International Journal of Molecular Ecology and Conservation, 2025, Vol.15, No.1, 19-29 http://ecoevopublisher.com/index.php/ijmec 21 2.2 Adaptation and genetic basis of high-altitude hypoxia environment In harsh high-altitude environments (such as the Qinghai-Tibet Plateau and the Himalayas), hypoxia (plateau hypoxia) is one of the biggest challenges facing organisms. Goat breeds living on plateaus (such as Tibetan goats) show high tolerance to low oxygen environments and possess a series of physiological adaptations, such as increased erythrocytosis, changes in hemoglobin oxygen affinity, and respiratory metabolic regulation (Zhu et al., 2025). The formation of these adaptations is inseparable from the contribution of genetic factors. One typical example is the variation of the EPAS1 gene (also known as HIF2A). EPAS1 encodes hypoxia-inducible factor 2α, which is the main regulator of the body's response to hypoxia. Studies on goats at different altitudes in Yunnan, China found that a non-synonymous mutation site (Gln556Leu) in the EPAS1 gene was positively selected in high-altitude goats. The higher the altitude, the higher the frequency of the mutant allele. Goats carrying the mutation showed higher red blood cell counts and hemoglobin concentrations at plateaus above 2,500 meters, which helped improve the blood's oxygen-carrying capacity (Zhu et al., 2025). This finding echoes the adaptive mutation of EPAS1 in humans and other plateau mammals, indicating that different species convergently evolve and utilize the same hypoxia sensing pathway genes (Jin et al., 2020; Tiwari et al., 2024). In addition to conventional gene mutations, structural variation also contributes to the adaptation of plateau goats. The latest pan-genome study of goats found that a VNTR sequence was inserted near the PAPSS2 gene on chromosome 6 of goats, and the frequency was significantly increased in plateau populations, which is considered to be related to the high-altitude adaptation of goats. PAPSS2 is involved in the sulfate metabolism pathway, and this structural insertion variation may affect the regulation of the gene, thereby affecting plateau hypoxia or other plateau stresses (Bian et al., 2024). 2.3 Adaptation to drought and high temperature environment and genetic basis The drought and hot environment also poses severe challenges to the survival of goats. In desert and semi-desert areas with scarce water resources, poor vegetation and strong high temperature radiation, local indigenous goat breeds show outstanding characteristics such as heat resistance, drought resistance and roughage tolerance (Silanikove, 2000; Kali̇ber et al., 2016). For example, goat breeds in the arid zone of sub-Saharan Africa can maintain water balance under long-term water shortage conditions, and dissipate heat and cool down through day and night behavior adjustments and skin physiological regulation; some goat breeds in the Middle East and South Asia can tolerate temperatures as high as 40°C and have evolved the ability to feed on juicy and salty plants. The genome comparison of the wild relatives living in desert habitats, the Nubian ibex (actually a wild goat subspecies) and domestic goats, provides important clues. A whole-genome analysis of the endangered Nubian antelope identified 22 positively selected genes involved in a variety of biological functions such as immune response, protein ubiquitination, olfactory transduction, and visual development. Among them, three genes (ABCA12, ASCL4, and UVSSA) are closely related to the development and function of the skin barrier (Chebii et al., 2020). In addition to the skin system, goats' tolerance to high temperatures is also related to metabolic and endocrine regulation. Landscape genomic analysis showed that goat breeds in dry and hot climates showed signs of selection on some genes that control energy metabolism and heat stress response. For example, genes such as PLCβ1, ITPR2, and DENND1A were co-selected in high-temperature environment breeds (Peng et al., 2024a). In addition, heat shock protein (HSP)-related genes play an important role in goat heat tolerance. A study on local Chinese goats reported that several HSP genes were upregulated under high temperature stress conditions, and there were allelic variation differences between breeds. 2.4 Adaptability and genetic basis under severe cold environment and disease pressure In addition to showing adaptability in tropical deserts and plateau environments, goats also survive well in cold environments such as high latitudes and mountains. For example, some goat breeds from Central Asia and Northern Europe can withstand severe cold of dozens of degrees Celsius below zero. These goats usually have dense fur (including developed undercoat) and thick subcutaneous fat to keep warm, and respond to the cold
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