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Differential expression of Aspergillus genes during the induction of aflatoxin biosynthesis

ABSTRACT: Gene expression analysis of A. parasiticus grown under conditions conducive and nonconductive for aflatoxin production was evaluated using glass slide microarrays containing the 753 ESTs. A complex regulatory network governs the biosynthesis of aflatoxin. While several genes involved in aflatoxin production are known, their action alone cannot account for its regulation. Arrays of clones from an Aspergillus flavus cDNA library and glass slide microarrays of ESTs were screened to identify additional genes. An initial screen of the cDNA clone arrays lead to the identification of 753 unique ESTs. Many showed sequence similarity to known metabolic and regulatory genes; however, no function could be ascribed to over 50% of the ESTs. Gene expression analysis of Aspergillus parasiticus grown under conditions conducive and non-conductive for aflatoxin production was evaluated using glass slide microarrays containing the 753 ESTs. Twenty-four genes were more highly expressed during aflatoxin biosynthesis and 18 genes were more highly expressed prior to aflatoxin biosynthesis. No predicted function could be ascribed to 18 of the 24 genes whose elevated expression was associated with aflatoxin biosynthesis. Keywords = Aspergillus Keywords = aflatoxin Keywords: time-course

ORGANISM(S): Aspergillus flavus Aspergillus parasiticus

PROVIDER: GSE204 | GEO | 2003/01/15

SECONDARY ACCESSION(S): PRJNA84551

REPOSITORIES: GEO

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Differential expression of Aspergillus genes during the induction of aflatoxin biosynthesis

Project description:Gene expression analysis of A. parasiticus grown under conditions conducive and nonconductive for aflatoxin production was evaluated using glass slide microarrays containing the 753 ESTs. A complex regulatory network governs the biosynthesis of aflatoxin. While several genes involved in aflatoxin production are known, their action alone cannot account for its regulation. Arrays of clones from an Aspergillus flavus cDNA library and glass slide microarrays of ESTs were screened to identify additional genes. An initial screen of the cDNA clone arrays lead to the identification of 753 unique ESTs. Many showed sequence similarity to known metabolic and regulatory genes; however, no function could be ascribed to over 50% of the ESTs. Gene expression analysis of Aspergillus parasiticus grown under conditions conducive and non-conductive for aflatoxin production was evaluated using glass slide microarrays containing the 753 ESTs. Twenty-four genes were more highly expressed during aflatoxin biosynthesis and 18 genes were more highly expressed prior to aflatoxin biosynthesis. No predicted function could be ascribed to 18 of the 24 genes whose elevated expression was associated with aflatoxin biosynthesis. Keywords = Aspergillus Keywords = aflatoxin Keywords: time-course

2003-01-15 | E-GEOD-204 | biostudies-arrayexpress

GAP_Culture_conditions

Project description:Gene expression analysis of A. parasiticus grown under conditions conducive and nonconductive for aflatoxin production was evaluated using glass slide microarrays containing 765 ESTs. Aflatoxins (AF) produced by Aspergillus flavus and A. parasiticus are responsible for approximately $270M in losses annually in the corn, peanut, cotton, and tree nut industries of the United States. In an attempt to develop effective control procedures, research has focused on elucidating the pathway of aflatoxin biosynthesis with the goal of identifying potential targets for intervention. Research to date points to the involvement of complex and likely overlapping regulatory circuits. To better understand the regulation by nutritional and environmental factors, a targeted cDNA microarray consisting of genes associated with AF production was employed to investigate the influence of nitrogen source, carbon source, temperature, and pH on AF production. For each nutritional or environmental parameter examined, a condition conducive for aflatoxin production was compared with a condition that was non-conducive. Three replicate cultures for each condition were grown. Cultures were grown for 24 hours and harvested. AF production for each culture was quantified and tissues were stored separately at -80C. For array hybridization, tissue samples for each condition were pooled and RNA extracted using Trizol reagent. Keywords = aspergillus Keywords = aflatoxin Keywords = regulation Keywords = secondary metabolism

2010-06-10 | E-GEOD-1649 | biostudies-arrayexpress

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Project description:Gene expression analysis of A. parasiticus grown under conditions conducive and nonconductive for aflatoxin production was evaluated using glass slide microarrays containing 765 ESTs. Aflatoxins (AF) produced by Aspergillus flavus and A. parasiticus are responsible for approximately $270M in losses annually in the corn, peanut, cotton, and tree nut industries of the United States. In an attempt to develop effective control procedures, research has focused on elucidating the pathway of aflatoxin biosynthesis with the goal of identifying potential targets for intervention. Research to date points to the involvement of complex and likely overlapping regulatory circuits. To better understand the regulation by nutritional and environmental factors, a targeted cDNA microarray consisting of genes associated with AF production was employed to investigate the influence of nitrogen source, carbon source, temperature, and pH on AF production. For each nutritional or environmental parameter examined, a condition conducive for aflatoxin production was compared with a condition that was non-conducive. Three replicate cultures for each condition were grown. Cultures were grown for 24 hours and harvested. AF production for each culture was quantified and tissues were stored separately at -80C. For array hybridization, tissue samples for each condition were pooled and RNA extracted using Trizol reagent. Keywords = aspergillus Keywords = aflatoxin Keywords = regulation Keywords = secondary metabolism Keywords: other

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Project description:We identified a 14-3-3 homolog (maf1) in an EST library made under conditions conducive to aflatoxin biosynthesis. Disruption of this gene in A. flavus by site directed mutagenesis abolished aflatoxin production. The maf1 mutant was morphologically similar to wild type but had reduced conidiation and growth on some media. DNA expression analysis of the wild type and maf1 mutant revealed that the mutation affected the expression profile of a set of genes associated with aflatoxin production. Keywords = Aspergillus Keywords = aflatoxin Keywords = 14-3-3

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Microarray analysis reveals novel regulatory genes associated with the non-aflatoxigenic Aspergillus parasiticus mutants obtained by 5-azacytosine treatment or serial mycelial transfer

Project description:Aflatoxins are carcinogenic secondary metabolites produced by the fungi Aspergillus flavus and Aspergillus parasiticus. Repeated serial mycelial transfer or treatment of A. parasiticus with 5-azacytidine produced mutants with a fluffy phenotype and loss of aflatoxin production. To understand how these treatments affect aflatoxin production and development, we carried out expressed sequence tag (EST)-based microarray assays to identify differentially expressed genes in clones obtained from these treatments. Expression of 183 genes was significantly dysregulated. Of these, 38 had at least two-fold or lower expression compared to the untreated control and only two had two-fold or higher expression. The most frequent change was downregulation of genes predicted to be membrane-bound. Dysregulation of some of these may be responsible for the fluffy phenotype. Of the aflatoxin biosynthesis pathway genes only aflJ (aflS) was significantly affected by either treatment. A gene for a protein homologous to a key regulator of secondary metabolite biosynthesis (LaeA) was one of the upregulated genes and possibly could affect the activity of LaeA. Other genes known to be required for fungal developmental or aflatoxin production were not affected by the treatments. Consistent with the fluffy phenotype and the non-aflatoxigenicity of the clones obtained by either treatment, we hypothesize that the mutations cause improper development of conidiophores and specialized biosynthesis vacuoles (aflatoxisomes) needed for AF production. A. parasiticus wild-type (WT) and clones from serial mycelial transfer (SerTrans), and 5-azacytidine-treated (5-AC) fungi were grown for 16 and 24 h on PDA medium. RNA was isolated from the mycelia at each time point and cDNAs were labeled with Cy3 or Cy5 dyes prior to microarray assay.

2011-12-31 | E-GEOD-30756 | biostudies-arrayexpress

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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.

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