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  • 1
    Electronic Resource
    Electronic Resource
    Description of somatic-embryo-forming single cells in carrot suspension cultures employing video cell tracking (1994)
    Springer
    Planta 194 (1994), S. 565-572 
    Details
    ISSN: 1432-2048
    Keywords: Cell tracking ; Daucus ; Development (single cell) ; 2,4-Dichlorophenoxyacetic acid ; Phytagel (cell immobilisation) ; Somatic embryogenesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A cell-tracking system was established to determine the capability of individual single suspension cells of carrot (Daucus carota L.) to develop into somatic embryos. When immobilised in phytagel, 127 out of 30 318 single suspension cells smaller than 22 μm in diameter developed into a somatic embryo. Single cells present at the start of the experiment were classified on the basis of their morphology into five groups: small spherical vacuolated cells; small spherical cytoplasm-rich cells; oval vacuolated cells; elongated vacuolated cells and cells that could not be classified into either one of these groups. Single cells of all morphologically distinguishable single cell types developed into somatic embryos with a frequency that varied between 19 and 100 somatic embryos per 10 000 cells. This suggests that the capability of individual single cells to form somatic embryos is not restricted to a particular cell type distinguishable on the basis of its morphology. Three major pathways were observed during development. Oval and elongated cells developed into somatic embryos via an asymmetrical cell cluster. Spherical cells developed via a symmetrical cell cluster into somatic embryos. Before formation of a somatic embryo, cells of a more variable initial morphology first developed aberrantly shaped cell clusters. This suggests that the developmental pathway leading to a somatic embryo can be predicted by the initial single-cell morphology.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00714471
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  • 2
    Electronic Resource
    Electronic Resource
    The secretory nature of the lesion of carrot cell variant ts11, rescuable by endochitinase (1997)
    Springer
    Planta 203 (1997), S. 381-389 
    Details
    ISSN: 1432-2048
    Keywords: Key words: Chitinase ; Daucus ; Plant development ; Secretion ; Somatic embryogenesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. The carrot cell variant ts11 is unable to form somatic embryos at the non-permissive temperature of 32 °C, but the block can be overcome by the addition of a 32-kDa acidic endochitinase to the medium. In this work we conducted a cyto-histological analysis of the blocked embryo forms. The morphology of the endomembrane system is altered; in particular, the ER is dilated and may show electron-dense precipitates and continuity with the plasma membrane. These morphological alterations do not occur in the presence of externally-added endochitinase. We also noticed modifications of the culture medium that are probably related to the morphological observations: the total amount of secreted proteins is reduced and pulse-chase experiments revealed that, compared with wild-type cells, the secretion of major polypeptides is reduced while new minor polypeptides are secreted. Western blot analysis revealed the presence of the binding protein BiP, a resident of the ER and of glutamine synthase, a cytosolic protein, in the medium of ts11 but not wild-type cells. These results indicate that ts11 is altered in the secretory pathway but do not clarify the role of endochitinase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004250050204
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  • 3
    Electronic Resource
    Electronic Resource
    Calcium increases the yield of somatic embryos in carrot embryogenic suspension cultures (1990)
    Springer
    Plant cell reports 9 (1990), S. 221-223 
    Details
    ISSN: 1432-203X
    Keywords: Calcium ; Daucus carota ; Somatic embryogenesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract An upward shift in the concentration of calcium present in the medium during somatic embryogenesis increased the number of embryos produced approximately two-fold. This was observed when embryogenic suspension cells grown in 2,4-D medium with the normal calcium concentration of 10−3 M were transferred to hormone-free medium containing 10−2 M calcium and when embryogenic suspension cells grown in 2,4-D medium containing 10−4 M calcium were transferred to hormone-free medium with 10−3 M calcium. At calcium concentrations between 6·10−3 and 10−2 M globular stage somatic embryos were found in cultures supplemented with 2·10−6 M of 2,4-D indicating that elevated calcium counteracts the inhibitory effect of 2,4-D on somatic embryogenesis. No qualitative changes were found in the pattern of extracellular polypeptides as a result of growth and embryogenesis in media with different calcium concentrations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00232184
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  • 4
    Electronic Resource
    Electronic Resource
    Expression of the JIM8 cell wall epitope in carrot somatic embryogenesis (1996)
    Springer
    Planta 200 (1996), S. 167-173 
    Details
    ISSN: 1432-2048
    Keywords: Arabinogalactan protein epitope ; Cell tracking ; Daucus ; Monoclonal antibody (JIM8) ; Somatic embryogenesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Certain single cells in carrot (Daucus carota L.) suspension cultures react with the monoclonal antibody JIM8, and it has been proposed that these cells represent a transitional stage in somatic embryo formation. Shortly after isolation of the single cells by sieving, up to 80% of the cells react with JIM8. Within 4 d, JIM8 labelling becomes restricted to 1% of the single cells. To obtain evidence for the proposed correlation between expression of the JIM8 cell wall epitope and somatic embryo formation the developmental fate of carrot single cells labelled with JIM8 was determined by cell tracking. The results, obtained by recording 43 000 cells, show that only few JIM8-labelled cells give rise to embryos, and most somatic embryos develop from cells devoid of the JIM8 cell wall epitope. We therefore conclude that the presence of the JIM8 cell wall epitope does not coincide with the ability of single suspension cells to form embryos.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00208305
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  • 5
    Electronic Resource
    Electronic Resource
    Gene-expression programs in embryogenic and non-embryogenic carrot cultures (1988)
    Springer
    Planta 176 (1988), S. 205-211 
    Details
    ISSN: 1432-2048
    Keywords: Daucus ; Embryogenic potential ; Gene expression ; mRNA ; Somatic embryogenesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Somatic embryogenesis can be synchronized by enriching carrot (Daucus carota L.) suspension cultures for small, dense clusters of cells termed proembryogenic masses (PEMs). Gene-expression programs of PEMs were compared with those of embryonic and mature tissues by in-vitro translation of representative mRNA populations and by nucleic-acid hybridization. Analysis of invitro-translated polypeptides by two-dimensional polyacrylamide gel electrophoresis revealed striking similarities between the mRNA populations of PEM and torpedo-stage embryos; substantial differences, however, were observed when in-vitro translation products of PEMs and torpedo embryos were compared with those of hypocotyls and leaves. Northern blots of RNA isolated from PEMs, staged embryos, and mature carrot tissues were hybridized with cDNA probes for Dc3, Dc5 and Dc13; these cDNA recombinants represent mRNAs that are regulated during carrot somatic embryogenesis. The pattern of expression of these embryo-regulated transcripts was similar in PEMs and somatic embryos but differed in other carrot tissues. These results indicate that many of the molecular processes of embryogenesis are already established in PEMs in the presence of auxin. Additional experiments indicate the utility of Dc3 as a molecular marker for the acquisition of embryogenic potential.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00392446
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  • 6
    Electronic Resource
    Electronic Resource
    Transient reduction in secreted 32 kD chitinase prevents somatic embryogenesis in the carrot (Daucus carota L.) variant ts11 (1995)
    Chichester [u.a.] : Wiley-Blackwell
    Developmental Genetics 16 (1995), S. 332-343 
    Details
    ISSN: 0192-253X
    Keywords: Somatic embryogenesis ; temperature-sensitive mutant ts11 ; chitinase ; carrot (Daucus carota L.) ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: At the nonpermissive temperature, somatic embryos of the temperature-sensitive (ts) carrot (Daucus carota L.) cell variant ts11 only proceed beyond the globular embryo stage in the presence of medium conditioned by wild-type cells. The causative component in the conditioned medium has been identified as an acidic 32 kD endochitinase. An antiserum raised against the 32 kD chitinase detected this protein in culture medium from ts11 embryo cultures grown at the permissive temperature as well as at the nonpermissive temperature. No difference in biochemical characteristics or in effect on ts11 embryo development could be detected between the 32 kD chitinase purified from wild-type cultures and the chitinase from ts11 cultures grown at the permissive or at the nonpermissive temperature. Compared to the amount present in a ts11 embryo culture at the permissive temperature, a reduction in the amount of 32 kD chitinase was observed during the temperature-sensitive period at the nonpermissive temperature. These results imply that the arrested embryo phenotype of ts11 is not the result of a structural difference in its 32 kD chitinase, but is the result of a transient decrease in the amount of 32 kD chitinase present. Morphological observations indicate that the ts11 phenotype is pleiotropic and also affects the cell wall of nonembryogenic cells. © 1995 Wiley-Liss, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/dvg.1020160406
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