Genome-wide Detection Of Selection Signatures Between Fat-tailed And Thin-tailed Sheep Populations

Selection signatures are the selective footprints across the organism genome due to the effect of selection in the process of artificial selection or natural selection, which displayed the long range linkage disequilibrium in chromosome or genetic diversity reduction.This experiment was conducted to study genetic differentiation between two sheep populations of distinct tail types with genome-wide detection of selection signatures and to search the candidate genes related to important traits of sheep. Based on the Illumina Ovine SNP 50 K Breadchip genotyping data of Mongolian sheep and Tibetan sheep,population differentiation index FST was adopted to detect the selection signatures,to found the genes located in selection signature regions were found by bioinformatis analyses. Based on the tail adipose tissue of Hulun Buir sheep(fat-tailed sheep, include large fat-tailed sheep and small fat-tailed sheep) and Tibetan sheep(thin-tailed sheep), the relative expression study was adopted to explore the difference of gene relative expression level of PPARG and PDGFD, which were related to fat metabolism.This research presents findings in two aspects:(1) 465 selected SNPs were found,harboring 448 candidate genes.The result of GO analysis showed that these candidate genes enriched in the GO terms related to development process, cell morphogenesis and macromolecule catabolic process.And 50 genes related to lipid metabolism were selected from these candidate genes, the analysis of GO analysis showed that these genes have enriched the GO terms which are related to lipid biosynthetic process, phospholipid metabolic process and lipid binding. In addition, four genes were found, PPARG, RXRG, SLC27A2 and ACSL6, which enriched the PPAR signaling pathway.PPARG and PDGFD gene were found to involved in fat metabolism process, and have important relationship with tail fat formation.(2)The gene relative expression level of PPARG and PDGFD from Hulun Buir sheep is significantly higher than Tibetan sheep between fat-tailed and thin-tailed sheep(P<0.01) and the gene relative expression level of PPARG from lager fat-tailed Hulun Buir sheep is significantly higher than small fat-tailed Hulun Buir sheep(P<0.05) but the gene relative expression level of PDGFD has no difference between lager fat-tailed Hulun Buir sheep and small fat-tailed Hulun Buir sheep.FST can be used to detect the genes with selection signatures and some of the candidate genes were related to important traits in sheep. And PPARG and PDGFD gene were proved to be closely related to tail fat deposition through the relative expression studies, these genes can be used as candidate genes for different tailed sheep breeding. This study can provide theoretical references for sheep breeding or breed improvement.