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  • 1
    Electronic Resource
    Electronic Resource
    Ploidy reduction and genome segregation in cultured carrot cell lines. II. Somatic meiosis (1992)
    Springer
    Plant cell, tissue and organ culture 30 (1992), S. 115-119 
    Details
    ISSN: 1573-5044
    Keywords: cell suspension cultures ; Daucus carota ; haploidy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Carrot cell lines W1 and W2 express permanently in culture a meiotic-like phenotpe, with apparent pairing and chiasmata formation comparable to meiosis during carrot microsporogenesis. The variant lines also show several variants of division in relation to the presence or absence of cytokinesis, nuclear fusion or spindle disturbance. The meiotic-like divisions can also be found in the abnormal structures, which are regenerated from these spontaneous variant lines. A possible role of the chromosome reducing mechanisms on carrot embryogenesis capacity and somaclonal variability is postulated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00034304
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  • 2
    Electronic Resource
    Electronic Resource
    Ploidy reduction and genome segregation in cultured carrot cell lines. I. Prophase chromosome reduction (1992)
    Springer
    Plant cell, tissue and organ culture 30 (1992), S. 107-114 
    Details
    ISSN: 1573-5044
    Keywords: chromosome variability ; Daueus earota ; polyploidy ; somatic enbryogenesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Cytological analysis of different carrot cell lines in culture has shown various cytogenetic anomalies generating new levels of ploidy and novel chromosome numbers. Polyploidy may be considered a reservoir of variability that can be released in the form of distinct new segregants of different ploidy. Mechanisms alternative to mitosis (reductional grouping, prophase chromosome reduction) operate from a polyploid state (possibly reached by means of endopolyploidy, endomitosis, nuclear fusion, or restitution nuclei) to generate new levels of ploidy and novel chromosome numbers necessary for selection to operate in vitro. The segregational phenomena require chromosome recognition in haploid set complements and abnormal behaviour of mitoses; the resulting chromosome variability suggests that chromosomes are arranged, in the resting nuclei, in an orderly and predictable manner. The knowledge of the molecular events governing these mechanisms, and how to control them, would be of great help for future applications of plant cell culture.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00034303
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    DNA heterogeneity and genetic control of tumorigenesis in nicotiana tumorous and nontumorous genotypes (1982)
    Chichester [u.a.] : Wiley-Blackwell
    Developmental Genetics 3 (1982), S. 25-39 
    Details
    ISSN: 0192-253X
    Keywords: tumorous and nontumorous genotypes ; DNA amplification ; repetitive DNA ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: The possible relevance of changes in amounts of highly repetitive DNA sequences for plant differentiation and dedifferentiation processes has been suggested in several cases. Data are lacking however on (1) the genetic control of these phenomena and (2) cause-effect relationships between DNA amplification and specific ontogenetic patterns.The present study was carried out on a Nicotiana genetic system consisting of the tumorous amphidiploid N glauca X N langsdorffii, a nontumorous mutant of it, their F1, and a backcross to the tumorous parent. Backcross segregation ratios were shown to be compatible with a “single gene” hypothesis, the F1 plant being nontumorous but showing a low percentage of tumors induced by wounds, 6-azauracil or X-rays.In vitro studies of excised pith tissue grown on Linsmaier and Skoog medium for different periods of time showed the presence, confirmed by cytological analyses, of amplification of highly repetitive sequences only in the nontumorous stock, as judged by reassociation experiments in the first 24-96 hours of culture. CsCl analytical ultracentrifugation of those sequences showed the appearance in the same stock of a heavy DNA satellite (density = 1.721 gm/ml), whose presence was also confirmed by derivative melting curves.Amplification seemed to be essential for the initiation of cell division, which was completely inhibited in the nontumorous genotype and partially influenced in the F1 by incorporation during the critical period (24-96 hours of the primary explant) of 5-bromo-2′-deoxy-uridine.The results are discussed in terms of an hypothesis of an integrated gene-controlled, hormone-mediated regulatory system of cell proliferation involving changes in target repetitive DNA sequences.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/dvg.1020030104
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  • 4
    Electronic Resource
    Electronic Resource
    A comparison of genome modifications leading to genetic and epigenetic tumorous transformation in Nicotiana spp. tissue cultures (1986)
    Chichester [u.a.] : Wiley-Blackwell
    Developmental Genetics 7 (1986), S. 51-64 
    Details
    ISSN: 0192-253X
    Keywords: tumorous and nontumorous genotypes ; repetitive DNA ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: A single system is presented, where both genetic and epigenetic control of tumor induction can be studied at the same time. This system is offered by the amphidiploid tumorous hybrid Nicotiana glauca × N. langsdorffii, a nontumorous mutant of it and the nontumorous parent species N. glauca and N. langsdorffii. The aim of the present paper is to compare long-term in vitro cultures of tumorous (genetic and habituated), and nontumorous strains, through the characterization of their genomes according to several physico-chemical parameters. The data reported show that both qualitative and quantitative differences in DNA complexity are correlated with the tumorous transformation. Particularly, a high degree of mismatching between the DNAs of the tumorous and nontumorous hybrids and the lack, in the second genotype (nontumorous), of three DNA peaks in Ag+-Cs2SO4 analytical ultracentrifugation profile seem to support the hypothesis, suggested in a previous paper, of the presence, in the nontumorous mutant, of a gross chromosomal rearrangement, probably a deletion. Amplification and underreplication of specific sequences also seemed to be correlated with changes from the normal to the tumorous state, highly repetitive sequences being present in higher amounts in the normal strains and in the habituated N. glauca than in the case of the tumorous hybrid.Finally, DNA bound ion contents were found to be strikingly higher in tumorous than in nontumorous tissues. The results are discussed in the frame of the general hypothesis of high somatic genomic plasticity in plants.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/dvg.1020070105
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    Paper (German National Licenses)
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