The integral role of triacyl glycerols in the biosynthesis of the aldehydic sex pheromones of Manduca sexta (L).

In a gland located near the tip of their abdomens, Manduca sexta females produce a pheromone blend comprised of hexadecanal, (Z)-9-hexadecenal, (Z)- and (E)-11-hexadecenal, (E,Z)- and (E,E)-10,12-hexadecadienal, and (E,E,Z)- and (E,E,E)-10,12,14-hexadecatrienal. These aldehydes are produced and released by evaporation from the surface of the gland only during a discrete period of the night. They are not stored in the gland and are found there only in very small amounts, if at all, during other times of the photoperiod. However, fatty acyl analogues of the pheromone aldehydes are present in the gland in relatively large amounts, primarily as components of triacyl glycerols, continuously from eclosion of the adults until death. The unsaturated components are produced from hexadecanoate, which is desaturated to the monoenes. Then, (Z)-11-hexadecenoate is desaturated and isomerized to form the conjugated dienes and ultimately the conjugated trienes. The fatty acyl precursors of the pheromones, stored as components of triacyl glycerols, are converted into aldehydes by a process triggered by a pheromone biosynthesis activating neuropeptide (PBAN), produced in the brain-subesophageal complex. It is not yet clear whether this conversion involves direct reduction of the acyl groups to aldehydes or reduction to alcohols followed by oxidation to aldehydes.