Iridoid Sex Pheromone Biosynthesis in Aphids Mimics Iridoid‐Producing Plants.

Biosynthesis of (1R,4aS,7S,7aR)‐nepetalactol (1) and (4aS,7S,7aR)‐nepetalactone (2) in plants involves iridoid synthase (ISY), an atypical reductive cyclase that catalyses the reduction of 8‐oxogeranial into the reactive enol of (S)‐8‐oxocitronellal, and cyclization of this enol intermediate, either non‐enzymatically or by a nepetalactol‐related short chain dehydrogenase enzyme (NEPS) that yields the nepetalactols. In this study, we investigated the biosynthesis in vivo of 1 and 2 in the pea aphid, Acyrthosiphon pisum, using a library of isotopically‐labelled monoterpenoids as molecular probes. Topical application of deuterium‐labelled probes synthesized from geraniol and nerol resulted in production of 2H4−lactol 1 and 2H4−lactone 2. However, deuterium incorporation was not evident using labelled probes synthesized from (S)‐citronellol. These results suggest that iridoid biosynthesis in animals, specifically aphids, may follow a broadly similar route to that characterised for plants. [ABSTRACT FROM AUTHOR]