The Experts below are selected from a list of 2946 Experts worldwide ranked by ideXlab platform
Gary N Drews - One of the best experts on this subject based on the ideXlab platform.
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synergid cell death in arabidopsis is triggered following direct interaction with the pollen tube
Plant Physiology, 2007Co-Authors: Linda Sandaklienikolova, Ravishankar Palanivelu, Gregory P Copenhaver, Edward J King, Gary N DrewsAbstract:During angiosperm reproduction, one of the two synergid cells within the Female Gametophyte undergoes cell death prior to fertilization. The pollen tube enters the Female Gametophyte by growing into the synergid cell that undergoes cell death and releases its two sperm cells within the degenerating synergid cytoplasm to effect double fertilization. In Arabidopsis (Arabidopsis thaliana) and many other species, synergid cell death is dependent upon pollination. However, the mechanism by which the pollen tube causes synergid cell death is not understood. As a first step toward understanding this mechanism, we defined the temporal relationship between pollen tube arrival at the Female Gametophyte and synergid cell death in Arabidopsis. Using confocal laser scanning microscopy, light microscopy, transmission electron microscopy, and real-time observation of these two events in vitro, we demonstrate that synergid cell death initiates after the pollen tube arrives at the Female Gametophyte but before pollen tube discharge. Our results support a model in which a signaling cascade triggered by pollen tube-synergid cell contact induces synergid cell death in Arabidopsis.
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nuclear fusion defective1 encodes the arabidopsis rpl21m protein and is required for karyogamy during Female Gametophyte development and fertilization
Plant Physiology, 2006Co-Authors: Michael F Portereiko, Linda Sandaklienikolova, Alan M Lloyd, Chad A Dever, Denichiro Otsuga, Gary N DrewsAbstract:Karyogamy, or nuclear fusion, is essential for sexual reproduction. In angiosperms, karyogamy occurs three times: twice during double fertilization of the egg cell and the central cell and once during Female Gametophyte development when the two polar nuclei fuse to form the diploid central cell nucleus. The molecular mechanisms controlling karyogamy are poorly understood. We have identified nine Female Gametophyte mutants in Arabidopsis (Arabidopsis thaliana), nuclear fusion defective1 (nfd1) to nfd9, that are defective in fusion of the polar nuclei. In the nfd1 to nfd6 mutants, failure of fusion of the polar nuclei is the only defect detected during megagametogenesis. nfd1 is also affected in karyogamy during double fertilization. Using transmission electron microscopy, we showed that nfd1 nuclei fail to undergo fusion of the outer nuclear membranes. nfd1 contains a T-DNA insertion in RPL21M that is predicted to encode the mitochondrial 50S ribosomal subunit L21, and a wild-type copy of this gene rescues the mutant phenotype. Consistent with the predicted function of this gene, an NFD1-green fluorescent protein fusion protein localizes to mitochondria and the NFD1/RPL21M gene is expressed throughout the plant. The nfd3, nfd4, nfd5, and nfd6 mutants also contain T-DNA insertions in genes predicted to encode proteins that localize to mitochondria, suggesting a role for this organelle in nuclear fusion.
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myb98 is required for pollen tube guidance and synergid cell differentiation in arabidopsis
The Plant Cell, 2005Co-Authors: Ryushiro D Kasahara, Linda Sandaklienikolova, Michael F Portereiko, David S Rabiger, Gary N DrewsAbstract:The synergid cells of the Female Gametophyte play a role in many steps of the angiosperm fertilization process, including guidance of pollen tube growth to the Female Gametophyte. However, the mechanisms by which the synergid cells become specified and develop their unique features during Female Gametophyte development are not understood. We identified MYB98 in a screen for Arabidopsis thaliana genes expressed in the Female Gametophyte. MYB98 is a member of the R2R3-MYB gene family, the members of which likely encode transcription factors. In the context of the ovule, MYB98 is expressed exclusively in the synergid cells, and mutations in this gene affect the Female Gametophyte specifically. myb98 Female Gametophytes are affected in two unique features of the synergid cell, pollen tube guidance and the filiform apparatus, but are otherwise normal. MYB98 also is expressed in trichomes and endosperm. Homozygous myb98 mutants exhibit no sporophytic defects, including trichome and endosperm defects. Together, these data suggest that MYB98 controls the development of specific features within the synergid cell during Female Gametophyte development.
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development and function of the angiosperm Female Gametophyte
Annual Review of Genetics, 2002Co-Authors: Gary N Drews, Ramin YadegariAbstract:▪ 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 inves...
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identification of gametophytic mutations affecting Female Gametophyte development in arabidopsis
Developmental Biology, 1998Co-Authors: Cory Christensen, Santhi Subramanian, Gary N DrewsAbstract:Abstract The Female Gametophyte (embryo sac or megaGametophyte) plays a critical role in sexual reproduction of angiosperms. It is the structure that produces the egg cell and central cell which, following fertilization, give rise to the seed's embryo and endosperm, respectively. In addition, the Female Gametophyte mediates a host of reproductive processes including pollen tube guidance, fertilization, and the induction of seed development. Several major events occur during megagametogenesis, including syncitial nuclear divisions, cellularization, nuclear migration and fusion, and cell death. While these events have been described morphologically, the molecules regulating them in the Female Gametophyte are largely unknown. We discuss a genetic screen based on reduced seed set and segregation distortion to identify mutations affecting megagametogenesis and Female Gametophyte function. We report on the isolation of four mutants ( fem1, fem2, fem3 , and fem4 ) and show that the four mutations map to different locations within the genome. Additionally, we show that the fem1 and fem2 mutations affect only the Female Gametophyte, while the fem3 and fem4 mutations affect both the Female and male Gametophyte. We analyzed Female Gametophyte development in these four mutants as well as in the gfa2, gfa3, gfa4, gfa5 , and gfa7 mutants. We found that the fem2, fem3, gfa4 , and gfa5 mutants abort development at the one-nucleate stage, while the fem1, fem4, gfa2, gfa3 , and gfa7 mutants are affected in processes later in development such as polar nuclei fusion and cellularization. The establishment of a genetic screen to identify mutants and the development of a rapid procedure for analyzing mutant phenotypes represent a first step in the isolation of molecules that regulate Female Gametophyte development and function.
Rita Groshardt - One of the best experts on this subject based on the ideXlab platform.
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development and function of the flowering plant Female Gametophyte
Current Topics in Developmental Biology, 2019Co-Authors: Isil Erbasol Serbes, Joakim Palovaara, Rita GroshardtAbstract:Flowering plants constitute an indispensable basis for the existence of most organisms, including humans. In a world characterized by rapid population growth and climate changes, understanding plant reproduction becomes increasingly important in order to respond to the resource shortage associated with this development. New technologies enabling powerful forward genetic approaches, comprehensive genome and transcriptome analyses, and sophisticated cell isolation and imaging have advanced our understanding of the molecular mechanisms underlying gamete formation and fertilization. In addition, these techniques have allowed us to explore the fascinating cellular crosstalk, which coordinates the intra- and interorganismic interactions that secure reproductive success. Here we review the basic principles underlying development of the germ cell-harboring Female Gametophyte in flowering plants. We start with the selection of the founder cells and end with the formation of a few-celled, highly specialized structure that operates on the basis of division of labor in order to generate the next generation.
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patterning the Female Gametophyte of flowering plants
Plant Physiology, 2017Co-Authors: Dawit G Tekleyohans, Thomas Nakel, Rita GroshardtAbstract:Intracellular and intercellular mechanisms govern the differentiation of Female gametophytic cells.
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lachesis dependent egg cell signaling regulates the development of Female gametophytic cells
Development, 2012Co-Authors: Ronny Volz, Nadine Baumann, Thomas Dresselhaus, Ludwig Von Lyncker, Stefanie Sprunck, Rita GroshardtAbstract:In contrast to animals, plant germ cells are formed along with accessory cells in specialized haploid generations, termed Gametophytes. The Female Gametophyte of flowering plants consists of four different cell types, which exert distinct functions in the reproductive process. For successful fertilization, the development of the four cell types has to be tightly coordinated; however, the underlying mechanisms are not yet understood. We have previously isolated the lachesis ( lis ) mutant, which forms supernumerary gametes at the expense of adjacent accessory cells. LIS codes for the Arabidopsis homolog of the pre-mRNA splicing factor PRP4 and shows a dynamic expression pattern in the maturing Female Gametophyte. Here, we used LIS as a molecular tool to study cell-cell communication in the Female Gametophyte. We show that reducing LIS transcript amounts specifically in the egg cell, affects the development of all Female gametophytic cells, indicating that cell differentiation in the Female Gametophyte is orchestrated by the egg cell. Among the defects observed is the failure of homotypic nuclei fusion in the central cell and, as a consequence, a block in endosperm formation. LIS -mediated egg cell signaling, thus, provides a safeguard mechanism that prevents the formation of nurturing tissue in the absence of a functional egg cell.
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lachesis restricts gametic cell fate in the Female Gametophyte of arabidopsis
PLOS Biology, 2007Co-Authors: James M. Moore, Rita Groshardt, Christina Kagi, Nadine Baumann, Ramamurthy Baskar, Wendy B GaglianoAbstract:In flowering plants, the egg and sperm cells form within haploid Gametophytes. The Female Gametophyte of Arabidopsis consists of two gametic cells, the egg cell and the central cell, which are flanked by five accessory cells. Both gametic and accessory cells are vital for fertilization; however, the mechanisms that underlie the formation of accessory versus gametic cell fate are unknown. In a screen for regulators of egg cell fate, we isolated the lachesis (lis) mutant which forms supernumerary egg cells. In lis mutants, accessory cells differentiate gametic cell fate, indicating that LIS is involved in a mechanism that prevents accessory cells from adopting gametic cell fate. The temporal and spatial pattern of LIS expression suggests that this mechanism is generated in gametic cells. LIS is homologous to the yeast splicing factor PRP4, indicating that components of the splice apparatus participate in cell fate decisions.
Weicai Yang - One of the best experts on this subject based on the ideXlab platform.
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ovule development in arabidopsis progress and challenge
Current Opinion in Plant Biology, 2011Co-Authors: Weicai YangAbstract:Female Gametophyte, the central core of the ovule, is a simple seven-celled reproductive structure. Its stereotyped ontogeny provides a traceable model system to study mechanisms controlling cell growth, cell division, cell fate, pattern formation, and perhaps the function of essential genes in plants. An auxin concentration gradient was demonstrated for the first time in the embryo sac to control gametic cell fate. Mutant analysis also indicates a role of RNA processing in the mitotic progression of the gametophytic generation and cell fate determination in the embryo sac. Combined studies of genetics and transcriptome analysis revealed recently that epigenetic pathways play a critical role in Female Gametophyte development. In addition, the discovery that a large number of small secreted cysteine-rich proteins are enriched in embryo sac is of special interest. Except these insights and progresses, challenge ahead is to reveal the signaling pathways and their interactions that lead to the patterning of the Female Gametophyte.
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Female Gametophyte development in flowering plants
Annual Review of Plant Biology, 2010Co-Authors: Weicai Yang, Dongqiao Shi, Yanhong ChenAbstract:The multicellular Female Gametophyte, a unique feature of higher plants, provides us with an excellent experimental system to address fundamental questions in biology. During the past few years, we have gained significant insight into the mechanisms that control embryo sac polarity, gametophytic cell specification, and recognition between male and Female gametophytic cells. An auxin gradient has been shown for the first time to function in the Female Gametophyte to regulate gametic cell fate, and key genes that control gametic cell fate have also been identified. This review provides an overview of these exciting discoveries with a focus on molecular and genetic data.
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arabidopsis histidine kinase cki1 acts upstream of histidine phosphotransfer proteins to regulate Female Gametophyte development and vegetative growth
The Plant Cell, 2010Co-Authors: Yan Deng, Weicai Yang, Haili Dong, Bo Ren, Binglian Zheng, Yan Liang, Jianru ZuoAbstract:Cytokinin signaling is mediated by a multiple-step phosphorelay. Key components of the phosphorelay consist of the histidine kinase (HK)-type receptors, histidine phosphotransfer proteins (HP), and response regulators (RRs). Whereas overexpression of a nonreceptor-type HK gene CYTOKININ-INDEPENDENT1 (CKI1) activates cytokinin signaling by an unknown mechanism, mutations in CKI1 cause Female gametophytic lethality. However, the function of CKI1 in cytokinin signaling remains unclear. Here, we characterize a mutant allele, cki1-8, that can be transmitted through Female Gametophytes with low frequency (∼0.17%). We have recovered viable homozygous cki1-8 mutant plants that grow larger than wild-type plants, show defective megagametogenesis and rarely set enlarged seeds. We found that CKI1 acts upstream of AHP (Arabidopsis HP) genes, independently of cytokinin receptor genes. Consistently, an ahp1,2-2,3,4,5 quintuple mutant, which contains an ahp2-2 null mutant allele, exhibits severe defects in megagametogenesis, with a transmission efficiency of <3.45% through Female Gametophytes. Rarely recovered ahp1,2-2,3,4,5 quintuple mutants are seedling lethal. Finally, the Female gametophytic lethal phenotype of cki1-5 (a null mutant) can be partially rescued by IPT8 or ARR1 (a type-B Arabidopsis RR) driven by a CKI1 promoter. These results define a genetic pathway consisting of CKI1, AHPs, and type-B ARRs in the regulation of Female Gametophyte development and vegetative growth.
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arabidopsis histidine kinase cki1 acts upstream of histidine phosphotransfer proteins to regulate Female Gametophyte development and vegetative growth
The Plant Cell, 2010Co-Authors: Yan Deng, Weicai Yang, Haili Dong, Bo Ren, Binglian Zheng, Yan Liang, Jianru ZuoAbstract:Cytokinin signaling is mediated by a multiple-step phosphorelay. Key components of the phosphorelay consist of the histidine kinase (HK)-type receptors, histidine phosphotransfer proteins (HP), and response regulators (RRs). Whereas overexpression of a nonreceptor-type HK gene CYTOKININ-INDEPENDENT1 (CKI1) activates cytokinin signaling by an unknown mechanism, mutations in CKI1 cause Female gametophytic lethality. However, the function of CKI1 in cytokinin signaling remains unclear. Here, we characterize a mutant allele, cki1-8, that can be transmitted through Female Gametophytes with low frequency (approximately 0.17%). We have recovered viable homozygous cki1-8 mutant plants that grow larger than wild-type plants, show defective megagametogenesis and rarely set enlarged seeds. We found that CKI1 acts upstream of AHP (Arabidopsis HP) genes, independently of cytokinin receptor genes. Consistently, an ahp1,2-2,3,4,5 quintuple mutant, which contains an ahp2-2 null mutant allele, exhibits severe defects in megagametogenesis, with a transmission efficiency of <3.45% through Female Gametophytes. Rarely recovered ahp1,2-2,3,4,5 quintuple mutants are seedling lethal. Finally, the Female gametophytic lethal phenotype of cki1-5 (a null mutant) can be partially rescued by IPT8 or ARR1 (a type-B Arabidopsis RR) driven by a CKI1 promoter. These results define a genetic pathway consisting of CKI1, AHPs, and type-B ARRs in the regulation of Female Gametophyte development and vegetative growth.
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slow walker2 a noc1 mak21 homologue is essential for coordinated cell cycle progression during Female Gametophyte development in arabidopsis
Plant Physiology, 2009Co-Authors: Li Yuan, Zuoshun Tang, Venkatesan Sundaresan, Naiyou Liu, Dongqiao Shi, Jie Liu, Weicai YangAbstract:Morphogenesis requires the coordination of cell growth, division, and cell differentiation. Female gametogenesis in flowering plants, where a single haploid spore undergoes continuous growth and nuclear division without cytokinesis to form an eight-nucleate coenocytic embryo sac before cellularization, provides a good system to study the genetic control of such processes in multicellular organisms. Here, we report the characterization of an Arabidopsis (Arabidopsis thaliana) Female Gametophyte mutant, slow walker2 (swa2), in which the progression of the mitotic cycles and the synchrony of Female Gametophyte development were impaired, causing an arrest of Female Gametophytes at the two-, four-, or eight-nucleate stage. Delayed pollination test showed that a portion of the mutant ovules were able to develop into functional embryo sacs and could be fertilized. SWA2 encodes a nucleolar protein homologous to yeast NUCLEOLAR COMPLEX ASSOCIATED PROTEIN1 (NOC1)/MAINTENANCE OF KILLER21 that, together with NOC2, is involved in preribosome export from the nucleus to the cytoplasm. Similarly, SWA2 can physically interact with a putative Arabidopsis NOC2 homologue. SWA2 is expressed ubiquitously throughout the plant, at high levels in actively dividing tissues and Gametophytes. Therefore, we conclude that SWA2 most likely plays a role in ribosome biogenesis that is essential for the coordinated mitotic progression of the Female Gametophyte.
Venkatesan Sundaresan - One of the best experts on this subject based on the ideXlab platform.
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Recent advances in understanding Female Gametophyte development [version 1; referees: 2 approved]
F1000 Research Ltd, 2018Co-Authors: Debra J Skinner, Venkatesan SundaresanAbstract: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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auxin import and local auxin biosynthesis are required for mitotic divisions cell expansion and cell specification during Female Gametophyte development in arabidopsis thaliana
PLOS ONE, 2015Co-Authors: Aneesh Panoli, Li Yuan, Monica Alandetesaez, Gabriela Carolina Pagnussat, Maria Victoria Martin, Marissa K Simon, Christina Neff, Ranjan Swarup, Andres Bellido, Venkatesan SundaresanAbstract:The Female Gametophyte of flowering plants, called the embryo sac, develops from a haploid cell named the functional megaspore, which is specified after meiosis by the diploid sporophyte. In Arabidopsis, the functional megaspore undergoes three syncitial mitotic divisions followed by cellularization to form seven cells of four cell types including two Female gametes. The plant hormone auxin is important for sporophytic developmental processes, and auxin levels are known to be regulated by biosynthesis and transport. Here, we investigated the role of auxin biosynthetic genes and auxin influx carriers in embryo sac development. We find that genes from the YUCCA/TAA pathway (YUC1, YUC2, YUC8, TAA1, TAR2) are expressed asymmetrically in the developing ovule and embryo sac from the two-nuclear syncitial stage until cellularization. Mutants for YUC1 and YUC2 exhibited defects in cell specification, whereas mutations in YUC8, as well as mutations in TAA1 and TAR2, caused defects in nuclear proliferation, vacuole formation and anisotropic growth of the embryo sac. Additionally, expression of the auxin influx carriers AUX1 and LAX1 were observed at the micropylar pole of the embryo sac and in the adjacent cells of the ovule, and the aux1 lax1 lax2 triple mutant shows multiple Gametophyte defects. These results indicate that both localized auxin biosynthesis and auxin import, are required for mitotic divisions, cell expansion and patterning during embryo sac development.
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antipodal cells persist through fertilization in the Female Gametophyte of arabidopsis
Sexual Plant Reproduction, 2014Co-Authors: Xiaoya Song, Li Yuan, Venkatesan SundaresanAbstract:The Female Gametophyte of most flowering plants forms four cell types after cellularization, namely synergid cell, egg cell, central cell and antipodal cell. Of these, only the antipodal cells have no established functions, and it has been proposed that in many plants including Arabidopsis, the antipodal cells undergo programmed cell death during embryo sac maturation and prior to fertilization. Here, we examined the expression of Female Gametophyte-specific fluorescent reporters in mature embryo sacs of Arabidopsis, and in developing seeds shortly after fertilization. We observed expression of the fluorescence from the reporter genes in the three antipodal cells in the mature stage embryo sac, and continuing through the early syncytial endosperm stages. These observations suggest that rather than undergoing programmed cell death and degenerating at the mature stage of Female Gametophyte as previously supposed, the antipodal cells in Arabidopsis persist beyond fertilization, even when the other cell types are no longer present. The results support the concept that the Arabidopsis Female Gametophyte at maturity should be considered to be composed of seven cells and four cell types, rather than the previously prevailing view of four cells and three cell types.
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pattern formation in miniature the Female Gametophyte of flowering plants
Development, 2010Co-Authors: Venkatesan Sundaresan, Monica AlandetesaezAbstract:Plant reproduction involves gamete production by a haploid generation, the Gametophyte. For flowering plants, a defining characteristic in the evolution from the 'naked-seed' plants, or gymnosperms, is a reduced Female Gametophyte, comprising just seven cells of four different types--a microcosm of pattern formation and gamete specification about which only little is known. However, several genes involved in the differentiation, fertilization and post-fertilization functions of the Female Gametophyte have been identified and, recently, the morphogenic activity of the plant hormone auxin has been found to mediate patterning and egg cell specification. This article reviews recent progress in understanding the pattern formation, maternal effects and evolution of this essential unit of plant reproduction.
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slow walker2 a noc1 mak21 homologue is essential for coordinated cell cycle progression during Female Gametophyte development in arabidopsis
Plant Physiology, 2009Co-Authors: Li Yuan, Zuoshun Tang, Venkatesan Sundaresan, Naiyou Liu, Dongqiao Shi, Jie Liu, Weicai YangAbstract:Morphogenesis requires the coordination of cell growth, division, and cell differentiation. Female gametogenesis in flowering plants, where a single haploid spore undergoes continuous growth and nuclear division without cytokinesis to form an eight-nucleate coenocytic embryo sac before cellularization, provides a good system to study the genetic control of such processes in multicellular organisms. Here, we report the characterization of an Arabidopsis (Arabidopsis thaliana) Female Gametophyte mutant, slow walker2 (swa2), in which the progression of the mitotic cycles and the synchrony of Female Gametophyte development were impaired, causing an arrest of Female Gametophytes at the two-, four-, or eight-nucleate stage. Delayed pollination test showed that a portion of the mutant ovules were able to develop into functional embryo sacs and could be fertilized. SWA2 encodes a nucleolar protein homologous to yeast NUCLEOLAR COMPLEX ASSOCIATED PROTEIN1 (NOC1)/MAINTENANCE OF KILLER21 that, together with NOC2, is involved in preribosome export from the nucleus to the cytoplasm. Similarly, SWA2 can physically interact with a putative Arabidopsis NOC2 homologue. SWA2 is expressed ubiquitously throughout the plant, at high levels in actively dividing tissues and Gametophytes. Therefore, we conclude that SWA2 most likely plays a role in ribosome biogenesis that is essential for the coordinated mitotic progression of the Female Gametophyte.
Tetsuya Higashiyama - One of the best experts on this subject based on the ideXlab platform.
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Dynamics of the cell fate specifications during Female Gametophyte development in Arabidopsis.
'Public Library of Science (PLoS)', 2021Co-Authors: Daichi Susaki, Tetsuya Higashiyama, Takamasa Suzuki, Daisuke Maruyama, Minako Ueda, Daisuke KuriharaAbstract:The Female Gametophytes of angiosperms contain cells with distinct functions, such as those that enable reproduction via pollen tube attraction and fertilization. Although the Female Gametophyte undergoes unique developmental processes, such as several rounds of nuclear division without cell plate formation and final cellularization, it remains unknown when and how the cell fate is determined during development. Here, we visualized the living dynamics of Female Gametophyte development and performed transcriptome analysis of individual cell types to assess the cell fate specifications in Arabidopsis thaliana. We recorded time lapses of the nuclear dynamics and cell plate formation from the 1-nucleate stage to the 7-cell stage after cellularization using an in vitro ovule culture system. The movies showed that the nuclear division occurred along the micropylar-chalazal (distal-proximal) axis. During cellularization, the polar nuclei migrated while associating with the forming edge of the cell plate, and then, migrated toward each other to fuse linearly. We also tracked the gene expression dynamics and identified that the expression of MYB98pro::GFP-MYB98, a synergid-specific marker, was initiated just after cellularization in the synergid, egg, and central cells and was then restricted to the synergid cells. This indicated that cell fates are determined immediately after cellularization. Transcriptome analysis of the Female Gametophyte cells of the wild-type and myb98 mutant revealed that the myb98 synergid cells had egg cell-like gene expression profiles. Although in myb98, egg cell-specific gene expression was properly initiated in the egg cells only after cellularization, but subsequently expressed ectopically in one of the 2 synergid cells. These results, together with the various initiation timings of the egg cell-specific genes, suggest complex regulation of the individual Gametophyte cells, such as cellularization-triggered fate initiation, MYB98-dependent fate maintenance, cell morphogenesis, and organelle positioning. Our system of live-cell imaging and cell type-specific gene expression analysis provides insights into the dynamics and mechanisms of cell fate specifications in the development of Female Gametophytes in plants
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Higashiyama T. Live imaging and laser disruption reveal the dynamics and cell-cell communication during Torenia fournieri Female Gametophyte development
2016Co-Authors: Daichi Susaki, Hiroki Tsutsui, Daisuke Kurihara, Hidenori Takeuchi, Tetsuya HigashiyamaAbstract:The Female Gametophytes of many flowering plants contain one egg cell, one central cell, two synergid cells and three antipodal cells with respective morphological characteristics and functions. These cells are formed by cellularization of a multinuclear Female Gametophyte. However, the dynamics and mechanisms of Female Gametophyte development remain largely unknown due to the lack of a system to visu-alize directly and manipulate Female Gametophytes in living material. Here, we established an in vitro ovule culture system to examine Female Gametophyte development in Torenia fournieri, a unique plant species with a protruding Female Gametophyte. The four-nucleate Female gameto-phyte became eight nucleate by the final (third) mitosis and successively cellularized and matured to attract a pollen tube. The duration of final mitosis was 28 ± 6.5 min
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live imaging and laser disruption reveal the dynamics and cell cell communication during torenia fournieri Female Gametophyte development
Plant and Cell Physiology, 2015Co-Authors: Daichi Susaki, Hiroki Tsutsui, Daisuke Kurihara, Hidenori Takeuchi, Tetsuya HigashiyamaAbstract:: The Female Gametophytes of many flowering plants contain one egg cell, one central cell, two synergid cells and three antipodal cells with respective morphological characteristics and functions. These cells are formed by cellularization of a multinuclear Female Gametophyte. However, the dynamics and mechanisms of Female Gametophyte development remain largely unknown due to the lack of a system to visualize directly and manipulate Female Gametophytes in living material. Here, we established an in vitro ovule culture system to examine Female Gametophyte development in Torenia fournieri, a unique plant species with a protruding Female Gametophyte. The four-nucleate Female Gametophyte became eight nucleate by the final (third) mitosis and successively cellularized and matured to attract a pollen tube. The duration of final mitosis was 28 ± 6.5 min, and cellularization was completed in 54 ± 20 min after the end of the third mitosis. Fusion of polar nuclei in the central cell occurred in 13.1 ± 1.1 h, and onset of expression of LURE2, a pollen tube attractant gene, was visualized by a green fluorescent protein reporter 10.7 ± 2.3 h after cellularization. Laser disruption analysis demonstrated that the egg and central cells were required for synergid cells to acquire the pollen tube attraction function. Moreover, aberrant nuclear positioning and down-regulation of LURE2 were observed in one of the two synergid cells after disrupting an immature egg cell, suggesting that cell specification was affected. Our system provides insights into the precise dynamics and mechanisms of Female Gametophyte development in T. fournieri.
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pollen tube guidance beacons from the Female Gametophyte
Current Opinion in Plant Biology, 2003Co-Authors: Tetsuya Higashiyama, Haruko Kuroiwa, Tsuneyoshi KuroiwaAbstract:The sperm cell of a flowering plant cannot migrate unaided and it must be transported by the pollen-tube cell before successful fertilization can occur. The pollen tube is precisely guided to the target Female Gametophyte, the embryo sac, which contains the egg cell. The mechanism that precisely directs the pollen tube through the pistil to the Female Gametophyte has been studied for more than a century. There has been controversy over whether a diffusible signal attracts the pollen tube or whether Female tissues define its path. Emerging genetic and physiological data show that the Female Gametophyte produces at least two directional signals, and that at least one of these signals is diffusible and derived from the two synergid cells.
