title: VeA is associated with the response to oxidative stress in the aflatoxin producer Aspergillus flavus.
abstract: Survival of fungal species depends on the ability of these organisms to respond to environmental stresses. Osmotic stress or high levels of reactive oxygen species (ROS) can cause stress in fungi resulting in growth inhibition. Both eukaryotic and prokaryotic cells have developed numerous mechanisms to counteract and survive the stress in the presence of ROS. In many fungi, the HOG signaling pathway is crucial for the oxidative stress response as well as for osmotic stress response. This study revealed that while the osmotic stress response is only slightly affected by the master regulator veA, this gene, also known to control morphological development and secondary metabolism in numerous fungal species, has a profound effect on the oxidative stress response in the aflatoxin-producing fungus Aspergillus flavus. We found that the expression of A. flavus homolog genes involved in the HOG signaling pathway is regulated by veA. Deletion of veA resulted in a reduction in transcription levels of oxidative stress response genes after exposure to hydrogen peroxide. Furthermore, analyses of the effect of VeA on the promoters of cat1 and trxB indicate that the presence of VeA alters DNA-protein complex formation. This is particularly notable in the cat1 promoter, where the absence of VeA results in abnormally stronger complex formation with reduced cat1 expression and more sensitivity to ROS in a veA deletion mutant, suggesting that VeA might prevent binding of negative transcription regulators to the cat1 promoter. Our study also revealed that veA positively influences the expression of the transcription factor gene atfB and that normal formation of DNA-protein complexes in the cat1 promoter is dependent on AtfB.
authors.affiliation: Department of Biological Sciences, Northern Illinois University, Dekalb, Illinois, USA.
authors.forename: Sachin
authors.initials: S
authors.lastname: Baidya
authors.affiliation: Department of Biological Sciences, Northern Illinois University, Dekalb, Illinois, USA.
authors.forename: Rocio M
authors.initials: RM
authors.lastname: Duran
authors.affiliation: Department of Biological Sciences, Northern Illinois University, Dekalb, Illinois, USA.
authors.forename: Jessica M
authors.initials: JM
authors.lastname: Lohmar
authors.affiliation: Southern Regional Research Center, Agricultural Research Service, U.S. Department of Agriculture, New Orleans, Louisiana, USA.
authors.forename: Pamela Y
authors.initials: PY
authors.lastname: Harris-Coward
authors.affiliation: Southern Regional Research Center, Agricultural Research Service, U.S. Department of Agriculture, New Orleans, Louisiana, USA.
authors.forename: Jeffrey W
authors.initials: JW
authors.lastname: Cary
authors.affiliation: Department of Food Science and Human Nutrition, Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, Michigan, USA.
authors.forename: Sung-Yong
authors.initials: SY
authors.lastname: Hong
authors.affiliation: Department of Food Science and Human Nutrition, Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, Michigan, USA.
authors.forename: Ludmila V
authors.initials: LV
authors.lastname: Roze
authors.affiliation: Department of Food Science and Human Nutrition, Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, Michigan, USA.
authors.forename: John E
authors.initials: JE
authors.lastname: Linz
authors.affiliation: Department of Biological Sciences, Northern Illinois University, Dekalb, Illinois, USA amcalvo@niu.edu.
authors.forename: Ana M
authors.initials: AM
authors.lastname: Calvo
mesh_terms: D000222:Adaptation, Physiological; D000348:Aflatoxins / Q000096:biosynthesis; D001231:Aspergillus flavus / Q000235:genetics / Q000378:metabolism*; D002374:Catalase / Q000235:genetics / Q000378:metabolism; D004271:DNA, Fungal / Q000235:genetics / Q000378:metabolism; D005656:Fungal Proteins / Q000502:physiology*; D015870:Gene Expression; D015966:Gene Expression Regulation, Fungal; D009997:Osmotic Pressure; D018384:Oxidative Stress; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D014157:Transcription Factors / Q000502:physiology*
chemical_list: D000348:Aflatoxins; D004271:DNA, Fungal; D005656:Fungal Proteins; D014157:Transcription Factors; D002374:Catalase