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  • 1
    Electronic Resource
    Electronic Resource
    Rapid changes in amplification and methylation pattern of genomic DNA in cultured carrot root explants (Daucus carota L.) (1993)
    Springer
    Theoretical and applied genetics 85 (1993), S. 793-800 
    Details
    ISSN: 1432-2242
    Keywords: Daucus carota L. ; Tissue culture ; Growth regulator ; Genomic DNA ; Methylation ; Differential replication ; Rejuvenilization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Rapid genomic DNA variation due to methylation and copy number alteration was observed in carrot root explants 6 h after inoculation and during a 36-h period of exponential callus growth. De novo methylation and amplification of restricted BspNI fragments of low molecular weight occurred before cell cycle activation and should, therefore, be independent of progression through the S-phase of the cell cycle. Growth regulators seemed to influence the amplification pattern indirectly by regulating cell division activity. In exponentially growing callus tissue the copy number of most of the repetitive fragments was dramatically reduced. It is presumed that this reduction in the copy number of repetitive fragments is characteristic of ‘rejuvenilization’. 3-Indole-acetic-acid (IAA) and inositol in the medium increased the degree of unspecific genomic DNA methylation in growing rhizogenic carrot callus tissue in the absence of kinetin, which inhibits root induction at that stage. A possible relation to the induction of rhizogenesis is considered. The observed reduction in number of repetitive restriction fragments and the increase in DNA methylation are gross changes covering the total genome. The results are discussed in relation to the controversy concerning the general biological significance of the methylation and amplification of DNA sequences.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00225021
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  • 2
    Electronic Resource
    Electronic Resource
    Physiological aspects of genome variability in tissue culture. I. Growth phase-dependent differential DNA methylation of the carrot genome (Daucus carota L.) during primary culture (1995)
    Springer
    Theoretical and applied genetics 91 (1995), S. 809-815 
    Details
    ISSN: 1432-2242
    Keywords: Daucus carota L. ; Tissue culture ; Differential DNA methylation ; Cell-division growth ; Kinetin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Investigations were performed on growth phase-dependent EcoRII site-specific DNA methylation of the carrot genome during primary culture to elucidate physiological aspects of genome DNA variability in tissue culture. While DNA methylation of the root cambium and the secondary phloem and petioles of carrot leaves were strikingly different, the methylation level of the secondary phloem seemed to be independent of cultivar origin, the age of the plants and the extent of secondary root growth. As was shown earlier a change in the differentiated state of the secondary phloem by tissue culture leads to changes in genome modification. Whereas de novo methylation was observed during the first 2 weeks of growth initiation, the results presented demonstrate genome de-methylation during the transition to stationary growth indicating differential εnome methylation during different phases of culture. The presence of kinetin in the nutrient medium of the primary culture was found to be antagonistic to changes in genome modification in general. De novo methylation and subsequent de-methylation of the carrot genome are discussed as gross changes obviously essential to molecular genome differentiation during tissue culture.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00220964
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  • 3
    Electronic Resource
    Electronic Resource
    Physiological aspects of genome variability in tissue culture. II. Growth phase-dependent quantitative variability of repetitive BstNI fragments of primary cultures of Daucus carota L. (1995)
    Springer
    Theoretical and applied genetics 91 (1995), S. 816-823 
    Details
    ISSN: 1432-2242
    Keywords: Daucus carota L. ; Tissue culture ; Differential DNA replication ; Cell-division growth ; Cell determination
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Systematic investigations on the occurrence of differential DNA replication in carrot cultures, expressed at the total genome level, were performed. The genome of Daucus carota L. could be characterized by a pattern of repetitive BstNI fragments that was independent of tissue specificity or cultivar differences. Characterization of the genomic DNA of the secondary phloem of carrot roots, in comparison to the DNA of the induced primary cultures at different growth phases, revealed dramatic differences in the copy number of the repetitive fragments. Highly proliferative tissue showed extensive reduction in the proportion of repetitive sequences in the genome in all of the 37 investigated variants. In contrast, during subsequent transition to stationary growth the repetitive fragments re-amplified. The results suggest that the quantitative genome organisation was involved in the regulation of the growth potential of cells. A hypothesis is discussed suggesting a determining influence of the observed differential DNA replication on cell-cycle rates and the cell program of proliferative tissue by structural and positioning effects on DNA loops. To study the causality of somaclonal variation, research on the relationship between physiological genome variability and the induction of heritable changes is recommended.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00220965
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  • 4
    Electronic Resource
    Electronic Resource
    Variable methylation and differential replication of genomic DNA in cultured carrot root expiants during growth induction as influenced by hormonal treatments (1991)
    Springer
    Theoretical and applied genetics 82 (1991), S. 283-288 
    Details
    ISSN: 1432-2242
    Keywords: Daucus carota L. ; Tissue culture ; Hormones ; DNA methylation ; Differential replication ; Transitory genomic variation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The methylation and amplification pattern of genomic DNA of carrot root expiants (Daucus carota L.) undergoes transitory changes during the cultural cycle. A high degree of variation was observed as early as 36 h after the incubation of fresh expiants in the nutrient medium and, depending on the hormonal treatment significant modifications occurred during 14 days of culture. Proliferative tissue conditioned by kinetin showed an extensive reduction in DNA methylation. Changes in the DNA amplification pattern were not necessarily linked to methylation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02190613
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