Functional Fatty Acid Reductases in the ermine moths, Yponomeutidae, and their involvement in pheromone biosynthesis

The three sister species of small ermine moths (Lepidoptera: Yponomeutidae) Yponomeuta evonymellus, Y. padellus and Y. rorellus are distributed sympatrically throughout Europe, and they use various alcohols and acetates as their female sex pheromone (1, 2 ,3). This makes them a suitable group for studying the repertoire of Fatty Acyl Reductases (FARs) involved in the pheromone biosynthesis (4). In pheromone biosynthesis, FARs account for a key step by converting the fatty acyl intermediates into fatty alcohols, which may subsequently be acetylated to form pheromone component acetates. However, the molecular and biochemical properties of these enzymes have not yet been investigated in detail apart from the active FAR reported in the silkworm moth Bombyx mori (5). We have screened the pheromone gland transcriptome of the three species and we isolated several FAR-like homologous sequences. Transcriptional analysis showed that one of the transcripts (FARII) was exclusively expressed in the pheromone gland, suggesting a role in pheromone biosynthesis, whereas the others were present both in the abdomen and pheromone gland tissues. We further investigated the putative FARs by analyzing the functionality and specificity of each ORF enzyme in vitro, and testing the same potential fatty-acid intermediate pheromone precursors for each species. Our results confirmed the involvement of FARII in pheromone biosynthesis and suggest that FARII encodes a unique functional fatty acyl-CoA reductase in all three sister species, whereas the other FAR-like encoded-genes were found to be inactive on each substrate tested.