The biosynthesis of Dufour's gland constituents in queens of the honeybee (Apis mellifera)

Chemical analysis of queen Dufour's gland by GC/MS revealed the presence of long chain esters and hydrocarbons. To evaluate whether the biosynthesis of Dufour's gland components is modulated by physiological factors, we studied the de novo biosynthesis of esters and hydrocarbons in virgin and mated queen glands in vivo and in vitro. Using [1-¹⁴C] sodium acetate as a precursor, it was shown that in vivo, esters and hydrocarbons comprised the major de novo products. The relative proportion of the hydrocarbon fraction was significantly higher in mated queens than in virgins, while in esters the situation was reversed. Comparision between reproductive and non reproductive virgin queens revealed that mating and not egg laying induced changes in glandular activity. Glands incubated in vitro, on the other hand, synthesized mainly esters and alcohols but not hydrocarbons. These results suggest that either hydrocarbons are produced elsewhere and subsequently sequestered by Dufour's gland, or that the gland biosynthetic expression in vivo is modulated. Differences between the gland activity in vivo and in vitro further support the hypothesis of a physiological mechanism in regulation of glandular performance.