bZIP transcription factor AflHapX coordinates iron homeostasis and aflatoxin biosynthesis in Aspergillus flavus

Iron homeostasis and secondary metabolism are controlled by the basic leucine zipper (bZIP) transcription factor HapX in many fungi. In this study, AflHapX was identified through homology research of the Aspergillus flavus genome with the bZIP protein HapX in Aspergillus fumigatus and subsequent gene deletion. We established that AflHapX functions as a regulator for adaptation to iron-excess and iron-starvation conditions. The AflhapX deletion strain (ΔAflhapX) produces less aflatoxin B1 (AFB1) compared to the wild type (WT) and complementary strain (ΔAflhapXC) on YES medium. While iron typically represses AFB1 biosynthesis in A. flavus, the deletion of AflhapX restores iron’s inhibition of AFB1 production. Furthermore, compared to WT and ΔAflhapXC, ΔAflhapX produced more sclerotia and displayed greater sensitivity to the oxidative reagents H2O2, menadione sodium bisulfite (MSB), and diamide. On peanuts, the ΔAflhapX strain produced fewer conidia and less AFB1 than WT and ΔAflhapXC. Transcriptome analysis data provided evidence that AflHapX globally regulates genes involved in aflatoxin biosynthesis, oxidative stress response, and iron homeostasis. Our results suggest that AflHapX may regulate the effect of iron on aflatoxin production.