Palmitvaccenic Acid (Δ11- cis -hexadecenoic acid) Is Synthesized by an OLE1-like Desaturase in the Arbuscular Mycorrhiza Fungus Rhizophagus irregularis .

Arbuscular mycorrhiza (AM) fungi deliver mineral nutrients to the plant host in exchange for reduced carbon in the form of sugars and lipids. Colonization with AM fungi upregulates a specific host lipid synthesis pathway resulting in the production of fatty acids. Predominantly palmitic acid (16:0) and the unusual palmitvaccenic acid (16:1 ^Δ11cis ) accumulate in the fungus Rhizophagus irregularis . Here, we present the isolation and characterization of Ri OLE1-LIKE, the desaturase involved in palmitvaccenic acid synthesis, by heterologous expression in yeast and plants. Results are in line with the scenario in which RiOLE1-LIKE encodes an acyl-CoA desaturase with substrate specificity for C15-C18 acyl groups, in particular C16. Phylogenetic analysis of RiOLE1-LIKE -related sequences revealed that this gene is conserved in AM fungi from the Glomales and Diversisporales but is absent from nonsymbiotic Mortierellaceae and Mucoromycotina fungi, suggesting that 16:1 ^Δ11cis provides a specific function during AM colonization.