Department of Animal Production and Technology, Faculty of Animal Science, Bogor Agricultural University, 16680 Bogor, Indonesia.
School of Veterinary Science, University of Queensland, Gatton Campus, QLD 4343, Australia; Faculty of Veterinary Science, Bangladesh Agricultural University, 2202, Bangladesh.
Gene. 2018 Nov 15;676:86-94. doi: 10.1016/j.gene.2018.06.086. Epub 2018 Jun 27.
Mutton consumption is less popular in many Asian countries including Indonesia, whose consumers often complain about the unpleasant flavour and odour of the meat. The main causes of mutton odour are the two compounds of branched chain fatty acid (BCFA): methylnonanoic (MNA), phenol, 3-methyl (MP), 4-methylnonanoic (MNA) and 4-ethyloctanoic (EOA) present in all the adipose tissue; and the 3-methylindole (MI) or skatole and indole, which are originated from pastoral diets. It is crucial to understand the genetic mechanism of mutton odour and flavour (MOF) to select sheep for lower BCFA and indole thus reduce the unpleasant flavour of meat. The aim of the present study was to investigate transcriptome profiling in liver tissue with divergent MOF using RNA deep sequencing. Liver tissues from higher (n = 3) and lower (n = 3) MOF sheep were analysed using Illumina HiSeq 2500. The total number of reads produced for each liver sample ranged from 21.37 to 25.37 million. Approximately 103 genes were differentially expressed (DEGs) with significance level of p-adjusted value <0.05. Among them, 60 genes were up-regulated, and 43 were down-regulated (p < 0.01, FC > 1.5) in higher MOF group. Differentially regulated genes in high MOF liver samples were enriched in biological processes such as cellular response to chemical stimulus and endogenous stimulus; cellular components such as such as basement membrane and extracellular matrix; and molecular functions such as haeme binding and oxidoreductase activity. Among the DEGs, metabolic phase I related genes belonging to the cytochrome P450 CYP2A6 were dominantly expressed. Additionally, phase II conjugation genes including UDP glucuronosyltransferases UGT2B18, sulfotransferase SULT1C1, and glutathione S-transferase GSTM1 were identified. The dominant candidate genes for SOF could be cytochrome P450, sodium-channel protein, transmembrane protein, glutathione transferase, UDP glucuronosyltransferases and sulfotransferase. Pathway analysis identified steroid hormone biosynthesis and chemical carcinogenesis by cytochrome P450 pathways which may play important roles in MOF-related molecules metabolism. This work highlighted potential genes and gene-networks that may affect meat off flavour and odour in sheep.
羊肉在包括印度尼西亚在内的许多亚洲国家的消费并不流行，这些国家的消费者经常抱怨羊肉的异味。羊肉异味的主要原因是支链脂肪酸（BCFA）的两种化合物：甲基壬酸（MNA）、苯酚、3-甲基（MP）、4-甲基壬酸（MNA）和 4-乙氧基辛酸（EOA），它们存在于所有脂肪组织中；以及 3-甲基吲哚（MI）或粪臭素和吲哚，它们来自放牧饮食。了解羊肉气味和风味（MOF）的遗传机制对于选择支链脂肪酸和吲哚含量较低的绵羊以降低肉的不良风味至关重要。本研究的目的是使用 RNA 深度测序研究肝脏组织中具有不同 MOF 的转录组谱。使用 Illumina HiSeq 2500 分析了 MOF 较高（n=3）和较低（n=3）的绵羊的肝组织。每个肝样本的总读取数范围为 2137 到 2537 万。大约有 103 个基因表现出差异表达（DEGs），其调整后的 p 值<0.05。其中，60 个基因上调，43 个基因下调（p<0.01，FC>1.5）在较高的 MOF 组。在高 MOF 肝样品中差异调节的基因在生物过程中富集，如细胞对化学刺激和内源性刺激的反应；细胞成分如基底膜和细胞外基质；以及分子功能如血红素结合和氧化还原酶活性。在 DEGs 中，属于细胞色素 P450 CYP2A6 的代谢 I 相相关基因表达占主导地位。此外，还鉴定了包括 UDP 葡糖醛酸基转移酶 UGT2B18、磺基转移酶 SULT1C1 和谷胱甘肽 S-转移酶 GSTM1 在内的 II 相结合基因。SOF 的主要候选基因可能是细胞色素 P450、钠通道蛋白、跨膜蛋白、谷胱甘肽转移酶、UDP 葡糖醛酸基转移酶和磺基转移酶。途径分析确定了细胞色素 P450 途径的甾体激素生物合成和化学致癌作用，这可能在 MOF 相关分子代谢中发挥重要作用。这项工作突出了可能影响绵羊肉质异味和气味的潜在基因和基因网络。
