Early postmortem gene expression and its relationship to composition and quality traits in pig Longissimus dorsi muscle.

An mRNA expression study has been performed in 20- to 25-min postmortem-obtained samples from Longissimus dorsi muscle of 59 Duroc × Landrace/ Large White (LD/LW) pigs to search for gene sequences related to meat quality (pH(24), pH(45), "Lab" color coordinates, curing yield, and exudation at 3 different times) or meat composition [intramuscular fat, content of several fatty acids (C16:0, C18:0, C18:1, and C18:2), ratio of saturated, monounsaturated, and polyunsaturated fatty acids, and protein and humidity contents] traits to find targets for selection. Gene ontology analysis, biological pathway, and gene network studies all show that many more differentially expressed genes (506 vs. 279) are related to meat quality (Group P or perimortem characters) than to meat composition traits (Group L or whole life traits). The difference between the number of gene ontology terms annotated, biological pathways, and gene networks in groups P and L is notable due to the differences in the complexity of the "generation process" of P-traits and involvement of other tissues or organs in the generation of variability of L-traits. Also, interactions between differentially expressed genes were found in extracellular matrix (ECM)-receptor interaction, tumor growth factor (TGF)-beta signaling pathway, fatty acid elongation in mitochondria, and adipocytokine signaling pathway, indicating that a substantial fraction of the gene networks could be associated with interactions between differentially expressed genes related to traits under study. A large number of the most overexpressed genes are related to muscle development and functionality and repair mechanisms; they could be good candidates for breeding programs in which the main goal is to enhance meat quality.