Structural Variations Associated with Adaptation and Coat Color in Qinghai-Tibetan Plateau Cattle

Abstract

Structural variations (SVs) play crucial roles in the evolutionary adaptation of domesticated animals to natural and human-controlled environments, but SVs have not been explored in Tibetan cattle, which recently migrated and rapidly adapted to the high altitudes of the Qinghai-Tibetan Plateau (QTP). In this study, a de novo chromosome-level genome assembly for Tibetan cattle is constructed. It is found that using a lineage-specific reference genome significantly increased variant detection accuracy and completeness. Analysis of long-read sequencing data from 36 high-altitude QTP and 48 low-altitude cattle identified 222 528 SVs and 259 SV hotspot regions. Positively selected SVs in high-altitude cattle are related to energy metabolism erythropoiesis and angiogenesis, and peroxisomal metabolism. A 102-bp intronic deletion in GNPAT likely upregulated its expression. It is distinguished 7293 SVs that may be introgressed from yak, including variants upstream of the hypoxia-inducing gene EGLN1. Finally, a ≈2-Mb heterozygous inversion and two translocations on chromosome 6 are likely associated with the cattle gray coat via regulatory effects on the KIT gene. The results confirm the importance of SVs in evolutionary adaptation and the contribution yak-introgressed SVs to the rapid acclimatization of QTP cattle.