Identification of avian wax synthases

Sequence similarities enabled us to identify six cDNAs encoding putative wax synthesizing proteins in chicken and two from barn owl and goose. Expression studies in yeast under in vivo and in vitro conditions showed that three proteins from chicken performed WS activity while a sequence from chicken, goose and barn owl encoded a bifunctional enzyme catalyzing both wax ester and triacylglycerol synthesis. Mono- and bifunctional WS were found to differ in their substrate specificities especially with regard to branched-chain alcohols and acyl-CoA thioesters. According to the expression patterns of their transcripts and the properties of the enzymes, avian WS proteins might not be confined to preen glands.We provide direct evidence that avian preen glands possess both monofunctional and bifunctional WS proteins which have different expression patterns and WS activities with different substrate specificities.Birds preen their feathers with a secretion produced by the uropygial gland, a holocrine bilobular gland located above their tail. The secretion consists of lipids, proteins and salts [1] and varies, for example, among species, age, season and sex [2-7]. These secretions confer different functions regarding sexual attraction, lubrication, waterproofing, antipathogenic effects and plumage maintenance [8-11]. Preen gland waxes show a high diversity of components; some species contain monoacyl esters, others diacyl esters or triacylglycerols (TAG). The distribution of fatty acids and alcohol residues is often unique, especially branched-chain, extremely long-chain or substituted fatty acids can be found here [12]. For instance, the preen gland secretions from chicken (Gallus gallus) consist of 50% wax diesters and 30% TAG [13]. Wax diesters contain erythro- and threo-alkane-2,3-diols with chain-lengths of 21 to 23 carbon atoms and saturated fatty acids of 12 to 20 carbon atoms [13,14]. Diester waxes are detected in other galliform birds as quail or pheasant as well as