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  • Electronic Resource  (5)
  • 1995-1999  (5)
  • Betula pendula  (1)
  • Caffeine  (1)
  • Cell division  (1)
  • Embryo sac  (1)
  • Nicotiana tabacum
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  • Electronic Resource  (5)
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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Sexual plant reproduction 12 (1999), S. 67-70 
    ISSN: 1432-2145
    Keywords: Key words Cytoskeleton ; Cytoskeleton proteins ; Cytoskeleton function ; Pollen tube ; Embryo sac
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Sexual reproduction in plants is intimately connected to the activity of the cytoskeletal apparatus in reproductive cells. Because of the ease with which the pollen tube can be studied, it has become a model for studying many aspects of cell physiology related to the cytoskeleton, such as movement of organelles and vesicles and cell division. However, information about cytoskeletal proteins is still insufficient for determining cytoskeletal functions during reproduction, especially in terms of cell-cell interactions. One reason may be that cytological and biochemical research on the cytoskeleton of pollen and the embryo sac has not been complemented by sufficient research activity at genetic and molecular levels, and few laboratories are currently involved in this work. This might be because of problems in identifying appropriate applied applications of the work that might attract more investigation.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1615-6102
    Keywords: Cell division ; Confocal microscopy ; Convallaria majalis ; Generative cell ; Liliaceae ; Microtubules
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The organization of the microtubule cytoskeleton in the generative cell ofConvallaria majalis has been studied during migration of the cell through the pollen tube and its division into the two sperm cells. Analysis by conventional or confocal laser scanning microscopy after tubulin staining was used to investigate changes of the microtubule cytoskeleton during generative-cell migration and division in the pollen tube. Staining of DNA with 4′,6-diamidino-2-phenylindole was used to correlate the rearrangement of microtubules with nuclear division during sperm cell formation. Before pollen germination the generative cell is spindle-shaped, with microtubules organized in bundles and distributed in the cell cortex to form a basketlike structure beneath the generative-cell plasma membrane. During generative-cell migration through the pollen tube, the organization of the microtubule bundles changes following nuclear division. A typical metaphase plate is not usually formed. The generative-cell division is characterized by the extension of microtubules concomitant with a significant cell elongation. After karyokinesis, microtubule bundles reorganize to form a phragmoplast between the two sperm nuclei. The microtubule organization during generative-cell division inConvallaria majalis shows some similarities but also differences to that in other members of the Liliaceae.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1615-6102
    Keywords: Caffeine ; Freeze substitution ; Lilium ; Pollen tubes ; Rapid freeze fixation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary In an attempt to correlate structural effects with the known dissipation of the tip-focused Ca2+ gradient caused by caffeine, we have examined the ultrastructure of caffeine-treated lily pollen tubes prepared by rapid freeze fixation and freeze substitution. We show that treatment with caffeine results in a rapid rearrangement of secretory vesicles at the pollen tube tip; the normal cone-shaped array of vesicles is rapidly dispersed. In addition, microfilament bundles appear in the tip region, where they had previously been excluded. Delocalized vesicle fusion continues in the presence of caffeine but tube extension ceases. Removal of caffeine from the growth medium initially causes tip swelling, delocalized vesicle fusion and presence of microfilaments well into the tip before normal structure and growth resume, concurrent with the previously reported return to a normal Ca2+ gradient.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1615-6102
    Keywords: Microtubule ; Microtubule organizing centers ; Nicotiana tabacum ; Pericentriolar antigens ; Plasma membrane ; Pollen tube
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary In the pollen and pollen tube of higher plants, the distribution of the microtubular cytoskeleton has been extensively studied. Even though the pattern of microtubules is known, one of the most remarkable deficiencies is the absence of data on the localization of microtubule-nucleation sites in the pollen tubes. In order to get insights about the localization of centrosome-like structures in the pollen tube ofNicotiana tabacum L., we have used the monoclonal antibody 6C6 to search for pericentriolar antigen(s). The antibody was initially raised against a component of animal centrosomes and has been already employed to locate centrosomal structures in other plant cell types. By immunoblotting analysis, a polypeptide of Mr 77,000 was identified specifically in the membrane-associated protein fraction of the pollen tube, and is absent from the soluble protein pool. Immunofluorescence observations have shown the polypeptide to be located in the apical part of the pollen tube (about 40–50 μm from the tip) in association with the cortical area. A purified plasma membrane fraction from the growing pollen tubes has been obtained, using H+-ATPase activity as an organelle marker. The plasma membrane fraction was shown to be enriched in the Mr 77,000 polypeptide, which can be extracted from membranes by treatment with the detergent CHAPS at a concentration of 0.5%. These data open new research perspectives on the localization and analysis of putative cortical microtubule nucleation sites in the pollen tube.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1615-6102
    Keywords: Allergens ; Allergy ; Betula pendula ; Immunolabelling ; Pollen grains ; Tapetum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Although intact pollen grains are assumed to be the primary carrier of pollen allergens, specific immunoreactive components have been found in other aerosol fractions, e.g., starch grains and remains of tapetal cells Cryo-scanning-electron-microscopy results demonstrate the presence of a clear network of strands connecting the tapetum with the microspores. The distribution of protein in tapetal orbicules, pollen wall, and pollen cytoplasm was tested by histochemical stains for light microscopy and transmission electron microscopy. The protein is mainly localized at the apertures and starch grains in the cytoplasm of pollen and in the core and on the surface of tapetal orbicules. Monoclonal antibodies Bv-10, BIP3, and BIP4 have been used to locate the cellular sites of pollen and tapetal allergens inBetula pendula (syn.B. verrucosa). The application of rapid-freeze fixation prevented relocation of allergens from their native sites. The allergens are predominantly found in the starch grains and to lesser extent in the exine. We also tested interactions between mature birch pollen and human fluids: saliva, nostrils fluid, and eyes solution. The aim was to mimic more closely the in vivo situation during allergenic response. In all cases we observed several pollen grains that were burst and had released their cytoplasmic contents. In the nose the allergens are released from the pollen within minutes. In rhinitis, nasal pH is increased from the normal pH 6.0 to 8.0. When we used nasal fluid at pH 8.0, the number of ruptured pollen grains increased. The mechanism that might induce formation of small allergen-bearing particles from living plant cells is discussed.
    Type of Medium: Electronic Resource
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