Abstract
BackgroundBird species show a high degree of variation in the composition of their preen gland waxes. For instance, galliform birds like chicken contain fatty acid esters of 2,3-alkanediols, while Anseriformes like goose or Strigiformes like barn owl contain wax monoesters in their preen gland secretions. The final biosynthetic step is catalyzed by wax synthases (WS) which have been identified in pro- and eukaryotic organisms.ResultsSequence 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.ConclusionsWe 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.
Highlights
Bird species show a high degree of variation in the composition of their preen gland waxes
Identification of putative wax synthases from avian organisms Sequence similarity based searches conducted with human AWAT1, AWAT2 and DGAT1 sequences as queries against the annotated Gallus gallus proteome resulted in five full-length sequences
Using mRNA isolated from preen glands as starting material, we succeeded in cloning the respective cDNAs of GgWS2 [NCBI: JQ031644], GgWS4 [NCBI: XP_419207.1], GgWS5 [NCBI: NP_0010261921.1] and GgDGAT1 [NCBI: JQ031642], while cDNAs of GgWS1 were synthesized because we failed to amplify the respective full-length sequence
Summary
Bird species show a high degree of variation in the composition of their preen gland waxes. The final biosynthetic step is catalyzed by wax synthases (WS) which have been identified in pro- and eukaryotic organisms. 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 [2,3,4,5,6,7]. The preen gland secretions from chicken (Gallus gallus) consist of 50% wax diesters and 30% TAG [13]. Diester waxes are detected in other galliform birds as quail or pheasant as well as perching
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