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  • 1
    Electronic Resource
    Electronic Resource
    ANISOTROPIC EXPANSION OF THE PLANT CELL WALL (2005)
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Cell and Developmental Biology 21 (2005), S. 203-222 
    Details
    ISSN: 1081-0706
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology , Medicine
    Notes: Plants shape their organs with a precision demanded by optimal function; organ shaping requires control over cell wall expansion anisotropy. Focusing on multicellular organs, I survey the occurrence of expansion anisotropy and discuss its causes and proposed controls. Expansion anisotropy of a unit area of cell wall is characterized by the direction and degree of anisotropy. The direction of maximal expansion rate is usually regulated by the direction of net alignment among cellulose microfibrils, which overcomes the prevailing stress anisotropy. In some stems, the directionality of expansion of epidermal cells is controlled by that of the inner tissue. The degree of anisotropy can vary widely as a function of position and of treatment. The degree of anisotropy is probably controlled by factors in addition to the direction of microfibril alignment. I hypothesize that rates of expansion in maximal and minimal directions are regulated by distinct molecular mechanisms that regulate interactions between matrix and microfibrils.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1146/annurev.cellbio.20.082503.103053
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  • 2
    Electronic Resource
    Electronic Resource
    Improvements in immunostaining samples embedded in methacrylate: localization of microtubules and other antigens throughout developing organs in plants of diverse taxa (1992)
    Springer
    Planta 187 (1992), S. 405-413 
    Details
    ISSN: 1432-2048
    Keywords: Cytoskeleton ; Dithiothreitol ; Fluorescencemicroscopy ; Immuno cytochemistry ; Microtubules(techniques)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Microtubules are important in plant growth and development. Localizing microtubules in sectioned material is advantageous because it allows any tissue of interest to be studied and it permits the positional relations of the cells within the organ to be known. We describe here a method that uses semi-thin (0.5–2 μm) sections of material embedded in butyl-methylmethacrylate, to which 10 mM dithiothreitol was added. After removing the embedding material and using indirect immunofluorescence staining, we obtain clear images of microtubules, actin microfilaments, callose and pulse-fed bromodeoxyuridine. This method works on the root tissues of Arabidopsis thaliana(L.) Heynh, Pinus radiataD. Don, Zamia furfuraceaAit., Azolla pinnataR. Br. and on sporophytic tissues of Funaria hygrometricaHedw. In general, most of the cells in the organs studied are successfully stained. Using this method, we find that interphase meristematic cells in all of these species have microtubules not only in the usual cortical array but also throughout their cytoplasm. The presence of the calcium chelator ethylene glycol-bis(β-aminoethyl ether)N,N,N′,N′-tetraacetic acid EGTA in fixation buffers led to some tissue damage, and did not enhance the preservation of microtubules. The common assumption that EGTA-containing buffers stabilize plant microtubules during fixation appears unwarranted.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00195665
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  • 3
    Electronic Resource
    Electronic Resource
    Stimulation of radial expansion in arabidopsis roots by inhibitors of actomyosin and vesicle secretion but not by various inhibitors of metabolism (1995)
    Springer
    Planta 197 (1995), S. 514-521 
    Details
    ISSN: 1432-2048
    Keywords: Actomyosin ; Arabidopsis (root expansion) ; Growth anisotropy ; Inhibitor ; Root morphology ; Vesicle secretion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Plant morphogenesis depends on accurate control over growth anisotropy. To learn to what extent the control of growth anisotropy depends on cellular metaolism, we surveyed the response of growing roots to a range of inhibitors. Seedlings of Arabidopsis thaliana L. (Heynh), 7–8 d old, were transplanted onto plates containing an inhibitor, and elongation and radial expansion of roots were measured over the subsequent 2-d period. Fourteen inhibitors of diverse metabolic processes inhibited root elongation but failed to stimulate radial expansion. These inhibitors were aluminum sulfate, aphidicolin (DNA synthesis), caffeine (cell-plate formation), cisplatin (DNA synthesis), cycloheximide (protein synthesis), 3,4-dehydro-l-proline (proline hydroxylation), 6-dimethylaminopurine (protein kinases), dinitrophenol (mitochondrial ATP synthesis), galactose (UDP-glucose formation), Lovastatin, formerly mevinolin (isoprenoid formation), methionine sulfoximine (glutamine synthetase), methotrexate (folate metabolism), XRD-489 (synthesis of branched-chain amino acids), and high or low calcium treatments. These results show that various types of metabolic disruption, although inhibitory to elongation, do not reduce the high degree of anisotropic growth of the root. However, five chemicals did stimulate radial expansion; namely, the detergent, digitonin; two inhibitors of vesicle secretion, monensin and brefeldin A; and two inhibitors of actomyosin, cytochalasin B and butanedione monoxime. The maximum radial expansion induced by these compounds (except butanedione monoxime) was greater than that caused by ethylene, and the morphology of treated roots did not resemble that of roots treated with ethylene. These results indicate that vesicle secretion and actomyosin play a role in controlling anisotropic expansion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00196673
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  • 4
    Electronic Resource
    Electronic Resource
    Auxin stimulates both deposition and breakdown of material in the pea outer epidermal cell wall, as measured interferometrically (1991)
    Springer
    Planta 185 (1991), S. 462-471 
    Details
    ISSN: 1432-2048
    Keywords: Auxin and elongation growth ; Epidermis ; Interference microscopy ; Cell wall growth ; Pisum (auxin and cell-wall growth)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The effect of auxin on the mass per area in the outer epidermal walls of third internodes of Pisum sativum L. cv. Alaska grown in dim red light was investigated using interference microscopy, and rates of net deposition of wall material were calculated. Examination of these net rates under different growth conditions showed that there is no simple relationship between the deposition of mass and growth. Net deposition can be proportional to growth when sufficient substrate for wall synthesis is available, as in intact plants, and in segments treated with indole-3-acetic acid (IAA) plus glucose. Net deposition can cause thickening of the walls when growth is small, as in the case of segments kept without IAA in the presence or absence of glucose, or segments whose growth is inhibited with mannitol. When substrate is limited and growth is large, however, wall expansion can occur with no net deposition, or an actual net loss of wall material can even take place. Auxin appears to induce a breakdown in the walls of segments treated in the absence of glucose, although it promotes synthesis when glucose is present. It is likely that IAA always induces a breakdown of wall material, but that the breakdown is masked when substrate is available for synthesis. Our results indicate that pea epidermal cells have two different auxin-stimulated mechanisms, wall synthesis and wall breakdown, potentially available to loosen their outer epidermal walls to bring about cell enlargement, alternatives which could be employed to different extents depending on substrate conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00202954
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  • 5
    Electronic Resource
    Electronic Resource
    Hazards of the passive voice (1996)
    [s.l.] : Nature Publishing Group
    Nature 381 (1996), S. 730-730 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] SIR - Leather correctly points out that the active voice can impart a personal agency where none were better shown. But so too the passive voice can hide an agent inappropriately, as in the ever-so-blameless "mistakes were made". Active and passive voices differ not only in whether they name the ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/381730c0
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  • 6
    Electronic Resource
    Electronic Resource
    The Arabidopsis thaliana PPX/PP4 phosphatases: molecular cloning and structural organization of the genes and immunolocalization of the proteins to plastids (2000)
    Springer
    Plant molecular biology 44 (2000), S. 499-511 
    Details
    ISSN: 1573-5028
    Keywords: gene comparison ; PPX-1 ; PPX-2 ; protein phosphatase ; root plastid ; subcellular localization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The PPX/PP4 Ser/Thr protein phosphatases belong to the type 2A phosphatase subfamily and are present in most eukaryotic organisms. We have previously isolated two closely related DNAs encoding PPX isoforms (PPX-1 and PPX-2) of Arabidopsis thaliana. Here we report the molecular cloning of the genes encoding these proteins. The genes PPX-1 and PPX-2 are composed of eight exons and seven introns located at equivalent positions related to the coding sequences. Whereas the intron-exon organization of the PPX genes is completely different from that of the PP2A-3/PP2A-4 A. thaliana family, specific intron-exon boundaries are conserved among PPX genes from distantly related organisms. Based on GUS expression, both PPX genes show the same spatial and temporal pattern of expression: they are expressed in all the organs and tissues analyzed, and from the earliest stage of development. When PPX proteins were localized to the root in semi-thin methacrylate sections by immunofluorescence, staining was predominantly confined to small organelles, shown to be plastids by co-localization of PPX and ferredoxin. Interestingly, only some ferredoxin-positive plastids were also PPX-positive, and PPX staining was consistently brighter in the epidermis. The localization was confirmed with immunogold and electron microscopy. Our results suggest that, despite its strong sequence conservation, PPX in plants functions differently than in animals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1026587405656
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  • 7
    Electronic Resource
    Electronic Resource
    Direct observation of mitotic spindle elongation in vitro (1988)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 10 (1988), S. 210-216 
    Details
    ISSN: 0886-1544
    Keywords: anaphase-B ; diatom spindle ; microtubule sliding ; mitosis in vitro ; video microscopy ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Successful reactivation in vitro of anaphase B has recently been achieved with mitotic spindles isolated from the diatom Stephanopyxis turris. When a population of isolated spindles was studied indirectly by using immunofluorescence, nearly all of them were found to have elongated; however, when studied directly by using video microscopy, only a small proportion of spindles elongated. We report here conditions that allow nearly all of the spindles to elongate when observed directly with video microscopy. These direct observations validate previous ones made using indirect immunofluorescence. In addition, we find that the isolated spindles elongate with a linear rate, that the elongation is unchanged after the chromatin surrounding the spindles is digested with DNase I, and that during elongation a phase-dense matrix may accumulate in the spindle midzone.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cm.970100125
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  • 8
    Electronic Resource
    Electronic Resource
    On the constancy of cell division rate in the root meristem (2000)
    Springer
    Plant molecular biology 43 (2000), S. 545-554 
    Details
    ISSN: 1573-5028
    Keywords: cell cycle duration ; cell division rate ; cell length ; kinematic analysis ; root meristem
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract This review examines under what circumstances the rate of cell division among cells of the root meristem is known to vary. First, methods are compared that have been used to quantify cell division rate. These can be grouped as being either cytological, in which the rate of accumulation of cells in a particular phase of the cell cycle is determined based on some form of cytological labeling, or kinematic, in which the rate of cell accumulation is determined from the net movement of cells. Then, evidence is reviewed as to whether cell division rates vary between different tissues or cell types, between different positions in the root, or finally between different environments. The evidence is consistent with cells dividing at a constant rate, and well documented examples where cell division rate changes substantially are rare. The constancy of cell division rate contrasts with the number of dividing cells, which varies extensively, and implies that a major point for cell cycle control is governing the exit from the proliferative state at the basal boundary of the meristem.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006383921517
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