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Khouider S, Gehring M. Parental dialectic: Epigenetic conversations in endosperm. CURRENT OPINION IN PLANT BIOLOGY 2024; 81:102591. [PMID: 38944896 DOI: 10.1016/j.pbi.2024.102591] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/17/2024] [Revised: 05/21/2024] [Accepted: 06/07/2024] [Indexed: 07/02/2024]
Abstract
Endosperm is a major evolutionary innovation of flowering plants, and its proper development critically impacts seed growth and viability. Epigenetic regulators have a key function in parental control of endosperm development. Notably, epigenetic regulation of parental genome dosage is a major determinant of seed development success, and disruption of this balance can produce inviable seed, as observed in some interploidy and interspecific crosses. These postzygotic reproduction barriers are also a potent driver of speciation. The molecular machinery and regulatory architecture governing endosperm development is proposed to have evolved under parental conflict. In this review, we emphasize parental conflict as a dialectic conflict and discuss recent findings about the epigenetic molecular machinery that mediates parental conflict in the endosperm.
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Affiliation(s)
- Souraya Khouider
- Whitehead Institute for Biomedical Research, Cambridge MA 02142, USA
| | - Mary Gehring
- Whitehead Institute for Biomedical Research, Cambridge MA 02142, USA; Department of Biology, Massachusetts Institute of Technology, Cambridge MA 02139, USA.
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2
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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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3
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Soliman HK, Coughlan JM. United by Conflict: Convergent Signatures of Parental Conflict in Angiosperms and Placental Mammals. J Hered 2024:esae009. [PMID: 38366852 DOI: 10.1093/jhered/esae009] [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: 10/31/2023] [Indexed: 02/18/2024] Open
Abstract
Endosperm in angiosperms and placenta in eutherians are convergent innovations for efficient embryonic nutrient transfer. Despite advantages, this reproductive strategy incurs metabolic costs that maternal parents disproportionately shoulder, leading to potential inter-parental conflict over optimal offspring investment. Genomic imprinting-parent-of-origin-biased gene expression-is fundamental for endosperm and placenta development and has convergently evolved in angiosperms and mammals, in part, to resolve parental conflict. Here, we review the mechanisms of genomic imprinting in these taxa. Despite differences in the timing and spatial extent of imprinting, these taxa exhibit remarkable convergence in the molecular machinery and genes governing imprinting. We then assess the role of parental conflict in shaping evolution within angiosperms and eutherians using four criteria: (1) Do differences in the extent of sibling relatedness cause differences in the inferred strength of parental conflict? (2) Do reciprocal crosses between taxa with different inferred histories of parental conflict exhibit parent-of-origin growth effects? (3) Are these parent-of-origin growth effects caused by dosage-sensitive mechanisms and do these loci exhibit signals of positive selection? (4) Can normal development be restored by genomic perturbations that restore stoichiometric balance in the endosperm/placenta? Although we find evidence for all criteria in angiosperms and eutherians, suggesting that parental conflict may help shape their evolution, many questions remain. Additionally, myriad differences between the two taxa suggest that their respective biologies may shape how/when/where/to what extent parental conflict manifests. Lastly, we discuss outstanding questions, highlighting the power of comparative work in quantifying the role of parental conflict in evolution.
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Affiliation(s)
- Hagar K Soliman
- Department of Ecology & Evolutionary Biology, Yale University, New Haven, CT, 06511, United States
- Department of Biotechnology, Faculty of Science, Cairo University, Giza, 12613, Egypt
| | - Jenn M Coughlan
- Department of Ecology & Evolutionary Biology, Yale University, New Haven, CT, 06511, United States
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Coughlan JM. The role of hybrid seed inviability in angiosperm speciation. AMERICAN JOURNAL OF BOTANY 2023; 110:1-14. [PMID: 36801827 DOI: 10.1002/ajb2.16135] [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: 08/27/2022] [Revised: 01/05/2023] [Accepted: 01/05/2023] [Indexed: 05/11/2023]
Abstract
Understanding which reproductive barriers contribute to speciation is essential to understanding the diversity of life on earth. Several contemporary examples of strong hybrid seed inviability (HSI) between recently diverged species suggest that HSI may play a fundamental role in plant speciation. Yet, a broader synthesis of HSI is needed to clarify its role in diversification. Here, I review the incidence and evolution of HSI. Hybrid seed inviability is common and evolves rapidly, suggesting that it may play an important role early in speciation. The developmental mechanisms that underlie HSI involve similar developmental trajectories in endosperm, even between evolutionarily deeply diverged incidents of HSI. In hybrid endosperm, HSI is often accompanied by whole-scale gene misexpression, including misexpression of imprinted genes which have a key role in endosperm development. I explore how an evolutionary perspective can clarify the repeated and rapid evolution of HSI. In particular, I evaluate the evidence for conflict between maternal and paternal interests in resource allocation to offspring (i.e., parental conflict). I highlight that parental conflict theory generates explicit predictions regarding the expected hybrid phenotypes and genes responsible for HSI. While much phenotypic evidence supports a role of parental conflict in the evolution of HSI, an understanding of the underlying molecular mechanisms of this barrier is essential to test parental conflict theory. Lastly, I explore what factors may influence the strength of parental conflict in natural plant populations as an explanation for why rates of HSI may differ between plant groups and the consequences of strong HSI in secondary contact.
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Affiliation(s)
- Jenn M Coughlan
- Department of Ecology and Evolutionary Biology, Yale University, New Haven, CT, 06511, USA
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5
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Jia Z, Gao P, Yin F, Quilichini TD, Sheng H, Song J, Yang H, Gao J, Chen T, Yang B, Kochian LV, Zou J, Patterson N, Yang Q, Gillmor CS, Datla R, Li Q, Xiang D. Asymmetric gene expression in grain development of reciprocal crosses between tetraploid and hexaploid wheats. Commun Biol 2022; 5:1412. [PMID: 36564439 PMCID: PMC9789062 DOI: 10.1038/s42003-022-04374-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2022] [Accepted: 12/13/2022] [Indexed: 12/24/2022] Open
Abstract
Production of viable progeny from interploid crosses requires precise regulation of gene expression from maternal and paternal chromosomes, yet the transcripts contributed to hybrid seeds from polyploid parent species have rarely been explored. To investigate the genome-wide maternal and paternal contributions to polyploid grain development, we analyzed the transcriptomes of developing embryos, from zygote to maturity, alongside endosperm in two stages of development, using reciprocal crosses between tetraploid and hexaploid wheats. Reciprocal crosses between species with varied levels of ploidy displayed broad impacts on gene expression, including shifts in alternative splicing events in select crosses, as illustrated by active splicing events, enhanced protein synthesis and chromatin remodeling. Homoeologous gene expression was repressed on the univalent D genome in pentaploids, but this suppression was attenuated in crosses with a higher ploidy maternal parent. Imprinted genes were identified in endosperm and early embryo tissues, supporting predominant maternal effects on early embryogenesis. By systematically investigating the complex transcriptional networks in reciprocal-cross hybrids, this study presents a framework for understanding the genomic incompatibility and transcriptome shock that results from interspecific hybridization and uncovers the transcriptional impacts on hybrid seeds created from agriculturally-relevant polyploid species.
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Affiliation(s)
- Zhen Jia
- grid.35155.370000 0004 1790 4137National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, 430070 Wuhan, China
| | - Peng Gao
- grid.25152.310000 0001 2154 235XGlobal Institute for Food Security, University of Saskatchewan, Saskatoon, SK S7N 4J8 Canada
| | - Feifan Yin
- grid.35155.370000 0004 1790 4137National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, 430070 Wuhan, China ,grid.35155.370000 0004 1790 4137Hubei Key Laboratory of Agricultural Bioinformatics, College of Informatics, Huazhong Agricultural University, 430070 Wuhan, China
| | - Teagen D. Quilichini
- grid.24433.320000 0004 0449 7958Aquatic and Crop Resource Development, National Research Council Canada, 110 Gymnasium Place, Saskatoon, SK S7N 0W9 Canada
| | - Huajin Sheng
- grid.25152.310000 0001 2154 235XGlobal Institute for Food Security, University of Saskatchewan, Saskatoon, SK S7N 4J8 Canada
| | - Jingpu Song
- grid.24433.320000 0004 0449 7958Aquatic and Crop Resource Development, National Research Council Canada, 110 Gymnasium Place, Saskatoon, SK S7N 0W9 Canada
| | - Hui Yang
- grid.24433.320000 0004 0449 7958Aquatic and Crop Resource Development, National Research Council Canada, 110 Gymnasium Place, Saskatoon, SK S7N 0W9 Canada
| | - Jie Gao
- grid.35155.370000 0004 1790 4137National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, 430070 Wuhan, China
| | - Ting Chen
- grid.35155.370000 0004 1790 4137National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, 430070 Wuhan, China
| | - Bo Yang
- grid.35155.370000 0004 1790 4137National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, 430070 Wuhan, China
| | - Leon V. Kochian
- grid.25152.310000 0001 2154 235XGlobal Institute for Food Security, University of Saskatchewan, Saskatoon, SK S7N 4J8 Canada
| | - Jitao Zou
- grid.24433.320000 0004 0449 7958Aquatic and Crop Resource Development, National Research Council Canada, 110 Gymnasium Place, Saskatoon, SK S7N 0W9 Canada
| | - Nii Patterson
- grid.24433.320000 0004 0449 7958Aquatic and Crop Resource Development, National Research Council Canada, 110 Gymnasium Place, Saskatoon, SK S7N 0W9 Canada
| | - Qingyong Yang
- grid.35155.370000 0004 1790 4137National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, 430070 Wuhan, China ,grid.35155.370000 0004 1790 4137Hubei Key Laboratory of Agricultural Bioinformatics, College of Informatics, Huazhong Agricultural University, 430070 Wuhan, China
| | - C. Stewart Gillmor
- grid.512574.0Langebio, Unidad de Genómica Avanzada, Centro de Investigación y Estudios Avanzados del IPN (CINVESTAV-IPN), Irapuato, Guanajuato, 36821 México
| | - Raju Datla
- grid.25152.310000 0001 2154 235XGlobal Institute for Food Security, University of Saskatchewan, Saskatoon, SK S7N 4J8 Canada
| | - Qiang Li
- grid.35155.370000 0004 1790 4137National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, 430070 Wuhan, China
| | - Daoquan Xiang
- grid.24433.320000 0004 0449 7958Aquatic and Crop Resource Development, National Research Council Canada, 110 Gymnasium Place, Saskatoon, SK S7N 0W9 Canada
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6
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Ågren JA, Patten MM. Genetic conflicts and the case for licensed anthropomorphizing. Behav Ecol Sociobiol 2022; 76:166. [DOI: 10.1007/s00265-022-03267-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2022] [Revised: 11/05/2022] [Accepted: 11/08/2022] [Indexed: 12/02/2022]
Abstract
Abstract
The use of intentional language in biology is controversial. It has been commonly applied by researchers in behavioral ecology, who have not shied away from employing agential thinking or even anthropomorphisms, but has been rarer among researchers from more mechanistic corners of the discipline, such as population genetics. One research area where these traditions come into contact—and occasionally clash—is the study of genetic conflicts, and its history offers a good window to the debate over the use of intentional language in biology. We review this debate, paying particular attention to how this interaction has played out in work on genomic imprinting and sex chromosomes. In light of this, we advocate for a synthesis of the two approaches, a form of licensed anthropomorphizing. Here, agential thinking’s creative potential and its ability to identify the fulcrum of evolutionary pressure are combined with the rigidity of formal mathematical modeling.
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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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Picard CL, Povilus RA, Williams BP, Gehring M. Transcriptional and imprinting complexity in Arabidopsis seeds at single-nucleus resolution. NATURE PLANTS 2021; 7:730-738. [PMID: 34059805 PMCID: PMC8217372 DOI: 10.1038/s41477-021-00922-0] [Citation(s) in RCA: 35] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/04/2020] [Accepted: 04/15/2021] [Indexed: 05/06/2023]
Abstract
Seeds are a key life cycle stage for many plants. Seeds are also the basis of agriculture and the primary source of calories consumed by humans1. Here, we employ single-nucleus RNA-sequencing to generate a transcriptional atlas of developing Arabidopsis thaliana seeds, with a focus on endosperm. Endosperm, the primary site of gene imprinting in flowering plants, mediates the relationship between the maternal parent and the embryo2. We identify transcriptionally uncharacterized nuclei types in the chalazal endosperm, which interfaces with maternal tissue for nutrient unloading3,4. We demonstrate that the extent of parental bias of maternally expressed imprinted genes varies with cell-cycle phase, and that imprinting of paternally expressed imprinted genes is strongest in chalazal endosperm. Thus, imprinting is spatially and temporally heterogeneous. Increased paternal expression in the chalazal region suggests that parental conflict, which is proposed to drive imprinting evolution, is fiercest at the boundary between filial and maternal tissues.
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Affiliation(s)
- Colette L Picard
- Whitehead Institute for Biomedical Research, Cambridge, MA, USA
- Computational and Systems Biology Graduate Program, Massachusetts Institute of Technology, Cambridge, MA, USA
| | | | - Ben P Williams
- Whitehead Institute for Biomedical Research, Cambridge, MA, USA
| | - Mary Gehring
- Whitehead Institute for Biomedical Research, Cambridge, MA, USA.
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA, USA.
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9
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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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10
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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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Liu Y, Jing X, Zhang H, Xiong J, Qiao Y. Identification of Imprinted Genes Based on Homology: An Example of Fragaria vesca. Genes (Basel) 2021; 12:genes12030380. [PMID: 33800118 PMCID: PMC7999015 DOI: 10.3390/genes12030380] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2021] [Revised: 02/28/2021] [Accepted: 03/04/2021] [Indexed: 01/04/2023] Open
Abstract
Genomic imprinting has drawn increasing attention in plant biology in recent years. At present, hundreds of imprinted genes have been identified in various plants, and some of them have been reported to be evolutionarily conserved in plant species. In this research, 17 candidate genes in Fragaria vesca were obtained based on the homologous imprinted genes in Arabidopsis thaliana and other species. We further constructed reciprocal crosses of diploid strawberry (F. vesca) using the varieties 10-41 and 18-86 as the parents to investigate the conservation of these imprinted genes. Potentially informative single nucleotide polymorphisms (SNPs) were used as molecular markers of two parents obtained from candidate imprinted genes which have been cloned and sequenced. Meanwhile, we analyzed the SNP site variation ratios and parent-of-origin expression patterns of candidate imprinted genes at 10 days after pollination (DAP) endosperm and embryo for the hybrids of reciprocal cross, respectively. A total of five maternally expressed genes (MEGs), i.e., FvARI8, FvKHDP-2, FvDRIP2, FvBRO1, and FvLTP3, were identified in the endosperm, which did not show imprinting in the embryo. Finally, tissues expression analysis indicated that the five imprinted genes excluding FvDRIP2 mainly expressed in the endosperm. This is the first report on imprinted genes of Fragaria, and we provide a simple and rapid method based on homologous conservation to screen imprinted genes. The present study will provide a basis for further study of function and mechanism of genomic imprinting in F. vesca.
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