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Cauz-Santos LA, Samuel R, Metschina D, Christenhusz MJM, Dodsworth S, Dixon KW, Conran JG, Paun O, Chase MW. Recent speciation and adaptation to aridity in the ecologically diverse Pilbara region of Australia enabled the native tobaccos (Nicotiana; Solanaceae) to colonize all Australian deserts. Mol Ecol 2024:e17498. [PMID: 39152668 DOI: 10.1111/mec.17498] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2023] [Revised: 08/01/2024] [Accepted: 08/05/2024] [Indexed: 08/19/2024]
Abstract
Over the last 6 million years, the arid Australian Eremaean Zone (EZ) has remained as dry as it is today. A widely accepted hypothesis suggests that the flora and fauna of arid regions were more broadly distributed before aridification began. In Australia, this process started around 20 million years ago (Ma), leading to gradual speciation as the climate became increasingly arid. Here, we use genomic data to investigate the biogeography and timing of divergence of native allotetraploid tobaccos, Nicotiana section Suaveolentes (Solanaceae). The original allotetraploid migrants from South America were adapted to mesic areas of Australia and recently radiated in the EZ, including in sandy dune fields (only 1.2 Ma old), after developing drought adaptations. Coalescent and maximum likelihood analyses suggest that Nicotiana section Suaveolentes arrived on the continent around 6 Ma, with the ancestors of the Pilbara (Western Australian) lineages radiating there at the onset of extreme aridity 5 Ma by locally adapting to these various ancient, highly stable habitats. The Pilbara thus served as both a mesic refugium and cradle for adaptations to harsher conditions, due to its high topographical diversity, providing microhabitats with varying moisture levels and its proximity to the ocean, which buffers against extreme aridity. This enabled species like Nicotiana to survive in mesic refugia and subsequently adapt to more arid conditions. These results demonstrate that initially poorly adapted plant groups can develop novel adaptations in situ, permitting extensive and rapid dispersal despite the highly variable and unpredictable extreme conditions of the EZ.
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Affiliation(s)
- Luiz A Cauz-Santos
- Department of Botany and Biodiversity Research, University of Vienna, Vienna, Austria
| | - Rosabelle Samuel
- Department of Botany and Biodiversity Research, University of Vienna, Vienna, Austria
| | - Dominik Metschina
- Department of Botany and Biodiversity Research, University of Vienna, Vienna, Austria
| | - Maarten J M Christenhusz
- Royal Botanic Gardens, Kew, Richmond, UK
- Department of Environment and Agriculture, Curtin University, Perth, Western Australia, Australia
| | - Steven Dodsworth
- School of Biological Sciences, University of Portsmouth, Portsmouth, UK
| | - Kingsley W Dixon
- Department of Environment and Agriculture, Curtin University, Perth, Western Australia, Australia
| | - John G Conran
- Environment Institute, School of Biological Sciences, The University of Adelaide, Adelaide, South Australia, Australia
| | - Ovidiu Paun
- Department of Botany and Biodiversity Research, University of Vienna, Vienna, Austria
| | - Mark W Chase
- Department of Botany and Biodiversity Research, University of Vienna, Vienna, Austria
- Royal Botanic Gardens, Kew, Richmond, UK
- Department of Environment and Agriculture, Curtin University, Perth, Western Australia, Australia
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2
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Matyášek R, Kalfusová R, Kuderová A, Řehůřková K, Sochorová J, Kovařík A. Transcriptional Silencing of 35S rDNA in Tragopogon porrifolius Correlates with Cytosine Methylation in Sequence-Specific Manner. Int J Mol Sci 2024; 25:7540. [PMID: 39062783 PMCID: PMC11276851 DOI: 10.3390/ijms25147540] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2024] [Revised: 06/21/2024] [Accepted: 07/04/2024] [Indexed: 07/28/2024] Open
Abstract
Despite the widely accepted involvement of DNA methylation in the regulation of rDNA transcription, the relative participation of different cytosine methylation pathways is currently described only for a few model plants. Using PacBio, Bisulfite, and RNA sequencing; PCR; Southern hybridizations; and FISH, the epigenetic consequences of rDNA copy number variation were estimated in two T. porrifolius lineages, por1 and por2, the latter with more than twice the rDNA copy numbers distributed approximately equally between NORs on chromosomes A and D. The lower rDNA content in por1 correlated with significantly reduced (>90%) sizes of both D-NORs. Moreover, two (L and S) prominent rDNA variants, differing in the repetitive organization of intergenic spacers, were detected in por2, while only the S-rDNA variant was detected in por1. Transcriptional activity of S-rDNA in por1 was associated with secondary constriction of both A-NORs. In contrast, silencing of S-rDNA in por2 was accompanied by condensation of A-NORs, secondary constriction on D-NORs, and L-rDNA transcriptional activity, suggesting (i) bidirectional nucleolar dominance and (ii) association of S-rDNAs with A-NORs and L-rDNAs with D-NORs in T. porrifolius. Each S- and L-rDNA array was formed of several sub-variants differentiating both genetically (specific SNPs) and epigenetically (transcriptional efficiency and cytosine methylation). The most significant correlations between rDNA silencing and methylation were detected for symmetric CWG motifs followed by CG motifs. No correlations were detected for external cytosine in CCGs or asymmetric CHHs, where methylation was rather position-dependent, particularly for AT-rich variants. We conclude that variations in rDNA copy numbers in plant diploids can be accompanied by prompt epigenetic responses to maintain an appropriate number of active rDNAs. The methylation dynamics of CWGs are likely to be the most responsible for regulating silent and active rDNA states.
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Affiliation(s)
- Roman Matyášek
- Institute of Biophysics of the Czech Academy of Sciences, 612 65 Brno, Czech Republic; (R.K.); (A.K.); (K.Ř.); (J.S.); (A.K.)
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3
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McEvoy SL, Grady PGS, Pauloski N, O'Neill RJ, Wegrzyn JL. Profiling genome-wide methylation in two maples: Fine-scale approaches to detection with nanopore technology. Evol Appl 2024; 17:e13669. [PMID: 38633133 PMCID: PMC11022628 DOI: 10.1111/eva.13669] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2023] [Revised: 02/04/2024] [Accepted: 02/12/2024] [Indexed: 04/19/2024] Open
Abstract
DNA methylation is critical to the regulation of transposable elements and gene expression and can play an important role in the adaptation of stress response mechanisms in plants. Traditional methods of methylation quantification rely on bisulfite conversion that can compromise accuracy. Recent advances in long-read sequencing technologies allow for methylation detection in real time. The associated algorithms that interpret these modifications have evolved from strictly statistical approaches to Hidden Markov Models and, recently, deep learning approaches. Much of the existing software focuses on methylation in the CG context, but methylation in other contexts is important to quantify, as it is extensively leveraged in plants. Here, we present methylation profiles for two maple species across the full range of 5mC sequence contexts using Oxford Nanopore Technologies (ONT) long-reads. Hybrid and reference-guided assemblies were generated for two new Acer accessions: Acer negundo (box elder; 65x ONT and 111X Illumina) and Acer saccharum (sugar maple; 93x ONT and 148X Illumina). The ONT reads generated for these assemblies were re-basecalled, and methylation detection was conducted in a custom pipeline with the published Acer references (PacBio assemblies) and hybrid assemblies reported herein to generate four epigenomes. Examination of the transposable element landscape revealed the dominance of LTR Copia elements and patterns of methylation associated with different classes of TEs. Methylation distributions were examined at high resolution across gene and repeat density and described within the broader angiosperm context, and more narrowly in the context of gene family dynamics and candidate nutrient stress genes.
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Affiliation(s)
- Susan L. McEvoy
- Department of Ecology and Evolutionary BiologyUniversity of ConnecticutStorrsConnecticutUSA
- Department of Forest SciencesUniversity of HelsinkiHelsinkiFinland
| | - Patrick G. S. Grady
- Department of Molecular and Cell BiologyUniversity of ConnecticutStorrsConnecticutUSA
| | - Nicole Pauloski
- Department of Molecular and Cell BiologyUniversity of ConnecticutStorrsConnecticutUSA
- Institute for Systems GenomicsUniversity of ConnecticutStorrsConnecticutUSA
| | - Rachel J. O'Neill
- Department of Molecular and Cell BiologyUniversity of ConnecticutStorrsConnecticutUSA
- Institute for Systems GenomicsUniversity of ConnecticutStorrsConnecticutUSA
| | - Jill L. Wegrzyn
- Department of Ecology and Evolutionary BiologyUniversity of ConnecticutStorrsConnecticutUSA
- Institute for Systems GenomicsUniversity of ConnecticutStorrsConnecticutUSA
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4
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Chen LG, Lan T, Zhang S, Zhao M, Luo G, Gao Y, Zhang Y, Du Q, Lu H, Li B, Jiao B, Hu Z, Ma Y, Zhao Q, Wang Y, Qian W, Dai J, Jiao Y. A designer synthetic chromosome fragment functions in moss. NATURE PLANTS 2024; 10:228-239. [PMID: 38278952 DOI: 10.1038/s41477-023-01595-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/19/2023] [Accepted: 11/22/2023] [Indexed: 01/28/2024]
Abstract
Rapid advances in DNA synthesis techniques have enabled the assembly and engineering of viral and microbial genomes, presenting new opportunities for synthetic genomics in multicellular eukaryotic organisms. These organisms, characterized by larger genomes, abundant transposons and extensive epigenetic regulation, pose unique challenges. Here we report the in vivo assembly of chromosomal fragments in the moss Physcomitrium patens, producing phenotypically virtually wild-type lines in which one-third of the coding region of a chromosomal arm is replaced by redesigned, chemically synthesized fragments. By eliminating 55.8% of a 155 kb endogenous chromosomal region, we substantially simplified the genome without discernible phenotypic effects, implying that many transposable elements may minimally impact growth. We also introduced other sequence modifications, such as PCRTag incorporation, gene locus swapping and stop codon substitution. Despite these substantial changes, the complex epigenetic landscape was normally established, albeit with some three-dimensional conformation alterations. The synthesis of a partial multicellular eukaryotic chromosome arm lays the foundation for the synthetic moss genome project (SynMoss) and paves the way for genome synthesis in multicellular organisms.
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Affiliation(s)
- Lian-Ge Chen
- State Key Laboratory of Plant Genomics, Institute of Genetics and Developmental Biology, The Innovative Academy of Seed Design, Chinese Academy of Sciences, Beijing, China
| | - Tianlong Lan
- College of Life Sciences, University of Chinese Academy of Sciences, Beijing, China
- Peking University-Tsinghua University-National Institute of Biological Sciences Joint Graduate Program, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing, China
- State Key Laboratory of Protein and Plant Gene Research, School of Life Sciences, Peking University, Beijing, China
| | - Shuo Zhang
- State Key Laboratory of Plant Genomics, Institute of Genetics and Developmental Biology, The Innovative Academy of Seed Design, Chinese Academy of Sciences, Beijing, China
- College of Advanced Agricultural Sciences, University of Chinese Academy of Sciences, Beijing, China
| | - Mengkai Zhao
- College of Life Sciences and Oceanography, Shenzhen University, Shenzhen, China
| | - Guangyu Luo
- CAS Key Laboratory of Quantitative Engineering Biology, Guangdong Provincial Key Laboratory of Synthetic Genomics and Shenzhen Key Laboratory of Synthetic Genomics, Shenzhen Institute of Synthetic Biology, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen, China
| | - Yi Gao
- College of Life Sciences, University of Chinese Academy of Sciences, Beijing, China
| | - Yuliang Zhang
- State Key Laboratory of Plant Genomics, Institute of Genetics and Developmental Biology, The Innovative Academy of Seed Design, Chinese Academy of Sciences, Beijing, China
- College of Advanced Agricultural Sciences, University of Chinese Academy of Sciences, Beijing, China
| | - Qingwei Du
- State Key Laboratory of Plant Genomics, Institute of Genetics and Developmental Biology, The Innovative Academy of Seed Design, Chinese Academy of Sciences, Beijing, China
- College of Advanced Agricultural Sciences, University of Chinese Academy of Sciences, Beijing, China
- Beijing Agro-Biotechnology Research Center, Beijing Academy of Agriculture and Forestry Sciences, Beijing, China
| | - Houze Lu
- School of Earth and Space Sciences, Peking University, Beijing, China
| | - Bimeng Li
- College of Life Sciences, University of Chinese Academy of Sciences, Beijing, China
| | - Bingke Jiao
- State Key Laboratory of Plant Genomics, Institute of Genetics and Developmental Biology, The Innovative Academy of Seed Design, Chinese Academy of Sciences, Beijing, China
- College of Advanced Agricultural Sciences, University of Chinese Academy of Sciences, Beijing, China
| | - Zhangli Hu
- College of Life Sciences and Oceanography, Shenzhen University, Shenzhen, China
| | - Yingxin Ma
- CAS Key Laboratory of Quantitative Engineering Biology, Guangdong Provincial Key Laboratory of Synthetic Genomics and Shenzhen Key Laboratory of Synthetic Genomics, Shenzhen Institute of Synthetic Biology, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen, China
| | - Qiao Zhao
- CAS Key Laboratory of Quantitative Engineering Biology, Guangdong Provincial Key Laboratory of Synthetic Genomics and Shenzhen Key Laboratory of Synthetic Genomics, Shenzhen Institute of Synthetic Biology, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen, China
| | - Ying Wang
- College of Life Sciences, University of Chinese Academy of Sciences, Beijing, China.
| | - Wenfeng Qian
- State Key Laboratory of Plant Genomics, Institute of Genetics and Developmental Biology, The Innovative Academy of Seed Design, Chinese Academy of Sciences, Beijing, China.
- College of Life Sciences, University of Chinese Academy of Sciences, Beijing, China.
| | - Junbiao Dai
- College of Life Sciences and Oceanography, Shenzhen University, Shenzhen, China.
- CAS Key Laboratory of Quantitative Engineering Biology, Guangdong Provincial Key Laboratory of Synthetic Genomics and Shenzhen Key Laboratory of Synthetic Genomics, Shenzhen Institute of Synthetic Biology, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen, China.
- 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, China.
| | - Yuling Jiao
- State Key Laboratory of Plant Genomics, Institute of Genetics and Developmental Biology, The Innovative Academy of Seed Design, Chinese Academy of Sciences, Beijing, China.
- State Key Laboratory of Protein and Plant Gene Research, School of Life Sciences, Peking University, Beijing, China.
- College of Advanced Agricultural Sciences, University of Chinese Academy of Sciences, Beijing, China.
- Peking-Tsinghua Center for Life Sciences, Center for Quantitative Biology, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing, China.
- Peking University Institute of Advanced Agricultural Sciences, Shandong Laboratory of Advanced Agricultural Sciences in Weifang, Weifang, China.
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Hisanaga T, Wu S, Schafran P, Axelsson E, Akimcheva S, Dolan L, Li F, Berger F. The ancestral chromatin landscape of land plants. THE NEW PHYTOLOGIST 2023; 240:2085-2101. [PMID: 37823324 PMCID: PMC10952607 DOI: 10.1111/nph.19311] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/28/2023] [Accepted: 08/29/2023] [Indexed: 10/13/2023]
Abstract
Recent studies have shown that correlations between chromatin modifications and transcription vary among eukaryotes. This is the case for marked differences between the chromatin of the moss Physcomitrium patens and the liverwort Marchantia polymorpha. Mosses and liverworts diverged from hornworts, altogether forming the lineage of bryophytes that shared a common ancestor with land plants. We aimed to describe chromatin in hornworts to establish synapomorphies across bryophytes and approach a definition of the ancestral chromatin organization of land plants. We used genomic methods to define the 3D organization of chromatin and map the chromatin landscape of the model hornwort Anthoceros agrestis. We report that nearly half of the hornwort transposons were associated with facultative heterochromatin and euchromatin and formed the center of topologically associated domains delimited by protein coding genes. Transposons were scattered across autosomes, which contrasted with the dense compartments of constitutive heterochromatin surrounding the centromeres in flowering plants. Most of the features observed in hornworts are also present in liverworts or in mosses but are distinct from flowering plants. Hence, the ancestral genome of bryophytes was likely a patchwork of units of euchromatin interspersed within facultative and constitutive heterochromatin. We propose this genome organization was ancestral to land plants.
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Affiliation(s)
- Tetsuya Hisanaga
- Gregor Mendel InstituteAustrian Academy of Sciences, Vienna BioCenterDr. Bohr‐Gasse 3Vienna1030Austria
| | - Shuangyang Wu
- Gregor Mendel InstituteAustrian Academy of Sciences, Vienna BioCenterDr. Bohr‐Gasse 3Vienna1030Austria
| | | | - Elin Axelsson
- Gregor Mendel InstituteAustrian Academy of Sciences, Vienna BioCenterDr. Bohr‐Gasse 3Vienna1030Austria
| | - Svetlana Akimcheva
- Gregor Mendel InstituteAustrian Academy of Sciences, Vienna BioCenterDr. Bohr‐Gasse 3Vienna1030Austria
| | - Liam Dolan
- Gregor Mendel InstituteAustrian Academy of Sciences, Vienna BioCenterDr. Bohr‐Gasse 3Vienna1030Austria
| | - Fay‐Wei Li
- Boyce Thompson InstituteIthacaNY14853USA
- Plant Biology SectionCornell UniversityIthacaNY14853USA
| | - Frédéric Berger
- Gregor Mendel InstituteAustrian Academy of Sciences, Vienna BioCenterDr. Bohr‐Gasse 3Vienna1030Austria
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Lin X, Tirichine L, Zhang X. The dynamic duo: how DNA methylation and gene transcription help diatoms thrive in modern oceans. JOURNAL OF EXPERIMENTAL BOTANY 2023; 74:3879-3882. [PMID: 37536061 PMCID: PMC10400112 DOI: 10.1093/jxb/erad205] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/05/2023]
Abstract
This article comments on:
Wan J, Zhou Y, Beardall J, Raven JA, Lin J, Huang J, Lu Y, Liang S, Ye M, Xiao M, Zhao J, Dai X, Xia J, Jin P. 2023. DNA methylation and gene transcription act cooperatively in driving the adaptation of a marine diatom to global change. Journal of Experimental Botany74, 4259–4276.
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Affiliation(s)
- Xin Lin
- State Key Laboratory of Marine Environmental Science, College of Ocean and Earth Sciences, Xiamen University, Xiamen, 361102, PR China
| | - Leila Tirichine
- Nantes Université, CNRS, US2B, UMR 6286, F-44000 Nantes, France
| | - Xu Zhang
- State Key Laboratory of Marine Environmental Science, College of Ocean and Earth Sciences, Xiamen University, Xiamen, 361102, PR China
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Yang C, Xia L, Fu M, Chen Y, Kong X, Zhang S. DNA methylation-mediated phenylpropane and starch metabolism causes male poplars to be more tolerant to nitrogen deficiency than females. PLANT PHYSIOLOGY AND BIOCHEMISTRY : PPB 2023; 195:144-154. [PMID: 36638604 DOI: 10.1016/j.plaphy.2023.01.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/22/2022] [Revised: 12/28/2022] [Accepted: 01/05/2023] [Indexed: 06/17/2023]
Abstract
Nitrogen (N) is an essential nutrient for plant growth and development. Dioecious plants, especially perennial plants, are often faced with a shortage of N supply in nature. Poplar is one of the most important dioecious and perennials species. Due to the different ecological functions, female and male poplars adopt different adaptation strategies to N limitation. However, the regulation in epigenetic mechanism is poorly understood on sexes. Here, the integrative analysis of whole-genome bisulfite sequencing (WGBS), RNA sequencing, and plant physiological analysis on female and male Populus cathayana were performed. We found that N deficiency reprograms methylation in both sexes, and the CG and CHH methylation types played critical roles in female and male poplars, respectively. Induced by DNA methylation, N-deficient males had a stronger phenylpropanoid synthesis pathway and less anthocyanin accumulation than females, which not only strengthened the N cycle but also reduced the defense cost of males. In addition, compared with male poplars, females accumulated more starch to expend excess energy under N limited condition. Additionally, DNA methylation also mediated hormone signalling involved in anthocyanin synthesis and starch metabolism. Therefore, our study reveals new molecular evidences that male poplars are more tolerant to N deficiency than females, which provides a reference for ecological adaptability of forest trees.
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Affiliation(s)
- Congcong Yang
- Key Laboratory of Bio-Resource and Eco-Environment of Ministry of Education, College of Life Sciences, Sichuan University, Chengdu, 610065, China
| | - Linchao Xia
- Key Laboratory of Bio-Resource and Eco-Environment of Ministry of Education, College of Life Sciences, Sichuan University, Chengdu, 610065, China
| | - Mingyue Fu
- Key Laboratory of Bio-Resource and Eco-Environment of Ministry of Education, College of Life Sciences, Sichuan University, Chengdu, 610065, China
| | - Yao Chen
- Key Laboratory of Bio-Resource and Eco-Environment of Ministry of Education, College of Life Sciences, Sichuan University, Chengdu, 610065, China
| | - Xiangge Kong
- Key Laboratory of Bio-Resource and Eco-Environment of Ministry of Education, College of Life Sciences, Sichuan University, Chengdu, 610065, China
| | - Sheng Zhang
- Key Laboratory of Bio-Resource and Eco-Environment of Ministry of Education, College of Life Sciences, Sichuan University, Chengdu, 610065, China.
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Griess O, Domb K, Katz A, Harris KD, Heskiau KG, Ohad N, Zemach A. Knockout of DDM1 in Physcomitrium patens disrupts DNA methylation with a minute effect on transposon regulation and development. PLoS One 2023; 18:e0279688. [PMID: 36888585 PMCID: PMC9994747 DOI: 10.1371/journal.pone.0279688] [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: 07/24/2022] [Accepted: 12/13/2022] [Indexed: 03/09/2023] Open
Abstract
The Snf2 chromatin remodeler, DECREASE IN DNA METHYLATION 1 (DDM1) facilitates DNA methylation. In flowering plants, DDM1 mediates methylation in heterochromatin, which is targeted primarily by MET1 and CMT methylases and is necessary for silencing transposons and for proper development. DNA methylation mechanisms evolved throughout plant evolution, whereas the role of DDM1 in early terrestrial plants remains elusive. Here, we studied the function of DDM1 in the moss, Physcomitrium (Physcomitrella) patens, which has robust DNA methylation that suppresses transposons and is mediated by a MET1, a CMT, and a DNMT3 methylases. To elucidate the role of DDM1 in P. patens, we have generated a knockout mutant and found DNA methylation to be strongly disrupted at any of its sequence contexts. Symmetric CG and CHG sequences were affected stronger than asymmetric CHH sites. Furthermore, despite their separate targeting mechanisms, CG (MET) and CHG (CMT) methylation were similarly depleted by about 75%. CHH (DNMT3) methylation was overall reduced by about 25%, with an evident hyper-methylation activity within lowly-methylated euchromatic transposon sequences. Despite the strong hypomethylation effect, only a minute number of transposons were transcriptionally activated in Ppddm1. Finally, Ppddm1 was found to develop normally throughout the plant life cycle. These results demonstrate that DNA methylation is strongly dependent on DDM1 in a non-flowering plant; that DDM1 is required for plant-DNMT3 (CHH) methylases, though to a lower extent than for MET1 and CMT enzymes; and that distinct and separate methylation pathways (e.g. MET1-CG and CMT-CHG), can be equally regulated by the chromatin and that DDM1 plays a role in it. Finally, our data suggest that the biological significance of DDM1 in terms of transposon regulation and plant development, is species dependent.
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Affiliation(s)
- Ofir Griess
- School of Plant Sciences and Food Security, Tel-Aviv University, Tel- Aviv, Israel
| | - Katherine Domb
- School of Plant Sciences and Food Security, Tel-Aviv University, Tel- Aviv, Israel
| | - Aviva Katz
- School of Plant Sciences and Food Security, Tel-Aviv University, Tel- Aviv, Israel
| | - Keith D. Harris
- School of Plant Sciences and Food Security, Tel-Aviv University, Tel- Aviv, Israel
| | - Karina G. Heskiau
- School of Plant Sciences and Food Security, Tel-Aviv University, Tel- Aviv, Israel
| | - Nir Ohad
- School of Plant Sciences and Food Security, Tel-Aviv University, Tel- Aviv, Israel
- * E-mail: (AZ); (NO)
| | - Assaf Zemach
- School of Plant Sciences and Food Security, Tel-Aviv University, Tel- Aviv, Israel
- * E-mail: (AZ); (NO)
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Chang YTS, Yen MR, Chen PY. Methylome Imputation by Methylation Patterns. Methods Mol Biol 2023; 2624:115-126. [PMID: 36723812 DOI: 10.1007/978-1-0716-2962-8_8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
DNA methylation is studied extensively for its relations with several biological processes such as transcriptional regulation. While methylation levels are usually estimated per cytosine or genomic region, additional information on methylation heterogeneity can be obtained when considering stretches of successive cytosines on the same reads; however, the majority of methylomes suffer from low coverage of genomic regions with sequencing depths enough for accurate estimation of methylation heterogeneity using existing methods. Here we describe a probabilistic-based imputation method that makes use of methylation information from neighboring sites to recover partially observed methylation patterns. Our method and software are proven to be faster and more accurate among all evaluated. Ultimately, our method allows for a more streamlined monitoring of epigenetic changes within cellular populations and their putative role in disease.
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Affiliation(s)
| | - Ming-Ren Yen
- Institute of Plant and Microbial Biology, Academia Sinica, Taipei, Taiwan
| | - Pao-Yang Chen
- Institute of Plant and Microbial Biology, Academia Sinica, Taipei, Taiwan.
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10
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Chakraborty T, Payne H, Mosher RA. Expansion and contraction of small RNA and methylation machinery throughout plant evolution. CURRENT OPINION IN PLANT BIOLOGY 2022; 69:102260. [PMID: 35849937 DOI: 10.1016/j.pbi.2022.102260] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/25/2022] [Revised: 06/09/2022] [Accepted: 06/14/2022] [Indexed: 06/15/2023]
Abstract
The revolution in sequencing has created a wealth of plant genomes that can be mined to understand the evolution of biological complexity. Complexity is often driven by gene duplication, which allows paralogs to specialize in an activity of the ancestral gene or acquire novel functions. Angiosperms encode a variety of gene silencing pathways that share related machinery for small RNA biosynthesis and function. Recent phylogenetic analysis of these gene families plots the expansion, specialization, and occasional contraction of this core machinery. This analysis reveals the ancient origin of RNA-directed DNA Methylation in early land plants, or possibly their algal ancestors, as well as ongoing duplications that evolve novel small RNA pathways.
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Affiliation(s)
- Tania Chakraborty
- School of Plant Sciences, University of Arizona, Tucson, AZ 85721-0036, USA
| | - Hayden Payne
- School of Plant Sciences, University of Arizona, Tucson, AZ 85721-0036, USA
| | - Rebecca A Mosher
- School of Plant Sciences, University of Arizona, Tucson, AZ 85721-0036, USA.
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11
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To TK, Kakutani T. Crosstalk among pathways to generate DNA methylome. CURRENT OPINION IN PLANT BIOLOGY 2022; 68:102248. [PMID: 35724481 DOI: 10.1016/j.pbi.2022.102248] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/30/2022] [Revised: 05/19/2022] [Accepted: 05/19/2022] [Indexed: 06/15/2023]
Abstract
Cytosine is methylated in both CpG and non-CpG contexts (mCG and mCH, respectively) in plant genomes. Although mCG and mCH are almost independent in regard to their "maintenance," recent studies uncovered crosstalk between them during their "establishment," which unexpectedly functions in both RNAi-dependent and -independent pathways. In addition, the importance of linker histone H1 and variants of histone H2A to DNA methylation dynamics is starting to be understood. We summarize these new aspects of mechanisms to generate DNA methylomes and discuss future prospects.
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Affiliation(s)
- Taiko Kim To
- Department of Biological Sciences, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Tetsuji Kakutani
- Department of Biological Sciences, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
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Cauz‐Santos LA, Dodsworth S, Samuel R, Christenhusz MJM, Patel D, Shittu T, Jakob A, Paun O, Chase MW. Genomic insights into recent species divergence in Nicotiana benthamiana and natural variation in Rdr1 gene controlling viral susceptibility. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2022; 111:7-18. [PMID: 35535507 PMCID: PMC9543217 DOI: 10.1111/tpj.15801] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/10/2022] [Revised: 05/05/2022] [Accepted: 05/07/2022] [Indexed: 05/31/2023]
Abstract
One of the most commonly encountered and frequently cited laboratory organisms worldwide is classified taxonomically as Nicotiana benthamiana (Solanaceae), an accession of which, typically referred to as LAB, is renowned for its unique susceptibility to a wide range of plant viruses and hence capacity to be transformed using a variety of methods. This susceptibility is the result of an insertion and consequent loss of function in the RNA-dependent RNA polymerase 1 (Rdr1) gene. However, the origin and age of LAB and the evolution of N. benthamiana across its wide distribution in Australia remain relatively underexplored. Here, we have used multispecies coalescent methods on genome-wide single nucleotide polymorphisms (SNPs) to assess species limits, phylogenetic relationships and divergence times within N. benthamiana. Our results show that the previous taxonomic concept of this species in fact comprises five geographically, morphologically and genetically distinct species, one of which includes LAB. We provide clear evidence that LAB is closely related to accessions collected further north in the Northern Territory; this species split much earlier, c. 1.1 million years ago, from their common ancestor than the other four in this clade and is morphologically the most distinctive. We also found that the Rdr1 gene insertion is variable among accessions from the northern portions of the Northern Territory. Furthermore, this long-isolated species typically grows in sheltered sites in subtropical/tropical monsoon areas of northern Australia, contradicting the previously advanced hypothesis that this species is an extremophile that has traded viral resistance for precocious development.
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Affiliation(s)
- Luiz A. Cauz‐Santos
- Department of Botany and Biodiversity ResearchUniversity of ViennaRennweg 14A‐1030ViennaAustria
| | - Steven Dodsworth
- School of Biological SciencesUniversity of PortsmouthKing Henry Building, King Henry 1 StreetPortsmouthPO1 2DYUK
- School of Life SciencesUniversity of Bedfordshire, University SquareLutonBedfordshireLU1 3JUUK
| | - Rosabelle Samuel
- Department of Botany and Biodiversity ResearchUniversity of ViennaRennweg 14A‐1030ViennaAustria
| | | | - Denise Patel
- School of Life SciencesUniversity of Bedfordshire, University SquareLutonBedfordshireLU1 3JUUK
| | - Taiwo Shittu
- School of Life SciencesUniversity of Bedfordshire, University SquareLutonBedfordshireLU1 3JUUK
| | - Aljaž Jakob
- Department of Botany and Biodiversity ResearchUniversity of ViennaRennweg 14A‐1030ViennaAustria
| | - Ovidiu Paun
- Department of Botany and Biodiversity ResearchUniversity of ViennaRennweg 14A‐1030ViennaAustria
| | - Mark W. Chase
- Department of Botany and Biodiversity ResearchUniversity of ViennaRennweg 14A‐1030ViennaAustria
- Royal Botanic GardensKewRichmondTW9 3DSUK
- Department of Environment and AgricultureCurtin UniversityPerthWestern AustraliaAustralia
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13
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Vigneau J, Borg M. The epigenetic origin of life history transitions in plants and algae. PLANT REPRODUCTION 2021; 34:267-285. [PMID: 34236522 PMCID: PMC8566409 DOI: 10.1007/s00497-021-00422-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/13/2021] [Accepted: 06/14/2021] [Indexed: 05/17/2023]
Abstract
Plants and algae have a complex life history that transitions between distinct life forms called the sporophyte and the gametophyte. This phenomenon-called the alternation of generations-has fascinated botanists and phycologists for over 170 years. Despite the mesmerizing array of life histories described in plants and algae, we are only now beginning to learn about the molecular mechanisms controlling them and how they evolved. Epigenetic silencing plays an essential role in regulating gene expression during multicellular development in eukaryotes, raising questions about its impact on the life history strategy of plants and algae. Here, we trace the origin and function of epigenetic mechanisms across the plant kingdom, from unicellular green algae through to angiosperms, and attempt to reconstruct the evolutionary steps that influenced life history transitions during plant evolution. Central to this evolutionary scenario is the adaption of epigenetic silencing from a mechanism of genome defense to the repression and control of alternating generations. We extend our discussion beyond the green lineage and highlight the peculiar case of the brown algae. Unlike their unicellular diatom relatives, brown algae lack epigenetic silencing pathways common to animals and plants yet display complex life histories, hinting at the emergence of novel life history controls during stramenopile evolution.
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Affiliation(s)
- Jérômine Vigneau
- Department of Algal Development and Evolution, Max Planck Institute for Developmental Biology, Tübingen, Germany
| | - Michael Borg
- Department of Algal Development and Evolution, Max Planck Institute for Developmental Biology, Tübingen, Germany.
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14
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Methylation patterns of Tf2 retrotransposons linked to rapid adaptive stress response in the brown planthopper (Nilaparvata lugens). Genomics 2021; 113:4214-4226. [PMID: 34774681 DOI: 10.1016/j.ygeno.2021.11.007] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2021] [Revised: 10/12/2021] [Accepted: 11/07/2021] [Indexed: 11/23/2022]
Abstract
Transposable elements (TEs) exhibit vast diversity across insect orders and are one of the major factors driving insect evolution and speciation. Presence of TEs can be both beneficial and deleterious to their host. While it is well-established that TEs impact life-history traits, adaptations and survivability of insects under hostile environments, the influence of the ecological niche on TE-landscape remains unclear. Here, we analysed the dynamics of Tf2 retrotransposons in the brown planthopper (BPH), under environmental fluctuations. BPH, a major pest of rice, is found in almost all rice-growing ecosystems. We believe genome plasticity, attributed to TEs, has allowed BPH to adapt and colonise novel ecological niches. Our study revealed bimodal age-distribution for Tf2 elements in BPH, indicating the occurrence of two major transpositional events in its evolutionary history and their contribution in shaping BPH genome. While TEs can provide genome flexibility and facilitate adaptations, they impose massive load on the genome. Hence, we investigated the involvement of methylation in modulating transposition in BPH. We performed comparative analyses of the methylation patterns of Tf2 elements in BPH feeding on resistant- and susceptible-rice varieties, and also under pesticide stress, across different life-stages. Results confirmed that methylation, particularly in non-CG context, is involved in TE regulation and dynamics under stress. Furthermore, we observed differential methylation for BPH adults and nymphs, emphasising the importance of screening juvenile life-stages in understanding adaptive-stress-responses in insects. Collectively, this study enhances our understanding of the role of transposons in influencing the evolutionary trajectory and survival strategies of BPH across generations.
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15
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Ni P, Huang N, Nie F, Zhang J, Zhang Z, Wu B, Bai L, Liu W, Xiao CL, Luo F, Wang J. Genome-wide detection of cytosine methylations in plant from Nanopore data using deep learning. Nat Commun 2021; 12:5976. [PMID: 34645826 PMCID: PMC8514461 DOI: 10.1038/s41467-021-26278-9] [Citation(s) in RCA: 41] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2021] [Accepted: 09/28/2021] [Indexed: 11/09/2022] Open
Abstract
In plants, cytosine DNA methylations (5mCs) can happen in three sequence contexts as CpG, CHG, and CHH (where H = A, C, or T), which play different roles in the regulation of biological processes. Although long Nanopore reads are advantageous in the detection of 5mCs comparing to short-read bisulfite sequencing, existing methods can only detect 5mCs in the CpG context, which limits their application in plants. Here, we develop DeepSignal-plant, a deep learning tool to detect genome-wide 5mCs of all three contexts in plants from Nanopore reads. We sequence Arabidopsis thaliana and Oryza sativa using both Nanopore and bisulfite sequencing. We develop a denoising process for training models, which enables DeepSignal-plant to achieve high correlations with bisulfite sequencing for 5mC detection in all three contexts. Furthermore, DeepSignal-plant can profile more 5mC sites, which will help to provide a more complete understanding of epigenetic mechanisms of different biological processes.
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Affiliation(s)
- Peng Ni
- School of Computer Science and Engineering, Central South University, Changsha, 410083, China
- Hunan Provincial Key Lab on Bioinformatics, Central South University, Changsha, 410083, China
| | - Neng Huang
- School of Computer Science and Engineering, Central South University, Changsha, 410083, China
- Hunan Provincial Key Lab on Bioinformatics, Central South University, Changsha, 410083, China
| | - Fan Nie
- School of Computer Science and Engineering, Central South University, Changsha, 410083, China
- Hunan Provincial Key Lab on Bioinformatics, Central South University, Changsha, 410083, China
| | - Jun Zhang
- School of Computer Science and Engineering, Central South University, Changsha, 410083, China
- Hunan Provincial Key Lab on Bioinformatics, Central South University, Changsha, 410083, China
| | - Zhi Zhang
- School of Computer Science and Engineering, Central South University, Changsha, 410083, China
- Hunan Provincial Key Lab on Bioinformatics, Central South University, Changsha, 410083, China
| | - Bo Wu
- School of Computing, Clemson University, Clemson, SC, 29634-0974, USA
| | - Lu Bai
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, China
| | - Wende Liu
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, China
| | - Chuan-Le Xiao
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, #7 Jinsui Road, Tianhe District, Guangzhou, China.
| | - Feng Luo
- School of Computing, Clemson University, Clemson, SC, 29634-0974, USA.
| | - Jianxin Wang
- School of Computer Science and Engineering, Central South University, Changsha, 410083, China.
- Hunan Provincial Key Lab on Bioinformatics, Central South University, Changsha, 410083, China.
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16
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Rothi MH, Tsuzuki M, Sethuraman S, Wierzbicki AT. Reinforcement of transcriptional silencing by a positive feedback between DNA methylation and non-coding transcription. Nucleic Acids Res 2021; 49:9799-9808. [PMID: 34469565 PMCID: PMC8464056 DOI: 10.1093/nar/gkab746] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2021] [Revised: 07/09/2021] [Accepted: 08/23/2021] [Indexed: 11/12/2022] Open
Abstract
Non-coding transcription is an important determinant of heterochromatin formation. In Arabidopsis thaliana a specialized RNA polymerase V (Pol V) transcribes pervasively and produces long non-coding RNAs. These transcripts work with small interfering RNA to facilitate locus-specific establishment of RNA-directed DNA methylation (RdDM). Subsequent maintenance of RdDM is associated with elevated levels of Pol V transcription. However, the impact of DNA methylation on Pol V transcription remained unresolved. We found that DNA methylation strongly enhances Pol V transcription. The level of Pol V transcription is reduced in mutants defective in RdDM components working downstream of Pol V, indicating that RdDM is maintained by a mutual reinforcement of DNA methylation and Pol V transcription. Pol V transcription is affected only on loci that lose DNA methylation in all sequence contexts in a particular mutant, including mutants lacking maintenance DNA methyltransferases, which suggests that RdDM works in a complex crosstalk with other silencing pathways.
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Affiliation(s)
- M Hafiz Rothi
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI 48109, USA
| | - Masayuki Tsuzuki
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI 48109, USA.,Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, Meguro-ku, Tokyo 153-8902, Japan
| | - Shriya Sethuraman
- Bioinformatics Graduate Program, University of Michigan, Ann Arbor, MI 48109, USA
| | - Andrzej T Wierzbicki
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI 48109, USA
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17
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Szövényi P, Gunadi A, Li FW. Charting the genomic landscape of seed-free plants. NATURE PLANTS 2021; 7:554-565. [PMID: 33820965 DOI: 10.1038/s41477-021-00888-z] [Citation(s) in RCA: 30] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/10/2020] [Accepted: 02/25/2021] [Indexed: 05/02/2023]
Abstract
During the past few years several high-quality genomes has been published from Charophyte algae, bryophytes, lycophytes and ferns. These genomes have not only elucidated the origin and evolution of early land plants, but have also provided important insights into the biology of the seed-free lineages. However, critical gaps across the phylogeny remain and many new questions have been raised through comparing seed-free and seed plant genomes. Here, we review the reference genomes available and identify those that are missing in the seed-free lineages. We compare patterns of various levels of genome and epigenomic organization found in seed-free plants to those of seed plants. Some genomic features appear to be fundamentally different. For instance, hornworts, Selaginella and most liverworts are devoid of whole-genome duplication, in stark contrast to other land plants. In addition, the distribution of genes and repeats appear to be less structured in seed-free genomes than in other plants, and the levels of gene body methylation appear to be much lower. Finally, we highlight the currently available (or needed) model systems, which are crucial to further our understanding about how changes in genes translate into evolutionary novelties.
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Affiliation(s)
- Péter Szövényi
- Department of Systematic and Evolutionary Botany, University of Zurich and Zurich-Basel Plant Science Center, Zurich, Switzerland.
| | | | - Fay-Wei Li
- Boyce Thompson Institute, Ithaca, NY, USA
- Plant Biology Section, Cornell University, Ithaca, NY, USA
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18
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Ross SE, Hesselson D, Bogdanovic O. Developmental Accumulation of Gene Body and Transposon Non-CpG Methylation in the Zebrafish Brain. Front Cell Dev Biol 2021; 9:643603. [PMID: 33748137 PMCID: PMC7978034 DOI: 10.3389/fcell.2021.643603] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2020] [Accepted: 02/08/2021] [Indexed: 12/13/2022] Open
Abstract
DNA methylation predominantly occurs at CG dinucleotides in vertebrate genomes; however, non-CG methylation (mCH) is also detectable in vertebrate tissues, most notably in the nervous system. In mammals it is well established that mCH is targeted to CAC trinucleotides by DNMT3A during nervous system development where it is enriched in gene bodies and associated with transcriptional repression. Nevertheless, the conservation of developmental mCH accumulation and its deposition by DNMT3A is largely unexplored and has yet to be functionally demonstrated in other vertebrates. In this study, by analyzing DNA methylomes and transcriptomes of zebrafish brains, we identified enrichment of mCH at CAC trinucleotides (mCAC) at defined transposon motifs as well as in developmentally downregulated genes associated with developmental and neural functions. We further generated and analyzed DNA methylomes and transcriptomes of developing zebrafish larvae and demonstrated that, like in mammals, mCH accumulates during post-embryonic brain development. Finally, by employing CRISPR/Cas9 technology, we unraveled a conserved role for Dnmt3a enzymes in developmental mCAC deposition. Overall, this work demonstrates the evolutionary conservation of developmental mCH dynamics and highlights the potential of zebrafish as a model to study mCH regulation and function during normal and perturbed development.
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Affiliation(s)
- Samuel E Ross
- Genomics and Epigenetics Division, Garvan Institute of Medical Research, Sydney, NSW, Australia.,Faculty of Medicine, St Vincent's Clinical School, University of New South Wales, Sydney, NSW, Australia
| | - Daniel Hesselson
- Centenary Institute, The University of Sydney, Sydney, NSW, Australia.,Faculty of Medicine and Health, The University of Sydney, Sydney, NSW, Australia
| | - Ozren Bogdanovic
- Genomics and Epigenetics Division, Garvan Institute of Medical Research, Sydney, NSW, Australia.,School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, NSW, Australia
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19
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Markulin L, Škiljaica A, Tokić M, Jagić M, Vuk T, Bauer N, Leljak Levanić D. Taking the Wheel - de novo DNA Methylation as a Driving Force of Plant Embryonic Development. FRONTIERS IN PLANT SCIENCE 2021; 12:764999. [PMID: 34777448 PMCID: PMC8585777 DOI: 10.3389/fpls.2021.764999] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/26/2021] [Accepted: 10/13/2021] [Indexed: 05/16/2023]
Abstract
During plant embryogenesis, regardless of whether it begins with a fertilized egg cell (zygotic embryogenesis) or an induced somatic cell (somatic embryogenesis), significant epigenetic reprogramming occurs with the purpose of parental or vegetative transcript silencing and establishment of a next-generation epigenetic patterning. To ensure genome stability of a developing embryo, large-scale transposon silencing occurs by an RNA-directed DNA methylation (RdDM) pathway, which introduces methylation patterns de novo and as such potentially serves as a global mechanism of transcription control during developmental transitions. RdDM is controlled by a two-armed mechanism based around the activity of two RNA polymerases. While PolIV produces siRNAs accompanied by protein complexes comprising the methylation machinery, PolV produces lncRNA which guides the methylation machinery toward specific genomic locations. Recently, RdDM has been proposed as a dominant methylation mechanism during gamete formation and early embryo development in Arabidopsis thaliana, overshadowing all other methylation mechanisms. Here, we bring an overview of current knowledge about different roles of DNA methylation with emphasis on RdDM during plant zygotic and somatic embryogenesis. Based on published chromatin immunoprecipitation data on PolV binding sites within the A. thaliana genome, we uncover groups of auxin metabolism, reproductive development and embryogenesis-related genes, and discuss possible roles of RdDM at the onset of early embryonic development via targeted methylation at sites involved in different embryogenesis-related developmental mechanisms.
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