Identification of a Δ11 desaturase from the arbuscular mycorrhizal fungus Rhizophagus irregularis

Abstract

Arbuscular mycorrhizal fungi are oleaginous organisms and the most abundant fatty acyl moiety usually found in their lipids is palmitvaccenic acid (16:1{Delta}11cis). However, it is not known how this uncommon fatty acid species is made. Here we have cloned two homologs of Lepidopteran fatty acyl-CoenzymeA {Delta}11 desaturases from Rhizophagus irregularis. Both DES1 and DES2 are expressed in intraradicle mycelium and can complement the unsaturated fatty acid-requiring auxotrophic growth phenotype of the Saccharomyces cerevisiae ole1{Delta} mutant. DES1 expression leads almost exclusively to oleic acid (18:1{Delta}9cis) production, whereas DES2 expression results in the production of 16:1{Delta}11cis and vaccenic acid (18:1{Delta}11cis). DES2 therefore encodes a {Delta}11 desaturase that is likely to be responsible for the synthesis of 16:1{Delta}11cis in R. irregularis.