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  • Mutant (gravitropism)  (2)
  • 4,4′-Diisothiocyanatostilbene-2,2′-disulfonic acid (DIDS)  (1)
  • Ceratodon  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Amyloplasts as possible statoliths in gravitropic protonemata of the moss Ceratodon purpureus (1990)
    Springer
    Planta 181 (1990), S. 71-77 
    Details
    ISSN: 1432-2048
    Keywords: Amyloplast ; Bryophytes ; Gravitropism ; Gravity perception ; Ceratodon ; Protonema (moss), gravitropism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The kinetics of gravitropism and of amyloplast sedimentation were studied in dark-grown protonemata of the moss Ceratodon purpureus (Hedw.) Brid. The protonemata grew straight up at a rate of 20–25 μm·h− in nutrient-supplemented agar. After they were oriented to the horizontal, upward curvature was first detected after 1–1.5 h and reached 84° by 24 h. The tip cells exhibited an amyloplast zonation, with a tip cluster of nonsedimenting amyloplasts, an amyloplast-free zone, and a zone with pronounced amyloplast sedimentation. This latter zone appears specialized more for lateral than for axial sedimentation since amyloplasts sediment to the lower wall in horizontal protonemata but do not fall to the basal wall in vertical protonemata. Amyloplast sedimentation started within 15 min of gravistimulation; this is within the 12–17-min presentation time. The data support the hypothesis that some amyloplasts function as statoliths in these cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00202326
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Amyloplasts are necessary for full gravitropic sensitivity in roots of Arabidopsis thaliana (1989)
    Springer
    Planta 177 (1989), S. 198-206 
    Details
    ISSN: 1432-2048
    Keywords: Amyloplast ; Arabidopsis ; Gravitropism ; Gravity ; Mutant (gravitropism) ; Plastid and graviperception ; Starch and graviperception ; Statolith
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The observation that a starchless mutant (TC7) of Arabidopsis thaliana (L.) Heynh. is gravitropic (T. Caspar and B.G. Pickard, 1989, Planta 177, 185–197) raises questions about the hypothesis that starch and amyloplasts play a role in gravity perception. We compared the kinetics of gravitropism in this starchless mutant and the wild-type (WT). Wild-type roots are more responsive to gravity than TC7 roots as judged by several parameters: (1) Vertically grown TC7 roots were not as oriented with respect to the gravity vector as WT roots. (2) In the time course of curvature after gravistimulation, curvature in TC7 roots was delayed and reduced compared to WT roots. (3) TC7 roots curved less than WT roots following a single, short (induction) period of gravistimulation, and WT, but not TC7, roots curved in response to a 1-min period of horizontal exposure. (4) Wild-type roots curved much more than TC7 roots in response to intermittent stimulation (repeated short periods of horizontal exposure); WT roots curved in response to 10 s of stimulation or less, but TC7 roots required 2 min of stimulation to produce a curvature. The growth rates were equal for both genotypes. We conclude that WT roots are more sensitive to gravity than TC7 roots. Starch is not required for gravity perception in TC7 roots, but is necessary for full sensitivity; thus it is likely that amyloplasts function as statoliths in WT Arabidopsis roots. Furthermore, since centrifugation studies using low gravitational forces indicated that starchless plastids are relatively dense and are the most movable component in TC7 columella cells, the starchless plastids may also function as statoliths.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00392808
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  • 3
    Electronic Resource
    Electronic Resource
    Fluorescence microscopy and radiolabeling of C3 and C4 chloroplasts using diisothiocyanatostilbene disulfonic acid as a marker for the phosphate translocator (1989)
    Springer
    Planta 179 (1989), S. 137-147 
    Details
    ISSN: 1432-2048
    Keywords: Anion transport ; Chloroplast membrane (phosphate translocator) ; 4,4′-Diisothiocyanatostilbene-2,2′-disulfonic acid (DIDS) ; Fluorescence microscopy ; Spinacia (chloroplast membrane) ; Zea (chloroplast membrane)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The usefulness of 4,4′-diisothiocyanatostilbene-2,2′-disulfonic acid (DIDS) for in-situ studies of the chloroplast phosphate translocator was evaluated by fluorescence microscopy and radiolabeling of spinach (Spinacia oleracea L.) (C3 plant) and maize (Zea mays L.) (C4 plant) chloroplasts. In maize mesophyll and bundle-sheath chloroplasts and in spinach chloroplasts that were either intact, broken or swollen, DIDS fluorescence was only associated with the chloroplast envelope. Intact chloroplasts often had fluorescent patches corresponding to concave regions of the chloroplast which we assume to be regions enriched in DIDS-binding sites. Incubation of intact or broken spinach chloroplasts or maize mesophyll chloroplasts with [3H2]DIDS resulted in the labeling of a single polypeptide (relative molecular mass, Mr, ∼30 kDa) in the envelope fraction, in each case. Label in the stromal fraction was not detected when intact chloroplasts were incubated with [3H2]DIDS. However, when broken chloroplasts were incubated with [3H2]DIDS, several polypeptides of various molecular masses were labeled, but not the 30×31-kDa polypeptide. In thylakoid fractions from both broken and intact chloroplasts, a single 30×31-kDa polypeptide was labeled inconsistently. When a mixture of intact maize mesophyll and bundle-sheath chloroplasts was labeled with [3H2]DIDS, extracts of whole chloroplasts displayed radioactivity only in the 30×31-kDa band. We conclude that DIDS is a valuable probe for the in-situ identification and characterization of the ∼30-kDa protein — the presumptive phosphate translocator — in C3 and C4 chloroplasts since DIDS (1) does not penetrate the inner membrane of the envelope of intact chloroplasts and, therefore, (2) does not bind internal sites in intact chloroplasts, and (3) only binds the ∼30-kDa protein in the inner membrane of the envelope.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00393683
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  • 4
    Electronic Resource
    Electronic Resource
    Reduced gravitropic sensitivity in roots of a starch-deficient mutant ofNicotiana sylvestris (1989)
    Springer
    Planta 180 (1989), S. 123-130 
    Details
    ISSN: 1432-2048
    Keywords: Amyloplast ; Gravitropism ; Mutant (gravitropism) ; Nicotiana (gravitropism) ; Plastid and graviperception ; Starch and graviperception ; Statolith
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Gravitropism was studied in seedlings ofNicotiana sylvestris Speg. et Comes wild-type (WT) and mutant NS 458 which has a defective plastid phosphoglucomutase (EC 2.7.5.1). Starch was greatly reduced in NS 458 compared to the WT, but small amounts of starch were detected in root-cap columella cells in NS 458 by light and electron microscopy. The roots of WT are more sensitive to gravity than mutant NS 458 roots since: (1) in mutant roots, curvature was reduced and delayed in the time course of curvature; (2) curvature of mutant roots was 24–56% that of WT roots over the range of induction periods tested; (3) in intermittent-stimulation experiments, curvature of mutant roots was 37% or less than that of WT roots in all treatments tested. The perception time, roots in all treatments tested. The perception time, determined by intermittent-stimulation experiments, was ≤5 s for WT roots and 30–60 s for mutant roots. The growth rates for WT and NS 458 roots were essentially equal. These results and our previous results with WT and starchless mutantArabidopsis roots (Kiss et al. 1989, Planta177, 198–206) support the conclusions that a full complement of starch is necessary for full gravitropic sensitivity and that amyloplasts function in gravity perception. Since a presumed relatively small increase in plastid buoyant mass (N. sylvestris mutant versusArabidopsis mutant) significantly improves the orientation of theN. sylvestris mutant roots, we suggest that plastids are the likeliest candidates to be triggering gravity perception in roots of both mutants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02411418
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