Biosynthesis of 4-methyl-1-nonanol: Female-produced sex pheromone of the yellow mealworm beetle, Tenebrio molitor (Coleoptera : Tenebrionidae)

The objective of this study was to elucidate the biosynthetic route to 4-me thyl-1-nonanol, the female-produced sex pheromone of the yellow mealworm be etle, Tenebrio molitor L. The biosynthetic route to the pheromone was exami ned by (i) allowing the females to feed on defatted bran coated with a stab le isotope-labeled putative precursor ([1-C-13]acetate, [1-C-13]propionate, [1-C-13]pentanoate, [1-C-13]2-methylheptanoic acid, or [H-2(2)]4-methylnon anoic acid); (ii) determining if the precursors were incorporated by analyz ing the emitted pheromone by gas chromatography/selected ion monitoring-mas s spectroscopy (GC/SIM-MS); (iii) where the pheromone was isotopically-enri ched, determining the position of the isotopic label(s) through comparison of the MS fragmentation pattern with that of unlabelled 4-methyl-1-nonanol. Although the incorporation of [1-C-13]acetate into 4-methyl-1-nonanol coul d not be detected, relatively large proportions of the pheromone were produ ced from the other precursors tested: 81% from [H-2(2)]4-methylnonanoic aci d, 45% from [1-C-13]2-methylheptanoic acid, 16% from [1-C-13]pentanoate, an d 35% from [1-C-13]propionate (27% from only one unit, and 7.8% from two un its). The results indicate that 4-methyl-1-nonanol is produced through a mo dification of normal fatty acid biosynthesis: initiation of the pathway wit h one unit of propionate results in the uneven number of carbons in the cha in; incorporation of another unit of propionate during elongation provides the methyl branch; reduction of 4-methylnonanoic acid produces the alcohol pheromone. The elucidation of the biosynthetic pathway of 4-methyl-1-nonano l biosynthesis in the yellow mealworm is the first step towards understandi ng the biochemistry of sex pheromone production in this species. (C) 1999 E lsevier Science Ltd. All rights reserved.