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Robert B. Goldberg - One of the best experts on this subject based on the ideXlab platform.

  • Using Giant Scarlet Runner Bean (Phaseolus coccineus) Embryos to Dissect the Early Events in Plant Embryogenesis.
    Methods in Molecular Biology, 2020
    Co-Authors: Min Chen, Anhthu Q. Bui, Robert B. Goldberg
    Abstract:

    The giant Embryo of the scarlet runner bean (Phaseolus coccineus) has been used historically to investigate the molecular and developmental processes that control the early events of plant Embryo development. In more recent years, our laboratory has been using scarlet runner bean Embryos to uncover the genes and regulatory events that control Embryo Proper and suspensor region differentiation shortly after fertilization. In this chapter we describe methods that we have developed to isolate scarlet runner bean Embryos at the globular stage of development, and capture Embryo Proper and suspensor regions by either hand dissection or laser capture microdissection (LCM) for use in downstream genomic analysis. These methods are also applicable for use in investigating the early events of common bean (Phaseolus vulgaris) Embryo development, a close relative of scarlet runner bean, which also has a giant Embryo in addition to a sequenced genome.

  • Using giant scarlet runner bean Embryos to uncover regulatory networks controlling suspensor gene activity
    Frontiers in Plant Science, 2015
    Co-Authors: Kelli F. Henry, Robert B. Goldberg
    Abstract:

    One of the major unsolved issues in plant development is understanding the regulatory networks that control the differential gene activity that is required for the specification and development of the two major Embryonic regions, the Embryo Proper and suspensor. Historically, the giant Embryo of scarlet runner bean (SRB), Phaseolus coccineus, has been used as a model system to investigate the physiological events that occur early in Embryogenesis – focusing on the question of what role the suspensor region plays. A major feature distinguishing SRB Embryos from those of other plants is a highly enlarged suspensor containing at least 200 cells that synthesize growth regulators required for subsequent Embryonic development. Recent studies have exploited the giant size of the SRB Embryo to micro-dissect the Embryo Proper and suspensor regions in order to use genomics-based approaches to identify regulatory genes that may be involved in controlling suspensor and Embryo Proper differentiation, as well as the cellular processes that may be unique to each Embryonic region. Here we review the current genomics resources that make SRB Embryos a compelling model system for studying the early events required to program Embryo development.

  • Cell Differentiation and Morphogenesis Are Uncoupled in Arabidopsis raspberry Embryos.
    The Plant Cell, 1994
    Co-Authors: Ramin Yadegari, Grd. Paiva, T. Laux, A. M. Koltunow, Nestor Apuya, J. L. Zimmerman, R. L. Fischer, John J. Harada, Robert B. Goldberg
    Abstract:

    We identified two Arabidopsis Embryo mutants, designated as raspberry1 and raspberry2, by screening T-DNA-mutagenized Arabidopsis lines. Embryogenesis in these mutants is indistinguishable from that of wild-type plants until the late-globular stage, after which raspberry1 and raspberry2 Embryos fail to undergo the transition to heart stage, remain globular shaped, and proliferate an enlarged suspensor region. raspberry1 and raspberry2 Embryo-Proper regions enlarge during Embryogenesis, become highly vacuolate, and display prominent convex, or "raspberry-like" protuberances on their outer cell layers. In situ hybridization studies with several Embryo cell-specific mRNA probes indicated that the raspberry1 and raspberry2 Embryo-Proper regions differentiate tissue layers in their correct spatial contexts and that the regulation of cell-specific genes within these layers is normal. Surprisingly, a similar spatial and temporal pattern of mRNA accumulation occurs within the enlarged suspensor region of raspberry1 and raspberry2 Embryos, suggesting that a defect in Embryo-Proper morphogenesis can cause the suspensor to take on an Embryo-Proper-like state and differentiate a radial tissue-type axis. We conclude that cell differentiation can occur in the absence of both organ formation and morphogenesis during plant Embryogenesis and that interactions occur between the Embryo-Proper and suspensor regions.

Edward C. Yeung - One of the best experts on this subject based on the ideXlab platform.

  • Dynamic distribution and the role of abscisic acid during seed development of a lady's slipper orchid, Cypripedium formosanum.
    Annals of Botany, 2015
    Co-Authors: Yung-i Lee, Edward C. Yeung, Mei-chu Chung, Nean Lee
    Abstract:

    Background and Aims Although abscisic acid (ABA) is commonly recognized as a primary cause of seed dormancy, there is a lack of information on the role of ABA during orchid seed development. In order to address this issue, the localization and quantification of ABA were determined in developing seeds of Cypripedium formosanum. Methods The endogenous ABA profile of seeds was measured by enzyme-linked immunosorbent assay (ELISA). Temporal and spatial distributions of ABA in developing seeds were visualized by immunohistochemical staining with monoclonal ABA antibodies. Fluoridone was applied to test the causal relationship between ABA content and seed germinability. Key Results ABA content was low at the proEmbryo stage, then increased rapidly from 120 to 150 days after pollination (DAP), accompanied by a progressive decrease in water content and seed germination. Immunofluorescence signals indicated an increase in fluorescence over time from the proEmbryo stage to seed maturation. From immunogold labelling, gold particles could be seen within the cytoplasm of Embryo-Proper cells during the early stages of seed development. As seeds approached maturity, increased localization of gold particles was observed in the periplasmic space, the plasmalemma between Embryo-Proper cells, the surface wall of the Embryo Proper, and the inner walls of inner seed-coat cells. At maturity, gold particles were found mainly in the apoplast, such as the surface wall of the Embryo Proper, and the shrivelled inner and outer seed coats. Injection of fluoridone into capsules resulted in enhanced germination of mature seeds. Conclusions The results indicate that ABA is the key inhibitor of germination in C. formosanum. The distinct accumulation pattern of ABA suggests that it is synthesized in the cytosol of Embryo cells during the early stages of seed development, and then exported to the apoplastic region of the cells for subsequent regulatory processes as seeds approach maturity.

  • The osmotic Property and fluorescent tracer movement of developing orchid Embryos of Phaius tankervilliae (Aiton) Bl.
    Sexual Plant Reproduction, 2010
    Co-Authors: Yung-i Lee, Edward C. Yeung
    Abstract:

    The suspensor plays an active role during the early Embryo development of flowering plants. In orchids, the suspensor cells are highly vacuolated without structural specializations, and the possible mechanism(s) that enable the suspensor to serve as the nutrient uptake site is virtually unknown. Here, we used the fluorescent tracer CFDA to characterize the pathway for symplastic transport in the suspensor cells of developing Embryos and to provide direct visual evidence that the orchid suspensor has unique physiological Properties. The Embryo Proper uptakes the fluorescent dye through the suspensor. CF could first be detected throughout the suspensor cell and then subsequently in the Embryo Proper. A plasmolysis experiment clearly indicates that suspensor cells have a more negative osmotic potential than the adjoining testa cells. It is proposed that the preferential entry of CFDA into the suspensor cell of the Nun orchid is aided by the more negative osmotic potential of the suspensor than neighboring cells, providing a driving force for the uptake of water from the apoplast into the symplast.

  • Embryology of Phalaenopsis amabilis var. formosa: Embryo development
    Botanical Studies, 2008
    Co-Authors: Yung-i Lee, Edward C. Yeung, Nean Lee, Mei-chu Chung
    Abstract:

    Phalaenopsis amabilis var. formosa is an endemic epiphytic orchid variety native to Taitung and Lanyu of Taiwan. A ⊥-shaped, four-celled Embryo is produced by two successive cell divisions of a zygote. Soon after, two of the four cells toward the micropyle enlarge and divide two more times resulting in the formation of eight tubular suspensor cells. The suspensor cells are highly vacuolated; the bottom tier of suspensor cells elongates towards the micropyle, and the upper tier elongates towards the chalazal end of the seed. During the early stages of Embryo development, lipid droplets appear in the elongating suspensor cells and disappear soon afterwards, indicating the suspensor functions in nutrient uptake and as a temporary food storage site for the developing Embryo. In the mature seed, a differentiated apical zone containing the relatively small cells can be seen in the Embryo Proper. Protein and lipid bodies are the main storage products in the Embryo Proper cells. The results of Nile red staining indicate that a cuticular layer is present only on the surface walls of the Embryo Proper, but is absent from the suspensor cell wall Cuticular material is also present in the outermost layer of the seed coat and persists through seed maturation.

  • Embryo Development in the Lady's Slipper Orchid, Paphiopedilum delenatii, with Emphasis on the Ultrastructure of the Suspensor
    Annals of Botany, 2006
    Co-Authors: Yung-i Lee, Edward C. Yeung, Nean Lee, Mei-chu Chung
    Abstract:

    • Background and Aims Owing to large-scale collecting, the lady's slipper orchid, Paphiopedilum delenatii, is under threat of extinction. Asymbiotic germination provides a useful way to re-establish plants in the wild and for commercial propagation. A detailed study of Embryo development would provide information on subsequent germination events and aid in the propagation of the species. • Methods Developing capsules were collected for histochemical and ultrastructural studies by using both light and transmission electron microscopy. • Key Results The suspensor of this species consists of three vacuolated cells. During the early globular stage of Embryo development, structural differentiation occurs, revealing an abundance of smooth endoplasmic reticulum cisternae and wall ingrowths within the suspensor cells. These features are not present in cells of the Embryo Proper. Furthermore, the results of Nile red staining demonstrate that a cuticular layer is present only in the Embryo Proper, but absent from the suspensor. Cuticular material is also present in the inner walls of the seed coat, and persists through seed maturation. • Conclusions The morphological features of the transfer cell and the absence of cuticular material in the suspensor cell wall corroborate the hypothesis that the suspensor is the major nutrient uptake site for the developing Embryo in the lady's slipper orchid. The absence of an endosperm and presence of cuticular material in the inner walls of the seed coat enclosing the Embryo Proper further support the notion that nutrient uptake by the Embryo is confined to the micropylar end of the seed through the suspensor.

  • Zygotic Embryo development in Daucus carota
    Canadian Journal of Botany, 1996
    Co-Authors: Sharon Lackie, Edward C. Yeung
    Abstract:

    After fertilization, the zygote divided unequally, giving rise to a larger basal cell and a smaller terminal cell. Derivatives from the basal cell gave rise to the suspensor and the terminal cell gave rise to the Embryo Proper. The suspensor usually consisted of a uniseriate file of 10–12 cells. However, additional anticlinal and oblique divisions resulted in some suspensors having more than one cell file. Cuticular substance was not present in the suspensor cell wall. The Embryo Proper was derived from the terminal four cells of the eight-celled Embryo. The protoderm differentiated first, and subsequent to its formation cuticular substance could be detected in the outer tangential walls using the Nile red stain. This staining pattern intensified as the Embryo matured. A defined cell lineage was not associated with tissue and meristem differentiation. Meristems began to form at the heart stage and became clearly defined at the late heart – early cotyledon stage. Keywords: cuticular material, Daucus carota...

James Palis - One of the best experts on this subject based on the ideXlab platform.

  • 18 Circulation Plays an Essential Role in Distributing Hematopoietic Progenitors from the Yolk Sac to the Embryo Proper; Lessons from the Ncx1-Null Mouse.
    Pediatric Research, 2006
    Co-Authors: Christopher T. Lux, Kathleen E. Mcgrath, James Palis, Momoko Yoshimoto, Simon J. Conway, Mervin C. Yoder
    Abstract:

    18 Circulation Plays an Essential Role in Distributing Hematopoietic Progenitors from the Yolk Sac to the Embryo Proper; Lessons from the Ncx1-Null Mouse.

  • Yolk Sac Development in Mice
    Hematopoietic Stem Cell Development, 2006
    Co-Authors: James Palis
    Abstract:

    A functional cardiovascular system is essential for survival and growth of the mammalian Embryo, so the hematopoietic, vascular, and cardiac organ systems are the first to emerge in early post-implantation development.1 During gastrulation, mesoderm cells create the body plan, forming red blood cells in the yolk sac, the heart and aorta in the Embryo Proper, and a vascular network to connect the two. In this chapter, the development of the hematopoietic system in the yolk sac of the mouse will be reviewed.

  • Circulation Plays an Essential Role in Distributing Mammalian Yolk Sac Definitive Hematopoietic Progenitor Cells to the Embryo Proper; Using the Ncx1 Knockout Mouse Model To Prevent Circulation.
    Blood, 2005
    Co-Authors: Christopher T. Lux, Kathleen E. Mcgrath, James Palis, Simon J. Conway, Mervin C. Yoder
    Abstract:

    The yolk sac is the lone site of primitive hematopoiesis. The role of the yolk sac in generating definitive hematopoietic progenitors, however, has remained controversial. One complicating factor preventing an accurate investigation of this subject has been the onset of early circulation which alters the localization of hematopoietic progenitors. An Ncx1 knockout mouse (which fails to initiate a heartbeat) is used here to investigate the temporal and spatial distribution of definitive hematopoietic progenitor cells (HPCs: adult type BFU-E, CFU-GM, CFU-GEMM) in an environment lacking circulation. Embryos were harvested from timed pregnancies from Ncx1 heterozygote crosses beginning at the onset of circulation 8.5 days post conception (E8.5) and ending 36 hours later (E10). Developmental age was determined by somite pair number. All Embryos were carefully separated from their yolk sacs and both samples were digested and plated in methylcellulose using a previously published definitive hematopoietic progenitor colony assay. Colonies were counted at seven days and then collected for genotyping. In Embryos of all genotypes at E8.5, definitive HPCs were enriched more than 28 fold in the yolk sac compared to the Embryo Proper (EP), but following redistribution by a functional circulation in E10 wild type and heterozygous Embryos, the ratio drops to a 3 fold enrichment in the yolk sac (similar to the 3–5 fold enrichment previously reported at this age; KM & JP, Blood 2003). Ncx1 null Embryos lacking circulation produced few HPCs in the EP and never redistribute the HPCs as late as E10 resulting in a 72 fold enrichment in the yolk sac even at E10. Whole mount ζ-hemoglobin mRNA staining was carried out to visualize the distribution of blood cells in the yolk sac and Embryo Proper in the presence and absence of circulation. The staining pattern in null Embryos confirms that cells from the yolk sac blood band remain in the yolk sac and are not found in the EP. Our findings support a model in which the primitive and definitive hematopoietic progenitors are generated in the yolk sac and are only redistributed to the EP upon the onset of circulation. Not only is the yolk sac an important source of definitive HPCs, it is the developing Embryo’s primary source through E10.

  • Circulation is established in a stepwise pattern in the mammalian Embryo
    Blood, 2003
    Co-Authors: Kathleen E. Mcgrath, Anne Koniski, Jeffrey Malik, James Palis
    Abstract:

    To better understand the relationship between the Embryonic hematopoietic and vascular systems, we investigated the establishment of circulation in mouse Embryos by examining the redistribution of yolk sac-derived primitive erythroblasts and definitive hematopoietic progenitors. Our studies revealed that small numbers of erythroblasts first enter the Embryo Proper at 4 to 8 somite pairs (sp) (Embryonic day 8.25 [E8.25]), concomitant with the proposed onset of cardiac function. Hours later (E8.5), most red cells remained in the yolk sac. Although the number of red cells expanded rapidly in the Embryo Proper, a steady state of approximately 40% red cells was not reached until 26 to 30 sp (E10). Additionally, erythroblasts were unevenly distributed within the Embryo's vasculature before 35 sp. These data suggest that fully functional circulation is established after E10. This timing correlated with vascular remodeling, suggesting that vessel arborization, smooth muscle recruitment, or both are required. We also examined the distribution of committed hematopoietic progenitors during early Embryogenesis. Before E8.0, all progenitors were found in the yolk sac. When normalized to circulating erythroblasts, there was a significant enrichment (20- to 5-fold) of progenitors in the yolk sac compared with the Embryo Proper from E9.5 to E10.5. These results indicated that the yolk sac vascular network remains a site of progenitor production and preferential adhesion even as the fetal liver becomes a hematopoietic organ. We conclude that a functional vascular system develops gradually and that specialized vascular-hematopoietic environments exist after circulation becomes fully established.

  • Onset of Cardiac Function During Early Mouse Embryogenesis Coincides With Entry of Primitive Erythroblasts Into the Embryo Proper
    Circulation Research, 2003
    Co-Authors: Colin K.l. Phoon, Orlando Aristizabal, Kathleen E. Mcgrath, James Palis, Daniel H. Turnbull
    Abstract:

    When cardiac function and blood flow are first established are fundamental questions in mammalian Embryogenesis. The earliest erythroblasts arise in yolk sac blood islands and subsequently enter the Embryo Proper to initiate circulation. Embryos staged 0 to 30 somites (S) were examined in utero with 40- to 50-MHz ultrasound biomicroscopy (UBM)-Doppler, to determine onset of Embryonic heartbeat and blood flow and to characterize basic physiology of the very early mouse Embryonic circulation. A heartbeat was first detected at 5 S, and blood vascular flow at 7 S. Heart rate, peak arterial velocity, and velocity-time integral showed progressive increases that indicated a dramatically increasing cardiac output from even the earliest stages. In situ hybridization revealed an onset of the heartbeat coincident with the appearance of yolk sac–derived erythroblasts in the Embryo Proper at 5 S. Early maturation of the circulation follows a tightly coordinated program.

David W. Meinke - One of the best experts on this subject based on the ideXlab platform.

  • Development of the Suspensor: Differentiation, Communication, and Programmed Cell Death During Plant Embryogenesis
    Advances in Cellular and Molecular Biology of Plants, 1997
    Co-Authors: Brian W. Schwartz, Daniel M. Vernon, David W. Meinke
    Abstract:

    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.

  • Disruption of morphogenesis and transformation of the suspensor in abnormal suspensor mutants of Arabidopsis
    Development (Cambridge England), 1994
    Co-Authors: Brian W. Schwartz, Edward C. Yeung, David W. Meinke
    Abstract:

    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.

  • EmbryoGENIC TRANSFORMATION OF THE SUSPENSOR IN TWIN, A POLYEmbryoNIC MUTANT OF ARABIDOPSIS
    Developmental Biology, 1994
    Co-Authors: Daniel M. Vernon, David W. Meinke
    Abstract:

    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.

  • Embryogenesis in Angiosperms: Development of the Suspensor.
    The Plant Cell, 1993
    Co-Authors: Edward C. Yeung, David W. Meinke
    Abstract:

    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.

Hiroshi Kamada - One of the best experts on this subject based on the ideXlab platform.