Comparative Transcriptome Analysis of Milk Somatic Cells During Lactation Between Two Intensively Reared Dairy Sheep Breeds

Abstract

In dairy sheep industry, milk production dictates the value of a ewe. Milk production is directly related to the morphology and physiology of the mammary gland; both being designated targets of breeding strategies. Although within a flock breeding parameters are mutual, large differences in milk production among individual ewes are usually observed. In this work, we tested two of the most productive dairy sheep breeds reared intensively in Greece, one local the Chios breed and one foreign the Lacaune breed. We used transcriptome sequencing to reveal molecular mechanisms that render the mammary gland highly productive or not. While highly expressed genes (caseins and major whey protein genes) were common among breeds, differences were observed in differentially expressed genes. ENSOARG00000008077, as a member of ribosomal protein 14 family, together with LPCAT2, CCR3, GPSM2, ZNF131, and ASIP were among the genes significantly differentiating mammary gland’s productivity in high yielding ewes. Gene ontology terms were mainly linked to the inherent transcriptional activity of the mammary gland (GO:0005524, GO:0030552, GO:0016740, GO:0004842), lipid transfer activity (GO:0005319) and innate immunity (GO:0002376, GO:0075528, GO:0002520). In addition, clusters of genes affecting zinc and iron trafficking into mitochondria were highlighted for high yielding ewes (GO:0071294, GO:0010043). Our analyses provide insights into the molecular pathways involved in lactation between ewes of different performances. Results revealed management issues that should be addressed by breeders in order to move toward increased milk yields through selection of the desired phenotypes. Our results will also contribute toward the selection of the most resilient and productive ewes, thus, will strengthen the existing breeding systems against a spectrum of environmental threats.

Identification of candidate genes associated with milk production and mastitis based on transcriptome‐wide association study

“…EPPK1 plays a role in the production of unsaturated fatty acids (Bohlouli et al., 2022). GPSM2 plays an important role in mammary gland productivity in high‐yielding animals (Michailidou et al., 2021). PLEC has been identified as a candidate gene associated with milk, fat, and protein yield, and fat and protein percentage in Holstein cattle (Cai et al., 2020; Jiang, Ma, et al., 2019; Pedrosa et al., 2021).…”

“…DGAT1 encodes an enzyme with an important metabolic role that can convert diacylglycerol and fatty acyl CoA into triacylglycerol. The MGST1 gene plays a role in hydrophobic metabolism, (Morgenstern et al, 2011). This is one of the candidate genes for the milk production trait (Iung et al, 2019;Pedrosa et al, 2021).…”

Review: Research Progress of Dairy Sheep Milk Genes

“…From domestication to the current pattern of differentiation, domestic species have been influenced by lots of factors such as migration, isolation, and introgression; these have resulted in a very large number of sheep breeds across the world [2]. A large quantity of dairy sheep are distributed in Mediterranean and Black Sea regions, so the sheep milk industry is mainly concentrated in parts of Europe, West Asia, and African countries such as France, Greece, Italy, Spain, Israel, Turkey, and so on; some dairy sheep breeds like the East Friesian sheep, Sarda sheep, Lacaune sheep, Latxa sheep, and Assaf sheep are all high producing sheep breeds known to the world [3]. Previous reports showed that sheep milk has higher fat content, protein content, lactose content, ash content, and total non-fat solids, which have higher nutritional value and can be processed into various delicious milk products and by-products.…”