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Somers J, Nelms B. The sporophyte-to-gametophyte transition: The haploid generation comes of age. CURRENT OPINION IN PLANT BIOLOGY 2023; 75:102416. [PMID: 37441836 DOI: 10.1016/j.pbi.2023.102416] [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: 04/19/2023] [Revised: 06/02/2023] [Accepted: 06/14/2023] [Indexed: 07/15/2023]
Abstract
Flowering plants alternate between two multicellular generations: the diploid sporophyte and haploid gametophyte. Despite its small size, the gametophyte has significant impacts on plant genetics, evolution, and breeding. Each male pollen grain and female embryo sac is a multicellular organism with independent gene expression, a functioning metabolism, and specialized cell types. In this review, we describe recent progress in understanding the process in which the haploid genome takes over expression from its diploid parent - the sporophyte-to-gametophyte transition. The focus is on pollen, but similar concepts may also apply to the female gametophyte. Technological advances in single-cell genomics offer the opportunity to characterize haploid gene expression in unprecedented detail, positioning the field to make rapid progress.
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Affiliation(s)
- Julian Somers
- Department of Plant Biology, University of Georgia, Athens, GA 30602, USA
| | - Brad Nelms
- Department of Plant Biology, University of Georgia, Athens, GA 30602, USA.
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2
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Chen Y, Xie D, Ma X, Xue X, Liu M, Xiao X, Lai C, Xu X, Chen X, Chen Y, Zhang Z, XuHan X, Lai Z, Lin Y. Genome-wide high-throughput chromosome conformation capture analysis reveals hierarchical chromatin interactions during early somatic embryogenesis. PLANT PHYSIOLOGY 2023; 193:555-577. [PMID: 37313777 DOI: 10.1093/plphys/kiad348] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/23/2023] [Revised: 05/04/2023] [Accepted: 05/23/2023] [Indexed: 06/15/2023]
Abstract
Somatic embryogenesis (SE), like zygotic embryo development, is a progressive process. Early SE is the beginning of a switch from a somatic to an embryogenic state and is an important stage for initiating chromatin reprogramming of SE. Previous studies suggest that changes in chromatin accessibility occur during early SE, although information on the 3D structure of chromatin is not yet available. Here, we present a chromosome-level genome assembly of longan (Dimocarpus longan) using PacBio combined with high-through chromosome conformation capture scaffolding, which resulted in a 446 Mb genome assembly anchored onto 15 scaffolds. During early SE, chromatin was concentrated and then decondensed, and a large number of long terminal repeat retrotransposons (LTR-RTs) were enriched in the local chromatin interaction region, suggesting LTR-RTs were involved in chromatin reorganization. Early SE was accompanied by the transformation from A to B compartments, and the interactions between B compartments were enhanced. Results from chromatin accessibility, monomethylation of histone H3 at lysine 4 (H3K4me1) modification, and transcription analyses further revealed a gene regulatory network for cell wall thickening during SE. Particularly, we found that the H3K4me1 differential peak binding motif showed abnormal activation of ethylene response factor transcription factors and participation in SE. The chromosome-level genomic and multiomics analyses revealed the 3D conformation of chromatin during early SE, providing insight into the molecular mechanisms underlying cell wall thickening and the potential regulatory networks of TFs during early SE in D. longan. These results provide additional clues for revealing the molecular mechanisms of plant SE.
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Affiliation(s)
- Yan Chen
- Institute of Horticultural Biotechnology, Fujian Agriculture and Forestry University, Fuzhou, Fujian 350002, China
| | - Dejian Xie
- Beijing Research Center, Wuhan Frasergen Bioinformatics Co., Ltd, Beijing 100081, China
| | - Xiangwei Ma
- Institute of Horticultural Biotechnology, Fujian Agriculture and Forestry University, Fuzhou, Fujian 350002, China
| | - Xiaodong Xue
- Institute of Horticultural Biotechnology, Fujian Agriculture and Forestry University, Fuzhou, Fujian 350002, China
| | - Mengyu Liu
- Institute of Horticultural Biotechnology, Fujian Agriculture and Forestry University, Fuzhou, Fujian 350002, China
| | - Xuechen Xiao
- Institute of Horticultural Biotechnology, Fujian Agriculture and Forestry University, Fuzhou, Fujian 350002, China
| | - Chunwang Lai
- Institute of Horticultural Biotechnology, Fujian Agriculture and Forestry University, Fuzhou, Fujian 350002, China
| | - Xiaoping Xu
- Institute of Horticultural Biotechnology, Fujian Agriculture and Forestry University, Fuzhou, Fujian 350002, China
| | - Xiaohui Chen
- Institute of Horticultural Biotechnology, Fujian Agriculture and Forestry University, Fuzhou, Fujian 350002, China
| | - Yukun Chen
- Institute of Horticultural Biotechnology, Fujian Agriculture and Forestry University, Fuzhou, Fujian 350002, China
| | - Zihao Zhang
- Institute of Horticultural Biotechnology, Fujian Agriculture and Forestry University, Fuzhou, Fujian 350002, China
| | - Xu XuHan
- Institute of Horticultural Biotechnology, Fujian Agriculture and Forestry University, Fuzhou, Fujian 350002, China
- Institut de la Recherche Interdisciplinaire de Toulouse, IRIT-ARI, Toulouse 31300, France
| | - Zhongxiong Lai
- Institute of Horticultural Biotechnology, Fujian Agriculture and Forestry University, Fuzhou, Fujian 350002, China
| | - Yuling Lin
- Institute of Horticultural Biotechnology, Fujian Agriculture and Forestry University, Fuzhou, Fujian 350002, China
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Alaniz-Fabián J, Orozco-Nieto A, Abreu-Goodger C, Gillmor CS. Hybridization alters maternal and paternal genome contributions to early plant embryogenesis. Development 2022; 149:281772. [PMID: 36314727 DOI: 10.1242/dev.201025] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2022] [Accepted: 10/17/2022] [Indexed: 11/06/2022]
Abstract
After fertilization, zygotic genome activation results in a transcriptionally competent embryo. Hybrid transcriptome experiments in Arabidopsis have concluded that the maternal and paternal genomes make equal contributions to zygotes and embryos, yet embryo defective (emb) mutants in the Columbia (Col) ecotype display early maternal effects. Here, we show that hybridization of Col with Landsberg erecta (Ler) or Cape Verde Islands (Cvi) ecotypes decreases the maternal effects of emb mutants. Reanalysis of Col/Ler and Col/Cvi transcriptomes confirmed equal parental contributions in Col/Cvi early embryos. By contrast, thousands of genes in Col/Ler zygotes and one-cell embryos were biallelic in one cross and monoallelic in the reciprocal cross, with analysis of intron reads pointing to active transcription as responsible for this parent-of-origin bias. Our analysis shows that, contrary to previous conclusions, the maternal and paternal genomes in Col/Ler zygotes are activated in an asymmetric manner. The decrease in maternal effects in hybrid embryos compared with those in isogenic Col along with differences in genome activation between Col/Cvi and Col/Ler suggest that neither of these hybrids accurately reflects the general trends of parent-of-origin regulation in Arabidopsis embryogenesis.
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Affiliation(s)
- Jaime Alaniz-Fabián
- Langebio, Unidad de Genómica Avanzada, CINVESTAV-IPN, Irapuato 36824, México
| | - Axel Orozco-Nieto
- Langebio, Unidad de Genómica Avanzada, CINVESTAV-IPN, Irapuato 36824, México
| | - Cei Abreu-Goodger
- Institute of Ecology and Evolution, School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3FL, UK
| | - C Stewart Gillmor
- Langebio, Unidad de Genómica Avanzada, CINVESTAV-IPN, Irapuato 36824, México
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Armenta-Medina A, Gillmor CS, Gao P, Mora-Macias J, Kochian LV, Xiang D, Datla R. Developmental and genomic architecture of plant embryogenesis: from model plant to crops. PLANT COMMUNICATIONS 2021; 2:100136. [PMID: 33511346 PMCID: PMC7816075 DOI: 10.1016/j.xplc.2020.100136] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/12/2020] [Revised: 12/05/2020] [Accepted: 12/11/2020] [Indexed: 05/08/2023]
Abstract
Embryonic development represents an important reproductive phase of sexually reproducing plant species. The fusion of egg and sperm produces the plant zygote, a totipotent cell that, through cell division and cell identity specification in early embryogenesis, establishes the major cell lineages and tissues of the adult plant. The subsequent morphogenesis phase produces the full-sized embryo, while the late embryogenesis maturation process prepares the seed for dormancy and subsequent germination, ensuring continuation of the plant life cycle. In this review on embryogenesis, we compare the model eudicot Arabidopsis thaliana with monocot crops, focusing on genome activation, paternal and maternal regulation of early zygote development, and key organizers of patterning, such as auxin and WOX transcription factors. While the early stages of embryo development are apparently conserved among plant species, embryo maturation programs have diversified between eudicots and monocots. This diversification in crop species reflects the likely effects of domestication on seed quality traits that are determined during embryo maturation, and also assures seed germination in different environmental conditions. This review describes the most important features of embryonic development in plants, and the scope and applications of genomics in plant embryo studies.
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Affiliation(s)
- Alma Armenta-Medina
- Global Institute for Food Security, University of Saskatchewan, Saskatoon, SK S7N 4J8, Canada
- Laboratorio Nacional de Genómica para la Biodiversidad (Langebio), Unidad de Genómica Avanzada, Centro de Investigación y Estudios Avanzados del IPN (CINVESTAV-IPN), Irapuato, Guanajuato, México
| | - C. Stewart Gillmor
- Laboratorio Nacional de Genómica para la Biodiversidad (Langebio), Unidad de Genómica Avanzada, Centro de Investigación y Estudios Avanzados del IPN (CINVESTAV-IPN), Irapuato, Guanajuato, México
| | - Peng Gao
- Global Institute for Food Security, University of Saskatchewan, Saskatoon, SK S7N 4J8, Canada
| | - Javier Mora-Macias
- Global Institute for Food Security, University of Saskatchewan, Saskatoon, SK S7N 4J8, Canada
| | - Leon V. Kochian
- Global Institute for Food Security, University of Saskatchewan, Saskatoon, SK S7N 4J8, Canada
| | - Daoquan Xiang
- National Research Council Canada, 110 Gymnasium Place, Saskatoon, SK S7N 0W9, Canada
| | - Raju Datla
- Global Institute for Food Security, University of Saskatchewan, Saskatoon, SK S7N 4J8, Canada
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Zhao P, Zhou X, Zheng Y, Ren Y, Sun MX. Equal parental contribution to the transcriptome is not equal control of embryogenesis. NATURE PLANTS 2020; 6:1354-1364. [PMID: 33106635 DOI: 10.1038/s41477-020-00793-x] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/30/2020] [Accepted: 09/16/2020] [Indexed: 05/06/2023]
Abstract
In animals, early embryogenesis is maternally controlled, whereas in plants, parents contribute equally to the proembryo transcriptome. Thus, the question remains whether equivalent parental contribution to the transcriptome of the early proembryo means equal control of early embryogenesis. Here, on the basis of cell-lineage-specific and allele-specific transcriptome analysis, we reveal that paternal and maternal genomes contribute equally to the transcriptomes of both the apical cell lineage and the basal cell lineage of early proembryos. However, a strong maternal effect on basal cell lineage development was found, indicating that equal parental contribution to the transcriptome is not necessarily coupled with equivalent parental control of proembryonic development. Parental contributions to embryogenesis therefore cannot be concluded solely on the basis of the ratio of paternal/maternal transcripts. Furthermore, we demonstrate that parent-of-origin genes display developmental-stage-dependent and cell-lineage-dependent allelic expression patterns. These findings will facilitate the investigation of specific parental roles in specific processes of early embryogenesis.
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Affiliation(s)
- Peng Zhao
- State Key Laboratory of Hybrid Rice, College of Life Sciences, Wuhan University, Wuhan, China.
| | - Xuemei Zhou
- State Key Laboratory of Hybrid Rice, College of Life Sciences, Wuhan University, Wuhan, China
- College of Life Sciences, South-Central University for Nationalities, Wuhan, China
| | - Yifan Zheng
- State Key Laboratory of Hybrid Rice, College of Life Sciences, Wuhan University, Wuhan, China
| | - Yanru Ren
- State Key Laboratory of Hybrid Rice, College of Life Sciences, Wuhan University, Wuhan, China
| | - Meng-Xiang Sun
- State Key Laboratory of Hybrid Rice, College of Life Sciences, Wuhan University, Wuhan, China.
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Abstract
In higher plants, fertilization induces many structural and physiological changes in the fertilized egg that reflect the transition from the haploid female gamete to the diploid zygote - the first cell of the sporophyte. After fusion of the egg nucleus with the sperm nucleus, many molecular changes occur in the zygote during the process of zygote activation during embryogenesis. The zygote originates from the egg, from which some pre-stored translation initiation factors transfer into the zygote and function during zygote activation. This indicates that the control of zygote activation is pre-set in the egg. After the egg and sperm nuclei fuse, gene expression is activated in the zygote, and paternal and maternal gene expression patterns are displayed. This highlights the diversity of zygotic genome activation in higher plants. In addition to new gene expression in the zygote, some genes show quantitative changes in expression. The asymmetrical division of the zygote produces an apical cell and a basal cell that have different destinies during plant reconstruction; these destinies are determined in the zygote. This review describes significant advances in research on the mechanisms controlling zygote activation in higher plants.
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Wang K, Chen H, Miao Y, Bayer M. Square one: zygote polarity and early embryogenesis in flowering plants. CURRENT OPINION IN PLANT BIOLOGY 2020; 53:128-133. [PMID: 31727540 DOI: 10.1016/j.pbi.2019.10.002] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/16/2019] [Revised: 09/27/2019] [Accepted: 10/07/2019] [Indexed: 06/10/2023]
Abstract
In the last two decades, work on auxin signaling has helped to understand many aspects of the fundamental process underlying the specification of tissue types in the plant embryo. However, the immediate steps after fertilization including the polarization of the zygote and the initial body axis formation remained poorly understood. Valuable insight into these enigmatic processes has been gained by studying fertilization in grasses. Recent technical advances in transcriptomics of developing embryos with high spatial and temporal resolution give an emerging picture of the rapid changes of the zygotic developmental program. Together with the use of live imaging of novel fluorescent marker lines, these data are now the basis of unraveling the very first steps of the embryonic patterning process.
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Affiliation(s)
- Kai Wang
- Max Planck Institute for Developmental Biology, Department of Cell Biology, Max-Planck-Ring 5, 72076 Tübingen, Germany
| | - Houming Chen
- Max Planck Institute for Developmental Biology, Department of Cell Biology, Max-Planck-Ring 5, 72076 Tübingen, Germany
| | - Yingjing Miao
- Max Planck Institute for Developmental Biology, Department of Cell Biology, Max-Planck-Ring 5, 72076 Tübingen, Germany
| | - Martin Bayer
- Max Planck Institute for Developmental Biology, Department of Cell Biology, Max-Planck-Ring 5, 72076 Tübingen, Germany.
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Zhao P, Zhou X, Shen K, Liu Z, Cheng T, Liu D, Cheng Y, Peng X, Sun MX. Two-Step Maternal-to-Zygotic Transition with Two-Phase Parental Genome Contributions. Dev Cell 2019; 49:882-893.e5. [DOI: 10.1016/j.devcel.2019.04.016] [Citation(s) in RCA: 38] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2018] [Revised: 02/13/2019] [Accepted: 04/11/2019] [Indexed: 10/26/2022]
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9
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Armenta-Medina A, Gillmor CS. Genetic, molecular and parent-of-origin regulation of early embryogenesis in flowering plants. Curr Top Dev Biol 2019; 131:497-543. [DOI: 10.1016/bs.ctdb.2018.11.008] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/05/2022]
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10
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Anderson SN, Johnson CS, Chesnut J, Jones DS, Khanday I, Woodhouse M, Li C, Conrad LJ, Russell SD, Sundaresan V. The Zygotic Transition Is Initiated in Unicellular Plant Zygotes with Asymmetric Activation of Parental Genomes. Dev Cell 2017; 43:349-358.e4. [DOI: 10.1016/j.devcel.2017.10.005] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2017] [Revised: 08/15/2017] [Accepted: 10/05/2017] [Indexed: 10/18/2022]
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Palovaara J, de Zeeuw T, Weijers D. Tissue and Organ Initiation in the Plant Embryo: A First Time for Everything. Annu Rev Cell Dev Biol 2016; 32:47-75. [PMID: 27576120 DOI: 10.1146/annurev-cellbio-111315-124929] [Citation(s) in RCA: 63] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Land plants can grow to tremendous body sizes, yet even the most complex architectures are the result of iterations of the same developmental processes: organ initiation, growth, and pattern formation. A central question in plant biology is how these processes are regulated and coordinated to allow for the formation of ordered, 3D structures. All these elementary processes first occur in early embryogenesis, during which, from a fertilized egg cell, precursors for all major tissues and stem cells are initiated, followed by tissue growth and patterning. Here we discuss recent progress in our understanding of this phase of plant life. We consider the cellular basis for multicellular development in 3D and focus on the genetic regulatory mechanisms that direct specific steps during early embryogenesis.
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Affiliation(s)
- Joakim Palovaara
- Laboratory of Biochemistry, Wageningen University, 6703 HA Wageningen, The Netherlands;
| | - Thijs de Zeeuw
- Laboratory of Biochemistry, Wageningen University, 6703 HA Wageningen, The Netherlands;
| | - Dolf Weijers
- Laboratory of Biochemistry, Wageningen University, 6703 HA Wageningen, The Netherlands;
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Parent-of-Origin-Effect rough endosperm Mutants in Maize. Genetics 2016; 204:221-31. [PMID: 27440865 DOI: 10.1534/genetics.116.191775] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2016] [Accepted: 07/12/2016] [Indexed: 01/06/2023] Open
Abstract
Parent-of-origin-effect loci have non-Mendelian inheritance in which phenotypes are determined by either the maternal or paternal allele alone. In angiosperms, parent-of-origin effects can be caused by loci required for gametophyte development or by imprinted genes needed for seed development. Few parent-of-origin-effect loci have been identified in maize (Zea mays) even though there are a large number of imprinted genes known from transcriptomics. We screened rough endosperm (rgh) mutants for parent-of-origin effects using reciprocal crosses with inbred parents. Six maternal rough endosperm (mre) and three paternal rough endosperm (pre) mutants were identified with three mre loci mapped. When inherited from the female parent, mre/+ seeds reduce grain fill with a rough, etched, or pitted endosperm surface. Pollen transmission of pre mutants results in rgh endosperm as well as embryo lethality. Eight of the mutants had significant distortion from the expected one-to-one ratio for parent-of-origin effects. Linked markers for mre1, mre2, and mre3 indicated that the mutant alleles have no bias in transmission. Histological analysis of mre1, mre2, mre3, and pre*-949 showed altered timing of starch grain accumulation and basal endosperm transfer cell layer (BETL) development. The mre1 locus delays BETL and starchy endosperm development, while mre2 and pre*-949 cause ectopic starchy endosperm differentiation. We conclude that many parent-of-origin effects in maize have incomplete penetrance of kernel phenotypes and that there is a large diversity of endosperm developmental roles for parent-of-origin-effect loci.
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