Genomic selection signatures in Brazilian sheep breeds reared in a tropical environment

Abstract

The molecular and genetic effects of heat stress are not as well understood as physiological effects. Heat Stress response should be considered one component of gene network coordinated across various cells, tissues and systems. Its action seeks to minimize the effects of the environment on cellular functions. The detection of selection signatures can identify genes and mutations associated with phenotypic traits even if they are no longer segregating within the populations of interest. This paper looked at 48 sheep breeds (1988 animals), of which 649 animals are from 6 Brazilian breeds reared in a tropical environment. These animals were genotyped using the 50 K SNP Chip. We applied different detection methods (HapFLK and PCAdapt) to identify genomic regions with selection signals (selection signatures). Three groups of breeds were defined, and the first component showed a clear separation between Hair_Warm and Wool_Cold groups. The second component showed some divergence between Wool_Cold and Wool_Warm, with some Hair_Warm breeds located together with Wool_Warm. Hair Brazilian breeds were separated from the others in the first breed component, while the second component segregated European breeds from African and Asian breeds. The four genomic regions identified in chromosomes 2, 7, 11 and 16 harbor several genes related to a wide range of functions. These include production traits (such as milk, growth and reproduction), metabolism (fat and energy), stress response (including immune and inflammation), as well as cell cycle functions. These genomic regions can be a starting point for identifying gene mutations and selecting adapted animals, mainly in a climate change scenario. The locally adapted tropical sheep breeds can be an important genetic reservoir of these thermotolerance genes.