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  • 1
    ISSN: 1520-4995
    Source: ACS Legacy Archives
    Topics: Biology , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    Molecular microbiology 37 (2000), S. 0 
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Amino acid limitation results in impaired sexual fruit body formation in filamentous fungi such as Aspergillus nidulans. The starvation signal is perceived by the cross-pathway regulatory network controlling the biosynthesis of translational precursors and results in increased expression of a transcriptional activator encoded by a c-Jun homologue. In the presence of amino acids, the gene product of the mammalian RACK1 homologue cpcB is required to repress the network. Growth under amino acid starvation conditions permits the initiation of the sexual developmental programme of the fungus, but blocks fruit body formation before completion of meiosis. Accordingly, arrest at this defined control point results in microcleistothecia filled with hyphae. Addition of amino acids results in release of the block and completion of development to mature ascospores. The same developmental block is induced by either overexpression of c-Jun homologues or deletion of the RACK1 homologue cpcB of A. nidulans in the presence of amino acids. Therefore, the amino acid starvation signal regulates sexual development through the network that also controls the amino acid biosynthetic genes. Expression of the RACK1 gene suppresses the block in development caused by a deletion of cpcB. These data illuminate a connection between metabolism and sexual development in filamentous fungi.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The general control transcriptional regulator gene cpcA of Aspergillus niger was cloned by complementation of a Saccharomyces cerevisiaeΔgcn4 mutant strain. The encoded protein conferred resistance to amino acid analogues when expressed in yeast. Disruption of cpcA in A. niger resulted in a strain which is sensitive towards 3-aminotriazole and fails to respond to amino acid starvation. cpcA encodes a transcript of ≈2400 nucleotides in length that includes a 5′ leader region of 900 nucleotides. The 5′ leader region contains two small open reading frames, suggesting translational control of gene expression. Steady-state mRNA levels of cpcA increase by a factor of three upon amino acid starvation. The coding region of cpcA is interrupted by a 57 bp intron and the deduced amino acid sequence displays an ≈30% overall identity to yeast GCN4p and Neurospora crassa cpc-1p. Critical amino acid residues of the transcriptional activation domains of GCN4p are conserved in cpcAp. The basic DNA-binding domain shows up to 70% amino acid sequence identity to other basic zipper (bZIP)-type transcriptional activators. cpcAp binds specifically to a GCN4p recognition element in gel retardation experiments. The C-terminal dimerization domain encodes a leucine zipper with only a single leucine residue.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Archives of microbiology 172 (1999), S. 157-166 
    ISSN: 1432-072X
    Keywords: Key wordsAspergillus nidulans ; Tryptophan ; biosynthesis ; Fruitbody formation ; Auxin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The interplay between sexual development and amino acid biosynthesis in the ascomycete Aspergillus nidulans was studied. The growth and differentiation of four tryptophan auxotrophic strains that are unable to regulate their tryptophan biosynthesis, were examined. These strains are sterile on medium containing low tryptophan concentrations. Fruitbody formation was restored by supplementation with high concentrations of tryptophan and was promoted by supplementation with indole or auxin. Tryptophan supplementation resulted in auxin production of A. nidulans. Fertility of ascospores of the tryptophan auxotrophic strains could only be partially re-established. trpC transcript levels and enzyme activities remained stable in cleistothecia and conidiophore extracts as compared to those of mycelium, while levels of gene transcripts involved in glycolysis were lower in fruitbodies and conidiospores. Auxotrophic strains unable to form fruitbodies at intermediate amino acid supplementation levels turned on the cross-pathway regulatory system that is induced by amino acid starvation. We conclude that there is a connection between the genetic network of cross-pathway control and sexual development in A. nidulans.
    Type of Medium: Electronic Resource
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