Significant association of SNP polymorphism in the tilapiaenhancer of polycomb homolog 1gene with salt tolerance

Abstract

Identifying candidate genes involved into osmoregulation provides a basis for developing molecular markers for breeding of saline tilapia. In this study, we characterized and conducted a functional analysis of the Enhancer of Polycomb Homolog 1 (EPC1) gene in Nile tilapia. The length of the EPC1CDS sequence was 1161 bp, including 14 exons encoding 386 amino acid residues. The expression for EPC1 was investigated in the gill, brain and intestine tissues of Nile tilapia that challenged by 0 ppt, 10 ppt, 15 ppt and 20 ppt of salinity content by qRT-PCR. We found that the gene was significantly down-regulated at 20 ppt of high salinity stress. We also detected significant evidence of 5 SNP association in the EPC1 gene with salt tolerance trait by genotyping 192 extreme individuals from a full-sib tilapia family (N = ~500). The individuals with heterozygous SNP genotypes in the population (with an average survival time of 3,064 s) were significantly less tolerant than the other individuals with the homozygote genotypes (with an average survival time of 5,986 s). Further functional analysis on the EPC1 protein sequences from 31 fish species inhabiting different salinity environments identified seven amino acid sites as significantly associated sites (α < 0.01) with salinity content. These data suggested that the EPC1 gene may be a candidate gene related to osmoregulation process in tilapia. Our findings could contribute to selection of the saline tilapia by using marker-assisted selection technique.