The Experts below are selected from a list of 12420 Experts worldwide ranked by ideXlab platform
Hiroshi Kamada - One of the best experts on this subject based on the ideXlab platform.
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Development of the embryo proper and the Suspensor during plant embryogenesis
Plant Biotechnology, 2005Co-Authors: Mikihisa Umehara, Hiroshi KamadaAbstract:Seed plant zygotes differentiate into two components, the embryo proper and the Suspensor. Previous studies have led to the generally accepted view that development of the embryo proper is regulated by the Suspensor connecting the embryo proper to donor tissue. However, biochemical, biological, and molecular analyses of embryogenesis are difficult, since zygotic embryos in higher plants are deeply embedded in mother tissues. To find a way out of the difficulties, some embryo-defective mutants of Arabidopsis have been used to discuss embryogenesis and Suspensor function. On the other hand, somatic embryogenesis is widely used as a model system for studying the process of zygotic embryo formation. Because somatic embryo of gymnosperms has a well-developed Suspensor, it has been successfully used to observe the Suspensor directly and to identify factors modulating the interaction between the embryo proper and the Suspensor. Various stimulatory and inhibitory factors are correlated with the interaction. Here, we review the results of studies employing Arabidopsis mutants and some gymnosperm tissue culture, and we discuss the possibility of using somatic embryogenesis as a new model for studies of Suspensor biology.
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Two stimulatory effects of the peptidyl growth factor phytosulfokine during somatic embryogenesis in Japanese larch (Larix leptolepis Gordon)
Plant Science, 2005Co-Authors: Mikihisa Umehara, Shinjiro Ogita, Hamako Sasamoto, Chang-ho Eun, Yoshikatsu Matsubayashi, Youji Sakagami, Hiroshi KamadaAbstract:Abstract In contrast to angiosperms, some gymnosperms form well-development Suspensors during somatic embryogenesis. This feature is highly useful to studies of Suspensor biology. In cell cultures of Japanese larch ( Larix leptolepis Gordon), somatic embryos rarely formed when the initial cell density was lower than 0.1 ml packed cell volume (PCV) l −1 . However, in the presence of phytosulfokine (PSK), a peptidyl plant growth factor, mitotic activity during somatic embryogenesis was stimulated, even when the cell density was lower than 0.1 ml PCV l −1 , particularly, the development of the Suspensor. Manual separation of somatic embryos into the embryo proper and the Suspensor arrested further development, but when embryos proper lacking a Suspensor were treated with PSK, the Suspensor regenerated and development proceeded to maturity. Because no division of the Suspensor cells was observed, the cells of the regenerated Suspensor probably originated from basal cells of the embryo proper. In contrast, PSK treatment of Suspensors lacking the embryo proper did not stimulate further development. These results indicate that PSK stimulates not only cell division of embryo proper but also development of the Suspensor.
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an in vitro culture system used to investigate possible interactions between the embryo proper and the Suspensor in embryogenesis in japanese larch larix leptolepis gordon
Plant Biotechnology, 2004Co-Authors: Mikihisa Umehara, Shinjiro Ogita, Hamako Sasamoto, Hiroshi KamadaAbstract:It has been proposed that the Suspensor has important roles in early embryogenesis in seed plants. However, the roles of the Suspensor are not well understood, because the development of zygotic embryos normally occurs deep within both the endosperm and the maternal cells. In this paper, we report the development of an in vitro culture system to investigate the roles of the Suspensor in the development of the embryo proper, using a somatic embryogenesis system with Japanese larch (Larix leptolepis GORDON). Our results indicate that the Suspensor is essential for the normal development of somatic embryos of this species. This method provides a useful experimental system to investigate the interactions between the embryo proper and the Suspensor.
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Inhibitory Factor(s) of Somatic Embryogenesis Regulated Suspensor Differentiation in Suspension Culture of Japanese Larch(Larix leptolepis GORDON)
Plant Biotechnology, 2004Co-Authors: Mikihisa Umehara, Shinjiro Ogita, Hamako Sasamoto, Hiroshi KamadaAbstract:Using somatic embryogenesis system of Japanese larch that develops embryos composed of embryo-proper and Suspensor, the effects of high-cell-density culture and conditioned medium on the somatic embryogenesis were investigated. High-cell-density culture strongly inhibited the somatic embryogenesis. Furthermore, the conditioned medium derived from high-cell-density culture also strongly inhibited the somatic embryogenesis, especially differentiation of the Suspensor. The inhibitory effect of the conditioned medium was not attributable to the depletion of nutrients, but to the accumulation of inhibitory factor(s) in the medium. The addition of activated charcoal to high-cell-density culture resulted in the formation of numerous somatic embryos with longer Suspensors than in the untreated one. This treatment also resulted in the formation of numerous vacuolated cells-like Suspensor on the surface surrounding the embryo-proper. These results indicate that some inhibitory factor(s) that regulates Suspensor differentiation are released into the medium of high cell density.
Mikihisa Umehara - One of the best experts on this subject based on the ideXlab platform.
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Development of the embryo proper and the Suspensor during plant embryogenesis
Plant Biotechnology, 2005Co-Authors: Mikihisa Umehara, Hiroshi KamadaAbstract:Seed plant zygotes differentiate into two components, the embryo proper and the Suspensor. Previous studies have led to the generally accepted view that development of the embryo proper is regulated by the Suspensor connecting the embryo proper to donor tissue. However, biochemical, biological, and molecular analyses of embryogenesis are difficult, since zygotic embryos in higher plants are deeply embedded in mother tissues. To find a way out of the difficulties, some embryo-defective mutants of Arabidopsis have been used to discuss embryogenesis and Suspensor function. On the other hand, somatic embryogenesis is widely used as a model system for studying the process of zygotic embryo formation. Because somatic embryo of gymnosperms has a well-developed Suspensor, it has been successfully used to observe the Suspensor directly and to identify factors modulating the interaction between the embryo proper and the Suspensor. Various stimulatory and inhibitory factors are correlated with the interaction. Here, we review the results of studies employing Arabidopsis mutants and some gymnosperm tissue culture, and we discuss the possibility of using somatic embryogenesis as a new model for studies of Suspensor biology.
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Two stimulatory effects of the peptidyl growth factor phytosulfokine during somatic embryogenesis in Japanese larch (Larix leptolepis Gordon)
Plant Science, 2005Co-Authors: Mikihisa Umehara, Shinjiro Ogita, Hamako Sasamoto, Chang-ho Eun, Yoshikatsu Matsubayashi, Youji Sakagami, Hiroshi KamadaAbstract:Abstract In contrast to angiosperms, some gymnosperms form well-development Suspensors during somatic embryogenesis. This feature is highly useful to studies of Suspensor biology. In cell cultures of Japanese larch ( Larix leptolepis Gordon), somatic embryos rarely formed when the initial cell density was lower than 0.1 ml packed cell volume (PCV) l −1 . However, in the presence of phytosulfokine (PSK), a peptidyl plant growth factor, mitotic activity during somatic embryogenesis was stimulated, even when the cell density was lower than 0.1 ml PCV l −1 , particularly, the development of the Suspensor. Manual separation of somatic embryos into the embryo proper and the Suspensor arrested further development, but when embryos proper lacking a Suspensor were treated with PSK, the Suspensor regenerated and development proceeded to maturity. Because no division of the Suspensor cells was observed, the cells of the regenerated Suspensor probably originated from basal cells of the embryo proper. In contrast, PSK treatment of Suspensors lacking the embryo proper did not stimulate further development. These results indicate that PSK stimulates not only cell division of embryo proper but also development of the Suspensor.
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an in vitro culture system used to investigate possible interactions between the embryo proper and the Suspensor in embryogenesis in japanese larch larix leptolepis gordon
Plant Biotechnology, 2004Co-Authors: Mikihisa Umehara, Shinjiro Ogita, Hamako Sasamoto, Hiroshi KamadaAbstract:It has been proposed that the Suspensor has important roles in early embryogenesis in seed plants. However, the roles of the Suspensor are not well understood, because the development of zygotic embryos normally occurs deep within both the endosperm and the maternal cells. In this paper, we report the development of an in vitro culture system to investigate the roles of the Suspensor in the development of the embryo proper, using a somatic embryogenesis system with Japanese larch (Larix leptolepis GORDON). Our results indicate that the Suspensor is essential for the normal development of somatic embryos of this species. This method provides a useful experimental system to investigate the interactions between the embryo proper and the Suspensor.
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Inhibitory Factor(s) of Somatic Embryogenesis Regulated Suspensor Differentiation in Suspension Culture of Japanese Larch(Larix leptolepis GORDON)
Plant Biotechnology, 2004Co-Authors: Mikihisa Umehara, Shinjiro Ogita, Hamako Sasamoto, Hiroshi KamadaAbstract:Using somatic embryogenesis system of Japanese larch that develops embryos composed of embryo-proper and Suspensor, the effects of high-cell-density culture and conditioned medium on the somatic embryogenesis were investigated. High-cell-density culture strongly inhibited the somatic embryogenesis. Furthermore, the conditioned medium derived from high-cell-density culture also strongly inhibited the somatic embryogenesis, especially differentiation of the Suspensor. The inhibitory effect of the conditioned medium was not attributable to the depletion of nutrients, but to the accumulation of inhibitory factor(s) in the medium. The addition of activated charcoal to high-cell-density culture resulted in the formation of numerous somatic embryos with longer Suspensors than in the untreated one. This treatment also resulted in the formation of numerous vacuolated cells-like Suspensor on the surface surrounding the embryo-proper. These results indicate that some inhibitory factor(s) that regulates Suspensor differentiation are released into the medium of high cell density.
Robert B. Goldberg - One of the best experts on this subject based on the ideXlab platform.
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comparative analysis of embryo proper and Suspensor transcriptomes in plant embryos with different morphologies
bioRxiv, 2020Co-Authors: Min Chen, Anhthu Q. Bui, Kelli F. Henry, Nestor Apuya, John J. Harada, Jeryoung Lin, Julie M Pelletier, Shawn Cokus, Matteo Pellegrini, Robert B. GoldbergAbstract:An important question is what genes govern the differentiation of plant embryos into Suspensor and embryo-proper regions following fertilization and division of the zygote. We compared embryo proper and Suspensor transcriptomes of four plants that vary in embryo morphology within the Suspensor region. We determined that genes encoding enzymes in several metabolic pathways leading to the formation of hormones, such as gibberellic acid, and other metabolites are up-regulated in giant Scarlet Runner Bean and Common Bean Suspensors. Genes involved in transport and Golgi body organization are up-regulated within the Suspensors of these plants as well - strengthening the view that giant specialized Suspensors serve as a hormone factory and a conduit for transferring substances to the developing embryo proper. By contrast, genes controlling transcriptional regulation, development, and cell division are up-regulated primarily within the embryo proper. Transcriptomes from less specialized soybean and Arabidopsis Suspensors demonstrated that fewer genes encoding metabolic enzymes and hormones are up-regulated. Genes active in the embryo proper, however, are functionally similar to those active in Scarlet Runner Bean and Common Bean embryo proper regions. We uncovered a set of Suspensor- and embryo-proper-specific transcription factors (TFs) that are shared by all embryos irrespective of morphology, suggesting that they are involved in early differentiation processes common to all plants. ChIP-Seq experiments with Scarlet Runner Bean and soybean WOX9, an up-regulated Suspensor TF, gained entry into a regulatory network important for Suspensor development irrespective of morphology. SignificanceHow plant embryos are differentiated into embryo proper and Suspensor regions following fertilization is a major unanswered question. The Suspensor is unique because it can vary in morphology in different plant species. We hypothesized that regulatory genes controlling the specification of embryo proper and Suspensor regions should be shared by all plants irrespective of embryo morphology. We compared embryo proper and Suspensor transcriptomes of plants with distinct Suspensor morphologies. Scarlet Runner Bean and Common Bean have highly specialized giant Suspensor regions, whereas soybean and Arabidopsis Suspensors are smaller and less specialized. We uncovered a small set of embryo-proper- and Suspensor-specific transcription factors shared by all embryos irrespective of morphology, suggesting that they play an important role in early embryo differentiation.
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A shared cis-regulatory module activates transcription in the Suspensor of plant embryos.
Proceedings of the National Academy of Sciences, 2018Co-Authors: Kelli F. Henry, Anhthu Q. Bui, Tomokazu Kawashima, Robert B. GoldbergAbstract:The mechanisms controlling the transcription of gene sets in specific regions of a plant embryo shortly after fertilization remain unknown. Previously, we showed that G564 mRNA, encoding a protein of unknown function, accumulates to high levels in the giant Suspensor of both Scarlet Runner Bean (SRB) and Common Bean embryos, and a cis-regulatory module containing three unique DNA sequences, designated as the 10-bp, Region 2, and Fifth motifs, is required for G564 Suspensor-specific transcription [Henry KF, et al. (2015) Plant Mol Biol 88:207-217; Kawashima T, et al. (2009) Proc Natl Acad Sci USA 106:3627-3632]. We tested the hypothesis that these motifs are also required for transcription of the SRB GA 20-oxidase gene, which encodes a gibberellic acid hormone biosynthesis enzyme and is coexpressed with G564 at a high level in giant bean Suspensors. We used deletion and gain-of-function experiments in transgenic tobacco embryos to show that two GA 20-oxidase DNA regions are required for Suspensor-specific transcription, one in the 5' UTR (+119 to +205) and another in the 5' upstream region (-341 to -316). Mutagenesis of sequences in these two regions determined that the cis-regulatory motifs required for G564 Suspensor transcription are also required for GA 20-oxidase transcription within the Suspensor, although the motif arrangement differs. Our results demonstrate the flexibility of motif positioning within a cis-regulatory module that activates gene transcription within giant bean Suspensors and suggest that G564 and GA 20-oxidase comprise part of a Suspensor gene regulatory network.
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A shared cis-regulatory module activates transcription in the Suspensor of plant embryos
2018Co-Authors: Kelli F. Henry, Anhthu Q. Bui, Tomokazu Kawashima, Robert B. GoldbergAbstract:The mechanisms controlling the transcription of gene sets in specific regions of a plant embryo shortly after fertilization remain unknown. Previously, we showed that G564 mRNA, encoding a protein of unknown function, accumulates to high levels in the giant Suspensor of both Scarlet Runner Bean (SRB) and Common Bean embryos, and a cis-regulatory module containing three unique DNA sequences, designated as the 10-bp, Region 2, and Fifth motifs, is required for G564 Suspensor-specific transcription [Henry, K. F. et al., Plant Mol. Biol. 88(3):207-217 (2015); Kawashima, T. et al., Proc. Natl. Acad. Sci USA 106(9):3627-3632 (2009)]. We tested the hypothesis that these motifs are also required for transcription of the SRB GA 20-oxidase gene, which encodes a gibberellic acid hormone biosynthesis enzyme and is co-expressed with G564 at a high level in giant bean Suspensors. We used deletion and gain-of-function experiments in transgenic tobacco embryos to show that two GA 20-oxidase DNA regions are required for Suspensor-specific transcription − one in the 5′ untranslated region (UTR) (+119 to +205) and another in the 5′ upstream region (-341 to -316). Mutagenesis of sequences in these two regions determined that the cis-regulatory motifs required for G564 Suspensor transcription are also required for GA 20-oxidase transcription within the Suspensor, although the motif arrangement differs. Our results demonstrate the flexibility of motif positioning within a cis-regulatory module that activates gene transcription within giant bean Suspensors, and suggest that G564 and GA 20-oxidase comprise part of a Suspensor gene regulatory network.
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A cis-regulatory module activating transcription in the Suspensor contains five cis-regulatory elements
Plant Molecular Biology, 2015Co-Authors: Kelli F. Henry, Tomokazu Kawashima, Robert B. GoldbergAbstract:Little is known about the molecular mechanisms by which the embryo proper and Suspensor of plant embryos activate specific gene sets shortly after fertilization. We analyzed the upstream region of the Scarlet Runner Bean ( Phaseolus coccineus ) G564 gene in order to understand how genes are activated specifically in the Suspensor during early embryo development. Previously, we showed that a 54-bp fragment of the G564 upstream region is sufficient for Suspensor transcription and contains at least three required cis -regulatory sequences, including the 10-bp motif (5′-GAAAAGCGAA-3′), the 10 bp-like motif (5′-GAAAAACGAA-3′), and Region 2 motif (partial sequence 5′-TTGGT-3′). Here, we use site-directed mutagenesis experiments in transgenic tobacco globular-stage embryos to identify two additional cis -regulatory elements within the 54-bp cis -regulatory module that are required for G564 Suspensor transcription: the Fifth motif (5′-GAGTTA-3′) and a third 10-bp-related sequence (5′-GAAAACCACA-3′). Further deletion of the 54-bp fragment revealed that a 47-bp fragment containing the five motifs (the 10-bp, 10-bp-like, 10-bp-related, Region 2 and Fifth motifs) is sufficient for Suspensor transcription, and represents a cis -regulatory module. A consensus sequence for each type of motif was determined by comparing motif sequences shown to activate Suspensor transcription. Phylogenetic analyses suggest that the regulation of G564 is evolutionarily conserved. A homologous cis -regulatory module was found upstream of the G564 ortholog in the Common Bean ( Phaseolus vulgaris ), indicating that the regulation of G564 is evolutionarily conserved in closely related bean species.
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A cis -regulatory module activating transcription in the Suspensor contains five cis -regulatory elements
Plant Molecular Biology, 2015Co-Authors: Kelli F. Henry, Tomokazu Kawashima, Robert B. GoldbergAbstract:Little is known about the molecular mechanisms by which the embryo proper and Suspensor of plant embryos activate specific gene sets shortly after fertilization. We analyzed the upstream region of the Scarlet Runner Bean (Phaseolus coccineus) G564 gene in order to understand how genes are activated specifically in the Suspensor during early embryo development. Previously, we showed that a 54-bp fragment of the G564 upstream region is sufficient for Suspensor transcription and contains at least three required cis-regulatory sequences, including the 10-bp motif (5′-GAAAAGCGAA-3′), the 10 bp-like motif (5′-GAAAAACGAA-3′), and Region 2 motif (partial sequence 5′-TTGGT-3′). Here, we use site-directed mutagenesis experiments in transgenic tobacco globular-stage embryos to identify two additional cis-regulatory elements within the 54-bp cis-regulatory module that are required for G564 Suspensor transcription: the Fifth motif (5′-GAGTTA-3′) and a third 10-bp-related sequence (5′-GAAAACCACA-3′). Further deletion of the 54-bp fragment revealed that a 47-bp fragment containing the five motifs (the 10-bp, 10-bp-like, 10-bp-related, Region 2 and Fifth motifs) is sufficient for Suspensor transcription, and represents a cis-regulatory module. A consensus sequence for each type of motif was determined by comparing motif sequences shown to activate Suspensor transcription. Phylogenetic analyses suggest that the regulation of G564 is evolutionarily conserved. A homologous cis-regulatory module was found upstream of the G564 ortholog in the Common Bean (Phaseolus vulgaris), indicating that the regulation of G564 is evolutionarily conserved in closely related bean species. Electronic supplementary material The online version of this article (doi:10.1007/s11103-015-0308-z) contains supplementary material, which is available to authorized users.
David W. Meinke - One of the best experts on this subject based on the ideXlab platform.
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Development of the Suspensor: Differentiation, Communication, and Programmed Cell Death During Plant Embryogenesis
Advances in Cellular and Molecular Biology of Plants, 1997Co-Authors: Brian W. Schwartz, Daniel M. Vernon, David W. MeinkeAbstract:The Suspensor functions early in embryogenesis to provide physical support, nutrition, and growth regulators to the developing embryo proper. In most plants, the Suspensor is derived from the basal cell produced following asymmetric division of the zygote. Cellular differences between the Suspensor and embryo proper may result from morphogenetic gradients established prior to division of the zygote. The Suspensor develops rapidly with respect to the embryo proper and becomes the first differentiated embryonic structure produced during seed development. The Suspensor later undergoes programmed cell death and is not present in mature seeds. Several abnormal Suspensor mutants of Arabidopsis have been identified in which the Suspensor fails to undergo programmed cell death and instead proliferates to form a structure with features characteristic of the embryo proper. Analysis of these mutants suggests that communication with the embryo proper is required early in embryogenesis for maintenance of Suspensor cell identity and later in Suspensor development for initiation of programmed cell death. The pattern of embryogenic transformation observed in these mutants indicates that Suspensor cells have the potential to recapitulate the entire spectrum of developmental programs normally restricted to the embryo proper. During normal development, interactions with the embryo proper appear to inhibit embryogenic programs, allowing Suspensor cell identity to be maintained. Based on these observations, we propose that negative regulation of developmental potential plays a major role in Suspensor cell differentiation and that the Suspensor may serve as a valuable system for addressing mechanisms of cell differentiation and cellular communication during plant development.
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Disruption of morphogenesis and transformation of the Suspensor in abnormal Suspensor mutants of Arabidopsis
Development (Cambridge England), 1994Co-Authors: Brian W. Schwartz, Edward C. Yeung, David W. MeinkeAbstract:The Suspensor is the first differentiated structure produced during plant embryogenesis. In most angiosperms, the Suspensor functions early in development to provide nutrients and growth regulators to the embryo proper. In Arabidopsis, the Suspensor undergoes programmed cell death at the torpedo stage and is not present in mature seeds. We have identified at least 16 embryo-defective mutants of Arabidopsis that exhibit an enlarged Suspensor phenotype at maturity. In this report, we focus on seven abnormal Suspensor mutants, which define three genetic loci (sus1, sus2 and sus3). Recessive mutations at each of these loci disrupt morphogenesis in the embryo proper and consistently result in the formation of a large Suspensor. Defects in the embryo proper appear by the globular stage of development; abnormalities in the Suspensor are detected soon after at the heart stage. Storage protein and lipid bodies, which normally accumulate only in the embryo proper late in embryogenesis, are present in both the arrested embryo proper and enlarged Suspensor. Therefore, cell differentiation in the embryo proper can proceed in the absence of normal morphogenesis, and the Suspensor can be transformed into a structure with features normally restricted to the embryo proper. These observations are consistent with a model in which normal development of the embryo proper limits growth and differentiation of the Suspensor. Altered development of the embryo proper in mutant seeds leads indirectly to proliferation of Suspensor cells and expression of properties characteristic of the embryo proper. Ultimately, growth of the transformed Suspensor is limited by the same genetic defect that disrupts development of the embryo proper. The availability of multiple alleles of sus1 and sus2, including T-DNA tagged alleles of each, will facilitate the cloning of these essential genes and molecular analysis of interactions between the embryo proper and Suspensor early in development.
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EMBRYOGENIC TRANSFORMATION OF THE Suspensor IN TWIN, A POLYEMBRYONIC MUTANT OF ARABIDOPSIS
Developmental Biology, 1994Co-Authors: Daniel M. Vernon, David W. MeinkeAbstract:Spontaneous twinning is a widespread but infrequent phenomenon in higher plants. We describe here a mutant of Arabidopsis thaliana, twin, that yields an unusually high frequency of viable twin and occasional triplet seedlings. Supernumerary embryos of twin arise through a novel mechanism: transformation of cells within the Suspensor, a differentiated structure established early in embryogenesis. Twin embryos develop in tandem within the seed, connected by intact segments of the Suspensor. Transformed Suspensor cells appear to duplicate the patterns of cell division and developmental pathways characteristic of zygotic embryogenesis. In addition to polyembryony, mutant embryos exhibit a number of developmental defects, including irregular patterns of cell division and abnormal morphology. The TWIN locus therefore appears to be required for normal development of the embryo proper as well as suppression of embryogenic potential in the Suspensor. The development of viable secondary embryos in twin demonstrates that cells of the Arabidopsis Suspensor can successfully establish embryonic polarity and complete the full spectrum of developmental programs normally restricted to the embryo proper. In addition, the twin phenotype indicates that disruption of a single genetic locus can result in the conversion of a single terminally differentiated cell type to an embryogenic state.
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Embryogenesis in Angiosperms: Development of the Suspensor.
The Plant Cell, 1993Co-Authors: Edward C. Yeung, David W. MeinkeAbstract:The zygote in flowering plants usually divides transversely to form a terminal cell, which gives rise to the embryo proper, and a vacuolated basal cell, which often divides rapidly to form a structure known as the Suspensor. Angiosperm Suspensors vary widely in size and morphology from a single cell to a massive column of several hundred cells (Maheshwari, 1950; Wardlaw, 1955; Lersten, 1983). In most cases, the Suspensor functions early in embryogenesis and then degenerates during later stages of development and is not present in the mature seed. Classically, the Suspensor was thought to play a passive role in embryo development by holding the embryo proper in a fixed position within the seed (Maheshwari, 1950). It now appears from extensive structural, biochemical, and physiological studies with a variety of angiosperms that the Suspensor plays an active role early in development by promoting continued growth of the embryo proper. In addition, growth of the Suspensor during early stages of development may be inhibited by the embryo proper (Marsden and Meinke, 1985). Analysis of reproductive development in angiosperms must therefore include a consideration of developmental interactions that occur between the embryo proper and Suspensor. Although the Suspensor appears to play a critical role in zygotic embryogenesis, it usually fails to develop when somatic embryos are produced in culture. The Suspensor should therefore be viewed as a specialized structure that functions primarily to facilitate continued development of the embryo proper within the seed. In this review, we present an overview of the structure and function of the angiosperm Suspensor and discuss recent attempts to analyze the development of the Suspensor through a combination of descriptive, experimental, and genetic approaches. The recent identification of a large collection of Arabidopsis mutants with abnormal Suspensors provides a unique opportunity to examine the underlying genetic factors that influence Suspensor development.
Hamako Sasamoto - One of the best experts on this subject based on the ideXlab platform.
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Two stimulatory effects of the peptidyl growth factor phytosulfokine during somatic embryogenesis in Japanese larch (Larix leptolepis Gordon)
Plant Science, 2005Co-Authors: Mikihisa Umehara, Shinjiro Ogita, Hamako Sasamoto, Chang-ho Eun, Yoshikatsu Matsubayashi, Youji Sakagami, Hiroshi KamadaAbstract:Abstract In contrast to angiosperms, some gymnosperms form well-development Suspensors during somatic embryogenesis. This feature is highly useful to studies of Suspensor biology. In cell cultures of Japanese larch ( Larix leptolepis Gordon), somatic embryos rarely formed when the initial cell density was lower than 0.1 ml packed cell volume (PCV) l −1 . However, in the presence of phytosulfokine (PSK), a peptidyl plant growth factor, mitotic activity during somatic embryogenesis was stimulated, even when the cell density was lower than 0.1 ml PCV l −1 , particularly, the development of the Suspensor. Manual separation of somatic embryos into the embryo proper and the Suspensor arrested further development, but when embryos proper lacking a Suspensor were treated with PSK, the Suspensor regenerated and development proceeded to maturity. Because no division of the Suspensor cells was observed, the cells of the regenerated Suspensor probably originated from basal cells of the embryo proper. In contrast, PSK treatment of Suspensors lacking the embryo proper did not stimulate further development. These results indicate that PSK stimulates not only cell division of embryo proper but also development of the Suspensor.
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an in vitro culture system used to investigate possible interactions between the embryo proper and the Suspensor in embryogenesis in japanese larch larix leptolepis gordon
Plant Biotechnology, 2004Co-Authors: Mikihisa Umehara, Shinjiro Ogita, Hamako Sasamoto, Hiroshi KamadaAbstract:It has been proposed that the Suspensor has important roles in early embryogenesis in seed plants. However, the roles of the Suspensor are not well understood, because the development of zygotic embryos normally occurs deep within both the endosperm and the maternal cells. In this paper, we report the development of an in vitro culture system to investigate the roles of the Suspensor in the development of the embryo proper, using a somatic embryogenesis system with Japanese larch (Larix leptolepis GORDON). Our results indicate that the Suspensor is essential for the normal development of somatic embryos of this species. This method provides a useful experimental system to investigate the interactions between the embryo proper and the Suspensor.
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Inhibitory Factor(s) of Somatic Embryogenesis Regulated Suspensor Differentiation in Suspension Culture of Japanese Larch(Larix leptolepis GORDON)
Plant Biotechnology, 2004Co-Authors: Mikihisa Umehara, Shinjiro Ogita, Hamako Sasamoto, Hiroshi KamadaAbstract:Using somatic embryogenesis system of Japanese larch that develops embryos composed of embryo-proper and Suspensor, the effects of high-cell-density culture and conditioned medium on the somatic embryogenesis were investigated. High-cell-density culture strongly inhibited the somatic embryogenesis. Furthermore, the conditioned medium derived from high-cell-density culture also strongly inhibited the somatic embryogenesis, especially differentiation of the Suspensor. The inhibitory effect of the conditioned medium was not attributable to the depletion of nutrients, but to the accumulation of inhibitory factor(s) in the medium. The addition of activated charcoal to high-cell-density culture resulted in the formation of numerous somatic embryos with longer Suspensors than in the untreated one. This treatment also resulted in the formation of numerous vacuolated cells-like Suspensor on the surface surrounding the embryo-proper. These results indicate that some inhibitory factor(s) that regulates Suspensor differentiation are released into the medium of high cell density.
