Fungal infection of wild-type Drosophila induces rapid expression of drosomycin, an AMP with antifungal properties, but mutants for Spaetzle, Toll, Tube, and Pelle show reduced levels of drosomycin upon fungal infection (Fehlbaum et al., 1994; Lemaitre et al., 1996). Here, IRAK1 is linked to fungal infectious disease.