Effects of temperature on the production of ochratoxin A by Aspergillus niger

This study aimed to investigate the effects of temperature on OTA production by Aspergillus niger and charac-terized the underlying regulatory metabolism. The results indicated that 23 degrees C induced OTA production, when compared with a non-inducing temperature of 30 degrees C. Genes involved in the OTA biosynthesis cluster, including p450, nrps, and hal, were up-regulated; genes related to antioxidants, such as cat, pod, and gstA, were down-regulated; and genes participating in oxidative phosphorylation, including those encoding succinate dehydro-genase and ATP synthase, were up-regulated at 23 degrees C, when compared to 30 degrees C. Correspondingly, the content of H2O2 and O2-, the sensitivity to H2O2, the mitochondrial complex II activity and ATP content were increased at 23 degrees C. These results indicated that temperature altered the cellular redox homeostasis and oxidative phos-phorylation, and up-regulated expressions of OTA biosynthesis genes, thus ultimately triggering OTA biosyn-thesis. Notably, the novel and most significantly up-regulated zinc finger transcriptional factor, An12g06480, which was essential for A. niger growth and OTA biosynthesis, was identified. In the An12g06480 deletion strain, OTA production was significantly inhibited, and decreased by 89.47%. In addition, deletion of An12g06480 decreased mitochondrial complex II activity and ATP content by 81.41% and 16.17%, indicating that An12g06480 positively affected OTA biosynthesis by regulating cellular oxidative phosphorylation.