The mitochondrial membrane protein FgLetm1 regulates mitochondrial integrity, production of endogenous reactive oxygen species and mycotoxin biosynthesis in Fusarium graminearum

SUMMARY Deoxynivalenol (DON) is a mycotoxin produced in cereal crops infected with Fusarium graminearum. DON poses a serious threat to human and animal health and is a critical virulence factor. Various environmental factors including reactive oxygen species (ROS) have been shown to interfere with DON biosynthesis in this pathogen. The regulatory mechanisms of how ROS trigger DON production have been extensively investigated in F. graminearum. However, the role of the endogenous ROS generating system in DON biosynthesis is largely unknown. In this study, we genetically analyzed the function of Leucine zipper–EF-hand–containing trans-membrane 1(LETM1) super-family proteins and evaluated the role of the mitochondria-produced ROS in DON biosynthesis. Our results show that there are two Letm1 orthologs, FgLetm1 and FgLetm2, in F. graminearum. FgLetm1 is localized to the mitochondria and is essential for mitochondrial integrity, whereas FgLetm2 plays a minor role in maintaining mitochondrial integrity. The ΔFgLetm1 mutant demonstrated a vegetative growth defect, abnormal conidia and increased sensitivity to various stress agents. More importantly, the ΔFgLetm1 mutant showed significantly reduced levels of endogenous ROS, decreased DON biosynthesis and attenuated virulence in planta. To our knowledge, this is the first report that mitochondrial integrity and endogenous ROS production by mitochondria are important for DON production and virulence in Fusarium species. This article is protected by copyright. All rights reserved.