Interferon gamma (IFN-ã) is one of the key cytokines that plays a major role against viral and intracellular bacterial infection. In addition to the IFN-ã gene, teleost fish possess a second copy known as IFN-ã-related (IFN-ãrel) gene. This report describes structural and functional properties of IFN-ãrel gene in the Indian major carp, rohu (Labeo rohita), a commercially important freshwater fish species in the Indian subcontinent. The rohu IFN-ãrel gene consisted of four exons with three intervening introns and phylogenetically closely related to grass carp. The full-length IFN-ãrel cDNA comprised 927 bp nucleotides with a single open reading frame of 504 bp, encoding 167 amino acids (aa) polypeptide with a signal peptide of 24 aa. The mature rohu IFN-ãrel protein was 143 aa with a predicted molecular weight of 16.85 kDa. Basal expression analysis of IFN-ãrel showed its wide range of expression in all examined tissues: The highest was in the skin and the lowest was in the liver. In response to LPS, poly I:C, iE-DAP, muramyl dipeptide stimulations, and bacterial infections, IFN-ãrel gene expression was significantly (p<0.05) induced in treated fish tissues as compared with their control. The IFN-ãrel was expressed as recombinant protein (rIFN-ãrel) and confirmed through western blot. Stimulation of peripheral blood leukocytes with rIFN-ãrel protein resulted in the activation of IFN-ã receptor and marked induction of inducible nitric oxide synthase gene expression. These results together may suggest the important role of IFN-ãrel as an antimicrobial cytokine in fish.
Amino Acid Sequence Animals