title: Transcriptome Analysis of Aspergillus flavus Reveals veA-Dependent Regulation of Secondary Metabolite Gene Clusters, Including the Novel Aflavarin Cluster.
abstract: The global regulatory veA gene governs development and secondary metabolism in numerous fungal species, including Aspergillus flavus. This is especially relevant since A. flavus infects 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 are veA dependent. The genes responsible for the synthesis of aflatoxins are clustered, a signature common for genes involved in fungal secondary metabolism. Studies of the A. flavus genome 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 that veA is 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 of veA. One of the clusters under the influence of veA is cluster 39. The absence of veA results 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.
authors.affiliation: Food and Feed Safety Research Unit, USDA/ARS, Southern Regional Research Center, New Orleans, Louisiana, USA.
authors.forename: J W
authors.initials: JW
authors.lastname: Cary
authors.affiliation: Laboratory of Food Analysis, Faculty of Pharmaceutical Sciences, Ghent University, Ghent, Belgium.
authors.forename: Z
authors.initials: Z
authors.lastname: Han
authors.affiliation: Department of Biological Sciences, Northern Illinois University, DeKalb, Illinois, USA.
authors.forename: Y
authors.initials: Y
authors.lastname: Yin
authors.affiliation: Department of Biological Sciences, Northern Illinois University, DeKalb, Illinois, USA.
authors.forename: J M
authors.initials: JM
authors.lastname: Lohmar
authors.affiliation: Department of Biological Sciences, Northern Illinois University, DeKalb, Illinois, USA.
authors.forename: S
authors.initials: S
authors.lastname: Shantappa
authors.affiliation: Food and Feed Safety Research Unit, USDA/ARS, Southern Regional Research Center, New Orleans, Louisiana, USA.
authors.forename: P Y
authors.initials: PY
authors.lastname: Harris-Coward
authors.affiliation: Food and Feed Safety Research Unit, USDA/ARS, Southern Regional Research Center, New Orleans, Louisiana, USA.
authors.forename: B
authors.initials: B
authors.lastname: Mack
authors.affiliation: Food and Feed Safety Research Unit, USDA/ARS, Southern Regional Research Center, New Orleans, Louisiana, USA.
authors.forename: K C
authors.initials: KC
authors.lastname: Ehrlich
authors.affiliation: Food and Feed Safety Research Unit, USDA/ARS, Southern Regional Research Center, New Orleans, Louisiana, USA.
authors.forename: Q
authors.initials: Q
authors.lastname: Wei
authors.affiliation: Laboratory of Food Analysis, Faculty of Pharmaceutical Sciences, Ghent University, Ghent, Belgium.
authors.forename: N
authors.initials: N
authors.lastname: Arroyo-Manzanares
authors.affiliation: Laboratory of Food Analysis, Faculty of Pharmaceutical Sciences, Ghent University, Ghent, Belgium.
authors.forename: V
authors.initials: V
authors.lastname: Uka
authors.affiliation: Department of Veterinary Public Health and Food Safety, Laboratory of Chemical Analysis, Faculty of Veterinary Medicine, Ghent University, Ghent, Belgium.
authors.forename: L
authors.initials: L
authors.lastname: Vanhaecke
authors.affiliation: Food and Feed Safety Research Unit, USDA/ARS, Southern Regional Research Center, New Orleans, Louisiana, USA.
authors.forename: D
authors.initials: D
authors.lastname: Bhatnagar
authors.affiliation: Food and Feed Safety Research Unit, USDA/ARS, Southern Regional Research Center, New Orleans, Louisiana, USA.
authors.forename: J
authors.initials: J
authors.lastname: Yu
authors.affiliation: J. Craig Venter Institute, Rockville, Maryland, USA.
authors.forename: W C
authors.initials: WC
authors.lastname: Nierman
authors.affiliation: Department of Biological Sciences, Northern Illinois University, DeKalb, Illinois, USA.
authors.forename: M A
authors.initials: MA
authors.lastname: Johns
authors.affiliation: Department of Biological Sciences, Northern Illinois University, DeKalb, Illinois, USA.
authors.forename: D
authors.initials: D
authors.lastname: Sorensen
authors.affiliation: Department of Biological Sciences, Northern Illinois University, DeKalb, Illinois, USA.
authors.forename: H
authors.initials: H
authors.lastname: Shen
authors.affiliation: Laboratory of Food Analysis, Faculty of Pharmaceutical Sciences, Ghent University, Ghent, Belgium.
authors.forename: S
authors.initials: S
authors.lastname: De Saeger
authors.affiliation: Laboratory of Food Analysis, Faculty of Pharmaceutical Sciences, Ghent University, Ghent, Belgium.
authors.forename: J
authors.initials: J
authors.lastname: Diana Di Mavungu
authors.affiliation: Department of Biological Sciences, Northern Illinois University, DeKalb, Illinois, USA amcalvo@niu.edu.
authors.forename: A M
authors.initials: AM
authors.lastname: Calvo
mesh_terms: D000348:Aflatoxins / Q000096:biosynthesis / Q000235:genetics*; D001231:Aspergillus flavus / Q000235:genetics* / Q000472:pathogenicity; D005656:Fungal Proteins / Q000235:genetics*; D020869:Gene Expression Profiling; D015966:Gene Expression Regulation, Fungal / Q000235:genetics*; D005809:Genes, Regulator / Q000235:genetics*; D005810:Multigene Family / Q000235:genetics*; D064210:Secondary Metabolism / Q000235:genetics*; D014157:Transcription Factors / Q000235:genetics*; D059467:Transcriptome / Q000235:genetics
chemical_list: D000348:Aflatoxins; D005656:Fungal Proteins; D014157:Transcription Factors