ABSTRACT: Black cattle is a new breed of beef cattle developed by combining modern biotechnologies such as somatic cell cloning and conventional breeding methods. To provide new ideas for improving meat quality and generating new breeds of cattle, the important candidate genes affecting fat deposition in two kinds of cattle were identified. Eighteen months Black cattles and Luxi cattles were randomly assigned into two environmental. The longissimus dorsi muscle were collected on Black cattle and Luxi cattle,for analyses including fatty acid determinationrs, high-throughput sequencing metagenomics, qRT-PCR expression profile and western blot.The ratio of unsaturated fatty acids to saturated fatty acids was 1.37:1 and 1.24:1 in the muscle tissues of Black cattle and Luxi cattle, respectively. The results of RNA-Seq analysis revealed 1,415 DEGs(fold change ≥ ± 2, P<0.05) between the longissimus dorsi of Black cattle and yellow cattle. A total of 939 genes were upregulated, and the other 476 genes were downregulated. With GO enrichment analysis, it was found that the identified DEGs were significantly enriched in biological regulation, regulation of the Wnt signaling pathway, negative regulation of the Wnt signaling pathway, cAMP metabolic process, fat cell differentiation, and brown fat cell differentiation, among other functions. Regulation of lipolysis in adipocytes, AMPK signaling pathway, adipocytokine signaling pathway and PPAR signaling pathway in the KEGG pathway database were significantly enriched. PPI network analysis showed that the downregulated genes FABP4, ADIPOQ, PLIN1, PLIN2 and LIPE were closely linked to other DEGs and were the key sites of multiple metabolic pathways. Combined with qRT-PCR and protein expression profile analysis, the expression level of fat acid metabolism related genes (FABP4, ADIPOQ) in black cattle was high and the difference was significant. Changes in the expression of fatty acid metabolism-related genes in Black cattle and Luxi cattle were analyzed and important candidate marker genes (such as ADIPOQ and FABP4) that affect fat deposition were identified in order to provide a genetic basis for the efficient breeding of production performance, establish a molecular marker database for local cattle breeds and support the cultivation of new breeds.
