Degeneration of aflatoxin gene clusters in Aspergillus flavus
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PROVIDER: PRJEB11911 | ENA |
REPOSITORIES: ENA
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Project description:The molecular mechanisms underlying aflatoxin production have been well-studied in strains of the fungus Aspergillus flavus (A. flavus) under artificial conditions. However, aflatoxin biosynthesis has rarely been studied in natural isolates of A. flavus strains. In the present study, tandem mass tag (TMT) labeling and high-performance liquid chromatography (HPLC) coupled with tandem-mass spectrometry analysiswere used for proteomic quantification in natural isolates of high- and low-aflatoxin-yield A. flavus strains.
2022-02-17 | PXD027517 | Pride
Project description:Aspergillus flavus is the major producer of carcinogenic aflatoxins in crops worldwide. Natural populations of A. flavus show tremendous variation in aflatoxin production some of which can be attributed to extreme environmental conditions (e.g., drought), differential regulation of the aflatoxin biosynthetic pathway, missing cluster genes or loss-of-function mutations. Understanding the evolutionary processes that generate genetic diversity in A. flavus may also explain quantitative and qualitative differences in aflatoxigenicity. Several population studies provide indirect evidence of recombination in the aflatoxin gene cluster and genome-wide, using multilocus genealogical approaches. More recently A. flavus has been shown to be functionally heterothallic and capable of sexual reproduction in laboratory crosses. In the present study, we characterize the progeny from nine A. flavus crosses and show that crossovers in the aflatoxin cluster coincide with inferred recombination blocks and hotspots in natural populations, which suggests that recombination in the cluster is primarily driven by sex. Moreover, we show that a single crossover event in the cluster can restore aflatoxigenicity, which is significant as mycotoxin production in A. flavus is highly heritable. aCGH was used to corroborate inferences from cluster-based MLSTs and to possibly identify additional crosovers within the cluster.
2012-03-07 | GSE27484 | GEO
Project description:Aflatoxins are carcinogenic fungal secondary metabolites. Levels of aflatoxins in agricultural commodities are stringently regulated by many countries. A cluster of genes is responsible for aflatoxin biosynthesis by Aspergillus flavus and other closely related species. Expression of the clustered aflatoxin genes is governed by a complex network of regulatory mechanisms. To better understand the molecular events that are associated with aflatoxin production, transcription profiling by microarray analyses which compared three independent aflatoxigenic A. flavus strains to individual isogenic progenies that no longer produced aflatoxins after serial transfers was carried out. Twenty-two significantly differentially expressed features were identified. After physical mapping using the A. oryzae genome sequence as the reference, the number of unique genes was reduced to 16. Compared to the parental strains, changes in the aflatoxin gene expression levels in the progenies were not significant, which suggests that the inability to produce aflatoxins is not caused by decreased expression. The only gene showing higher expression levels in the progenies is homologous to glutathione S-transferease genes. Overexpression of this gene, named hcc, at six- to nine-fold in an aflatoxigenic A. flavus did not cause discernible changes in colony morphology or aflatoxin production. Loss of aflatoxin production after serial transfers may not result from a single event but caused by multiple factors. Keywords: Compartiave hybridization toxigenic and atoxigenic lines of Aspergillus
2008-06-18 | GSE8185 | GEO
Project description:Aflatoxins are carcinogenic fungal secondary metabolites. Levels of aflatoxins in agricultural commodities are stringently regulated by many countries. A cluster of genes is responsible for aflatoxin biosynthesis by Aspergillus flavus and other closely related species. Expression of the clustered aflatoxin genes is governed by a complex network of regulatory mechanisms. To better understand the molecular events that are associated with aflatoxin production, transcription profiling by microarray analyses which compared three independent aflatoxigenic A. flavus strains to individual isogenic progenies that no longer produced aflatoxins after serial transfers was carried out. Twenty-two significantly differentially expressed features were identified. After physical mapping using the A. oryzae genome sequence as the reference, the number of unique genes was reduced to 16. Compared to the parental strains, changes in the aflatoxin gene expression levels in the progenies were not significant, which suggests that the inability to produce aflatoxins is not caused by decreased expression. The only gene showing higher expression levels in the progenies is homologous to glutathione S-transferease genes. Overexpression of this gene, named hcc, at six- to nine-fold in an aflatoxigenic A. flavus did not cause discernible changes in colony morphology or aflatoxin production. Loss of aflatoxin production after serial transfers may not result from a single event but caused by multiple factors. Keywords: Compartiave hybridization toxigenic and atoxigenic lines of Aspergillus Aspergillus flavus NRRL 29459, NRRL 29474, and NRRL 29490 are aflatoxigenic strains originated from soil collection in a peanut field (Terrell Co., Georgia, USA). Strains 459B-20-2, 474A-20, and 499A-20 were nonaflatoxigenic isolates obtained after 20 serial transfers of the parental strains on potato dextrose agar slants (Horn and Dorner 2002). Comparsions in each experiment consisted of one aflatoxigenic parental strain and one nonaflatoxigenic progeny, compared after 48- or 72-hr growth. Each comparison was repeated with duplicate dye-flip.
2010-05-26 | E-GEOD-8185 | biostudies-arrayexpress
Project description:Aspergillus flavus is the major producer of carcinogenic aflatoxins in crops worldwide. Natural populations of A. flavus show tremendous variation in aflatoxin production some of which can be attributed to extreme environmental conditions (e.g., drought), differential regulation of the aflatoxin biosynthetic pathway, missing cluster genes or loss-of-function mutations. Understanding the evolutionary processes that generate genetic diversity in A. flavus may also explain quantitative and qualitative differences in aflatoxigenicity. Several population studies provide indirect evidence of recombination in the aflatoxin gene cluster and genome-wide, using multilocus genealogical approaches. More recently A. flavus has been shown to be functionally heterothallic and capable of sexual reproduction in laboratory crosses. In the present study, we characterize the progeny from nine A. flavus crosses and show that crossovers in the aflatoxin cluster coincide with inferred recombination blocks and hotspots in natural populations, which suggests that recombination in the cluster is primarily driven by sex. Moreover, we show that a single crossover event in the cluster can restore aflatoxigenicity, which is significant as mycotoxin production in A. flavus is highly heritable. aCGH was used to corroborate inferences from cluster-based MLSTs and to possibly identify additional crosovers within the cluster. aCGH comparison between 3 strains of A. flavus: 2 parental (P) and 1 progeny (F1) analyzed at the probe level. A total of 9 trio comparisons were made from a total of 18 isolates analyzed by aCGH. Trio comparisons are as follows: IC278 (P), IC1179 (P) and IC1650 (F1); IC201 (P), IC310 (P) and IC1719 (F1); IC307 (P), IC308 (P) and IC1751 (F1); IC277 (P), IC311 (P) and IC1766 (F1); IC277 (P), IC311 (P) and IC1775 (F1); IC244 (P), IC277 (P) and IC2205 (F1); IC244 (P), IC277 (P) and IC2207 (F1); IC301 (P), IC1179 (P) and IC2171 (F1); and finally IC244 (P), IC277 (P) and IC2209 (F1).
2012-03-07 | E-GEOD-27484 | biostudies-arrayexpress
Project description:Aspergillus flavus contaminates crops during preharvest and post-harvest periods and produce carcinogenic mycotoxin aflatoxins posing severe threat to food safety and human health. Lysine 2-hydroxyisobutyrylation is one of the most important reversible post-translational modifications and plays a vital regulatory role in various cellular processes. In order to explore the potential roles of lysine 2-hydroxyisobutyrylation in aflatoxin biosynthesis, protein 2-hydroxyisobutyrylation analysis of A. flavus was performed, and a total of 7156 2-hydroxyisobutyrylation sites in 1473 proteins were identified.
2022-06-06 | PXD030912 | Pride
Project description:Aspergillus flavus is a pathogen of corn, peanut, and other crops which produces carcinogenic mycotoxins known as aflatoxins. Previous studies have shown that drought stress results in exacerbated aflatoxin production. Drought-associated oxidative stress caused by reactive oxygen species (ROS) is suspected to contribute to increased aflatoxin production during infection. Here, the responses of field isolates of A. flavus with varying degrees of aflatoxin production capability to H2O2-derived oxidative stress were examined using iTRAQ proteomics. Three isolates: AF13 (highly toxigenic), NRRL3357 (moderately toxigenic), and K54A (atoxigenic), were cultures in aflatoxin conducive yeast extract-sucrose (YES) medium amended with 0, 10, or 20/25mM of H2O2. Identified differentially expressed proteins were used for functional prediction, cellular localization, and pathway analyses to identify molecular mechanisms involved in A. flavus oxidative stress responses relative to aflatoxin production capability. Correlative analyses with previously obtained transcriptome data for the same isolates under the same experimental conditions was also performed with a low degree of correlation (r = 0.1114) observed between the protein and transcript data suggesting possible post-transcriptional regulation of oxidative stress responses. The identified stress responsive mechanisms provide a basis of investigating novel approaches of enhancing host resistance against aflatoxin contamination.
2018-02-27 | PXD007164 | Pride
Project description:Diverse expression patterns for secondary metabolism gene clusters from Aspergillus flavus under different environmental conditions and in genetic mutants: Insights into regulation of cyclopiazonic acid along with aflatoxin Species of Aspergillus produce a diverse array of secondary metabolites, and recent genomic analysis predicts that these species have the capacity to synthesize many more compounds. It has been possible to infer the presence of 55 gene clusters associated with secondary metabolism in A. flavus. Presumably, secondary metabolites play important roles in the ecology of the producing species, but functions for most secondary metabolites remain unknown. Only three metabolic pathways have been associated with the predicted clusters in A. flavus. These include aflatoxin, cyclopiazonic acid (CPA), and aflatrem. To gain insight into the regulation of, and infer ecological significance for the 55 secondary metabolite gene clusters predicted in A. flavus, we examined their expression over 28 diverse conditions. Variables included culture media and temperature, fungal development, colonization of developing maize seeds, and misexpression of laeA, the global regulator of secondary metabolism. Hierarchical clustering analysis of expression profiles allowed us to categorize the gene clusters into four distinct clades. Gene clusters for the production of aflatoxins, CPA, and seven other unknown compound(s) were identified as belonging to one clade. To further explore the relationships found by gene expression analysis, aflatoxin and CPA production were quantified under five different cell culture environments known to be conducive or non-conducive for aflatoxin biosynthesis and during colonization of developing maize seeds. Results from these studies showed that secondary metabolism gene clusters have distinctive gene expression profiles. Aflatoxin and CPA were found to have unique regulation but similar enough that they would be expected to co-occur in commodities colonized with A. flavus.
2010-03-11 | GSE15435 | GEO
Project description:Aflatoxins are toxic and carcinogenic secondary metabolites produced by the fungi Aspergillus flavus and A. parasiticus. In order to better understand the molecular mechanisms that regulate aflatoxin production, the biosynthesis of the toxin in A. flavus and A. parasticus grown in yeast extract sucrose media supplemented with 50 mM tryptophan (Trp) were examined. A. flavus grown in the presence of 50 mM tryptophan was found to have significantly reduced aflatoxin B1 and B2 biosynthesis, while A. parasiticus cultures had significantly increased B1 and G1 biosynthesis. Microarray analysis of RNA extracted from fungi grown under these conditions revealed seventy seven genes that are expressed significantly different between A. flavus and A. parasiticus, including the aflatoxin biosynthetic genes aflD (nor-1), aflE (norA), and aflO (omtB). It is clear that the regulatory mechanisms of aflatoxin biosynthesis in response to Trp in A. flavus and A. parasiticus are different. These candidate genes may serve as regulatory factors of aflatoxin biosynthesis. Keywords: Aflatoxin, Aspergillus, flavus, Amnio Acids, Tryptophan
2007-06-07 | GSE6182 | GEO
Project description:Aspergillus flavus contaminates crops during preharvest and post-harvest periods and produce carcinogenic mycotoxin aflatoxins posing severe threat to food safety and human health. To identify potential targets to tackle aflatoxin contamination, we have characterized a novel Afper1, sharing sequence identity with the yeast protein per1, regulating cell development and secondary metabolism in A. flavus. Notably, proteomics analysis revealed that the enzymes involved in extracellular hydrolases, conidial development, ER homeostasis, and aflatoxin biosynthesis significantly varied. Unexpectedly, enzymes participated in scavenging ROS including catA, catB, cpeB, and sodM were significantly downregulated and the accumulated ROS and sensitivity to hydrogen peroxide were confirmed by experiments. Surprisingly, Afper1 deletion significantly unregulated heterochromatin protein (HepA) and downregulated GNAT family acetyltransferase involved in heterochromatin formation. Accompanying the accumulated ROS and chromatin remodelling, enzymes participating in aflatoxins, ustiloxin B, and gliotoxin were impaired. These results implied that Afper1 affected chromatin remodelling and disturbed ER homeostasis leading to the accumulation of ROS, and ultimately resulted in growth defect and impaired secondary metabolites biosynthesis.
2022-07-13 | PXD030015 | Pride