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  • 1
    Electronic Resource
    Electronic Resource
    Nuclear cytoplasmic domains, microtubules and organelles in microsporocytes of the slipper orchid Cypripedium californicum A. Gray dividing by simultaneous cytokinesis (1996)
    Springer
    Sexual plant reproduction 9 (1996), S. 145-152 
    Details
    ISSN: 1432-2145
    Keywords: Cytokinesis ; Microtubules ; Microsporogenesis ; Orchids ; Phragmoplast ; Pollen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Microsporocytes of the slipper orchidCypripedium californicum A. Gray divide simultaneously after second meiosis. The organization and apportionment of the cytoplasm throughout meiosis are functions of nuclear-based radial microtubule systems (RMSs) that define domains of cytoplasm - a single sporocyte domain before meiosis, dyad domains within the undivided cytoplasm after first meiosis, and four spore domains after second meiosis. Organelles migrate to the interface of dyad domains in the undivided cytoplasm after first meiotic division, and second meiotic division takes place simultaneously on both sides of the equatorial organelle band. Microtubules emanating from the telophase II nuclei interact to form columnar arrrays that interconnect all four nuclei, non-sister as well as sister. Cell plates are initiated in these columns of microtubules and expand centrifugally along the interface of opposing RMSs, coalescing in the center of the sporocyte and joining with the original sporocyte wall at the periphery to form the tetrad of microspores. Organelles are distributed into the spore domains in conjunction with RMSs. These data, demonstrating that cytokinesis in microsporogenesis can occur in the absence of both components of the typical cytokinetic apparatus (the preprophase band of microtubules which predicts the division site and the phragmoplast which controls cell-plate deposition), suggest that plant nuclei have an inherent ability to establish a domain of cytoplasm via radial microtubule systems and to regulate wall deposition independently of the more complex cytokinetic apparatus of vegetative cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02221394
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  • 2
    Electronic Resource
    Electronic Resource
    Ultrastructure of meiosis in the mossRhynchostegium serrulatum I. Prophasic microtubules and spindle dynamics (1982)
    Springer
    Protoplasma 110 (1982), S. 23-33 
    Details
    ISSN: 1615-6102
    Keywords: Meiosis ; Microtubules ; Polarity ; Ultrastructure ; Mosses
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary An extensive system of microtubules develops during meiotic prophase in the mossRhynchostegium serrulatum (Hedw.)Jaeg. &Sauerb. Development of the cytoskeleton can be traced to early prophase when the nucleus is acentric and the single plastid divides into four plastids. The cytoskeletal microtubules are associated with equidistant positioning of the four plastids at the distal tetrad poles and with migration of the nucleus to a central position in the sporocyte. The cytoskeleton, which interconnects plastids and encloses the nucleus, contributes to the establishment of moss sporocyte polarity. Just prior to metaphase I evidence of the prophase cytoskeleton is lost as the bipolar metaphase I spindle develops in association with discrete polar organizers located in opposite cleavage furrows between plastids.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01314678
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  • 3
    Electronic Resource
    Electronic Resource
    Aperture development in spores of the moss,Trematodon longicollis Mx. (1981)
    Springer
    Protoplasma 106 (1981), S. 273-287 
    Details
    ISSN: 1615-6102
    Keywords: Microtubules ; Polarity ; Spore development ; Trematodon
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Young spores of the mossTrematodon longicollis Mx. are highly polar. Immediately after meiotic cytokinesis an extensive system of microtubules associated with the single plastid develops under the entire distal face. Following exine initiation on the distal surface a microtubule system is elaborated at the site of aperture development on the proximal surface. Both plastid and nucleus move from distal to proximal pole and are attached to microtubules of the proximal system. Microtubules underlie the plasma membrane as it withdraws from the exine in the initiation of both the surrounding annulus and central aperture pore. The central pore enlarges to form a bowl-shaped concavity in which a fibrillar plug develops basipetally. The annulus expands into a fibrillar-filled protrusion surrounding the central pore. The mature aperture consists of a central pore plug covered by a thin roof of exine and separated from the surrounding annulus by exine lamellae. The aperture of the mature spore is obscured by development of the ornate exine and is not a prominent feature of the mature spore surface.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01275558
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  • 4
    Electronic Resource
    Electronic Resource
    Division polarity and plasticity of the meiosis I spindle inCypripedium californicum (Orchidaceae) (1998)
    Springer
    Protoplasma 203 (1998), S. 168-174 
    Details
    ISSN: 1615-6102
    Keywords: Confocal laser scanning microscopy ; Cytoplasmic domains ; Meiosis ; Microtubules ; Organelle band ; Polarity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Establishment of division polarity and meiotic spindle organization in the lady's slipper orchidCypripedium californicum A. Gray was studied by immunocytochemistry, confocal and transmission electron microscopy. Prior to organization of the spindle for meiosis I, the cytoplasmic domains of the future dyad and spindle polarity are marked by: (1) constriction of the prophase nucleus into an hourglass shape; (2) reorganization of nuclear-based radial microtubules into two arrays that intersect at the constriction; and (3) redistribution of organelles into a ring at the boundary of the newly defined dyad domains. It is not certain whether the opposing microtubule arrays contribute directly to the anastral spindle which is organized in the perinuclear areas of the two hemispheres. By late prophase each half-spindle consists of a spline-like structure from which depart the kinetochore fibers. This peculiar spindle closely resembles the spline-like spindle of generative-cell mitosis in certain plants where the spindle is distorted by physical constraints of the slender pollen tube. In the microsporocyte, the elongate spindle of late prophase/metaphase is curved within the cell so that the poles are not actually opposite each other and chromosomes do not form a plate at the equator. By late telophase the poles of the shortened halfspindles lie opposite each other. Plasticity of the physically constrained plant spindle appears to be due to its construction from multiple units terminating in minipoles. Cytokinesis does not follow the first meiosis. However, the dyad domains are clearly defined by radial microtubules emanating from the two daughter nuclei and the domains themselves are separated by a disc-like band of organelles.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01279473
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  • 5
    Electronic Resource
    Electronic Resource
    Polarization predicts the pattern of cellularization in cereal endosperm (1996)
    Springer
    Protoplasma 192 (1996), S. 168-177 
    Details
    ISSN: 1615-6102
    Keywords: Cereals ; Endosperm ; Development ; Polarity ; Microtubules
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The endosperm of cereal grains develops as a multinucleate mass of wall-less cytoplasm (syncytium) that lines the periphery of the central cell before becoming cellular. The pattern of initial wall formation is precisely oriented and is followed by a round of precisely oriented formative cell division that gives rise to initials for the two tissues of endosperm. The initial anticlinal walls form at boundaries of nuclear-cytoplasmic domains (NCDs) defined by radial microtubules emanating from nuclei in the syncytium. Polarized growth of the NCDs in axes perpendicular to the embryo sac wall and centripetal elongation of the anticlinal walls results in a single layer of open ended alveoli overtopped by the remaining syncytial cytoplasm. This arboreal stage, so named because the elongate nucleate columns of cytoplasm resemble an orchard of trees, predicts the division polarity of the imminent formative division. Mitosis occurs as a wave which, like polarization, moves in both directions from ventral to dorsal. Spindles are oriented parallel to the long axis of the alveoli and cell plates give rise to periclinal walls. The outer daughter nuclei (aleurone initials) are thus completely enclosed by walls and the inner nuclei (starchy endosperm initials) are in alveoli adjacent to the central vacuole.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01273889
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  • 6
    Electronic Resource
    Electronic Resource
    Transition from mitotic apparatus to cytokinetic apparatus in pollen mitosis of the slipper orchid (1997)
    Springer
    Protoplasma 198 (1997), S. 43-52 
    Details
    ISSN: 1615-6102
    Keywords: Confocal microscopy ; Microtubules ; Mitosis ; Orchid ; Phragmoplast ; Pollen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Cytokinesis following asymmetrical pollen mitosis was studied in the slipper orchidCypripedium fasciculatum using techniques of immunofluorescence, confocal laser scanning, and transmission electron microscopy. Data from stereo reconstructions of double labelled preparations (microtubules/nuclei) show that the contribution of residual spindle fibers to development of the interzonal array is minor; rather, new populations of microtubules are nucleated in association with the two groups of anaphase chromosomes. As kinetochores reach the poles, trailing arms of the chromosomes and nonkinetochore microtubules are displaced outward in the equatorial zone and by early telophase the interzone is left virtually free of microtubules. The interzonal apparatus has its origin in a massive proliferation of microtubules from the polar regions and surfaces of contracting chromosomes. Each polar region appears as a hub from which microtubules radiate in a spoke-like configuration and numerous tufts of microtubules appear to emanate from margins of the chromosomes themselves. These newly organized arrays of microtubules extend to the equatorial region where they interact to form the interzonal apparatus. Increasing organization of microtubules in the interzone results in development of a typical phragmoplast configuration consisting of opposing cone-like bundles of microtubules bisected by an unstained equatorial line.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01282130
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  • 7
    Electronic Resource
    Electronic Resource
    Microtubule organization and morphogenesis in young spores of the mossTetraphis pellucida Hedw (1983)
    Springer
    Protoplasma 116 (1983), S. 115-124 
    Details
    ISSN: 1615-6102
    Keywords: Microtubules ; Moss ; MTOC ; Sporogenesis ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Microtubule systems appear sequentially at the distal and proximal poles of tetrad members during mid-sporogenesis in the mossTetraphis pellucida Hedw. The distal microtubule system emanates from a microtubule organizing center (MTOC) located between the single plastid and the nucleus. The distal MTOC and associated microtubules, which appear immediately after cytokinesis, are ephemeral and do not appear to be associated with the deposition of exine occuring at the same time. The proximal microtubule system, which appears slightly later than the distal system, is a more stable component of mid-sporogenesis. The proximal MTOC is an irregularly lobed, patelliform aggregation of electron-dense granules located beneath the plasma membrane at the proximal spore pole. Several bundles of microtubules radiate from the proximal MTOC and traverse the cell, enclosing the nucleus in an cone of microtubules. The proximal microtubule system is thought to function in aperture development and organelle migration. The relatively large nucleus migrates a short distance in the small spore early in the tetrad stage and maintains its acentric position at the proximal pole throughout later stages of sporogenesis. The plastid migrates later in the tetrad stage from its meiotic position parallel to the distal surface to a position perpendicular to the distal surface with one tip in close proximity to the proximal MTOC. The proximal microtubule system reaches its maximum development by the end of the tetrad stage and all micrographic evidence of it is lost in the maturation stages of late sporogenesis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01279828
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  • 8
    Electronic Resource
    Electronic Resource
    Plastid apportionment and preprophase microtubule bands in monoplastidic root meristem cells ofIsoetes andSelaginella (1984)
    Springer
    Protoplasma 123 (1984), S. 95-103 
    Details
    ISSN: 1615-6102
    Keywords: Microtubules ; Mitosis ; Plastids ; Preprophase Band ; Isoetes ; Selaginella
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Ultrastructural observations on monoplastidic root tip cells ofIsoetes andSelaginella demonstrate two important phenomena associated with preprophasic preparation for mitotic cell division, 1. the preprophase band and 2. precise orientation of the dividing plastid relative to the preprophase band. Both of these phenomena accurately predict the future plane of cell division. The plastid divides in a plane parallel to the spindle and each cell inherits a single plastid which caps the telophase nucleus. When succesive transverse divisions occur, the plastid migrates prior to prophase from a position near an old transverse wall to a lateral position in the cell. The plastid is oriented with its median constriction precisely intersected by the plane of the preprophase band. When a longitudinal division follows a transverse division, the plastid remains in its position adjacent to an old transverse wall where it is bisected by the plane of the longitudinally oriented preprophase band microtubules.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01283580
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  • 9
    Electronic Resource
    Electronic Resource
    Pattern and process of wall formation in developing endosperm (1995)
    New York, NY : Wiley-Blackwell
    BioEssays 17 (1995), S. 803-812 
    Details
    ISSN: 0265-9247
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Endosperm is emerging as a system for investigating the genetic control of wall placement and deposition in plant development. Development of endosperm progresses in distinct stages from a wall-less syncytial stage to a cellular stage that is entirely typical of plant meristems where the division plane is predicted by a preprophase band of microtubules (PPB) and cytokinesis is completed by formation of a cell plate in association with a phragmoplast. Four developmentally different types of walls, each associated with a different microtubule system, are sequentially produced: (1) free growing walls deposited in the absence of mitosis and phragmoplasts; (2) walls guided by cytoplasmic phragmoplasts formed adventitiously in the absence of mitosis; (3) walls formed by interzonal phragmoplasts in a cell cycle that lacks PPBs; and (4) wall deposition driven by interzonal phragmoplasts in a cycle that includes PPBs. We are using methods of differential screening to isolate cDNA clones corresponding in temporal and spatial pattern to the types of wall development, and are studying mutants for clues to the genetic controls of wall development.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bies.950170910
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