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  • 1
    ISSN: 1432-2048
    Keywords: Key words: Cell wall (endosperm) ; Development (cereal grain) ; Endosperm (development ; structure) ; Glucan (immunolocation) ; Grain development ; Oryza (cell wall)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. Immunogold labeling was used to study the distribution of (1 → 3)-β-glucans and (1 → 3, 1 → 4)-β-glucans in the rice grain during cellularization of the endosperm. At approximately 3–5 d after pollination the syncytial endosperm is converted into a cellular tissue by three developmentally distinct types of wall. The initial free-growing anticlinal walls, which compartmentalize the syncytium into open-ended alveoli, are formed in the absence of mitosis and phragmoplasts. This stage is followed by unidirectional (centripetal) growth of the anticlinal walls mediated by adventitious phragmoplasts that form between adjacent interphase nuclei. Finally, the periclinal walls that divide the alveoli are formed in association with centripetally expanding interzonal phragmoplasts following karyokinesis. The second and third types of wall are formed alternately until the endosperm is cellular throughout. All three types of wall that cellularize the endosperm contain (1 → 3)-β-glucans but not (1 → 3, 1 → 4)-β-glucans, whereas cell walls in the surrounding maternal tissues contain considerable amounts of (1 → 3, 1 → 4)-β-glucans with (1 → 3)-β-glucans present only around plasmodesmata. The callosic endosperm walls remain thin and cell plate-like throughout the cellularization process, appearing to exhibit a prolonged juvenile state.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Sexual plant reproduction 12 (1999), S. 32-42 
    ISSN: 1432-2145
    Keywords: Key words Arabidopsis thaliana ; Alveoli ; Development ; Endosperm ; Microtubules ; Seeds
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  The process of endosperm development in Arabidopsis was studied using immunohistochemistry of tubulin/microtubules coupled with light and confocal laser scanning microscopy. Arabidopsis undergoes the nuclear type of development in which the primary endosperm nucleus resulting from double fertilization divides repeatedly without cytokinesis resulting in a syncytium lining the central cell. Development occurs as waves originating in the micropylar chamber and moving through the central chamber toward the chalazal tip. Prior to cellularization, the syncytium is organized into nuclear cytoplasmic domains (NCDs) defined by nuclear-based radial systems of microtubules. The NCDs become polarized in axes perpendicular to the central cell wall, and anticlinal walls deposited among adjacent NCDs compartmentalize the syncytium into open-ended alveoli overtopped by a crown of syncytial cytoplasm. Continued centripetal growth of the anticlinal walls is guided by adventitious phragmoplasts that form at interfaces of microtubules emanating from adjacent interphase nuclei. Polarity of the elongating alveoli is reflected in a subsequent wave of periclinal divisions that cuts off a peripheral layer of cells and displaces the alveoli centripetally into the central vacuole. This pattern of development via alveolation appears to be highly conserved; it is characteristic of nuclear endosperm development in angiosperms and is similar to ancient patterns of gametophyte development in gymnosperms.
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Sexual plant reproduction 7 (1994), S. 87-94 
    ISSN: 1432-2145
    Keywords: Evolution ; Microtubules ; Polarity Pollen ; Mitosis ; Orchids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Pollen mitosis in the slipper orchid Cypripedium fasciculatum was studied using correlated methods of immunofluorescence and transmission electron microscopy. Unlike the more highly evolved orchids, the cypripedioid orchids shed pollen as monosulcate monads. Prior to pollen mitosis, the microspore nucleus migrates to a proximal position opposite the aperture, as is typical of monocotyledons. There is no distinct generative pole microtubule system (GPMS) like that recently reported in development of pollen polarity in the vandoid moth orchid Phalaenopsis. Instead, microtubules in early prophase are concentrated around the nucleus and extend into the cytoplasm toward the future generative pole. Once the nucleus has migrated to the continuous surface opposite the aperture, microtubules surround the nucleus evenly and show no tendency to be more concentrated in the generative domain. The mitotic spindle, which develops from the perinuclear microtubules, is asymmetrically placed in the microspore and is cone-shaped. The generative pole is broad and closely appressed to the continuous spore surface, while the vegetative pole is pointed and located in the interior of the microspore. As the chromosomes move poleward, microtubules proliferate in the interzone and a phragmoplast develops. The phragmoplast expands in a hemispherical path beyond the interzone following an array of microtubules that radiates from the generative nucleus. Data from this study indicate that evolution of pollen in orchids includes a shift in location of the generative cell from proximal to distal and the evolution of a GPMS, in addition in the well-known trend toward increased pollen aggregation and loss of exine.
    Type of Medium: Electronic Resource
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  • 4
    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
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  • 5
    ISSN: 1432-2145
    Keywords: Key words Cytokinesis ; Microtubules ; Microsporogenesis ; Orchids ; Phragmoplast ; Pollen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Microsporocytes of the slipper orchid Cypripedium 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
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Journal of plant research 109 (1996), S. 301-313 
    ISSN: 1618-0860
    Keywords: Cereal ; Endosperm ; Microtubules ; Mitosis ; Morphogenesis ; Phragmoplast ; Rice
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The syncytial endosperm of rice undergoes cellularization according to a regular morphogenetic plan. At 3 days after pollination (dap) mitosis in the peripheral synctium ceases. Radial systems of microtubules emanating from interphase nuclei define nuclear-cytoplasmic domains (NCDs) which develop axes perpendicular, to the embryo sac wall. Free-growing anticlinal walls between adjacent NCDs compart-mentalize the cytoplasm into open-ended alveoli which are overtopped by syncytial cytoplasm adjacent to the central vacuole. At 4 dap, mitosis resumes as a wave originating adjacent to the vascular bundle. The spindles are oriented parallel to the alveolar walls and cell plates formed in association with interzonal phragmoplasts result in periclinal walls that cut off a peripheral layer of cells and an inner layer of alveoli displaced toward the center. Polarized growth of the newly formed alveoli and elongation of the anticlinal walls occurs during interphase. The next wave of cell division in the alveoli proceeds as the first and a second cylinder of cells is cut off inside the peripheral layer. The periods of polarized growth/anticlinal wall elongation alternating with periclinal cell division are repeated 3–4 times until the grain is filled by 5 dap.
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  • 7
    ISSN: 1615-6102
    Keywords: Actin ; Confocal microscopy ; Guard cells ; Microtubules ; Selaginella ; Stomata
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Using fluorescent probes and confocal laser scanning microscopy we have examined the organisation of the microtubule and actin components of the cytoskeleton in kidney-shaped guard cells of six species of Selaginella. The stomata of Selaginella exhibit novel cytoskeletal arrangements, and at different developmental stages, display similarities in microtubule organisation to the two major types of stomata: grass (dumbbell-shaped) and non-grass (kidney-shaped). Initially, cortical microtubules and F-actin radiate from the stomatal pore and extend across the external and internal periclinal cell surfaces of the guard cells. As the stomata differentiate, the cytoskeleton reorients only along the internal periclinal walls. Reorganisation is synchronous in guard cells of the same stoma. Microtubules on the inner periclinal walls of the guard cells now emanate from areas of the ventral wall on either side of the pore and form concentric circles around the pore. The rearrangement of F-actin is similar to that of microtubules although F-actin is less well organised. Radial arrays of both microtubules and F-actin are maintained adjacent to the external surfaces. Subsequently, in two of the six species of Selaginella examined, microtubules on both the internal and external walls become oriented longitudinally and exhibit no association with the ventral wall. In the other four species, microtubules adjacent to the internal walls revert to the initial radial alignment. These findings may have implications in the development and evolution of the stomatal complex.
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 11 (1988), S. 139-146 
    ISSN: 0886-1544
    Keywords: phragmoplast ; sporogenesis ; indirect immunofluorescence ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Studies of the microtubular cytoskeleton during sporogenesis in the hepatic Conocephalum conicum (Bryophyta) have revealed several unusual phenomena that contribute to understanding the cytokinetic apparatus in plant cell division. Although a typical phragmoplast forms in the interzonal microtubules of the first division spindle and expands to the cell periphery, no cell plate develops. There is no evidence of predetermined division sites and the orientation of both first and second meiotic spindles is imprecise. Simultaneous division of the cytoplasm follows second nuclear division. Equal apportionment of the cytoplasm appears to be a function of the establishment of cytoplasmic domains in the coenocyte, the boundaries of which are delimited by interaction of postmeiotic microtubule systems radiating from the four nuclei. Primary phragmoplasts are initiated in phragmoplasts that are initiated between nonsister nuclei. Depending upon the arrangement of nuclei in the nonpolar sporocyte, from one to three secondary phragmoplasts develop in the zones of contact between opposing sets of microtubules. Except for the site and time of initiation, the two types of phragmoplasts are identical. Eventually the phragmoplasts become confluent and cell plates form in all second division phragmoplasts. It is clear that typical functional phragmoplasts can form in sites determined by interaction of postmeiotic microtubule systems as well as in interzonal spindles as is common in plant cell division.
    Additional Material: 18 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 22 (1992), S. 72-77 
    ISSN: 0886-1544
    Keywords: bryophytes ; microtubules ; MTOC ; plastids ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Archesporial cells of the hepatic Monoclea gottschei Lindb. undergo a series of monoplastidic mitotic divisions prior to enlarging into sporocytes. Interphase cells have a nuclear-based endoplasmic microtubule system that is predominantly aligned in the long axis of the cell and lack a hoop-like cortical system. No preprophase bands (PPBs) are formed. Prior to mitosis, the single plastid divides and daughter plastids move to the incipient spindle poles as is typical of monoplastidic cell division. However, the plastids do not serve as microtubule organizing centers (MTOCs) as they do in both mitosis and meiosis of hornworts and lycopsids, and in meiosis of mosses. Rather, microtubules of the developing spindle emanate from distinct polar organizers (POs) arising just outside the nuclear envelope as in polyplastidic mitosis in other hepatics. The POs, which appear to arise de novo on opposite ends of the nucleus during preprophase, consist of vesicles, endoplasmic reticulum, and radiating microtubules. The developmental and evolutionary significance of distinct POs, plastid MTOCs, and the diffuse MTOCs of higher plants is discussed. © 1992 Wiley-Liss, Inc.
    Additional Material: 11 Tab.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 23 (1992), S. 89-101 
    ISSN: 0886-1544
    Keywords: division polarity ; F-actin ; microtubules ; plastids ; preprophase band ; stomata ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Stomatogenesis, the determinate developmental pathway leading to formation of a pair of specialized guard cells, was studied in monoplastidic cells ofSelaginella. Observations of living cells followed by immunofluorescence microscopy of the same cells made it possible to correlate changes in cytoskeletal organization with developmental events. The guard mother cell divides in a plane perpendicular to previous divisions and this shift in polarity is marked by morphogenetic plastid migration, as well as by extensive reorganization of cytoskeletal arrays. The single plastid divides and daughter plastids move to a position opposite each other (incipient spindle poles). The axis defined by the opposing plastids rotates in the cell before becoming fixed in position with polar plastids adjacent to the lateral anticlinal walls. Plastid polarity predicts spindle orientation and the plane of division. Once division polarity is defined by plastid position, which will remain unchanged throughout mitosis and cytokinesis, cortical microtubules become reorganized from radial to longitudinal (relative to the long axis of the leaf). The initially random cortical F-actin also becomes aligned longitudinally. A wide preprophase band of microtubules and F-actin is formed at right angles to the spindle axis. Plastid-based microtubules establish the preprophase spindle and also connect to the preprophase band. The mitotic spindle remains anchored at the polar plastids. After mitosis, a phragmoplast that forms among microtubules emanating from plastids and nuclei develops in the plane marked previously by the preprophase band. Mitosis is completed in 1 h 15 min ± 3 min (mean ± S.E.). © 1992 Wiley-Liss, Inc.
    Additional Material: 21 Ill.
    Type of Medium: Electronic Resource
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