Key biosynthetic gene subfamily recruited for pheromone production prior to the extensive radiation of Lepidoptera

Abstract

BackgroundMoths have evolved highly successful mating systems, relying on species-specific mixtures of sex pheromone components for long-distance mate communication. Acyl-CoA desaturases are key enzymes in the biosynthesis of these compounds and to a large extent they account for the great diversity of pheromone structures in Lepidoptera. A novel desaturase gene subfamily that displays Δ11 catalytic activities has been highlighted to account for most of the unique pheromone signatures of the taxonomically advanced ditrysian species. To assess the mechanisms driving pheromone evolution, information is needed about the signalling machinery of primitive moths. The currant shoot borer, Lampronia capitella, is the sole reported primitive non-ditrysian moth known to use unsaturated fatty-acid derivatives as sex-pheromone. By combining biochemical and molecular approaches we elucidated the biosynthesis paths of its main pheromone component, the (Z,Z)-9,11-tetradecadien-1-ol and bring new insights into the time point of the recruitment of the key Δ11-desaturase gene subfamily in moth pheromone biosynthesis.ResultsThe reconstructed evolutionary tree of desaturases evidenced two ditrysian-specific lineages (the Δ11 and Δ9 (18C>16C)) to have orthologs in the primitive moth L. capitella despite being absent in Diptera and other insect genomes. Four acyl-CoA desaturase cDNAs were isolated from the pheromone gland, three of which are related to Δ9-desaturases whereas the fourth cDNA clusters with Δ11-desaturases. We demonstrated that this transcript (Lca-KPVQ) exclusively accounts for both steps of desaturation involved in pheromone biosynthesis. This enzyme possesses a Z11-desaturase activity that allows transforming the palmitate precursor (C16:0) into (Z)-11-hexadecenoic acid and the (Z)-9-tetradecenoic acid into the conjugated intermediate (Z,Z)-9,11-tetradecadienoic acid.ConclusionThe involvement of a single Z11-desaturase in pheromone biosynthesis of a non-ditrysian moth species, supports that the duplication event leading to the origin of the Lepidoptera-specific Δ11-desaturase gene subfamily took place before radiation of ditrysian moths and their divergence from other heteroneuran lineages. Our findings uncover that this novel class of enzymes affords complex combinations of unique unsaturated fatty acyl-moieties of variable chain-lengths, regio- and stereo-specificities since early in moth history and contributes a notable innovation in the early evolution of moth-pheromones.

A Review of Ant Cuticular Hydrocarbons

“…This suggests that the genetic architecture for the production of all hydrocarbons was already present in ancestral ants, and has been maintained throughout their subsequent vast radiation. This parallels the finding that the key biosynthetic gene subfamily used in pheromone production existed prior to the radiation of Lepidoptera (Liénard et al 2008). Although few species currently appear to synthesize this type of complex CHC profiles, a recent study that used high temperature (HT) columns to analyze CHC profiles of two species of tropical ants (Menzel et al 2008) found that Crematogaster modiglianii and Camponotus rufifemur produce 14 methylalkenes, all of which occurred at chain-lengths greater than C 34 .…”

Terminal fatty-acyl-CoA desaturase involved in sex pheromone biosynthesis in the winter moth (Operophtera brumata)

“…Species-specific moth pheromone biosynthetic Δ11-desaturases have likely evolved from the metabolic acyl-CoA Δ9-desaturases (Roelofs and Rooney, 2003;Liénard et al, 2008). They catalyze the formation of uncommon unsaturated fatty-acyl-CoA esters with variable chain lengths, different locations of unsaturations, and either the ordinary Z or the unusual E double bond geometry.…”

Biotechnological potential of insect fatty acid-modifying enzymes

“…Δ12 mFADs have also been identified, but they are involved in primary metabolism during the production of methylene-interrupted PUFAs [31] rather than pheromone biosynthesis. The moth mFADs can also introduce a double bond at the terminal position between the penultimate and ultimate carbon atoms [78,83] and can produce FAs with a system of isolated double bonds [64] or a system of conjugated double bonds [10,65,66,76,79,80,82]. Among the more bizarre desaturation reactions, an mFAD identified in the processionary moth, Thaumetopoea pityocampa, can introduce triple bonds into the FA chains [81], resembling in activity an mFAD described in the plant of Crepis genus [84].…”

“…The FA-derived pheromones are the most common [8], encompassing thousands of compounds and mixtures of compounds [9]. Insect pheromone-biosynthetic enzymes presumably evolved via a divergence of the original functions of the FA-biosynthetic and FA-modifying enzymes participating in insect primary metabolism [10]. The diversification of the pheromone-biosynthetic enzymes likely has been driven by evolutionarily imposed requirements on sex pheromone signal specificity [11,12].…”