Molecular features and expression characteristics of a novel tumour necrosis factor-α paralog from snubnose pompano (Trachinotus blochii).

Abstract

Tumour necrosis factor alpha (TNF-α) is a pivotal cytokine in vertebrate immunity. Considering the increasing scientific interest for TNF-α in piscine biology, the paper detailed the characteristics of a novel tnf-α gene from a high-value mariculture species, Trachinotus blochii. The tbtnf-α complementary DNA (cDNA) of 1385 bp encoded an open reading frame of 762 bp, 3' untranslated region (3' UTR) of 484 bp and 5' UTR of 139 bp. The deduced Tbtnf-α1 showed the highest sequence identity to that of Seriola dumerili (∼83%). The comparative phylogenetics identified the protein as the TNF-α paralog 1. Tbtnf-α1 displayed all the hallmark features of other teleost TNF-α, suggesting similar immune-related functions. However, the Tbtnf-α1 was predicted to be more acidic and less thermostable. The study generated the three-dimensional (3-D) structure model of Tbtnfα-1 based on the protein sequence that can be applied in future research. The genomic organization of tbtnfα-1 contained four exons and three introns. Real-time polymerase chain reaction (PCR) analysis in healthy conditions showed the constitutive expression and wide distribution of tbtnfα-1 in a tissue-specific manner, with maximum expression in the kidney. As in silico analysis predicted the biological function of the novel TNF-α as a regulator in the defence response to bacterial infection, functional validation was done through the expression analysis following exposure to a marine pathogen (Vibrio harveyi) challenge. The results showed that the expression of tbtnf-α1 in the liver, spleen, heart, gill and kidney was significantly upregulated compared to the control fish after the challenge at differential time points post-infection. The study also demonstrated the kinetics of tbtnfα-1 expression in the liver, spleen, heart, gill and kidney at 6 to 48 h post-infection, and the results showed the peak expression at 24 h in all the tissues followed by a drop in the expression. Briefly, the present study detailed the sequence, structural and functional characteristics of tnf-α1 in the immune response of silver pompano.