 Oxidative stress is a major cause of secondary metabolism in fungi and plants. Transcription factors related to oxidative stress response have been found to play a role in controlling secondary metabolism. For example, aflatoxin biosynthesis, a model of secondary metabolism, has been shown to be triggered and intensified by reactive oxygen species buildup. Additionally, recent studies have identified a regulatory network composed of at least for transcription factors that control the expression of genes involved in aflatoxin biosynthesis and antioxidant genes. These findings suggest that secondary metabolism may serve as a secondary line of defense against oxidative stress. This article was authored by John E. Lins, Sun Yong-hwan, and Ludmila V. Rose.