Transcriptome-Based Modeling Reveals that Oxidative Stress Induces Modulation of the AtfA-Dependent Signaling Networks in Aspergillus nidulans.

Erzsébet Orosz,Tamás Emri,Zsuzsa Szabó,Kap-Hoon Han,István Pócsi,Zoltán Gazdag,Károly Antal,Jae-Hyuk Yu

doi:10.1155/2017/6923849

Abstract

To better understand the molecular functions of the master stress-response regulator AtfA in Aspergillus nidulans, transcriptomic analyses of the atfA null mutant and the appropriate control strains exposed to menadione sodium bisulfite- (MSB-), t-butylhydroperoxide- and diamide-induced oxidative stresses were performed. Several elements of oxidative stress response were differentially expressed. Many of them, including the downregulation of the mitotic cell cycle, as the MSB stress-specific upregulation of FeS cluster assembly and the MSB stress-specific downregulation of nitrate reduction, tricarboxylic acid cycle, and ER to Golgi vesicle-mediated transport, showed AtfA dependence. To elucidate the potential global regulatory role of AtfA governing expression of a high number of genes with very versatile biological functions, we devised a model based on the comprehensive transcriptomic data. Our model suggests that an important function of AtfA is to modulate the transduction of stress signals. Although it may regulate directly only a limited number of genes, these include elements of the signaling network, for example, members of the two-component signal transduction systems. AtfA acts in a stress-specific manner, which may increase further the number and diversity of AtfA-dependent genes. Our model sheds light on the versatility of the physiological functions of AtfA and its orthologs in fungi.

Highlights

Oxidative stress is commonly defined as a physiological state when the negative effects of reactive oxygen species (ROS) significantly decrease the fitness of stress-exposed cells
Owing to its importance in the regulation of stress tolerance and secondary metabolism, AtfA significantly contributes to the virulence of plant pathogenic fungi [25, 27,28,29], and it is essential for the virulence of the human pathogenic A. fumigatus [19, 20, 31]
We investigated the genome-wide transcriptional changes mounted in A. nidulans, when it was exposed to six types of stresses, including oxidative stress (menadione sodium bisulfite (MSB), low and high concentration of H2O2, t-butylhydroperoxide, diamide) and high-osmolarity stress (NaCl) [23]

Summary

Introduction

Oxidative stress is commonly defined as a physiological state when the negative effects of reactive oxygen species (ROS) significantly decrease the fitness of stress-exposed cells. AtfA has been characterized as a regulator of conidial stress tolerance in A. nidulans, A. fumigatus, and A. oryzae [18,19,20,21]. AtfA is an important component of a central multiple-stress signaling pathway regulating development in filamentous fungi as well [24]. AtfB, an orthologue/paralogue of AtfA, is an important transcription factor which integrates mycotoxin production and oxidative stress response in Aspergillus parasiticus and probably in other aspergilli as well [30]. Owing to its importance in the regulation of stress tolerance and secondary metabolism, AtfA significantly contributes to the virulence of plant pathogenic fungi [25, 27,28,29], and it is essential for the virulence of the human pathogenic A. fumigatus [19, 20, 31]. The involvement of AtfA in virulence and/or mycotoxin production in several fungi explains the ceaseless interest in this bZIP-type transcription factor

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Conclusion