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  • tumorous and nontumorous genotypes  (2)
  • 1
    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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  • 2
    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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