Involvement of a bifunctional fatty-acyl desaturase in the biosynthesis of the silkmoth, Bombyx mori , sex pheromone

Abstract

The straight-chain C10 to C18 unsaturated aliphatic compounds containing an oxygenated functional group (aldehyde, alcohol, or acetate ester) derived from saturated C 16 or C18 fatty acids are a major class of sex pheromone components produced by female moths. In the biosynthesis of these pheromone components, various combinations of limited chain-shortening and regio-and stereospecific desaturation reactions significantly contribute to the production of a vast number of the species-specific pheromone components in Lepidoptera. Biosynthesis of the silkmoth sex pheromone bombykol, (E,Z)-10,12-hexadecadien-1-ol, involves two consecutive desaturation steps, the second of which is unique in that it generates a conjugated diene system from the ⌬11-monoene C 16 intermediate. In experiments designed to characterize the acyl-CoA desaturases responsible for bombykol biosynthesis, we have cloned three cDNAs encoding desaturase family members from the pheromone gland of the inbred strain of the silkmoth, Bombyx mori. Transcript analyses by RT-PCR and subsequent functional assays using a Bac-to-Bac baculovirus expression system revealed that desat1 is the only desaturase gene prominently expressed during pheromonogenesis and that its gene product, B. mori Desat1, possesses both Z11 desaturation and ⌬10,12-desaturation activities. Consequently, we have concluded that B. mori Desat1 is not only a bifunctional desaturase involved in bombykol biosynthesis but that it is also the enzyme responsible for both desaturation steps.

A multifunctional desaturase involved in the biosynthesis of the processionary moth sex pheromone

“…Likewise, another bifunctional desaturase/acetylenase enzyme has been reported in the moss C. purpureus (20,29). Bifunctional desaturases are not unusual in insects, as exemplified by the ⌬ 11 /⌬ 10,12 desaturases of B. mori (9) and S. littoralis (19). However, the case of the Tpi-PGFAD is unique because it exhibits not only dual ⌬ 11 /⌬ 13 desaturase activity, but also acetylenase activity, thus constituting a remarkable example of evolution of complex enzymatic activities to generate natural products in the most economical manner for the cell.…”

“…The desaturases expressed in female sex-pheromone glands of different moth species have evolved to play a key role in the biosynthesis of sex pheromones, exhibiting an amazing diversity of substrate and regio-and stereospecifities. Unlike the metabolic ⌬ 9 acyl-CoA desaturases, pheromone gland desaturases catalyze the formation of uncommon unsaturated fatty acyl-CoA esters with variable chain lengths, different locations of unsaturations, and either the ordinary Z or the unusual E double bond geometry (3)(4)(5)(6)(7)(8)(9)(10).…”

“…Cloned desaturases specifically involved in sex pheromone biosynthesis with unusual regiospecificities include the ⌬ 14 desaturase of Ostrinia species (18), the ⌬ 10 desaturase of Planotortrix octo (3), and the bifunctional desaturases of Bombyx mori (9) and Spodoptera littoralis (10,19). Because of the unique chemical structure of its sex pheromone, cloning the acyl-CoA desaturases from T. pityocampa pheromone gland might uncover new desaturases with activities, like ⌬ 11 acetylenase and ⌬ 13 desaturase, so far unreported in the Animal Kingdom.…”

Bombyx mori Homologs of STIM1 and Orai1 Are Essential Components of the Signal Transduction Cascade That Regulates Sex Pheromone Production

“…Transcripts encoding proteins essential to silkmoth sex pheromone production have been shown to be PG specific and undergo up-regulation in the day preceding adult emergence from the pupal stage (8,27,28). To examine the expression profile of BmSTIM1, reverse transcriptase-PCR analyses were performed using primer pairs designed to amplify the entire ORF.…”

An epoxide hydrolase involved in the biosynthesis of an insect sex attractant and its use to localize the production site

“…Other approaches studied the endocrine regulation of pheromone biosynthesis (8,12) and aimed at the characterization of biosynthetic enzymes (4,5,13). The tremendous progress of molecular methods during the past years and the availability of genome sequences of various model organisms shifted the interests of researchers more and more toward the genes involved in pheromone biosynthesis (14)(15)(16)(17)(18)(19)(20). Particularly, the use of RNA interference (RNAi)-mediated gene silencing and in situ RT-PCR has demonstrated the usefulness of these cutting edge tools for insect pheromone research, because they allow both the unequivocal assignment of gene function in vivo and cell localization of biosynthetic pathways within the organism (21)(22)(23).…”