Functional analysis of Δ11-desaturase genes involved in the biosynthesis of conjugated pheromone components in primitive and advanced moth species

Lepidopteran female sex pheromones act as long-range attractants for conspecific mates. According to their structure, moth pheromones can be classified into three types: primitive moths (i.e Eriocraniidae) release short chain secondary alcohols and ketones from sternal V glands (type 0); the majority of lepidopteran species release, through a terminal abdominal gland, long chain fatty acid derivatives (12C-18C) comprising an oxygenated terminal group (alcohol, aldehyde and acetate) and 0 to 3 double bonds (type I); among ditrysian species, some (i.e Geometridae) associate FA derivatives with long chain hydrocarbons (type II). This work aims at identifying and characterizing desaturases involved in the pheromone biosynthetic pathways of Dendrolimus punctatus and Lampronia capitella, two moth species phylogenetically highly distant, but sharing the particularity to produce conjugated dienes as main pheromone components. We report the first identification in a primitive moth species of a Δ11-desaturase active in the pheromone biosynthesis of conjugated (Z,Z)-9,11 pheromone components. This enzyme is very similar to other insect Δ11-desaturases. This shows that the Δ11 subfamily evolved before the divergence of Ditrysia and other Heteroneuran lineages. To synthesize its (Z,E)-5,7 conjugated diene pheromone, the highly advanced moth species, D. punctatus relies on two functional Δ11-desaturase genes having similar
substrate and regio-specificities. In conclusion, Δ11-desaturases certainly played a significant role in increasing the structural diversity in pheromone components, thus being involved in sex-pheromone evolution “on the emitter side” and are likely to have favoured lepidopteran species diversity.