Zhang Xueying, Li Fadi, Qin Fang, Li Wanhong, Yue Xiangpeng
State Key Laboratory of Grassland Agro-ecosystems; Key Laboratory of Grassland Livestock Industry Innovation, Ministry of Agriculture and Rural Affairs; Engineering Research Center of Grassland Industry, Ministry of Education; College of Pastoral Agriculture Science and Technology, Lanzhou University, Lanzhou, Gansu, China.
Engineering Laboratory of Sheep Breeding and Reproduction Biotechnology in Gansu Province, Minqin, Gansu, China.
PeerJ. 2020 Oct 8;8:e10105. doi: 10.7717/peerj.10105. eCollection 2020.
Ovine milk is a rich source of bioactive proteins that supports the early growth and development of the newborn lambs. A large number of researches had targeted to the identification of ovine milk fat globule membrane proteins (MFGMPs), caseins (CNs), mastitis milk proteins in past years, but the dynamic change tendency of milk whey proteins during postnatal development has received limited attention. This research aimed to investigate the dynamic changes of ovine milk whey proteins after delivery, and explore the functions of whey proteins on early development of the newborns.
In this research, Hu sheep milk samples were collected from six individuals by manual milking manner, at 0 d, 3 d, 7 d, 14 d, 28 d and 56 d after delivery, respectively. The milk whey proteins were identified and quantified by the isobaric tag for relative and absolute quantification (iTRAQ) coupled with liquid chromatography (LC)-electrospray ionization (ESI) tandem MS (MS/MS) methods. In addition, biological functions of differentially expressed proteins (DEPs) were annotated by Gene Ontology (GO) annotation and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis.
A total of 310 proteins were identified , of which 121 were differentially expressed. In detail, 30 (10 up-regulated and 20 down-regulated), 22 (11 up-regulated and 11 down-regulated), 11 (four up-regulated and seven down-regulated), 11 (eight up-regulated and three down-regulated), 10 (six up-regulated and four down-regulated) DEPs were identified in 3 d vs. 0 d, 7 d vs. 3 d, 14 d vs. 7 d, 28 d vs. 14 d, 56 d vs. 28 d comparison groups, respectively. The GO annotation analysis revealed that biological process principally involved metabolic and biological regulation, the major cellular location were organelle, cell and extracellular region, and the mainly molecular function were binding and catalytic activity. Circadian rhythm, fatty acid biosynthesis and African trypanosomiasis were enriched by KEGG annotation analysis.
The study reveals a comprehensive understanding of Hu sheep milk proteome, suggesting whey proteins change dramatically in early development of newborn lambs, which provide a potential guidance for early weaning of lambs.
羊奶是生物活性蛋白的丰富来源，有助于新生羔羊的早期生长和发育。过去几年，大量研究致力于鉴定羊乳脂肪球膜蛋白（MFGMPs）、酪蛋白（CNs）、乳腺炎乳蛋白，但产后发育过程中乳清蛋白的动态变化趋势受到的关注有限。本研究旨在探讨分娩后羊乳清蛋白的动态变化，并探究乳清蛋白对新生儿早期发育的作用。
本研究中，通过手工挤奶方式从6只湖羊个体中分别采集产后0 d、3 d、7 d、14 d、28 d和56 d的乳样。采用相对和绝对定量等压标签（iTRAQ）结合液相色谱（LC）-电喷雾电离（ESI）串联质谱（MS/MS）方法对乳清蛋白进行鉴定和定量。此外，通过基因本体论（GO）注释和京都基因与基因组百科全书（KEGG）通路富集分析对差异表达蛋白（DEPs）的生物学功能进行注释。
共鉴定出310种蛋白，其中121种差异表达。具体而言，在3 d与0 d、7 d与3 d、14 d与7 d、28 d与14 d以及56 d与28 d的比较组中分别鉴定出30种（10种上调和20种下调）、22种（11种上调和11种下调）、11种（4种上调和7种下调）、11种（8种上调和3种下调）、10种（6种上调和4种下调）差异表达蛋白。GO注释分析表明，生物学过程主要涉及代谢和生物调节，主要细胞定位为细胞器、细胞和细胞外区域，主要分子功能为结合和催化活性。KEGG注释分析富集了昼夜节律、脂肪酸生物合成和非洲锥虫病。
该研究全面了解了湖羊乳蛋白质组，表明乳清蛋白在新生羔羊早期发育过程中变化显著，为羔羊早期断奶提供了潜在指导。
