been captured by these elements in rice and sorghum, respectively. Gene Ontology (GO) and gene set enrichment analysis (GSEA) showed that no over-represented GO term was identified in LTR captured rice genes. For LTR captured sorghum genes, GO terms with functions in DNA/RNA metabolism and chromatin organization were over-represented. Only 36% of LTR captured rice genes were expressed and expression divergence was estimated as 11.9%. Higher percentage of LTR captured rice genes have evolved into pseudogenes under neutral selection. On the contrary, higher percentage of LTR captured sorghum genes were under purifying selection and 72.4% of them were expressed. Thus, higher percentage of LTR captured sorghum genes was functional. Small RNA analysis suggested that some of LTR captured genes in rice and sorghum might have been involved in negative regulation. On the other hand, positive selection has been observed in both rice and sorghum LTR captured genes and some of them were still expressed and functional. The data suggest that some of these LTR captured genes might have evolved into new gene functions.
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Affiliation(s)
- Shu-Ye Jiang
- Temasek Life Sciences Laboratory, National University of Singapore, Singapore
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Yin H, Liu J, Xu Y, Liu X, Zhang S, Ma J, Du J. TARE1, a mutated Copia-like LTR retrotransposon followed by recent massive amplification in tomato. PLoS One 2013; 8:e68587. [PMID: 23861922 PMCID: PMC3701649 DOI: 10.1371/journal.pone.0068587] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2013] [Accepted: 06/05/2013] [Indexed: 11/19/2022] Open
Abstract
Long terminal repeat retrotransposons (LTR-RTs) are the major DNA components in flowering plants. Most LTR-RTs contain dinucleotides ‘TG’ and ‘CA’ at the ends of the two LTRs. Here we report the structure, evolution, and propensity of a tomato atypical retrotransposon element (TARE1) with both LTRs starting as ‘TA’. This family is also characterized by high copy numbers (354 copies), short LTR size (194 bp), extremely low ratio of solo LTRs to intact elements (0.05∶1), recent insertion (most within 0.75∼1.75 million years, Mys), and enrichment in pericentromeric region. The majority (83%) of the TARE1 elements are shared between S. lycopersicum and its wild relative S. pimpinellifolium, but none of them are found in potato. In the present study, we used shared LTR-RTs as molecular markers and estimated the divergence time between S. lycopersicum and S. pimpinellifolium to be <0.5 Mys. Phylogenetic analysis showed that the TARE1 elements, together with two closely related families, TARE2 and TGRE1, have formed a sub-lineage belonging to a Copia-like Ale lineage. Although TARE1 and TARE2 shared similar structural characteristics, the timing, scale, and activity of their amplification were found to be substantially different. We further propose a model wherein a single mutation from ‘G’ to ‘A’ in 3′ LTR followed by amplification is responsible for the origin of TARE1, thus providing evidence that the proliferation of a spontaneous mutation can be mediated by the amplification of LTR-RTs at the level of RNA.
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Affiliation(s)
- Hao Yin
- Bioinformatics Group, Institute of Industrial Crops, Jiangsu Academy of Agricultural Sciences, Nanjing, China
- Center of Pear Engineering Technology Research, State Key Laboratory of Crop Genetics and Germplasm Enhancement, Nanjing Agricultural University, Nanjing, China
| | - Jing Liu
- Bioinformatics Group, Institute of Industrial Crops, Jiangsu Academy of Agricultural Sciences, Nanjing, China
| | - Yingxiu Xu
- Bioinformatics Group, Institute of Industrial Crops, Jiangsu Academy of Agricultural Sciences, Nanjing, China
| | - Xing Liu
- Bioinformatics Group, Institute of Industrial Crops, Jiangsu Academy of Agricultural Sciences, Nanjing, China
- Center of Pear Engineering Technology Research, State Key Laboratory of Crop Genetics and Germplasm Enhancement, Nanjing Agricultural University, Nanjing, China
| | - Shaoling Zhang
- Center of Pear Engineering Technology Research, State Key Laboratory of Crop Genetics and Germplasm Enhancement, Nanjing Agricultural University, Nanjing, China
| | - Jianxin Ma
- Department of Agronomy, Purdue University, West Lafayette, Indiana, United States of America
| | - Jianchang Du
- Bioinformatics Group, Institute of Industrial Crops, Jiangsu Academy of Agricultural Sciences, Nanjing, China
- * E-mail:
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Ragupathy R, You FM, Cloutier S. Arguments for standardizing transposable element annotation in plant genomes. TRENDS IN PLANT SCIENCE 2013; 18:367-76. [PMID: 23618952 DOI: 10.1016/j.tplants.2013.03.005] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/14/2012] [Revised: 03/07/2013] [Accepted: 03/26/2013] [Indexed: 05/26/2023]
Abstract
Whole genome sequence assemblies have been generated for many plants. Annotation of transposable elements (TEs), which constitute the major proportion of genomes and play a significant role in epigenome alterations under stress, has not been given equal importance to that of genes. In this opinion article, we argue that the lack of focus dedicated to the fine-scale characterization of repeat fractions and the absence of consistent methods for their annotation impede our ability to critically understand the influence of TEs on the epigenome with implications in gene expression and non-Mendelian inheritance. Major structural changes occur over an evolutionary time scale. However, epigenetic regulation mediated by TEs can happen in a single generation, thus emphasizing the need for their standardized annotation.
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Affiliation(s)
- Raja Ragupathy
- Cereal Research Centre, Agriculture and Agri-Food Canada, 195 Dafoe Road, Winnipeg, Manitoba, R3T 2M9, Canada
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Co-evolution of plant LTR-retrotransposons and their host genomes. Protein Cell 2013; 4:493-501. [PMID: 23794032 DOI: 10.1007/s13238-013-3037-6] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2013] [Accepted: 05/22/2013] [Indexed: 01/09/2023] Open
Abstract
Transposable elements (TEs), particularly, long terminal repeat retrotransposons (LTR-RTs), are the most abundant DNA components in all plant species that have been investigated, and are largely responsible for plant genome size variation. Although plant genomes have experienced periodic proliferation and/or recent burst of LTR-retrotransposons, the majority of LTR-RTs are inactivated by DNA methylation and small RNA-mediated silencing mechanisms, and/or were deleted/truncated by unequal homologous recombination and illegitimate recombination, as suppression mechanisms that counteract genome expansion caused by LTR-RT amplification. LTR-RT DNA is generally enriched in pericentromeric regions of the host genomes, which appears to be the outcomes of preferential insertions of LTR-RTs in these regions and low effectiveness of selection that purges LTR-RT DNA from these regions relative to chromosomal arms. Potential functions of various TEs in their host genomes remain blurry; nevertheless, LTR-RTs have been recognized to play important roles in maintaining chromatin structures and centromere functions and regulation of gene expressions in their host genomes.
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Zhou Y, Cahan SH. A novel family of terminal-repeat retrotransposon in miniature (TRIM) in the genome of the red harvester ant, Pogonomyrmex barbatus. PLoS One 2012; 7:e53401. [PMID: 23285291 PMCID: PMC3532108 DOI: 10.1371/journal.pone.0053401] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2012] [Accepted: 11/29/2012] [Indexed: 12/03/2022] Open
Abstract
We report the first described non-plant family of TRIMs (terminal-repeat retrotransposons in miniature), which are small nonautonomous LTR retrotransposons, from the whole-genome sequence of the red harvester ant, Pogonomyrmex barbatus (Hymenoptera: Myrmicinae). Members of this retrotransposon family, named PbTRIM, have typical features of plant TRIMs in length and structure, although they share no overall sequence similarity. PbTRIM elements and their solo-LTRs are abundant in the host genome and exhibit an uneven distribution pattern. Elements are preferentially inserted into TA-rich regions with ATAT as the most common pattern of target site duplication (TSD). PbTRIM is most likely mobile as indicated by the young age of many complete elements, the high degree of sequence similarity among elements at different genomic locations, the abundance of elements in the host genome, and the presence of 4-bp target site duplications (TSDs) flanking the elements and solo-LTRs. Many PbTRIM elements and their solo-LTRs are located within or near genes, suggesting their potential roles in restructuring the host genes and genome. Database search, PCR and sequencing analysis revealed the presence of homologous PbTRIM elements in other ant species. The high sequence similarity between elements from distantly related ant species, the incongruence between the phylogenies of PbTRIM and its hosts, and the patchy distribution of the retroelement within the Myrmicinae subfamily indicate possible horizontal transfer events of the retroelement.
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Affiliation(s)
- Yihong Zhou
- Department of Biology, University of Vermont, Burlington, Vermont, United States of America
| | - Sara Helms Cahan
- Department of Biology, University of Vermont, Burlington, Vermont, United States of America
- * E-mail:
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[Identification and analysis methods of plant LTR retrotransposon sequences]. YI CHUAN = HEREDITAS 2012. [PMID: 23208147 DOI: 10.3724/sp.j.1005.2012.01491] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
LTR retrotransposons are an important class of eukaryotic transposable elements, which are ubiquitous and highly heterogeneous in plant and play a major role in genome evolution of eukaryote. They are now extensively employed in gene function and genetic diversity analyses. Identification of LTR retrotransposons is the precondition for its application. Therefore, it has important theoretical significance and practical application value in studying identification and analysis methods LTR retrotransposon sequences. Bioinformatic software of the sequence analysis, according to the work principle, can be classified roughly into two types: sequence alignment and sequence identification of conserved domains. Alignment software, such as BLAST and DNAstar, produce the corresponding sequence information through comparison of sequence similarity; however, this kind of software cannot be applied for full length sequences. According to the principle, LTR retro-transposon sequence identification software can be roughly sorted into four types: de novo repeat discovery method, com-parative genomic method, homology-based method, and structure-based method. For example, LTR_Finder based on de novo repeat discovery method can accurately predict and annotate LTR retrotransposons for full length sequences; Repeat-Masker, which is based on homology-based method, can discover LTR retrotransposons by comparing the similarity with known sequences in the database. In this article, different methods of identification and analysis of retrotransposon se-quences were compared and analyzed, and a set of flow of LTR retrotransposons sequence analysis was summarized in order to provide the reference for LTR retrotransposons sequence analysis.
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Gao D, Jimenez-Lopez JC, Iwata A, Gill N, Jackson SA. Functional and structural divergence of an unusual LTR retrotransposon family in plants. PLoS One 2012; 7:e48595. [PMID: 23119066 PMCID: PMC3485330 DOI: 10.1371/journal.pone.0048595] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2012] [Accepted: 09/28/2012] [Indexed: 12/24/2022] Open
Abstract
Retrotransposons with long terminal repeats (LTRs) more than 3 kb are not frequent in most eukaryotic genomes. Rice LTR retrotransposon, Retrosat2, has LTRs greater than 3.2 kb and two open reading frames (ORF): ORF1 encodes enzymes for retrotransposition whereas no function can be assigned to ORF0 as it is not found in any other organism. A variety of experimental and in silico approaches were used to determine the origin of Retrosat2 and putative function of ORF0. Our data show that not only is Retrosat2 highly abundant in the Oryza genus, it may yet be active in rice. Homologs of Retrosat2 were identified in maize, sorghum, Arabidopsis and other plant genomes suggesting that the Retrosat2 family is of ancient origin. Several putatively cis-acting elements, some multicopy, that regulate retrotransposon replication or responsiveness to environmental factors were found in the LTRs of Retrosat2. Unlike the ORF1, the ORF0 sequences from Retrosat2 and homologs are divergent at the sequence level, 3D-structures and predicted biological functions. In contrast to other retrotransposon families, Retrosat2 and its homologs are dispersed throughout genomes and not concentrated in the specific chromosomal regions, such as centromeres. The genomic distribution of Retrosat2 homologs varies across species which likely reflects the differing evolutionary trajectories of this retrotransposon family across diverse species.
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Affiliation(s)
- Dongying Gao
- Center for Applied Genetic Technologies, University of Georgia, Athens, Georgia, United States of America
| | - Jose C. Jimenez-Lopez
- Department of Biochemistry, Cell & Molecular Biology of Plants, Estacion Experimental del Zaidin, High Council for Scientific Research, Granada, Spain
| | - Aiko Iwata
- Center for Applied Genetic Technologies, University of Georgia, Athens, Georgia, United States of America
| | - Navdeep Gill
- Center for Applied Genetic Technologies, University of Georgia, Athens, Georgia, United States of America
- Department of Botany, University of British Columbia, Vancouver, British Columbia, Canada
| | - Scott A. Jackson
- Center for Applied Genetic Technologies, University of Georgia, Athens, Georgia, United States of America
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