Fatty acyl pheromone analogue-containing lipids and their roles in sex pheromone biosynthesis in the lightbrown apple moth, Epipyhas postvittana (Walker)

The pheromone gland of the moth Epiphyas postvittana was analysed for lipids containing the fatty acyl pheromone analogue (FAPA) of the component, (E)-11-tetradecenyl acetate. The FAPA was found predominantly in the triglycerides (TGs), and to a lesser extent in the choline phosphatides. The FAPA was found to be exclusively on the sn-1 or sn-3 position (probably the latter) of the TGs. When pheromone gland lipid extracts were eluted through silica solid phase extraction, a significant proportion of the FAPA was not recovered. Changes in titre of this non-recoverable FAPA paralleled changes in pheromone titre in females. In contrast, changes in recoverable FAPA (mostly in the TGs) titre showed a gradual increase with time after eclosion. The properties of this non-recoverable FAPA were consistent with it being the CoA ester of the FAPA. Thus, it appears that the FAPA-CoA ester is the immediate lipid precursor of the pheromone, and that the FAPA-containing TGs are formed by reaction of the FAPA-CoA with 1,2-DGs, as a consequence of the rate-limiting reduction of the FAPA-CoA. Finally, injection of PBAN into females decapitated for 3 days resulted in a decrease in recoverable FAPA and an increase in non-recoverable FAPA, suggesting that PBAN influences the lipolysis of TGs. Overall these data suggest that there are two routes for biosynthesis of the pheromone component E11-14:OAc in E. postvittana: a de novo route, directly via the CoA esters of the various fatty acid intermediates, and a less direct route via the lipolysis of FAPA-containing TGs.