12 Asexual Sporulation in Agaricomycetes

2016 ◽  
pp. 269-328 ◽  
Author(s):  
Ursula Kües ◽  
Susanna M. Badalyan ◽  
Alexander Gießler ◽  
Bastian Dörnte
Keyword(s):  
Asexual Sporulation

scholarly journals Suppressor Mutations Bypass the Requirement of fluG for Asexual Sporulation and Sterigmatocystin Production in Aspergillus nidulans

Genetics ◽  
2003 ◽  
Vol 165 (3) ◽  
pp. 1083-1093
Author(s):  
Jeong-Ah Seo ◽  
Yajun Guan ◽  
Jae-Hyuk Yu
Keyword(s):  
Aspergillus Nidulans ◽  
Molecular Mechanisms ◽  
Dominant Negative ◽  
Wild Type ◽  
Dominant Mutation ◽  
Site Mutation ◽  
Asexual Sporulation ◽  
Dominant Negative Mutation ◽  
Suppressor Mutations ◽  
Early Developmental

Abstract Asexual sporulation (conidiation) in the filamentous fungus Aspergillus nidulans requires the early developmental activator fluG. Loss of fluG results in the blockage of both conidiation and production of the mycotoxin sterigmatocystin (ST). To investigate molecular mechanisms of fluG-dependent developmental activation, 40 suppressors of fluG (SFGs) that conidiate without fluG have been isolated and characterized. Genetic analyses showed that an individual suppression is caused by a single second-site mutation, and that all sfg mutations but one are recessive. Pairwise meiotic crosses grouped mutations to four loci, 31 of them to sfgA, 6 of them to sfgB, and 1 each to sfgC and sfgD, respectively. The only dominant mutation, sfgA38, also mapped to the sfgA locus, suggesting a dominant negative mutation. Thirteen sfgA and 1 sfgC mutants elaborated conidiophores in liquid submerged culture, indicating that loss of either of these gene functions not only bypasses fluG function but also results in hyperactive conidiation. While sfg mutants show varying levels of restored conidiation, all recovered the ability to produce ST at near wild-type levels. The fact that at least four loci are defined by recessive sfg mutations indicates that multiple genes negatively regulate conidiation downstream of fluG and that the activity of fluG is required to remove such repressive effects.

Characterization of the Role of the FluG Protein in Asexual Development of Aspergillus nidulans

Genetics ◽  
2001 ◽  
Vol 158 (3) ◽  
pp. 1027-1036 ◽  
Author(s):  
Cletus A D'Souza ◽  
Bee Na Lee ◽  
Thomas H Adams
Keyword(s):  
Aspergillus Nidulans ◽  
Negative Influence ◽  
Asexual Development ◽  
Wild Type ◽  
Significant Similarity ◽  
Developmental Defects ◽  
Asexual Sporulation ◽  
Type Strains

Abstract We showed previously that a ΔfluG mutation results in a block in Aspergillus nidulans asexual sporulation and that overexpression of fluG activates sporulation in liquid-submerged culture, a condition that does not normally support sporulation of wild-type strains. Here we demonstrate that the entire N-terminal region of FluG (∼400 amino acids) can be deleted without affecting sporulation, indicating that FluG activity resides in the C-terminal half of the protein, which bears significant similarity with GSI-type glutamine synthetases. While FluG has no apparent role in glutamine biosynthesis, we propose that it has an enzymatic role in sporulation factor production. We also describe the isolation of dominant suppressors of ΔfluG(dsg) that should identify components acting downstream of FluG and thereby define the function of FluG in sporulation. The dsgA1 mutation also suppresses the developmental defects resulting from ΔflbA and dominant activating fadA mutations, which both cause constitutive induction of the mycelial proliferation pathway. However, dsgA1 does not suppress the negative influence of these mutations on production of the aflatoxin precursor, sterigmatocystin, indicating that dsgA1 is specific for asexual development. Taken together, our studies define dsgA as a novel component of the asexual sporulation pathway.

scholarly journals Systematic Dissection of the Evolutionarily Conserved WetA Developmental Regulator across a Genus of Filamentous Fungi

mBio ◽  
2018 ◽  
Vol 9 (4) ◽  
Author(s):  
Ming-Yueh Wu ◽  
Matthew E. Mead ◽  
Mi-Kyung Lee ◽  
Erin M. Ostrem Loss ◽  
Sun-Chang Kim ◽  
...  
Keyword(s):  
Gene Regulatory Network ◽  
Filamentous Fungi ◽  
Negative Feedback ◽  
Regulatory Network ◽  
Feedback Loop ◽  
Spore Formation ◽  
Negative Feedback Loop ◽  
Content Type ◽  
Asexual Sporulation ◽  
Gene Regulatory

ABSTRACTAsexual sporulation is fundamental to the ecology and lifestyle of filamentous fungi and can facilitate both plant and human infection. InAspergillus, the production of asexual spores is primarily governed by the BrlA→AbaA→WetA regulatory cascade. The final step in this cascade is controlled by the WetA protein and governs not only the morphological differentiation of spores but also the production and deposition of diverse metabolites into spores. While WetA is conserved across the genusAspergillus, the structure and degree of conservation of thewetAgene regulatory network (GRN) remain largely unknown. We carried out comparative transcriptome analyses of comparisons betweenwetAnull mutant and wild-type asexual spores in three representative species spanning the diversity of the genusAspergillus:A. nidulans,A. flavus, andA. fumigatus. We discovered that WetA regulates asexual sporulation in all three species via a negative-feedback loop that represses BrlA, the cascade’s first step. Furthermore, data from chromatin immunoprecipitation sequencing (ChIP-seq) experiments inA. nidulansasexual spores suggest that WetA is a DNA-binding protein that interacts with a novel regulatory motif. Several global regulators known to bridge spore production and the production of secondary metabolites show species-specific regulatory patterns in our data. These results suggest that the BrlA→AbaA→WetA cascade’s regulatory role in cellular and chemical asexual spore development is functionally conserved but that thewetA-associated GRN has diverged duringAspergillusevolution.IMPORTANCEThe formation of resilient spores is a key factor contributing to the survival and fitness of many microorganisms, including fungi. In the fungal genusAspergillus, spore formation is controlled by a complex gene regulatory network that also impacts a variety of other processes, including secondary metabolism. To gain mechanistic insights into how fungal spore formation is controlled acrossAspergillus, we dissected the gene regulatory network downstream of a major regulator of spore maturation (WetA) in three species that span the diversity of the genus: the genetic modelA. nidulans, the human pathogenA. fumigatus, and the aflatoxin producerA. flavus. Our data show that WetA regulates asexual sporulation in all three species via a negative-feedback loop and likely binds a novel regulatory element that we term the WetA response element (WRE). These results shed light on how gene regulatory networks in microorganisms control important biological processes and evolve across diverse species.

scholarly journals The Putative APSES Transcription Factor RgdA Governs Growth, Development, Toxigenesis, and Virulence in Aspergillus fumigatus

mSphere ◽  
2020 ◽  
Vol 5 (6) ◽  
Author(s):  
Sang-Cheol Jun ◽  
Yong-Ho Choi ◽  
Min-Woo Lee ◽  
Jae-Hyuk Yu ◽  
Kwang-Soo Shin
Keyword(s):  
Transcription Factor ◽  
Aspergillus Fumigatus ◽  
Molecular Mechanisms ◽  
Pathogenic Fungus ◽  
Mrna Levels ◽  
Transcript Levels ◽  
Content Type ◽  
Asexual Sporulation ◽  
Human Pathogenic Fungus ◽  
Growth Development

ABSTRACT The APSES transcription factor (TF) in Aspergillus species is known to govern diverse cellular processes, including growth, development, and secondary metabolism. Here, we investigated functions of the rgdA gene (Afu3g13920) encoding a putative APSES TF in the opportunistic human-pathogenic fungus Aspergillus fumigatus. The rgdA deletion resulted in significantly decreased hyphal growth and asexual sporulation. Consistently, transcript levels of the key asexual developmental regulators abaA, brlA, and wetA were decreased in the ΔrgdA mutant compared to those in the wild type (WT). Moreover, ΔrgdA resulted in reduced spore germination rates and elevated transcript levels of genes associated with conidium dormancy. The conidial cell wall hydrophobicity and architecture were changed, and levels of the RodA protein were decreased in the ΔrgdA mutant. Comparative transcriptomic analyses revealed that the ΔrgdA mutant showed higher mRNA levels of gliotoxin (GT)-biosynthetic genes and GT production. While the ΔrgdA mutant exhibited elevated production of GT, ΔrgdA strains showed reduced virulence in the mouse model. In addition, mRNA levels of genes associated with the cyclic AMP (cAMP)-protein kinase A (PKA) signaling pathway and the SakA mitogen-activated protein (MAP) kinase pathway were increased in the ΔrgdA mutant. In summary, RgdA plays multiple roles in governing growth, development, GT production, and virulence which may involve attenuation of PKA and SakA signaling. IMPORTANCE Immunocompromised patients are susceptible to infections with the opportunistic human-pathogenic fungus Aspergillus fumigatus. This fungus causes systemic infections such as invasive aspergillosis (IA), which is one of the most life-threatening fungal diseases. To control this serious disease, it is critical to identify new antifungal drug targets. In fungi, the transcriptional regulatory proteins of the APSES family play crucial roles in controlling various biological processes, including mating, asexual sporulation and dimorphic growth, and virulence traits. This study found that a putative APSES transcription factor, RgdA, regulates normal growth, asexual development, conidium germination, spore wall architecture and hydrophobicity, toxin production, and virulence in A. fumigatus. Better understanding the molecular mechanisms of RgdA in human-pathogenic fungi may reveal a novel antifungal target for future drug development.

Asexual Sporulation in the Oomycetes

1997 ◽  
pp. 353-398 ◽  
Author(s):  
A.R. Hardham ◽  
G.J. Hyde
Keyword(s):  
Asexual Sporulation

scholarly journals Aspergillus Volatiles Regulate Aflatoxin Synthesis and Asexual Sporulation in Aspergillus parasiticus

2007 ◽  
Vol 73 (22) ◽  
pp. 7268-7276 ◽  
Author(s):  
Ludmila V. Roze ◽  
Randolph M. Beaudry ◽  
Anna E. Arthur ◽  
Ana M. Calvo ◽  
John E. Linz
Keyword(s):  
Aspergillus Parasiticus ◽  
Primary Source ◽  
Aflatoxin Contamination ◽  
Aflatoxin Biosynthesis ◽  
Transcript Accumulation ◽  
Potential Health ◽  
Asexual Sporulation ◽  
Norsolorinic Acid ◽  
Aflatoxin Accumulation ◽  
Regulatory Effects

ABSTRACT Aspergillus parasiticus is one primary source of aflatoxin contamination in economically important crops. To prevent the potential health and economic impacts of aflatoxin contamination, our goal is to develop practical strategies to reduce aflatoxin synthesis on susceptible crops. One focus is to identify biological and environmental factors that regulate aflatoxin synthesis and to manipulate these factors to control aflatoxin biosynthesis in the field or during crop storage. In the current study, we analyzed the effects of aspergillus volatiles on growth, development, aflatoxin biosynthesis, and promoter activity in the filamentous fungus A. parasiticus. When colonies of Aspergillus nidulans and A. parasiticus were incubated in the same growth chamber, we observed a significant reduction in aflatoxin synthesis and asexual sporulation by A. parasiticus. Analysis of the headspace gases demonstrated that A. nidulans produced much larger quantities of 2-buten-1-ol (CA) and 2-ethyl-1-hexanol (EH) than A. parasiticus. In its pure form, EH inhibited growth and increased aflatoxin accumulation in A. parasiticus at all doses tested; EH also stimulated aflatoxin transcript accumulation. In contrast, CA exerted dose-dependent up-regulatory or down-regulatory effects on aflatoxin accumulation, conidiation, and aflatoxin transcript accumulation. Experiments with reporter strains carrying nor-1 promoter deletions and mutations suggested that the differential effects of CA were mediated through separate regulatory regions in the nor-1 promoter. The potential efficacy of CA as a tool for analysis of transcriptional regulation of aflatoxin biosynthesis is discussed. We also identify a novel, rapid, and reliable method to assess norsolorinic acid accumulation in solid culture using a Chroma Meter CR-300 apparatus.

scholarly journals Asexual Sporulation in Aspergillus nidulans

1998 ◽  
Vol 62 (1) ◽  
pp. 35-54 ◽  
Author(s):  
Thomas H. Adams ◽  
Jenny K. Wieser ◽  
Jae-Hyuk Yu
Keyword(s):  
Life Cycle ◽  
Aspergillus Nidulans ◽  
Reproductive Mode ◽  
Fungal Species ◽  
Intrinsic Signals ◽  
Regulatory Interactions ◽  
Asexual Sporulation ◽  
Extracellular Signal ◽  
Sporulation Initiation ◽  
Fungal Life Cycle

SUMMARY The formation of mitotically derived spores, called conidia, is a common reproductive mode in filamentous fungi, particularly among the large fungal class Ascomycetes. Asexual sporulation strategies are nearly as varied as fungal species; however, the formation of conidiophores, specialized multicellular reproductive structures, by the filamentous fungus Aspergillus nidulans has emerged as the leading model for understanding the mechanisms that control fungal sporulation. Initiation of A. nidulans conidipohore formation can occur either as a programmed event in the life cycle in response to intrinsic signals or to environmental stresses such as nutrient deprivation. In either case, a development-specific set of transcription factors is activated and these control the expression of each other as well as genes required for conidiophore morphogenesis. Recent progress has identified many of the earliest-acting genes needed for initiating conidiophore development and shown that there are at least two antagonistic signaling pathways that control this process. One pathway is modulated by a heterotrimeric G protein that when activated stimulates growth and represses both asexual and sexual sporulation as well as production of the toxic secondary metabolite, sterigmatocystin. The second pathway apparently requires an extracellular signal to induce sporulation-specific events and to direct the inactivation of the first pathway, removing developmental repression. A working model is presented in which the regulatory interactions between these two pathways during the fungal life cycle determine whether cells grow or develop.

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