1
|
Martin GT, Solares E, Guadardo-Mendez J, Muyle A, Bousios A, Gaut BS. miRNA-like secondary structures in maize ( Zea mays) genes and transposable elements correlate with small RNAs, methylation, and expression. Genome Res 2023; 33:1932-1946. [PMID: 37918960 PMCID: PMC10760457 DOI: 10.1101/gr.277459.122] [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: 11/07/2022] [Accepted: 10/16/2023] [Indexed: 11/04/2023]
Abstract
RNA molecules carry information in their primary sequence and also their secondary structure. Secondary structure can confer important functional information, but it is also a signal for an RNAi-like host epigenetic response mediated by small RNAs (smRNAs). In this study, we used two bioinformatic methods to predict local secondary structures across features of the maize genome, focusing on small regions that had similar folding properties to pre-miRNA loci. We found miRNA-like secondary structures to be common in genes and most, but not all, superfamilies of RNA and DNA transposable elements (TEs). The miRNA-like regions map to a higher diversity of smRNAs than regions without miRNA-like structure, explaining up to 27% of variation in smRNA mapping for some TE superfamilies. This mapping bias is more pronounced among putatively autonomous TEs relative to nonautonomous TEs. Genome-wide, miRNA-like regions are also associated with elevated methylation levels, particularly in the CHH context. Among genes, those with miRNA-like secondary structure are 1.5-fold more highly expressed, on average, than other genes. However, these genes are also more variably expressed across the 26 nested association mapping founder lines, and this variability positively correlates with the number of mapping smRNAs. We conclude that local miRNA-like structures are a nearly ubiquitous feature of expressed regions of the maize genome, that they correlate with higher smRNA mapping and methylation, and that they may represent a trade-off between functional requirements and the potentially negative consequences of smRNA production.
Collapse
Affiliation(s)
- Galen T Martin
- Department of Ecology and Evolutionary Biology, University of California, Irvine, California 92617, USA
| | - Edwin Solares
- Department of Ecology and Evolutionary Biology, University of California, Irvine, California 92617, USA
- Department of Ecology and Evolutionary Biology, University of California, Davis, California 95616, USA
| | - Jeanelle Guadardo-Mendez
- Department of Ecology and Evolutionary Biology, University of California, Irvine, California 92617, USA
| | - Aline Muyle
- Department of Ecology and Evolutionary Biology, University of California, Irvine, California 92617, USA
- CEFE, University of Montpellier, CNRS, EPHE, IRD, 34090 Montpellier, France
| | - Alexandros Bousios
- School of Life Sciences, University of Sussex, Brighton BN1 9QG, United Kingdom
| | - Brandon S Gaut
- Department of Ecology and Evolutionary Biology, University of California, Irvine, California 92617, USA;
| |
Collapse
|
2
|
Sammarco I, Pieters J, Salony S, Toman I, Zolotarov G, Lafon Placette C. Epigenetic targeting of transposon relics: beating the dead horses of the genome? Epigenetics 2022; 17:1331-1344. [PMID: 36255200 PMCID: PMC9586680 DOI: 10.1080/15592294.2021.2022066] [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: 01/07/2023] Open
Abstract
Transposable elements (TEs) have been seen as selfish genetic elements that can propagate in a host genome. Their propagation success is however hindered by a combination of mechanisms such as mutations, selection, and their epigenetic silencing by the host genome. As a result, most copies of TEs in a given genome are dead relics: their sequence is too degenerated to allow any transposition. Nevertheless, these TE relics often, but not always, remain epigenetically silenced, and if not to prevent transposition anymore, one can wonder the reason for this phenomenon. The mere self-perpetuating loop inherent to epigenetic silencing could alone explain that even when inactive, TE copies remain silenced. Beyond this process, nevertheless, antagonistic selective forces are likely to act on TE relic silencing. Especially, without the benefit of preventing transposition, TE relic silencing may prove deleterious to the host fitness, suggesting that the maintenance of TE relic silencing is the result of a fine, and perhaps case-by-case, evolutionary trade-off between beneficial and deleterious effects. Ultimately, the release of TE relics silencing may provide a 'safe' ground for adaptive epimutations to arise. In this review, we provide an overview of these questions in both plants and animals.
Collapse
Affiliation(s)
- Iris Sammarco
- Department of Botany, Faculty of Science, Charles University, Prague, Czech Republic,Institute of Botany, Czech Academy of Sciences, Pruhonice, Czech Republic
| | - Janto Pieters
- Laboratory of Pollen Biology, Institute of Experimental Botany, Czech Academy of Science, Prague, Czech Republic,Department of Plant Experimental Biology, Faculty of Science, Charles University, Prague, Czech Republic
| | - Susnata Salony
- Department of Botany, Faculty of Science, Charles University, Prague, Czech Republic
| | - Izabela Toman
- Department of Anthropology and Human Genetics, Faculty of Science, Charles University, Prague, Czech Republic
| | - Grygoriy Zolotarov
- Berlin Institute for Medical Systems Biology, Max Delbrück Center for Molecular Medicine in the Helmholtz Association, Berlin, Germany
| | - Clément Lafon Placette
- Department of Botany, Faculty of Science, Charles University, Prague, Czech Republic,CONTACT Clément Lafon Placette Department of Botany, Faculty of Science, Charles University, PragueCZ-128 01, Czech Republic
| |
Collapse
|
3
|
Yin L, Xu G, Yang J, Zhao M. The Heterogeneity in the Landscape of Gene Dominance in Maize is Accompanied by Unique Chromatin Environments. Mol Biol Evol 2022; 39:6709529. [PMID: 36130304 PMCID: PMC9547528 DOI: 10.1093/molbev/msac198] [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] [Indexed: 12/15/2022] Open
Abstract
Subgenome dominance after whole-genome duplication (WGD) has been observed in many plant species. However, the degree to which the chromatin environment affects this bias has not been explored. Here, we compared the dominant subgenome (maize1) and the recessive subgenome (maize2) with respect to patterns of sequence substitutions, genes expression, transposable element accumulation, small interfering RNAs, DNA methylation, histone modifications, and accessible chromatin regions (ACRs). Our data show that the degree of bias between subgenomes for all the measured variables does not vary significantly when both of the WGD genes are located in pericentromeric regions. Our data further indicate that the location of maize1 genes in chromosomal arms is pivotal for maize1 to maintain its dominance, but location has a less effect on maize2 homoeologs. In addition to homoeologous genes, we compared ACRs, which often harbor cis-regulatory elements, between the two subgenomes and demonstrate that maize1 ACRs have a higher level of chromatin accessibility, a lower level of sequence substitution, and are enriched in chromosomal arms. Furthermore, we find that a loss of maize1 ACRs near their nearby genes is associated with a reduction in purifying selection and expression of maize1 genes relative to their maize2 homoeologs. Taken together, our data suggest that chromatin environment and cis-regulatory elements are important determinants shaping the divergence and evolution of duplicated genes.
Collapse
Affiliation(s)
- Liangwei Yin
- Department of Biology, Miami University, Oxford, OH 45056
| | - Gen Xu
- Department of Agronomy and Horticulture, University of Nebraska-Lincoln, Lincoln, NE 68588,Center for Plant Science Innovation, University of Nebraska-Lincoln, Lincoln, NE 68583
| | - Jinliang Yang
- Department of Agronomy and Horticulture, University of Nebraska-Lincoln, Lincoln, NE 68588,Center for Plant Science Innovation, University of Nebraska-Lincoln, Lincoln, NE 68583
| | | |
Collapse
|
4
|
Zhao Y, Li X, Xie J, Xu W, Chen S, Zhang X, Liu S, Wu J, El-Kassaby YA, Zhang D. Transposable Elements: Distribution, Polymorphism, and Climate Adaptation in Populus. FRONTIERS IN PLANT SCIENCE 2022; 13:814718. [PMID: 35178060 PMCID: PMC8843856 DOI: 10.3389/fpls.2022.814718] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/14/2021] [Accepted: 01/10/2022] [Indexed: 06/14/2023]
Abstract
Transposable elements (TEs) are a class of mobile genetic elements that make effects on shaping rapid phenotypic traits of adaptive significance. TE insertions are usually related to transcription changes of nearby genes, and thus may be subjected to purifying selection. Based on the available genome resources of Populus, we found that the composition of Helitron DNA family were highly variable and could directly influence the transcription of nearby gene expression, which are involving in stress-responsive, programmed cell death, and apoptosis pathway. Next, we indicated TEs are highly enriched in Populus trichocarpa compared with three other congeneric poplar species, especially located at untranslated regions (3'UTRs and 5'UTRs) and Helitron transposons, particularly 24-nt siRNA-targeted, are significantly associated with reduced gene expression. Additionally, we scanned a representative resequenced Populus tomentosa population, and identified 9,680 polymorphic TEs loci. More importantly, we identified a Helitron transposon located at the 3'UTR, which could reduce WRKY18 expression level. Our results highlight the importance of TE insertion events, which could regulate gene expression and drive adaptive phenotypic variation in Populus.
Collapse
Affiliation(s)
- Yiyang Zhao
- National Engineering Laboratory for Tree Breeding, College of Biological Sciences and Technology, Beijing Forestry University, Beijing, China
- Key Laboratory of Genetics and Breeding in Forest Trees and Ornamental Plants, Ministry of Education, College of Biological Sciences and Technology, Beijing Forestry University, Beijing, China
| | - Xian Li
- National Engineering Laboratory for Tree Breeding, College of Biological Sciences and Technology, Beijing Forestry University, Beijing, China
- Key Laboratory of Genetics and Breeding in Forest Trees and Ornamental Plants, Ministry of Education, College of Biological Sciences and Technology, Beijing Forestry University, Beijing, China
| | - Jianbo Xie
- National Engineering Laboratory for Tree Breeding, College of Biological Sciences and Technology, Beijing Forestry University, Beijing, China
- Key Laboratory of Genetics and Breeding in Forest Trees and Ornamental Plants, Ministry of Education, College of Biological Sciences and Technology, Beijing Forestry University, Beijing, China
| | - Weijie Xu
- National Engineering Laboratory for Tree Breeding, College of Biological Sciences and Technology, Beijing Forestry University, Beijing, China
- Key Laboratory of Genetics and Breeding in Forest Trees and Ornamental Plants, Ministry of Education, College of Biological Sciences and Technology, Beijing Forestry University, Beijing, China
| | - Sisi Chen
- National Engineering Laboratory for Tree Breeding, College of Biological Sciences and Technology, Beijing Forestry University, Beijing, China
- Key Laboratory of Genetics and Breeding in Forest Trees and Ornamental Plants, Ministry of Education, College of Biological Sciences and Technology, Beijing Forestry University, Beijing, China
| | - Xiang Zhang
- National Engineering Laboratory for Tree Breeding, College of Biological Sciences and Technology, Beijing Forestry University, Beijing, China
- Key Laboratory of Genetics and Breeding in Forest Trees and Ornamental Plants, Ministry of Education, College of Biological Sciences and Technology, Beijing Forestry University, Beijing, China
| | - Sijia Liu
- National Engineering Laboratory for Tree Breeding, College of Biological Sciences and Technology, Beijing Forestry University, Beijing, China
- Key Laboratory of Genetics and Breeding in Forest Trees and Ornamental Plants, Ministry of Education, College of Biological Sciences and Technology, Beijing Forestry University, Beijing, China
| | - Jiadong Wu
- National Engineering Laboratory for Tree Breeding, College of Biological Sciences and Technology, Beijing Forestry University, Beijing, China
- Key Laboratory of Genetics and Breeding in Forest Trees and Ornamental Plants, Ministry of Education, College of Biological Sciences and Technology, Beijing Forestry University, Beijing, China
| | - Yousry A. El-Kassaby
- Department of Forest and Conservation Sciences, Forest Sciences Centre, Faculty of Forestry, The University of British Columbia, Vancouver, BC, Canada
| | - Deqiang Zhang
- National Engineering Laboratory for Tree Breeding, College of Biological Sciences and Technology, Beijing Forestry University, Beijing, China
- Key Laboratory of Genetics and Breeding in Forest Trees and Ornamental Plants, Ministry of Education, College of Biological Sciences and Technology, Beijing Forestry University, Beijing, China
| |
Collapse
|
5
|
Dallaire A, Manley BF, Wilkens M, Bista I, Quan C, Evangelisti E, Bradshaw CR, Ramakrishna NB, Schornack S, Butter F, Paszkowski U, Miska EA. Transcriptional activity and epigenetic regulation of transposable elements in the symbiotic fungus Rhizophagus irregularis. Genome Res 2021; 31:2290-2302. [PMID: 34772700 PMCID: PMC8647823 DOI: 10.1101/gr.275752.121] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2021] [Accepted: 09/16/2021] [Indexed: 11/29/2022]
Abstract
Arbuscular mycorrhizal (AM) fungi form mutualistic relationships with most land plant species. AM fungi have long been considered as ancient asexuals. Long-term clonal evolution would be remarkable for a eukaryotic lineage and suggests the importance of alternative mechanisms to promote genetic variability facilitating adaptation. Here, we assessed the potential of transposable elements for generating such genomic diversity. The dynamic expression of TEs during Rhizophagus irregularis spore development suggests ongoing TE activity. We find Mutator-like elements located near genes belonging to highly expanded gene families. Whole-genome epigenomic profiling of R. irregularis provides direct evidence of DNA methylation and small RNA production occurring at TE loci. Our results support a model in which TE activity shapes the genome, while DNA methylation and small RNA-mediated silencing keep their overproliferation in check. We propose that a well-controlled TE activity directly contributes to genome evolution in AM fungi.
Collapse
Affiliation(s)
- Alexandra Dallaire
- Wellcome Trust/Cancer Research UK Gurdon Institute, University of Cambridge, Cambridge CB2 1QN, United Kingdom
- Department of Genetics, University of Cambridge, Cambridge CB2 3EH, United Kingdom
- Tree of Life, Wellcome Sanger Institute, Cambridge CB10 1SA, United Kingdom
| | - Bethan F Manley
- Wellcome Trust/Cancer Research UK Gurdon Institute, University of Cambridge, Cambridge CB2 1QN, United Kingdom
- Department of Genetics, University of Cambridge, Cambridge CB2 3EH, United Kingdom
- Tree of Life, Wellcome Sanger Institute, Cambridge CB10 1SA, United Kingdom
| | - Maya Wilkens
- Quantitative Proteomics, Institute of Molecular Biology, 55128 Mainz, Germany
| | - Iliana Bista
- Wellcome Trust/Cancer Research UK Gurdon Institute, University of Cambridge, Cambridge CB2 1QN, United Kingdom
- Department of Genetics, University of Cambridge, Cambridge CB2 3EH, United Kingdom
- Tree of Life, Wellcome Sanger Institute, Cambridge CB10 1SA, United Kingdom
| | - Clement Quan
- Sainsbury Laboratory, University of Cambridge, Cambridge CB2 1LR, United Kingdom
| | - Edouard Evangelisti
- Sainsbury Laboratory, University of Cambridge, Cambridge CB2 1LR, United Kingdom
| | - Charles R Bradshaw
- Wellcome Trust/Cancer Research UK Gurdon Institute, University of Cambridge, Cambridge CB2 1QN, United Kingdom
| | - Navin B Ramakrishna
- Wellcome Trust/Cancer Research UK Gurdon Institute, University of Cambridge, Cambridge CB2 1QN, United Kingdom
- Department of Genetics, University of Cambridge, Cambridge CB2 3EH, United Kingdom
| | - Sebastian Schornack
- Sainsbury Laboratory, University of Cambridge, Cambridge CB2 1LR, United Kingdom
| | - Falk Butter
- Quantitative Proteomics, Institute of Molecular Biology, 55128 Mainz, Germany
| | - Uta Paszkowski
- Crop Science Centre, University of Cambridge, Cambridge CB3 0LE, United Kingdom
| | - Eric A Miska
- Wellcome Trust/Cancer Research UK Gurdon Institute, University of Cambridge, Cambridge CB2 1QN, United Kingdom
- Department of Genetics, University of Cambridge, Cambridge CB2 3EH, United Kingdom
- Tree of Life, Wellcome Sanger Institute, Cambridge CB10 1SA, United Kingdom
| |
Collapse
|
6
|
Minow MAA, Lukens L, Rossi V, Colasanti J. Patterns of stability and change in the maize genome: a case study of small RNA transcriptomes in two recombinant inbred lines and their progenitors. Genome 2021; 65:1-12. [PMID: 34597524 DOI: 10.1139/gen-2021-0040] [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: 11/22/2022]
Abstract
Small RNAs (sRNAs) are epigenetic regulators of eukaryotic genes and transposable elements (TEs). Diverse sRNA expression patterns exist within a species, but how this diversity arises is not well understood. To provide a window into the dynamics of maize sRNA patterning, sRNA and mRNA transcriptomes were examined in two related Zea mays recombinant inbred lines (RILs) and their inbred parents. Analysis of these RILs revealed that most clusters of sRNA expression retained the parental sRNA expression level. However, expression states that differ from the parental allele were also observed, predominantly reflecting decreases in sRNA expression. When RIL sRNA expression differed from the parental allele, the new state was frequently similar between the two RILs, and similar to the expression state found at the allele in the other parent. Novel sRNA expression patterns, distinct from those of either parent, were rare. Additionally, examination of sRNA expression over TEs revealed one TE family, Gyma, which showed consistent enrichment for RIL sRNA expression differences compared to those found in parental alleles. These findings provide insights into how sRNA silencing might evolve over generations and suggest that further investigation into the molecular nature of sRNA trans regulators is warranted.
Collapse
Affiliation(s)
- Mark A A Minow
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario, Canada
| | - Lewis Lukens
- Plant Agriculture Department, University of Guelph, Guelph, Ontario, Canada
| | - Vincenzo Rossi
- Council for Agricultural Research and Economics, Research Centre for Cereal and Industrial Crops, I-24126 Bergamo, Italy
| | - Joseph Colasanti
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario, Canada
| |
Collapse
|
7
|
Muyle A, Seymour D, Darzentas N, Primetis E, Gaut BS, Bousios A. Gene capture by transposable elements leads to epigenetic conflict in maize. MOLECULAR PLANT 2021; 14:237-252. [PMID: 33171302 DOI: 10.1016/j.molp.2020.11.003] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/06/2020] [Revised: 10/15/2020] [Accepted: 11/05/2020] [Indexed: 06/11/2023]
Abstract
Transposable elements (TEs) regularly capture fragments of genes. When the host silences these TEs, siRNAs homologous to the captured regions may also target the genes. This epigenetic crosstalk establishes an intragenomic conflict: silencing the TEs has the cost of silencing the genes. If genes are important, however, natural selection may maintain function by moderating the silencing response, which may also advantage the TEs. In this study, we examined this model by focusing on Helitrons, Pack-MULEs, and Sirevirus LTR retrotransposons in the maize genome. We documented 1263 TEs containing exon fragments from 1629 donor genes. Consistent with epigenetic conflict, donor genes mapped more siRNAs and were more methylated than genes with no evidence of capture. However, these patterns differed between syntelog versus translocated donor genes. Syntelogs appeared to maintain function, as measured by gene expression, consistent with moderation of silencing for functionally important genes. Epigenetic marks did not spread beyond their captured regions and 24nt crosstalk siRNAs were linked with CHH methylation. Translocated genes, in contrast, bore the signature of silencing. They were highly methylated and less expressed, but also overrepresented among donor genes and located away from chromosomal arms, which suggests a link between capture and gene movement. Splitting genes into potential functional categories based on evolutionary constraint supported the synteny-based findings. TE families captured genes in different ways, but the evidence for their advantage was generally less obvious; nevertheless, TEs with captured fragments were older, mapped fewer siRNAs, and were slightly less methylated than TEs without captured fragments. Collectively, our results argue that TE capture triggers an intragenomic conflict that may not affect the function of important genes but may lead to the pseudogenization of less-constrained genes.
Collapse
Affiliation(s)
- Aline Muyle
- Department of Ecology and Evolutionary Biology, UC Irvine, Irvine, CA 92697, USA
| | - Danelle Seymour
- Department of Ecology and Evolutionary Biology, UC Irvine, Irvine, CA 92697, USA; Department of Botany and Plant Sciences, UC Riverside, Riverside, CA 92521, USA
| | - Nikos Darzentas
- Central European Institute of Technology, Masaryk University, Brno, Czech Republic
| | - Elias Primetis
- School of Life Sciences, University of Sussex, Brighton, UK
| | - Brandon S Gaut
- Department of Ecology and Evolutionary Biology, UC Irvine, Irvine, CA 92697, USA.
| | | |
Collapse
|
8
|
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.
Collapse
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
| |
Collapse
|
9
|
Wang Y, Liang W, Tang T. Constant conflict between Gypsy LTR retrotransposons and CHH methylation within a stress-adapted mangrove genome. THE NEW PHYTOLOGIST 2018; 220:922-935. [PMID: 29762876 DOI: 10.1111/nph.15209] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/09/2018] [Accepted: 04/10/2018] [Indexed: 05/23/2023]
Abstract
The evolutionary dynamics of the conflict between transposable elements (TEs) and their host genome remain elusive. This conflict will be intense in stress-adapted plants as stress can often reactivate TEs. Mangroves reduce TE load convergently in their adaptation to intertidal environments and thus provide a unique opportunity to address the host-TE conflict and its interaction with stress adaptation. Using the mangrove Rhizophora apiculata as a model, we investigated methylation and short interfering RNA (siRNA) targeting patterns in relation to the abundance and age of long terminal repeat (LTR) retrotransposons. We also examined the distance of LTR retrotransposons to genes, the impact on neighboring gene expression and population frequencies. We found differential accumulation amongst classes of LTR retrotransposons despite high overall methylation levels. This can be attributed to 24-nucleotide siRNA-mediated CHH methylation preferentially targeting Gypsy elements, particularly in their LTR regions. Old Gypsy elements possess unusually abundant siRNAs which show cross-mapping to young copies. Gypsy elements appear to be closer to genes and under stronger purifying selection than other classes. Our results suggest a continuous host-TE battle masked by the TE load reduction in R. apiculata. This conflict may enable mangroves, such as R. apiculata, to maintain genetic diversity and thus evolutionary potential during stress adaptation.
Collapse
Affiliation(s)
- Yushuai Wang
- State Key Laboratory of Biocontrol and Guangdong Key Laboratory of Plant Resources, School of Life Sciences, Sun Yat-sen University, Guangzhou, 510275, Guangdong, China
| | - Weiqi Liang
- State Key Laboratory of Biocontrol and Guangdong Key Laboratory of Plant Resources, School of Life Sciences, Sun Yat-sen University, Guangzhou, 510275, Guangdong, China
| | - Tian Tang
- State Key Laboratory of Biocontrol and Guangdong Key Laboratory of Plant Resources, School of Life Sciences, Sun Yat-sen University, Guangzhou, 510275, Guangdong, China
| |
Collapse
|
10
|
Roessler K, Bousios A, Meca E, Gaut BS. Modeling Interactions between Transposable Elements and the Plant Epigenetic Response: A Surprising Reliance on Element Retention. Genome Biol Evol 2018; 10:803-815. [PMID: 29608716 PMCID: PMC5841382 DOI: 10.1093/gbe/evy043] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/20/2018] [Indexed: 12/16/2022] Open
Abstract
Transposable elements (TEs) compose the majority of angiosperm DNA. Plants counteract TE activity by silencing them epigenetically. One form of epigenetic silencing requires 21-22 nt small interfering RNAs that act to degrade TE mRNA and may also trigger DNA methylation. DNA methylation is reinforced by a second mechanism, the RNA-dependent DNA methylation (RdDM) pathway. RdDM relies on 24 nt small interfering RNAs and ultimately establishes TEs in a quiescent state. These host factors interact at a systems level, but there have been no system level analyses of their interactions. Here, we define a deterministic model that represents the propagation of active TEs, aspects of the host response and the accumulation of silenced TEs. We describe general properties of the model and also fit it to biological data in order to explore two questions. The first is why two overlapping pathways are maintained, given that both are likely energetically expensive. Under our model, RdDM silenced TEs effectively even when the initiation of silencing was weak. This relationship implies that only a small amount of RNAi is needed to initiate TE silencing, but reinforcement by RdDM is necessary to efficiently counter TE propagation. Second, we investigated the reliance of the host response on rates of TE deletion. The model predicted that low levels of deletion lead to few active TEs, suggesting that silencing is most efficient when methylated TEs are retained in the genome, thereby providing one explanation for the large size of plant genomes.
Collapse
Affiliation(s)
- Kyria Roessler
- Department of Ecology and Evolutionary Biology, UC Irvine
| | | | - Esteban Meca
- Departamento de Agronomia, Universidad de Cordoba, Spain
| | - Brandon S Gaut
- Department of Ecology and Evolutionary Biology, UC Irvine
| |
Collapse
|
11
|
Li ZW, Hou XH, Chen JF, Xu YC, Wu Q, González J, Guo YL. Transposable Elements Contribute to the Adaptation of Arabidopsis thaliana. Genome Biol Evol 2018; 10:2140-2150. [PMID: 30102348 PMCID: PMC6117151 DOI: 10.1093/gbe/evy171] [Citation(s) in RCA: 43] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/08/2018] [Indexed: 12/30/2022] Open
Abstract
Transposable elements (TEs) are mobile genetic elements with very high mutation rates that play important roles in shaping genome architecture and regulating phenotypic variation. However, the extent to which TEs influence the adaptation of organisms in their natural habitats is largely unknown. Here, we scanned 201 representative resequenced genomes from the model plant Arabidopsis thaliana and identified 2,311 polymorphic TEs from noncentromeric regions. We found expansion and contraction of different types of TEs in different A. thaliana populations. More importantly, we identified two TE insertions that are likely candidates to play a role in adaptive evolution. Our results highlight the importance of variations in TEs for the adaptation of plants in general in the context of rapid global climate change.
Collapse
Affiliation(s)
- Zi-Wen Li
- State Key Laboratory of Systematic and Evolutionary Botany, Institute of Botany, Chinese Academy of Sciences, Beijing, China
| | - Xing-Hui Hou
- State Key Laboratory of Systematic and Evolutionary Botany, Institute of Botany, Chinese Academy of Sciences, Beijing, China
- College of Life Sciences, University of Chinese Academy of Sciences, Beijing, China
| | - Jia-Fu Chen
- State Key Laboratory of Systematic and Evolutionary Botany, Institute of Botany, Chinese Academy of Sciences, Beijing, China
- College of Life Sciences, University of Chinese Academy of Sciences, Beijing, China
| | - Yong-Chao Xu
- State Key Laboratory of Systematic and Evolutionary Botany, Institute of Botany, Chinese Academy of Sciences, Beijing, China
- College of Life Sciences, University of Chinese Academy of Sciences, Beijing, China
| | - Qiong Wu
- State Key Laboratory of Systematic and Evolutionary Botany, Institute of Botany, Chinese Academy of Sciences, Beijing, China
| | - Josefa González
- Institute of Evolutionary Biology (CSIC-Universitat Pompeu Fabra), Barcelona, Spain
| | - Ya-Long Guo
- State Key Laboratory of Systematic and Evolutionary Botany, Institute of Botany, Chinese Academy of Sciences, Beijing, China
- College of Life Sciences, University of Chinese Academy of Sciences, Beijing, China
| |
Collapse
|
12
|
Zhao M, Zhang B, Lisch D, Ma J. Patterns and Consequences of Subgenome Differentiation Provide Insights into the Nature of Paleopolyploidy in Plants. THE PLANT CELL 2017; 29:2974-2994. [PMID: 29180596 PMCID: PMC5757279 DOI: 10.1105/tpc.17.00595] [Citation(s) in RCA: 64] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/27/2017] [Revised: 10/26/2017] [Accepted: 11/16/2017] [Indexed: 05/07/2023]
Abstract
Polyploidy is an important feature of plant genomes, but the nature of many polyploidization events remains to be elucidated. Here, we demonstrate that the evolutionary fates of the subgenomes in maize (Zea mays) and soybean (Glycine max) have followed different trajectories. One subgenome has been subject to relaxed selection, lower levels of gene expression, higher rates of transposable element accumulation, more small interfering RNAs and DNA methylation around genes, and higher rates of gene loss in maize, whereas none of these features were observed in soybean. Nevertheless, individual gene pairs exhibit differentiation with respect to these features in both species. In addition, we observed a higher number of chromosomal rearrangements and higher frequency of retention of duplicated genes in soybean than in maize. Furthermore, soybean "singletons" were found to be more frequently tandemly duplicated than "duplicates" in soybean, which may, to some extent, counteract the genome imbalance caused by gene loss. We propose that unlike in maize, in which two subgenomes were distinct prior to the allotetraploidization event and thus experienced global differences in selective constraints, in soybean, the two subgenomes were far less distinct prior to polyploidization, such that individual gene pairs, rather than subgenomes, experienced stochastic differences over longer periods of time, resulting in retention of the majority of duplicates.
Collapse
Affiliation(s)
- Meixia Zhao
- Department of Botany and Plant Pathology, Purdue University, West Lafayette, Indiana 47907
- Department of Agronomy, Purdue University, West Lafayette, Indiana 47907
| | - Biao Zhang
- Department of Agronomy, Purdue University, West Lafayette, Indiana 47907
| | - Damon Lisch
- Department of Botany and Plant Pathology, Purdue University, West Lafayette, Indiana 47907
- Center for Plant Biology, Purdue University, West Lafayette, Indiana 47907
| | - Jianxin Ma
- Department of Agronomy, Purdue University, West Lafayette, Indiana 47907
- Center for Plant Biology, Purdue University, West Lafayette, Indiana 47907
| |
Collapse
|
13
|
Bousios A, Gaut BS, Darzentas N. Considerations and complications of mapping small RNA high-throughput data to transposable elements. Mob DNA 2017; 8:3. [PMID: 28228849 PMCID: PMC5311732 DOI: 10.1186/s13100-017-0086-z] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2016] [Accepted: 01/31/2017] [Indexed: 12/21/2022] Open
Abstract
BACKGROUND High-throughput sequencing (HTS) has revolutionized the way in which epigenetic research is conducted. When coupled with fully-sequenced genomes, millions of small RNA (sRNA) reads are mapped to regions of interest and the results scrutinized for clues about epigenetic mechanisms. However, this approach requires careful consideration in regards to experimental design, especially when one investigates repetitive parts of genomes such as transposable elements (TEs), or when such genomes are large, as is often the case in plants. RESULTS Here, in an attempt to shed light on complications of mapping sRNAs to TEs, we focus on the 2,300 Mb maize genome, 85% of which is derived from TEs, and scrutinize methodological strategies that are commonly employed in TE studies. These include choices for the reference dataset, the normalization of multiply mapping sRNAs, and the selection among sRNA metrics. We further examine how these choices influence the relationship between sRNAs and the critical feature of TE age, and contrast their effect on low copy genomic regions and other popular HTS data. CONCLUSIONS Based on our analyses, we share a series of take-home messages that may help with the design, implementation, and interpretation of high-throughput TE epigenetic studies specifically, but our conclusions may also apply to any work that involves analysis of HTS data.
Collapse
Affiliation(s)
- Alexandros Bousios
- School of Life Sciences, University of Sussex, Brighton, East Sussex BN1 9RH UK
| | - Brandon S. Gaut
- Department of Ecology and Evolutionary Biology, UC Irvine, Irvine, CA 92697 USA
| | - Nikos Darzentas
- Central European Institute of Technology, Masaryk University, Brno, 62500 Czech Republic
| |
Collapse
|
14
|
Zhang Y, Fan C, Li S, Chen Y, Wang RRC, Zhang X, Han F, Hu Z. The Diversity of Sequence and Chromosomal Distribution of New Transposable Element-Related Segments in the Rye Genome Revealed by FISH and Lineage Annotation. FRONTIERS IN PLANT SCIENCE 2017; 8:1706. [PMID: 29046683 PMCID: PMC5632726 DOI: 10.3389/fpls.2017.01706] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/21/2017] [Accepted: 09/19/2017] [Indexed: 05/18/2023]
Abstract
Transposable elements (TEs) in plant genomes exhibit a great variety of structure, sequence content and copy number, making them important drivers for species diversity and genome evolution. Even though a genome-wide statistic summary of TEs in rye has been obtained using high-throughput DNA sequencing technology, the accurate diversity of TEs in rye, as well as their chromosomal distribution and evolution, remains elusive due to the repetitive sequence assembling problems and the high dynamic and nested nature of TEs. In this study, using genomic plasmid library construction combined with dot-blot hybridization and fluorescence in situ hybridization (FISH) analysis, we successfully isolated 70 unique FISH-positive TE-related sequences including 47 rye genome specific ones: 30 showed homology or partial homology with previously FISH characterized sequences and 40 have not been characterized. Among the 70 sequences, 48 sequences carried Ty3/gypsy-derived segments, 7 sequences carried Ty1/copia-derived segments and 15 sequences carried segments homologous with multiple TE families. 26 TE lineages were found in the 70 sequences, and among these lineages, Wilma was found in sequences dispersed in all chromosome regions except telomeric positions; Abiba was found in sequences predominantly located at pericentromeric and centromeric positions; Wis, Carmilla, and Inga were found in sequences displaying signals dispersed from distal regions toward pericentromeric positions; except DNA transposon lineages, all the other lineages were found in sequences displaying signals dispersed from proximal regions toward distal regions. A high percentage (21.4%) of chimeric sequences were identified in this study and their high abundance in rye genome suggested that new TEs might form through recombination and nested transposition. Our results also gave proofs that diverse TE lineages were arranged at centromeric and pericentromeric positions in rye, and lineages like Abiba might play a role in their structural organization and function. All these results might help in understanding the diversity and evolution of TEs in rye, as well as their driving forces in rye genome organization and evolution.
Collapse
Affiliation(s)
- Yingxin Zhang
- Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China
- Center for Life Science, University of Chinese Academy of Sciences, Beijing, China
| | - Chengming Fan
- Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China
- *Correspondence: Chengming Fan, Zanmin Hu,
| | - Shuangshuang Li
- Department of Life Science, Henan Normal University, Xinxiang, China
| | - Yuhong Chen
- Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China
| | - Richard R.-C. Wang
- Forage and Range Research Laboratory, United States Department of Agriculture, Agricultural Research Service, Utah State University, Logan, UT, United States
| | - Xiangqi Zhang
- Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China
| | - Fangpu Han
- Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China
| | - Zanmin Hu
- Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China
- Center for Life Science, University of Chinese Academy of Sciences, Beijing, China
- *Correspondence: Chengming Fan, Zanmin Hu,
| |
Collapse
|
15
|
Cuerda-Gil D, Slotkin RK. Non-canonical RNA-directed DNA methylation. NATURE PLANTS 2016; 2:16163. [PMID: 27808230 DOI: 10.1038/nplants.2016.163] [Citation(s) in RCA: 152] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/27/2016] [Accepted: 09/26/2016] [Indexed: 05/18/2023]
Abstract
Small RNA-directed DNA methylation (RdDM) has been extensively studied in plants, resulting in a deep understanding of a major 'canonical RdDM' mechanism. However, current models of canonical RdDM cannot explain how this self-perpetuating mechanism is initiated. Recent investigations into the initiation of epigenetic silencing have determined that there are several alternative 'non-canonical RdDM' pathways that function through distinct mechanisms to modify chromatin. This Review aims to illustrate the diversity of non-canonical RdDM mechanisms described to date, recognize common themes within this dizzying array of interconnected pathways, and identify the key unanswered questions remaining in this field.
Collapse
Affiliation(s)
- Diego Cuerda-Gil
- Department of Molecular Genetics, The Ohio State University, 500 Aronoff Laboratory, 318 West Twelfth Avenue, Columbus, Ohio 43210, USA
| | - R Keith Slotkin
- Department of Molecular Genetics, The Ohio State University, 500 Aronoff Laboratory, 318 West Twelfth Avenue, Columbus, Ohio 43210, USA
- Center for RNA Biology, The Ohio State University, 105 Biological Sciences Building, 484 West Twelfth Avenue, Columbus, Ohio 43210, USA
| |
Collapse
|
16
|
Bousios A, Gaut BS. Mechanistic and evolutionary questions about epigenetic conflicts between transposable elements and their plant hosts. CURRENT OPINION IN PLANT BIOLOGY 2016; 30:123-33. [PMID: 26950253 DOI: 10.1016/j.pbi.2016.02.009] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/20/2015] [Revised: 02/16/2016] [Accepted: 02/17/2016] [Indexed: 05/02/2023]
Abstract
Transposable elements (TEs) constitute the majority of plant genomes, but most are epigenetically inactivated by their host. Research over the last decade has elucidated many of the molecular components that are required for TE silencing. In contrast, the evolutionary dynamics between TEs and silencing pathways are less clear. Here, we discuss current information about these dynamics from both mechanistic and evolutionary perspectives. We highlight new evidence that palindromic sequences within TEs may act as signals for host recognition and that cis-regulatory regions of TEs may be sites of ongoing arms races with host defenses. We also discuss patterns of TE aging after they are silenced; while there is not yet a consensus, it appears that TEs are removed more rapidly near genes, such that older TE insertions tend to be farther from genes. We conclude by discussing the energetic costs for maintaining silencing pathways, which appear to be substantive. The maintenance of silencing pathways across many species suggests that epigenetic emergencies are frequent.
Collapse
Affiliation(s)
| | - Brandon S Gaut
- Department of Ecology and Evolutionary Biology, UC Irvine, Irvine, CA 92697, USA.
| |
Collapse
|
17
|
Springer NM, Lisch D, Li Q. Creating Order from Chaos: Epigenome Dynamics in Plants with Complex Genomes. THE PLANT CELL 2016; 28:314-25. [PMID: 26869701 PMCID: PMC4790878 DOI: 10.1105/tpc.15.00911] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/26/2015] [Accepted: 02/10/2016] [Indexed: 05/02/2023]
Abstract
Flowering plants have strikingly distinct genomes, although they contain a similar suite of expressed genes. The diversity of genome structures and organization is largely due to variation in transposable elements (TEs) and whole-genome duplication (WGD) events. We review evidence that chromatin modifications and epigenetic regulation are intimately associated with TEs and likely play a role in mediating the effects of WGDs. We hypothesize that the current structure of a genome is the result of various TE bursts and WGDs and it is likely that the silencing mechanisms and the chromatin structure of a genome have been shaped by these events. This suggests that the specific mechanisms targeting chromatin modifications and epigenomic patterns may vary among different species. Many crop species have likely evolved chromatin-based mechanisms to tolerate silenced TEs near actively expressed genes. These interactions of heterochromatin and euchromatin are likely to have important roles in modulating gene expression and variability within species.
Collapse
Affiliation(s)
- Nathan M Springer
- Department of Plant Biology, Microbial and Plant Genomics Institute, University of Minnesota, Saint Paul, Minnesota 55108
| | - Damon Lisch
- Department of Botany and Plant Pathology, Purdue University, West Lafayette, Indiana 47907
| | - Qing Li
- Department of Plant Biology, Microbial and Plant Genomics Institute, University of Minnesota, Saint Paul, Minnesota 55108
| |
Collapse
|