Abstract:

To reveal the role of TNF-α receptor genes TNF-R1 and TNF-R2 in the Nile tilapis (Oreochromis niloticus) immune processes, we cloned the full-length cDNA sequences of TNF-R1 and TNF-R2 from Nile tilapia by RACE. Sequence analysis showed that the full length of TNF-R1 cDNA was 2 275 bp, containing an open reading frame of 1 335 bp, and encoding a protein with 444 amino acids; the full length of TNF-R2 cDNA was 1 719 bp, containing an open reading frame of 1 476 bp, and encoding a protein with 491 amino acids. Protein structure prediction showed that TNF-R1 have three cysteine-rich domains and an intracellular death domain, while TNF-R2 have four cysteine-rich domains and without death domain. Systematic evolutionary analysis showed that the tilapia TNF-R1 and TNF-R2 were highly homologous with those of other vertebrates. Phylogenetic tree showed that TNF-R1 and TNF-R2 were clustered separately. By qRT-PCR, the highest expression levels of TNF-R1 and TNF-R2 mRNA were found in the gill, head kidney and spleen, and the lowest levels were in pituitary and muscle. The expression of TNF-α, TNF-R1 and TNF-R2 genes can be increased to varying degrees by stimulating the tilapia kidneys and spleen white cells incubated with LPS and Poly Ⅰ:C, respectively. The expressions of three genes in the head, kidney and spleen can be increased after intra-peritoneal injection of Streptococcus agalactiae. This study has some reference value to show the immune regulation mechanisms of TNF-R1 and TNF-R2 to improve the level of healthy breeding of tilapia.

Key words:

TNF-α, TNF-R1, TNF-R2, Oreochromis niloticus, immunity, Streptococcus agalactiae