Submitted to: National Entomological Society of America Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 11/12/1998
Publication Date: N/A
Technical Abstract: Sap beetles (Coleoptera: Nitidulidae) of the genus Carpophilus have male-produced aggregation pheromones that are attractive to both males and females. These pheromones typically have multiple components, and these are acyclic hydrocarbons of 12 to 17 carbons with three or four conjugated double bonds and two or three alkyl branches. The alkyl branches are either methyl or ethyl and occur on alternate carbons of the chain. The structures suggested a mixed polyketide origin, and assembly of the pheromones from small organic acid precursors was explored experimentally. A fortunate circumstance was that the beetles tolerated high levels of organic acids in their artificial diet, and free acids labeled either with deuterium or carbon-13 were clearly incorporated into the pheromone molecules. Mass and NMR spectra of the resulting pheromones determined the numbers and locations of the heavy isotope atoms, allowing biosynthetic inferences to be made. All of the pheromone components can be assembled biosynthetically from just acetate, propionate, and butyrate units. Four total units give a triene, and five give a tetraene. Methyl branches are derived from propionate, and ethyl branches are derived from butyrate. The acyl carbon of the final unit in the chain is removed. Pheromone assembly is proposed to be as in typical fatty acid anabolism except that the double-bond reduction step of each cycle does not occur, resulting in the conjugated unsaturated system. The pheromones are made in specialized cells within the abdomen that empty into the tracheal system.