Fatty acid and transcriptome profiling of longissimus dorsi muscles between pig breeds differing in meat quality.

Fat and lean pig breeds show obvious differences in meat quality characteristics including the fatty acid composition of muscle. However, the molecular mechanism underlying these phenotypes differences remains unknown. This study compared meat quality traits between Lantang (a Chinese indigenous breed) and Landrace (a typical lean breed). The Lantang pigs showed higher L* values and intramuscular fat content, lower pH(45min), pH(24h) and shear force in longissimus dorsi (LD) muscle than Landrace (P < 0.05). Fatty acid analysis demonstrated the lower monounsaturated fatty acids (MUFA) and higher polyunsaturated fatty acids (PUFA) percentage in Lantang LD than that in Landrace LD (P < 0.05). To further identify candidate genes for fatty acid composition, the transcriptome of LD muscle from the two breeds were measured by microarrays. There were 586 transcripts differentially expressed, of which 267 transcripts were highly expressed in Lantang pigs. After the validation by real-time quantitative PCR, 13 genes were determined as candidate genes for fatty acid composition of muscle, including Stearoyl-CoA desaturase (SCD). Then, a SCD over-expression plasmid was transfected into C2C12 cells to reveal the effect of SCD on the fatty acid composition in vitro. The results showed that SCD over-expression significantly increased PUFA proportion, while reduced that of saturated fatty acids (SFA) in C2C12 cells (P < 0.05). In summary, this study compared the differences of fatty acid composition and transcriptome in two breeds differing in meat quality, and further identified the novel role of SCD in the regulation of PUFA deposition.

Yu K ，Shu G ，Yuan F ，Zhu X ，Gao P ，Wang S ，Wang L ，Xi Q ，Zhang S ，Zhang Y ，Li Y ，Wu T ，Yuan L ，Jiang Q ... -  《International Journal of Biological Sciences》

Longissimus dorsi muscle transcriptomic analysis of Yunling and Chinese simmental cattle differing in intramuscular fat content and fatty acid composition.

Intramuscular fat (IMF) content and fatty acid (FA) composition vary significantly across beef cattle breeds, which play an important role in taste and nutritional value. However, the molecular mechanisms underlying these phenotypic differences remain unknown. The present study compared meat quality traits between Yunling cattle and Chinese Simmental cattle. Yunling cattle showed a lower IMF content and proportion of monounsaturated fatty acids (MUFA), as well as higher proportions of saturated fatty acids (SFA), polyunsaturated fatty acids (PUFA), and short-chain fatty acids (sc-FA) in the longissimus dorsi (LD) muscle than Chinese Simmental cattle. To further identify the candidate genes and pathways responsible for these phenotypic differences, the transcriptome of LD muscle from the two breeds were measured using RNA-seq. A total of 1347 differentially expressed genes were identified. The major metabolic pathways that were differentially modulated were lipolysis and glycometabolism. Yunling cattle showed a higher expression of lipolysis genes (ALDH9A1, ACSL5, ACADM, ACAT2, ACOT2) and a lower expression of genes related to glycometabolism (PGM1, GALM, PGM1, GPI, LDHA). This research identified candidate genes and pathways for IMF content and FA composition in the LD muscle of beef cattle, which may facilitate the design of new selection strategies to improve meat quality.

Zhang HM ，Xia HL ，Jiang HR ，Mao YJ ，Qu KX ，Huang BZ ，Gong YC ，Yang ZP ... -  《-》

Transcriptome analysis in comparing carcass and meat quality traits of Jiaxing Black Pig and Duroc × Duroc × Berkshire × Jiaxing Black Pig crosses.

This study compares two typical strains: Chinese local excellent meat quality of Jiaxing Black (JXB) Pig and quadratic crossbred pig strain Duroc × Duroc × Berkshire × Jiaxing Black (DDBJ). It was found that between the two pig strains, carcass traits and meat quality traits differed significantly. This is exemplified by the leanness and dressing out percent of DDBJ that were significantly higher than JXB pigs of the same age (P < 0.05) and the better growth rate of DDBJ pigs as to JXB pigs was shown by quantifying muscle proliferation and differentiation of longissimus dorsi muscle employing Hematoxylin and Eosin staining of longissimus dorsi muscle. Nutrients such as inosinic acid, intramuscular fat, and free amino acids in the longissimus dorsi muscle were significantly higher in JXB pigs than DDBJ pigs (p < 0.0001); saturated fatty acids were higher in JXB than in DDBJ pigs (p = 0.0097); essential amino acids and fresh taste amino acids (serine, glutamic acid, proline, glycine, alanine) of JXB pigs was higher than that of DDBJ pigs (p < 0.0001) and amino acids in longissimus dorsi muscle of JXB pigs surpasses the amino acid concentration of DDBJ pigs (p < 0.0001), thus showing the superiority of JXB in terms of meat quality. However, the content of polyunsaturated fatty acids, which is responsible for poor meat quality, was significantly higher in the longissimus dorsi muscle of DDBJ pig than JXB pigs (p < 0.0001); RNA-seq analysis of 5 biological replicates from two of the strains was performed. The screening of 164 up-regulated genes and 183 down-regulated genes found in longissimus dorsi muscle of DDBJ was done and the results identified differentially expressed genes related to muscle development, adipogenesis, amino acid metabolism, fatty acid metabolism and inosine synthesis. In conclusion, the study identified functional genes, elucidated the mechanisms associated with carcass quality traits, meat quality traits and other related traits, and provided means of genetic enhancement to improve meat quality traits and carcass traits in Chinese commercial pigs.

Chen Q ，Zhang W ，Cai J ，Ni Y ，Xiao L ，Zhang J ... -  《-》

Comparative transcriptome analysis of longissimus dorsi muscle reveal potential genes affecting meat trait in Chinese indigenous Xiang pig.

In this study, we compared the transcriptome of longissimus dorsi muscle between Guizhou Xiang pigs (XP) and Western commercial Large White pigs (LW), which show diffirent meat quality between them. In terms of meat quality traits, the pH 45 min, color score, backfat thickness, and intramuscular fat (IMF) content were higher in Xiang pigs than in Large White pigs (P < 0.01), while the drip loss, lean meat percentage, shear force, and longissimus dorsi muscle area of Xiang pigs were lower than that of Large White pigs (P < 0.01). Nutrients such as monounsaturated fatty acid (MUFA), total amino acids (TAA), delicious amino acids (DAA) and essential amino acids (EAA) in Xiang pigs were higher than that in Large White pigs, and the proportion of polyunsaturated fatty acid (PUFA) of Xiang pigs was significantly lower than Large White pigs (P < 0.01). Transcriptome analysis identified 163 up-regulated genes and 88 genes down-regulated in Xiang pigs longissimus dorsi muscle. Combined with the correlation analysis and quantitative trait locis (QTLs) affecting meat quality, a total of 227 DEGs were screened to be significantly associated with meat quality values. Enrichment analysis indicated that numerous members of genes were gathered in muscle development, adipogenesis, amino acid metabolism, fatty acid metabolism and synthesis. Of those, 29 genes were identified to be hub genes that might be related with the meat quality of Xiang pig, such as MYOD1, ACTB, ASNS, FOXO1, ARG2, SLC2A4, PLIN2, and SCD. Thus, we screened and identified the potential functional genes for the formation of meat quality in Xiang pigs, which provides a corresponding theoretical basis for the study of the molecular regulatory mechanism of pork quality and the improvement of pork quality.

Wang W ，Wang D ，Zhang X ，Liu X ，Niu X ，Li S ，Huang S ，Ran X ，Wang J ... -  《Scientific Reports》

Distinctive genes determine different intramuscular fat and muscle fiber ratios of the longissimus dorsi muscles in Jinhua and landrace pigs.

Meat quality is determined by properties such as carcass color, tenderness and drip loss. These properties are closely associated with meat composition, which includes the types of muscle fiber and content of intramuscular fat (IMF). Muscle fibers are the main contributors to meat mass, while IMF not only contributes to the sensory properties but also to the plethora of physical, chemical and technological properties of meat. However, little is known about the molecular mechanisms that determine meat composition in different pig breeds. In this report we show that Jinhua pigs, a Chinese breed, contains much higher levels of IMF than do Landrace pigs, a Danish breed. We analyzed global gene expression profiles in the longissimus dorsi muscles in Jinhua and Landrace breeds at the ages of 30, 90 and 150 days. Cross-comparison analysis revealed that genes that regulate fatty acid biosynthesis (e.g., fatty acid synthase and stearoyl-CoA desaturase) are expressed at higher levels in Jinhua pigs whereas those that regulate myogenesis (e.g., myogenic factor 6 and forkhead box O1) are expressed at higher levels in Landrace pigs. Among those genes which are highly expressed in Jinhua pigs at 90 days (d90), we identified a novel gene porcine FLJ36031 (pFLJ), which functions as a positive regulator of fat deposition in cultured intramuscular adipocytes. In summary, our data showed that the up-regulation of fatty acid biosynthesis regulatory genes such as pFLJ and myogenesis inhibitory genes such as myostatin in the longissimus dorsi muscles of Jinhua pigs could explain why this local breed produces meat with high levels of IMF.

Wu T ，Zhang Z ，Yuan Z ，Lo LJ ，Chen J ，Wang Y ，Peng J ... -  《PLoS One》