Abstract
Background:Boar taint is a major obstacle when using uncastrated male pigs for swine production. One of the main compounds causing this taint is androstenone, a pheromone produced in porcine testis. Here we use microarrays to study the expression of thousands of genes simultaneously in testis of high and low androstenone boars. The study allows identification of genes and pathways associated with elevated androstenone levels, which is essential for recognising potential molecular markers for breeding purposes.Results:Testicular tissue was collected from 60 boars, 30 with extreme high and 30 with extreme low levels of androstenone, from each of the two breeds Duroc and Norwegian Landrace. The samples were hybridised to porcine arrays containing 26,877 cDNA clones, detecting 563 and 160 genes that were differentially expressed (p < 0.01) in Duroc and Norwegian Landrace, respectively. Of these significantly up- and down-regulated clones, 72 were found to be common for the two breeds, suggesting the possibility of both general and breed specific mechanisms in regulation of, or response to androstenone levels in boars. Ten genes were chosen for verification of expression patterns by quantitative real competitive PCR and real-time PCR. As expected, our results point towards steroid hormone metabolism and biosynthesis as important biological processes for the androstenone levels, but other potential pathways were identified as well. Among these were oxidoreductase activity, ferric iron binding, iron ion binding and electron transport activities. Genes belonging to the cytochrome P450 and hydroxysteroid dehydrogenase families were highly up-regulated, in addition to several genes encoding different families of conjugation enzymes. Furthermore, a number of genes encoding transcription factors were found both up- and down-regulated. The high number of clones belonging to ferric iron and iron ion binding suggests an importance of these genes, and the association between these pathways and androstenone levels is not previously described.Conclusion:This study contributes to the understanding of the complex genetic system controlling and responding to androstenone levels in pig testis. The identification of new pathways and genes involved in the biosynthesis and metabolism of androstenone is an important first step towards finding molecular markers to reduce boar taint.
Highlights
Boar taint is a major obstacle when using uncastrated male pigs for swine production
A total of 1533 Norwegian Landrace (NL) boars and 1027 D boars were analysed and average androstenone levels were 1.17 ± 1.15 μg/g and 3.22 ± 2.68 μg/g for NL and D, respectively. 30 high and 30 low androstenone boars were selected from each breed and average values were 5.91 ± 2.41 μg/g for NL high androstenone (NLH), 0.15 ± 0.04 μg/g for NL low androstenone (NLL), 10.27 ± 2.68 μg/g for D high androstenone (DH) and 0.42 ± 0.13 μg/g for D low androstenone (DL)
Our results show an up-regulation of Cytochrome P450 19A2 (CYP19A2) isoform in both NLH and DH boars, whereas the CYP19A1 isoform was up-regulated in DH
Summary
Boar taint is a major obstacle when using uncastrated male pigs for swine production. Production of entire males is a challenge due to boar taint, an unpleasant odour and flavour often present in the meat of un-castrated male pigs [2]. Castration is undesirable both for ethical as well as for economical reasons and alternative methods are needed to prevent tainted meat. Boar taint is primarily caused by high levels of the two components androstenone and/or skatole in the pig carcasses [3,4]. Moderate to high heritabilities have been shown for both androstenone and skatole levels in fat [5,6,7]. A recent study of Duroc and Norwegian Landrace showed heritabilities ranging from 0.5–0.6 for androstenone and 0.23–0.56 for skatole [8]
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