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  • Cytoskeleton  (4)
  • Microtubules  (4)
  • Organelle movement  (4)
  • Megagametophyte  (2)
  • 1
    Electronic Resource
    Electronic Resource
    The kinesin-immunoreactive homologue from Nicotiana tabacum pollen tubes: Biochemical properties and subcellular localization (1993)
    Springer
    Planta 191 (1993), S. 496-506 
    Details
    ISSN: 1432-2048
    Keywords: Kinesin ; Nicotiana ; Organelle movement ; Pollen tube
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In plant cells, microtubule-based motor proteins have not been characterized to the same degree as in animal cells; therefore, it is not yet clear whether the movement of organelles and vesicles is also dependent on the microtubular cytoskeleton. In this work the kinesinimmunoreactive homologue from pollen tubes of Nicotiana tabacum L. has been purified and biochemically characterized. The protein preparation mainly contained a polypeptide with a relative molecular weight of approx. 100 kDa. This polypeptide bound to animal microtubules in an ATP-dependent manner and it further copurified with an ATPase activity fourfold-stimulated by the presence of microtubules. In addition, the sedimentation coefficient (approx. 9S) was similar to those previously shown for other kinesins. Immunofluorescence analyses revealed a partial co-distribution of the protein with microtubules in the pollen tube. These data clearly indicate that several properties of the kinesin-immunoreactive homologue are similar to those of kinesin proteins, and suggest that molecular mechanisms analogous to those of animal cells may drive the microtubule-based motility of organelles and vesicles in plants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00195751
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  • 2
    Electronic Resource
    Electronic Resource
    Ultrastructural features of Aloe ciliaris pollen (1988)
    Springer
    Sexual plant reproduction 1 (1988), S. 88-96 
    Details
    ISSN: 1432-2145
    Keywords: Pollen activation ; Generative cell ; Vegetative cell ; Cytoskeleton
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Both the internal anatomy and the external morphology of the mature pollen grain of Aloe ciliaris have been studied, together with the cytological changes occurring during pollen activation. In mature pollen, the generative cell (GC) and the vegetative nucleus (VN) are closely associated with each other, and both can be found in the central part of the grain. In the generative cytoplasm, some organelles and microtubular bundles are present. In the vegetative cell, dictyosomes, stacks of rough endoplasmic reticulum, mitochondria, plastids, vacuoles, ribosomes, and masses of fibrillar material have been described. During pollen activation, important changes occur in both the generative and vegetative cells (VC). In the GC, the microtubular bundles become clearly visible, and the GC and VC gradually move towards the germ pore. The RER cisterns become free from the stacks, and organelles, such as dictyosomes, become very active. The fibrillar masses gradually decrease in number, and the individual fibrils become more evident and clearer in resolution.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00189267
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  • 3
    Electronic Resource
    Electronic Resource
    The microtubule cytoskeleton and the rounding of isolated generative cells ofNicotiana tabacum (1992)
    Springer
    Sexual plant reproduction 5 (1992), S. 64-71 
    Details
    ISSN: 1432-2145
    Keywords: Generative cell ; Isolation ; Microtubules ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Upon squashing of the pollen grain, the isolated generative cell ofNicotiana tabacum looses its spindle shape to become spherical; this phenomenon is independent of the sucrose concentration used. The time necessary for this change can vary from 1 min (0% sucrose) to 20 min (30% sucrose). The microtubular cytoskeleton was studied by means of immunofluorescence and electron microscopy. Just after isolation, 5 to 15 clearly visible bundles in microtubules organized in a basket-like structure are present. After 15 min in medium with 15% sucrose, the microtubular cytoskeleton disappears, and a diffusely spread tubulin can be observed. Neither the addition of 10–20 μM taxol to the medium, nor the omission of Ca2+ to the medium has any effect on the changes in cell shape and loss of microtubular bundles after isolation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00714559
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  • 4
    Electronic Resource
    Electronic Resource
    Cytoplasmic motors and pollen tube growth (1996)
    Springer
    Sexual plant reproduction 9 (1996), S. 59-64 
    Details
    ISSN: 1432-2145
    Keywords: Motor proteins ; Pollen tube ; Tip growth ; Organelle movement
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The growth of pollen tubes is characterized by an intense cytoplasmic streaming, during which the movements of smaller organelles (like secretory vesicles) and larger ones (including the generative cell and vegetative nucleus) are precisely coordinated. A well-characterized cytoskeletal apparatus is likely responsible for these intracellular movements. In recent years both microfilament and microtubule-based motor proteins have been identified and assumed to be the translocators of the several organelle categories. Their precise function during pollen tube growth is not yet clear, but apparently an actomyosin-based system is mainly responsible for pollen tube elongation. On the other hand, microtubules and microtubule-based motors have been thought to play a role in the maintenance of cell polarity. Both cytoskeletal systems (and their respective motor activities) could cooperate to ensure a precise regulation of pollen tube growth.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02153052
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  • 5
    Electronic Resource
    Electronic Resource
    Pre-fertilization degeneration of both synergids in Brassica campestris ovules (1988)
    Springer
    Sexual plant reproduction 1 (1988), S. 208-216 
    Details
    ISSN: 1432-2145
    Keywords: Megagametophyte ; Synergids ; Brassica campestris ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary In Brassica campestris, both synergids of the ovule degenerate before the arrival of the pollen tube. Synergid degeneration does not depend on pollination. At the non-degenerated stage, the synergids are completely filled with a complexly organized cytoplasm containing numerous mitochondria with many cristae, a large number of dictyosomes with many associated vesicles, and a very extensive rough endoplasmic reticulum. The degenerative changes that occur in the cytoplasm of the synergids are characterized by a loss of visibility of the membranes of the endoplasmic reticulum and the simultaneous formation of dense deposits on the surrounding membranes of the mitochondria. Locally, the plasma membranes of the synergids disappear, and some ground plasma of the synergids penetrates into the space between the plasma membranes of the egg cell and the central cell.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00189154
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    Paper (German National Licenses)
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  • 6
    Electronic Resource
    Electronic Resource
    Video microscopic observations of living, isolated embryo sacs of Nicotiana and their component cells (1992)
    Springer
    Sexual plant reproduction 5 (1992), S. 156-162 
    Details
    ISSN: 1432-2145
    Keywords: Female germ unit ; Nicotiana ; Megagametophyte ; Organelle movement ; Video microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Living embryo sacs and megagametophytic cells of Nicotiana alata and Nicotiana tabacum were obtained using enzymatic maceration and microdissection. The yields of isolated embryo sacs, egg apparatus and central cells were up to 35%, 40% and 35%, respectively. Vectorial movement of organelles and undulations of tubular structures, presumably endoplasmic reticulum, were observed in eggs, synergids and central cells using video-enhanced microscopy. Despite evident viability using the fluorochromatic reaction, the egg displays much less organelle movement and therefore appears to be quiescent. The large vacuole of the central cell is traversed by mobile strands of cytoplasm through which organelles migrate. A polygonal network is located at the periphery of the central cell, which may contribute to anchorage of the cell with the embryo-sac wall. The observation of organelle movement provides direct evidence of the condition of the cell and may be a useful approach for assessing cell vigor.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00194876
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  • 7
    Electronic Resource
    Electronic Resource
    Striped projections of the outer membrane of the generative cell in Convallaria majalis pollen (1995)
    Springer
    Sexual plant reproduction 8 (1995), S. 223-227 
    Details
    ISSN: 1432-2145
    Keywords: Pollen ; Generative cell ; Cytoskeleton ; Motility ; Myosin immunogold labelling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In pollen grains of Convallaria majalis the outer membrane of the generative cell (GC) is the inner membrane of the vegetative cell (VC). Striped projections (SP) at the cytoplasmic face of the outer membrane of the GC were revealed by chemical fixation and also by a rapid freeze-fixation and freeze-substitution. The projections, located in groups on the protruding lobes of the GC, were arranged parallel to each other and were equally spaced (40 nm apart). The length of the SP, estimated from grazing sections of GC, was 400 nm. Each projection was composed of T-shaped elements, about 35 nm high, spaced at an average distance of 25 nm. SP were observed in mature, hydrated, activated and germinated pollen grains and seemed to be associated with microtubules and microfilaments of the VC. No evidence exists yet of SP on the sperm cell membrane. Immunogold labelling with anti-myosin antibodies showed many gold particles attached preferentially to the surface of the protruding lobes of the GC in the area of the projections. These results may suggest that the SP of Convallaria GC contain myosin-like protein and play an important role in the motility of the GC during pollen tube growth.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00228941
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  • 8
    Electronic Resource
    Electronic Resource
    Cytoplasmic motors and pollen tube growth (1996)
    Springer
    Sexual plant reproduction 9 (1996), S. 59-64 
    Details
    ISSN: 1432-2145
    Keywords: Key words Motor proteins ; Pollen tube ; Tip growth ; Organelle movement
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  The growth of pollen tubes is characterized by an intense cytoplasmic streaming, during which the movements of smaller organelles (like secretory vesicles) and larger ones (including the generative cell and vegetative nucleus) are precisely coordinated. A well-characterized cytoskeletal apparatus is likely responsible for these intracellular movements. In recent years both microfilament- and microtubule-based motor proteins have been identified and assumed to be the translocators of the several organelle categories. Their precise function during pollen tube growth is not yet clear, but apparently an actomyosin-based system is mainly responsible for pollen tube elongation. On the other hand, microtubules and microtubule-based motors have been thought to play a role in the maintenance of cell polarity. Both cytoskeletal systems (and their respective motor activities) could cooperate to ensure a precise regulation of pollen tube growth.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004970050011
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  • 9
    Electronic Resource
    Electronic Resource
    The organization of microtubules during generative-cell division inConvallaria majalis (1999)
    Springer
    Protoplasma 207 (1999), S. 147-153 
    Details
    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
    URL: http://dx.doi.org/10.1007/BF01282994
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  • 10
    Electronic Resource
    Electronic Resource
    Cytoskeletal changes during generative cell division and sperm formation inTradescantia virginiana (1989)
    Springer
    Protoplasma 150 (1989), S. 54-71 
    Details
    ISSN: 1615-6102
    Keywords: Generative cell ; Microtubules ; Mitosis ; Cytokinesis ; Pollen ; Sperm ; Tradescantia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Cytoskeletal organization and chromosome behavior were studied inTradescantia generative cells prior to and during sperm formation using in vitro grown pollen tubes and fluorescence staining methods. Before pollen germination, the crescent-shaped generative cell contains a reticulate microtubule (Mt) system. The cell elongates dramatically after germination, and its Mts assume a helical to longitudinal arrangement. Chromosome condensation is evident approximately 3hr after germination. Kinetochores appear as dark interruptions in the Mt array, and thus seem to attach directly to interphase fibers. No metaphase plate typical of other cells is observed with either DAPI or anti-tubulin staining. Instead, the chromosomes adopt a twisted or braided arrangement, with kinetochores distributed along the length of the cell and kinetochore fibers linked to each other and to surrounding fibers. Anaphase is characterized by a staggered, overlapping separation of chromosomes and by elongation of Mt branches connecting opposing kinetochore fibers. Cytokinesis appears to utilize a furrowing process; a phragmoplast or cell plate was never seen. As a result of these events, the sperm directly inherit their cytoskeleton from generative cell Mts involved in division. No actin fibers are observed at any stage using rhodamine-phalloidin staining. The results are discussed in terms of other reports on sperm formation, possible mitotic and cytokinetic mechanisms, and past distinctions between Mt arrays in higher plant somatic cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01352921
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