Palmitvaccenic acid (Δ11-cis-hexadecenoic acid) is synthesized by an OLE1-like desaturase in the arbuscular mycorrhiza fungusRhizophagus irregularis

Abstract

AbstractArbuscular 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 fungusRhizophagus irregularisaccumulates predominantly palmitic acid (16:0) and the unusual palmitvaccenic acid (16:1Δ11cis). Here, we present the isolation and characterization ofRiOLE1-LIKE, the desaturase involved in palmitvaccenic acid synthesis, by heterologous expression in yeast and plants. Results are in line with the scenario thatRiOLE1-LIKEencodes an acyl-CoA desaturase with substrate specificity for C15-C18 acyl groups, in particular C16. Phylogenetic analysis ofRiOLE1-LIKErelated 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 16:1Δ11cisprovides a specific function during AM colonization.