Understanding the role of myoglobin content in Iberian pigs fattened in an extensive system through analysis of the transcriptome profile

Meat color is the first perceived sensory feature and one of the most important quality traits. Myoglobin is the main pigment in meat, giving its characteristic cherry-red color which is highly appreciated by consumers. In the current study, we used the RNA-seq technique to characterize the longissimus dorsi muscle transcriptome in two groups of Iberian pigs with divergent breeding values for myoglobin content. As a result, we identified 57 differentially expressed genes and transcripts (DEG). Moreover, we have validated the RNA-seq expression of a set of genes by qPCR. Functional analyses revealed an enrichment of DEGs in biological process related to oxidation (HBA1), lipid metabolism (ECH1, PLA2G10, PLD2), inflammation (CHST1, CD209, PLA2G10), and immune system (CD209, MX2, LGALS3, LGALS9). The upstream analysis showed a total of five transcription regulatory factors and eight master regulators that could regulate the expression of some DEGs, highlighting SPI1 and MAPK1, since they regulate the expression of DEGs involved in immune defence and inflammatory processes. Iberian pigs with high myoglobin content also showed higher expression of the HBA1 gene and it has been described that both molecules have a protective effect against oxidative and inflammatory processes. Therefore, the HBA1 gene is a very promising candidate gene to harbour polymorphisms underlying the myoglobin content, whereby, further studies should be carried out for its potential use in an Iberian pig selection program. Overall design: Twelve Iberian individuals with divergent breeding values for myoglobin content were selected (six per group), samples of Longissimus dorsi were collected after the slaughter, RNA from these samples was extracted, pair-end libraries of 150 bp were constructed