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  • 1
    Electronic Resource
    Electronic Resource
    Selection and characterisation of flavanone 3-hydroxylase mutants ofDahlia, Streptocarpus, Verbena andZinnia (1984)
    Springer
    Planta 161 (1984), S. 261-265 
    Details
    ISSN: 1432-2048
    Keywords: Acyanic mutants ; Anthocyanin biosynthesis ; Dahlia ; Flavanone 3-hydroxylase ; Mutant (white-flowering) ; Streptocarpus ; Verbena ; Zinnia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Precursor experiments and chromatographic studies indicate that the hydroxylation of flavanones in the 3-position to dihydroflavonols is blocked in special white-flowering mutants ofDahlia, Streptocarpus, Verbena andZinnia. The result of our investigations was confirmed in as much as the activity of the enzyme flavanone 3-hydroxylase, which catalyses the conversion of flavanones to dihydroflavonols, could readily be detected in flower extracts of cyanic strains of the four plant species. It was found to be, however, completely absent in flower extracts of the corresponding acyanic mutants. Thus, the interruption of the anthocyanin pathway in these mutants is clearly caused by a lack of this enzyme activity. Similar to the enzymes from other sources, the 3-hydroxylases ofDahlia, Streptocarpus, Verbena andZinnia are soluble enzymes; they belong to the 2-oxoglutarate-dependent dioxygenases and the reaction is inhibited by ethylenediaminetetraacetic acid, KCN and diethyldithiocarbamate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00982923
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  • 2
    Electronic Resource
    Electronic Resource
    Genetic and biochemical studies on the conversion of flavanones to dihydroflavonols in flowers of Petunia hybrida (1985)
    Springer
    Theoretical and applied genetics 70 (1985), S. 561-568 
    Details
    ISSN: 1432-2242
    Keywords: Anthocyanin-Biosynthesis ; Flavonoids ; Flavanone 3-hydroxylase ; Genetic Control ; Petunia hybrida
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Chemogenetic investigations and precursor experiments on flowers of Petunia hybrida suggest that recessive alleles of the gene An3 block the biosynthetic pathway of flavonols and anthocyanins between the flavanone and dihydroflavonol step. In confirmation of this hypothesis, activity of the enzyme flavanone 3-hydroxylase, which catalyses the conversion of flavanones to dihydroflavonols, was readily demonstrated in enzyme preparations from flowers of lines with the dominant allele An3, whereas no or very low activity could be found in extracts from lines with recessive alleles (an3an3). A second genetic factor is described which clearly reduces the amount of flavonols in the flowers but not the amount of anthocyanins. Crossing experiments revealed that this factor represents a third allele of the An3 gene. It is referred to as an3-1. As expected, a residual flavanone 3-hydroxylase activity of about 10% could be found in enzyme extracts from plants with the an3-1 allele. The decreased level of dihydroflavonol formed under this condition is obviously still sufficient for anthocyanin formation but not for flavonol synthesis. Similar to flavanone 3-hydroxylases from other plants, the enzyme of Petunia is a soluble enzyme and belongs according to its cofactor requirements to the 2-oxoglutarate-dependent dioxygenases. The residual flavanone 3-hydroxylase activity found in plants with the an3-1 allele is identical to the activity extracted from An3-genotypes with regard to cofactors, substrate specificity and most of the inhibitors. The difference observed in the respective pH-optima and the genetic data suggest that the mutation providing the an3-1 phenotype is localized in the structural gene for flavanone 3-hydroxylase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00305991
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    Paper (German National Licenses)
    Fulltext
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