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. The fungus Rhizophagus irregularis accumulates predominantly palmitic acid (16:0) and the unusual palmitvaccenic acid (16:1{Delta}11cis). Here, we present the isolation and characterization of RiOLE1-LIKE, the desaturase involved in palmitvaccenic acid synthesis, by heterologous expression in yeast and plants. Results are in line with the scenario that 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 non-symbiotic Mortierellaceae and Mucoromycotina fungi, suggesting that 16:1{Delta}11cis provides a specific function during AM colonization.