Transcriptional analysis of intramuscular fatty acid composition in the longissimus thoracis muscle of I berian × L andrace back‐crossed pigs

Summary This study aimed at identifying differential gene expression conditional on the fatty acid profile of the longissimus thoracis (Lt) muscle, a prime cut of economic relevance for fresh and cured pork production. A population of 110 Iberian (25%) ×   Landrace (75%) back‐crossed pigs was used, because these two breeds exhibit extreme profiles of intramuscular saturated fatty acid, monounsaturated fatty acid ( MUFA ) and polyunsaturated fatty acid ( PUFA ) contents. Total RNA from Lt muscle was individually hybridized to GeneChip Porcine Genome arrays (Affymetrix). A principal component analysis was performed with data from the 110 animals to select 40 extreme animals based on the total fatty acid profile and the MUFA composition ( MAP ). Comparison of global transcription levels between extreme fatty acid profile pigs ( n  =   40) resulted in 219 differentially expressed probes (false discovery rate <0.10). Gene ontology, pathway and network analysis indicated that animals with higher percentages of PUFA exhibit a shift toward a more oxidative muscular metabolism state, with a raise in mitochondria function ( PPARGC 1A , ATF 2 ), fatty acid uptake and oxidation ( FABP 5 , MGLL ). On the other hand, 87 probes were differentially expressed between MUFA composition groups ( n  =   40; false discovery rate <0.10). In particular, muscles rich in n‐7 MUFA expressed higher levels of genes involved in lipid metabolism ( GLUL , CRAT , PLA 2G15 ) and lower levels of fatty acid elongation genes ( ELOVL 5 ). Moreover, the chromosomal position of FABP 5 , PAQR 3 , MGLL , PPARGC 1A , GLUL and ELOVL 5 co‐localized with very relevant QTL for fat deposition and composition described in the same resource population. This study represents a complementary approach to identifying genes underlying these QTL effects.