Abstract

The tumor necrosis superfamily (TNFSF) and their receptors (TNFRs) play an essential role in inflammatory responses. In this study,tnfsf14,tnfrsf1a,tnfrsf1bandtnfrsf14were identified in spotted gar. All the genes have conserved genomic organization and synteny with their respective homologs in zebrafish and humans. The putative TNFSF protein contains a typical TNF homology domain in the extracellular region. All three TNFRSFs possess characteristic cysteine-rich domains. TNFRSF1a has a death domain in the cytosolic region which is absent in the TNFRSF1b and TNFRSF14. Notably, TNFRSF14 lacks a transmembrane domain and is predicted to be secreted. Protein structure modeling revealed that the key residues involved in the interaction between TNFSF14 and TNFRSF14 are well conserved in spotted gar. All four genes were ubiquitously expressed in the spleen, liver, kidney, gills and intestine. Infection withKlebsiella pneumoniaeresulted in remarkable downregulation oftnfsf14andtnfrsf14in tissues but upregulation oftnfrsf1aandtnfrsf1b. The results indicate thattnfsf14,tnfrsf1a,tnfrsf1bandtnfrsf14are involved in the immune response to bacterial infection, and expand knowledge on the TNF system in the primitive ray-finned fish.Keywords:TNFSF;TNFSF receptor;Klebsiella pneumoniae;evolution;expression;spotted gar