Summary Ustilaginoidins, toxic to plants, animals and human, are one of major types of mycotoxins produced by Ustilaginoidea virens . In this study, a gene cluster containing the polyketide synthase gene UvPKS1 was analysed via gene replacement and biochemical studies to determine ustilaginoidin biosynthetic pathway in U. virens . UvPKS1 was first proven to be responsible for the first step of ustilaginoidin biosynthesis, sinc...