The Experts below are selected from a list of 282 Experts worldwide ranked by ideXlab platform
Minako Ueda - One of the best experts on this subject based on the ideXlab platform.
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Intracellular dynamics and transcriptional regulations in plant Zygotes: a case study of Arabidopsis
Plant Reproduction, 2020Co-Authors: Yusuke Kimata, Minako UedaAbstract:Key message Recent understandings of Arabidopsis Zygote . Abstract Body axis formation is essential for the proper development of multicellular organisms. The apical-basal axis in Arabidopsis thaliana is determined by the asymmetric division of the Zygote, following its cellular polarization. However, the regulatory mechanism of Zygote polarization is unclear due to technical issues. The Zygote is located deep in the seed (ovule) in flowers, which prevents the living dynamics of Zygotes from being observed. In addition, elucidation of molecular pathways by conventional forward genetic screens was not enough because of high gene redundancy in early development. Here, we present a review introducing two new methods, which have been developed to overcome these problems. Method 1: the two-photon live-cell imaging method provides a new system to visualize the dynamics of intracellular structures in Arabidopsis Zygotes, such as cytoskeletons and vacuoles. Microtubules form transverse rings and control Zygote elongation, while vacuoles dynamically change their shapes along longitudinal actin filaments and support polar nuclear migration. Method 2: the transcriptome method uses isolated Arabidopsis Zygotes and egg cells to reveal the gene expression profiles before and after fertilization. This approach revealed that de novo transcription occurs extensively and immediately after fertilization. Moreover, inhibition of the de novo transcription was shown to sufficiently block the zygotic division, thus indicating a strong possibility that yet unidentified Zygote regulators can be found using this transcriptome approach. These new strategies in Arabidopsis will help to further our understanding of the fundamental principles regarding the proper formation of plant bodies from unicellular Zygotes.
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transcriptional integration of paternal and maternal factors in the arabidopsis Zygote
Genes & Development, 2017Co-Authors: Minako Ueda, Ernst Aichinger, Wen Gong, Edwin P Groot, Inge Verstraeten, Lam Dai Vu, Ive De Smet, Tetsuya Higashiyama, Masaaki UmedaAbstract:: In many plants, the asymmetric division of the Zygote sets up the apical-basal axis of the embryo. Unlike animals, plant Zygotes are transcriptionally active, implying that plants have evolved specific mechanisms to control transcriptional activation of patterning genes in the Zygote. In Arabidopsis, two pathways have been found to regulate Zygote asymmetry: YODA (YDA) mitogen-activated protein kinase (MAPK) signaling, which is potentiated by sperm-delivered mRNA of the SHORT SUSPENSOR (SSP) membrane protein, and up-regulation of the patterning gene WOX8 by the WRKY2 transcription factor. How SSP/YDA signaling is transduced into the nucleus and how these pathways are integrated have remained elusive. Here we show that paternal SSP/YDA signaling directly phosphorylates WRKY2, which in turn leads to the up-regulation of WOX8 transcription in the Zygote. We further discovered the transcription factors HOMEODOMAIN GLABROUS11/12 (HDG11/12) as maternal regulators of Zygote asymmetry that also directly regulate WOX8 transcription. Our results reveal a framework of how maternal and paternal factors are integrated in the Zygote to regulate embryo patterning.
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transcriptional activation of arabidopsis axis patterning genes wox8 9 links Zygote polarity to embryo development
Developmental Cell, 2011Co-Authors: Minako Ueda, Zhongjuan Zhang, Thomas LauxAbstract:In most flowering plants, the apical-basal body axis is established by an asymmetric division of the polarized Zygote. In Arabidopsis, early embryo patterning is regulated by WOX homeobox genes, which are coexpressed in the Zygote but become restricted to apical (WOX2) and basal (WOX8/9) cells. How the asymmetry of Zygote division is regulated and connected to the daughter cell fates is largely unknown. Here, we show that expression of WOX8 is independent of the axis patterning signal auxin, but, together with the redundant gene WOX9, is activated in the Zygote, its basal daughter cell, and the hypophysis by the zinc-finger transcription factor WRKY2. In wrky2 mutants, egg cells polarize normally but Zygotes fail to reestablish polar organelle positioning from a transient symmetric state, resulting in equal cell division and distorted embryo development. Both defects are rescued by overexpressing WOX8, indicating that WRKY2-dependent WOX8 transcription links Zygote polarization with embryo patterning.
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Transcriptional Activation of Arabidopsis Axis Patterning Genes WOX8/9 Links Zygote Polarity to Embryo Development
Developmental Cell, 2011Co-Authors: Minako Ueda, Zhongjuan Zhang, Thomas LauxAbstract:In most flowering plants, the apical-basal body axis is established by an asymmetric division of the polarized Zygote. In Arabidopsis, early embryo patterning is regulated by WOX homeobox genes, which are coexpressed in the Zygote but become restricted to apical (WOX2) and basal (WOX8/9) cells. How the asymmetry of Zygote division is regulated and connected to the daughter cell fates is largely unknown. Here, we show that expression of WOX8 is independent of the axis patterning signal auxin, but, together with the redundant gene WOX9, is activated in the Zygote, its basal daughter cell, and the hypophysis by the zinc-finger transcription factor WRKY2. In wrky2 mutants, egg cells polarize normally but Zygotes fail to reestablish polar organelle positioning from a transient symmetric state, resulting in equal cell division and distorted embryo development. Both defects are rescued by overexpressing WOX8, indicating that WRKY2-dependent WOX8 transcription links Zygote polarization with embryo patterning. © 2011 Elsevier Inc.
Thomas Laux - One of the best experts on this subject based on the ideXlab platform.
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transcriptional activation of arabidopsis axis patterning genes wox8 9 links Zygote polarity to embryo development
Developmental Cell, 2011Co-Authors: Minako Ueda, Zhongjuan Zhang, Thomas LauxAbstract:In most flowering plants, the apical-basal body axis is established by an asymmetric division of the polarized Zygote. In Arabidopsis, early embryo patterning is regulated by WOX homeobox genes, which are coexpressed in the Zygote but become restricted to apical (WOX2) and basal (WOX8/9) cells. How the asymmetry of Zygote division is regulated and connected to the daughter cell fates is largely unknown. Here, we show that expression of WOX8 is independent of the axis patterning signal auxin, but, together with the redundant gene WOX9, is activated in the Zygote, its basal daughter cell, and the hypophysis by the zinc-finger transcription factor WRKY2. In wrky2 mutants, egg cells polarize normally but Zygotes fail to reestablish polar organelle positioning from a transient symmetric state, resulting in equal cell division and distorted embryo development. Both defects are rescued by overexpressing WOX8, indicating that WRKY2-dependent WOX8 transcription links Zygote polarization with embryo patterning.
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Transcriptional Activation of Arabidopsis Axis Patterning Genes WOX8/9 Links Zygote Polarity to Embryo Development
Developmental Cell, 2011Co-Authors: Minako Ueda, Zhongjuan Zhang, Thomas LauxAbstract:In most flowering plants, the apical-basal body axis is established by an asymmetric division of the polarized Zygote. In Arabidopsis, early embryo patterning is regulated by WOX homeobox genes, which are coexpressed in the Zygote but become restricted to apical (WOX2) and basal (WOX8/9) cells. How the asymmetry of Zygote division is regulated and connected to the daughter cell fates is largely unknown. Here, we show that expression of WOX8 is independent of the axis patterning signal auxin, but, together with the redundant gene WOX9, is activated in the Zygote, its basal daughter cell, and the hypophysis by the zinc-finger transcription factor WRKY2. In wrky2 mutants, egg cells polarize normally but Zygotes fail to reestablish polar organelle positioning from a transient symmetric state, resulting in equal cell division and distorted embryo development. Both defects are rescued by overexpressing WOX8, indicating that WRKY2-dependent WOX8 transcription links Zygote polarization with embryo patterning. © 2011 Elsevier Inc.
Takashi Okamoto - One of the best experts on this subject based on the ideXlab platform.
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An imbalanced parental genome ratio affects the development of rice Zygotes.
Journal of Experimental Botany, 2018Co-Authors: Erika Toda, Yukinosuke Ohnishi, Takashi OkamotoAbstract:Upon double fertilization, one sperm cell fuses with the egg cell to form a Zygote with a 1:1 maternal-to-paternal genome ratio (1m:1p), and another sperm cell fuses with the central cell to form a triploid primary endosperm cell with a 2m:1p ratio, resulting in formation of the embryo and the endosperm, respectively. The endosperm is known to be considerably sensitive to the ratio of the parental genomes. However, the effect of an imbalance of the parental genomes on zygotic development and embryogenesis has not been well studied, because it is difficult to reproduce the parental genome-imbalanced situation in Zygotes and to monitor the developmental profile of Zygotes without external effects from the endosperm. In this study, we produced polyploid Zygotes with an imbalanced parental genome ratio by electro-fusion of isolated rice gametes and observed their developmental profiles. Polyploid Zygotes with an excess maternal gamete/genome developed normally, whereas approximately half to three-quarters of polyploid Zygotes with a paternal excess showed developmental arrests. These results indicate that paternal and maternal genomes synergistically serve Zygote development with distinct functions, and that genes with monoallelic expression play important roles during zygotic development and embryogenesis.
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Development of polyspermic Zygote and possible contribution of polyspermy to polyploid formation in angiosperms
Journal of Plant Research, 2017Co-Authors: Takashi Okamoto, Yukinosuke Ohnishi, Erika TodaAbstract:Fertilization is a general feature of eukaryotic uni- and multicellular organisms to restore a diploid genome from female and male gamete haploid genomes. In angiosperms, polyploidization is a common phenomenon, and polyploidy would have played a major role in the long-term diversification and evolutionary success of plants. As for the mechanism of formation of autotetraploid plants, the triploid-bridge pathway, crossing between triploid and diploid plants, is considered as a major pathway. For the emergence of triploid plants, fusion of an unreduced gamete with a reduced gamete is generally accepted. In addition, the possibility of polyspermy has been proposed for maize, wheat and some orchids, although it has been regarded as an uncommon mechanism of triploid formation. One of the reasons why polyspermy is regarded as uncommon is because it is difficult to reproduce the polyspermy situation in Zygotes and to analyze the developmental profiles of polyspermic triploid Zygotes. Recently, polyspermic rice Zygotes were successfully produced by electric fusion of an egg cell with two sperm cells, and their developmental profiles were monitored. Two sperm nuclei and an egg nucleus fused into a zygotic nucleus in the polyspermic Zygote, and the triploid Zygote divided into a two-celled embryo via mitotic division with a typical bipolar microtubule spindle. The two-celled proembryos further developed and regenerated into triploid plants. These suggest that polyspermic plant Zygotes have the potential to form triploid embryos, and that polyspermy in angiosperms might be a pathway for the formation of triploid plants.
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Development of Polyspermic Rice Zygotes
Plant Physiology, 2016Co-Authors: Erika Toda, Yukinosuke Ohnishi, Takashi OkamotoAbstract:Fertilization is a general feature of eukaryotic uni- and multicellular organisms to restore a diploid genome from female and male gamete haploid genomes. In most animals and fucoid algae, polyspermy block occurs at the plasmogamy step. Because the polyspermy barrier in animals and in fucoid algae is incomplete, polyspermic Zygotes are generated by multiple fertilization events. However, these polyspermic Zygotes with extra centrioles from multiple sperms show aberrant nuclear and cell division. In angiosperms, polyspermy block functions in the egg cell and the central cell to promote faithful double fertilization, although the mechanism of polyspermy block remains unclear. In contrast to the case in animals and fucoid algae, polyspermic Zygotes formed in angiosperms are not expected to die because angiosperms lack centrosomes. However, there have been no reports on the developmental profiles of polyspermic Zygotes at cellular level in angiosperms. In this study, we produced polyspermic rice Zygotes by electric fusion of an egg cell with two sperm cells, and monitored their developmental profiles. Two sperm nuclei and an egg nucleus fused into a zygotic nucleus, and the triploid Zygote divided into a two-celled embryo via mitotic division with a typical bipolar microtubule spindle, as observed during mitosis of a diploid Zygote. The two-celled proembryos further developed and regenerated into triploid plants. These findings suggest that polyspermic plant Zygotes have the potential to form triploid embryos. Polyspermy in angiosperms might be a pathway for the formation of triploid plants, which can contribute significantly to the formation of autopolyploids.
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Dynamics of Male and Female Chromatin during Karyogamy in Rice Zygotes
Plant Physiology, 2014Co-Authors: Yukinosuke Ohnishi, Rina Hoshino, Takashi OkamotoAbstract:In angiosperms, the conversion of an egg cell into a Zygote involves two sequential gametic processes: plasmogamy, the fusion of the plasma membranes of male and female gametes, and karyogamy, the fusion of the gametic nuclei. In this study, the nuclei and nuclear membranes of rice (Oryza sativa) gametes were fluorescently labeled using histones 2B-green fluorescent protein/red fluorescent protein and Sad1/UNC-84-domain protein2-green fluorescent protein, respectively, which were heterologously expressed. These gametes were fused in vitro to produce Zygotes, and the nuclei and nuclear membranes in the Zygotes were observed during karyogamy. The results indicated that the sperm nucleus migrates adjacent to the egg nucleus 5 to 10 min after plasmogamy via an actin cytoskelton, and the egg chromatin then appears to move unidirectionally into the sperm nucleus through a possible nuclear connection. The enlargement of the sperm nucleus accompanies this possible chromatin remodeling. Then, 30 to 70 min after fusion, the sperm chromatin begins to decondense with the completion of karyogamy. Based on these observations, the development of early rice Zygotes from plasmogamy to karyogamy was divided into eight stages, and using reverse transcription PCR analyses, paternal and de novo synthesized transcripts were separately detected in Zygotes at early and late karyogamy stages, respectively.
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Gene expression profiles in rice gametes and Zygotes: identification of gamete-enriched genes and up- or down-regulated genes in Zygotes after fertilization
Journal of Experimental Botany, 2013Co-Authors: Mafumi Abiko, Hiroki Maeda, Kentaro Tamura, Ikuko Hara-nishimura, Takashi OkamotoAbstract:In angiosperms, fertilization and subsequent zygotic development occur in embryo sacs deeply embedded in the ovaries; therefore, these processes are poorly elucidated. In this study, microarray-based transcriptome analyses were conducted on rice sperm cells, egg cells, and Zygotes isolated from flowers to identify candidate genes involved in gametic and/or early zygotic development. Cell type-specific transcriptomes were obtained, and up- or down-regulated genes in Zygotes after fertilization were identified, in addition to genes enriched in male and female gametes. A total of 325 putatively up-regulated and 94 putatively down-regulated genes in Zygotes were obtained. Interestingly, several genes encoding homeobox proteins or transcription factors were identified as highly up-regulated genes after fertilization, and the gene ontology for up-regulated genes was highly enriched in functions related to chromatin/DNA organization and assembly. Because a gene encoding methyltransferase 1 was identified as a highly up-regulated gene in Zygotes after fertilization, the effect of an inhibitor of this enzyme on Zygote development was monitored. The inhibitor appeared partially to affect polarity or division asymmetry in rice Zygotes, but it did not block normal embryo generation.
Masaaki Umeda - One of the best experts on this subject based on the ideXlab platform.
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transcriptional integration of paternal and maternal factors in the arabidopsis Zygote
Genes & Development, 2017Co-Authors: Minako Ueda, Ernst Aichinger, Wen Gong, Edwin P Groot, Inge Verstraeten, Lam Dai Vu, Ive De Smet, Tetsuya Higashiyama, Masaaki UmedaAbstract:: In many plants, the asymmetric division of the Zygote sets up the apical-basal axis of the embryo. Unlike animals, plant Zygotes are transcriptionally active, implying that plants have evolved specific mechanisms to control transcriptional activation of patterning genes in the Zygote. In Arabidopsis, two pathways have been found to regulate Zygote asymmetry: YODA (YDA) mitogen-activated protein kinase (MAPK) signaling, which is potentiated by sperm-delivered mRNA of the SHORT SUSPENSOR (SSP) membrane protein, and up-regulation of the patterning gene WOX8 by the WRKY2 transcription factor. How SSP/YDA signaling is transduced into the nucleus and how these pathways are integrated have remained elusive. Here we show that paternal SSP/YDA signaling directly phosphorylates WRKY2, which in turn leads to the up-regulation of WOX8 transcription in the Zygote. We further discovered the transcription factors HOMEODOMAIN GLABROUS11/12 (HDG11/12) as maternal regulators of Zygote asymmetry that also directly regulate WOX8 transcription. Our results reveal a framework of how maternal and paternal factors are integrated in the Zygote to regulate embryo patterning.
Zhongjuan Zhang - One of the best experts on this subject based on the ideXlab platform.
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transcriptional activation of arabidopsis axis patterning genes wox8 9 links Zygote polarity to embryo development
Developmental Cell, 2011Co-Authors: Minako Ueda, Zhongjuan Zhang, Thomas LauxAbstract:In most flowering plants, the apical-basal body axis is established by an asymmetric division of the polarized Zygote. In Arabidopsis, early embryo patterning is regulated by WOX homeobox genes, which are coexpressed in the Zygote but become restricted to apical (WOX2) and basal (WOX8/9) cells. How the asymmetry of Zygote division is regulated and connected to the daughter cell fates is largely unknown. Here, we show that expression of WOX8 is independent of the axis patterning signal auxin, but, together with the redundant gene WOX9, is activated in the Zygote, its basal daughter cell, and the hypophysis by the zinc-finger transcription factor WRKY2. In wrky2 mutants, egg cells polarize normally but Zygotes fail to reestablish polar organelle positioning from a transient symmetric state, resulting in equal cell division and distorted embryo development. Both defects are rescued by overexpressing WOX8, indicating that WRKY2-dependent WOX8 transcription links Zygote polarization with embryo patterning.
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Transcriptional Activation of Arabidopsis Axis Patterning Genes WOX8/9 Links Zygote Polarity to Embryo Development
Developmental Cell, 2011Co-Authors: Minako Ueda, Zhongjuan Zhang, Thomas LauxAbstract:In most flowering plants, the apical-basal body axis is established by an asymmetric division of the polarized Zygote. In Arabidopsis, early embryo patterning is regulated by WOX homeobox genes, which are coexpressed in the Zygote but become restricted to apical (WOX2) and basal (WOX8/9) cells. How the asymmetry of Zygote division is regulated and connected to the daughter cell fates is largely unknown. Here, we show that expression of WOX8 is independent of the axis patterning signal auxin, but, together with the redundant gene WOX9, is activated in the Zygote, its basal daughter cell, and the hypophysis by the zinc-finger transcription factor WRKY2. In wrky2 mutants, egg cells polarize normally but Zygotes fail to reestablish polar organelle positioning from a transient symmetric state, resulting in equal cell division and distorted embryo development. Both defects are rescued by overexpressing WOX8, indicating that WRKY2-dependent WOX8 transcription links Zygote polarization with embryo patterning. © 2011 Elsevier Inc.
