Molecular characterization and expression of type-I interferon gene in Labeo rohita

Genes coding for type-I interferon (I-IFN) has been cloned from Labeo rohita, a commercially important and widely cultured fish in India and South East Asia. In the present study, full-length gene of I-IFN was amplified and sequenced. The sequence analysis revealed that I-IFN consists of 1,786 bp genomic sequence with four introns and five exons and an ORF of 546 bp encoding for a putative protein of 181 amino acids. The mature protein has a molecular weight of 18.97 kDa and consists of 158 amino acids and a signal peptide of 23 amino acids at the N terminus. The sequence carries I-IFN signature motif, one glycosylation site, two conserved cystine amino acids and other conserved amino acids. The sequence showed highest similarity to that of Cyprinus carpio (84 %). In silico analysis of the rohu I-IFN protein was done using various bioinformatic tools. The constitutive expression of I-IFN gene was found to be more in spleen compared to gill and kidney in real time PCR assay. Expression of I-IFN increased about 20-fold in cultured kidney cell 2 h after induction with poly I:C and showed maximum expression at 8 h post-induction.