Abstract
The yak is a valuable species in the Qinghai-Tibet Plateau of China. Nevertheless, the molecular mechanisms underlying its adaptation to high-altitude environments remain largely unknown. In the present study, comparative transcriptome sequencing was performed for lung and gluteus tissues from two species of low-altitude cattle (Sanjiang and Holstein cattle), Tibetan cattle (living at a moderate altitude), and yak (living at a high altitude) and the differentially expressed genes were validated using real-time quantitative PCR. The results showed that CD36 antigen was up-regulated and CD59 antigen was down-regulated in yak in comparison to the other animals, which might promote the development of red blood cells and inhibit the development of lymphocytes in yak. In addition, thrombospondin type 1, coagulation factor 5/8, and fibronectin were all down-regulated, but serpin and alpha 2-macroglobulin (A2M) were up-regulated. These differences would inhibit blood coagulation, thus reducing the risk of pulmonary edema. The expression levels of the calcium-release, potassium, and transient receptor potential channels decreased in yak, minimizing membrane depolarization and the harmful effects of pulmonary edema. Eleven KEGG pathways associated with innate immunity were more activated in yak and Tibetan cattle than in other cattle strains, which should reduce their risk of infection and disease. These changes together might facilitate the adaptation of yak and Tibetan cattle to live in high-altitude habitats.
Highlights
The Qinghai-Tibet Plateau in China is one of the harshest places for animals to live, with an average altitude higher than 4000 m, an average air temperature below 10 °C, and an oxygen concentration of only 50–60% of normal values
Endogenous purine derivative excretion, average daily urinary N excretion, fasting daily urinary N excretion, and daily glomerular filtration rates were all lower in yak than in cattle, suggesting that they may have developed special regulating mechanisms in kidney and N metabolism[6,7]
Transcriptome comparisons between the lung, heart, liver, and kidney of cattle and yak showed that blood supply system, modulation of cardiac contractility, vascular smooth muscle proliferation, and the glutamate receptor system were all likely to be regulated for yak adaptation[10]
Summary
Total RNA was extracted using Biozol reagent (Bioer, Hangzhou, China), according to the manufacturer’s protocol. ® NanoPhotometer spectrophotometer (IMPLEN, CA, USA) and RNA nano 6000 assay kit on Agilent Bioanalyzer. In order to construct sequencing libraries, 3 μg of total RNA was treated with the Epicentre Ribo-zeroTM rRNA removal kit (Epicentre, USA) to remove ribosomal RNA and was harvested by ethanol precipitation. ® ® sequencing libraries were prepared using NEBNext UltraTM directional RNA library prep kit for Illumina (NEB, USA). The relative expression levels of each gene among different samples were compared using DESeq[2] R package v3.814. To validate the expression levels of DEGs produced by Illumina sequencing, qPCR was performed. All cDNA was prepared using the BioRT cDNA first strand synthesis kit (Bioer, Hangzhou, China) with oligo(dT) primer. The relative expression level of each gene was calculated using the typical 2−ΔΔCt method[17]
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