scholarly journals The 14-3-3 Protein Homolog ArtA Regulates Development and Secondary Metabolism in the Opportunistic Plant PathogenAspergillus flavus

2017 ◽  
Vol 84 (5) ◽  
Author(s):  
Beatriz A. Ibarra ◽  
Jessica M. Lohmar ◽  
Timothy Satterlee ◽  
Taylor McDonald ◽  
Jeffrey W. Cary ◽  
...  
Keyword(s):  
Secondary Metabolism ◽  
Aspergillus Flavus ◽  
Pathogenic Fungus ◽  
Cyclopiazonic Acid ◽  
Gene Clusters ◽  
Opportunistic Pathogen ◽  
Aflatoxin Contamination ◽  
Morphological Development ◽  
Dependent Manner ◽  
Content Type

ABSTRACTThe opportunistic plant-pathogenic fungusAspergillus flavusproduces carcinogenic mycotoxins termed aflatoxins (AF). Aflatoxin contamination of agriculturally important crops, such as maize, peanut, sorghum, and tree nuts, is responsible for serious adverse health and economic impacts worldwide. In order to identify possible genetic targets to reduce AF contamination, we have characterized theartAgene, encoding a putative 14-3-3 homolog inA. flavus. TheartAdeletion mutant presents a slight decrease in vegetative growth and alterations in morphological development and secondary metabolism. Specifically,artAaffects conidiation, and this effect is influenced by the type of substrate and culture condition. In addition, normal levels ofartAare required for sclerotial development. Importantly,artAnegatively regulates AF production as well as the concomitant expression of genes in the AF gene cluster. An increase in AF is also observed in seeds infected with theA. flavusstrain lackingartA. Furthermore, the expression of other secondary metabolite genes is alsoartAdependent, including genes in the cyclopiazonic acid (CPA) and ustiloxin gene clusters, in this agriculturally important fungus.IMPORTANCEIn the current study,artA, which encodes a 14-3-3 homolog, was characterized in the agriculturally and medically important fungusAspergillus flavus, specifically, its possible role governing sporulation, formation of resistant structures, and secondary metabolism. The highly conservedartAis necessary for normal fungal morphogenesis in an environment-dependent manner, affecting the balance between production of conidiophores and the formation of resistant structures that are necessary for the dissemination and survival of this opportunistic pathogen. This study reports a 14-3-3 protein affecting secondary metabolism in filamentous fungi. Importantly,artAregulates the biosynthesis of the potent carcinogenic compound aflatoxin B1 (AFB1) as well as the production of other secondary metabolites.

scholarly journals The Solvent Dimethyl Sulfoxide Affects Physiology, Transcriptome and Secondary Metabolism of Aspergillus flavus

2021 ◽  
Vol 7 (12) ◽  
pp. 1055
Author(s):  
Laura H. Costes ◽  
Yannick Lippi ◽  
Claire Naylies ◽  
Emilien L. Jamin ◽  
Clémence Genthon ◽  
...  
Keyword(s):  
Dimethyl Sulfoxide ◽  
Secondary Metabolism ◽  
Aspergillus Flavus ◽  
Biological Effects ◽  
Pathogenic Fungus ◽  
Fungal Growth ◽  
Cyclopiazonic Acid ◽  
Gene Clusters ◽  
Dependent Manner ◽  
Fold Reduction

Dimethyl sulfoxide (DSMO) is a simple molecule widely used because of its great solvating ability, but this solvent also has little-known biological effects, especially on fungi. Aspergillus flavus is a notorious pathogenic fungus which may contaminate a large variety of crops worldwide by producing aflatoxins, endangering at the same time food safety and international trade. The aim of this study was to characterize the effect of DMSO on A. flavus including developmental parameters such as germination and sporulation, as well as its transcriptome profile using high-throughput RNA-sequencing assay and its impact on secondary metabolism (SM). After DMSO exposure, A. flavus displayed depigmented conidia in a dose-dependent manner. The four-day exposition of cultures to two doses of DMSO, chosen on the basis of depigmentation intensity (35 mM “low” and 282 mM “high”), led to no significant impact on fungal growth, germination or sporulation. However, transcriptomic data analysis showed that 4891 genes were differentially regulated in response to DMSO (46% of studied transcripts). A total of 4650 genes were specifically regulated in response to the highest dose of DMSO, while only 19 genes were modulated upon exposure to the lowest dose. Secondary metabolites clusters genes were widely affected by the DMSO, with 91% of clusters impacted at the highest dose. Among these, aflatoxins, cyclopiazonic acid and ustiloxin B clusters were totally under-expressed. The genes belonging to the AFB1 cluster were the most negatively modulated ones, the two doses leading to 63% and 100% inhibition of the AFB1 production, respectively. The SM analysis also showed the disappearance of ustiloxin B and a 10-fold reduction of cyclopiazonic acid level when A. flavus was treated by the higher DMSO dose. In conclusion, the present study showed that DMSO impacted widely A. flavus’ transcriptome, including secondary metabolism gene clusters with the aflatoxins at the head of down-regulated ones. The solvent also inhibits conidial pigmentation, which could illustrate common regulatory mechanisms between aflatoxins and fungal pigment pathways. Because of its effect on major metabolites synthesis, DMSO should not be used as solvent especially in studies testing anti-aflatoxinogenic compounds.

scholarly journals Transcriptome Analysis of Aspergillus flavus RevealsveA-Dependent Regulation of Secondary Metabolite Gene Clusters, Including the Novel Aflavarin Cluster

2015 ◽  
Vol 14 (10) ◽  
pp. 983-997 ◽  
Author(s):  
J. W. Cary ◽  
Z. Han ◽  
Y. Yin ◽  
J. M. Lohmar ◽  
S. Shantappa ◽  
...  
Keyword(s):  
Secondary Metabolism ◽  
Secondary Metabolite ◽  
Aspergillus Flavus ◽  
Gene Clusters ◽  
Fungal Species ◽  
The Novel ◽  
Content Type ◽  
Expression Of Genes ◽  
Number Of Genes ◽  
Fungal Secondary Metabolism

ABSTRACTThe global regulatoryveAgene governs development and secondary metabolism in numerous fungal species, includingAspergillus flavus. This is especially relevant sinceA. flavusinfects crops of agricultural importance worldwide, contaminating them with potent mycotoxins. The most well-known are aflatoxins, which are cytotoxic and carcinogenic polyketide compounds. The production of aflatoxins and the expression of genes implicated in the production of these mycotoxins areveAdependent. The genes responsible for the synthesis of aflatoxins are clustered, a signature common for genes involved in fungal secondary metabolism. Studies of theA. flavusgenome revealed many gene clusters possibly connected to the synthesis of secondary metabolites. Many of these metabolites are still unknown, or the association between a known metabolite and a particular gene cluster has not yet been established. In the present transcriptome study, we show thatveAis necessary for the expression of a large number of genes. Twenty-eight out of the predicted 56 secondary metabolite gene clusters include at least one gene that is differentially expressed depending on presence or absence ofveA. One of the clusters under the influence ofveAis cluster 39. The absence ofveAresults in a downregulation of the five genes found within this cluster. Interestingly, our results indicate that the cluster is expressed mainly in sclerotia. Chemical analysis of sclerotial extracts revealed that cluster 39 is responsible for the production of aflavarin.

scholarly journals The kinetochore protein Spc105, a novel interaction partner of LaeA, regulates development and secondary metabolism in Aspergillus flavus

2018 ◽  
Author(s):  
QingQing Zhi ◽  
Lei He ◽  
JieYing Li ◽  
Jing Li ◽  
ZhenLong Wang ◽  
...  
Keyword(s):  
Secondary Metabolism ◽  
Aspergillus Flavus ◽  
Leucine Zipper ◽  
Cyclopiazonic Acid ◽  
Gene Clusters ◽  
Interaction Partner ◽  
Kinetochore Protein ◽  
Metabolism Regulation ◽  
Fungal Secondary Metabolism

Nuclear protein LaeA is known as the global regulator of secondary metabolism in Aspergillus. LaeA connects with VeA and VelB to form a heterotrimeric complex, which coordinates fungal development and secondary metabolism. Here, we describe a new interaction partner of LaeA, the kinetochore protein Spc105, from the aflatoxin-producing fungus Aspergillus flavus. We showed that in addition to involvement in nuclear division, Spc105 is required for normal conidiophore development and sclerotia production of A. flavus. Moreover, Spc105 positively regulates the production of secondary metabolites such as aflatoxin and kojic acid, and negatively regulates the production of cyclopiazonic acid. Transcriptome analysis of the ?spc105 strain revealed that 23 backbone genes were differentially expressed, corresponding to 19 of the predicted 56 secondary metabolite gene clusters, suggesting a broad regulatory role of Spc105 in secondary metabolism. Notably, the reduced expression of laeA in our transcriptome data led to the discovery of the correlation between Spc105 and LaeA, and double mutant analysis indicated a functional interdependence between Spc105 and LaeA. Further, yeast two-hybrid (Y2H) and GST pull-down assays revealed that Spc105 interacts directly with the S-adenosylmethionine (SAM)-binding domain of LaeA, and that the leucine zipper motif in Spc105 is required for this interaction. The Spc105-LaeA interaction identified in our study indicates a cooperative interplay of distinct regulators in A. flavus, providing new insights into fungal secondary metabolism regulation networks.

Modelling the colonisation of maize by toxigenic and non-toxigenic Aspergillus flavus strains: implications for biological control

2008 ◽  
Vol 1 (3) ◽  
pp. 333-340 ◽  
Author(s):  
H. Abbas ◽  
R. Zablotowicz ◽  
H. Bruns
Keyword(s):  
Biological Control ◽  
Aspergillus Flavus ◽  
Growth Parameters ◽  
Biological Control Agent ◽  
Cyclopiazonic Acid ◽  
Aflatoxin Contamination ◽  
Tween 20 ◽  
Lag Phase ◽  
Gompertz Equation ◽  
Aflatoxin Accumulation

To successfully exploit biological control it is desirable to understand how the introduced agent colonises the host and interferes with establishment of the pest. This study assessed field colonisation of maize by Aspergillus flavus strains as biological control agents to reduce aflatoxin contamination. Maize (corn, Zea mays L.) ears were inoculated with A. flavus using a pin-bar technique in 2004 and 2005. Non-aflatoxigenic strains K49 (NRRL 30797) & CT3 (NRRL 30798) and toxigenic F3W4 (NRRL 30798) were compared against a carrier control (0.2% aqueous Tween 20). Ten ears were sampled over 12 to 20 days, visually assessed, and curves fit to a three compartment Gompertz equation or other best appropriate regressions. Aflatoxin was determined by HPLC and cyclopiazonic acid (CPA) by LC/MS. The Gompertz model describes growth parameters, e.g. growth constant, lag phase and maximum colonisation characterised patterns of maize colonisation for most inoculated treatments. Aflatoxin accumulation in maize inoculated with F3W4 was about 35,000 ng/g in 2004 and 2005, with kinetics of aflatoxin accumulation in 2005 well described by the Gompertz equation. Less than 200 ng/g was observed in maize inoculated with strains CT3 & K49 and accumulation was described by a linear or logistic model. Maize inoculated with strains CT3 and F3W4 accumulated a maximum of 220 and 169 µg/kg CPA, respectively, compared to 22 and 0.2 µg/kg in the control and K49 inoculated, respectively. This technique can be used to elucidate colonisation potential of non-toxigenic A. flavus in maize in relation to biological control of aflatoxin. The greatest reduction of aflatoxin and CPA in maize inoculated with strain K49 and Gompertz parameters on colonisation indicates its superiority to CT3 as a biological control agent. The dynamics of maize colonisation by A. flavus strains and subsequent mycotoxin accumulation generated by using the pin-bar technique has implications for characterising the competence of biocontrol strains for reducing aflatoxin contamination.

scholarly journals Transcriptomic, Protein-DNA Interaction, and Metabolomic Studies of VosA, VelB, and WetA in Aspergillus nidulans Asexual Spores

mBio ◽  
2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Ming-Yueh Wu ◽  
Matthew E. Mead ◽  
Mi-Kyung Lee ◽  
George F. Neuhaus ◽  
Donovon A. Adpressa ◽  
...  
Keyword(s):  
Transcription Factors ◽  
Secondary Metabolism ◽  
Aspergillus Nidulans ◽  
Filamentous Fungi ◽  
Genetic Regulatory Networks ◽  
Asexual Development ◽  
Morphological Development ◽  
Vast Number ◽  
Content Type ◽  
Metabolic Remodeling

ABSTRACT In filamentous fungi, asexual development involves cellular differentiation and metabolic remodeling leading to the formation of intact asexual spores. The development of asexual spores (conidia) in Aspergillus is precisely coordinated by multiple transcription factors (TFs), including VosA, VelB, and WetA. Notably, these three TFs are essential for the structural and metabolic integrity, i.e., proper maturation, of conidia in the model fungus Aspergillus nidulans. To gain mechanistic insight into the complex regulatory and interdependent roles of these TFs in asexual sporogenesis, we carried out multi-omics studies on the transcriptome, protein-DNA interactions, and primary and secondary metabolism employing A. nidulans conidia. RNA sequencing and chromatin immunoprecipitation sequencing analyses have revealed that the three TFs directly or indirectly regulate the expression of genes associated with heterotrimeric G-protein signal transduction, mitogen-activated protein (MAP) kinases, spore wall formation and structural integrity, asexual development, and primary/secondary metabolism. In addition, metabolomics analyses of wild-type and individual mutant conidia indicate that these three TFs regulate a diverse array of primary metabolites, including those in the tricarboxylic acid (TCA) cycle, certain amino acids, and trehalose, and secondary metabolites such as sterigmatocystin, emericellamide, austinol, and dehydroaustinol. In summary, WetA, VosA, and VelB play interdependent, overlapping, and distinct roles in governing morphological development and primary/secondary metabolic remodeling in Aspergillus conidia, leading to the production of vital conidia suitable for fungal proliferation and dissemination. IMPORTANCE Filamentous fungi produce a vast number of asexual spores that act as efficient propagules. Due to their infectious and/or allergenic nature, fungal spores affect our daily life. Aspergillus species produce asexual spores called conidia; their formation involves morphological development and metabolic changes, and the associated regulatory systems are coordinated by multiple transcription factors (TFs). To understand the underlying global regulatory programs and cellular outcomes associated with conidium formation, genomic and metabolomic analyses were performed in the model fungus Aspergillus nidulans. Our results show that the fungus-specific WetA/VosA/VelB TFs govern the coordination of morphological and chemical developments during sporogenesis. The results of this study provide insights into the interdependent, overlapping, or distinct genetic regulatory networks necessary to produce intact asexual spores. The findings are relevant for other Aspergillus species such as the major human pathogen Aspergillus fumigatus and the aflatoxin producer Aspergillus flavus.

scholarly journals Vibrio gazogenes inhibits aflatoxin production through downregulation of aflatoxin biosynthetic genes in Aspergillus flavus

2022 ◽  
Author(s):  
Shyam L. Kandel ◽  
Rubaiya Jesmin ◽  
Brian M. Mack ◽  
Rajtilak Majumdar ◽  
Matthew K. Gilbert ◽  
...  
Keyword(s):  
Secondary Metabolites ◽  
Secondary Metabolite ◽  
Aspergillus Flavus ◽  
Fungal Biomass ◽  
Expression Profiles ◽  
Health Hazard ◽  
Gene Clusters ◽  
Aflatoxin Contamination ◽  
Aflatoxin Biosynthesis ◽  
Control Samples

Aspergillus flavus is an opportunistic pathogen of oilseed crops such as maize, peanut, cottonseed, and tree nuts and produces carcinogenic secondary metabolites known as aflatoxins during seed colonization. Aflatoxin contamination not only reduces the value of the produce but also is a health hazard to humans and animals. Previously, we observed inhibition of A. flavus aflatoxin biosynthesis upon exposure to the marine bacterium, Vibrio gazogenes (Vg). In this study, we used RNA sequencing to examine the transcriptional profiles of A. flavus treated with both live and heat-inactivated dead Vg and control samples. Fungal biomass, total accumulated aflatoxins, and expression profiles of genes constituting secondary metabolite biosynthetic gene clusters were determined at 24, 30, and 40 h after treatment. Statistically significant reductions in total aflatoxins were detected in Vg-treated samples as compared to control samples at 40 h. But no statistical difference in fungal biomass was observed upon these treatments. The Vg treatments were most effective on aflatoxin biosynthesis as was reflected in significant downregulation of majority of the genes in the aflatoxin gene cluster including the aflatoxin pathway regulator gene, aflR. Along with aflatoxin genes, we also observed significant downregulation in some other secondary metabolite gene clusters including cyclopiazonic acid and aflavarin, suggesting that the treatment may inhibit other secondary metabolites as well. Finally, a weighted gene correlation network analysis identified an upregulation of ten genes that were most strongly associated with Vg-dependent aflatoxin inhibition and provide a novel start-point in understanding the mechanisms that result in this phenomenon.

scholarly journals Diversity of Secondary Metabolism in Aspergillus nidulans Clinical Isolates

mSphere ◽  
2020 ◽  
Vol 5 (2) ◽  
Author(s):  
M. T. Drott ◽  
R. W. Bastos ◽  
A. Rokas ◽  
L. N. A. Ries ◽  
T. Gabaldón ◽  
...  
Keyword(s):  
Secondary Metabolism ◽  
Aspergillus Nidulans ◽  
Reference Genome ◽  
Genetic Model ◽  
High Resolution Mass Spectrometry ◽  
Gene Clusters ◽  
Clinical Isolates ◽  
Biosynthetic Gene ◽  
Content Type ◽  
Natural Diversity

ABSTRACT The filamentous fungus Aspergillus nidulans has been a primary workhorse used to understand fungal genetics. Much of this work has focused on elucidating the genetics of biosynthetic gene clusters (BGCs) and the secondary metabolites (SMs) they produce. SMs are both niche defining in fungi and of great economic importance to humans. Despite the focus on A. nidulans, very little is known about the natural diversity in secondary metabolism within this species. We determined the BGC content and looked for evolutionary patterns in BGCs from whole-genome sequences of two clinical isolates and the A4 reference genome of A. nidulans. Differences in BGC content were used to explain SM profiles determined using liquid chromatography–high-resolution mass spectrometry. We found that in addition to genetic variation of BGCs contained by all isolates, nine BGCs varied by presence/absence. We discovered the viridicatumtoxin BGC in A. nidulans and suggest that this BGC has undergone a horizontal gene transfer from the Aspergillus section Nigri lineage into Penicillium sometime after the sections Nigri and Nidulantes diverged. We identified the production of viridicatumtoxin and several other compounds previously not known to be produced by A. nidulans. One isolate showed a lack of sterigmatocystin production even though it contained an apparently intact sterigmatocystin BGC, raising questions about other genes and processes known to regulate this BGC. Altogether, our work uncovers a large degree of intraspecies diversity in BGC and SM production in this genetic model species and offers new avenues to understand the evolution and regulation of secondary metabolism. IMPORTANCE Much of what we know about the genetics underlying secondary metabolite (SM) production and the function of SMs in the model fungus Aspergillus nidulans comes from a single reference genome. A growing body of research indicates the importance of biosynthetic gene cluster (BGC) and SM diversity within a species. However, there is no information about the natural diversity of secondary metabolism in A. nidulans. We discovered six novel clusters that contribute to the considerable variation in both BGC content and SM production within A. nidulans. We characterize a diverse set of mutations and emphasize how findings of single nucleotide polymorphisms (SNPs), deletions, and differences in evolutionary history encompass much of the variation observed in nonmodel systems. Our results emphasize that A. nidulans may also be a strong model to use within-species diversity to elucidate regulatory cross talk, fungal ecology, and drug discovery systems.

scholarly journals The Frequency of Sex: Population Genomics Reveals Differences in Recombination and Population Structure of the Aflatoxin-Producing Fungus Aspergillus flavus

mBio ◽  
2020 ◽  
Vol 11 (4) ◽  
Author(s):  
Milton T. Drott ◽  
Tatum R. Satterlee ◽  
Jeffrey M. Skerker ◽  
Brandon T. Pfannenstiel ◽  
N. Louise Glass ◽  
...  
Keyword(s):  
Aspergillus Flavus ◽  
Population Genomics ◽  
Population Expansion ◽  
Aflatoxin Production ◽  
The United States ◽  
Aflatoxin Contamination ◽  
Deleterious Mutations ◽  
Content Type ◽  
Sexual And Asexual Reproduction ◽  
Potent Carcinogen

ABSTRACT The apparent rarity of sex in many fungal species has raised questions about how much sex is needed to purge deleterious mutations and how differences in frequency of sex impact fungal evolution. We sought to determine how differences in the extent of recombination between populations of Aspergillus flavus impact the evolution of genes associated with the synthesis of aflatoxin, a notoriously potent carcinogen. We sequenced the genomes of, and quantified aflatoxin production in, 94 isolates of A. flavus sampled from seven states in eastern and central latitudinal transects of the United States. The overall population is subdivided into three genetically differentiated populations (A, B, and C) that differ greatly in their extent of recombination, diversity, and aflatoxin-producing ability. Estimates of the number of recombination events and linkage disequilibrium decay suggest relatively frequent sex only in population A. Population B is sympatric with population A but produces significantly less aflatoxin and is the only population where the inability of nonaflatoxigenic isolates to produce aflatoxin was explained by multiple gene deletions. Population expansion evident in population B suggests a recent introduction or range expansion. Population C is largely nonaflatoxigenic and restricted mainly to northern sampling locations through restricted migration and/or selection. Despite differences in the number and type of mutations in the aflatoxin gene cluster, codon optimization and site frequency differences in synonymous and nonsynonymous mutations suggest that low levels of recombination in some A. flavus populations are sufficient to purge deleterious mutations. IMPORTANCE Differences in the relative frequencies of sexual and asexual reproduction have profound implications for the accumulation of deleterious mutations (Muller’s ratchet), but little is known about how these differences impact the evolution of ecologically important phenotypes. Aspergillus flavus is the main producer of aflatoxin, a notoriously potent carcinogen that often contaminates food. We investigated if differences in the levels of production of aflatoxin by A. flavus could be explained by the accumulation of deleterious mutations due to a lack of recombination. Despite differences in the extent of recombination, variation in aflatoxin production is better explained by the demography and history of specific populations and may suggest important differences in the ecological roles of aflatoxin among populations. Furthermore, the association of aflatoxin production and populations provides a means of predicting the risk of aflatoxin contamination by determining the frequencies of isolates from low- and high-production populations.

scholarly journals Characterizing the Pathogenic, Genomic, and Chemical Traits ofAspergillus fischeri, a Close Relative of the Major Human Fungal PathogenAspergillus fumigatus

mSphere ◽  
2019 ◽  
Vol 4 (1) ◽  
Author(s):  
Matthew E. Mead ◽  
Sonja L. Knowles ◽  
Huzefa A. Raja ◽  
Sarah R. Beattie ◽  
Caitlin H. Kowalski ◽  
...  
Keyword(s):  
Secondary Metabolites ◽  
Aspergillus Fumigatus ◽  
Secondary Metabolism ◽  
Human Disease ◽  
Chemical Characterization ◽  
Gene Clusters ◽  
Invasive Disease ◽  
Close Relative ◽  
Low Oxygen ◽  
Content Type

ABSTRACTAspergillus fischeriis closely related toAspergillus fumigatus, the major cause of invasive mold infections. Even thoughA. fischeriis commonly found in diverse environments, including hospitals, it rarely causes invasive disease. WhyA. fischericauses less human disease thanA. fumigatusis unclear. A comparison ofA. fischeriandA. fumigatusfor pathogenic, genomic, and secondary metabolic traits revealed multiple differences in pathogenesis-related phenotypes. We observed thatA. fischeriNRRL 181 is less virulent thanA. fumigatusstrain CEA10 in multiple animal models of disease, grows slower in low-oxygen environments, and is more sensitive to oxidative stress. Strikingly, the observed differences for some traits are of the same order of magnitude as those previously reported betweenA. fumigatusstrains. In contrast, similar to what has previously been reported, the two species exhibit high genomic similarity; ∼90% of theA. fumigatusproteome is conserved inA. fischeri, including 48/49 genes known to be involved inA. fumigatusvirulence. However, only 10/33A. fumigatusbiosynthetic gene clusters (BGCs) likely involved in secondary metabolite production are conserved inA. fischeriand only 13/48A. fischeriBGCs are conserved inA. fumigatus. Detailed chemical characterization ofA. fischericultures grown on multiple substrates identified multiple secondary metabolites, including two new compounds and one never before isolated as a natural product. Additionally, anA. fischerideletion mutant oflaeA, a master regulator of secondary metabolism, produced fewer secondary metabolites and in lower quantities, suggesting that regulation of secondary metabolism is at least partially conserved. These results suggest that the nonpathogenicA. fischeripossesses many of the genes important forA. fumigatuspathogenicity but is divergent with respect to its ability to thrive under host-relevant conditions and its secondary metabolism.IMPORTANCEAspergillus fumigatusis the primary cause of aspergillosis, a devastating ensemble of diseases associated with severe morbidity and mortality worldwide.A. fischeriis a close relative ofA. fumigatusbut is not generally observed to cause human disease. To gain insights into the underlying causes of this remarkable difference in pathogenicity, we compared two representative strains (one from each species) for a range of pathogenesis-relevant biological and chemical characteristics. We found that disease progression in multipleA. fischerimouse models was slower and caused less mortality thanA. fumigatus. Remarkably, the observed differences betweenA. fischeriandA. fumigatusstrains examined here closely resembled those previously described for two commonly studiedA. fumigatusstrains, AF293 and CEA10.A. fischeriandA. fumigatusexhibited different growth profiles when placed in a range of stress-inducing conditions encountered during infection, such as low levels of oxygen and the presence of chemicals that induce the production of reactive oxygen species. We also found that the vast majority ofA. fumigatusgenes known to be involved in virulence are conserved inA. fischeri, whereas the two species differ significantly in their secondary metabolic pathways. These similarities and differences that we report here are the first step toward understanding the evolutionary origin of a major fungal pathogen.

scholarly journals The Streptomyces filipinensis Gamma-Butyrolactone System Reveals Novel Clues for Understanding the Control of Secondary Metabolism

2020 ◽  
Vol 86 (18) ◽  
Author(s):  
Eva G. Barreales ◽  
Tamara D. Payero ◽  
Ester Jambrina ◽  
Jesús F. Aparicio
Keyword(s):  
Quorum Sensing ◽  
Secondary Metabolism ◽  
Target Genes ◽  
Antibiotic Production ◽  
The Other ◽  
Antimycin A ◽  
Dependent Manner ◽  
Biosynthetic Genes ◽  
Content Type ◽  
Communication Signals

ABSTRACT Streptomyces γ-butyrolactones (GBLs) are quorum sensing communication signals triggering antibiotic production. The GBL system of Streptomyces filipinensis, the producer of the antifungal agent filipin, has been investigated. Inactivation of sfbR (for S. filipinensis γ-butyrolactone receptor), a GBL receptor, resulted in a strong decrease in production of filipin, and deletion of sfbR2, a pseudo-receptor, boosted it, in agreement with lower and higher levels of transcription of filipin biosynthetic genes, respectively. It is noteworthy that none of the mutations affected growth or morphological development. While no ARE (autoregulatory element)-like sequences were found in the promoters of filipin genes, suggesting indirect control of production, five ARE sequences were found in five genes of the GBL cluster, whose transcription has been shown to be controlled by both S. filipinensis SfbR and SfbR2. In vitro binding of recombinant SfbR and SfbR2 to such sequences indicated that such control is direct. Transcription start points were identified by 5′ rapid amplification of cDNA ends, and precise binding regions were investigated by the use of DNase I protection studies. Binding of both regulators took place in the promoter of target genes and at the same sites. Information content analysis of protected sequences in target promoters yielded an 18-nucleotide consensus ARE sequence. Quantitative transcriptional analyses revealed that both regulators are self-regulated and that each represses the transcription of the other as well as that of the remaining target genes. Unlike other GBL receptor homologues, SfbR activates its own transcription whereas SfbR2 has a canonical autorepression profile. Additionally, SfbR2 was found here to bind the antifungal antimycin A as a way to modulate its DNA-binding activity. IMPORTANCE Streptomyces GBLs are important signaling molecules that trigger antibiotic production in a quorum sensing-dependent manner. We have characterized the GBL system from S. filipinensis, finding that two key players of this system, the GBL receptor and the pseudo-receptor, each counteracts the transcription of the other for the modulation of filipin production and that such control over antifungal production involves an indirect effect on the transcription of filipin biosynthetic genes. Additionally, the two regulators bind the same sites, are self-regulated, and repress the transcription of three other genes of the GBL cluster, including that encoding the GBL synthase. In contrast to all the GBL receptors known, SfbR activates its own synthesis. Moreover, the pseudo-receptor was identified as the receptor of antimycin A, thus extending the range of examples supporting the idea of signaling effects of antibiotics in Streptomyces. The intricate regulatory network depicted here should provide important clues for understanding the regulatory mechanism governing secondary metabolism.

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