Iron acquisition and storage in all cells must be carefully regulated to avoid iron-induced toxicity. Alternaria alternata produces a dimethyl coprogen siderophore to acquire iron from surrounding environment. The ability to acquire iron is also required for detoxification of reactive oxygen species and virulence. Genetic analysis reveals that a SreA gene encoding a GATA type transcription factor negatively regulates siderophore production. A. alternata strains lacking SreA (?sreA) increase siderophore production by 3.7-fold compared to wild type. ?sreA displays wild-type virulence in citrus, even though the mutant reduces 77% radial growth of wild type grown on PDA. An iron chelator and EDTA partially rescue mutant growth. ?sreA reduces 43% growth on minimal medium and slightly increases sensitivity to iron, potassium superoxide, and H₂O₂. However, ?sreA decreases sensitivity to diethyl maleate, rose Bengal, eosin Y, Congo red, and calcofluor white. The expression of SreA is induced by iron and repressed by H₂O₂, and negatively regulated by the oxidative stress-responsive transcription activator Yap1. Deletion of SreA leads to the increased expression of the genes involved in siderophore biosynthesis and transportation and reductive iron assimilation. EMSA reveals that the E.coli-expressed SreA protein could bind the promoter of the Nps6 gene encoding a nonribosomal peptide synthetase required for siderophore biosynthesis. Our results demonstrate that SreA plays a profound role in iron homeostasis and cellular sensitivity to xenobiotics.