Genomic structure of the Nile tilapia (Oreochromis niloticus) transferrin gene and a haplotype associated with saltwater tolerance

Abstract

The present study presents the complete genomic sequence of Nile tilapia (Oreochromis niloticus) transferrin and functional studies of transferrin in relation to saltwater resistance. The gene consists of a total of 17 exons separated by 16 introns. The complete coding domain sequence is 2085 bp and the gene spans more than 7 kb of genomic DNA. The gene was compared to other species using phylogenetic analyses and protein alignment.Two microsatellite markers closely linked to transferrin were genotyped on surviving and non-surviving tilapia siblings kept in saltwater. Statistical analysis detected a significant distortion in segregation between two haplotypes defined by the two microsatellites. Sequence analysis of the transferrin gene detected several SNPs, some of which resulted in amino-acid changes in the transferrin protein. A haplotype of several SNPs segregated together with the two microsatellites and indicated that transferrin could be associated with saltwater tolerance in tilapia. An expression study indicated up-regulation of transferrin when tilapias were exposed to saltwater. These findings suggest that transferrin is involved in saltwater tolerance in tilapia.