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  • 1
    Electronic Resource
    Electronic Resource
    Conservation of structure and function of the aflatoxin regulatory geneaflR fromAspergillus nidulans andA. flavus (1996)
    Springer
    Current genetics 29 (1996), S. 549-555 
    Details
    ISSN: 1432-0983
    Keywords: allR ; Aflatoxin ; Secondary metabolism ; Zinc binuclear cluster
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Under limiting growth conditions,Aspergillus nidulans produces a carcinogenic secondary metabolite related to aflatoxin and called sterigmatocystin (ST). The genes for ST biosynthesis are co-ordinately regulated and are all found within an approximately 60-kilobase segment of DNA. One of the genes within this region is predicted to encode a CX2CX6CX6CX2CX6CX2 zinc binuclear cluster DNA-binding protein that is related to theAspergillus flavus andAspergillus parasiticus aflatoxin regulatory geneaflR. Deletion of theA. nidulans aflR homolog resulted in an inability to induce expression of genes within the ST gene cluster and a loss of ST production. BecauseA. nidulans aflR mRNA accumulates specifically under conditions that favor ST production we expect that activation of ST biosynthetic genes is determined byA. nidulans aflR. In support of this hypothesis, we demonstrated that induced expression of theA. flavus aflR gene inA. nidulans, under conditions that normally suppress ST gene expression, resulted in activation of genes in the ST biosynthetic pathway. This result demonstrates that AflR function is conserved betweenAspergillus spp. and thataflR expression is sufficient to activate genes in the ST pathway.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02426959
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  • 2
    Electronic Resource
    Electronic Resource
    Sequence-specific binding by Aspergillus nidulans AflR, a C6 zinc cluster protein regulating mycotoxin biosynthesis (1998)
    Oxford BSL : Blackwell Science Ltd
    Molecular microbiology 28 (1998), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The Aspergillus nidulans aflR gene is found within a 60 kb gene cluster that includes ≈24 other genes that putatively function in the production of the aflatoxin-related mycotoxin sterigmatocystin. Previous work showed that AflR is a C6 zinc binuclear cluster protein that is conserved across Aspergillus spp. and functions as a pathway-specific transcription factor in activating expression of other cluster genes. In this report, we demonstrate that A. nidulans AflR (AnAflR) is a 45 kDa protein that binds to the palindromic sequence 5′-TCG(N5)CGA-3′ found in the promoter regions of several aflatoxin and sterigmatocystin cluster genes (stc genes). The in vivo relevance of this AnAflR binding site was assessed by examining the contribution of the three TCG(N5)CGA elements in the 1.1 kb promoter region of stcU using gene fusions with the bacterial uidA gene encoding β-glucuronidase (GUS). By mutating one, two or all three of the AnAflR-binding elements and examining GUS activity in wild-type aflR or ΔaflR A. nidulans strains, we found that stc gene activation required both AnAflR and at least one TCG(N5)CGA AflR binding site.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.1998.00907.x
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  • 3
    Electronic Resource
    Electronic Resource
    Blockage of methylcitrate cycle inhibits polyketide production in Aspergillus nidulans (2004)
    Oxford, UK : Blackwell Science Ltd
    Molecular microbiology 52 (2004), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Aspergillus nidulans produces the polyketide toxin sterigmatocystin (ST) of which the biosynthetic and pathway specific regulatory genes compose a stc gene cluster. A previous mutagenesis screen identified 23 mutants defective in production of ST. Five mutants constitute a single locus. Genetic complementation and sequencing analysis revealed the mutant locus to be mcsA encoding methylcitrate synthase that converts propionyl-CoA to methylcitrate. Feeding downstream products of methylcitrate synthase, methylcitrate and pyruvate, did not restore ST production in mcsA mutants, indicating that loss of methylcitrate cycle products is not the cause of the ST defect. However, propionate, a precursor for propionyl-CoA, inhibited ST production and induced transcription of mcsA in the wild type. Furthermore, propionate impaired formation of two polyketide spore pigments whereas overexpression of mcsA relieved inhibition of ST production by propionate. Transcription analyses revealed that disruption of mcsA did not affect expression of the specialized fatty acid synthase genes (stcJ and stcK) or polyketide synthase gene (stcA) required for formation of norsolorinic acid (NOR), the first stable intermediate in the ST biosynthetic pathway. Feeding studies showed that NOR but not hexanoic acid (the fatty acid produced by StcJ/StcK and primer unit of StcA) or malonate (source of the extender unit of StcA) restored ST production in the mcsA mutant. We hypothesize that excess buildup of propionyl-CoA in mcsA mutants interferes with polyketide synthase activity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.2004.03994.x
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  • 4
    Electronic Resource
    Electronic Resource
    Mitochondrial β-oxidation in Aspergillus nidulans (2004)
    Oxford, UK : Blackwell Publishing Ltd.
    Molecular microbiology 54 (2004), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: β-Oxidation (β-ox) occurs exclusively in the peroxisomes of Saccharomyces cerevisiae and other yeasts, leading to the supposition that fungi lack mitochondrial β-ox. Here we present unequivocal evidence that the filamentous fungus Aspergillus nidulans houses both peroxisomal and mitochondrial β-ox. While growth of a peroxisomal β-ox disruption mutant (ΔfoxA) was eliminated on a very long-chain fatty acid (C22:1), growth was only partially impeded on a long-chain fatty acid (C18:1) and was not affected at all on short chain (C4–C6) fatty acids. In contrast, growth of a putative enoyl-CoA hydratase mutant (ΔechA) was abolished on short-chain and severely restricted on long- and very long-chain fatty acids. Furthermore fatty acids inhibited growth of the ΔechA mutant but not the ΔfoxA mutant in the presence of an alternate carbon source (lactose). Disruption of echA led to a 28-fold reduction in 2-butenoyl-CoA hydratase activity in a preparation of organelles. EchA was also required for growth on isoleucine and valine. The subcellular localization of the FoxA and EchA proteins was confirmed through the use of red and green fluorescent protein fusions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.2004.04340.x
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  • 5
    Electronic Resource
    Electronic Resource
    Requirement of spermidine for developmental transitions in Aspergillus nidulans (2002)
    Oxford, UK : Blackwell Science Ltd
    Molecular microbiology 46 (2002), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Deletion of the spermidine synthase gene in the fungus Aspergillus nidulans results in a strain, ΔspdA, which requires spermidine for growth and accumulates putrescine as the sole polyamine. Vegetative growth but not sporulation or sterigmatocystin production is observed when ΔspdA is grown on media supplemented with 0.05–0.10 mM exogenous spermidine. Supplementation of ΔspdA with ≥ 0.10 mM spermidine restores sterigmatocystin production and ≥ 0.50 mM spermidine produces a phenotype with denser asexual spore production and decreased radial hyphal growth compared with the wild type. ΔspdA spores germinate in unsupplemented media but germ tube growth ceases after 8 h upon which time the spores swell to approximately three times their normal diameter. Hyphal growth is resumed upon addition of 1.0 mM spermidine. Suppression of a G protein signalling pathway could not force asexual sporulation and sterigmatocystin production in ΔspdA strains grown in media lacking spermidine but could force both processes in ΔspdA strains supplemented with 0.05 mM spermidine. These results show that increasing levels of spermidine are required for the transitions from (i) germ tube to hyphal growth and (ii) hyphal growth to tissue differentiation and secondary metabolism. Suppression of G protein signalling can over-ride the spermidine requirement for the latter but not the former transition.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.2002.03201.x
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  • 6
    Electronic Resource
    Electronic Resource
    Mitotic stability of transforming DNA is determined by its chromosomal configuration in the fungus Cochliobolus heterostrophus (1991)
    Springer
    Current genetics 19 (1991), S. 227-233 
    Details
    ISSN: 1432-0983
    Keywords: Cochliobolus ; Transformation ; DNA instability ; Homologous recombination ; Ectopic integration ; DNA methylation ; Plant disease
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Cochliobolus heterostrophus was transformed with a plasmid (pH1S) containing a bacterial gene (hygB), which confers resistance to the antibiotic hygromycin B when under control of an 838-bp fragment of promoter 1 from C. heterostrophus. The plasmid integrated at either homologous (52% single copy, 33% tandemly repeated copies) or ectopic (4% single copy, 11% tandemly repeated copies) sites on different chromosomes, resulting in four distinct configurations of integrated DNA. All four configurations were highly stable during mitotic growth; virtually no loss of integrated DNA was detected after five subcultures on nonselective medium or after seven cycles of pathogenesis on maize, the normal host of this fungus. However, deletion of integrated DNA was detected after eight or more disease cycles. The frequency of deletion depended on the configuration of the recombinant chromosome. A single copy of pH1S integrated at an homologous site was flanked by direct repeats of the target sequence and was least stable; up to 50% of the population lacked integrated DNA after 12 disease cycles. A single copy integrated at an ectopic site had no repeated DNA directly associated with it and was the most stable; no deletions were detected after 12 disease cycles. Tandemly repeated copies of pH1S integrated at either homologous or ectopic sites appeared to have intermediate stability; 2–18% of each population lost at least one copy after 12 disease cycles, although in no case were all copies deleted. Cytosine residues of integrated DNA were methylated during mitotic growth, but this had no apparent effect on the expression of hygB.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00336491
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  • 7
    Electronic Resource
    Electronic Resource
    Variable electrophoretic karyotypes of members of Aspergillus Section Flavi (1992)
    Springer
    Current genetics 21 (1992), S. 371-375 
    Details
    ISSN: 1432-0983
    Keywords: Electrophoretic karyotyping ; Aspergillus Section Flavi ; Chromosome length polymorphisms
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Contour-clamped homogeneous electric field gel electrophoresis was used to establish karyotypes for fungi of Aspergillus Section Flavi. Under identical electrophoretic conditions, five to eight chromosomal bands were separated in Aspergillus flavus isolates and five to seven chromosomal bands in A. parasiticus isolates. Each distinct chromosomal band contained one or more chromosomes. Other members of Aspergillus Section Flavi (A. oryzae, A. sojae, and A. tamarii) had similar karyotypes to those of A. flavus and A. parasiticus. A related species, A. versicolor, showed six chromosomal bands. With the exception of small chromosomes present in some isolates, the estimated sizes of chromosomes for all six species range from approximately 3.0 to ≥7.0 Mb. It is likely that all isolates of these species contain the same number of large (〉3 Mb) chromosomes; however, not all of the chromosomal bands could be resolved into separate chromosomes for each isolate due to chromosome length polymorphisms. This variability, observed in A. flavus and A. parasiticus, generated unique chromosomal band patterns within these species. The total genome sizes of these fungi were at least as large as those reported for A. nidulans and A. niger (31–38.5 Mb). Conserved genes were mapped to analogous chromosomes of A. flavus and A. parasiticus by gene hybridization.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00351697
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  • 8
    Electronic Resource
    Electronic Resource
    A peanut seed lipoxygenase responsive to Aspergillus colonization (2000)
    Springer
    Plant molecular biology 42 (2000), S. 689-701 
    Details
    ISSN: 1573-5028
    Keywords: Arachis hypogaea ; Aspergillus parasiticus ; lipoxygenase ; plant defense gene ; plant/microbe interaction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Several lines of evidence have indicated that lipoxygenase enzymes (LOX) and their products, especially 9S- and 13S-hydroperoxy fatty acids, could play a role in the Aspergillus/seed interaction. Both hydroperoxides exhibit sporogenic effects on Aspergillus spp. (Calvo, A., Hinze, L., Gardner, H.W. and Keller, N.P. 1999. Appl. Environ. Microbiol. 65: 3668–3673) and differentially modulate aflatoxin pathway gene transcription (Burow, G.B., Nesbitt, T.C., Dunlap, J. and Keller, N.P. 1997. Mol. Plant-Microbe Interact. 10: 380–387). To examine the role of seed LOXs at the molecular level, a peanut (Arachis hypogaea L.) seed gene, PnLOX1, was cloned and characterized. Analysis of nucleotide sequence suggests that PnLOX1 encodes a predicted 98 kDa protein highly similar in sequence and biochemical properties to soybean LOX2. The full-length PnLOX1 cDNA was subcloned into an expression vector to determine the type(s) of hydroperoxide products the enzyme produces. Analysis of the oxidation products of PnLOX1 revealed that it produced a mixture of 30% 9S-HPODE (9S-hydroperoxy-10E, 12Z-octadecadienoic acid) and 70% 13S-HPODE (13S-hydroperoxy-9Z, 11E-octadecadienoic acid) at pH 7. PnLOX1 is an organ-specific gene which is constitutively expressed in immature cotyledons but is highly induced by methyl jasmonate, wounding and Aspergillus infections in mature cotyledons. Examination of HPODE production in infected cotyledons suggests PnLOX1 expression may lead to an increase in 9S-HPODE in the seed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006361305703
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