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Li WG, Li YY, Zheng CK, Li ZZ. Chromosome-level genome assembly of a cliff plant Taihangia rupestris var. ciliata provides insights into its adaptation and demographic history. BMC PLANT BIOLOGY 2024; 24:596. [PMID: 38914948 PMCID: PMC11197248 DOI: 10.1186/s12870-024-05322-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/14/2023] [Accepted: 06/21/2024] [Indexed: 06/26/2024]
Abstract
BACKGROUND Cliffs are recognized as one of the most challenging environments for plants, characterized by harsh conditions such as drought, infertile soil, and steep terrain. However, they surprisingly host ancient and diverse plant communities and play a crucial role in protecting biodiversity. The Taihang Mountains, which act as a natural boundary in eastern China, support a rich variety of plant species, including many unique to cliff habitats. However, it is little known how cliff plants adapt to harsh habitats and the demographic history in this region. RESULTS To better understand the demographic history and adaptation of cliff plants in this area, we analyzed the chromosome-level genome of a representative cliff plant, T. rupestris var. ciliata, which has a genome size of 769.5 Mb, with a scaffold N50 of 104.92 Mb. The rapid expansion of transposable elements may have contributed to the increasing genome and its ability to adapt to unique and challenging cliff habitats. Comparative analysis of the genome evolution between Taihangia and non-cliff plants in Rosaceae revealed a significant expansion of gene families associated with oxidative phosphorylation, which is likely a response to the abiotic stresses faced by cliff plants. This expansion may explain the long-term adaptation of Taihangia to harsh cliff environments. The effective population size of the two varieties has continuously decreased due to climatic fluctuations during the Quaternary period. Furthermore, significant differences in gene expression between the two varieties may explain the varied leaf phenotypes and adaptations to harsh conditions in different natural distributions. CONCLUSION Our study highlights the extraordinary adaptation of T. rupestris var. ciliata, shedding light on the evolution of cliff plants worldwide.
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Affiliation(s)
- Wei-Guo Li
- School of Resource and Environment, Henan Polytechnic University, Jiaozuo, Henan, 454000, China.
| | - Yuan-Yuan Li
- School of Resource and Environment, Henan Polytechnic University, Jiaozuo, Henan, 454000, China
| | - Chuan-Kun Zheng
- School of Resource and Environment, Henan Polytechnic University, Jiaozuo, Henan, 454000, China
| | - Zhi-Zhong Li
- Wuhan Botanical Garden, Chinese Academy of Sciences, Wuhan, 430074, China.
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2
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Thieme M, Minadakis N, Himber C, Keller B, Xu W, Rutowicz K, Matteoli C, Böhrer M, Rymen B, Laudencia-Chingcuanco D, Vogel JP, Sibout R, Stritt C, Blevins T, Roulin AC. Transposition of HOPPLA in siRNA-deficient plants suggests a limited effect of the environment on retrotransposon mobility in Brachypodium distachyon. PLoS Genet 2024; 20:e1011200. [PMID: 38470914 PMCID: PMC10959353 DOI: 10.1371/journal.pgen.1011200] [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: 10/30/2023] [Revised: 03/22/2024] [Accepted: 02/23/2024] [Indexed: 03/14/2024] Open
Abstract
Long terminal repeat retrotransposons (LTR-RTs) are powerful mutagens regarded as a major source of genetic novelty and important drivers of evolution. Yet, the uncontrolled and potentially selfish proliferation of LTR-RTs can lead to deleterious mutations and genome instability, with large fitness costs for their host. While population genomics data suggest that an ongoing LTR-RT mobility is common in many species, the understanding of their dual role in evolution is limited. Here, we harness the genetic diversity of 320 sequenced natural accessions of the Mediterranean grass Brachypodium distachyon to characterize how genetic and environmental factors influence plant LTR-RT dynamics in the wild. When combining a coverage-based approach to estimate global LTR-RT copy number variations with mobilome-sequencing of nine accessions exposed to eight different stresses, we find little evidence for a major role of environmental factors in LTR-RT accumulations in B. distachyon natural accessions. Instead, we show that loss of RNA polymerase IV (Pol IV), which mediates RNA-directed DNA methylation in plants, results in high transcriptional and transpositional activities of RLC_BdisC024 (HOPPLA) LTR-RT family elements, and that these effects are not stress-specific. This work supports findings indicating an ongoing mobility in B. distachyon and reveals that host RNA-directed DNA methylation rather than environmental factors controls their mobility in this wild grass model.
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Affiliation(s)
- Michael Thieme
- Department of Plant and Microbial Biology, University of Zurich, Zurich, Switzerland
| | - Nikolaos Minadakis
- Department of Plant and Microbial Biology, University of Zurich, Zurich, Switzerland
| | - Christophe Himber
- Institut de Biologie Moléculaire des Plantes, Centre National de la Recherche Scientifique, Université de Strasbourg, Strasbourg, France
| | - Bettina Keller
- Department of Plant and Microbial Biology, University of Zurich, Zurich, Switzerland
| | - Wenbo Xu
- Department of Plant and Microbial Biology, University of Zurich, Zurich, Switzerland
| | - Kinga Rutowicz
- Department of Plant and Microbial Biology, University of Zurich, Zurich, Switzerland
| | - Calvin Matteoli
- Institut de Biologie Moléculaire des Plantes, Centre National de la Recherche Scientifique, Université de Strasbourg, Strasbourg, France
| | - Marcel Böhrer
- Institut de Biologie Moléculaire des Plantes, Centre National de la Recherche Scientifique, Université de Strasbourg, Strasbourg, France
| | - Bart Rymen
- Institut de Biologie Moléculaire des Plantes, Centre National de la Recherche Scientifique, Université de Strasbourg, Strasbourg, France
| | - Debbie Laudencia-Chingcuanco
- United States Department of Agriculture Agricultural Research Service Western Regional Research Center, Albany, California, United States of America
| | - John P. Vogel
- United States Department of Energy Joint Genome Institute, Lawrence Berkeley National Laboratory, Berkeley, California, United States of America
| | - Richard Sibout
- Institut National de la Recherche Agronomique Unité BIA- 1268 Biopolymères Interactions Assemblages Equipe Paroi Végétale et Polymères Pariétaux (PVPP), Nantes, France
| | - Christoph Stritt
- Swiss Tropical and Public Health Institute (Swiss TPH), Allschwil, Switzerland
| | - Todd Blevins
- Institut de Biologie Moléculaire des Plantes, Centre National de la Recherche Scientifique, Université de Strasbourg, Strasbourg, France
| | - Anne C. Roulin
- Department of Plant and Microbial Biology, University of Zurich, Zurich, Switzerland
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3
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Hassan AH, Mokhtar MM, El Allali A. Transposable elements: multifunctional players in the plant genome. FRONTIERS IN PLANT SCIENCE 2024; 14:1330127. [PMID: 38239225 PMCID: PMC10794571 DOI: 10.3389/fpls.2023.1330127] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/30/2023] [Accepted: 12/06/2023] [Indexed: 01/22/2024]
Abstract
Transposable elements (TEs) are indispensable components of eukaryotic genomes that play diverse roles in gene regulation, recombination, and environmental adaptation. Their ability to mobilize within the genome leads to gene expression and DNA structure changes. TEs serve as valuable markers for genetic and evolutionary studies and facilitate genetic mapping and phylogenetic analysis. They also provide insight into how organisms adapt to a changing environment by promoting gene rearrangements that lead to new gene combinations. These repetitive sequences significantly impact genome structure, function and evolution. This review takes a comprehensive look at TEs and their applications in biotechnology, particularly in the context of plant biology, where they are now considered "genomic gold" due to their extensive functionalities. The article addresses various aspects of TEs in plant development, including their structure, epigenetic regulation, evolutionary patterns, and their use in gene editing and plant molecular markers. The goal is to systematically understand TEs and shed light on their diverse roles in plant biology.
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Affiliation(s)
- Asmaa H. Hassan
- Bioinformatics Laboratory, College of Computing, Mohammed VI Polytechnic University, Ben Guerir, Morocco
- Agricultural Genetic Engineering Research Institute, Agriculture Research Center, Giza, Egypt
| | - Morad M. Mokhtar
- Bioinformatics Laboratory, College of Computing, Mohammed VI Polytechnic University, Ben Guerir, Morocco
- Agricultural Genetic Engineering Research Institute, Agriculture Research Center, Giza, Egypt
| | - Achraf El Allali
- Bioinformatics Laboratory, College of Computing, Mohammed VI Polytechnic University, Ben Guerir, Morocco
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4
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Bock DG, Cai Z, Elphinstone C, González-Segovia E, Hirabayashi K, Huang K, Keais GL, Kim A, Owens GL, Rieseberg LH. Genomics of plant speciation. PLANT COMMUNICATIONS 2023; 4:100599. [PMID: 37050879 PMCID: PMC10504567 DOI: 10.1016/j.xplc.2023.100599] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/26/2023] [Revised: 03/21/2023] [Accepted: 04/06/2023] [Indexed: 06/19/2023]
Abstract
Studies of plants have been instrumental for revealing how new species originate. For several decades, botanical research has complemented and, in some cases, challenged concepts on speciation developed via the study of other organisms while also revealing additional ways in which species can form. Now, the ability to sequence genomes at an unprecedented pace and scale has allowed biologists to settle decades-long debates and tackle other emerging challenges in speciation research. Here, we review these recent genome-enabled developments in plant speciation. We discuss complications related to identification of reproductive isolation (RI) loci using analyses of the landscape of genomic divergence and highlight the important role that structural variants have in speciation, as increasingly revealed by new sequencing technologies. Further, we review how genomics has advanced what we know of some routes to new species formation, like hybridization or whole-genome duplication, while casting doubt on others, like population bottlenecks and genetic drift. While genomics can fast-track identification of genes and mutations that confer RI, we emphasize that follow-up molecular and field experiments remain critical. Nonetheless, genomics has clarified the outsized role of ancient variants rather than new mutations, particularly early during speciation. We conclude by highlighting promising avenues of future study. These include expanding what we know so far about the role of epigenetic and structural changes during speciation, broadening the scope and taxonomic breadth of plant speciation genomics studies, and synthesizing information from extensive genomic data that have already been generated by the plant speciation community.
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Affiliation(s)
- Dan G Bock
- Department of Botany and Biodiversity Research Centre, University of British Columbia, Vancouver, BC, Canada
| | - Zhe Cai
- Department of Botany and Biodiversity Research Centre, University of British Columbia, Vancouver, BC, Canada
| | - Cassandra Elphinstone
- Department of Botany and Biodiversity Research Centre, University of British Columbia, Vancouver, BC, Canada
| | - Eric González-Segovia
- Department of Botany and Biodiversity Research Centre, University of British Columbia, Vancouver, BC, Canada
| | | | - Kaichi Huang
- Department of Botany and Biodiversity Research Centre, University of British Columbia, Vancouver, BC, Canada
| | - Graeme L Keais
- Department of Botany and Biodiversity Research Centre, University of British Columbia, Vancouver, BC, Canada
| | - Amy Kim
- Department of Botany and Biodiversity Research Centre, University of British Columbia, Vancouver, BC, Canada
| | - Gregory L Owens
- Department of Biology, University of Victoria, Victoria, BC, Canada
| | - Loren H Rieseberg
- Department of Botany and Biodiversity Research Centre, University of British Columbia, Vancouver, BC, Canada.
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Zhao P, Gu L, Gao Y, Pan Z, Liu L, Li X, Zhou H, Yu D, Han X, Qian L, Liu GE, Fang L, Wang Z. Young SINEs in pig genomes impact gene regulation, genetic diversity, and complex traits. Commun Biol 2023; 6:894. [PMID: 37652983 PMCID: PMC10471783 DOI: 10.1038/s42003-023-05234-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2022] [Accepted: 08/09/2023] [Indexed: 09/02/2023] Open
Abstract
Transposable elements (TEs) are a major source of genetic polymorphisms and play a role in chromatin architecture, gene regulatory networks, and genomic evolution. However, their functional role in pigs and contributions to complex traits are largely unknown. We created a catalog of TEs (n = 3,087,929) in pigs and found that young SINEs were predominantly silenced by histone modifications, DNA methylation, and decreased accessibility. However, some transcripts from active young SINEs showed high tissue-specificity, as confirmed by analyzing 3570 RNA-seq samples. We also detected 211,067 dimorphic SINEs in 374 individuals, including 340 population-specific ones associated with local adaptation. Mapping these dimorphic SINEs to genome-wide associations of 97 complex traits in pigs, we found 54 candidate genes (e.g., ANK2 and VRTN) that might be mediated by TEs. Our findings highlight the important roles of young SINEs and provide a supplement for genotype-to-phenotype associations and modern breeding in pigs.
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Affiliation(s)
- Pengju Zhao
- Hainan Institute, Zhejiang University, Yongyou Industry Park, Yazhou Bay Sci-Tech City, Sanya, 572000, China
- College of Animal Sciences, Zhejiang University, Hangzhou, Zhejiang, 310058, China
| | - Lihong Gu
- Institute of Animal Science & Veterinary Medicine, Hainan Academy of Agricultural Sciences, No. 14 Xingdan Road, Haikou, 571100, China
| | - Yahui Gao
- Animal Genomics and Improvement Laboratory, Beltsville Agricultural Research Center, Agricultural Research Service, USDA, Beltsville, MD, 20705, USA
| | - Zhangyuan Pan
- Department of Animal Science, University of California, Davis, CA, 95616, USA
| | - Lei Liu
- Shenzhen Branch, Guangdong Laboratory of Lingnan Modern Agriculture, Genome Analysis Laboratory of the Ministry of Agriculture and Rural Affairs, Agricultural Genomics Institute at Shenzhen, Chinese Academy of Agricultural Sciences, Shenzhen, 518124, China
| | - Xingzheng Li
- Shenzhen Branch, Guangdong Laboratory of Lingnan Modern Agriculture, Genome Analysis Laboratory of the Ministry of Agriculture and Rural Affairs, Agricultural Genomics Institute at Shenzhen, Chinese Academy of Agricultural Sciences, Shenzhen, 518124, China
| | - Huaijun Zhou
- Department of Animal Science, University of California, Davis, CA, 95616, USA
| | - Dongyou Yu
- Hainan Institute, Zhejiang University, Yongyou Industry Park, Yazhou Bay Sci-Tech City, Sanya, 572000, China
- College of Animal Sciences, Zhejiang University, Hangzhou, Zhejiang, 310058, China
| | - Xinyan Han
- Hainan Institute, Zhejiang University, Yongyou Industry Park, Yazhou Bay Sci-Tech City, Sanya, 572000, China
- College of Animal Sciences, Zhejiang University, Hangzhou, Zhejiang, 310058, China
| | - Lichun Qian
- Hainan Institute, Zhejiang University, Yongyou Industry Park, Yazhou Bay Sci-Tech City, Sanya, 572000, China
- College of Animal Sciences, Zhejiang University, Hangzhou, Zhejiang, 310058, China
| | - George E Liu
- Animal Genomics and Improvement Laboratory, Beltsville Agricultural Research Center, Agricultural Research Service, USDA, Beltsville, MD, 20705, USA.
| | - Lingzhao Fang
- Center for Quantitative Genetics and Genomics, Aarhus University, Aarhus, 8000, Denmark.
| | - Zhengguang Wang
- Hainan Institute, Zhejiang University, Yongyou Industry Park, Yazhou Bay Sci-Tech City, Sanya, 572000, China.
- College of Animal Sciences, Zhejiang University, Hangzhou, Zhejiang, 310058, China.
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6
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Kumar M, Rani K. Epigenomics in stress tolerance of plants under the climate change. Mol Biol Rep 2023:10.1007/s11033-023-08539-6. [PMID: 37294468 DOI: 10.1007/s11033-023-08539-6] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2022] [Accepted: 05/19/2023] [Indexed: 06/10/2023]
Abstract
BACKGROUND Climate change has had a tremendous impact on the environment in general as well as agricultural crops grown in these situations as time passed. Agricultural production of crops is less suited and of lower quality due to disturbances in plant metabolism brought on by sensitivity to environmental stresses, which are brought on by climate change. Abiotic stressors that are specific to climate change, including as drought, extremes in temperature, increasing CO2, waterlogging from heavy rain, metal toxicity, and pH changes, are known to negatively affect an array of species. Plants adapt to these challenges by undergoing genome-wide epigenetic changes, which are frequently accompanied by differences in transcriptional gene expression. The sum of a cell's biochemical modifications to its nuclear DNA, post-translational modifications to histones, and variations in the synthesis of non-coding RNAs is called an epigenome. These modifications frequently lead to variations in gene expression that occur without any alteration in the underlying base sequence. EPIGENETIC MECHANISMS AND MARKS The methylation of homologous loci by three different modifications-genomic (DNA methylation), chromatin (histone modifications), and RNA-directed DNA methylation (RdDM)-could be regarded as epigenetic mechanisms that control the regulation of differential gene expression. Stresses from the environment cause chromatin remodelling, which enables plant cells to adjust their expression patterns temporarily or permanently. EPIGENOMICS' CONSEQUENCES FOR GENOME STABILITY AND GENE EXPRESSION: DNA methylation affects gene expression in response to abiotic stressors by blocking or suppressing transcription. Environmental stimuli cause changes in DNA methylation levels, either upward in the case of hypermethylation or downward in the case of hypomethylation. The type of stress response that occurs as a result also affects the degree of DNA methylation alterations. Stress is also influenced by DRM2 and CMT3 methylating CNN, CNG, and CG. Both plant development and stress reactions depend on histone changes. Gene up-regulation is associated with histone tail phosphorylation, ubiquitination, and acetylation, while gene down-regulation is associated with de-acetylation and biotinylation. Plants undergo a variety of dynamic changes to histone tails in response to abiotic stressors. The relevance of these transcripts against stress is highlighted by the accumulation of numerous additional antisense transcripts, a source of siRNAs, caused by abiotic stresses. The study highlights the finding that plants can be protected from a range of abiotic stresses by epigenetic mechanisms such DNA methylation, histone modification, and RNA-directed DNA methylation. TRANSGENERATIONAL INHERITANCE AND SOURCES OF EPIGENETIC VARIATION: Stress results in the formation of epialleles, which are either transient or enduring epigenetic stress memory in plants. After the stress is gone, the stable memory is kept for the duration of the plant's remaining developmental cycles or passed on to the next generations, leading to plant evolution and adaptability. The bulk of epigenetic changes brought on by stress are temporary and return to normal after the stress has passed. Some of the modifications, however, might be long-lasting and transmitted across mitotic or even meiotic cell divisions. Epialleles often have genetic or non-genetic causes. Epialleles can arise spontaneously due to improper methylation state maintenance, short RNA off-target effects, or other non-genetic causes. Developmental or environmental variables that influence the stability of epigenetic states or direct chromatin modifications may also be non-genetic drivers of epigenetic variation. Transposon insertions that change local chromatin and structural rearrangements, such copy number changes that are genetically related or unrelated, are two genetic sources of epialleles. EPIGENOMICS IN CROP IMPROVEMENT To include epigenetics into crop breeding, it is necessary to create epigenetic variation as well as to identify and evaluate epialleles. Epigenome editing or epi-genomic selection may be required for epiallele creation and identification. In order to combat the challenges given by changing environments, these epigenetic mechanisms have generated novel epialleles that can be exploited to develop new crop types that are more climate-resilient. Numerous techniques can be used to alter the epigenome generally or at specific target loci in order to induce the epigenetic alterations necessary for crop development. Technologies like CRISPR/Cas9 and dCas, which have recently advanced, have opened up new avenues for the study of epigenetics. Epialleles could be employed in epigenomics-assisted breeding in addition to sequence-based markers for crop breeding. CONCLUSIONS AND FUTURE PROSPECTUS A few of the exciting questions that still need to be resolved in the area of heritable epigenetic variation include a better understanding of the epigenetic foundation of characteristics, the stability and heritability of epialleles, and the sources of epigenetic variation in crops. Investigating long intergenic non-coding RNAs (lincRNAs) as an epigenetic process might open up a new path to understanding crop plant's ability to withstand abiotic stress. For many of these technologies and approaches to be more applicable and deployable at a lower cost, technological breakthroughs will also be necessary. Breeders will probably need to pay closer attention to crop epialleles and how they can affect future responses to climate changes. The development of epialleles suitable for particular environmental circumstances may be made possible by creating targeted epigenetic changes in pertinent genes and by comprehending the molecular underpinnings of trans generational epigenetic inheritance. More research on a wider variety of plant species is required in order to fully comprehend the mechanisms that produce and stabilise epigenetic variation in crops. In addition to a collaborative and multidisciplinary effort by researchers in many fields of plant science, this will require a greater integration of the epigenomic data gathered in many crops. Before it may be applied generally, more study is required.
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Affiliation(s)
- Mithlesh Kumar
- AICRN On Potential Crops, ARS Mandor, Agriculture University, Jodhpur, 342 304, Rajasthan, India.
| | - Kirti Rani
- ICAR-National Bureau of Plant Genetic Resources (NBPGR), Regional Station, Jodhpur, 342 003, Rajasthan, India
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7
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Arvas YE, Marakli S, Kaya Y, Kalendar R. The power of retrotransposons in high-throughput genotyping and sequencing. FRONTIERS IN PLANT SCIENCE 2023; 14:1174339. [PMID: 37180380 PMCID: PMC10167742 DOI: 10.3389/fpls.2023.1174339] [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: 02/26/2023] [Accepted: 04/11/2023] [Indexed: 05/16/2023]
Abstract
The use of molecular markers has become an essential part of molecular genetics through their application in numerous fields, which includes identification of genes associated with targeted traits, operation of backcrossing programs, modern plant breeding, genetic characterization, and marker-assisted selection. Transposable elements are a core component of all eukaryotic genomes, making them suitable as molecular markers. Most of the large plant genomes consist primarily of transposable elements; variations in their abundance contribute to most of the variation in genome size. Retrotransposons are widely present throughout plant genomes, and replicative transposition enables them to insert into the genome without removing the original elements. Various applications of molecular markers have been developed that exploit the fact that these genetic elements are present everywhere and their ability to stably integrate into dispersed chromosomal localities that are polymorphic within a species. The ongoing development of molecular marker technologies is directly related to the deployment of high-throughput genotype sequencing platforms, and this research is of considerable significance. In this review, the practical application to molecular markers, which is a use of technology of interspersed repeats in the plant genome were examined using genomic sources from the past to the present. Prospects and possibilities are also presented.
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Affiliation(s)
- Yunus Emre Arvas
- Department of Biology, Faculty of Sciences, Karadeniz Technical University, Trabzon, Türkiye
| | - Sevgi Marakli
- Department of Molecular Biology and Genetics, Faculty of Arts and Sciences, Yildiz Technical University, Istanbul, Türkiye
| | - Yılmaz Kaya
- Agricultural Biotechnology Department, Faculty of Agriculture, Ondokuz Mayıs University, Samsun, Türkiye
- Department of Biology, Faculty of Science, Kyrgyz-Turkish Manas University, Bishkek, Kyrgyzstan
| | - Ruslan Kalendar
- Center for Life Sciences, National Laboratory Astana, Nazarbayev University, Astana, Kazakhstan
- Institute of Biotechnology, Helsinki Institute of Life Science (HiLIFE), University of Helsinki, Helsinki, Finland
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Camelo-Júnior AE, Ferreira AWC, Andrade IM, Mayo SJ, Nollet F, Silva JL, Barros MC, Fraga E, Pessoa EM. Species delimitation in the Trichocentrum cepula (Oncidiinae, Orchidaceae) complex: a multidisciplinary approach. SYST BIODIVERS 2022. [DOI: 10.1080/14772000.2022.2099478] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/14/2022]
Affiliation(s)
- Antonio E. Camelo-Júnior
- Programa de Pós-Graduação em Biodiversidade, Ambiente e Saúde, Universidade Estadual do Maranhão, Campus Caxias, 65.604-380, Caxias, Maranhão, Brazil
| | | | - Ivanilza M. Andrade
- Núcleo de Pesquisa em Biodiversidade e Biotecnologia, Biotec, Campus de Parnaíba, Universidade Federal do Delta do Piauí, Parnaíba, Piauí, Brazil
| | - Simon J. Mayo
- Royal Botanic Gardens, Kew, Richmond TW9 3AE, Surrey, UK
| | - Felipe Nollet
- Departamento de Biologia, Programa de Pós-Graduação em Botânica, Universidade Federal Rural de Pernambuco, Dois Irmãos, Recife, 52171–900, Pernambuco, Brazil
| | - José L. Silva
- Departamento de Ciências Biológicas, Universidade Federal da Paraíba Centro de Ciências Agrárias, Campus II, Areia, 58397-000, Paraíba, Brazil
| | - Maria C. Barros
- Programa de Pós-Graduação em Biodiversidade, Ambiente e Saúde, Universidade Estadual do Maranhão, Campus Caxias, 65.604-380, Caxias, Maranhão, Brazil
| | - Elmary Fraga
- Programa de Pós-Graduação em Biodiversidade, Ambiente e Saúde, Universidade Estadual do Maranhão, Campus Caxias, 65.604-380, Caxias, Maranhão, Brazil
| | - Edlley M. Pessoa
- Programa de Pós-Graduação em Biodiversidade, Ambiente e Saúde, Universidade Estadual do Maranhão, Campus Caxias, 65.604-380, Caxias, Maranhão, Brazil
- Departamento de Botânica e Ecologia, Universidade Federal do Mato Grosso, Cuiabá, 78060-900, Mato Grosso, Brazil
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9
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Papolu PK, Ramakrishnan M, Mullasseri S, Kalendar R, Wei Q, Zou L, Ahmad Z, Vinod KK, Yang P, Zhou M. Retrotransposons: How the continuous evolutionary front shapes plant genomes for response to heat stress. FRONTIERS IN PLANT SCIENCE 2022; 13:1064847. [PMID: 36570931 PMCID: PMC9780303 DOI: 10.3389/fpls.2022.1064847] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/08/2022] [Accepted: 11/21/2022] [Indexed: 05/28/2023]
Abstract
Long terminal repeat retrotransposons (LTR retrotransposons) are the most abundant group of mobile genetic elements in eukaryotic genomes and are essential in organizing genomic architecture and phenotypic variations. The diverse families of retrotransposons are related to retroviruses. As retrotransposable elements are dispersed and ubiquitous, their "copy-out and paste-in" life cycle of replicative transposition leads to new genome insertions without the excision of the original element. The overall structure of retrotransposons and the domains responsible for the various phases of their replication is highly conserved in all eukaryotes. The two major superfamilies of LTR retrotransposons, Ty1/Copia and Ty3/Gypsy, are distinguished and dispersed across the chromosomes of higher plants. Members of these superfamilies can increase in copy number and are often activated by various biotic and abiotic stresses due to retrotransposition bursts. LTR retrotransposons are important drivers of species diversity and exhibit great variety in structure, size, and mechanisms of transposition, making them important putative actors in genome evolution. Additionally, LTR retrotransposons influence the gene expression patterns of adjacent genes by modulating potential small interfering RNA (siRNA) and RNA-directed DNA methylation (RdDM) pathways. Furthermore, comparative and evolutionary analysis of the most important crop genome sequences and advanced technologies have elucidated the epigenetics and structural and functional modifications driven by LTR retrotransposon during speciation. However, mechanistic insights into LTR retrotransposons remain obscure in plant development due to a lack of advancement in high throughput technologies. In this review, we focus on the key role of LTR retrotransposons response in plants during heat stress, the role of centromeric LTR retrotransposons, and the role of LTR retrotransposon markers in genome expression and evolution.
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Affiliation(s)
- Pradeep K. Papolu
- State Key Laboratory of Subtropical Silviculture, Bamboo Industry Institute, Zhejiang A&F University, Hangzhou, Zhejiang, China
| | - Muthusamy Ramakrishnan
- State Key Laboratory of Subtropical Silviculture, Bamboo Industry Institute, Zhejiang A&F University, Hangzhou, Zhejiang, China
- Co-Innovation Center for Sustainable Forestry in Southern China, Bamboo Research Institute, Key Laboratory of National Forestry and Grassland Administration on Subtropical Forest Biodiversity Conservation, College of Biology and the Environment, Nanjing Forestry University, Nanjing, Jiangsu, China
| | - Sileesh Mullasseri
- Department of Zoology, St. Albert’s College (Autonomous), Kochi, Kerala, India
| | - Ruslan Kalendar
- Helsinki Institute of Life Science HiLIFE, Biocenter 3, University of Helsinki, Helsinki, Finland
- National Laboratory Astana, Nazarbayev University, Astana, Kazakhstan
| | - Qiang Wei
- Co-Innovation Center for Sustainable Forestry in Southern China, Bamboo Research Institute, Key Laboratory of National Forestry and Grassland Administration on Subtropical Forest Biodiversity Conservation, College of Biology and the Environment, Nanjing Forestry University, Nanjing, Jiangsu, China
| | - Long−Hai Zou
- State Key Laboratory of Subtropical Silviculture, Bamboo Industry Institute, Zhejiang A&F University, Hangzhou, Zhejiang, China
| | - Zishan Ahmad
- Co-Innovation Center for Sustainable Forestry in Southern China, Bamboo Research Institute, Key Laboratory of National Forestry and Grassland Administration on Subtropical Forest Biodiversity Conservation, College of Biology and the Environment, Nanjing Forestry University, Nanjing, Jiangsu, China
| | | | - Ping Yang
- State Key Laboratory of Subtropical Silviculture, Bamboo Industry Institute, Zhejiang A&F University, Hangzhou, Zhejiang, China
- Zhejiang Provincial Collaborative Innovation Center for Bamboo Resources and High-Efficiency Utilization, Zhejiang A&F University, Hangzhou, Zhejiang, China
| | - Mingbing Zhou
- State Key Laboratory of Subtropical Silviculture, Bamboo Industry Institute, Zhejiang A&F University, Hangzhou, Zhejiang, China
- Zhejiang Provincial Collaborative Innovation Center for Bamboo Resources and High-Efficiency Utilization, Zhejiang A&F University, Hangzhou, Zhejiang, China
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10
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Bajus M, Macko-Podgórni A, Grzebelus D, Baránek M. A review of strategies used to identify transposition events in plant genomes. FRONTIERS IN PLANT SCIENCE 2022; 13:1080993. [PMID: 36531345 PMCID: PMC9751208 DOI: 10.3389/fpls.2022.1080993] [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: 10/26/2022] [Accepted: 11/17/2022] [Indexed: 06/17/2023]
Abstract
Transposable elements (TEs) were initially considered redundant and dubbed 'junk DNA'. However, more recently they were recognized as an essential element of genome plasticity. In nature, they frequently become active upon exposition of the host to stress conditions. Even though most transposition events are neutral or even deleterious, occasionally they may happen to be beneficial, resulting in genetic novelty providing better fitness to the host. Hence, TE mobilization may promote adaptability and, in the long run, act as a significant evolutionary force. There are many examples of TE insertions resulting in increased tolerance to stresses or in novel features of crops which are appealing to the consumer. Possibly, TE-driven de novo variability could be utilized for crop improvement. However, in order to systematically study the mechanisms of TE/host interactions, it is necessary to have suitable tools to globally monitor any ongoing TE mobilization. With the development of novel potent technologies, new high-throughput strategies for studying TE dynamics are emerging. Here, we present currently available methods applied to monitor the activity of TEs in plants. We divide them on the basis of their operational principles, the position of target molecules in the process of transposition and their ability to capture real cases of actively transposing elements. Their possible theoretical and practical drawbacks are also discussed. Finally, conceivable strategies and combinations of methods resulting in an improved performance are proposed.
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Affiliation(s)
- Marko Bajus
- Mendeleum—Institute of Genetics, Faculty of Horticulture, Mendel University in Brno, Lednice, Czechia
| | - Alicja Macko-Podgórni
- Department of Plant Biology and Biotechnology, Faculty of Biotechnology and Horticulture, University of Agriculture in Krakow, Kraków, Poland
| | - Dariusz Grzebelus
- Department of Plant Biology and Biotechnology, Faculty of Biotechnology and Horticulture, University of Agriculture in Krakow, Kraków, Poland
| | - Miroslav Baránek
- Mendeleum—Institute of Genetics, Faculty of Horticulture, Mendel University in Brno, Lednice, Czechia
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11
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Singh AK, Mishra P, Kashyap SP, Karkute SG, Singh PM, Rai N, Bahadur A, Behera TK. Molecular insights into mechanisms underlying thermo-tolerance in tomato. FRONTIERS IN PLANT SCIENCE 2022; 13:1040532. [PMID: 36388532 PMCID: PMC9645296 DOI: 10.3389/fpls.2022.1040532] [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: 09/09/2022] [Accepted: 10/12/2022] [Indexed: 06/16/2023]
Abstract
Plant productivity is being seriously compromised by climate-change-induced temperature extremities. Agriculture and food safety are threatened due to global warming, and in many cases the negative impacts have already begun. Heat stress leads to significant losses in yield due to changes in growth pattern, plant phonologies, sensitivity to pests, flowering, grain filling, maturity period shrinkage, and senescence. Tomato is the second most important vegetable crop. It is very sensitive to heat stress and thus, yield losses in tomato due to heat stress could affect food and nutritional security. Tomato plants respond to heat stress with a variety of cellular, physiological, and molecular responses, beginning with the early heat sensing, followed by signal transduction, antioxidant defense, osmolyte synthesis and regulated gene expression. Recent findings suggest that specific plant organs are extremely sensitive to heat compared to the entire plant, redirecting the research more towards generative tissues. This is because, during sexual reproduction, developing pollens are the most sensitive to heat. Often, just a few degrees of temperature elevation during pollen development can have a negative effect on crop production. Furthermore, recent research has discovered certain genetic and epigenetic mechanisms playing key role in thermo-tolerance and have defined new directions for tomato heat stress response (HSR). Present challenges are to increase the understanding of molecular mechanisms underlying HS, and to identify superior genotypes with more tolerance to extreme temperatures. Several metabolites, genes, heat shock factors (HSFs) and microRNAs work together to regulate the plant HSR. The present review provides an insight into molecular mechanisms of heat tolerance and current knowledge of genetic and epigenetic control of heat-tolerance in tomato for sustainable agriculture in the future. The information will significantly contribute to improve breeding programs for development of heat tolerant cultivars.
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Affiliation(s)
- Achuit K. Singh
- Division of Crop Improvement, ICAR-Indian Institute of Vegetable Research, Varanasi, Uttar Pradesh, India
| | - Pallavi Mishra
- Division of Crop Improvement, ICAR-Indian Institute of Vegetable Research, Varanasi, Uttar Pradesh, India
| | - Sarvesh Pratap Kashyap
- Division of Crop Improvement, ICAR-Indian Institute of Vegetable Research, Varanasi, Uttar Pradesh, India
| | - Suhas G. Karkute
- Division of Crop Improvement, ICAR-Indian Institute of Vegetable Research, Varanasi, Uttar Pradesh, India
| | - Prabhakar Mohan Singh
- Division of Crop Improvement, ICAR-Indian Institute of Vegetable Research, Varanasi, Uttar Pradesh, India
| | - Nagendra Rai
- Division of Crop Improvement, ICAR-Indian Institute of Vegetable Research, Varanasi, Uttar Pradesh, India
| | - Anant Bahadur
- Division of Crop Production, ICAR-Indian Institute of Vegetable Research, Varanasi, Uttar Pradesh, India
| | - Tusar K. Behera
- Division of Crop Improvement, ICAR-Indian Institute of Vegetable Research, Varanasi, Uttar Pradesh, India
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12
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Peng H, Mirouze M, Bucher E. Extrachromosomal circular DNA: A neglected nucleic acid molecule in plants. CURRENT OPINION IN PLANT BIOLOGY 2022; 69:102263. [PMID: 35872391 DOI: 10.1016/j.pbi.2022.102263] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/25/2022] [Revised: 06/15/2022] [Accepted: 06/19/2022] [Indexed: 06/15/2023]
Abstract
Throughout the years, most plant genomic studies were focused on nuclear chromosomes. Extrachromosomal circular DNA (eccDNA) has largely been neglected for decades since its discovery in 1965. While initial research showed that eccDNAs can originate from highly repetitive sequences, recent findings show that many regions of the genome can contribute to the eccDNA pool. Currently, the biological functions of eccDNAs, if any, are a mystery but recent studies have indicated that they can be regulated by different genomic loci and contribute to stress response and adaptation. In this review, we outline current relevant technological developments facilitating eccDNA identification and the latest discoveries about eccDNAs in plants. Finally, we explore the probable functions and future research directions that could be undertaken with respect to different eccDNA sources.
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Affiliation(s)
- Haoran Peng
- Crop Genome Dynamics Group, Agroscope Changins, 1260, Nyon, Switzerland; Department of Botany and Plant Biology, Section of Biology, Faculty of Science, University of Geneva, 1211, Geneva, Switzerland
| | - Marie Mirouze
- Institut de Recherche pour le Développement (IRD), EMR269 MANGO, Université de Perpignan, 66860 Perpignan, France; Laboratory of Plant Genome and Development, Université de Perpignan, 66860, Perpignan, France.
| | - Etienne Bucher
- Crop Genome Dynamics Group, Agroscope Changins, 1260, Nyon, Switzerland.
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13
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Thieme M, Brêchet A, Bourgeois Y, Keller B, Bucher E, Roulin AC. Experimentally heat-induced transposition increases drought tolerance in Arabidopsis thaliana. THE NEW PHYTOLOGIST 2022; 236:182-194. [PMID: 35715973 PMCID: PMC9544478 DOI: 10.1111/nph.18322] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/20/2022] [Accepted: 06/10/2022] [Indexed: 05/14/2023]
Abstract
Eukaryotic genomes contain a vast diversity of transposable elements (TEs). Formerly often described as selfish and parasitic DNA sequences, TEs are now recognised as a source of genetic diversity and powerful drivers of evolution. However, because their mobility is tightly controlled by the host, studies experimentally assessing how fast TEs may mediate the emergence of adaptive traits are scarce. We exposed Arabidopsis thaliana high-copy TE lines (hcLines) with up to c. eight-fold increased copy numbers of the heat-responsive ONSEN TE to drought as a straightforward and ecologically highly relevant selection pressure. We provide evidence for increased drought tolerance in five out of the 23 tested hcLines and further pinpoint one of the causative mutations to an exonic insertion of ONSEN in the ribose-5-phosphate-isomerase 2 gene. The resulting loss-of-function mutation caused a decreased rate of photosynthesis, plant size and water consumption. Overall, we show that the heat-induced transposition of a low-copy TE increases phenotypic diversity and leads to the emergence of drought-tolerant individuals in A. thaliana. This is one of the rare empirical examples substantiating the adaptive potential of mobilised stress-responsive TEs in eukaryotes. Our work demonstrates the potential of TE-mediated loss-of-function mutations in stress adaptation.
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Affiliation(s)
- Michael Thieme
- Department of Plant and Microbial BiologyUniversity of Zurich8008ZürichSwitzerland
| | - Arthur Brêchet
- Department of Environmental Sciences – BotanyUniversity of Basel4056BaselSwitzerland
| | - Yann Bourgeois
- School of Biological SciencesUniversity of PortsmouthPO1 2DTPortsmouthUK
| | - Bettina Keller
- Department of Plant and Microbial BiologyUniversity of Zurich8008ZürichSwitzerland
| | | | - Anne C. Roulin
- Department of Plant and Microbial BiologyUniversity of Zurich8008ZürichSwitzerland
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14
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Abstract
Transposons were once thought to be junk repetitive DNA in the genome. However, their importance gradually became apparent as it became clear that they regulate gene expression, which is essential for organisms to survive, and that they are important factors in the driving force of evolution. Since there are multiple transposons in the genomes of all organisms, transposons have likely been activated and increased in copy number throughout their long history. This review focuses on environmental stress as a factor in transposon activation, paying particular attention to transposons in plants that are activated by environmental stresses. It is now known that plants respond to environmental stress in various ways, and correspondingly, many transposons respond to stress. The relationship between environmental stress and transposons is reviewed, including the mechanisms of their activation and the effects of transposon activation on host plants.
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15
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Ali S, Khan N, Tang Y. Epigenetic marks for mitigating abiotic stresses in plants. JOURNAL OF PLANT PHYSIOLOGY 2022; 275:153740. [PMID: 35716656 DOI: 10.1016/j.jplph.2022.153740] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/25/2021] [Revised: 03/02/2022] [Accepted: 05/29/2022] [Indexed: 06/15/2023]
Abstract
Abiotic stressors are one of the major factors affecting agricultural output. Plants have evolved adaptive systems to respond appropriately to various environmental cues. These responses can be accomplished by modulating or fine-tuning genetic and epigenetic regulatory mechanisms. Understanding the response of plants' molecular features to abiotic stress is a priority in the current period of continued environmental changes. Epigenetic modifications are necessary that control gene expression by changing chromatin status and recruiting various transcription regulators. The present study summarized the current knowledge on epigenetic modifications concerning plant responses to various environmental stressors. The functional relevance of epigenetic marks in regulating stress tolerance has been revealed, and epigenetic changes impact the effector genes. This study looks at the epigenetic mechanisms that govern plant abiotic stress responses, especially DNA methylation, histone methylation/acetylation, chromatin remodeling, and various metabolites. Plant breeders will benefit from a thorough understanding of these processes to create alternative crop improvement approaches. Genome editing with clustered regularly interspaced short palindromic repeat/CRISPR-associated proteins (CRISPR/Cas) provides genetic tools to make agricultural genetic engineering more sustainable and publicly acceptable.
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Affiliation(s)
- Shahid Ali
- Guangdong Provincial Key Laboratory for Plant Epigenetics, Shenzhen Key Laboratory of Marine Bioresource & Eco-environmental Science, Longhua Institute of Innovative Biotechnology, College of Life Sciences and Oceanography, Shenzhen University, Shenzhen, 518060, Guangdong Province, China; Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, College of Optoelectronic Engineering, Shenzhen University, Shenzhen, 518060, China.
| | - Naeem Khan
- Department of Agronomy, Institute of Food and Agricultural Sciences, University of Florida, FL, 32611, USA
| | - Yulin Tang
- Guangdong Provincial Key Laboratory for Plant Epigenetics, Shenzhen Key Laboratory of Marine Bioresource & Eco-environmental Science, Longhua Institute of Innovative Biotechnology, College of Life Sciences and Oceanography, Shenzhen University, Shenzhen, 518060, Guangdong Province, China; Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, College of Optoelectronic Engineering, Shenzhen University, Shenzhen, 518060, China.
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16
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Yang JS, Qian ZH, Shi T, Li ZZ, Chen JM. Chromosome-level genome assembly of the aquatic plant Nymphoides indica reveals transposable element bursts and NBS-LRR gene family expansion shedding light on its invasiveness. DNA Res 2022; 29:dsac022. [PMID: 35751614 PMCID: PMC9267246 DOI: 10.1093/dnares/dsac022] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2022] [Accepted: 06/24/2022] [Indexed: 11/19/2022] Open
Abstract
Nymphoides indica, an aquatic plant, is an invasive species that causes both ecological and economic damage in North America and elsewhere. However, the lack of genomic data of N. indica limits the in-depth analysis of this invasive species. Here, we report a chromosome-level genome assembly of nine pseudochromosomes of N. indica with a total size of ∼ 520 Mb. More than half of the N. indica genome consists of transposable elements (TEs), and a higher density of TEs around genes may play a significant role in response to an ever-changing environment by regulating the nearby gene. Additionally, our analysis revealed that N. indica only experienced a gamma (γ) whole-genome triplication event. Functional enrichment of the N. indica-specific and expanded gene families highlighted genes involved in the responses to hypoxia and plant-pathogen interactions, which may strengthen the ability to adapt to external challenges and improve ecological fitness. Furthermore, we identified 160 members of the nucleotide-binding site and leucine-rich repeat gene family, which may be linked to the defence response. Collectively, the high-quality N. indica genome reported here opens a novel avenue to understand the evolution and rapid invasion of Nymphoides spp.
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Affiliation(s)
- Jing-Shan Yang
- Key Laboratory of Aquatic Botany and Watershed Ecology, Wuhan Botanical Garden, Chinese Academy of Sciences, Wuhan 430074, China
- Center of Conservation Biology, Core Botanical Gardens, Chinese Academy of Sciences, Wuhan 430074, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Zhi-Hao Qian
- Key Laboratory of Aquatic Botany and Watershed Ecology, Wuhan Botanical Garden, Chinese Academy of Sciences, Wuhan 430074, China
- Center of Conservation Biology, Core Botanical Gardens, Chinese Academy of Sciences, Wuhan 430074, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Tao Shi
- Key Laboratory of Aquatic Botany and Watershed Ecology, Wuhan Botanical Garden, Chinese Academy of Sciences, Wuhan 430074, China
- Center of Conservation Biology, Core Botanical Gardens, Chinese Academy of Sciences, Wuhan 430074, China
| | - Zhi-Zhong Li
- Key Laboratory of Aquatic Botany and Watershed Ecology, Wuhan Botanical Garden, Chinese Academy of Sciences, Wuhan 430074, China
- Center of Conservation Biology, Core Botanical Gardens, Chinese Academy of Sciences, Wuhan 430074, China
| | - Jin-Ming Chen
- Key Laboratory of Aquatic Botany and Watershed Ecology, Wuhan Botanical Garden, Chinese Academy of Sciences, Wuhan 430074, China
- Center of Conservation Biology, Core Botanical Gardens, Chinese Academy of Sciences, Wuhan 430074, China
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17
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Genome-wide analyses of introgression between two sympatric Asian oak species. Nat Ecol Evol 2022; 6:924-935. [PMID: 35513577 DOI: 10.1038/s41559-022-01754-7] [Citation(s) in RCA: 17] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2021] [Accepted: 03/29/2022] [Indexed: 12/13/2022]
Abstract
Introgression can be an important source of new alleles for adaption under rapidly changing environments, perhaps even more important than standing variation. Though introgression has been extensively studied in many plants and animals, key questions on the underlying mechanisms of introgression still remain unanswered. In particular, we are yet to determine the genomic distribution of introgressed regions along the genome; whether the extent and patterns of introgression are influenced by ecological factors; and when and how introgression contributes to adaptation. Here, we generated high-quality genomic resources for two sympatric widespread Asian oak species, Quercus acutissima and Q. variabilis, sampled in multiple forests to study introgression between them. We show that introgressed regions are broadly distributed across the genome. Introgression was affected by genetic divergence between pairs of populations and by the similarity of the environments in which they live-populations occupying similar ecological sites tended to share the same introgressed regions. Introgressed genomic footprints of adaptation were preferentially located in regions with suppressed recombination rate. Introgression probably confers adaptation in these oak populations by introducing allelic variation in cis-regulatory elements, in particular through transposable element insertions, thereby altering the regulation of genes related to stress. Our results provide new avenues of research for uncovering mechanisms of adaptation due to hybridization in sympatric species.
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18
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Deneweth J, Van de Peer Y, Vermeirssen V. Nearby transposable elements impact plant stress gene regulatory networks: a meta-analysis in A. thaliana and S. lycopersicum. BMC Genomics 2022; 23:18. [PMID: 34983397 PMCID: PMC8725346 DOI: 10.1186/s12864-021-08215-8] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2021] [Accepted: 11/09/2021] [Indexed: 12/12/2022] Open
Abstract
BACKGROUND Transposable elements (TE) make up a large portion of many plant genomes and are playing innovative roles in genome evolution. Several TEs can contribute to gene regulation by influencing expression of nearby genes as stress-responsive regulatory motifs. To delineate TE-mediated plant stress regulatory networks, we took a 2-step computational approach consisting of identifying TEs in the proximity of stress-responsive genes, followed by searching for cis-regulatory motifs in these TE sequences and linking them to known regulatory factors. Through a systematic meta-analysis of RNA-seq expression profiles and genome annotations, we investigated the relation between the presence of TE superfamilies upstream, downstream or within introns of nearby genes and the differential expression of these genes in various stress conditions in the TE-poor Arabidopsis thaliana and the TE-rich Solanum lycopersicum. RESULTS We found that stress conditions frequently expressed genes having members of various TE superfamilies in their genomic proximity, such as SINE upon proteotoxic stress and Copia and Gypsy upon heat stress in A. thaliana, and EPRV and hAT upon infection, and Harbinger, LINE and Retrotransposon upon light stress in S. lycopersicum. These stress-specific gene-proximal TEs were mostly located within introns and more detected near upregulated than downregulated genes. Similar stress conditions were often related to the same TE superfamily. Additionally, we detected both novel and known motifs in the sequences of those TEs pointing to regulatory cooption of these TEs upon stress. Next, we constructed the regulatory network of TFs that act through binding these TEs to their target genes upon stress and discovered TE-mediated regulons targeted by TFs such as BRB/BPC, HD, HSF, GATA, NAC, DREB/CBF and MYB factors in Arabidopsis and AP2/ERF/B3, NAC, NF-Y, MYB, CXC and HD factors in tomato. CONCLUSIONS Overall, we map TE-mediated plant stress regulatory networks using numerous stress expression profile studies for two contrasting plant species to study the regulatory role TEs play in the response to stress. As TE-mediated gene regulation allows plants to adapt more rapidly to new environmental conditions, this study contributes to the future development of climate-resilient plants.
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Affiliation(s)
- Jan Deneweth
- Department of Plant Biotechnology and Bioinformatics, Ghent University, Ghent, Belgium
| | - Yves Van de Peer
- Department of Plant Biotechnology and Bioinformatics, Ghent University, Ghent, Belgium.,VIB Center for Plant Systems Biology, Ghent, Belgium.,Department of Biochemistry, Genetics and Microbiology, University of Pretoria, Pretoria, South Africa
| | - Vanessa Vermeirssen
- Department of Biomedical Molecular Biology, Ghent University, Ghent, Belgium. .,Department of Biomolecular Medicine, Ghent University, Ghent, Belgium. .,Lab for Computational Biology, Integromics and Gene Regulation (CBIGR), Cancer Research Institute Ghent (CRIG), Ghent, Belgium.
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19
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Kselíková V, Singh A, Bialevich V, Čížková M, Bišová K. Improving microalgae for biotechnology - From genetics to synthetic biology - Moving forward but not there yet. Biotechnol Adv 2021; 58:107885. [PMID: 34906670 DOI: 10.1016/j.biotechadv.2021.107885] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2021] [Revised: 11/28/2021] [Accepted: 12/07/2021] [Indexed: 12/28/2022]
Abstract
Microalgae are a diverse group of photosynthetic organisms that can be exploited for the production of different compounds, ranging from crude biomass and biofuels to high value-added biochemicals and synthetic proteins. Traditionally, algal biotechnology relies on bioprospecting to identify new highly productive strains and more recently, on forward genetics to further enhance productivity. However, it has become clear that further improvements in algal productivity for biotechnology is impossible without combining traditional tools with the arising molecular genetics toolkit. We review recent advantages in developing high throughput screening methods, preparing genome-wide mutant libraries, and establishing genome editing techniques. We discuss how algae can be improved in terms of photosynthetic efficiency, biofuel and high value-added compound production. Finally, we critically evaluate developments over recent years and explore future potential in the field.
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Affiliation(s)
- Veronika Kselíková
- Institute of Microbiology of the Czech Academy of Sciences, Centre Algatech, Laboratory of Cell Cycles of Algae, 379 81 Třeboň, Czech Republic; Faculty of Science, University of South Bohemia, 37005 České Budějovice, Czech Republic
| | - Anjali Singh
- Institute of Microbiology of the Czech Academy of Sciences, Centre Algatech, Laboratory of Cell Cycles of Algae, 379 81 Třeboň, Czech Republic
| | - Vitali Bialevich
- Institute of Microbiology of the Czech Academy of Sciences, Centre Algatech, Laboratory of Cell Cycles of Algae, 379 81 Třeboň, Czech Republic
| | - Mária Čížková
- Institute of Microbiology of the Czech Academy of Sciences, Centre Algatech, Laboratory of Cell Cycles of Algae, 379 81 Třeboň, Czech Republic
| | - Kateřina Bišová
- Institute of Microbiology of the Czech Academy of Sciences, Centre Algatech, Laboratory of Cell Cycles of Algae, 379 81 Třeboň, Czech Republic.
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20
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Regulation of retrotransposition in Arabidopsis. Biochem Soc Trans 2021; 49:2241-2251. [PMID: 34495315 DOI: 10.1042/bst20210337] [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] [Received: 06/29/2021] [Revised: 08/10/2021] [Accepted: 08/12/2021] [Indexed: 01/01/2023]
Abstract
Plant genomes are largely comprised of retrotransposons which can replicate through 'copy and paste' mechanisms. Long terminal repeat (LTR) retrotransposons are the major class of retrotransposons in plant species, and importantly they broadly affect the expression of nearby genes. Although most LTR retrotransposons are non-functional, active retrotranspositions have been reported in plant species or mutants under normal growth condition and environmental stresses. With the well-defined reference genome and numerous mutant alleles, Arabidopsis studies have significantly expanded our understanding of retrotransposon regulation. Active LTR retrotransposon loci produce virus-like particles to perform reverse transcription, and their complementary DNA can be inserted into new genomic loci. Due to the detrimental consequences of retrotransposition, plants like animals, have developed transcriptional and post-transcriptional silencing mechanisms. Recently several different genome-wide techniques have been developed to understand LTR retrotransposition in Arabidopsis and different plant species. Transposome, methylome, transcriptome, translatome and small RNA sequencing data have revealed how host silencing mechanisms can affect multiple steps of retrotransposition. These recent advances shed light on future mechanistic studies of retrotransposition as well as retrotransposon diversity.
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21
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The Dynamism of Transposon Methylation for Plant Development and Stress Adaptation. Int J Mol Sci 2021; 22:ijms222111387. [PMID: 34768817 PMCID: PMC8583499 DOI: 10.3390/ijms222111387] [Citation(s) in RCA: 29] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2021] [Revised: 10/13/2021] [Accepted: 10/19/2021] [Indexed: 02/06/2023] Open
Abstract
Plant development processes are regulated by epigenetic alterations that shape nuclear structure, gene expression, and phenotypic plasticity; these alterations can provide the plant with protection from environmental stresses. During plant growth and development, these processes play a significant role in regulating gene expression to remodel chromatin structure. These epigenetic alterations are mainly regulated by transposable elements (TEs) whose abundance in plant genomes results in their interaction with genomes. Thus, TEs are the main source of epigenetic changes and form a substantial part of the plant genome. Furthermore, TEs can be activated under stress conditions, and activated elements cause mutagenic effects and substantial genetic variability. This introduces novel gene functions and structural variation in the insertion sites and primarily contributes to epigenetic modifications. Altogether, these modifications indirectly or directly provide the ability to withstand environmental stresses. In recent years, many studies have shown that TE methylation plays a major role in the evolution of the plant genome through epigenetic process that regulate gene imprinting, thereby upholding genome stability. The induced genetic rearrangements and insertions of mobile genetic elements in regions of active euchromatin contribute to genome alteration, leading to genomic stress. These TE-mediated epigenetic modifications lead to phenotypic diversity, genetic variation, and environmental stress tolerance. Thus, TE methylation is essential for plant evolution and stress adaptation, and TEs hold a relevant military position in the plant genome. High-throughput techniques have greatly advanced the understanding of TE-mediated gene expression and its associations with genome methylation and suggest that controlled mobilization of TEs could be used for crop breeding. However, development application in this area has been limited, and an integrated view of TE function and subsequent processes is lacking. In this review, we explore the enormous diversity and likely functions of the TE repertoire in adaptive evolution and discuss some recent examples of how TEs impact gene expression in plant development and stress adaptation.
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22
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Sun Y, Liu C, Liu Z, Zhao T, Jiang J, Li J, Xu X, Yang H. Genome-Wide Identification, Characterization and Expression Analysis of the JAZ Gene Family in Resistance to Gray Leaf Spots in Tomato. Int J Mol Sci 2021; 22:ijms22189974. [PMID: 34576142 PMCID: PMC8469637 DOI: 10.3390/ijms22189974] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2021] [Revised: 09/07/2021] [Accepted: 09/14/2021] [Indexed: 12/27/2022] Open
Abstract
The plant disease resistance system involves a very complex regulatory network in which jasmonates play a key role in response to external biotic or abiotic stresses. As inhibitors of the jasmonic acid (JA) signaling pathway, JASMONATE ZIM domain (JAZ) proteins have been identified in many plant species, and their functions are gradually being clarified. In this study, 26 JAZ genes were identified in tomato. The physical and chemical properties, predicted subcellular localization, gene structure, cis-acting elements, and interspecies collinearity of 26 SlJAZ genes were subsequently analyzed. RNA-seq data combined with qRT-PCR analysis data showed that the expression of most SlJAZ genes were induced in response to Stemphylium lycopersici, methyl jasmonate (MeJA) and salicylic acid (SA). Tobacco rattle virus RNA2-based VIGS vector (TRV2)-SlJAZ25 plants were more resistant to tomato gray leaf spots than TRV2-00 plants. Therefore, we speculated that SlJAZ25 played a negative regulatory role in tomato resistance to gray leaf spots. Based on combining the results of previous studies and those of our experiments, we speculated that SlJAZ25 might be closely related to JA and SA hormone regulation. SlJAZ25 interacted with SlJAR1, SlCOI1, SlMYC2, and other resistance-related genes to form a regulatory network, and these genes played an important role in the regulation of tomato gray leaf spots. The subcellular localization results showed that the SlJAZ25 gene was located in the nucleus. Overall, this study is the first to identify and analyze JAZ family genes in tomato via bioinformatics approaches, clarifying the regulatory role of SlJAZ25 genes in tomato resistance to gray leaf spots and providing new ideas for improving plant disease resistance.
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Affiliation(s)
| | | | | | | | | | | | - Xiangyang Xu
- Correspondence: (X.X.); (H.Y.); Tel.: +86-0451-55190748 (H.Y.)
| | - Huanhuan Yang
- Correspondence: (X.X.); (H.Y.); Tel.: +86-0451-55190748 (H.Y.)
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23
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Park M, Williams DS, Turpin ZM, Wiggins ZJ, Tsolova VM, Onokpise OU, Bass HW. Differential nuclease sensitivity profiling uncovers a drought responsive change in maize leaf chromatin structure for two large retrotransposon derivatives, Uloh and Vegu. PLANT DIRECT 2021; 5:e337. [PMID: 34430792 PMCID: PMC8365550 DOI: 10.1002/pld3.337] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/12/2021] [Revised: 05/19/2021] [Accepted: 06/21/2021] [Indexed: 06/13/2023]
Abstract
Plant chromatin dynamics are generally recognized as playing a role in the genomic response to environmental stress. Although stress-induced transcriptional activities of LTR-retrotransposons have been reported, whether the stress response can be detected at the level of chromatin structure for LTR-retrotransposons is largely unknown. Using differential nuclease sensitivity profiling, we identified that two out of 29 maize LTR-retrotransposon families change their chromatin structure in response to drought stress in leaf tissue. The two LTR-retrotransposon families, uloh and vegu, are classified as nonautonomous LTR-retrotransposons. Differently from other families, the chromatin structure of these two families shifted from more open in normal conditions to more closed following drought stress. Although uloh and vegu lack sequence similarity, most of them shared an intriguing feature of having a new and uncharacterized insertion of a DNA sequence near one side of an LTR. In the uloh family, nine members with a strong drought response also exhibited a drought-induced reduction of published H3K4me3 histone modification in the inserted DNA region, implicating this modification in the chromatin structural changes. Our results provide new insight into how LTR-retrotransposons can alter their chromatin structure following stress response in plants.
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Affiliation(s)
- Minkyu Park
- Center for Viticulture and Small Fruit ResearchFlorida A&M UniversityTallahasseeFloridaUSA
| | - Delvin S. Williams
- College of Agriculture and Food SciencesFlorida A&M UniversityTallahasseeFloridaUSA
| | - Zachary M. Turpin
- Department of Biological ScienceFlorida State UniversityTallahasseeFloridaUSA
| | | | - Violeta M. Tsolova
- Center for Viticulture and Small Fruit ResearchFlorida A&M UniversityTallahasseeFloridaUSA
| | | | - Hank W. Bass
- Department of Biological ScienceFlorida State UniversityTallahasseeFloridaUSA
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24
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Benoit M, Drost HG. A Predictive Approach to Infer the Activity and Natural Variation of Retrotransposon Families in Plants. Methods Mol Biol 2021; 2250:1-14. [PMID: 33900588 DOI: 10.1007/978-1-0716-1134-0_1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Plant genomes harbor a particularly rich landscape of repetitive sequences. Transposable elements (TEs) represent a major fraction of this diversity and are intimately linked with plasticity and evolution of genomes across the tree of life (Fedoroff, Science 338:758-767, 2012). Amplification of Long Terminal Repeats (LTR) retrotransposons have shaped the genomic landscape by reshuffling genomic regions, altering gene expression, and providing new regulatory sequences, some of which have been instrumental for crop domestication and breeding (Lisch, Nat Rev Genet 14:49-61, 2013; Vitte et al., Brief Funct Genomics 13:276-295, 2014). While many retrotransposon families are still active within plant genomes, the repetitive nature of retrotransposons has hindered accurate annotation and kingdom-wide predictive assessment of their activity and molecular evolution. While it is natural for the first approach towards a genome annotation to characterize all regions of the genome and associate them with known structures such as particular genes, transposable elements, or other types of non-coding regions, such efforts can result in a large proportion of false-positive annotations when seeking for active loci. To overcome this issue, the next round of annotation efforts needs to include functional annotations based on rigorously defined sequence structures and protein domain compositions. In the context of retrotransposons, such a functional annotation can enable efforts to mobilize particular retrotransposon families in species living today and harness their mutagenic potency for crop improvement (Paszkowski, Curr Opin Biotechnol 32:200-206, 2015). For this purpose, we present a predictive analytical approach to infer the activity and natural variation of retrotransposon families in plants. This is achieved by applying a combination of software and molecular biology tools we developed for functional annotation, activity monitoring, and the assessment of the population structure of particular retrotransposon families in multiple plant species.
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Affiliation(s)
- Matthias Benoit
- Howard Hughes Medical Institute, Cold Spring Harbor Laboratory, Cold Spring Harbor, NY, USA
| | - Hajk-Georg Drost
- Computational Biology Group, Department of Molecular Biology, Max Planck Institute for Developmental Biology, Tübingen, Germany.
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25
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Ayukawa Y, Asai S, Gan P, Tsushima A, Ichihashi Y, Shibata A, Komatsu K, Houterman PM, Rep M, Shirasu K, Arie T. A pair of effectors encoded on a conditionally dispensable chromosome of Fusarium oxysporum suppress host-specific immunity. Commun Biol 2021; 4:707. [PMID: 34108627 PMCID: PMC8190069 DOI: 10.1038/s42003-021-02245-4] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2020] [Accepted: 05/18/2021] [Indexed: 11/29/2022] Open
Abstract
Many plant pathogenic fungi contain conditionally dispensable (CD) chromosomes that are associated with virulence, but not growth in vitro. Virulence-associated CD chromosomes carry genes encoding effectors and/or host-specific toxin biosynthesis enzymes that may contribute to determining host specificity. Fusarium oxysporum causes devastating diseases of more than 100 plant species. Among a large number of host-specific forms, F. oxysporum f. sp. conglutinans (Focn) can infect Brassicaceae plants including Arabidopsis (Arabidopsis thaliana) and cabbage. Here we show that Focn has multiple CD chromosomes. We identified specific CD chromosomes that are required for virulence on Arabidopsis, cabbage, or both, and describe a pair of effectors encoded on one of the CD chromosomes that is required for suppression of Arabidopsis-specific phytoalexin-based immunity. The effector pair is highly conserved in F. oxysporum isolates capable of infecting Arabidopsis, but not of other plants. This study provides insight into how host specificity of F. oxysporum may be determined by a pair of effector genes on a transmissible CD chromosome. Yu Ayukawa, Shuta Asai, et al. report the genome sequence of a Fusarium oxysporum isolate and demonstrate that it contains different conditionally dispensable chromosomes which are important to confer virulence on specific hosts, like Arabidopsis thaliana or cabbage. Altogether, these results provide further insight into the mechanisms underlying F. oxysporum pathogenicity.
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Affiliation(s)
- Yu Ayukawa
- Center for Sustainable Resource Science, RIKEN, Yokohama, Kanagawa, Japan.,Laboratory of Plant Pathology, Graduate School of Agriculture, Tokyo University of Agriculture and Technology (TUAT), Fuchu, Tokyo, Japan
| | - Shuta Asai
- Center for Sustainable Resource Science, RIKEN, Yokohama, Kanagawa, Japan. .,PRESTO, Japan Science and Technology Agency, Kawaguchi, Saitama, Japan.
| | - Pamela Gan
- Center for Sustainable Resource Science, RIKEN, Yokohama, Kanagawa, Japan
| | - Ayako Tsushima
- Center for Sustainable Resource Science, RIKEN, Yokohama, Kanagawa, Japan.,John Innes Centre, Norwich, UK
| | - Yasunori Ichihashi
- Center for Sustainable Resource Science, RIKEN, Yokohama, Kanagawa, Japan.,RIKEN BioResource Research Center, Tsukuba, Ibaraki, Japan
| | - Arisa Shibata
- Center for Sustainable Resource Science, RIKEN, Yokohama, Kanagawa, Japan
| | - Ken Komatsu
- Laboratory of Plant Pathology, Graduate School of Agriculture, Tokyo University of Agriculture and Technology (TUAT), Fuchu, Tokyo, Japan
| | - Petra M Houterman
- Molecular Plant Pathology, Swammerdam Institute for Life Sciences, University of Amsterdam, Amsterdam, The Netherlands
| | - Martijn Rep
- Molecular Plant Pathology, Swammerdam Institute for Life Sciences, University of Amsterdam, Amsterdam, The Netherlands
| | - Ken Shirasu
- Center for Sustainable Resource Science, RIKEN, Yokohama, Kanagawa, Japan
| | - Tsutomu Arie
- Laboratory of Plant Pathology, Graduate School of Agriculture, Tokyo University of Agriculture and Technology (TUAT), Fuchu, Tokyo, Japan.
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26
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Liang Z, Anderson SN, Noshay JM, Crisp PA, Enders TA, Springer NM. Genetic and epigenetic variation in transposable element expression responses to abiotic stress in maize. PLANT PHYSIOLOGY 2021; 186:420-433. [PMID: 33591319 PMCID: PMC8154091 DOI: 10.1093/plphys/kiab073] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/30/2020] [Accepted: 02/05/2021] [Indexed: 06/12/2023]
Abstract
Transposable elements (TEs) pervade most eukaryotic genomes. The repetitive nature of TEs complicates the analysis of their expression. Evaluation of the expression of both TE families (using unique and multi-mapping reads) and specific elements (using uniquely mapping reads) in leaf tissue of three maize (Zea mays) inbred lines subjected to heat or cold stress reveals no evidence for genome-wide activation of TEs; however, some specific TE families generate transcripts only in stress conditions. There is substantial variation for which TE families exhibit stress-responsive expression in the different genotypes. In order to understand the factors that drive expression of TEs, we focused on a subset of families in which we could monitor expression of individual elements. The stress-responsive activation of a TE family can often be attributed to a small number of elements in the family that contains regions lacking DNA methylation. Comparisons of the expression of TEs in different genotypes revealed both genetic and epigenetic variation. Many of the specific TEs that are activated in stress in one inbred are not present in the other inbred, explaining the lack of activation. Among the elements that are shared in both genomes but only expressed in one genotype, we found that many exhibit differences in DNA methylation such that the genotype without expression is fully methylated. This study provides insights into the regulation of expression of TEs in normal and stress conditions and highlights the role of chromatin variation between elements in a family or between genotypes for contributing to expression variation. The highly repetitive nature of many TEs complicates the analysis of their expression. Although most TEs are not expressed, some exhibits expression in certain tissues or conditions. We monitored the expression of both TE families (using unique and multi-mapping reads) and specific elements (using uniquely mapping reads) in leaf tissue of three maize (Zea mays) inbred lines subjected to heat or cold stress. While genome-wide activation of TEs did not occur, some TE families generated transcripts only in stress conditions with variation by genotype. To better understand the factors that drive expression of TEs, we focused on a subset of families in which we could monitor expression of individual elements. In most cases, stress-responsive activation of a TE family was attributed to a small number of elements in the family. The elements that contained small regions lacking DNA methylation regions showed enriched expression while fully methylated elements were rarely expressed in control or stress conditions. The cause of varied expression in the different genotypes was due to both genetic and epigenetic variation. Many specific TEs activated by stress in one inbred were not present in the other inbred. Among the elements shared in both genomes, full methylation inhibited expression in one of the genotypes. This study provides insights into the regulation of TE expression in normal and stress conditions and highlights the role of chromatin variation between elements in a family or between genotypes for contributing to expression.
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Affiliation(s)
- Zhikai Liang
- Department of Plant and Microbial Biology, University of Minnesota, Saint Paul, Minnesota, USA
| | - Sarah N Anderson
- Department of Genetics, Development and Cell Biology, Iowa State University, Ames, Iowa, USA
| | - Jaclyn M Noshay
- Department of Plant and Microbial Biology, University of Minnesota, Saint Paul, Minnesota, USA
| | - Peter A Crisp
- School of Agriculture and Food Sciences, The University of Queensland, Brisbane, Queensland, Australia
| | - Tara A Enders
- Department of Biology, Hofstra University, Hempstead, New York, USA
| | - Nathan M Springer
- Department of Plant and Microbial Biology, University of Minnesota, Saint Paul, Minnesota, USA
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27
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Gan P, Hiroyama R, Tsushima A, Masuda S, Shibata A, Ueno A, Kumakura N, Narusaka M, Hoat TX, Narusaka Y, Takano Y, Shirasu K. Telomeres and a repeat-rich chromosome encode effector gene clusters in plant pathogenic Colletotrichum fungi. Environ Microbiol 2021; 23:6004-6018. [PMID: 33780109 DOI: 10.1111/1462-2920.15490] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2020] [Accepted: 03/25/2021] [Indexed: 12/13/2022]
Abstract
Members of the Colletotrichum gloeosporioides species complex are causal agents of anthracnose in many commercially important plants. Closely related strains have different levels of pathogenicity on hosts despite their close phylogenetic relationship. To gain insight into the genetics underlying these differences, we generated and annotated whole-genome assemblies of multiple isolates of C. fructicola (Cf) and C. siamense (Cs), as well as three previously unsequenced species, C. aenigma (Ca), C. tropicale and C. viniferum with different pathogenicity on strawberry. Based on comparative genomics, we identified accessory regions with a high degree of conservation in strawberry-pathogenic Cf, Cs and Ca strains. These regions encode homologs of pathogenicity-related genes known as effectors, organized in syntenic gene clusters, with copy number variations in different strains of Cf, Cs and Ca. Analysis of highly contiguous assemblies of Cf, Cs and Ca revealed the association of related accessory effector gene clusters with telomeres and repeat-rich chromosomes and provided evidence of exchange between these two genomic compartments. In addition, expression analysis indicated that orthologues in syntenic gene clusters showed a tendency for correlated gene expression during infection. These data provide insight into mechanisms by which Colletotrichum genomes evolve, acquire and organize effectors.
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Affiliation(s)
- Pamela Gan
- RIKEN Center for Sustainable Resource Sciences, Yokohama, Kanagawa, Japan
| | - Ryoko Hiroyama
- RIKEN Center for Sustainable Resource Sciences, Yokohama, Kanagawa, Japan
| | - Ayako Tsushima
- RIKEN Center for Sustainable Resource Sciences, Yokohama, Kanagawa, Japan.,Graduate School of Science, The University of Tokyo, Bunkyo, Tokyo, Japan
| | - Sachiko Masuda
- RIKEN Center for Sustainable Resource Sciences, Yokohama, Kanagawa, Japan
| | - Arisa Shibata
- RIKEN Center for Sustainable Resource Sciences, Yokohama, Kanagawa, Japan
| | - Akiko Ueno
- RIKEN Center for Sustainable Resource Sciences, Yokohama, Kanagawa, Japan
| | - Naoyoshi Kumakura
- RIKEN Center for Sustainable Resource Sciences, Yokohama, Kanagawa, Japan
| | - Mari Narusaka
- Research Institute for Biological Sciences, Okayama Prefectural Technology Center for Agriculture, Forestry, and Fisheries, Okayama, Japan
| | | | - Yoshihiro Narusaka
- Research Institute for Biological Sciences, Okayama Prefectural Technology Center for Agriculture, Forestry, and Fisheries, Okayama, Japan
| | | | - Ken Shirasu
- RIKEN Center for Sustainable Resource Sciences, Yokohama, Kanagawa, Japan.,Graduate School of Science, The University of Tokyo, Bunkyo, Tokyo, Japan
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28
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Mobility connects: transposable elements wire new transcriptional networks by transferring transcription factor binding motifs. Biochem Soc Trans 2021; 48:1005-1017. [PMID: 32573687 PMCID: PMC7329337 DOI: 10.1042/bst20190937] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2020] [Revised: 06/01/2020] [Accepted: 06/03/2020] [Indexed: 12/28/2022]
Abstract
Transposable elements (TEs) constitute major fractions of plant genomes. Their potential to be mobile provides them with the capacity to cause major genome rearrangements. Those effects are potentially deleterious and enforced the evolution of epigenetic suppressive mechanisms controlling TE activity. However, beyond their deleterious effects, TE insertions can be neutral or even advantageous for the host, leading to long-term retention of TEs in the host genome. Indeed, TEs are increasingly recognized as major drivers of evolutionary novelties by regulating the expression of nearby genes. TEs frequently contain binding motifs for transcription factors and capture binding motifs during transposition, which they spread through the genome by transposition. Thus, TEs drive the evolution and diversification of gene regulatory networks by recruiting lineage-specific targets under the regulatory control of specific transcription factors. This process can explain the rapid and repeated evolution of developmental novelties, such as C4 photosynthesis and a wide spectrum of stress responses in plants. It also underpins the convergent evolution of embryo nourishing tissues, the placenta in mammals and the endosperm in flowering plants. Furthermore, the gene regulatory network underlying flower development has also been largely reshaped by TE-mediated recruitment of regulatory elements; some of them being preserved across long evolutionary timescales. In this review, we highlight the potential role of TEs as evolutionary toolkits in plants by showcasing examples of TE-mediated evolutionary novelties.
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29
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Srikant T, Drost HG. How Stress Facilitates Phenotypic Innovation Through Epigenetic Diversity. FRONTIERS IN PLANT SCIENCE 2021; 11:606800. [PMID: 33519857 PMCID: PMC7843580 DOI: 10.3389/fpls.2020.606800] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/15/2020] [Accepted: 12/16/2020] [Indexed: 05/14/2023]
Abstract
Climate adaptation through phenotypic innovation will become the main challenge for plants during global warming. Plants exhibit a plethora of mechanisms to achieve environmental and developmental plasticity by inducing dynamic alterations of gene regulation and by maximizing natural variation through large population sizes. While successful over long evolutionary time scales, most of these mechanisms lack the short-term adaptive responsiveness that global warming will require. Here, we review our current understanding of the epigenetic regulation of plant genomes, with a focus on stress-response mechanisms and transgenerational inheritance. Field and laboratory-scale experiments on plants exposed to stress have revealed a multitude of temporally controlled, mechanistic strategies integrating both genetic and epigenetic changes on the genome level. We analyze inter- and intra-species population diversity to discuss how methylome differences and transposon activation can be harnessed for short-term adaptive efforts to shape co-evolving traits in response to qualitatively new climate conditions and environmental stress.
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Affiliation(s)
| | - Hajk-Georg Drost
- Department of Molecular Biology, Max Planck Institute for Developmental Biology, Tübingen, Germany
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30
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DNA methylation mutants in Physcomitrella patens elucidate individual roles of CG and non-CG methylation in genome regulation. Proc Natl Acad Sci U S A 2020; 117:33700-33710. [PMID: 33376225 DOI: 10.1073/pnas.2011361117] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Cytosine (DNA) methylation in plants regulates the expression of genes and transposons. While methylation in plant genomes occurs at CG, CHG, and CHH sequence contexts, the comparative roles of the individual methylation contexts remain elusive. Here, we present Physcomitrella patens as the second plant system, besides Arabidopsis thaliana, with viable mutants with an essentially complete loss of methylation in the CG and non-CG contexts. In contrast to A. thaliana, P. patens has more robust CHH methylation, similar CG and CHG methylation levels, and minimal cross-talk between CG and non-CG methylation, making it possible to study context-specific effects independently. Our data found CHH methylation to act in redundancy with symmetric methylation in silencing transposons and to regulate the expression of CG/CHG-depleted transposons. Specific elimination of CG methylation did not dysregulate transposons or genes. In contrast, exclusive removal of non-CG methylation massively up-regulated transposons and genes. In addition, comparing two exclusively but equally CG- or CHG-methylated genomes, we show that CHG methylation acts as a greater transcriptional regulator than CG methylation. These results disentangle the transcriptional roles of CG and non-CG, as well as symmetric and asymmetric methylation in a plant genome, and point to the crucial role of non-CG methylation in genome regulation.
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31
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Liu J, He Z. Small DNA Methylation, Big Player in Plant Abiotic Stress Responses and Memory. FRONTIERS IN PLANT SCIENCE 2020; 11:595603. [PMID: 33362826 PMCID: PMC7758401 DOI: 10.3389/fpls.2020.595603] [Citation(s) in RCA: 51] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/17/2020] [Accepted: 11/18/2020] [Indexed: 05/12/2023]
Abstract
DNA methylation is a conserved epigenetic mark that plays important roles in maintaining genome stability and regulating gene expression. As sessile organisms, plants have evolved sophisticated regulatory systems to endure or respond to diverse adverse abiotic environmental challenges, i.e., abiotic stresses, such as extreme temperatures (cold and heat), drought and salinity. Plant stress responses are often accompanied by changes in chromatin modifications at diverse responsive loci, such as 5-methylcytosine (5mC) and N 6-methyladenine (6mA) DNA methylation. Some abiotic stress responses are memorized for several hours or days through mitotic cell divisions and quickly reset to baseline levels after normal conditions are restored, which is referred to as somatic memory. In some cases, stress-induced chromatin marks are meiotically heritable and can impart the memory of stress exposure from parent plants to at least the next stress-free offspring generation through the mechanisms of transgenerational epigenetic inheritance, which may offer the descendants the potential to be adaptive for better fitness. In this review, we briefly summarize recent achievements regarding the establishment, maintenance and reset of DNA methylation, and highlight the diverse roles of DNA methylation in plant responses to abiotic stresses. Further, we discuss the potential role of DNA methylation in abiotic stress-induced somatic memory and transgenerational inheritance. Future research directions are proposed to develop stress-tolerant engineered crops to reduce the negative effects of abiotic stresses.
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Affiliation(s)
- Junzhong Liu
- State Key Laboratory of Conservation and Utilization of Bio-Resources in Yunnan and Center for Life Sciences, School of Life Sciences, Yunnan University, Kunming, China
| | - Zuhua He
- National Key Laboratory of Plant Molecular Genetics, CAS Center for Excellence in Molecular Plant Sciences, Shanghai Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Shanghai, China
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32
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Wu L, Williams JS, Sun L, Kao TH. Sequence analysis of the Petunia inflata S-locus region containing 17 S-Locus F-Box genes and the S-RNase gene involved in self-incompatibility. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2020; 104:1348-1368. [PMID: 33048387 DOI: 10.1111/tpj.15005] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/09/2020] [Revised: 08/28/2020] [Accepted: 09/01/2020] [Indexed: 06/11/2023]
Abstract
Self-incompatibility in Petunia is controlled by the polymorphic S-locus, which contains S-RNase encoding the pistil determinant and 16-20 S-locus F-box (SLF) genes collectively encoding the pollen determinant. Here we sequenced and assembled approximately 3.1 Mb of the S2 -haplotype of the S-locus in Petunia inflata using bacterial artificial chromosome clones collectively containing all 17 SLF genes, SLFLike1, and S-RNase. Two SLF pseudogenes and 28 potential protein-coding genes were identified, 20 of which were also found at the S-loci of both the S6a -haplotype of P. inflata and the SN -haplotype of self-compatible Petunia axillaris, but not in the S-locus remnants of self-compatible potato (Solanum tuberosum) and tomato (Solanum lycopersicum). Comparative analyses of S-locus sequences of these three S-haplotypes revealed potential genetic exchange in the flanking regions of SLF genes, resulting in highly similar flanking regions between different types of SLF and between alleles of the same type of SLF of different S-haplotypes. The high degree of sequence similarity in the flanking regions could often be explained by the presence of similar long terminal repeat retroelements, which were enriched at the S-loci of all three S-haplotypes and in the flanking regions of all S-locus genes examined. We also found evidence of the association of transposable elements with SLF pseudogenes. Based on the hypothesis that SLF genes were derived by retrotransposition, we identified 10 F-box genes as putative SLF parent genes. Our results shed light on the importance of non-coding sequences in the evolution of the S-locus, and on possible evolutionary mechanisms of generation, proliferation, and deletion of SLF genes.
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Affiliation(s)
- Lihua Wu
- Intercollege Graduate Degree Program in Plant Biology, The Pennsylvania State University, University Park, Pennsylvania, 16802, USA
| | - Justin S Williams
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania, 16802, USA
| | - Linhan Sun
- Intercollege Graduate Degree Program in Plant Biology, The Pennsylvania State University, University Park, Pennsylvania, 16802, USA
| | - Teh-Hui Kao
- Intercollege Graduate Degree Program in Plant Biology, The Pennsylvania State University, University Park, Pennsylvania, 16802, USA
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania, 16802, USA
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33
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Rymen B, Ferrafiat L, Blevins T. Non-coding RNA polymerases that silence transposable elements and reprogram gene expression in plants. Transcription 2020; 11:172-191. [PMID: 33180661 PMCID: PMC7714444 DOI: 10.1080/21541264.2020.1825906] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Multisubunit RNA polymerase (Pol) complexes are the core machinery for gene expression in eukaryotes. The enzymes Pol I, Pol II and Pol III transcribe distinct subsets of nuclear genes. This family of nuclear RNA polymerases expanded in terrestrial plants by the duplication of Pol II subunit genes. Two Pol II-related enzymes, Pol IV and Pol V, are highly specialized in the production of regulatory, non-coding RNAs. Pol IV and Pol V are the central players of RNA-directed DNA methylation (RdDM), an RNA interference pathway that represses transposable elements (TEs) and selected genes. Genetic and biochemical analyses of Pol IV/V subunits are now revealing how these enzymes evolved from ancestral Pol II to sustain non-coding RNA biogenesis in silent chromatin. Intriguingly, Pol IV-RdDM regulates genes that influence flowering time, reproductive development, stress responses and plant–pathogen interactions. Pol IV target genes vary among closely related taxa, indicating that these regulatory circuits are often species-specific. Data from crops like maize, rice, tomato and Brassicarapa suggest that dynamic repositioning of TEs, accompanied by Pol IV targeting to TE-proximal genes, leads to the reprogramming of plant gene expression over short evolutionary timescales.
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Affiliation(s)
- Bart Rymen
- Institut de biologie moléculaire des plantes, Université de Strasbourg , Strasbourg, France
| | - Laura Ferrafiat
- Institut de biologie moléculaire des plantes, Université de Strasbourg , Strasbourg, France
| | - Todd Blevins
- Institut de biologie moléculaire des plantes, Université de Strasbourg , Strasbourg, France
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Kundariya H, Yang X, Morton K, Sanchez R, Axtell MJ, Hutton SF, Fromm M, Mackenzie SA. MSH1-induced heritable enhanced growth vigor through grafting is associated with the RdDM pathway in plants. Nat Commun 2020; 11:5343. [PMID: 33093443 PMCID: PMC7582163 DOI: 10.1038/s41467-020-19140-x] [Citation(s) in RCA: 36] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2020] [Accepted: 09/24/2020] [Indexed: 12/20/2022] Open
Abstract
Plants transmit signals long distances, as evidenced in grafting experiments that create distinct rootstock-scion junctions. Noncoding small RNA is a signaling molecule that is graft transmissible, participating in RNA-directed DNA methylation; but the meiotic transmissibility of graft-mediated epigenetic changes remains unclear. Here, we exploit the MSH1 system in Arabidopsis and tomato to introduce rootstock epigenetic variation to grafting experiments. Introducing mutations dcl2, dcl3 and dcl4 to the msh1 rootstock disrupts siRNA production and reveals RdDM targets of methylation repatterning. Progeny from grafting experiments show enhanced growth vigor relative to controls. This heritable enhancement-through-grafting phenotype is RdDM-dependent, involving 1380 differentially methylated genes, many within auxin-related gene pathways. Growth vigor is associated with robust root growth of msh1 graft progeny, a phenotype associated with auxin transport based on inhibitor assays. Large-scale field experiments show msh1 grafting effects on tomato plant performance, heritable over five generations, demonstrating the agricultural potential of epigenetic variation. The meiotic transmissibility and progeny phenotypic influence of graft-mediated epigenetic changes remain unclear. Here, the authors use the msh1 mutant in the rootstock to trigger heritable enhanced growth vigor in Arabidopsis and tomato, and show it is associated with the RNA-directed DNA methylation pathway.
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Affiliation(s)
- Hardik Kundariya
- Department of Agronomy and Horticulture, University of Nebraska, Lincoln, NE, USA.,Department of Biology, The Pennsylvania State University, University Park, PA, USA
| | - Xiaodong Yang
- Department of Biology, The Pennsylvania State University, University Park, PA, USA
| | - Kyla Morton
- EpiCrop Technologies, Inc., Lincoln, NE, USA
| | - Robersy Sanchez
- Department of Biology, The Pennsylvania State University, University Park, PA, USA
| | - Michael J Axtell
- Department of Biology, The Pennsylvania State University, University Park, PA, USA
| | - Samuel F Hutton
- Gulf Coast Research and Education Center, IFAS, University of Florida, Wimauma, FL, USA
| | | | - Sally A Mackenzie
- Departments of Biology and Plant Science, The Pennsylvania State University, University Park, PA, USA.
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Host Gene Regulation by Transposable Elements: The New, the Old and the Ugly. Viruses 2020; 12:v12101089. [PMID: 32993145 PMCID: PMC7650545 DOI: 10.3390/v12101089] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2020] [Revised: 09/14/2020] [Accepted: 09/23/2020] [Indexed: 12/12/2022] Open
Abstract
The human genome has been under selective pressure to evolve in response to emerging pathogens and other environmental challenges. Genome evolution includes the acquisition of new genes or new isoforms of genes and changes to gene expression patterns. One source of genome innovation is from transposable elements (TEs), which carry their own promoters, enhancers and open reading frames and can act as ‘controlling elements’ for our own genes. TEs include LINE-1 elements, which can retrotranspose intracellularly and endogenous retroviruses (ERVs) that represent remnants of past retroviral germline infections. Although once pathogens, ERVs also represent an enticing source of incoming genetic material that the host can then repurpose. ERVs and other TEs have coevolved with host genes for millions of years, which has allowed them to become embedded within essential gene expression programmes. Intriguingly, these host genes are often subject to the same epigenetic control mechanisms that evolved to combat the TEs that now regulate them. Here, we illustrate the breadth of host gene regulation through TEs by focusing on examples of young (The New), ancient (The Old), and disease-causing (The Ugly) TE integrants.
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Varotto S, Tani E, Abraham E, Krugman T, Kapazoglou A, Melzer R, Radanović A, Miladinović D. Epigenetics: possible applications in climate-smart crop breeding. JOURNAL OF EXPERIMENTAL BOTANY 2020; 71:5223-5236. [PMID: 32279074 PMCID: PMC7475248 DOI: 10.1093/jxb/eraa188] [Citation(s) in RCA: 54] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/31/2019] [Accepted: 04/09/2020] [Indexed: 05/23/2023]
Abstract
To better adapt transiently or lastingly to stimuli from the surrounding environment, the chromatin states in plant cells vary to allow the cells to fine-tune their transcriptional profiles. Modifications of chromatin states involve a wide range of post-transcriptional histone modifications, histone variants, DNA methylation, and activity of non-coding RNAs, which can epigenetically determine specific transcriptional outputs. Recent advances in the area of '-omics' of major crops have facilitated identification of epigenetic marks and their effect on plant response to environmental stresses. As most epigenetic mechanisms are known from studies in model plants, we summarize in this review recent epigenetic studies that may be important for improvement of crop adaptation and resilience to environmental changes, ultimately leading to the generation of stable climate-smart crops. This has paved the way for exploitation of epigenetic variation in crop breeding.
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Affiliation(s)
- Serena Varotto
- Department of Agronomy, Food, Natural Resources, Animals, and the Environment, University of Padova, Agripolis, Viale dell’Università, Padova, Italy
| | - Eleni Tani
- Department of Crop Science, Laboratory of Plant Breeding and Biometry, Agricultural University of Athens, Athens, Greece
| | - Eleni Abraham
- Laboratory of Range Science, School of Agriculture, Forestry and Natural Environment, Aristotle University of Thessaloniki, Thessaloniki, Greece
| | - Tamar Krugman
- Institute of Evolution, University of Haifa, Haifa, Israel
| | - Aliki Kapazoglou
- Institute of Olive Tree, Subtropical Crops and Viticulture (IOSV), Department of Vitis, Hellenic Agricultural Organization-Demeter (HAO-Demeter), Lykovrysi, Greece
| | - Rainer Melzer
- School of Biology and Environmental Science and Earth Institute, University College Dublin, Belfield, Dublin, Ireland
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Wang Z, Baulcombe DC. Transposon age and non-CG methylation. Nat Commun 2020; 11:1221. [PMID: 32144266 PMCID: PMC7060349 DOI: 10.1038/s41467-020-14995-6] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2020] [Accepted: 02/11/2020] [Indexed: 11/09/2022] Open
Abstract
Silencing of transposable elements (TEs) is established by small RNA-directed DNA methylation (RdDM). Maintenance of silencing is then based on a combination of RdDM and RNA-independent mechanisms involving DNA methyltransferase MET1 and chromodomain DNA methyltransferases (CMTs). Involvement of RdDM, according to this model should decrease with TE age but here we show a different pattern in tomato and Arabidopsis. In these species the CMTs silence long terminal repeat (LTR) transposons in the distal chromatin that are younger than those affected by RdDM. To account for these findings we propose that, after establishment of primary RdDM as in the original model, there is an RNA-independent maintenance phase involving CMTs followed by secondary RdDM. This progression of epigenetic silencing in the gene-rich distal chromatin is likely to influence the transcriptome either in cis or in trans depending on whether the mechanisms are RNA-dependent or -independent. RNA-directed DNA methylation (RdDM) is thought to silence newly inserted transposable elements (TEs) with RNA-independent mechanisms becoming more prominent as TEs age. Here, the authors show that RdDM continues to silence the oldest intact distal TEs in tomato and Arabidopsis suggesting a second, later phase of RdDM.
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Affiliation(s)
- Zhengming Wang
- Department of Plant Sciences, University of Cambridge, Cambridge, CB2 3EA, UK
| | - David C Baulcombe
- Department of Plant Sciences, University of Cambridge, Cambridge, CB2 3EA, UK.
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