ABSTRACT: Intramuscular fat (IMF) content is the determining factor for meat taste. To reveal the genetic basis of IMF content, genetic studies have made some progress in lean-type pig breeds, but fewer studies have been conducted in Chinese fat-type pigs. The Luchuan pig is a fat-type local breed in southern China that is famous for its desirable meat quality. In the present study, we measured the IMF content for 265 crossed pigs of Duroc x Luchuan pigs, from which individuals with extremely high (6.03% ± 0.58%, n = 12) and low (1.67% ± 0.42%, n = 12) IMF contents were selected to identify differentially expressed genes (DEGs) related to IMF content in the longissimus dorsi. RNA sequencing for 24 samples in total identified 312 differentially expressed transcripts that were significantly enriched in triglyceride biosynthesis- and metabolism-related processes (p-value ≤ 0.05 and fold change ≥ 1.5). Functional enrichment analysis revealed that the PPAR signaling pathway was the most significantly enriched pathway (p-value = 0.024, represented by ADIPOQ, FABP3, FABP4, LPL, PLIN4 and SCD). When a more stringent condition was applied (gene-based q-value ≤ 0.2 and fold change ≥ 1.5), only 17 transcripts remained to be differentially expressed, including LEP, ATP6V1F, SDR16C5, TUSC5, MPZ, PRX, PTPN4, BEX1, MVB12B, ZFP62, P4HA2, IDH2, THOC7, KRT14, FCGRT, MYPN and LPL. Among these DEGs, TUSC5 was significantly upregulated in the group of high IMF contents (log2FC = 1.114, p-value = 3.02E-5) and was suspected as a strong new candidate gene affecting porcine IMF content since it was the target gene of PPAR-gamma. The present study provided new data and candidate genes for the genetic study of porcine IMF content.
