AtfA-Independent Adaptation to the Toxic Heavy Metal Cadmium in Aspergillus nidulans

Abstract

Cadmium is an exceptionally toxic industrial and environmental pollutant classified as a human carcinogen. In order to provide insight into how we can keep our environment safe from cadmium contamination and prevent the accumulation of it in the food chain, we aim to elucidate how Aspergillus nidulans, one of the most abundant fungi in soil, survives and handles cadmium stress. As AtfA is the main transcription factor governing stress responses in A. nidulans, we examined genome-wide expression responses of wild-type and the atfA null mutant exposed to CdCl2. Both strains showed up-regulation of the crpA Cu2+/Cd2+ pump gene and AN7729 predicted to encode a putative bis(glutathionato)-cadmium transporter, and transcriptional changes associated with elevated intracellular Cys availability leading to the efficient adaptation to Cd2+. Although the deletion of atfA did not alter the cadmium tolerance of the fungus, the cadmium stress response of the mutant differed from that of a reference strain. Promoter and transcriptional analyses of the “Phospho-relay response regulator” genes suggest that the AtfA-dependent regulation of these genes can be relevant in this phenomenon. We concluded that the regulatory network of A. nidulans has a high flexibility allowing the fungus to adapt efficiently to stress both in the presence and absence of this important transcription factor.

Functional analysis of the bZIP-type transcription factors AtfA and AtfB in Aspergillus nidulans

“…Overexpression of atfB decreased the tolerance of the fungus to CdCl 2 ( Figure 1 ). Genome wide expression study by Emri et al (2021) in A. nidulans confirmed that exposure to CdCl 2 downregulates atfB gene expression in the control strain, while no alteration of the atfB expression was observed in the ΔatfA mutant (transcriptome data accession number: GSE166128). Overexpression of atfB decreased the number and increased the size of asexual spores ( Figures 3B , 4 ) and also increased the abaA gene expression ( Adams et al, 1998 ).…”

Heavy metal resistant Aspergillus species from soil and water environments impacted by solid wastes dumping exhibit mycoremediative traits

“…Previously, the tolerance capability of A. nidulans to Cd, Cu and Pb heavy metals had been reported with particular reference to its tolerance to Fe at 800 mgl -1 concentration (Oladipo et al, 2016). Also, Emri et al (2021), reported that Aspergillus nidulans tolerated Cd concentrations. However, studies on the exposure and tolerance of A. nidulans to Sn were not found and generally, literature on the exposure of A. nidulans to heavy metals were highly limited.…”

Strategies Shaping the Transcription of Carbohydrate-Active Enzyme Genes in Aspergillus nidulans

“…RNA sequencing (from library preparation to generation of fastq.gz files) as well as the RT-qPCR assays was carried out at the Genomic Medicine and Bioinformatic Core Facility, Department of Biochemistry and Molecular Biology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary. A single-read 75 bp Illumina sequencing was performed as described previously [43]. All library pools were sequenced in the same lane of a sequencing flow cell, and 11.5-20.8 million reads per sample were obtained.…”