SKN1, a novel plant defensin-sensitivity gene in Saccharomyces cerevisiae, is implicated in sphingolipid biosynthesis.

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 beta-1,6-glucan biosynthesis. We demonstrate that a Deltaskn1 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.