NILE TILAPIA HEPATIC ANTIMICROBIAL PEPTIDE HAMP GENES ENCODING FOUR HEPCIDIN PEPTIDES WERE DIFFERENTIALLY ACTIVATED IN RESPONSE TO Streptococcus iniae INFECTION
Four Nile tilapia hepatic antimicrobial peptide hepcidin/HAMP genes, encoding 87-a.a. HAMP1, 90-a.a. HAMP2, 83-a.a. HAMP3 and 133-a.a. HAMP4 were identified from Taiwan Nile tilapia NT1 strain infected by virulent Streptococcus iniae 89353. The secreted mature peptide sequences of 22-a.a. HAMP1 and 26-a.a. HAMP2 of Nile tilapia with four disulfide bonds are identical to previously identified strong HAMP TH1-5 and TH2-3 of Mozambique tilapia, respectively. The 19-a.a. HAMP3 is a novel HAMP composed of only three disulfide bonds and 22-a.a. mature HAMP4 is a new HAMP1-like HAMP with four disulfide bonds. Four Nile tilapia HAMP genes were differentially activated not only in the liver but also in head kidney, spleen and gill of NT1 Nile tilapia treated by IP injection with S. iniae in dose of LD50 (1.5x105 CFU/g BW) to contribute for defense against S. iniae. From the new Nile tilapia genome assembly ASM185804v2 (GCA_001858045.2), we found 12 hepcidin genes, including 7 hamp1, 1 hamp2, 1 hamp3, and 3 hamp4 genes in LG11, and 6 hepcidin genes in two unplaced contigs, contig825 and contig1099. Among them, hamp1 and hamp4 genes were highly amplified to 12 and 4 genes, respectively. We propose that tilapia hepcidin gene amplification during evolution may contribute to disease-resistance of tilapia.