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  • 1
    Electronic Resource
    Electronic Resource
    Short-term boron deprivation enhances levels of cytoskeletal proteins in maize, but not zucchini, root apices (2003)
    Oxford, UK : Munksgaard International Publishers
    Physiologia plantarum 117 (2003), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: By using indirect immunofluorescence microscopy and Western blot analysis, we have demonstrated increased levels of actin and tubulin proteins as well as an altered polymerization pattern of their cytoskeletal assemblies in maize, but not zucchini root apices, as a response to early boron deprivation. Northern blot analysis, however, did not show significant increases in the amount of steady-state mRNAs of actin and tubulin. This finding indicates that these rapid cytoskeletal responses to boron removal are very likely regulated at translational/post-translational levels. Interestingly, these increased levels of cytoskeletal proteins coincided well with a reduction in the water-extractable, but not with the cell wall-bound, fraction of boron. This implicates that free boric acid, or other more labile boron complexes, might be involved in the activation of cytoskeletal responses in maize root apices. In fact, our experimental approach revealed that maize was suffering from boron deprivation as early as zucchini. This was evidenced by its slightly reduced root elongation rate recorded within 3–5 h of boron deprivation. Importantly, however, maize roots can recover from this early inhibition indicating an effective adaptation mechanism. In contrast, zucchini roots apparently lack this boron-deprivation response pathway and suffer extensively when exposed to boron-free environment. This leads to the tentative working hypothesis for an adaptive mechanism of maize roots to boron deprivation by enhancing its cytoskeletal protein levels and altering their polymerization patterns in order to mechanically reinforce the cell periphery complex of their cells. This testable hypothesis requires further experimental verification.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1034/j.1399-3054.2003.00029.x
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  • 2
    Electronic Resource
    Electronic Resource
    Tubular reassembly of the plastid envelope in mechanically stressed cells of a siphonous green alga (Chlorodesmis fastigiata C.Ag. Ducker, Udoteaceae) (1983)
    Springer
    Planta 157 (1983), S. 190-192 
    Details
    ISSN: 1432-2048
    Keywords: Chlorodesmis Chlorophyta ; Injury ; Plastid envelope ; Plastid tubule
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A dramatic tubular reorganization of the plastid envelope in injury-stressed cytoplasm of the siphonous green alga Chlorodesmis fastigiata is described and discussed as a process of membrane self-assembly under drastic changes in the microenvironment of the organelle.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00393654
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  • 3
    Electronic Resource
    Electronic Resource
    Redistribution of actin, profilin and phosphatidylinositol-4,5-bisphosphate in growing and maturing root hairs (1999)
    Springer
    Planta 209 (1999), S. 435-443 
    Details
    ISSN: 1432-2048
    Keywords: Key words: Actin ; Cytochalasin D ; Mastoparan ; Phosphatidylinositol-4 ; 5-bisphosphate ; Profilin ; Tip growth
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. The continuously changing polar cytoplasmic organization during initiation and tip growth of root hairs is reflected by a dynamic redistribution of cytoskeletal elements. The small G-actin binding protein, profilin, which is known to be a widely expressed, potent regulator of actin dynamics, was specifically localized at the tip of root hairs and co-distributed with a diffusely fluorescing apical cap of actin, but not with subapical actin microfilament (MF) bundles. Profilin and actin caps were present exclusively in the bulge of outgrowing root hairs and at the apex of elongating root hairs; both disappeared when tip growth terminated, indicating a tip-growth mechanism that involves profilin-actin interactions for the delivery and localized exocytosis of secretory vesicles. Phosphatidylinositol-4,5-bisphosphate (PIP2), a ligand of profilin, was localized almost exclusively in the bulge and, subsequently, formed a weak tip-to-base gradient in the elongating root hairs. When tip growth was eliminated by the MF-disrupting inhibitor cytochalasin D, the apical profilin and the actin fluorescence were lost. Mastoparan, which is known to affect the PIP2 cycle, probably by stimulating phospholipases, caused the formation of a meshwork of distinct actin MFs replacing the diffuse apical actin cap and, concomittantly, tip growth stopped. This suggests that mastoparan interferes with the PIP2-regulated profilin-actin interactions and hence disturbs conditions indispensable for the maintenance of tip growth in root hairs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004250050746
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  • 4
    Electronic Resource
    Electronic Resource
    Molecular weight and quaternary structure of ribulose bisphosphate carboxylase from the cyanobacterium, Synechococcus sp. (1981)
    Springer
    Archives of microbiology 130 (1981), S. 344-348 
    Details
    ISSN: 1432-072X
    Keywords: Ribulose bisphosphate carboxylase ; Quaternary structure ; Molecular weight ; Electron microscopy ; Cyanobacteria ; Synechococcus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Ribulose bisphosphate (RuP2) carboxylase from the marme cyanobacterium, Synechococcus sp., comprised both large (57,000 dalton) and small (12,000 dalton) subunits. The undissociated, purified enzyme was considerably smaller than the spinach enzyme when compared by pore-gradient electrophoresis, gel filtration and density-gradient centrifugation. This suggested that the cyanobacterial enzyme might have a hexameric (L6S6) subunit structure, unlike the enzymes from spinach and many other organisms which are octamers (L8S8). However, the molecular weight of the Synechococcus enzyme was measured by equilibrium sedimentation and found to be 530,000, which is within the range observed for L8S8-type enzymes. Furthermore, electron microscopic studies of negatively stained preparations of both the native enzyme, and a preparation depleted of 87% of its small subunits by repeated mild-acid precipitation, revealed four-fold symmetry characteristic of an octameric, cubical structure. Synechococcus RuP2 carboxylase therefore must be an L8S8 octamer and its anomalous pore-penetration behaviour may be due to an asymmetric shape. Some support for the latter possibility was provided by electron miscoscopic observations of two different types of images which may be different views of the molecule in two planes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00414597
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  • 5
    Electronic Resource
    Electronic Resource
    Actin in living and fixed characean internodal cells: identification of a cortical array of fine actin strands and chloroplast actin rings (1996)
    Springer
    Protoplasma 190 (1996), S. 25-38 
    Details
    ISSN: 1615-6102
    Keywords: Chara ; F-actin ; Immunofluorescence ; Microtubule ; Nitella ; Phalloidin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We report on the novel features of the actin cytoskeleton and its development in characean internodal cells. Images obtained by confocal laser scanning microscopy after microinjection of living cells with fluorescent derivatives of F-actin-specific phallotoxins, and by modified immunofluorescence methods using fixed cells, were mutually confirmatory at all stages of internodal cell growth. The microinjection method allowed capture of 3-dimensional images of high quality even though photobleaching and apparent loss of the probes through degradation and uptake into the vacuole made it difficult to record phallotoxin-labelled actin over long periods of time. When injected at appropriate concentrations, phallotoxins affected neither the rate of cytoplasmic streaming nor the long-term viability of cells. Recently formed internodal cells have relatively disorganized actin bundles that become oriented in the subcortical cytoplasm approximately parallel to the newly established long axis and traverse the cell through transvacuolar strands. In older cells with central vacuoles not traversed by cytoplasmic strands, subcortical bundles are organized in parallel groups that associate closely with stationary chloroplasts, now in files. The parallel arrangement and continuity of actin bundles is maintained where they pass round nodal regions of the cell, even in the absence of chloroplast files. This study reports on two novel structural features of the characean internodal actin cytoskeleton: a distinct array of actin strands near the plasma membrane that is oriented transversely during cell growth and rings of actin around the chloroplasts bordering the neutral line, the zone that separates opposing flows of endoplasm.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01281192
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  • 6
    Electronic Resource
    Electronic Resource
    Improved visualization of F-actin in the green algaAcetabularia by microwave-accelerated fixation and simultaneous FITC-Phalloidin staining (1996)
    Springer
    Journal of molecular histology 28 (1996), S. 353-360 
    Details
    ISSN: 1573-6865
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary By employing a new procedure we have been able to visualize a highly intense actin cytoskeleton in the unicellular green algaAcetabularia acetabulum Silva. The protocol described in this study involves microwave-accelerated simultaneous permeabilization with 10% dimethyl sulphoxide, fixation with 1% glutaraldehyde and incubation with 0.5 μM fluorescein-isothiocyanateconjugated Phalloidin. Comparison of the images of the actin cytoskeleton of the stalk, as visualized by methods used previously, with those obtained in our own experiments shows that the actin filaments were preserved completely in an excellent condition. The required time for each procedure could be reduced from 12 h for the most commonly used immunofluorescence technique to 35 min. Moreover, it has been possible to observe the actin filament system of hair whorls, rhizoid and tip. Previously, the actin cytoskeleton of these parts of the cell could not be visualized by conventional techniques. It is shown that each region of the cell-stalk, tip, rhizoid and sidebranches-displays characteristic degrees of actin bundling and regularity of actin alignment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02331398
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  • 7
    Electronic Resource
    Electronic Resource
    Cytoskeletal architecture and motility in a giant freshwater amoeba, Reticulomyxa (1986)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 6 (1986), S. 521-533 
    Details
    ISSN: 0886-1544
    Keywords: intracellular organelle transport ; microtubules ; microfilaments ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Reticulomyxa is a large, multinucleated freshwater protozoan with striking intracellular transport. Cyloplasmic streaming and saltatory movements of individual organelles (at rates of up to 25 μm/sec) are observed within the naked cell body and the extensive reticulate peripheral network of fine cytoplasmic strands. As demonstrated by video-enhanced light microscopy, individual organelles move only when associated with cytoskeletal linear elements. The linear elements are composed of mixed colinear bundles of microtubules and actin filaments, which form the backbone of the reticulopodial network. The constant branching, sprouting, and fusion of network stands suggest unique membrane properties and an unusually dynamic cytoskeleton. The electrophoretic mobility of Reticulomyxa tubulins and the lack of crossreactivity with several antibodies known to react with many plant and animal tubulins suggest that they may differ from other tubulins more widely than might be expected. Reticulomyxa's large size, the rapidity and pervasiveness of the two forms of transport, and the simple and ordered cytoskeleton make the organism well suited for future studies on the mechanisms of intracellular transport.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cm.970060511
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  • 8
    Electronic Resource
    Electronic Resource
    Muskelproteine in Pflanzenzellen (1997)
    Weinheim : Wiley-Blackwell
    Biologie in unserer Zeit 27 (1997), S. 195-203 
    Details
    ISSN: 0045-205X
    Keywords: Life and Medical Sciences
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Pflanzen können nicht weglaufen. Ihre Zellen sind in der Regel von einer Zellwand umgeben und durch den vakuolären Turgordruck prall gespannt. Dadurch wird ihr Gewebe starrer als das der tierischen Organismen. Pflanzen sind deshalb im Laufe der Evolution Meister im „Aussitzen“ geworden. Allen Belastungen durch ihre Umwelt miissen sie an Ort und Stelle durch Anpassung begegnen.Wozu sollten sie also Proteine besitzen, die denen in tierischen Muskelzellen ähnlich sind? Die Antwort ist ganz einfach: Nicht die Zellen selbst bewegen sich, sondern in den Zellen herrscht rege Betriebsamkeit. Nicht nur die Chromosomen, sondern auch die Zellorganellen werden in Vorbereitung auf die Zellteilung an vorbestimmte Orte in der Zelle rangiert, damit jede Tochterzelle einen ihrer zukünftigen Aufgabe entsprechenden Anteil davon erhält. Aber auch außerhalb der Teilungsphasen werden, je nach Zelltyp in unterschiedlichem Umfang, Organellen oder sogar das gesamte Zytoplasma von einem Ende zum anderen transportiert oder regelrecht in Rotation versetzt, um alle Zellbereiche mit Nachschub zu versorgen. Insbesondere die Organellen der Photosynthese, die Chloroplasten, können gezielt verlagert werden, um je nach Intensität und Einfallswinkel des Lichtes die Photosyntheseleistung zu optimieren.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/biuz.960270308
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