AtfA bZIP-type transcription factor regulates oxidative and osmotic stress responses in Aspergillus nidulans

Abstract

The aim of the study was to demonstrate that the bZIP-type transcription factor AtfA regulates different types of stress responses in Aspergillus nidulans similarly to Atf1, the orthologous 'all-purpose' transcription factor of Schizosaccharomyces pombe. Heterologous expression of atfA in a S. pombe Deltaatf1 mutant restored the osmotic stress tolerance of fission yeast in surface cultures to the same level as recorded in complementation studies with the atf1 gene, and a partial complementation of the osmotic and oxidative-stress-sensitive phenotypes was also achieved in submerged cultures. AtfA is therefore a true functional ortholog of fission yeast's Atf1. As demonstrated by RT-PCR experiments, elements of both oxidative (e.g. catalase B) and osmotic (e.g. glycerol-3-phosphate dehydrogenase B) stress defense systems were transcriptionally regulated by AtfA in a stress-type-specific manner. Deletion of atfA resulted in oxidative-stress-sensitive phenotypes while the high-osmolarity stress sensitivity of the fungus was not affected significantly. In A. nidulans, the glutathione/glutathione disulfide redox status of the cells as well as apoptotic cell death and autolysis seemed to be controlled by regulatory elements other than AtfA. In conclusion, the orchestrations of stress responses in the aspergilli and in fission yeast share several common features, but further studies are needed to answer the important question of whether a fission yeast-like core environmental stress response also operates in the euascomycete genus Aspergillus.

bZIP transcription factors affecting secondary metabolism, sexual development and stress responses in Aspergillus nidulans

“…Significantly decreased stress tolerances were found in oxidative stress (MSB, tBOOH and H 2 O 2 )-exposed RWY10.3 (DnapA) cultures ("80 % ,DDA ,"20 %); meanwhile, growth stimulation caused by the overexpression of napA (RWY17.3) was DDA ¡15 % under different oxidative stress treatments. Pyridoxine supplementation increased slightly the oxidative stress resistance of RDIT9.32 (DDA ¡5 %), which was similar to previous findings (Balá zs et al, 2010). (Halliwell & Gutteridge, 2007).…”

Piperine inhibits aflatoxin B1 production in Aspergillus flavus by modulating fungal oxidative stress response

“…As expected, mRNA levels of sod1, catA and cat2 were significantly up regulated. Studies in Aspergilli have demonstrated that both, atfA and atfB, are essentially required to activate catA expression (Balázs et al, 2010;Hagiwara et al, 2016;Lara-Rojas et al, 2011). Herein, we observed higher expression levels of catA due to the over-expression of the atfB gene.…”

“…By contrast, in our study, atfB was over expressed while veA levels were decreased suggesting that other factors may influence atfB expression. Finally, atfA, another gene mainly involved in oxidativestress response (Balázs et al, 2010), was also up-regulated. AtfA, belonging also to the ATF/CREB family, permanently resides in the nucleus until activation as a response to oxidative or osmotic stress signals (Lara-Rojas et al, 2011).…”

Stress-related Transcription Factor AtfB Integrates Secondary Metabolism with Oxidative Stress Response in Aspergilli

“…In response to oxidative stress, A. oryzae atfB directly activates the catalase gene, catA (31,49). Consistent with this theme, atf1 and its ortholog aftA activate the catalase gene ctt1 in fission yeast S. pombe and catalase B in A. nidulans, respectively (28,50). ATF/CREB family proteins also activate genes involved in osmotic stress response in S. cerevisiae and S. pombe.…”