Identification and functional characterization of indole-3-acetamide-mediated IAA biosynthesis in plant-associated Fusarium species

► An IAM gene cluster was identified in Fusarium species of the Gibberella fujikuroi species complex. ► The cluster is fully functional in IAA production only in Fusarium proliferatum ET1. ► The gene cluster is also found in Colletotrichum, but not in any other fungal genome database. ► IAA production is regulated through transcription levels of the IaaM gene. ► Sequence analyses suggest the possibility of a horizontal gene transfer from bacteria to fungi.