A comparative study of sex pheromone biosynthesis in two strains of the turnip moth, Agrotis segetum, producing different ratios of sex pheromone components

Abstract

Among the sex pheromone components of the turnip moth, Agrotis segetum, (Z)-5-decenyl acetate, (Z)-7-dodecenyl acetate and (Z)-9-tetradecenyl acetate are biosynthetically derived from palmitic acid by Δ11-desaturation, chain-shortening, reduction and acetylation. Females of a Zimbabwean population produce the three components in a 78:20:2 ratio, while Swedish females produce the three components in a 12:59:29 ratio. We found that the titers of primary pheromone precursors, such as 16:Acyl and Z11-16:Acyl, did not differ significantly between the two populations. However, the amounts of intermediate precursors Z5-10:Acyl, Z7-12:Acyl and Z9-14:Acyl were significantly higher in the Swedish female extracts. There was no obvious correlation between the ratios of pheromone precursors and the ratios of pheromone components. By application of D 3-16:COOH, D 9-Z11-16:COOH, D 9-Z9-14:COOH and D 9-Z7-12:COOH to the female pheromone glands, we found that Zimbabwean females produced more labelled D 9-Z5-10:OAc than Swedish females. In contrast, in Swedish females, the labelled precursors were mainly converted to D 9-Z9-14:OAc and D 9-Z7-12:OAc, rather than to D 9-Z5-10:OAc. Moreover, the conversion rate of D 9-Z5-10:COOH to D 9-Z5-10:OAc, was significantly higher in Zimbabwean females than in Swedish females. Our results indicate that differences in chain shortening and/or the preferential reduction of acids with different chain lengths may lead to the production of different ratios. Brain-SOG homogenates from the two populations increased the pheromone production of decapitated females of both populations, but did not change the pheromone ratios of the two populations.