Identification and functional characterization of a glycosylceramide Delta 3-(E) desaturase from phytopathogenic fungi
Final Report Abstract
?3(E)-unsaturated fatty acids are characteristic components of glycosylceramides from some fungi, including also human- and 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 ?3-unsaturation of 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 sphingoHpid-?(E)- desaturase: Deletion of the candidate gene in F. graminearum resulted in loss of the ?3(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 ?3(E)-unsaturated GlcCer. We could show that the loss of ?3(E)-unsaturated GlcCer In F. graminearum led to increased resistance towards two antifungal peptides from Aspergillus giganteus and radish seeds. Whether these defensins directly interact with GlcCer and whether also the pathogenicity and virulence of the fungus towards wheat or maize are affected by the loss of ?3-unsaturation could not be determined during the funding period. It would be interesting to analyze these aspects in more detail in a follow up project.
Publications
- (2008): Identification and functional characterization of the 2-hydroxy fatty N-acyl-A3(E)-desaturase from Fusarium graminearum. Journal of Biological Chemistry 283:36734-36742
S. Zäuner, U. Zähringer, B. Lindner, D. Warnecke and P. Sperling
- (2009): Functional characterisation of a higher plant sphingolipid A4-desaturase: defining the role of sphingosine and sphingosine-1-phosphate in Arabidopsis thaliana. Plant Physiology 149:487-498
L.V. Michaelson, S. Zäuner, J.E. Markham, R. Haslam, R. Desikan, S. Mugford, S. Albrecht, D. Warnecke. P. Sperling, E. Heinz and J.A. Napier
