Genome-Wide Comparative Analyses Reveal Selection Signatures Underlying Adaptation in Domestic Bactrian and Wild Two-Humped Camel

Bactrian camels are vital large mammals that adapt well to the harsh environment of the desert. Genome-wide selection signatures can provide insights into natural and/or artificial selection and reveal functional genes related to biological characteristics and/or phenotypes. Here, we investigated genomic diversity and structure, and identified selection signatures of domestic Bactrians from China and Mongolia (IMG_D and MG_D) and wild two-humped camels (MG_W). The average sequencing depth reached 12.40× for each population, and more than 4.01, 3.58, and 2.70 million single-nucleotide polymorphisms (SNPs) were detected covering all autosomes and the X chromosome in the IMG_D, MG_D, and MG_W. The population structure suggested gene flows between IMG_D and MG_D, but no strong signal migration between the domestic and wild two-humped camels. Following the F_ST and θ_π approaches, candidate evolving genes in the camel lineage were significantly enriched in insulin secretion, insulin signaling pathway, lipid metabolism, immune system, and adaptation for desert, which may be the target of selection in domestic Bactrians and wild two-humped camels during the breeding and survival process. Furthermore, screened candidate genes, including ABCC8, KCNJ11, FFAR1, PRKACB, CREB1, PRKACB, ACACA, and SLC2A4, were associated with insulin pathways and putatively related to insulin resistance. We also identified candidate genes and KEGG pathways associated with olfactory transduction and environmental adaptation, implying a greater desert adaptation capacity in Bactrian camels. In conclusion, the present study provides a greater understanding of genome diversity and variations associated with adaptive and biological characteristics in Bactrian camels.