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Zsögön A, Szakonyi D, Shi X, Byrne ME. Ribosomal Protein RPL27a Promotes Female Gametophyte Development in a Dose-Dependent Manner. PLANT PHYSIOLOGY 2014; 165:1133-1143. [PMID: 24872379 PMCID: PMC4081327 DOI: 10.1104/pp.114.241778] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Ribosomal protein mutations in Arabidopsis (Arabidopsis thaliana) result in a range of specific developmental phenotypes. Why ribosomal protein mutants have specific phenotypes is not fully known, but such defects potentially result from ribosome insufficiency, ribosome heterogeneity, or extraribosomal functions of ribosomal proteins. Here, we report that ovule development is sensitive to the level of Ribosomal Protein L27a (RPL27a) and is disrupted by mutations in the two paralogs RPL27aC and RPL27aB. Mutations in RPL27aC result in high levels of female sterility, whereas mutations in RPL27aB have a significant but lesser effect on fertility. Progressive reduction in RPL27a function results in increasing sterility, indicating a dose-dependent relationship between RPL27a and female fertility. RPL27a levels in both the sporophyte and gametophyte affect female gametogenesis, with different developmental outcomes determined by the dose of RPL27a. These results demonstrate that RPL27aC and RPL27aB act redundantly and reveal a function for RPL27a in coordinating complex interactions between sporophyte and gametophyte during ovule development.
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Affiliation(s)
- Agustin Zsögön
- School of Biological Sciences, University of Sydney, Sydney, New South Wales 2006, Australia
| | - Dóra Szakonyi
- School of Biological Sciences, University of Sydney, Sydney, New South Wales 2006, Australia
| | - Xiuling Shi
- School of Biological Sciences, University of Sydney, Sydney, New South Wales 2006, Australia
| | - Mary E Byrne
- School of Biological Sciences, University of Sydney, Sydney, New South Wales 2006, Australia
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52
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Tucker MR, Koltunow AMG. Traffic monitors at the cell periphery: the role of cell walls during early female reproductive cell differentiation in plants. CURRENT OPINION IN PLANT BIOLOGY 2014; 17:137-45. [PMID: 24507505 DOI: 10.1016/j.pbi.2013.11.015] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/23/2013] [Revised: 11/14/2013] [Accepted: 11/27/2013] [Indexed: 05/05/2023]
Abstract
The formation of female gametes in plants occurs within the ovule, a floral organ that is also the precursor of the seed. Unlike animals, plants lack a typical germline separated from the soma early in development and rely on positional signals, including phytohormones, mobile mRNAs and sRNAs, to direct diploid somatic precursor cells onto a reproductive program. In addition, signals moving between plant cells must overcome the architectural limitations of a cell wall which surrounds the plasma membrane. Recent studies have addressed the molecular and histological signatures of young ovule cells and indicate that dynamic cell wall changes occur over a short developmental window. These changes in cell wall properties impact signal flow and ovule cell identity, thereby aiding the establishment of boundaries between reproductive and somatic ovule domains.
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Affiliation(s)
- Matthew R Tucker
- Australian Research Council (ARC) Centre of Excellence in Plant Cell Walls, University of Adelaide, Waite Campus, Urrbrae, SA 5064, Australia.
| | - Anna M G Koltunow
- Commonwealth Scientific and Industrial Research Organisation (CSIRO) Plant Industry, Hartley Grove, Waite Campus, Urrbrae, SA 5064, Australia
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53
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Fu WQ, Zhao ZG, Ge XH, Ding L, Li ZY. Anatomy and transcript profiling of gynoecium development in female sterile Brassica napus mediated by one alien chromosome from Orychophragmus violaceus. BMC Genomics 2014; 15:61. [PMID: 24456102 PMCID: PMC3930543 DOI: 10.1186/1471-2164-15-61] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2013] [Accepted: 01/21/2014] [Indexed: 01/07/2023] Open
Abstract
BACKGROUND The gynoecium is one of the most complex organs of angiosperms specialized for seed production and dispersal, but only several genes important for ovule or embryo sac development were identified by using female sterile mutants. The female sterility in oilseed rape (Brassica napus) was before found to be related with one alien chromosome from another crucifer Orychophragmus violaceus. Herein, the developmental anatomy and comparative transcript profiling (RNA-seq) for the female sterility were performed to reveal the genes and possible metabolic pathways behind the formation of the damaged gynoecium. RESULTS The ovules in the female sterile Brassica napus with two copies of the alien chromosomes (S1) initiated only one short integument primordium which underwent no further development and the female gametophyte development was blocked after the tetrad stage but before megagametogenesis initiation. Using Brassica_ 95k_ unigene as the reference genome, a total of 28,065 and 27,653 unigenes were identified to be transcribed in S1 and donor B. napus (H3), respectively. Further comparison of the transcript abundance between S1 and H3 revealed that 4540 unigenes showed more than two fold expression differences. Gene ontology and pathway enrichment analysis of the Differentially Expressed Genes (DEGs) showed that a number of important genes and metabolism pathways were involved in the development of gynoecium, embryo sac, ovule, integuments as well as the interactions between pollen and pistil. CONCLUSIONS DEGs for the ovule development were detected to function in the metabolism pathways regulating brassinosteroid (BR) biosynthesis, adaxial/abaxial axis specification, auxin transport and signaling. A model was proposed to show the possible roles and interactions of these pathways for the sterile gynoecium development. The results provided new information for the molecular mechanisms behind the gynoecium development at early stage in B. napus.
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Affiliation(s)
| | | | | | | | - Zai-yun Li
- National Key Lab of Crop Genetic Improvement, National Center of Crop Molecular Breeding Technology, National Center of Oil Crop Improvement (Wuhan), College of Plant Science and Technology, Huazhong Agricultural University, Wuhan 430070, P, R, China.
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54
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Armenta-Medina A, Huanca-Mamani W, Sanchez-León N, Rodríguez-Arévalo I, Vielle-Calzada JP. Functional analysis of sporophytic transcripts repressed by the female gametophyte in the ovule of Arabidopsis thaliana. PLoS One 2013; 8:e76977. [PMID: 24194852 PMCID: PMC3806734 DOI: 10.1371/journal.pone.0076977] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2013] [Accepted: 08/28/2013] [Indexed: 01/07/2023] Open
Abstract
To investigate the genetic and molecular regulation that the female gametophyte could exert over neighboring sporophytic regions of the ovule, we performed a quantitative comparison of global expression in wild-type and nozzle/sporocyteless (spl) ovules of Arabidopsis thaliana (Arabidopsis), using Massively Parallel Signature Sequencing (MPSS). This comparison resulted in 1517 genes showing at least 3-fold increased expression in ovules lacking a female gametophyte, including those encoding 89 transcription factors, 50 kinases, 25 proteins containing a RNA-recognition motif (RRM), and 20 WD40 repeat proteins. We confirmed that eleven of these genes are either preferentially expressed or exclusive of spl ovules lacking a female gametophyte as compared to wild-type, and showed that six are also upregulated in determinant infertile1 (dif1), a meiotic mutant affected in a REC8-like cohesin that is also devoided of female gametophytes. The sporophytic misexpression of IOREMPTE, a WD40/transducin repeat gene that is preferentially expressed in the L1 layer of spl ovules, caused the arrest of female gametogenesis after differentiation of a functional megaspore. Our results show that in Arabidopsis, the sporophytic-gametophytic cross talk includes a negative regulation of the female gametophyte over specific genes that are detrimental for its growth and development, demonstrating its potential to exert a repressive control over neighboring regions in the ovule.
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Affiliation(s)
- Alma Armenta-Medina
- Grupo de Desarrollo Reproductivo y Apomixis, Laboratorio Nacional de Genómica para la Biodiversidad y Departamento de Ingeniería Genética de Plantas, CINVESTAV Irapuato, Irapuato, Mexico
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55
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Okada T, Hu Y, Tucker MR, Taylor JM, Johnson SD, Spriggs A, Tsuchiya T, Oelkers K, Rodrigues JC, Koltunow AM. Enlarging cells initiating apomixis in Hieracium praealtum transition to an embryo sac program prior to entering mitosis. PLANT PHYSIOLOGY 2013; 163:216-31. [PMID: 23864557 PMCID: PMC3762643 DOI: 10.1104/pp.113.219485] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/11/2013] [Accepted: 07/08/2013] [Indexed: 05/19/2023]
Abstract
Hieracium praealtum forms seeds asexually by apomixis. During ovule development, sexual reproduction initiates with megaspore mother cell entry into meiosis and formation of a tetrad of haploid megaspores. The sexual pathway ceases when a diploid aposporous initial (AI) cell differentiates, enlarges, and undergoes mitosis, forming an aposporous embryo sac that displaces sexual structures. Embryo and endosperm development in aposporous embryo sacs is fertilization independent. Transcriptional data relating to apomixis initiation in Hieracium spp. ovules is scarce and the functional identity of the AI cell relative to other ovule cell types is unclear. Enlarging AI cells with undivided nuclei, early aposporous embryo sacs containing two to four nuclei, and random groups of sporophytic ovule cells not undergoing these events were collected by laser capture microdissection. Isolated amplified messenger RNA samples were sequenced using the 454 pyrosequencing platform and comparatively analyzed to establish indicative roles of the captured cell types. Transcriptome and protein motif analyses showed that approximately one-half of the assembled contigs identified homologous sequences in Arabidopsis (Arabidopsis thaliana), of which the vast majority were expressed during early Arabidopsis ovule development. The sporophytic ovule cells were enriched in signaling functions. Gene expression indicative of meiosis was notably absent in enlarging AI cells, consistent with subsequent aposporous embryo sac formation without meiosis. The AI cell transcriptome was most similar to the early aposporous embryo sac transcriptome when comparing known functional annotations and both shared expressed genes involved in gametophyte development, suggesting that the enlarging AI cell is already transitioning to an embryo sac program prior to mitotic division.
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56
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Ceccato L, Masiero S, Sinha Roy D, Bencivenga S, Roig-Villanova I, Ditengou FA, Palme K, Simon R, Colombo L. Maternal control of PIN1 is required for female gametophyte development in Arabidopsis. PLoS One 2013; 8:e66148. [PMID: 23799075 PMCID: PMC3684594 DOI: 10.1371/journal.pone.0066148] [Citation(s) in RCA: 93] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2012] [Accepted: 04/30/2013] [Indexed: 12/29/2022] Open
Abstract
Land plants are characterised by haplo-diploid life cycles, and developing ovules are the organs in which the haploid and diploid generations coexist. Recently it has been shown that hormones such as auxin and cytokinins play important roles in ovule development and patterning. The establishment and regulation of auxin levels in cells is predominantly determined by the activity of the auxin efflux carrier proteins PIN-FORMED (PIN). To study the roles of PIN1 and PIN3 during ovule development we have used mutant alleles of both genes and also perturbed PIN1 and PIN3 expression using micro-RNAs controlled by the ovule specific DEFH9 (DEFIFICENS Homologue 9) promoter. PIN1 down-regulation and pin1-5 mutation severely affect female gametophyte development since embryo sacs arrest at the mono- and/or bi-nuclear stages (FG1 and FG3 stage). PIN3 function is not required for ovule development in wild-type or PIN1-silenced plants. We show that sporophytically expressed PIN1 is required for megagametogenesis, suggesting that sporophytic auxin flux might control the early stages of female gametophyte development, although auxin response is not visible in developing embryo sacs.
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Affiliation(s)
- Luca Ceccato
- Dipartimento di BioScienze, Università degli Studi di Milano, Milano, Italy
| | - Simona Masiero
- Dipartimento di BioScienze, Università degli Studi di Milano, Milano, Italy
| | - Dola Sinha Roy
- Dipartimento di BioScienze, Università degli Studi di Milano, Milano, Italy
| | - Stefano Bencivenga
- Dipartimento di BioScienze, Università degli Studi di Milano, Milano, Italy
| | | | - Franck Anicet Ditengou
- Institute of Biology II, Faculty of Biology, Albert-Ludwigs-Universität of Freiburg, Schänzlestrasse 1, Freiburg, Germany
| | - Klaus Palme
- Institute of Biology II, Faculty of Biology, Albert-Ludwigs-Universität of Freiburg, Schänzlestrasse 1, Freiburg, Germany
| | - Rüdiger Simon
- Institut für Entwicklungsgenetik, Heinrich-Heine Universität, Düsseldorf, Germany
| | - Lucia Colombo
- Dipartimento di BioScienze, Università degli Studi di Milano, Milano, Italy
- Institute of Biology II, Faculty of Biology, Albert-Ludwigs-Universität of Freiburg, Schänzlestrasse 1, Freiburg, Germany
- Institut für Entwicklungsgenetik, Heinrich-Heine Universität, Düsseldorf, Germany
- Istituto di Biofisica, Consiglio Nazionale delle Ricerche, Milano, Italy
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57
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Musiał K, Płachno BJ, Świątek P, Marciniuk J. Anatomy of ovary and ovule in dandelions (Taraxacum, Asteraceae). PROTOPLASMA 2013; 250:715-22. [PMID: 23001751 PMCID: PMC3659273 DOI: 10.1007/s00709-012-0455-x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/19/2012] [Accepted: 09/11/2012] [Indexed: 05/10/2023]
Abstract
The genus Taraxacum Wigg. (Asteraceae) forms a polyploid complex within which there are strong links between the ploidy level and the mode of reproduction. Diploids are obligate sexual, whereas polyploids are usually apomictic. The paper reports on a comparative study of the ovary and especially the ovule anatomy in the diploid dandelion T. linearisquameum and the triploid T. gentile. Observations with light and electron microscopy revealed no essential differences in the anatomy of both the ovary and ovule in the examined species. Dandelion ovules are anatropous, unitegmic and tenuinucellate. In both sexual and apomictic species, a zonal differentiation of the integument is characteristic of the ovule. In the integumentary layers situated next to the endothelium, the cell walls are extremely thick and PAS positive. Data obtained from TEM indicate that these special walls have an open spongy structure and their cytoplasm shows evidence of gradual degeneration. Increased deposition of wall material in the integumentary cells surrounding the endothelium takes place especially around the chalazal pole of the embryo sac as well as around the central cell. In contrast, the integumentary cells surrounding the micropylar region have thin walls and exhibit a high metabolic activity. The role of the thick-walled integumentary layers in the dandelion ovule is discussed. We also consider whether this may be a feature of taxonomic importance.
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Affiliation(s)
- K Musiał
- Department of Plant Cytology and Embryology, Jagiellonian University, Grodzka 52, 31-044, Krakow, Poland.
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58
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Sotelo-Silveira M, Cucinotta M, Chauvin AL, Chávez Montes RA, Colombo L, Marsch-Martínez N, de Folter S. Cytochrome P450 CYP78A9 is involved in Arabidopsis reproductive development. PLANT PHYSIOLOGY 2013; 162:779-99. [PMID: 23610218 PMCID: PMC3668070 DOI: 10.1104/pp.113.218214] [Citation(s) in RCA: 66] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/20/2013] [Accepted: 04/16/2013] [Indexed: 05/18/2023]
Abstract
Synchronized communication between gametophytic and sporophytic tissue is crucial for successful reproduction, and hormones seem to have a prominent role in it. Here, we studied the role of the Arabidopsis (Arabidopsis thaliana) cytochrome P450 CYP78A9 enzyme during reproductive development. First, controlled pollination experiments indicate that CYP78A9 responds to fertilization. Second, while CYP78A9 overexpression can uncouple fruit development from fertilization, the cyp78a8 cyp78a9 loss-of-function mutant has reduced seed set due to outer ovule integument development arrest, leading to female sterility. Moreover, CYP78A9 has a specific expression pattern in inner integuments in early steps of ovule development as well as in the funiculus, embryo, and integuments of developing seeds. CYP78A9 overexpression did not change the response to the known hormones involved in flower development and fruit set, and it did not seem to have much effect on the major known hormonal pathways. Furthermore, according to previous predictions, perturbations in the flavonol biosynthesis pathway were detected in cyp78a9, cyp78a8 cyp78a9, and empty siliques (es1-D) mutants. However, it appeared that they do not cause the observed phenotypes. In summary, these results add new insights into the role of CYP78A9 in plant reproduction and present, to our knowledge, the first characterization of metabolite differences between mutants in this gene family.
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59
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Demesa-Arévalo E, Vielle-Calzada JP. The classical arabinogalactan protein AGP18 mediates megaspore selection in Arabidopsis. THE PLANT CELL 2013; 25:1274-87. [PMID: 23572547 PMCID: PMC3663267 DOI: 10.1105/tpc.112.106237] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/11/2012] [Revised: 02/28/2013] [Accepted: 03/21/2013] [Indexed: 05/03/2023]
Abstract
Female gametogenesis in most flowering plants depends on the predetermined selection of a single meiotically derived cell, as the three other megaspores die without further division or differentiation. Although in Arabidopsis thaliana the formation of the functional megaspore (FM) is crucial for the establishment of the gametophytic generation, the mechanisms that determine the specification and fate of haploid cells remain unknown. Here, we show that the classical arabinogalactan protein 18 (AGP18) exerts an active regulation over the selection and survival of megaspores in Arabidopsis. During meiosis, AGP18 is expressed in integumentary cells located in the abaxial region of the ovule. Overexpression of AGP18 results in the abnormal maintenance of surviving megaspores that can acquire a FM identity but is not sufficient to induce FM differentiation before meiosis, indicating that AGP18 positively promotes the selection of viable megaspores. We also show that all four meiotically derived cells in the ovule of Arabidopsis are competent to differentiate into a gametic precursor and that the function of AGP18 is important for their selection and viability. Our results suggest an evolutionary role for arabinogalactan proteins in the acquisition of monospory and the developmental plasticity that is intrinsic to sexual reproduction in flowering plants.
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Affiliation(s)
- Edgar Demesa-Arévalo
- Grupo de Desarrollo Reproductivo y Apomixis, Laboratorio Nacional de Genómica para la Biodiversidad y Departamento de Ingeniería Genética de Plantas, Cinvestav Irapuato CP36821 Guanajuato, Mexico
| | - Jean-Philippe Vielle-Calzada
- Grupo de Desarrollo Reproductivo y Apomixis, Laboratorio Nacional de Genómica para la Biodiversidad y Departamento de Ingeniería Genética de Plantas, Cinvestav Irapuato CP36821 Guanajuato, Mexico
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60
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Lee DS, Chen LJ, Li CY, Liu Y, Tan XL, Lu BR, Li J, Gan SX, Kang SG, Suh HS, Zhu Y. The Bsister MADS gene FST determines ovule patterning and development of the zygotic embryo and endosperm. PLoS One 2013; 8:e58748. [PMID: 23527017 PMCID: PMC3602522 DOI: 10.1371/journal.pone.0058748] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2012] [Accepted: 02/05/2013] [Indexed: 11/19/2022] Open
Abstract
Many homeotic MADS-box genes have been identified as controllers of the floral transition and floral development. However, information regarding Bsister (Bs)-function genes in monocots is still limited. Here, we describe the functional characterization of a Bs-group MADS-box gene FEMALE-STERILE (FST), whose frame-shift mutation (fst) results in abnormal ovules and the complete abortion of zygotic embryos and endosperms in rice. Anatomical analysis showed that the defective development in the fst mutant exclusively occurred in sporophytic tissues including integuments, fertilized proembryos and endosperms. Analyses of the spatio-temporal expression pattern revealed that the prominent FST gene products accumulated in the inner integument, nucellar cell of the micropylar side, apical and base of the proembryos and free endosperm nuclei. Microarray and gene ontology analysis unraveled substantial changes in the expression level of many genes in the fst mutant ovules and seeds, with a subset of genes involved in several developmental and hormonal pathways appearing to be down-regulated. Using both forward and reverse genetics approaches, we demonstrated that rice FST plays indispensable roles and multiple functions during ovule and early seed development. These findings support a novel function for the Bs-group MADS-box genes in plants.
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Affiliation(s)
- Dong Sun Lee
- Key Lab of Agro-Biodiversity and Pest Management of Education Ministry, Yunnan Agricultural University, Kunming, China
- Rice Research Institute, Yunnan Agricultural University, Kunming, China
| | - Li Juan Chen
- Rice Research Institute, Yunnan Agricultural University, Kunming, China
- Key Lab of Molecular Breeding for Dian-Type Japonica Hybrid Rice of Yunnan Education Department, Yunnan Agricultural University, Kunming, China
| | - Cheng Yun Li
- Key Lab of Agro-Biodiversity and Pest Management of Education Ministry, Yunnan Agricultural University, Kunming, China
| | - Yongsheng Liu
- Ministry of Education Key Lab for Bio-resource and Eco-environment, College of Life Science, State Key Lab of Hydraulics and Mountain River Engineering, Sichuan University, Chengdu, China
| | - Xue Lin Tan
- Rice Research Institute, Yunnan Agricultural University, Kunming, China
- Key Lab of Molecular Breeding for Dian-Type Japonica Hybrid Rice of Yunnan Education Department, Yunnan Agricultural University, Kunming, China
| | - Bao-Rong Lu
- Ministry of Education Key Lab for Biodiversity and Ecological Engineering, Institute of Biodiversity Science, Fudan University, Shanghai, China
| | - Juan Li
- Rice Research Institute, Yunnan Agricultural University, Kunming, China
- Key Lab of Molecular Breeding for Dian-Type Japonica Hybrid Rice of Yunnan Education Department, Yunnan Agricultural University, Kunming, China
| | - Shu Xian Gan
- Rice Research Institute, Yunnan Agricultural University, Kunming, China
- Key Lab of Molecular Breeding for Dian-Type Japonica Hybrid Rice of Yunnan Education Department, Yunnan Agricultural University, Kunming, China
| | - Sang Gu Kang
- School of Biotechnology, Yeungnam University, Gyeongsan, Korea
| | - Hak Soo Suh
- School of Biological Resources, Yeungnam University, Gyeongsan, Korea
| | - Youyong Zhu
- Key Lab of Agro-Biodiversity and Pest Management of Education Ministry, Yunnan Agricultural University, Kunming, China
- * E-mail:
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61
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Cheng CY, Mathews DE, Schaller GE, Kieber JJ. Cytokinin-dependent specification of the functional megaspore in the Arabidopsis female gametophyte. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2013; 73:929-940. [PMID: 23181607 DOI: 10.1111/tpj.12084] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/12/2012] [Revised: 11/20/2012] [Accepted: 11/22/2012] [Indexed: 05/19/2023]
Abstract
The life cycle of higher plants alternates between the diploid sporophytic and the haploid gametophytic phases. In angiosperms, male and female gametophytes develop within the sporophyte. During female gametophyte (FG) development, a single archesporial cell enlarges and differentiates into a megaspore mother cell, which then undergoes meiosis to give rise to four megaspores. In most species of higher plants, including Arabidopsis thaliana, the megaspore closest to the chalaza develops into the functional megaspore (FM), and the remaining three megaspores degenerate. Here, we examined the role of cytokinin signaling in FG development. We characterized the FG phenotype in three triple mutants harboring non-overlapping T-DNA insertions in cytokinin AHK receptors. We demonstrate that even the strongest mutant is not a complete null for the cytokinin receptors. Only the strongest mutant displayed a near fully penetrant disruption of FG development, and the weakest triple ahk mutant had only a modest FG phenotype. This suggests that cytokinin signaling is essential for FG development, but that only a low threshold of signaling activity is required for this function. Furthermore, we demonstrate that there is elevated cytokinin signaling localized in the chalaza of the ovule, which is enhanced by the asymmetric localization of cytokinin biosynthetic machinery and receptors. We show that an FM-specific marker is absent in the multiple ahk ovules, suggesting that disruption of cytokinin signaling elements in Arabidopsis blocks the FM specification. Together, this study reveals a chalazal-localized sporophytic cytokinin signal that plays an important role in FM specification in FG development.
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Affiliation(s)
- Chia-Yi Cheng
- Biology Department, University of North Carolina, CB#3280, Chapel Hill, NC 27599, USA
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62
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Chevalier E, Loubert-Hudon A, Matton DP. ScRALF3, a secreted RALF-like peptide involved in cell-cell communication between the sporophyte and the female gametophyte in a solanaceous species. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2013; 73:1019-33. [PMID: 23237060 DOI: 10.1111/tpj.12096] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/27/2012] [Revised: 11/29/2012] [Accepted: 12/06/2012] [Indexed: 05/16/2023]
Abstract
Small peptides have been shown to regulate numerous aspects of plant development through cell-cell communication. These signaling events are particularly important during reproduction, regulating gamete development and embryogenesis. Rapid alkalinization factor (RALF)-like genes, a large gene family that encodes secreted peptides, have specific or ubiquitous expression patterns. Previously, five RALF-like genes with potential involvement during reproduction were isolated from Solanum chacoense. Here, we show that ScRALF3 is an important peptide regulator of female gametophyte development. Its expression, which is auxin-inducible, is strictly regulated before and after fertilization. Down-regulation of ScRALF3 expression by RNA interference leads to the production of smaller fruits that produce fewer seeds, due to improper development of the embryo sacs. Defects include loss of embryo sac nuclei polarization, as well as an increase in asynchronous division, accounting for cellular dysfunctions and premature embryo sac development arrest during megagametogenesis. ScRALF3 is expressed in the sporophytic tissue surrounding the embryo sac, the integument and the nucellus, as revealed by in situ hybridization and GUS staining. As expected for a secreted peptide, fluorescence from an ScRALF3-GFP fusion construct is detected throughout the secretory pathway. Therefore, the ScRALF3 secreted peptide may be directly involved in the regulation of multiple aspects of cell-cell communication between the female gametophyte and its surrounding sporophytic tissue during ovule development.
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Affiliation(s)
- Eric Chevalier
- Institut de Recherche en Biologie Végétale, Département de Sciences Biologiques Université de Montréal, 4101 rue Sherbrooke est, Montréal, Québec, H1X 2B2, Canada
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63
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Feng X, Zilberman D, Dickinson H. A Conversation across Generations: Soma-Germ Cell Crosstalk in Plants. Dev Cell 2013; 24:215-25. [DOI: 10.1016/j.devcel.2013.01.014] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2012] [Revised: 01/16/2013] [Accepted: 01/18/2013] [Indexed: 11/15/2022]
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64
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Wu JJ, Peng XB, Li WW, He R, Xin HP, Sun MX. Mitochondrial GCD1 dysfunction reveals reciprocal cell-to-cell signaling during the maturation of Arabidopsis female gametes. Dev Cell 2012; 23:1043-58. [PMID: 23085019 DOI: 10.1016/j.devcel.2012.09.011] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2011] [Revised: 06/11/2012] [Accepted: 09/17/2012] [Indexed: 12/27/2022]
Abstract
Cell-to-cell communication in embryo sacs is thought to regulate the development of female gametes in flowering plants, but the details remain poorly understood. Here, we report a mitochondrial protein, GAMETE CELL DEFECTIVE 1 (GCD1), enriched in gametophytes that is essential for final maturation of female gametes. Using Arabidopsis gcd1 mutants, we found that final maturation of the egg and central cells is not required for double fertilization but is necessary for embryogenesis initiation and endosperm development. Furthermore, nonautonomous effects, observed when GCD1 or AAC2 function is disrupted, suggest that mitochondrial function influences reciprocal signaling between central and egg cells to regulate maturation of the partner (egg or central) cell. Our findings confirm that cell-to-cell communication is important in functional maturation of female gametic cells and suggest that both egg and central cells sense and transmit their mitochondrial metabolic status as an important cue that regulates the coordination of gamete maturation.
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Affiliation(s)
- Jian-Jun Wu
- Department of Cell and Development Biology, College of Life Science, State Key Laboratory of Plant Hybrid Rice, Wuhan University, Wuhan 430072, China
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65
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Wang N, Huang HJ, Ren ST, Li JJ, Sun Y, Sun DY, Zhang SQ. The rice wall-associated receptor-like kinase gene OsDEES1 plays a role in female gametophyte development. PLANT PHYSIOLOGY 2012; 160:696-707. [PMID: 22885936 PMCID: PMC3461549 DOI: 10.1104/pp.112.203943] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
The wall-associated kinase (WAK) gene family is a unique subfamily of receptor-like kinases (RLKs) in plants. WAK-RLKs play roles in cell expansion, pathogen resistance, and metal tolerance in Arabidopsis (Arabidopsis thaliana). Rice (Oryza sativa) has far more WAK-RLK genes than Arabidopsis, but the functions of rice WAK-RLKs are poorly understood. In this study, we found that one rice WAK-RLK gene, DEFECT IN EARLY EMBRYO SAC1 (OsDEES1), is involved in the regulation of early embryo sac development. OsDEES1 silencing by RNA interference caused a high rate of female sterility. Crossing experiments showed that female reproductive organs lacking OsDEES1 carried a functional defect. A detailed investigation of the ovaries from OsDEES1 RNA interference plants indicated that the knockdown of OsDEES1 expression did not affect megasporogenesis but that it disturbed female gametophyte formation, resulting in a degenerated embryo sac and defective seed formation. OsDEES1 exhibited a tissue-specific expression pattern in flowers and seedlings. In the ovary, OsDEES1 was expressed in the megagametophyte region and surrounding nucellus cells in the ovule near the micropylar region. OsDEES1 was found to be a membrane-localized protein with a unique sequence compared with other WAK-RLKs. These data indicate that OsDEES1 plays a role in rice sexual reproduction by regulating female gametophyte development. This study offers new insight into the functions of the WAK-RLK family.
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66
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Płachno BJ, Swiątek P. Actin cytoskeleton in the extra-ovular embryo sac of Utricularia nelumbifolia (Lentibulariaceae). PROTOPLASMA 2012; 249:663-70. [PMID: 21786167 PMCID: PMC3382281 DOI: 10.1007/s00709-011-0306-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/30/2011] [Accepted: 07/10/2011] [Indexed: 05/25/2023]
Abstract
The actin cytoskeleton in the mature female gametophyte of angiosperms has been examined in only a few dicot and monocot species. The main purposes of this study were to identify how the actin cytoskeleton is arranged in the mature extra-ovular embryo sac in Utricularia nelumbifolia (Lentibulariaceae). We found that the extra-ovular part of the central cell has a well-developed actin cytoskeleton: actin microfilaments formed of long strands which run longitudinally or transversally to the long axis of the embryo sac. The exerted part of the central cell, which is exposed to the environment of the ovary chamber, is highly vacuolated and in the thin peripheral cytoplasm possesses a complicated network of actin microfilaments. The epidermal cells of the placenta that are in contact with the extra-ovular part of the embryo sac are crushed. The ultrastructure data of these cells are presented. We detected the accumulation of the actin cytoskeleton between the micropylar parts of the synergids and the extra-ovular part of central cell. This actin accumulation is unusual because in typical angiosperms the micropylar parts of the synergids form the apex of the female gametophyte.
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Affiliation(s)
- Bartosz Jan Płachno
- Department of Plant Cytology and Embryology, Jagiellonian University, Grodzka 52, 31-044, Cracow, Poland.
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67
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Sánchez-León N, Arteaga-Vázquez M, Alvarez-Mejía C, Mendiola-Soto J, Durán-Figueroa N, Rodríguez-Leal D, Rodríguez-Arévalo I, García-Campayo V, García-Aguilar M, Olmedo-Monfil V, Arteaga-Sánchez M, de la Vega OM, Nobuta K, Vemaraju K, Meyers BC, Vielle-Calzada JP. Transcriptional analysis of the Arabidopsis ovule by massively parallel signature sequencing. JOURNAL OF EXPERIMENTAL BOTANY 2012; 63:3829-42. [PMID: 22442422 PMCID: PMC3388818 DOI: 10.1093/jxb/ers075] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
The life cycle of flowering plants alternates between a predominant sporophytic (diploid) and an ephemeral gametophytic (haploid) generation that only occurs in reproductive organs. In Arabidopsis thaliana, the female gametophyte is deeply embedded within the ovule, complicating the study of the genetic and molecular interactions involved in the sporophytic to gametophytic transition. Massively parallel signature sequencing (MPSS) was used to conduct a quantitative large-scale transcriptional analysis of the fully differentiated Arabidopsis ovule prior to fertilization. The expression of 9775 genes was quantified in wild-type ovules, additionally detecting >2200 new transcripts mapping to antisense or intergenic regions. A quantitative comparison of global expression in wild-type and sporocyteless (spl) individuals resulted in 1301 genes showing 25-fold reduced or null activity in ovules lacking a female gametophyte, including those encoding 92 signalling proteins, 75 transcription factors, and 72 RNA-binding proteins not reported in previous studies based on microarray profiling. A combination of independent genetic and molecular strategies confirmed the differential expression of 28 of them, showing that they are either preferentially active in the female gametophyte, or dependent on the presence of a female gametophyte to be expressed in sporophytic cells of the ovule. Among 18 genes encoding pentatricopeptide-repeat proteins (PPRs) that show transcriptional activity in wild-type but not spl ovules, CIHUATEOTL (At4g38150) is specifically expressed in the female gametophyte and necessary for female gametogenesis. These results expand the nature of the transcriptional universe present in the ovule of Arabidopsis, and offer a large-scale quantitative reference of global expression for future genomic and developmental studies.
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Affiliation(s)
- Nidia Sánchez-León
- Laboratorio Nacional de Genómica para la Biodiversidad y Departamento de Ingeniería Genética de Plantas, Cinvestav Irapuato CP36821 México
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68
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Tucker MR, Okada T, Johnson SD, Takaiwa F, Koltunow AMG. Sporophytic ovule tissues modulate the initiation and progression of apomixis in Hieracium. JOURNAL OF EXPERIMENTAL BOTANY 2012; 63:3229-41. [PMID: 22378948 PMCID: PMC3350933 DOI: 10.1093/jxb/ers047] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/29/2011] [Revised: 01/30/2012] [Accepted: 01/31/2012] [Indexed: 05/21/2023]
Abstract
Apomixis in Hieracium subgenus Pilosella initiates in ovules when sporophytic cells termed aposporous initial (AI) cells enlarge near sexual cells undergoing meiosis. AI cells displace the sexual structures and divide by mitosis to form unreduced embryo sac(s) without meiosis (apomeiosis) that initiate fertilization-independent embryo and endosperm development. In some Hieracium subgenus Pilosella species, these events are controlled by the dominant LOSS OF APOMEIOSIS (LOA) and LOSS OF PARTHENOGENESIS (LOP) loci. In H. praealtum and H. piloselloides, which both contain the same core LOA locus, the timing and frequency of AI cell formation is altered in derived mutants exhibiting abnormal funiculus growth and in transgenic plants expressing rolB which alters cellular sensitivity to auxin. The impact on apomictic and sexual reproduction was examined here when a chimeric RNAse gene was targeted to the funiculus and basal portions of the ovule, and also when polar auxin transport was inhibited during ovule development following N-1-naphthylphthalamic acid (NPA) application. Both treatments led to ovule deformity in the funiculus and distal parts of the ovule and LOA-dependent alterations in the timing, position, and frequency of AI cell formation. In the case of NPA treatment, this correlated with increased expression of DR5:GFP in the ovule, which marks the accumulation of the plant hormone auxin. Our results show that sporophytic information potentiated by funiculus growth and polar auxin transport influences ovule development, the initiation of apomixis, and the progression of embryo sac development in Hieracium. Signals associated with ovule pattern formation and auxin distribution or perception may influence the capacity of sporophytic ovule cells to respond to LOA.
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Affiliation(s)
- Matthew R. Tucker
- CSIRO Plant Industry, Waite Campus, Hartley Grove, Urrbrae SA 5064, Australia
| | - Takashi Okada
- CSIRO Plant Industry, Waite Campus, Hartley Grove, Urrbrae SA 5064, Australia
| | - Susan D. Johnson
- CSIRO Plant Industry, Waite Campus, Hartley Grove, Urrbrae SA 5064, Australia
| | - Fumio Takaiwa
- Transgenic Crop Research and Development Centre, National Institute of Agrobiological Sciences, Tsukuba, Ibaraki, Japan
| | - Anna M. G. Koltunow
- CSIRO Plant Industry, Waite Campus, Hartley Grove, Urrbrae SA 5064, Australia
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Mizzotti C, Mendes MA, Caporali E, Schnittger A, Kater MM, Battaglia R, Colombo L. The MADS box genes SEEDSTICK and ARABIDOPSIS Bsister play a maternal role in fertilization and seed development. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2012; 70:409-20. [PMID: 22176531 DOI: 10.1111/j.1365-313x.2011.04878.x] [Citation(s) in RCA: 84] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
The haploid generation of flowering plants develops within the sporophytic tissues of the ovule. After fertilization, the maternal seed coat develops in a coordinated manner with formation of the embryo and endosperm. In the arabidopsis bsister (abs) mutant, the endothelium, which is the most inner cell layer of the integuments that surround the haploid embryo sac, does not accumulate proanthocyanidins and the cells have an abnormal morphology. However, fertility is not affected in abs single mutants. SEEDSTICK regulates ovule identity redundantly with SHATTERPROOF 1 (SHP1) and SHP2 while a role in the control of fertility was not reported previously. Here we describe the characterization of the abs stk double mutant. This double mutant develops very few seeds due to both a reduced number of fertilized ovules and seed abortions later during development. Morphological analysis revealed a total absence of endothelium in this double mutant. Additionally, massive starch accumulation was observed in the embryo sac. The phenotype of the abs stk double mutant highlights the importance of the maternal-derived tissues, particularly the endothelium, for the development of the next generation.
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Affiliation(s)
- Chiara Mizzotti
- Dipartimento di Biologia, Università degli Studi di Milano, Via Celoria 26, 20133 Milan, Italy
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70
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Plant germline development: a tale of cross-talk, signaling, and cellular interactions. ACTA ACUST UNITED AC 2011; 24:91-5. [PMID: 21590362 DOI: 10.1007/s00497-011-0170-3] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
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71
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Nuclear behavior, cell polarity, and cell specification in the female gametophyte. ACTA ACUST UNITED AC 2011; 24:123-36. [PMID: 21336612 DOI: 10.1007/s00497-011-0161-4] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2010] [Accepted: 01/15/2011] [Indexed: 12/18/2022]
Abstract
In flowering plants, the haploid gamete-forming generation comprises only a few cells and develops within the reproductive organs of the flower. The female gametophyte has become an attractive model system to study the genetic and molecular mechanisms involved in pattern formation and gamete specification. It originates from a single haploid spore through three free nuclear division cycles, giving rise to four different cell types. Research over recent years has allowed to catch a glimpse of the mechanisms that establish the distinct cell identities and suggests dynamic cell-cell communication to orchestrate not only development among the cells of the female gametophyte but also the interaction between male and female gametophytes. Additionally, cytological observations and mutant studies have highlighted the importance of nuclei migration- and positioning for patterning the female gametophyte. Here we review current knowledge on the mechanisms of cell specification in the female gametophyte, emphasizing the importance of positional cues for the establishment of distinct molecular profiles.
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72
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The asymmetric division of the Arabidopsis zygote: from cell polarity to an embryo axis. ACTA ACUST UNITED AC 2011; 24:161-9. [PMID: 21225434 DOI: 10.1007/s00497-010-0160-x] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2010] [Accepted: 12/22/2010] [Indexed: 12/29/2022]
Abstract
During plant embryogenesis, a simple body plan consisting of shoot and root meristem that are connected by the embryo axis is set up by the first few rounds of cell divisions after fertilization. Postembryonically, the elaborate architecture of plants is created from stem cell populations of both meristems. Here, we address how the main axis (apical-basal) of the plant embryo is established from the single-celled zygote and the role that the asymmetric division of the zygote plays in this process. We will mainly draw on examples from the model plant Arabidopsis, for which several key regulators have been identified during the last years.
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73
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Abstract
The angiosperm female gametophyte is critical for plant reproduction. It contains the egg cell and central cell that become fertilized and give rise to the embryo and endosperm of the seed, respectively. Female gametophyte development begins early in ovule development with the formation of a diploid megaspore mother cell that undergoes meiosis. One resulting haploid megaspore then develops into the female gametophyte. Genetic and epigenetic processes mediate specification of megaspore mother cell identity and limit megaspore mother cell formation to a single cell per ovule. Auxin gradients influence female gametophyte polarity and a battery of transcription factors mediate female gametophyte cell specification and differentiation. The mature female gametophyte secretes peptides that guide the pollen tube to the embryo sac and contains protein complexes that prevent seed development before fertilization. Post-fertilization, the female gametophyte influences seed development through maternal-effect genes and by regulating parental contributions. Female gametophytes can form by an asexual process called gametophytic apomixis, which involves formation of a diploid female gametophyte and fertilization-independent development of the egg into the embryo. These functions collectively underscore the important role of the female gametophyte in seed and food production.
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Affiliation(s)
- Gary N. Drews
- Department of Biology, University of Utah, Salt Lake City, UT 84112
- Address correspondence to
| | - Anna M.G Koltunow
- Commonwealth Scientific and Industrial Research Organization Plant Industry, Waite Campus, South Australia 5064, Australia
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