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Tonosaki K, Susaki D, Morinaka H, Ono A, Nagata H, Furuumi H, Nonomura KI, Sato Y, Sugimoto K, Comai L, Hatakeyama K, Kawakatsu T, Kinoshita T. Multilayered epigenetic control of persistent and stage-specific imprinted genes in rice endosperm. NATURE PLANTS 2024; 10:1231-1245. [PMID: 39080502 DOI: 10.1038/s41477-024-01754-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/22/2022] [Accepted: 07/01/2024] [Indexed: 08/22/2024]
Abstract
In angiosperms, epigenetic profiles for genomic imprinting are established before fertilization. However, the causal relationships between epigenetic modifications and imprinted expression are not fully understood. In this study, we classified 'persistent' and 'stage-specific' imprinted genes on the basis of time-course transcriptome analysis in rice (Oryza sativa) endosperm and compared them to epigenetic modifications at a single time point. While the levels of epigenetic modifications are relatively low in stage-specific imprinted genes, they are considerably higher in persistent imprinted genes. Overall trends revealed that the maternal alleles of maternally expressed imprinted genes are activated by DNA demethylation, while the maternal alleles of paternally expressed imprinted genes with gene body methylation (gbM) are silenced by DNA demethylation and H3K27me3 deposition, and these regions are associated with an enriched motif related to Tc/Mar-Stowaway. Our findings provide insight into the stability of genomic imprinting and the potential variations associated with endosperm development, different cell types and parental genotypes.
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Grants
- 20K15504 Ministry of Education, Culture, Sports, Science and Technology (MEXT)
- 22K15145 Ministry of Education, Culture, Sports, Science and Technology (MEXT)
- 23H04749 Ministry of Education, Culture, Sports, Science and Technology (MEXT)
- 23H04756 Ministry of Education, Culture, Sports, Science and Technology (MEXT)
- 23K23585 Ministry of Education, Culture, Sports, Science and Technology (MEXT)
- 22H05175 Ministry of Education, Culture, Sports, Science and Technology (MEXT)
- 21H02170 Ministry of Education, Culture, Sports, Science and Technology (MEXT)
- 22H02320 Ministry of Education, Culture, Sports, Science and Technology (MEXT)
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Affiliation(s)
- Kaoru Tonosaki
- Kihara Institute for Biological Research, Yokohama City University, Yokohama, Kanagawa, Japan.
- Faculty of Agriculture, Iwate University, Morioka, Iwate, Japan.
| | - Daichi Susaki
- Kihara Institute for Biological Research, Yokohama City University, Yokohama, Kanagawa, Japan
| | - Hatsune Morinaka
- RIKEN Center for Sustainable Resource Science, Yokohama, Kanagawa, Japan
| | - Akemi Ono
- Kihara Institute for Biological Research, Yokohama City University, Yokohama, Kanagawa, Japan
| | - Hiroki Nagata
- Kihara Institute for Biological Research, Yokohama City University, Yokohama, Kanagawa, Japan
| | - Hiroyasu Furuumi
- Genetic Strains Research Center, National Institute of Genetics, Mishima, Shizuoka, Japan
| | - Ken-Ichi Nonomura
- Plant Cytogenetics, National Institute of Genetics, Mishima, Shizuoka, Japan
| | - Yutaka Sato
- Genetic Strains Research Center, National Institute of Genetics, Mishima, Shizuoka, Japan
| | - Keiko Sugimoto
- RIKEN Center for Sustainable Resource Science, Yokohama, Kanagawa, Japan
| | - Luca Comai
- Department of Plant Biology and Genome Center, University of California, Davis, CA, USA
| | | | - Taiji Kawakatsu
- Institute of Agrobiological Sciences, National Agriculture and Food Research Organization, Tsukuba, Ibaraki, Japan.
| | - Tetsu Kinoshita
- Kihara Institute for Biological Research, Yokohama City University, Yokohama, Kanagawa, Japan.
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2
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June V, Song X, Chen ZJ. Imprinting but not cytonuclear interactions determines seed size heterosis in Arabidopsis hybrids. PLANT PHYSIOLOGY 2024; 195:1214-1228. [PMID: 38319651 PMCID: PMC11142339 DOI: 10.1093/plphys/kiae061] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/15/2023] [Revised: 12/14/2023] [Accepted: 12/19/2023] [Indexed: 02/07/2024]
Abstract
The parent-of-origin effect on seeds can result from imprinting (unequal expression of paternal and maternal alleles) or combinational effects between cytoplasmic and nuclear genomes, but their relative contributions remain unknown. To discern these confounding factors, we produced cytoplasmic-nuclear substitution (CNS) lines using recurrent backcrossing in Arabidopsis (Arabidopsis thaliana) ecotypes Col-0 and C24. These CNS lines differed only in the nuclear genome (imprinting) or cytoplasm. The CNS reciprocal hybrids with the same cytoplasm displayed ∼20% seed size difference, whereas the seed size was similar between the reciprocal hybrids with fixed imprinting. Transcriptome analyses in the endosperm of CNS hybrids using laser-capture microdissection identified 104 maternally expressed genes (MEGs) and 90 paternally expressed genes (PEGs). These imprinted genes were involved in pectin catabolism and cell wall modification in the endosperm. Homeodomain Glabrous9 (HDG9), an epiallele and one of 11 cross-specific imprinted genes, affected seed size. In the embryo, there were a handful of imprinted genes in the CNS hybrids but only 1 was expressed at higher levels than in the endosperm. AT4G13495 was found to encode a long-noncoding RNA (lncRNA), but no obvious seed phenotype was observed in lncRNA knockout lines. Nuclear RNA Polymerase D1 (NRPD1), encoding the largest subunit of RNA Pol IV, was involved in the biogenesis of small interfering RNAs. Seed size and embryos were larger in the cross using nrpd1 as the maternal parent than in the reciprocal cross, supporting a role of the maternal NRPD1 allele in seed development. Although limited ecotypes were tested, these results suggest that imprinting and the maternal NRPD1-mediated small RNA pathway play roles in seed size heterosis in plant hybrids.
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Affiliation(s)
- Viviana June
- Department of Molecular Biosciences, The University of Texas at Austin, Austin, TX 78712, USA
| | - Xiaoya Song
- Department of Molecular Biosciences, The University of Texas at Austin, Austin, TX 78712, USA
| | - Z Jeffrey Chen
- Department of Molecular Biosciences, The University of Texas at Austin, Austin, TX 78712, USA
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3
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Miller JR, Adjeroh DA. Machine learning on alignment features for parent-of-origin classification of simulated hybrid RNA-seq. BMC Bioinformatics 2024; 25:109. [PMID: 38475727 DOI: 10.1186/s12859-024-05728-3] [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: 07/28/2023] [Accepted: 03/01/2024] [Indexed: 03/14/2024] Open
Abstract
BACKGROUND Parent-of-origin allele-specific gene expression (ASE) can be detected in interspecies hybrids by virtue of RNA sequence variants between the parental haplotypes. ASE is detectable by differential expression analysis (DEA) applied to the counts of RNA-seq read pairs aligned to parental references, but aligners do not always choose the correct parental reference. RESULTS We used public data for species that are known to hybridize. We measured our ability to assign RNA-seq read pairs to their proper transcriptome or genome references. We tested software packages that assign each read pair to a reference position and found that they often favored the incorrect species reference. To address this problem, we introduce a post process that extracts alignment features and trains a random forest classifier to choose the better alignment. On each simulated hybrid dataset tested, our machine-learning post-processor achieved higher accuracy than the aligner by itself at choosing the correct parent-of-origin per RNA-seq read pair. CONCLUSIONS For the parent-of-origin classification of RNA-seq, machine learning can improve the accuracy of alignment-based methods. This approach could be useful for enhancing ASE detection in interspecies hybrids, though RNA-seq from real hybrids may present challenges not captured by our simulations. We believe this is the first application of machine learning to this problem domain.
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Affiliation(s)
- Jason R Miller
- Department of Computer Science, Mathematics, Engineering, Shepherd University, Shepherdstown, WV, USA.
- EVOGENE, Department of Biosciences, University of Oslo, Oslo, Norway.
- Lane Department of Computer Science and Electrical Engineering, West Virginia University, Morgantown, WV, USA.
| | - Donald A Adjeroh
- Lane Department of Computer Science and Electrical Engineering, West Virginia University, Morgantown, WV, USA
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June V, Song X, Jeffrey Chen Z. Imprinting but not cytonuclear interactions affects parent-of-origin effect on seed size in Arabidopsis hybrids. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.09.15.557997. [PMID: 37745544 PMCID: PMC10516054 DOI: 10.1101/2023.09.15.557997] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/26/2023]
Abstract
The parent-of-origin effect on seed size can result from imprinting or a combinational effect between cytoplasmic and nuclear genomes, but their relative contributions remain unknown. To discern these confounding effects, we generated cytoplasmic-nuclear substitution (CNS) lines using recurrent backcrossing in the Arabidopsis thaliana ecotypes Col-0 and C24. These CNS lines differ only in the nuclear genome (imprinting) or in the cytoplasm. The CNS reciprocal hybrids with the same cytoplasm display a ~20% seed size difference as observed in the conventional hybrids. However, seed size is similar between the reciprocal cybrids with fixed imprinting. Transcriptome analyses in the endosperm of CNS hybrids using laser-capture microdissection have identified 104 maternally expressed genes (MEGs) and 90 paternally-expressed genes (PEGs). These imprinted genes are involved in pectin catabolism and cell wall modification in the endosperm. HDG9, an epiallele and one of 11 cross-specific imprinted genes, controls seed size. In the embryo, a handful of imprinted genes is found in the CNS hybrids but only one is expressed higher in the embryo than endosperm. AT4G13495 encodes a long-noncoding RNA (lncRNA), but no obvious seed phenotype is observed in the lncRNA knockout lines. NRPD1, encoding the largest subunit of RNA Pol IV, is involved in the biogenesis of small interfering RNAs. Seed size and embryo is larger in the cross using nrpd1 as the maternal parent than in the reciprocal cross. In spite of limited ecotypes tested, these results suggest potential roles of imprinting and NRPD1-mediated small RNA pathway in seed size variation in hybrids.
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Affiliation(s)
- Viviana June
- Department of Molecular Biosciences, The University of Texas at Austin, Austin, Texas 78712, USA
| | - Xiaoya Song
- Department of Molecular Biosciences, The University of Texas at Austin, Austin, Texas 78712, USA
| | - Z. Jeffrey Chen
- Department of Molecular Biosciences, The University of Texas at Austin, Austin, Texas 78712, USA
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Zhang H, Gong Z, Zhu JK. Active DNA demethylation in plants: 20 years of discovery and beyond. JOURNAL OF INTEGRATIVE PLANT BIOLOGY 2022; 64:2217-2239. [PMID: 36478523 DOI: 10.1111/jipb.13423] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/07/2022] [Accepted: 12/05/2022] [Indexed: 06/17/2023]
Abstract
Maintaining proper DNA methylation levels in the genome requires active demethylation of DNA. However, removing the methyl group from a modified cytosine is chemically difficult and therefore, the underlying mechanism of demethylation had remained unclear for many years. The discovery of the first eukaryotic DNA demethylase, Arabidopsis thaliana REPRESSOR OF SILENCING 1 (ROS1), led to elucidation of the 5-methylcytosine base excision repair mechanism of active DNA demethylation. In the 20 years since ROS1 was discovered, our understanding of this active DNA demethylation pathway, as well as its regulation and biological functions in plants, has greatly expanded. These exciting developments have laid the groundwork for further dissecting the regulatory mechanisms of active DNA demethylation, with potential applications in epigenome editing to facilitate crop breeding and gene therapy.
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Affiliation(s)
- Heng Zhang
- State Key Laboratory of Molecular Plant Genetics, Shanghai Centre for Plant Stress Biology, Centre for Excellence in Molecular Plant Sciences, Chinese Academy of Sciences, Shanghai, 200032, China
| | - Zhizhong Gong
- State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, China Agricultural University, Beijing, 100193, China
- School of Life Sciences, Institute of Life Science and Green Development, Hebei University, Baoding, 071002, China
| | - Jian-Kang Zhu
- School of Life Sciences, Institute of Advanced Biotechnology, Southern University of Science and Technology, Shenzhen, 518055, China
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6
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Montgomery SA, Berger F. The evolution of imprinting in plants: beyond the seed. PLANT REPRODUCTION 2021; 34:373-383. [PMID: 33914165 PMCID: PMC8566399 DOI: 10.1007/s00497-021-00410-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/01/2021] [Accepted: 04/12/2021] [Indexed: 05/14/2023]
Abstract
Genomic imprinting results in the biased expression of alleles depending on if the allele was inherited from the mother or the father. Despite the prevalence of sexual reproduction across eukaryotes, imprinting is only found in placental mammals, flowering plants, and some insects, suggesting independent evolutionary origins. Numerous hypotheses have been proposed to explain the selective pressures that favour the innovation of imprinted gene expression and each differs in their experimental support and predictions. Due to the lack of investigation of imprinting in land plants, other than angiosperms with triploid endosperm, we do not know whether imprinting occurs in species lacking endosperm and with embryos developing on maternal plants. Here, we discuss the potential for uncovering additional examples of imprinting in land plants and how these observations may provide additional support for one or more existing imprinting hypotheses.
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Affiliation(s)
- Sean A Montgomery
- Gregor Mendel Institute (GMI), Austrian Academy of Sciences, Vienna BioCenter (VBC), Dr. Bohr Gasse 3, 1030, Vienna, Austria
| | - Frédéric Berger
- Gregor Mendel Institute (GMI), Austrian Academy of Sciences, Vienna BioCenter (VBC), Dr. Bohr Gasse 3, 1030, Vienna, Austria.
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7
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Widespread imprinting of transposable elements and variable genes in the maize endosperm. PLoS Genet 2021; 17:e1009491. [PMID: 33830994 PMCID: PMC8057601 DOI: 10.1371/journal.pgen.1009491] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2020] [Revised: 04/20/2021] [Accepted: 03/15/2021] [Indexed: 11/19/2022] Open
Abstract
Fertilization and seed development is a critical time in the plant life cycle, and coordinated development of the embryo and endosperm are required to produce a viable seed. In the endosperm, some genes show imprinted expression where transcripts are derived primarily from one parental genome. Imprinted gene expression has been observed across many flowering plant species, though only a small proportion of genes are imprinted. Understanding how imprinted expression arises has been complicated by the reliance on single nucleotide polymorphisms between alleles to enable testing for imprinting. Here, we develop a method to use whole genome assemblies of multiple genotypes to assess for imprinting of both shared and variable portions of the genome using data from reciprocal crosses. This reveals widespread maternal expression of genes and transposable elements with presence-absence variation within maize and across species. Most maternally expressed features are expressed primarily in the endosperm, suggesting that maternal de-repression in the central cell facilitates expression. Furthermore, maternally expressed TEs are enriched for maternal expression of the nearest gene, and read alignments over maternal TE-gene pairs indicate that these are fused rather than independent transcripts.
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Anderson SN, Zhou P, Higgins K, Brandvain Y, Springer NM. Widespread imprinting of transposable elements and variable genes in the maize endosperm. PLoS Genet 2021. [PMID: 33830994 DOI: 10.1371/journal.pgen.100949] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/22/2023] Open
Abstract
Fertilization and seed development is a critical time in the plant life cycle, and coordinated development of the embryo and endosperm are required to produce a viable seed. In the endosperm, some genes show imprinted expression where transcripts are derived primarily from one parental genome. Imprinted gene expression has been observed across many flowering plant species, though only a small proportion of genes are imprinted. Understanding how imprinted expression arises has been complicated by the reliance on single nucleotide polymorphisms between alleles to enable testing for imprinting. Here, we develop a method to use whole genome assemblies of multiple genotypes to assess for imprinting of both shared and variable portions of the genome using data from reciprocal crosses. This reveals widespread maternal expression of genes and transposable elements with presence-absence variation within maize and across species. Most maternally expressed features are expressed primarily in the endosperm, suggesting that maternal de-repression in the central cell facilitates expression. Furthermore, maternally expressed TEs are enriched for maternal expression of the nearest gene, and read alignments over maternal TE-gene pairs indicate that these are fused rather than independent transcripts.
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Affiliation(s)
- Sarah N Anderson
- Department of Genetics, Development, and Cell Biology; Iowa State University; Ames, Iowa, United States of America
| | - Peng Zhou
- Department of Plant and Microbial Biology; University of Minnesota; St. Paul, Minnesota, United States of America
| | - Kaitlin Higgins
- Department of Genetics, Development, and Cell Biology; Iowa State University; Ames, Iowa, United States of America
| | - Yaniv Brandvain
- Department of Plant and Microbial Biology; University of Minnesota; St. Paul, Minnesota, United States of America
| | - Nathan M Springer
- Department of Plant and Microbial Biology; University of Minnesota; St. Paul, Minnesota, United States of America
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Tonosaki K, Ono A, Kunisada M, Nishino M, Nagata H, Sakamoto S, Kijima ST, Furuumi H, Nonomura KI, Sato Y, Ohme-Takagi M, Endo M, Comai L, Hatakeyama K, Kawakatsu T, Kinoshita T. Mutation of the imprinted gene OsEMF2a induces autonomous endosperm development and delayed cellularization in rice. THE PLANT CELL 2021; 33:85-103. [PMID: 33751094 PMCID: PMC8136911 DOI: 10.1093/plcell/koaa006] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/16/2020] [Accepted: 10/29/2020] [Indexed: 05/22/2023]
Abstract
In angiosperms, endosperm development comprises a series of developmental transitions controlled by genetic and epigenetic mechanisms that are initiated after double fertilization. Polycomb repressive complex 2 (PRC2) is a key component of these mechanisms that mediate histone H3 lysine 27 trimethylation (H3K27me3); the action of PRC2 is well described in Arabidopsis thaliana but remains uncertain in cereals. In this study, we demonstrate that mutation of the rice (Oryza sativa) gene EMBRYONIC FLOWER2a (OsEMF2a), encoding a zinc-finger containing component of PRC2, causes an autonomous endosperm phenotype involving proliferation of the central cell nuclei with separate cytoplasmic domains, even in the absence of fertilization. Detailed cytological and transcriptomic analyses revealed that the autonomous endosperm can produce storage compounds, starch granules, and protein bodies specific to the endosperm. These events have not been reported in Arabidopsis. After fertilization, we observed an abnormally delayed developmental transition in the endosperm. Transcriptome and H3K27me3 ChIP-seq analyses using endosperm from the emf2a mutant identified downstream targets of PRC2. These included >100 transcription factor genes such as type-I MADS-box genes, which are likely required for endosperm development. Our results demonstrate that OsEMF2a-containing PRC2 controls endosperm developmental programs before and after fertilization.
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Affiliation(s)
- Kaoru Tonosaki
- Kihara Institute for Biological Research, Yokohama City University, 641-12 Maioka, Totsuka, Yokohama, Kanagawa 244-0813, Japan
- Department of Plant Biology and Genome Center, University of California, Davis, CA 95616, USA
- Faculty of Agriculture, Iwate University, 3-18-8 Ueda, Morioka, Iwate 020-8550, Japan
- Author for correspondence: (T.Ki.), (K.T.)
| | - Akemi Ono
- Kihara Institute for Biological Research, Yokohama City University, 641-12 Maioka, Totsuka, Yokohama, Kanagawa 244-0813, Japan
| | - Megumi Kunisada
- Kihara Institute for Biological Research, Yokohama City University, 641-12 Maioka, Totsuka, Yokohama, Kanagawa 244-0813, Japan
| | - Megumi Nishino
- Kihara Institute for Biological Research, Yokohama City University, 641-12 Maioka, Totsuka, Yokohama, Kanagawa 244-0813, Japan
| | - Hiroki Nagata
- Kihara Institute for Biological Research, Yokohama City University, 641-12 Maioka, Totsuka, Yokohama, Kanagawa 244-0813, Japan
| | - Shingo Sakamoto
- Bioproduction Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Central 6, Higashi 1-1-1, Tsukuba, Ibaraki 305-8562, Japan
| | - Saku T Kijima
- Bioproduction Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Central 6, Higashi 1-1-1, Tsukuba, Ibaraki 305-8562, Japan
| | - Hiroyasu Furuumi
- Genetic Strains Research Center, National Institute of Genetics, Mishima, Shizuoka 411-8540, Japan
| | - Ken-Ichi Nonomura
- Plant Cytogenetics, National Institute of Genetics, Mishima, Shizuoka 411-8540, Japan
| | - Yutaka Sato
- Genetic Strains Research Center, National Institute of Genetics, Mishima, Shizuoka 411-8540, Japan
| | - Masaru Ohme-Takagi
- Graduate School of Science and Engineering, Saitama University, 255 Shimo-Okubo, Sakura-ku, Saitama 338-8570, Japan
| | - Masaki Endo
- Division of Applied Genetics, Institute of Agrobiological Sciences, National Agriculture and Food Research Organization, Tsukuba, Ibaraki 305-8602, Japan
| | - Luca Comai
- Department of Plant Biology and Genome Center, University of California, Davis, CA 95616, USA
| | - Katsunori Hatakeyama
- Faculty of Agriculture, Iwate University, 3-18-8 Ueda, Morioka, Iwate 020-8550, Japan
| | - Taiji Kawakatsu
- Division of Biotechnology, Institute of Agrobiological Sciences, National Agriculture and Food Research Organization, Tsukuba, Ibaraki 305-8602, Japan
| | - Tetsu Kinoshita
- Kihara Institute for Biological Research, Yokohama City University, 641-12 Maioka, Totsuka, Yokohama, Kanagawa 244-0813, Japan
- Author for correspondence: (T.Ki.), (K.T.)
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10
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Rong H, Yang W, Zhu H, Jiang B, Jiang J, Wang Y. Genomic imprinted genes in reciprocal hybrid endosperm of Brassica napus. BMC PLANT BIOLOGY 2021; 21:140. [PMID: 33726676 PMCID: PMC7968328 DOI: 10.1186/s12870-021-02908-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/12/2020] [Accepted: 02/28/2021] [Indexed: 05/06/2023]
Abstract
BACKGROUND Genomic imprinting results in the expression of parent-of-origin-specific alleles in the offspring. Brassica napus is an oil crop with research values in polyploidization. Identification of imprinted genes in B. napus will enrich the knowledge of genomic imprinting in dicotyledon plants. RESULTS In this study, we performed reciprocal crosses between B. napus L. cultivars Yangyou 6 (Y6) and Zhongshuang 11 (ZS11) to collect endosperm at 20 and 25 days after pollination (DAP) for RNA-seq. In total, we identified 297 imprinted genes, including 283 maternal expressed genes (MEGs) and 14 paternal expressed genes (PEGs) according to the SNPs between Y6 and ZS11. Only 36 genes (35 MEGs and 1 PEG) were continuously imprinted in 20 and 25 DAP endosperm. We found 15, 2, 5, 3, 10, and 25 imprinted genes in this study were also imprinted in Arabidopsis, rice, castor bean, maize, B. rapa, and other B. napus lines, respectively. Only 26 imprinted genes were specifically expressed in endosperm, while other genes were also expressed in root, stem, leaf and flower bud of B. napus. A total of 109 imprinted genes were clustered on rapeseed chromosomes. We found the LTR/Copia transposable elements (TEs) were most enriched in both upstream and downstream of the imprinted genes, and the TEs enriched around imprinted genes were more than non-imprinted genes. Moreover, the expression of 5 AGLs and 6 pectin-related genes in hybrid endosperm were significantly changed comparing with that in parent endosperm. CONCLUSION This research provided a comprehensive identification of imprinted genes in B. napus, and enriched the gene imprinting in dicotyledon plants, which would be useful in further researches on how gene imprinting regulates seed development.
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Affiliation(s)
- Hao Rong
- Jiangsu Provincial Key Laboratory of Crop Genetics and Physiology, Yangzhou University, Yangzhou, 225009 China
| | - Wenjing Yang
- Jiangsu Provincial Key Laboratory of Crop Genetics and Physiology, Yangzhou University, Yangzhou, 225009 China
| | - Haotian Zhu
- Jiangsu Provincial Key Laboratory of Crop Genetics and Physiology, Yangzhou University, Yangzhou, 225009 China
| | - Bo Jiang
- Jiangsu Provincial Key Laboratory of Crop Genetics and Physiology, Yangzhou University, Yangzhou, 225009 China
| | - Jinjin Jiang
- Jiangsu Provincial Key Laboratory of Crop Genetics and Physiology, Yangzhou University, Yangzhou, 225009 China
| | - Youping Wang
- Jiangsu Provincial Key Laboratory of Crop Genetics and Physiology, Yangzhou University, Yangzhou, 225009 China
- Joint International Research Laboratory of Agriculture and Agri-Product Safety, the Ministry of Education of China, Yangzhou, 225009 China
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11
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Tuteja R, McKeown PC, Ryan P, Morgan CC, Donoghue MTA, Downing T, O'Connell MJ, Spillane C. Paternally Expressed Imprinted Genes under Positive Darwinian Selection in Arabidopsis thaliana. Mol Biol Evol 2019; 36:1239-1253. [PMID: 30913563 PMCID: PMC6526901 DOI: 10.1093/molbev/msz063] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Genomic imprinting is an epigenetic phenomenon where autosomal genes display uniparental expression depending on whether they are maternally or paternally inherited. Genomic imprinting can arise from parental conflicts over resource allocation to the offspring, which could drive imprinted loci to evolve by positive selection. We investigate whether positive selection is associated with genomic imprinting in the inbreeding species Arabidopsis thaliana. Our analysis of 140 genes regulated by genomic imprinting in the A. thaliana seed endosperm demonstrates they are evolving more rapidly than expected. To investigate whether positive selection drives this evolutionary acceleration, we identified orthologs of each imprinted gene across 34 plant species and elucidated their evolutionary trajectories. Increased positive selection was sought by comparing its incidence among imprinted genes with nonimprinted controls. Strikingly, we find a statistically significant enrichment of imprinted paternally expressed genes (iPEGs) evolving under positive selection, 50.6% of the total, but no such enrichment for positive selection among imprinted maternally expressed genes (iMEGs). This suggests that maternally- and paternally expressed imprinted genes are subject to different selective pressures. Almost all positively selected amino acids were fixed across 80 sequenced A. thaliana accessions, suggestive of selective sweeps in the A. thaliana lineage. The imprinted genes under positive selection are involved in processes important for seed development including auxin biosynthesis and epigenetic regulation. Our findings support a genomic imprinting model for plants where positive selection can affect paternally expressed genes due to continued conflict with maternal sporophyte tissues, even when parental conflict is reduced in predominantly inbreeding species.
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Affiliation(s)
- Reetu Tuteja
- Genetics & Biotechnology Lab, Plant & AgriBiosciences Research Centre (PABC), School of Natural Sciences, Ryan Institute, National University of Ireland Galway, Galway, Ireland.,Center for Genomics and Systems Biology, New York University, New York, NY
| | - Peter C McKeown
- Genetics & Biotechnology Lab, Plant & AgriBiosciences Research Centre (PABC), School of Natural Sciences, Ryan Institute, National University of Ireland Galway, Galway, Ireland
| | - Pat Ryan
- Genetics & Biotechnology Lab, Plant & AgriBiosciences Research Centre (PABC), School of Natural Sciences, Ryan Institute, National University of Ireland Galway, Galway, Ireland
| | - Claire C Morgan
- School of Biotechnology, Faculty of Biological Sciences, Dublin City University, Dublin, Ireland.,Division of Diabetes, Endocrinology and Metabolism, Imperial College London, London, United Kingdom
| | - Mark T A Donoghue
- Genetics & Biotechnology Lab, Plant & AgriBiosciences Research Centre (PABC), School of Natural Sciences, Ryan Institute, National University of Ireland Galway, Galway, Ireland.,Memorial Sloan Kettering Cancer Center, New York, NY
| | - Tim Downing
- School of Biotechnology, Faculty of Biological Sciences, Dublin City University, Dublin, Ireland
| | - Mary J O'Connell
- Computational and Molecular Evolutionary Biology Research Group, School of Biology, Faculty of Biological Sciences, The University of Leeds, Leeds, United Kingdom.,Computational and Molecular Evolutionary Biology Group, School of Life Sciences, University of Nottingham, Nottingham, United Kingdom
| | - Charles Spillane
- Genetics & Biotechnology Lab, Plant & AgriBiosciences Research Centre (PABC), School of Natural Sciences, Ryan Institute, National University of Ireland Galway, Galway, Ireland
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