Deletion and Overexpression of the AnOTAbzip Gene, a Positive Regulator of Ochratoxin A Biosynthesis in Aspergillus niger

Abstract

The ochratoxin A (OTA) biosynthetic gene cluster includes a bZIP transcription factor (TF) gene (OTAbzip) that has been identified in different fungal species. However, most previous studies identified the OTAbzip gene in ochratoxigenic fungi using bioinformatics methods, while few studies focused on deleting the gene, let alone overexpressing it, to characterize the function of the OTAbZIP TF. Here, we characterized the AnOTAbZIP TF in an ochratoxigenic isolate of Aspergillus niger by deleting and overexpressing the AnOTAbzip gene and examining the role of AnOTAbZIP in morphological development, OTA biosynthesis, and pathogenicity. Chemical and gene expression analyses revealed that AnOTAbZIP positively regulates OTA biosynthesis, since the loss of OTA production and the downregulation of the OTA biosynthetic genes were observed in the ΔAnOTAbzip strain, compared with the wild-type (WT) and OE::AnOTAbzip strains. In terms of pathogenicity, the ΔAnOTAbzip strain produced a greater lesion on grape berries, especially with respect to the OE::AnOTAbzip strain, rather than WT. Finally, the ΔAnOTAbzip strain was also more tolerant to oxidative stress with respect to the OE::AnOTAbzip and WT strains in that order. These new findings improve our understanding of the AnOTAbZIP regulatory mechanism and help develop strategies to attenuate plant pathogenicity and reduce OTA biosynthesis of A. niger.

Fumonisin B1 Biosynthesis Is Associated with Oxidative Stress and Plays an Important Role in Fusarium proliferatum Infection on Banana Fruit

“…Further, the ΔFpf um21 strain was much more susceptible to ROS stress (Figure 7C,D), confirming that FB1 biosynthesis was vital for F. proliferatum in response to oxidative stress. However, a recent study found that the inhibition of OTA biosynthesis results in stronger pathogenicity and ROS tolerance, 9 suggesting the different roles of different mycotoxins biosynthesis in response to ROS stress. Previous research reported that deficiency in fumonisin biosynthesis results in a substantial reduction of F. verticillioides virulence in plant hosts.…”

“…In response to pathogen attack, plants establish a broad range of defense responses to protect themselves, including rapid production of reactive oxygen species (ROS). , Importantly, disease development in harvested fruit also results from the disorder of ROS metabolism. , Hence, ROS stress is one of the most important stresses confronted by fungi during the infection process. In turn, ROS detoxification is critical for the pathogenicity of pathogens .…”