Whole-genome comparative analysis reveals genetic mechanisms of disease resistance and heat tolerance of tropical Bos indicus cattle breeds.

Bos indicus cattle breeds have been naturally selected for thousands of years for disease resistance and thermo-tolerance. However, the genetic mechanisms underlying these specific inherited characteristics must be elucidated. Hence, in this study, a whole-genome comparative analysis of the Bos indicus cattle breeds Kangayam, Tharparkar, Sahiwal, Red Sindhi, and Hariana of the Indian subcontinent was conducted. Genetic variant identification analysis revealed 155 851 012 SNPs and 10 062 805 InDels in the mapped reads across all Bos indicus cattle breeds. The functional annotation of 17 252 genes that comprised both SNPs and InDels, with high functional impact on proteins, was carried out. The functional annotation results revealed the pathways involved in the innate immune response, including toll-like receptors, retinoic acid-inducible gene I-like receptors, NOD-like receptors, Jak-STAT signaling pathways, and non-synonymous variants in the candidate immune genes. We also identified several pathways involved in the heat shock response, hair and skin properties, oxidative stress response, osmotic stress response, thermal sweating, feed intake, metabolism, and non-synonymous variants in the candidate thermo-tolerant genes. These pathways and genes directly or indirectly contribute to the disease resistance and thermo-tolerance adaptations of Bos indicus cattle breeds.