The Qinghai-Tibet Plateau, known as the "Third Pole" of the Earth, is renowned for its low oxygen, low temperatures, and intense ultraviolet radiation. Yaks migrated to the Qinghai-Tibet Plateau around 3700 years ago, making them one of the earliest domesticated animals to inhabit the region. They represent the oldest and most primitive genetic resources of yaks in China and even globally, serving as a crucial strategic resource for breeding new varieties adapted to the high-altitude environment of China.
However, the current "National Livestock and Poultry Genetic Resources Compendium - Yak Volume" only includes four Tibetan yak breeds, which is significantly inadequate considering the vast geographical diversity of the Qinghai-Tibet Plateau. Therefore, conducting a systematic survey and in-depth exploration of the genetic resources of yaks on the plateau, as well as studying the genetic mechanisms underlying their adaptation to high-altitude environments, is of great significance for the exploration, conservation, and genetic improvement of livestock genetic resources in high-altitude regions.
A team led by Professor Lei Chuzhao from the College of Animal Science and Technology at Northwest A&F University, a specialist in the national beef and yak industry technology system, collaborated with Professor Lv Wenfa's team from Jilin Agricultural University. They conducted the first systematic evaluation of the genetic resources of yaks on the Qinghai-Tibet Plateau using multi-omics technologies. Their findings, titled "Recent Selection and Gene Introgression Jointly Promote Cattle Adaptation to High Altitudes," were published online in the "Science Bulletin" on May 25th, revealing that yak adaptation to the Qinghai-Tibet Plateau is a result of multi-gene effects, involving complex physiological processes to cope with the harsh conditions of cold, low oxygen, low pressure, and intense ultraviolet radiation.
Genomic diversity and high-altitude adaptation of Tibetan yak populations. Author's paper images.
This study systematically evaluated the paternal, maternal, and nuclear genomic levels of eight Tibetan yak populations at altitudes of 3400-4300 meters. It found that the genetic diversity within Tibetan yak populations is very high, with at least five highly differentiated groups, indicating rich local genetic resources with great potential for exploration on the Tibetan Plateau. By utilizing large-scale genomic data and various selection signal analyses, the study identified 160 highly confident selected genes in Tibetan yaks, including 15 newly discovered genes, involving multiple organs and physiological systems. The top three selected genes (HMGA2, NCAPG, and DUOXA2) are associated with body size and energy metabolism in Tibetan yaks. The researchers also observed asymmetric introgression of yak genes at different altitudes, including two important introgression regions on chromosomes 9 and 28, which are related to processes such as hypoxia response (EGLN1), cold adaptation (LRP11), DNA damage repair (LATS1), and resistance to ultraviolet radiation (GNPAT). Further analysis integrating multi-omics data revealed that yak introgression into non-coding regions can regulate the expression of EGLN1 and LRP11 genes, thereby promoting Tibetan yaks' adaptation to extreme environments.
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