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  • 1
    Electronic Resource
    Electronic Resource
    The gprA and gprB genes encode putative G protein-coupled receptors required for self-fertilization in Aspergillus nidulans (2004)
    Oxford, UK : Blackwell Science Ltd
    Molecular microbiology 53 (2004), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The filamentous fungus Aspergillus nidulans possesses both asexual and sexual reproductive cycles. Sexual fruiting bodies (cleistothecia) can be formed in both homothallic (self) and heterothallic (outcross) conditions. In this study, we characterized two genes, gprA and gprB, that are predicted to encode putative G protein-coupled receptors (GPCRs) similar to fungal pheromone receptors. Deletion (Δ) of gprA or gprB resulted in the production of a few small cleistothecia carrying a reduced number of ascospores, whereas ΔgprAΔgprB eliminated fruiting body formation in homothallic conditions. However, nullifying gprA and/or gprB did not affect vegetative growth, asexual sporulation, Hülle cell formation or even cleistothecia formation in outcross, indicating that GprA and GprB are specifically required for self-fertilization. The gprA and gprB genes encode two transcripts and, for both genes, larger transcripts are detectable during vegetative growth and asexual development whereas smaller transcripts accumulate during sexual development. Upregulation of nsdD encoding a key sexual developmental activator resulted in the production of barren cleistothecia in the ΔgprAΔgprB mutant, suggesting that NsdD can partially rescue the developmental defects caused by deletion of GPCRs and that GprA/B-mediated signalling may activate other genes necessary for maturation of cleistothecia and ascosporogenesis. Deletion of gprA and/or gprB suppressed growth defects caused by ΔgprD, implying that GprA/B function downstream of GprD-mediated negative control of sexual development.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.2004.04232.x
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  • 2
    Electronic Resource
    Electronic Resource
    REGULATION OF SECONDARY METABOLISM IN FILAMENTOUS FUNGI (2005)
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Phytopathology 43 (2005), S. 437-458 
    Details
    ISSN: 0066-4286
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Biology
    Notes: Fungal secondary metabolites are of intense interest to humankind due to their pharmaceutical (antibiotics) and/or toxic (mycotoxins) properties. In the past decade, tremendous progress has been made in understanding the genes that are associated with production of various fungal secondary metabolites. Moreover, the regulatory mechanisms controlling biosynthesis of diverse groups of secondary metabolites have been unveiled. In this review, we present the current understanding of the genetic regulation of secondary metabolism from clustering of biosynthetic genes to global regulators balancing growth, sporulation, and secondary metabolite production in selected fungi with emphasis on regulation of metabolites of agricultural concern. Particularly, the roles of G protein signaling components and developmental regulators in the mycotoxin sterigmatocystin biosynthesis in the model fungus Aspergillus nidulans are discussed in depth.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1146/annurev.phyto.43.040204.140214
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  • 3
    Electronic Resource
    Electronic Resource
    The nsdD gene encodes a putative GATA-type transcription factor necessary for sexual development of Aspergillus nidulans (2001)
    Oxford, UK : Blackwell Science Ltd
    Molecular microbiology 41 (2001), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The ability to reproduce both sexually and asexually is one of the characteristics of the homothalic ascomycete Aspergillus nidulans. Unlike the other Aspergillus species, A. nidulans undergoes sexual development that seems to be regulated by internal and external stimuli. To begin to understand the sexual reproduction of A. nidulans we previously isolated and characterized several NSD (never in sexual development) mutants that failed to produce any sexual reproductive organs, and identified four complementation groups, nsdA, nsdB, nsdC, and nsdD. The nsdD gene has been isolated, and it is predicted to encode a GATA-type transcription factor with the type IVb zinc finger DNA-binding domain. The mRNA of the nsdD gene started to accumulate in the early phase of vegetative growth, and the level increased as sexual development proceeded. However, it decreased during asexual sporulation and no nsdD mRNA was detected in conidia. Deletion of nsdD resulted in no cleistothecia (fruiting bodies) formation, even under the conditions that preferentially promoted sexual development, indicating that nsdD is necessary for sexual development. In contrast, when the nsdD gene was over-expressed, sexual-specific organ (Hülle cell) was formed even in submerged culture, which normally completely blocked sexual development, and the number of cleistothecia was also dramatically increased on solid medium. These results lead us to propose that the nsdD gene functions in activating sexual development of A. nidulans. Multiple copies of the nsdD gene could suppress nsdB5 and veA1, indicating that either nsdD acts downstream of these genes or possibly functions in overlapping pathway(s).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.2001.02472.x
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  • 4
    Electronic Resource
    Electronic Resource
    Regulators of G-protein signalling in Aspergillus nidulans: RgsA downregulates stress response and stimulates asexual sporulation through attenuation of GanB (Gα) signalling (2004)
    Oxford, UK : Blackwell Science Ltd
    Molecular microbiology 53 (2004), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Regulators of G-protein signalling play a crucial role in controlling the degree of heterotrimeric G-protein signalling. In addition to the previously studied flbA, we have identified three genes (rgsA, rgsB and rgsC) encoding putative RGS proteins in the genome of Aspergillus nidulans. Characterization of the rgsA gene revealed that RgsA downregulates pigment production and conidial germination, but stimulates asexual sporulation (conidiation). Deletion of rgsA (ΔrgsA) resulted in reduced colony size with increased aerial hyphae, elevated accumulation of brown pigments as well as enhanced tolerance of conidia and vegetative hyphae against oxidative and thermal stress. Moreover, ΔrgsA resulted in conidial germination in the absence of a carbon source. Deletion of both flbA and rgsA resulted in an additive phenotype, suggesting that the G-protein pathways controlled by FlbA and RgsA are different. Morphological and metabolic alterations caused by ΔrgsA were suppressed by deletion of ganB encoding a Gα subunit, indicating that the primary role of RgsA is to control negatively GanB-mediated signalling. Overexpression of rgsA caused inappropriate conidiation in liquid submerged culture, supporting the idea that GanB signalling represses conidiation. Our findings define a second and specific RGS–Gα pair in A. nidulans, which may govern upstream regulation of fungal cellular responses to environmental changes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.2004.04163.x
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  • 5
    Electronic Resource
    Electronic Resource
    A putative G protein-coupled receptor negatively controls sexual development in Aspergillus nidulans (2004)
    Oxford, UK : Blackwell Science Ltd
    Molecular microbiology 51 (2004), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: G protein-coupled receptors (GPCRs) are key components of heterotrimeric G protein-mediated signalling pathways that detect environmental signals and confer rapid cellular responses. To broaden our understanding of signalling mechanisms in the filamentous fungus Aspergillus nidulans, intensive analyses of the Aspergillus nidulans genome have been carried out and nine genes (gprA∼gprI) that are predicted to encode seven transmembrane spanning GPCRs have been identified. Six of nine putative GPCRs have been disrupted and the gprD gene was found to play a central role in coordinating hyphal growth and sexual development. Deletion of gprD (ΔgprD) causes extremely restricted hyphal growth, delayed conidial germination and uncontrolled activation of sexual development resulting in a small colony covered by sexual fruiting bodies. Genetic studies indicate that GprD may not signal through the FadA (Gα)-protein kinase A (PKA) pathway. Elimination of sexual development rescues both growth and developmental abnormalities caused by ΔgprD, suggesting that the primary role of GprD is to negatively regulate sexual development. This is supported by the fact that environmental conditions inhibiting sexual development suppress growth defects of the ΔgprD mutant. We propose that the GprD-mediated signalling cascade negatively regulates sexual development, which is required for proper proliferation of A. nidulans.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.2003.03940.x
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  • 6
    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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  • 7
    Electronic Resource
    Electronic Resource
    Dominant mutations affecting both sporulation and sterigmatocystin biosynthesis in Aspergillus nidulans (1997)
    Springer
    Current genetics 32 (1997), S. 218-224 
    Details
    ISSN: 1432-0983
    Keywords: Key words G proteins ; Transcription factor ; Sporulation ; Microbial development ; Mycotoxin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The initiation of conidiophore development in the filamentous fungus Aspergillus nidulans is a complex process requiring the activities of several genes including fluG, flbA, flbB, flbC, flbD, and flbE. Recessive mutations in any one of these genes result in greatly reduced expression of the brlA developmental regulatory gene and a colony morphology described as fluffy. These fluffy mutants have somewhat diverse phenotypes but generally grow as undifferentiated masses of vegetative hyphae to form large cotton-like colonies. In this paper we describe a genetic screen to identify dominant mutations resulting in similar fluffy colony morphologies. We have identified 36 dominant fluffy mutant strains and shown that 29 of these mutants have greatly reduced brlA expression as compared to wild-type. In addition, we have found that 19 of these mutants are not only developmentally altered but also fail to produce the toxic, carcinogenic, secondary metabolite sterigmatocystin. At least three of the mutants isolated result from dominant activating mutations in fadA which encodes the Gα subunit of a heterotrimeric G-protein. Another of the mutants results from a dominant interfering mutation in brlA. We discuss the approaches taken to characterize these potentially important regulators of growth, development and secondary metabolism.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002940050269
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