The antifungal plant defensin DmAMP1 interacts with the fungal sphingolipid mannosyl diinositolphosphoryl ceramide (M(IP) 2 C) and induces fungal growth inhibition. We have identified SKN1, besides the M(IP) 2 C-biosynthesis gene IPT1, as a novel DmAMP1-sensitivity gene in Saccharomyces cerevisiae. SKN1 was previously shown to be a KRE6 homologue, which is involved in β-1,6-glucan biosynthesis. We demonstrate that a Δskn1 mutant lacks M(IP) 2 C. Interestingly, overexpression of either IPT1 or SKN1 complemented the skn1 mutation, conferred sensitivity to DmAMP1, and resulted in M(IP) 2 C levels comparable to the wild type. These results show that SKN1, together with IPT1, is involved in sphingolipid biosynthesis in S. cerevisiae.