BioProject

The success of turkey breeding for rapid growth rate and larger breast size has coincided with an increasing incidence of a meat quality defect described as pale, soft and exudative (PSE). We hypothesized that this defect, which is associated with an abnormally rapid rate of postmortem metabolism, derives from altered expression of genes involved in metabolic regulation. Our objective was to use deep transcriptome RNA sequence analysis (RNAseq) to identify differentially expressed genes between normal and PSE turkey breasts. Following harvest of turkey breasts (n = 43), the pH at 15 min post-slaughter and percent marinade uptake at 24h post-slaughter were determined. Breast samples were classified as normal or PSE based on marinade uptake (high = normal; low = PSE). Total RNA from samples with the highest (n=4) and lowest (n=4) marinade uptake were isolated and sequenced using the Illumina GAIIX platform. Of 21,340 gene loci discovered by RNAseq, 8480 loci completely matched the turkey reference genome, and 480 genes were differentially expressed (false discovery rate, FDR<0.05) between normal and PSE samples. Two highlights were the genes nephroblastoma overexpressed (NOV), upregulated about 38-fold and pyruvate dehydrogenase kinase isoform 4 (PDK4), downregulated 14-fold in PSE samples. Pathway analysis suggested that several biological functions, including carbohydrate metabolism and energy production, were affected by meat quality. Because PDK4 regulates conversion of pyruvate to acetyl CoA, differences in regulation of oxidative metabolism may exist among turkeys. Accelerated early postmortem metabolism would result in faster pH decline in PSE meat. This hypothesis was supported by the fact that decreased expression of PDK4 was associated with lower pH in PSE samples (pH[PSE] = 5.59±0.09, pH[normal] = 5.77±0.17). The RNAseq results provided a greater molecular mechanistic understanding of development of PSE turkey, which will be a foundation for new intervention strategies to prevent development of this defect. Overall design: The mRNA profiles of normal and PSE turkey breast muscle were generated by deep sequencing using Illumina GAIIx platform. Multiplexing was performed (2 samples/lane). Afterwards, difference in gene expression between normal and PSE samples were tested.