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  • 1
    Electronic Resource
    Electronic Resource
    Regulation of the xylanase-encoding xlnA gene of Aspergilius tubigensis (1994)
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 12 (1994), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: A gene encoding an endo-1,4-β-xylanase from Aspergillus tubigensis was cloned by oligonucleotide screening using oligonucleotides derived from amino acid sequence data obtained from the purified protein. The isolated gene was functional as it could be expressed in the very closely related fungus Aspergillus niger. The xylanase encoded by this gene is synthesized as a protein of 211 amino acids. After cleavage of the presumed prepropeptide this results in a mature protein of 184 amino acids with a molecular weight of 19 kDa and an isoelectric point of 3.6. The regulatory region of the xlnA gene was studied with respect to the response to xylan induction and carbon catabolite repression. By deletion analysis of the 5′ upstream region of the gene a 158bp region involved in the xylan specific induction was identified. To study this regulatory element a reporter system for transcriptional activating sequences was developed that is based on the A. niger glucose oxidase-encoding gene. From the results with this reporter system it is concluded that this 158bp fragment not only contains the information required for induction of transcription but that it also plays a role in carbon catabolite repression of the xlnA gene. The region directly upstream of this fragment contains four potential CREA target sites; deletion of this region leads to an increase in the level of transcription. These results suggest that carbon catabolite repression of the xinA gene is controlled at two levels, directly by repression of xlnA gene transcription and indirectly by repression of the expression of a transcriptional activator. This type of mechanism would be similar to the double lock mechanism for the regulation of gene expression of alcA in Aspergillus nidulans. The reporter system was also used to study the regulation of expression via the functions located on this fragment in A. niger and in A. niduians. Essentially the same pattern of regulation was found in both of these hosts. Therefore, regulation of xylanase gene expression is basically conserved in ail three aspergilli.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.1994.tb01036.x
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  • 2
    Electronic Resource
    Electronic Resource
    Response of selected antioxidants and pigments in tissues of Rosa hybrida and Fuchsia hybrida to supplemental UV-A exposure (2003)
    Oxford, UK : Munksgaard International Publishers
    Physiologia plantarum 117 (2003), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The effect of supplemental UV-A (320–400 nm) radiation on tissue absorption at 355 nm, levels of various antioxidants (ascorbate, glutathione, carotenoids and flavonoids) and of antioxidant scavenging capacity were investigated with leaves and petals of Rosa hybrida, cv. Honesty and with leaves, petals and sepals of Fuchsia hybrida, cv. Dollarprinzessin. Supplemental UV-A did not result in visible changes in plant morphology of either species. In leaves it induced small increases in levels of chlorophylls a and b, the carotenoids antheraxanthin, lutein and β-carotene, and high increases in the flavonols quercetin and kaempferol. Petals hardly responded, while the coloured sepals of fuchsia showed an increase in quercetin derivatives. HPLC of unhydrolysed flavonoids showed that individual quercetin derivatives in leaves of both species and kaempferol derivatives in rose leaves increased 2-fold. Some kaempferol derivatives in fuchsia leaves were more than 2-fold enhanced or were newly induced by supplemental UV-A. Increases in l-ascorbic acid levels in fuchsia leaves, and decreases in rose leaves as result of supplemental UV-A were observed, but differences appeared statistically not significant, while l-ascorbate levels remained unchanged in the other tissues investigated. Anthocyanins and reduced glutathione levels were unaffected in all tissues. The combined UV-A induced increases in concentrations of these antioxidant species, did not lead to significant increases in antioxidant capacity of tissues, measured as Trolox equivalents in 50%-ethanol extracts. Light absorption at 355 nm of leaf extracts was significantly increased upon UV-A exposure. Our results indicate that the major protection towards UV-A exposure, in particular in the leaves, will originate from absorption of irradiation, and not from scavenging reactive oxygen species.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1034/j.1399-3054.2003.00037.x
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  • 3
    Electronic Resource
    Electronic Resource
    Characterisation of the Aspergillus nidulans frA1 mutant: hexose phosphorylation and apparent lack of involvement of hexokinase in glucose repression (1996)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 139 (1996), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract Hexose phosphorylation was studied in Aspergillus nidulans wild-type and in a fructose non-utilising mutant (frA). The data indicate the presence of at least one hexokinase and one glucokinase in wild-type A. nidulans, while the frA1 mutant lacks hexokinase activity. The A. nidulans gene encoding hexokinase was isolated by complementation of the frA1 mutation. The absence of hexokinase activity in the frA1 mutant did not interfere with glucose repression of the enzymes involved in alcohol and l-arabinose catabolism. This suggests that, unlike the situation in yeast where mutation of hexokinase PII abolishes glucose repression, the A. nidulans hexokinase might not be involved in glucose repression.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.1996.tb08206.x
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  • 4
    Electronic Resource
    Electronic Resource
    Induction of glucose oxidase, catalase, and lactonase in Aspergillus niger (1993)
    Springer
    Current genetics 24 (1993), S. 408-416 
    Details
    ISSN: 1432-0983
    Keywords: Aspergillus ; Glucose oxidase ; Catalase ; Lactonase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The induction of glucose oxidase, catalase, and lactonase activities was studied both in wild-type and in glucose oxidase regulatory and structural mutants of Aspergillus niger. The structural gene for glucose oxidase was isolated and used for Northern analysis and in transformation experiments using various gox mutations. Wild-type phenotype could be restored in the glucose oxidase-negative mutant (goxC) by transformation with the structural gene. We conclude, therefore, that the goxC marker which is located on chromosome 2 represents the structural gene of glucose oxidase. Glucose and a high oxygen level are necessary for the induction of all three enzyme activities in the wild-type strain and it was shown that both glucose and oxygen effects reflect regulation at the transcriptional level. The goxB mutation results in constitutive expression of all three activities although modulated to some extent by the carbon source. The goxE mutation only has an effect on lactonase and glucose oxidase expression and does not relieve the necessity for a high oxygen level. Catalase and lactonase could not be induced in the glucose oxidase-negative strain (goxC). Addition of H2O2 resulted in the induction of all three enzymes in the wild-type without glucose being present. The H2O2 induction is probably mediated by the goxB product. Besides the H2O2 induction there is still an effect of the carbon source on the induction. A model for induction of glucose oxidase, catalase, and lactonase in A. niger is discussed. Transformation of wild-type and goxC strains with the goxC gene resulted in only a 3–4 fold increase of glucose oxidase activity relative to the wild-type even though more than 25 copies of the structural gene were present. Transformation of the goxB strain gave higher activities but resulted in poor growth. Aspergillus nidulans does not have a glucose oxidase activity, but could be transformed with the A. niger goxC gene to a glucose oxidase-producing strain. Induction in these transformants was comparable to that in A. niger with respect to the carbon source dependency, but there was no oxygen dependencey of induction. The glucose oxidase produced by the A. nidulans transformants was kinetically indistinguishable from the A. niger enzyme, but it showed small differences in glycosylation pattern.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00351849
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