Functional characterisation of two Δ12-desaturases demonstrates targeted production of linoleic acid as pheromone precursor inNasonia

Abstract

Insect pheromones are often derived from fatty acid metabolism. Fatty acid desaturases, enzymes introducing double bonds into fatty acids, are crucial for the biosynthesis of these chemical signals. Δ12-desaturases catalyse the biosynthesis of linoleic acid by introducing a second double bond into oleic acid, but have been identified in only a few animal species. Here, we report the functional characterisation of two Δ12-desaturases, Nvit_D12a and Nvit_D12b, from the parasitic wasp Nasonia vitripennis. We demonstrate that Nvit_D12a is expressed in the rectal vesicle of males where they produce a linoleic acid-derived sex pheromone to attract virgin females. 13 C-labelling experiments with Urolepis rufipes, a closely related species belonging to the 'Nasonia group', revealed that females, but not males, are able to synthesise linoleic acid. U. rufipes males produce an isoprenoid sex pheromone in the same gland and do not depend on linoleic acid for pheromone production. This suggests that Δ12-desaturases are common in the 'Nasonia group', but acquired a specialised function in chemical communication of those species that use linoleic acid as a pheromone precursor. Phylogenetic analysis suggests that insect Δ12-desaturases have evolved repeatedly from Δ9-desaturases in different insect taxa. Hence, insects have developed a way to produce linoleic acid independent of the omega desaturase subfamily which harbours all of the eukaryotic Δ12-desaturases known so far.

Acetone application for administration of bioactive substances has no negative effects on longevity, fitness, and sexual communication in a parasitic wasp

“…We demonstrated that the sex pheromone of N. giraulti males is produced from linoleic acid. This result confirms previous studies with the congeneric species N. vitripennis [52,53] and demonstrates that acetone application is a suitable and convenient tool to study biosynthetic pathways.…”

“…Both lactones are derived from fatty acid metabolism. 13 C labeling experiments have revealed that linoleic acid is a key intermediate in the pheromone biosynthesis of N. vitripennis while the other Nasonia species have not yet been studied in this respect [52][53][54]. Another aspect of the pheromone biosynthesis in Nasonia that has not yet been studied is the role of insect hormones such as juvenile hormone (JH) and 20-hydroxyecdysone (20-OH-E) which have been found to trigger pheromone biosynthesis in several other insect taxa [13,14,17,[55][56][57].…”

Parasitic wasps do not lack lipogenesis

“…In samples from Ld, Ac, Ct, Hh, Te, and Nv, the respective isotope clusters were also detectable in the methyl esters of the unsaturated fatty acids oleic acid and linoleic acid (Figs. S4, S5 in the supplementary material) demonstrating that 13 C-labeled stearic acid had been processed by Δ9- and Δ12-desaturares [37].…”

Chemical Ecology of the Parasitoid Wasp Genus Nasonia (Hymenoptera, Pteromalidae)

“…Recent studies on the pheromone biosynthesis revealed that Nv has a 12-desaturase enabling them to synthesize LA from oleic acid (OA; Blaul et al, 2014;Semmelmann et al, 2019b; see Figure 3). Wang et al (2015) found a predicted desaturase gene Nasvi2EG017727 to be 800-fold higher expressed in Nv males while a highly similar paralogue was expressed unbiasedly in both males and females.…”

“…that both have in fact 12-desaturase activity. However, only Nvit_D12a was found to be expressed in the male pheromone gland suggesting that it acquired a specialized function in Nv for the production of LA as a pheromone precursor (Semmelmann et al, 2019b). The fact that Nv males are capable of synthesizing LA by themselves challenged the postulated importance of LA as a limited resource.…”