High-quality genome assembly of Urial identifies candidate structural variants for sheep body-size evolution

Background Wild sheep possess remarkable adaptive traits, making them invaluable genetic resources for improving domestic sheep breeds. Urial ( Ovis vignei ), an extant wild relative of domestic sheep, provides a useful model for investigating genomic differences associated with wild–domestic phenotypic divergence. However, the absence of a high-quality genome assembly for Urial has limited our understanding of sheep domestication and genomic divergence between wild and domestic sheep. Results We present a high-quality genome assembly of Urial, generated using Nanopore and Illumina sequencing technologies. The genome spans 2.57 Gb with a contig N50 of 28.88 Mb. We identified 735 expanding gene families and 56691 structural variants. By integrating expanded gene-families and structural-variations analyses, we identified nine candidate genes, including ALDH1A1 , which harbored a 117-bp sequence absent from the Rambouillet reference assembly relative to the Urial assembly. Functional analysis in zebrafish further supported a potential role of the ALDH/retinoic acid pathway in vertebrate axial development. Conclusions Our findings provide new insights into candidate genomic mechanisms potentially associated with body-length evolution during sheep domestication. This high-quality Urial genome provides a valuable reference resource for comparative genetic and functional studies of wild and domestic sheep.