Abstract
Gayal and yak are well adapted to their local high-altitude environments, yet the transcriptional regulation difference of the plateau environment among them remains obscure. Herein, cross-tissue and cross-species comparative transcriptome analyses were performed for the six hypoxia-sensitive tissues from gayal, yak, and cattle. Gene expression profiles for all single-copy orthologous genes showed tissue-specific expression patterns. By differential expression analysis, we identified 3,020 and 1,995 differentially expressed genes (DEGs) in at least one tissue of gayal vs. cattle and yak vs. cattle, respectively. Notably, we found that the adaptability of the gayal to the alpine canyon environment is highly similar to the yak living in the Qinghai-Tibet Plateau, such as promoting red blood cell development, angiogenesis, reducing blood coagulation, immune system activation, and energy metabolism shifts from fatty acid β-oxidation to glycolysis. By further analyzing the common and unique DEGs in the six tissues, we also found that numerous expressed regulatory genes related to these functions are unique in the gayal and yak, which may play important roles in adapting to the corresponding high-altitude environment. Combined with WGCNA analysis, we found that UQCRC1 and COX5A are the shared differentially expressed hub genes related to the energy supply of myocardial contraction in the heart-related modules of gayal and yak, and CAPS is a shared differential hub gene among the hub genes of the lung-related module, which is related to pulmonary artery smooth muscle contraction. Additionally, EDN3 is the unique differentially expressed hub gene related to the tracheal epithelium and pulmonary vasoconstriction in the lung of gayal. CHRM2 is a unique differentially expressed hub gene that was identified in the heart of yak, which has an important role in the autonomous regulation of the heart. These results provide a basis for further understanding the complex transcriptome expression pattern and the regulatory mechanism of high-altitude domestication of gayal and yak.
Highlights
Species living at high altitudes are exposed to strict selection pressures and physiological challenges owning to harsh environmental conditions, such as thin air, cold temperatures, ultraviolet exposure, and low pressure (Miao et al, 2015)
We found that the expression of the kininogen 1 (KNG1) gene was down-regulated by 2.46 times in the lung of yak, while downregulated by 12.39- and 7.38-fold in the heart of gayal and yak than that of lowland cattle, respectively
We found that the gene expression of TPI1 was upregulated in all tissues of both gayal and yak, and G6PC was down-regulated in three tissues of both gayal and yak, which is conducive to the production of ATP through strengthened glycolysis and reduced gluconeogenesis
Summary
Species living at high altitudes are exposed to strict selection pressures and physiological challenges owning to harsh environmental conditions, such as thin air, cold temperatures, ultraviolet exposure, and low pressure (Miao et al, 2015). Numerous species including Tibetans (Ge et al, 2012; Tashi et al, 2014), Tibetan pigs (Jia et al, 2016; Zhang B. et al, 2017), Tibetan sheep (Zhang et al, 2013), Tibetan chickens (Gou et al, 2014), and yak (Qiu et al, 2012; Qi et al, 2019) have evolved unique physiological characteristics, such as superior blood oxygen transport systems and high metabolic efficiency, to adapt to the harsh living pressure (Lan et al, 2018). A thorough understanding of the genetic basis of the physiological characteristics in gayal and yak will provide insight into their adaptation to the high-altitude environment
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