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Zhong S, Zhao P, Peng X, Li HJ, Duan Q, Cheung AY. From gametes to zygote: Mechanistic advances and emerging possibilities in plant reproduction. Plant Physiol 2024; 195:4-35. [PMID: 38431529 PMCID: PMC11060694 DOI: 10.1093/plphys/kiae125] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/12/2023] [Revised: 02/13/2024] [Accepted: 02/13/2024] [Indexed: 03/05/2024]
Affiliation(s)
- Sheng Zhong
- State Key Laboratory for Protein and Plant Gene Research, Peking-Tsinghua Center for Life Sciences, New Cornerstone Science Laboratory, College of Life Sciences, Peking University, Beijing 100871, China
| | - Peng Zhao
- State Key Laboratory of Hybrid Rice, College of Life Sciences, Wuhan University, Wuhan 430072, China
- Hubei Hongshan Laboratory, Wuhan 430070, China
| | - Xiongbo Peng
- State Key Laboratory of Hybrid Rice, College of Life Sciences, Wuhan University, Wuhan 430072, China
- Hubei Hongshan Laboratory, Wuhan 430070, China
| | - Hong-Ju Li
- Key Laboratory of Seed Innovation, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Center for Molecular Agrobiology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China
| | - Qiaohong Duan
- College of Horticulture Science and Engineering, Shandong Agricultural University, Tai’an, Shandong 271018, China
| | - Alice Y Cheung
- Department of Biochemistry and Molecular Biology, Molecular and Cellular Biology Program, Plant Biology Graduate Program, University of Massachusetts, Amherst, MA 01003, USA
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2
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Vijverberg K, Ozias-Akins P, Schranz ME. Identifying and Engineering Genes for Parthenogenesis in Plants. Front Plant Sci 2019; 10:128. [PMID: 30838007 PMCID: PMC6389702 DOI: 10.3389/fpls.2019.00128] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/15/2018] [Accepted: 01/24/2019] [Indexed: 05/16/2023]
Abstract
Parthenogenesis is the spontaneous development of an embryo from an unfertilized egg cell. It naturally occurs in a variety of plant and animal species. In plants, parthenogenesis usually is found in combination with apomeiosis (the omission of meiosis) and pseudogamous or autonomous (with or without central cell fertilization) endosperm formation, together known as apomixis (clonal seed production). The initiation of embryogenesis in vivo and in vitro has high potential in plant breeding methods, particularly for the instant production of homozygous lines from haploid gametes [doubled haploids (DHs)], the maintenance of vigorous F1-hybrids through clonal seed production after combining it with apomeiosis, reverse breeding approaches, and for linking diploid and polyploid gene pools. Because of this large interest, efforts to identify gene(s) for parthenogenesis from natural apomicts have been undertaken by using map-based cloning strategies and comparative gene expression studies. In addition, engineering parthenogenesis in sexual model species has been investigated via mutagenesis and gain-of-function strategies. These efforts have started to pay off, particularly by the isolation of the PsASGR-BabyBoom-Like from apomictic Pennisetum, a gene proven to be transferable to and functional in sexual pearl millet, rice, and maize. This review aims to summarize the current knowledge on parthenogenesis, the possible gene candidates also outside the grasses, and the use of these genes in plant breeding protocols. It shows that parthenogenesis is able to inherit and function independently from apomeiosis and endosperm formation, is expressed and active in the egg cell, and can induce embryogenesis in polyploid, diploid as well as haploid egg cells in plants. It also shows the importance of genes involved in the suppression of transcription and modifications thereof at one hand, and in embryogenesis for which transcription is allowed or artificially overexpressed on the other, in parthenogenetic reproduction. Finally, it emphasizes the importance of functional endosperm to allow for successful embryo growth and viable seed production.
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Affiliation(s)
- Kitty Vijverberg
- Biosystematics Group, Experimental Plant Sciences, Wageningen University and Research, Wageningen, Netherlands
- *Correspondence: Kitty Vijverberg,
| | - Peggy Ozias-Akins
- Department of Horticulture, Institute of Plant Breeding, Genetics and Genomics, University of Georgia, Tifton Campus, Tifton, GA, United States
| | - M. Eric Schranz
- Biosystematics Group, Experimental Plant Sciences, Wageningen University and Research, Wageningen, Netherlands
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Abstract
The haploid female gametophyte (embryo sac) is an essential reproductive unit of flowering plants, usually comprising four specialized cell types, including the female gametes (egg cell and central cell). The differentiation of these cells relies on spatial signals which pattern the gametophyte along a proximal-distal axis, but the molecular and genetic mechanisms by which cell identities are determined in the embryo sac have long been a mystery. Recent identification of key genes for cell fate specification and their relationship to hormonal signaling pathways that act on positional cues has provided new insights into these processes. A model for differentiation can be devised with egg cell fate as a default state of the female gametophyte and with other cell types specified by the action of spatially regulated factors. Cell-to-cell communication within the gametophyte is also important for maintaining cell identity as well as facilitating fertilization of the female gametes by the male gametes (sperm cells).
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Affiliation(s)
- Debra J Skinner
- Department of Plant Biology, University of California-Davis, Davis, USA
| | - Venkatesan Sundaresan
- Department of Plant Biology, University of California-Davis, Davis, USA.,Department of Plant Sciences, University of California-Davis, Davis, USA
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4
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Tedeschi F, Rizzo P, Rutten T, Altschmied L, Bäumlein H. RWP-RK domain-containing transcription factors control cell differentiation during female gametophyte development in Arabidopsis. New Phytol 2017; 213:1909-1924. [PMID: 27870062 DOI: 10.1111/nph.14293] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/06/2016] [Accepted: 09/17/2016] [Indexed: 05/02/2023]
Abstract
The formation of gametes is a prerequisite for any sexually reproducing organism in order to complete its life cycle. In plants, female gametes are formed in a multicellular tissue, the female gametophyte or embryo sac. Although the events leading to the formation of the female gametophyte have been morphologically characterized, the molecular control of embryo sac development remains elusive. We used single and double mutants as well as cell-specific marker lines to characterize a novel class of gene regulators in Arabidopsis thaliana, the RWP-RK domain-containing (RKD) transcription factors. Morphological and histological analyses were conducted using confocal laser scanning and differential interference contrast microscopy. Gene expression and transcriptome analyses were performed using quantitative reverse transcription-PCR and RNA sequencing, respectively. Our results showed that RKD genes are expressed during distinct stages of embryo sac development. Morphological analysis of the mutants revealed severe distortions in gametophyte polarity and cell differentiation. Transcriptome analysis revealed changes in the expression of several gametophyte-specific gene families (RKD2 and RKD3) and ovule development-specific genes (RKD3), and identified pleiotropic effects on phytohormone pathways (RKD5). Our data provide novel insight into the regulatory control of female gametophyte development. RKDs are involved in the control of cell differentiation and are required for normal gametophytic development.
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Affiliation(s)
- Francesca Tedeschi
- Department of Molecular Genetics, Leibniz Institute of Plant Genetics and Crop Plant Research (IPK), D-06466, Seeland, OT Gatersleben, Germany
| | - Paride Rizzo
- Department of Molecular Genetics, Leibniz Institute of Plant Genetics and Crop Plant Research (IPK), D-06466, Seeland, OT Gatersleben, Germany
| | - Twan Rutten
- Department of Physiology and Cell Biology, Leibniz Institute of Plant Genetics and Crop Plant Research (IPK), D-06466, Seeland, OT Gatersleben, Germany
| | - Lothar Altschmied
- Department of Molecular Genetics, Leibniz Institute of Plant Genetics and Crop Plant Research (IPK), D-06466, Seeland, OT Gatersleben, Germany
| | - Helmut Bäumlein
- Department of Molecular Genetics, Leibniz Institute of Plant Genetics and Crop Plant Research (IPK), D-06466, Seeland, OT Gatersleben, Germany
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5
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Kumlehn J. Embryogenesis and Plant Regeneration from Isolated Wheat Zygotes. Methods Mol Biol 2016; 1359:503-14. [PMID: 26619884 DOI: 10.1007/978-1-4939-3061-6_29] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/18/2023]
Abstract
Wheat zygotes can be mechanically isolated and cultivated to continue their development in vitro. Since each zygote needs to be individually isolated, only relatively few of these cells are available per experiment. To facilitate embryonic growth despite of this limitation, the zygotes are kept within a culture insert placed in a larger dish which itself contains embryogenic pollen cocultivated for continuous medium conditioning. This setup ensures that the two cultures, while being physically separated from one another, can exchange essential intercellular signal molecules passing through the bottom of the insert which is made of a permeable membrane. Thanks to the natural fate of zygotes, which is to form an embryo followed by the generation of a plant, embryogenesis and plant regeneration are achieved at much higher efficiency as compared to other single-cell systems. While the method is largely independent of the genotype, it allows for the nondestructive observation, manipulation, and individual analysis of zygotes and very young embryos.
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Lippmann R, Friedel S, Mock HP, Kumlehn J. The low molecular weight fraction of compounds released from immature wheat pistils supports barley pollen embryogenesis. Front Plant Sci 2015; 6:498. [PMID: 26217352 PMCID: PMC4493395 DOI: 10.3389/fpls.2015.00498] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/24/2015] [Accepted: 06/22/2015] [Indexed: 05/05/2023]
Abstract
Pollen embryogenesis provides a useful means of generating haploid plants for plant breeding and basic research. Although it is well-established that the efficacy of the process can be enhanced by the provision of immature pistils as a nurse tissue, the origin and compound class of the signal molecule(s) involved is still elusive. Here, a micro-culture system was established to enable the culturing of populations of barley pollen at a density too low to allow unaided embryogenesis to occur, and this was then exploited to assess the effect of using various parts of the pistil as nurse tissue. A five-fold increase in the number of embryogenic calli formed was obtained by simply cutting the pistils in half. The effectiveness of the pistil-conditioned medium was transitory, since it needed replacement at least every 4 days to measurably ensure embryogenic development. The differential effect of various size classes of compounds present in the pistil-conditioned medium showed that the relevant molecule(s) was of molecular weight below 3 kDa. This work narrows down possible feeder molecules to lower molecular weight compounds and showed that the cellular origin of the active compound(s) is not specific to any tested part of the pistil. Furthermore, the increased recovery of calli during treatment with cut pistils may provide a useful tool for plant breeders and researchers using haploid technology in barley and other plant species.
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Affiliation(s)
| | | | | | - Jochen Kumlehn
- Leibniz Institute of Plant Genetics and Crop Plant Research (IPK)Gatersleben, Germany
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7
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Ronceret A, Vielle-Calzada JP. Meiosis, unreduced gametes, and parthenogenesis: implications for engineering clonal seed formation in crops. Plant Reprod 2015; 28:91-102. [PMID: 25796397 DOI: 10.1007/s00497-015-0262-6] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/09/2014] [Accepted: 03/09/2015] [Indexed: 05/18/2023]
Abstract
Meiosis and unreduced gametes. Sexual flowering plants produce meiotically derived cells that give rise to the male and female haploid gametophytic phase. In the ovule, usually a single precursor (the megaspore mother cell) undergoes meiosis to form four haploid megaspores; however, numerous mutants result in the formation of unreduced gametes, sometimes showing female specificity, a phenomenon reminiscent of the initiation of gametophytic apomixis. Here, we review the developmental events that occur during female meiosis and megasporogenesis at the light of current possibilities to engineer unreduced gamete formation. We also provide an overview of the current understanding of mechanisms leading to parthenogenesis and discuss some of the conceptual implications for attempting the induction of clonal seed production in cultivated plants.
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Affiliation(s)
- Arnaud Ronceret
- Group of Reproductive Development and Apomixis, UGA Laboratorio Nacional de Genómica para la Biodiversidad, CINVESTAV Irapuato, Km 9.6 Libramiento Norte Carretera Irapuato-León, CP 36821, Irapuato, Guanajuato, Mexico
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8
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Fehér A. Somatic embryogenesis - Stress-induced remodeling of plant cell fate. Biochim Biophys Acta 2015; 1849:385-402. [PMID: 25038583 DOI: 10.1016/j.bbagrm.2014.07.005] [Citation(s) in RCA: 208] [Impact Index Per Article: 20.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/26/2014] [Revised: 07/08/2014] [Accepted: 07/10/2014] [Indexed: 01/13/2023]
Abstract
Plants as sessile organisms have remarkable developmental plasticity ensuring heir continuous adaptation to the environment. An extreme example is somatic embryogenesis, the initiation of autonomous embryo development in somatic cells in response to exogenous and/or endogenous signals. In this review I briefly overview the various pathways that can lead to embryo development in plants in addition to the fertilization of the egg cell and highlight the importance of the interaction of stress- and hormone-regulated pathways during the induction of somatic embryogenesis. Somatic embryogenesis can be initiated in planta or in vitro, directly or indirectly, and the requirement for dedifferentiation as well as the way to achieve developmental totipotency in the various systems is discussed in light of our present knowledge. The initiation of all forms of the stress/hormone-induced in vitro as well as the genetically provoked in planta somatic embryogenesis requires extensive and coordinated genetic reprogramming that has to take place at the chromatin level, as the embryogenic program is under strong epigenetic repression in vegetative plant cells. Our present knowledge on chromatin-based mechanisms potentially involved in the somatic-to-embryogenic developmental transition is summarized emphasizing the potential role of the chromatin to integrate stress, hormonal, and developmental pathways leading to the activation of the embryogenic program. The role of stress-related chromatin reorganization in the genetic instability of in vitro cultures is also discussed. This article is part of a Special Issue entitled: Stress as a fundamental theme in cell plasticity.
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Domoki M, Szűcs A, Jäger K, Bottka S, Barnabás B, Fehér A. Identification of genes preferentially expressed in wheat egg cells and zygotes. Plant Cell Rep 2013; 32:339-48. [PMID: 23160639 DOI: 10.1007/s00299-012-1367-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/25/2012] [Revised: 09/28/2012] [Accepted: 10/31/2012] [Indexed: 05/14/2023]
Abstract
KEY MESSAGE : Wheat genes differentially expressed in the egg cell before and after fertilization were identified. The data support zygotic gene activation before the first cell division in wheat. To have an insight into fertilization-induced gene expression, cDNA libraries have been prepared from isolated wheat egg cells and one-celled zygotes. Two-hundred and twenty-six egg cell and 253 zygote-expressed EST sequences were determined. Most of the represented transcripts were detected in the wheat egg cell or zygote transcriptome at the first time. Expression analysis of fourteen of the identified genes and three controls was carried out by real-time quantitative PCR. The preferential expression of all investigated genes in the female gametophyte-derived samples (egg cells, zygotes, two-celled proembryos, and basal ovule parts with synergids) in comparison to the anthers, and the leaves were verified. Three genes with putative signaling/regulatory functions were expressed at a low level in the egg cell but exhibited increased (2-to-33-fold) relative expression in the zygote and the proembryo. Genes with high EST abundance in cDNA libraries exhibited strong expression in the egg cell and the zygote, while the ones coding for unknown or hypothetical proteins exhibited differential expression patterns with preferential transcript accumulation in egg cells and/or zygotes. The obtained data support the activation of the zygotic genome before the first cell division in wheat.
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Affiliation(s)
- Mónika Domoki
- Biological Research Centre, Institute of Plant Biology, Hungarian Academy of Sciences, Temesvári krt. 62, Szeged, 6726, Hungary
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Wuest SE, Schmid MW, Grossniklaus U. Cell-specific expression profiling of rare cell types as exemplified by its impact on our understanding of female gametophyte development. Curr Opin Plant Biol 2013; 16:41-9. [PMID: 23276786 DOI: 10.1016/j.pbi.2012.12.001] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/15/2012] [Accepted: 12/03/2012] [Indexed: 05/20/2023]
Abstract
Expression profiling of single cells can yield insights into cell specification, cellular differentiation processes, and cell type-specific responses to environmental stimuli. Recent work has established excellent tools to perform genome-wide expression studies of individual cell types, even if the cells of interest occur at low frequency within an organ. We review the advances and impact of gene expression studies of rare cell types, as exemplified by recently gained insights into the development and function of the angiosperm female gametophyte. The detailed transcriptional characterization of different stages during female gametophyte development has significantly helped to improve our understanding of cellular specification or cell-cell communication processes. Next-generation sequencing approaches--used increasingly for expression profiling--will now allow for comparative approaches that focus on agriculturally, ecologically or evolutionarily relevant aspects of plant reproduction.
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Affiliation(s)
- Samuel E Wuest
- Institute of Evolutionary Biology and Environmental Studies & Zürich-Basel Plant Science Center, University of Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland
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11
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Schmidt A, Schmid MW, Grossniklaus U. Analysis of plant germline development by high-throughput RNA profiling: technical advances and new insights. Plant J 2012; 70:18-29. [PMID: 22449040 DOI: 10.1111/j.1365-313x.2012.04897.x] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Reproduction is a crucial step in the life cycle of plants. The male and female germline lineages develop in the reproductive organs of the flower, which in higher plants are the anthers and ovules, respectively. Development of the germline lineage initiates from a dedicated sporophytic cell that undergoes meiosis to form spores that subsequently give rise to the gametophytes through mitotic cell divisions. The mature male and female gametophytes harbour the male (sperm cells) and female gametes (egg and central cell), respectively. Those unite during double fertilization to initiate embryo and endosperm development in sexually reproducing higher plants. While cytological changes involved in development of the germline lineages have been well characterized in a number of species, investigation of the transcriptional basis underlying their development and the specification of the gametes proved challenging. This is largely due to the inaccessibility of the cells constituting the germline lineages, which are enclosed by sporophytic tissues. Only recently, these technical limitations could be overcome by combining new methods to isolate the relevant cells with powerful transcriptional profiling methods, such as microarrays or high-throughput sequencing of RNA. This review focuses on these technical advances and the new insights gained from them concerning the transcriptional basis and molecular mechanisms underlying germline development.
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Affiliation(s)
- Anja Schmidt
- Institute of Plant Biology and Zürich-Basel Plant Science Center, University of Zürich, Zollikerstrasse 107, Zürich, Switzerland.
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12
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Koszegi D, Johnston AJ, Rutten T, Czihal A, Altschmied L, Kumlehn J, Wüst SEJ, Kirioukhova O, Gheyselinck J, Grossniklaus U, Bäumlein H. Members of the RKD transcription factor family induce an egg cell-like gene expression program. Plant J 2011; 67:280-91. [PMID: 21457369 DOI: 10.1111/j.1365-313x.2011.04592.x] [Citation(s) in RCA: 81] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
In contrast to animals, the life cycle of higher plants alternates between a gamete-producing (gametophyte) and a spore-producing (sporophyte) generation. The female gametophyte of angiosperms consists of four distinct cell types, including two gametes, the egg and the central cell, which give rise to embryo and endosperm, respectively. Based on a combined subtractive hybridization and virtual subtraction approach in wheat (Triticum aestivum L.), we have isolated a class of transcription factors not found in animal genomes, the RKD (RWP-RK domain-containing) factors, which share a highly conserved RWP-RK domain. Single-cell RT-PCR revealed that the genes TaRKD1 and TaRKD2 are preferentially expressed in the egg cell of wheat. The Arabidopsis genome contains five RKD genes, at least two of them, AtRKD1 and AtRKD2, are preferentially expressed in the egg cell of Arabidopsis. Ectopic expression of the AtRKD1 and AtRKD2 genes induces cell proliferation and the expression of an egg cell marker. Analyses of RKD-induced proliferating cells exhibit a shift of gene expression towards an egg cell-like transcriptome. Promoters of selected RKD-induced genes were shown to be predominantly active in the egg cell and can be activated by RKD in a transient protoplast expression assay. The data show that egg cell-specific RKD factors control a transcriptional program, which is characteristic for plant egg cells.
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Affiliation(s)
- Dávid Koszegi
- Leibniz Institute of Plant Genetics and Crop Plant Research (IPK), Gatersleben, Germany
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Marshall E, Costa LM, Gutierrez-Marcos J. Cysteine-rich peptides (CRPs) mediate diverse aspects of cell-cell communication in plant reproduction and development. J Exp Bot 2011; 62:1677-86. [PMID: 21317212 DOI: 10.1093/jxb/err002] [Citation(s) in RCA: 82] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/19/2023]
Abstract
Cell-cell communication in plants is essential for the correct co-ordination of reproduction, growth, and development. Studies to dissect this mode of communication have previously focussed primarily on the action of plant hormones as mediators of intercellular signalling. In animals, peptide signalling is a well-documented intercellular communication system, however, relatively little is known about this system in plants. In recent years, numerous reports have emerged about small, secreted peptides controlling different aspects of plant reproduction. Interestingly, most of these peptides are cysteine-rich, and there is convincing evidence suggesting multiple roles for related cysteine-rich peptides (CRPs) as signalling factors in developmental patterning as well as during plant pathogen responses and symbiosis. In this review, we discuss how CRPs are emerging as key signalling factors in regulating multiple aspects of vegetative growth and reproductive development in plants.
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Affiliation(s)
- Eleanor Marshall
- School of Life Sciences, University of Warwick, Wellesbourne Campus, Wellesbourne, UK
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14
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Hu T, Yu M, Zhao J. Techniques of cell type-specific transcriptome analysis and applications in researches of sexual plant reproduction. ACTA ACUST UNITED AC 2011; 6:31-9. [DOI: 10.1007/s11515-011-1090-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
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Hu TX, Yu M, Zhao J. Comparative transcriptional profiling analysis of the two daughter cells from tobacco zygote reveals the transcriptome differences in the apical and basal cells. BMC Plant Biol 2010; 10:167. [PMID: 20699003 PMCID: PMC3095300 DOI: 10.1186/1471-2229-10-167] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/28/2010] [Accepted: 08/11/2010] [Indexed: 05/19/2023]
Abstract
BACKGROUND In angiosperm, after the first asymmetric zygotic cell division, the apical and basal daughter cells follow distinct development pathways. Global transcriptome analysis of these two cells is essential in understanding their developmental differences. However, because of the difficulty to isolate the in vivo apical and basal cells of two-celled proembryo from ovule and ovary in higher plants, the transcriptome analysis of them hasn't been reported. RESULTS In this study, we developed a procedure for isolating the in vivo apical and basal cells of the two-celled proembryo from tobacco (Nicotiana tabacum), and then performed a comparative transcriptome analysis of the two cells by suppression subtractive hybridization (SSH) combined with macroarray screening. After sequencing, we identified 797 differentially expressed ESTs corresponding to 299 unigenes. Library sequence analysis successfully identified tobacco homologies of genes involved in embryogenesis and seed development. By quantitative real-time PCR, we validated the differential expression of 40 genes, with 6 transcripts of them specifically expressed in the apical or basal cell. Expression analysis also revealed some transcripts displayed cell specific activation in one of the daughter cells after zygote division. These differential expressions were further validated by in situ hybridization (ISH). Tissue expression pattern analysis also revealed some potential roles of these candidate genes in development. CONCLUSIONS The results show that some differential or specific transcripts in the apical and basal cells of two-celled proembryo were successfully isolated, and the identification of these transcripts reveals that these two daughter cells possess distinct transcriptional profiles after zygote division. Further functional work on these differentially or specifically expressed genes will promote the elucidation of molecular mechanism controlling early embryogenesis.
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Affiliation(s)
- Tian-Xiang Hu
- Key Laboratory of the Ministry of Education for Plant Developmental Biology, College of Life Sciences, Wuhan University, Wuhan 430072, China
| | - Miao Yu
- Key Laboratory of the Ministry of Education for Plant Developmental Biology, College of Life Sciences, Wuhan University, Wuhan 430072, China
| | - Jie Zhao
- Key Laboratory of the Ministry of Education for Plant Developmental Biology, College of Life Sciences, Wuhan University, Wuhan 430072, China
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16
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Wang D, Zhang C, Hearn DJ, Kang IH, Punwani JA, Skaggs MI, Drews GN, Schumaker KS, Yadegari R. Identification of transcription-factor genes expressed in the Arabidopsis female gametophyte. BMC Plant Biol 2010; 10:110. [PMID: 20550711 PMCID: PMC3236301 DOI: 10.1186/1471-2229-10-110] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/11/2009] [Accepted: 06/16/2010] [Indexed: 05/04/2023]
Abstract
BACKGROUND In flowering plants, the female gametophyte is typically a seven-celled structure with four cell types: the egg cell, the central cell, the synergid cells, and the antipodal cells. These cells perform essential functions required for double fertilization and early seed development. Differentiation of these distinct cell types likely involves coordinated changes in gene expression regulated by transcription factors. Therefore, understanding female gametophyte cell differentiation and function will require dissection of the gene regulatory networks operating in each of the cell types. These efforts have been hampered because few transcription factor genes expressed in the female gametophyte have been identified. To identify such genes, we undertook a large-scale differential expression screen followed by promoter-fusion analysis to detect transcription-factor genes transcribed in the Arabidopsis female gametophyte. RESULTS Using quantitative reverse-transcriptase PCR, we analyzed 1,482 Arabidopsis transcription-factor genes and identified 26 genes exhibiting reduced mRNA levels in determinate infertile 1 mutant ovaries, which lack female gametophytes, relative to ovaries containing female gametophytes. Spatial patterns of gene transcription within the mature female gametophyte were identified for 17 transcription-factor genes using promoter-fusion analysis. Of these, ten genes were predominantly expressed in a single cell type of the female gametophyte including the egg cell, central cell and the antipodal cells whereas the remaining seven genes were expressed in two or more cell types. After fertilization, 12 genes were transcriptionally active in the developing embryo and/or endosperm. CONCLUSIONS We have shown that our quantitative reverse-transcriptase PCR differential-expression screen is sufficiently sensitive to detect transcription-factor genes transcribed in the female gametophyte. Most of the genes identified in this study have not been reported previously as being expressed in the female gametophyte. Therefore, they might represent novel regulators and provide entry points for reverse genetic and molecular approaches to uncover the gene regulatory networks underlying female gametophyte development.
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Affiliation(s)
- Dongfang Wang
- School of Plant Sciences, University of Arizona, Tucson, Arizona 85721-0036, USA
| | - Changqing Zhang
- School of Plant Sciences, University of Arizona, Tucson, Arizona 85721-0036, USA
- Current Address: The Section of Molecular, Cell and Developmental Biology, University of Texas at Austin, Austin, Texas 78712-0159, USA
| | - David J Hearn
- School of Plant Sciences, University of Arizona, Tucson, Arizona 85721-0036, USA
- Current Address: Department of Biological Sciences, Towson University, Towson, Maryland 21252-0001, USA
| | - Il-Ho Kang
- School of Plant Sciences, University of Arizona, Tucson, Arizona 85721-0036, USA
- Department of Biology, University of Utah, Salt Lake City, Utah 84112-0840, USA
- Current Address: Department of Horticulture, Iowa State University, Ames, Iowa 50011-1100, USA
| | - Jayson A Punwani
- Department of Biology, University of Utah, Salt Lake City, Utah 84112-0840, USA
- Current Address: Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3280, USA
| | - Megan I Skaggs
- School of Plant Sciences, University of Arizona, Tucson, Arizona 85721-0036, USA
| | - Gary N Drews
- Department of Biology, University of Utah, Salt Lake City, Utah 84112-0840, USA
| | - Karen S Schumaker
- School of Plant Sciences, University of Arizona, Tucson, Arizona 85721-0036, USA
| | - Ramin Yadegari
- School of Plant Sciences, University of Arizona, Tucson, Arizona 85721-0036, USA
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Pulido A, Bakos F, Devic M, Barnabás B, Olmedilla A. HvPG1 and ECA1: two genes activated transcriptionally in the transition of barley microspores from the gametophytic to the embryogenic pathway. Plant Cell Rep 2009; 28:551-9. [PMID: 19112566 DOI: 10.1007/s00299-008-0662-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/21/2008] [Revised: 11/28/2008] [Accepted: 12/09/2008] [Indexed: 05/13/2023]
Abstract
Microspores genetically programmed to produce male gametes can be switched to the embryogenic pathway to give rise to haploid embryos. Microspore embryogenesis is usually induced in barley by stress pre-treatment applied to vacuolated microspores. We studied the expression of two genes during the early stages of microspore embryogenesis to gain further insight into the microspore transition from the gametophytic to the embryogenic pathway. RT-PCR together with in situ hybridization on sections (ISH) and whole-mount in situ hybridization (WISH) were used to analyse the expression of the early-culture abundant gene (ECA1), which is expressed in barley during microspore embryogenesis, and a polygalacturonase gene (HvPG1), a late pollen gene expressed during gametogenesis only after microspore division. Both ECA1 and HvPG1 genes were transcriptionally active after stress pre-treatment in the same populations of microspore-derived structures, representing the sporophytically induced ones. ECA1 transcripts were also detected after 3 days' culture. Our results point to the possibility of using ECA1 gene expression as a marker for the induction of microspore embryogenesis and the earliest stages of this process. Finally, we demonstrate that WISH is a suitable technique for studying gene expression in embryogenic microspore populations and, because different structures can be examined individually, is an appropriate complement to transcriptomic profile analyses in the study of early microspore embryogenesis.
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Affiliation(s)
- Amada Pulido
- Department of Plant Biochemistry, Cell and Molecular Biology, EEZ (CSIC), Granada, Spain
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Bakos F, Szabó L, Olmedilla A, Barnabás B. Histological comparison between wheat embryos developing in vitro from isolated zygotes and those developing in vivo. ACTA ACUST UNITED AC 2009; 22:15-25. [PMID: 20033452 DOI: 10.1007/s00497-008-0087-7] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2008] [Accepted: 09/17/2008] [Indexed: 01/09/2023]
Abstract
There is currently great interest shown in understanding the process of embryogenesis and, due to the relative inaccessibility of these structures in planta, extended studies are carried out in various in vitro systems. The culture of isolated zygotes in particular provides an excellent platform to study the process of in planta embryogenesis. However, very few comparisons have been made between zygotic embryos grown entirely in cultures and those grown in vivo. The present study analyses the differences and similarities between the in vitro and in vivo development of wheat zygotic embryos at the level of morphology and histology. The study was possible thanks to an efficient culture system and an appropriate method of preparing isolated wheat zygotes for microscopy. The in vitro embryos were fixed, embedded and sectioned in the two-celled, globular, club-shaped and fully differentiated stages. Embryos developing in vitro closely followed the morphology of their in planta counterparts and their cell types and tissues were also similar, demonstrating the applicability of the present culture system for studying the process of zygotic embryogenesis. However, some important differences were also detected in the case of in vitro development: the disturbance of or lack of initial polarity led to changes in the division symmetry of the zygotes and subsequently to the formation of uniform cells in the globular structures. Presumably, differences between the in vitro and in planta environments resulted in a lower level of differentiation and maturation in in vitro embryos and in abundant starch and protein accumulation in the scutellum.
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Peng XB, Sun MX. Gamete recognition in higher plants: an abstruse but charming mystery. J Integr Plant Biol 2008; 50:868-874. [PMID: 18713397 DOI: 10.1111/j.1744-7909.2008.00706.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Although much effort has been made to uncover the mechanism underlying double fertilization, little knowledge has been acquired for understanding the molecular base of gamete recognition, mainly because of technical limitations. Still, progress has been made in terms of the mechanism, including the identification of candidate molecules that are involved in gamete recognition in angiosperms. New cues for gamete recognition have been found by the successful separation of the gametes and construction of gamete-specific cDNA libraries in several species, and the application of molecular approaches for studying this process by mutations. Thus, the topic is considered an abstruse but charming mystery.
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Affiliation(s)
- Xiong-Bo Peng
- Key Laboratory of Ministry of Education for Plant Developmental Biology, College of Life Sciences, Wuhan University, Wuhan 430072, China
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Kranz E, Scholten S. In vitro fertilization: analysis of early post-fertilization development using cytological and molecular techniques. ACTA ACUST UNITED AC 2008; 21:67-77. [DOI: 10.1007/s00497-007-0060-x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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22
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Abstract
The angiosperm female gametophyte typically consists of one egg cell, two synergid cells, one central cell, and three antipodal cells. Each of these four cell types has unique structural features and performs unique functions that are essential for the reproductive process. The gene regulatory networks conferring these four phenotypic states are largely uncharacterized. As a first step towards dissecting the gene regulatory networks of the female gametophyte, we have identified a large collection of genes expressed in specific cells of the Arabidopsis thaliana female gametophyte. We identified these genes using a differential expression screen based on reduced expression in determinant infertile1 (dif1) ovules, which lack female gametophytes. We hybridized ovule RNA probes with Affymetrix ATH1 genome arrays and validated the identified genes using real-time RT-PCR. These assays identified 71 genes exhibiting reduced expression in dif1 ovules. We further validated 45 of these genes using promoter::GFP fusions and 43 were expressed in the female gametophyte. In the context of the ovule, 11 genes were expressed exclusively in the antipodal cells, 11 genes were expressed exclusively or predominantly in the central cell, 17 genes were expressed exclusively or predominantly in the synergid cells, one gene was expressed exclusively in the egg cell, and three genes were expressed strongly in multiple cells of the female gametophyte. These genes provide insights into the molecular processes functioning in the female gametophyte and can be used as starting points to dissect the gene regulatory networks functioning during differentiation of the four female gametophyte cell types.
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Affiliation(s)
- Joshua G Steffen
- Department of Biology, University of Utah, Salt Lake City, UT 84112-0840, USA
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Ning J, Peng XB, Qu LH, Xin HP, Yan TT, Sun M. Differential gene expression in egg cells and zygotes suggests that the transcriptome is restructed before the first zygotic division in tobacco. FEBS Lett 2006; 580:1747-52. [PMID: 16510144 DOI: 10.1016/j.febslet.2006.02.028] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2005] [Revised: 01/24/2006] [Accepted: 02/13/2006] [Indexed: 11/16/2022]
Abstract
We applied suppression subtractive hybridization and mirror orientation selection to compare gene expression profiles of isolated Nicotiana tabacum cv SR1 zygotes and egg cells. Our results revealed that many differentially expressed genes in zygotes were transcribed de novo after fertilization. Some of these genes are critical to zygote polarity and pattern formation during early embryogenesis. This suggests that the transcriptome is restructed in zygote and that the maternal-to-zygotic transition happens before the first zygotic division, which is much earlier in higher plants than in animals. The expressed sequence tags used in this study provide a valuable resource for future research on fertilization and early embryogenesis.
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Affiliation(s)
- Jue Ning
- Key Laboratory of Ministry of Education for Plant Developmental Biology, College of Life Science, Wuhan University, Wuhan 430072, China
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Sprunck S, Baumann U, Edwards K, Langridge P, Dresselhaus T. The transcript composition of egg cells changes significantly following fertilization in wheat (Triticum aestivum L.). Plant J 2005; 41:660-72. [PMID: 15703054 DOI: 10.1111/j.1365-313x.2005.02332.x] [Citation(s) in RCA: 93] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Here, we report the transcript profile of wheat egg cells and proembryos, just after the first cell division. Microdissected female gametophytes of wheat were used to isolate eggs and two-celled proembryos to construct cell type-specific cDNA libraries. In total, 1197 expressed sequence tags (ESTs) were generated. Analysis of these ESTs revealed numerous novel transcripts. In egg cells, 17.6% of the clustered ESTs represented novel transcripts, while 11.4% novel clusters were identified in the two-celled proembryo. Functional classification of sequences with similarity to previously characterized proteins indicates that the unfertilized egg cell has a higher metabolic activity and protein turnover than previously thought. Transcript composition of two-celled proembryos was significantly distinct from egg cells, reflecting DNA replication as well as high transcriptional and translational activity. Several novel transcripts of the egg cell are specific for this cell. In contrast, some fertilization induced novel mRNAs are abundant also in sporophytic tissues indicating a more general role in plant growth and development. The potential functions of genes based on similarity to known genes involved in developmental processes are discussed. Our analysis has identified numerous genes with potential roles in embryo sac function such as signaling, fertilization or induction of embryogenesis.
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Affiliation(s)
- Stefanie Sprunck
- Developmental Biology and Biotechnology, Biocenter Klein Flottbek, University of Hamburg, Ohnhorststrasse 18, D-22609 Hamburg, Germany
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Abstract
The plant life cycle alternates between a diploid sporophyte generation and a haploid gametophyte generation. The angiosperm female gametophyte is critical to the reproductive process. It is the structure within which egg cell production and fertilization take place. In addition, the female gametophyte plays a role in pollen tube guidance, the induction of seed development, and the maternal control of seed development. Genetic analysis in Arabidopsis has uncovered mutations that affect female gametophyte development and function. Mutants defective in almost all stages of development have been identified, and analysis of these mutants is beginning to reveal features of the female gametophyte developmental program. Other mutations that affect female gametophyte function have uncovered regulatory genes required for the induction of endosperm development. From these studies, we are beginning to understand the regulatory networks involved in female gametophyte development and function. Further investigation of the female gametophyte will require complementary approaches including expression-based approaches to obtain a complete profile of the genes functioning within this critical structure.
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Affiliation(s)
- Gary N Drews
- Department of Biology, University of Utah, Salt Lake City, Utah 84112, USA.
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Abstract
The term apomixis encompasses a suite of processes whereby seeds form asexually in plants. In contrast to sexual reproduction, seedlings arising from apomixis retain the genotype of the maternal parent. The transfer of apomixis and its effective utilization in crop plants (where it is largely absent) has major advantages in agriculture. The hallmark components of apomixis include female gamete formation without meiosis (apomeiosis), fertilization-independent embryo development (parthenogenesis), and developmental adaptations to ensure functional endosperm formation. Understanding the molecular mechanisms underlying apomixis, a developmentally fascinating phenomenon in plants, is critical for the successful induction and utilization of apomixis in crop plants. This review draws together knowledge gained from analyzing ovule, embryo, and endosperm development in sexual and apomictic plants. It consolidates the view that apomixis and sexuality are closely interrelated developmental pathways where apomixis can be viewed as a deregulation of the sexual process in both time and space.
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Affiliation(s)
- Anna M Koltunow
- Commonwealth Scientific and Industrial Research Organization, Plant Industry, P.O. Box 350, Glen Osmond, South Australia 5064, Australia.
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