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  • 1
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Calcium signalling is little understood in filamentous fungi largely because easy and routine methods for calcium measurement in living hyphae have previously been unavailable. We have developed the recombinant aequorin method for this purpose. High levels of aequorin expression were obtained in Neurospora crassa, Aspergillus niger and Aspergillus awamori by codon optimization of the aequorin gene. Three external stimuli (mechanical perturbation, hypo-osmotic shock and high external calcium) were found transiently to increase [Ca2+]c. Each of the calcium signatures associated with these physico-chemical treatments was unique, suggesting the involvement of three distinct calcium-mediated signal transduction pathways. The fungal calcium channel blocker KP4 inhibited the [Ca2+]c responses to hypo-osmotic shock and high external calcium, but not to mechanical perturbation. The divalent cation chelator BAPTA inhibited [Ca2+]c responses to mechanical perturbation and hypo-osmotic shock. The calcium agonists A23187 and cyclopiazonic acid increased [Ca2+]c levels.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary The construction and characterization of glyceraldehyde-3-phosphate-dehydrogenase (GPD) overproducing transformants of Aspergillus nidulans and their behaviour in acetate-limited continuous cultures and glucose-grown batch cultures are described. The A. nidulans acetamidase deletion strain MH1277 was transormed with the homologous gpdA gene on a vector with the homologous acetamidase-gene (amdS) as a selection marker. Transformant Al contains about nine integrated copies of the gpdA gene, and shows a proportional gene-dosage GPD production of about 22% of the total soluble cell protein. Compared to the wild-type MH1277, Al has higher growth yields and reaches higher specific growth rates on both acetate and glucose, which could be due to the key position of GPD in glycolysis and gluconeogenesis.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-0983
    Keywords: Reporter gene ; Filamentous fungi ; Pathogenicity ; β-glucuronidase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A chimaeric β-glucuronidase (GUS) gene has been created by ligating the Aspergillus nidulans glyceraldehyde 3-phosphate dehydrogenase promoter to the coding sequence of the E. coli uidA gene. Cotransformation of this vector into A. nidulans, A. niger and the tomato pathogen Fulvia fulva (syn. Cladosporium fulvum (Cooke)) resulted in the expression of β-glucuronidase. GUS activity was detected by growth on agar media containing X-gluc and by enzyme assays of mycelial extracts. Expression of the gene in F. fulva transformants was also easily detectable during growth in plants and did not affect pathogenicity. These results form the basis for a versatile and sensitive reporter gene system for industrial and phytopathogenic filamentous fungi.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract  A synthetic derivative of the cutinase cDNA of Fusarium solani pisi was expressed in Aspergillus awamori using the A. awamori endoxylanase II (exlA) promoter and terminator. The influence of the origin of the pre-sequence and the presence of a pro-sequence on the efficiency of extracellular cutinase production was analysed in single-copy transformants containing an expression cassette integrated at the pyrG locus. Transformants containing a construct encoding a direct, in-frame fusion of the xylanase pre-peptide to the mature cutinase showed a 2-fold higher cutinase production level compared to strains containing constructs with an additional cutinase pro-peptide. The effect of multicopy integration of the expression cassette on cutinase production was analysed in strains with different numbers of a cutinase construct containing its own pre-prosequence. The multicopy strains showed a 6- to 12-fold increased production of extracellular cutinase relative to the single-copy strains. No linear dose response relation to the number of expression cassettes present in the strains was observed. The amount of active enzyme produced by the strains correlated with the amount of cutinase-specific mRNA, suggesting that cutinase overproduction is not limited at the level of translation or secretion.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract  A new, highly inducible fungal promoter derived from the Aspergillus awamori 1,4-β-endoxylanase A (exlA) gene is described. Induction analysis, carried out with the wild-type strain in shake flasks, showed that exlA expression is regulated at the transcriptional level. Using a β-glucuronidase (uidA) reporter strategy, D-xylose was shown to be an efficient inducer of the exlA promoter, whereas sucrose or maltodextrin were not. Upon D-xylose induction, the exlA promoter was threefold more efficient than the frequently used A. niger glucoamylase (glaA) promoter under maltodextrin induction. Detailed induction analyses demonstrated that induction was dependent on the presence of D-xylose in the medium. Carbon-source-limited chemostat cultures with the uidA reporter strain showed that D-xylose was also a very good inducer in a fermenter, even in the presence of sucrose.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Applied microbiology and biotechnology 43 (1995), S. 195-205 
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract  During the last 5 years, strain improvement by genetic engineering has been established as a good alternative for traditional methods of strain improvement such as mutagenesis and genetic recombination. Considerable success has been achieved in the overproduction of a variety of fungal proteins. However, from the available data a limitation at the level of transcription is evident. A more detailed analysis of this transcription limitation was carried out for the overproduction of glucoamylase in A. niger. This analysis revealed that both the site of integration of introduced gene copies and the available amount of trans-acting regulatory proteins were at the root of the observed limitation. Based on these results, approaches for the construction of a new generation of protein-overproducing strains are suggested.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Applied microbiology and biotechnology 43 (1995), S. 195-205 
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract During the last 5 years, strain improvement by genetic engineering has been established as a good alternative for traditional methods of strain improvement such as mutagenesis and genetic recombination. Considerable success has been achieved in the overproduction of a variety of fungal proteins. However, from the available data a limitation at the level of transcription is evident. A more detailed analysis of this transcription limitation was carried out for the overproduction of glucoamylase in A. niger. This analysis revealed that both the site of integration of introduced gene copies and the available amount of trans-acting regulatory proteins were at the root of the observed limitation. Based on these results, approaches for the construction of a new generation of protein-overproducing strains are suggested.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Applied microbiology and biotechnology 47 (1997), S. 1-11 
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Filamentous fungi are widely used for the production of homologous and heterologous proteins but, compared to homologous proteins, the levels of production of heterologous proteins are usually low. During the last 5 years, the levels of production of heterologous proteins have been drastically improved by fusing the corresponding gene to the 3' end of a homologous gene, encoding a well-secreted protein such as glucoamylase. Nevertheless, little research has been carried out to determine the limitations that hamper heterologous protein production. Recently we have carried out a detailed analysis of the levels of production of several proteins and glucoamylase fusion proteins in defined recombinant Aspergillus awamori strains. In this review we will focus on the use of filamentous fungi for the production of heterologous, especially non-fungal, proteins. In particular, the effect of gene-fusion strategies will be reviewed. Furthermore, the remaining limitations in heterologous protein production and suggestions for improvement strategies for overproduction of these protein will be discussed.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract  Introduction in the fungus Aspergillus niger of multiple copies of the A. niger bphA gene, encoding the cytochrome P450 enzyme benzoate p-hydroxylase, did not result in increased activities of this enzyme [Gorcom RFM van, et al. Mol Gen Genet (1990) 223: 192–197] probably because of low expression levels of the gene encoding the second component of the microsomal cytochrome P450 enzyme system, cytochrome P450 reductase. For improvement of this and other cytochrome-P450-dependent reactions, A. niger strains were constructed in which the copy number of the A. niger cprA gene (encoding cytochrome-P450 reductase) or the copy numbers of both cprA and the cytochrome-P450-encoding gene were increased. Expression of both genes was controlled by their own transcription control regions. Benzoate p-hydroxylase activity of different trans- formants was determined in microsomal fractions using a newly developed indirect in vitro assay. In trans- formants containing multiple copies of both genes, benzoate p-hydroxylase activity was significantly higher than in the wild-type strain or in transform- ants in which the copy number of only one of the genes was increased. These results clearly indicate the importance of co-expression of cytochrome-P450 reductase for achieving maximal cytochrome P450 activities in cytochrome-P450-overproducing filamentous fungi.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The function of the endoplasmic-reticulum-localized chaperone binding protein (BiP) in relation to protein secretion in filamentous fungi was studied. It was shown that the overproduction of several homologous and heterologous recombinant proteins by Aspergillus strains induces the expression of bipA, the BiP-encoding gene from Aspergillus niger and Aspergillus awamori. As this result could imply that BiP plays a role in protein overproduction, the effect of modulation of bipA gene expression on protein secretion was studied in several recombinant strains expressing glucoamylase (glaA) fusion genes. For overproduction of BiPA in these strains, extra copies of the bipA gene under the control of an inducible promoter were introduced. To allow analysis of the effect of a decreased bipA expression level on protein secretion, replacement of the wild-type gene for a bipA gene driven by the glaA promoter was attempted. However, this endeavour failed because of the lethality of this replacement. Although the final amount of secreted recombinant protein did not change significantly in strains with increased BiPA levels, increased levels of unprocessed fusion protein were detected in the total protein extracts of these strains.
    Type of Medium: Electronic Resource
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