Identification and functional characterization of the 2-hydroxy fatty N-acyl-Δ3(E)-desaturase from Fusarium graminearum

Abstract

Δ3(E)-Unsaturated fatty acids are characteristic components of glycosylceramides from some fungi, including also humanand plant-pathogenic species. The function and genetic basis for this unsaturation is unknown. For Fusarium graminearum, which is pathogenic to grasses and cereals, we could show that the level of Δ3-unsaturation of glucosylceramide (GlcCer) was highest at low temperatures and decreased when the fungus was grown above 28°C. With a bioinformatics approach, we identified a new family of polypeptides carrying the histidine box motifs characteristic for membrane-bound desaturases. One of the corresponding genes was functionally characterized as a sphingolipid-Δ3(E)-desaturase. Deletion of the candidate gene in F. graminearum resulted in loss of the Δ3(E)-double bond in the fatty acyl moiety of GlcCer. Heterologous expression of the corresponding cDNA from F. graminearum in the yeast Pichia pastoris led to the formation of Δ3(E)-unsaturated GlcCer. © 2008 by The American Society for Biochemistry and Molecular Biology, Inc.