Aspergillus flavus
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PROVIDER: PRJNA294865 | ENA |
REPOSITORIES: ENA
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Project description:Aspergillus flavus and A. parasiticus are two of the most important aflatoxin-producing species that contaminate agricultural commodities worldwide. Both species are heterothallic and undergo sexual reproduction in laboratory crosses. Here, we examine the possibility of interspecific matings between A. flavus and A. parasiticus. These species can be distinguished morphologically and genetically, as well as by their mycotoxin profiles. Aspergillus flavus produces both B aflatoxins and cyclopiazonic acid (CPA), B aflatoxins or CPA alone, or neither mycotoxin; Aspergillus parasiticus produces B and G aflatoxins or the aflatoxin precursor O-methylsterigmatocystin, but not CPA. Only four out of forty-five attempted interspecific crosses between compatible mating types of A. flavus and A. parasiticus were fertile and produced viable ascospores. Single ascospore strains from each cross were isolated and were shown to be recombinant hybrids using multilocus genotyping and array comparative genome hybridization. Conidia of parents and their hybrid progeny were haploid and predominantly monokaryons and dikaryons based on flow cytometry. Multilocus phylogenetic inference showed that experimental hybrid progeny were grouped with naturally occurring A. flavus L strain and A. parasiticus. Higher total aflatoxin concentrations in some F1 progeny strains compared to midpoint parent aflatoxin levels indicate synergism in aflatoxin production; moreover, three progeny strains synthesized G aflatoxins that were not produced by the parents, and there was evidence of putative allopolyploidization in one strain. These results suggest that hybridization is an important diversifying force resulting in the genesis of novel toxin profiles in these agriculturally important species.
2015-10-01 | GSE61981 | 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:RNA-seq was used to compare differential gene expressions for Aspergillus flavus wild type strain and ASPES transcription factor deletion strains.The goals of this study are to explore the aflatoxin regulation pathway in A. flavus.
2018-12-25 | GSE107025 | GEO
Project description:Purpose: Aflatoxin B1 is the most toxic and carcinogenic compound in nature produced by Aspergillus fungi. In our study, we applied RNA-seq to compare the transcriptomic profiles of Aspergillus flavus strains in the presence and absence of medicinal plant Zanthoxylum bungeanum. Methods: mRNA profiles of Aspergillus flavus supplemented with 250 µg/ml of methanolic extract fraction (treated samples) or DMSO (control samples) were generated in triplicate, by an Illumina platform using paired-end 150 bp sequencing strategy. Clean paired-end reads were mapped to the reference genome of A. flavus NRRL3357. Gene expression quantification was calculated by FPKM (Fragments Per Kilobase of transcript sequence per Millions base pairs sequenced). The differentially expressed genes (DGEs) between the control and test samples were analyzed using the DESeq2 R package. Results: RNA-seq produced 24.5–32.1 million clean paired-end reads (150 bp read length) per sample and most of them (83–91%) were uniquely mapped to the reference genome of A. flavus NRRL3357. Eighty-two percent of genes displayed FPKM value ≥1 and were thus classified as expressed genes. Ninety-six percent of the expressed genes were expressed both in the control and test groups whereas 2.3% and 1.8% of the genes were expressed only in the control or test group, respectively. With the combination of FPKM fold change ≥2 and adjusted p-value <0.05, we found in total 950 DEG’s. Among them, 515 genes were downregulated and 435 genes were upregulated. We used FungiFun software to analyze the functions of the DEGs based on FunCat pathways and categories. About half of the DEG’s had a relevant annotation in the FunCat database, and 60–70% of the annotated DEG’s were found to be enriched in specific functional pathways. Conclusions: we showed that simple organic extracts from Z. bungeanum inhibit both the growth and aflatoxin production by Aspergillus flavus. The repression of AF pathway is mediated by global regulators instead of pathway specific regulators AflR or AflS. Consistently, the expression of Velvet complex, a prominent regulator of fungal secondary metabolism and development, was substantially reduced. Natural compound extracts from Z. bungeanum have potential to facilitate the development of safe and economical control strategies that shutdown aflatoxin production in aflatoxigenic Aspergillus species.
2022-04-10 | GSE179477 | GEO
Project description:Aspergillus flavus is a common saprophyte and opportunistic pathogen producing aflatoxin (AF) and many other secondary metabolites. 5-Azacytidine (5-AC), a derivative of nucleoside cytidine, is widely used for studies in epigenetics and cancer biology as an inactivator of DNA methyltransferase and is also used for studying secondary metabolism in fungi. Our previous studies showed that 5-AC affects development and inhibits AF production in A. flavus, and that A. flavus lacks DNA methylation. How this common DNA methyltransferase inhibitor affects development and AF production is not clear. In this study, we applied an RNA-Seq approach to elucidate the mechanism of 5-ACM-bM-^@M-^Ys effect on A. flavus. In our current study, we identified 240 significantly differently expressed (Q-value<0.05) genes after 5-AC treatment, including two backbone genes in secondary metabolite clusters #27 and #35, which are involved in development or survival of sclerotia. With 5-AC treatment, about three quarters of the genes in the AF biosynthetic gene cluster in A. flavus were down-regulated to a certain degree. Strikingly, at least two genes aflI and aflLa, were completely inhibited. Interestingly, several genes involved in fungal development were down-regulated, especially veA, which is a gene that encodes protein bridges VelB and LaeA. This result supports the hypothesis that 5-AC affects development and AF production through weakening or even interrupting the connection between VelB and LaeA and then causing dysregulation of the expression pattern of genes involved in development and secondary metabolism. Our results improved the A. flavus genome annotation, provided a comprehensive view of the transcriptome of A. flavus responding to 5-AC and confirmed that fungal development and secondary metabolism are co-regulated. In additon, the RNA-Seq data of another sample treated with gallic acid was used to improve A. flavus genome annotation. mRNA of Aspergillus flavus cultured in three different culture media PDB, PDB+5-AC(5-Azacytidine),and PDB+GA(gallic acid) was subjected to sequence independently.
2013-06-15 | E-GEOD-40202 | biostudies-arrayexpress
Project description:We report here the AflR binding motif of Aspergillus flavus for the first time with the aid of ChIP-seq analysis. Of the 540 peak sequences associated with AflR binding events, 66.8% were located within 2 kb upstream (promoter region) of translational start sites. The identified 18-bp binding motif was a perfect palindromic sequence, 5′-CSSGGGWTCGAWCCCSSG’3′ with S representing G or C and W representing A or T. On closer examination, we hypothesized that the 18-bp motif sequence identified contained two identical parts (here called motif A and motif B). Motif A was in positions 8–18 on the upper strand, while motif B was in positions 11-1 on the bottom strand. The inferred length and sequence of the putative motif identified in A. flavus were similar to previous findings in A. parasiticus and A. nidulans. Gene ontology analysis indicated that AflR bound to other genes outside the aflatoxin biosynthetic gene cluster.
2020-05-02 | GSE149696 | GEO
Project description:Aspergillus flavus first gained scientific attention for its production of aflatoxin, the most potent naturally occurring toxin and hepatocarcinogenic secondary metabolite. For several decades, The DNA methylation status of A. flavus remains to be controversial. We first applied bisulfite sequencing, the gold standard at present, in conjunction with a biological replicate strategy to investigate the DNA methylation profiling of A. flavus genome. Our results reveal that the DNA methylation level of this fungus turns out to be negligible, comparable to the unmethylated lambda DNA we set as the false positive control of our bisulfite experiments. When comparing the DNA methyltransferase homolog of A. flauvs with that from several selected hypermethylated speices, we find that the DNA methyltransferase homolog of A.flavus as well as the other Aspergillus members groups closely with the RID from Neurospora crassa and Masc1 from Ascobolus immerses, which has been reported as DMT-incapable, but it diverges distantly from the other capable DNA methyltransferases. We observe significant depletion of repeat components within the A. flavus, which may possibly explain the lack of DNA methylation in this fungus. What's more, the RIP-index of the repeat of A. flavus turns out to be higher than the fungi without RID-like enzyme, suggesting this asexual fungus may possibly possess RIP process during the obscure sexual-stage which is very evanescent and may potentially related to DNA methylation. This work contributes to our understanding on the DNA methylation status of A. flavus. Also, it reinforces our views on the DNA methylation in fungal species. What's more, our strategy of applying bisulfite sequencing to DNA methylation detection on species with low DNA methylation may serve as a reference for later scientific investigations on other hypomethylated species. Two replicates were subjected to bisulfite conversion independently, unmethylated lambda DNA as a false positive control is added to both replicates.
2012-03-01 | E-GEOD-32177 | biostudies-arrayexpress
Project description:Objective: Aspergillus flavus aflR, a gene encoding a Zn(II)2Cys6 DNA-binding domain, is an important transcriptional regulator of the aflatoxin biosynthesis gene cluster. Our previous results of GO analysis for the binding sites of AflR in A. flavus suggest that AflR may play an integrative regulatory role. This study aimed to investigate the integrative function of the aflR gene in A. flavus. Design: In this study, we used Aspergillus flavus NRRL3357 as a wild-type strain (WT) and constructed a knockout strain of A. flavus ΔaflR by homologous recombination. Based on the transcriptomics technology, we investigated the metabolic effects of aflR gene on growth, development and toxin synthesis of A. flavus, and discussed the overall regulation mechanism of aflR gene on A. flavus at the transcriptional level. Results: The disruption of aflR severely affected the aflatoxin biosynthetic pathway, resulting in a significant decrease in aflatoxin production. In addition, disrupted strains of the aflR gene produced relatively sparse conidia and a very small number of sclerotia. However, the biosynthesis of cyclopiazonic acid (CPA) was not affected by aflR gene disruption. Transcriptomic analysis of the ΔaflR strain grown on potato dextrose agar (PDA) plates at 0 h, 24 h, and 72 h showed that expression of clustering genes involved in the biosynthesis of aflatoxin was significantly down-regulated. Meanwhile, the ΔaflR strain showed significant expression differences in genes involved in spore germination, sclerotial development, and carbohydrate metabolism compared to the WT strain. Conclusions: The results showed that the A. flavus aflR gene also played a positive role in the growth and development of fungi.
2021-07-16 | GSE179978 | GEO
Project description:Aspergillus flavus strain:YC-15 Raw sequence reads
| PRJNA433591 | ENA