Two NF-kappa B inhibitor-alpha (I kappa B alpha) genes from rock bream (Oplegnathus fasciatus): Molecular characterization, genomic organization and mRNA expression analysis after immune stimulation

Abstract

I kappa B alpha is a member of I kappa B family, which sequesters NF-kappa B in an inactivate form in the cytoplasm and blocks the translocation of NF-kappa B to nucleus. The I kappa B alpha paralogs of rock bream (Ofl kappa B alpha-A and Ofl kappa B alpha-B) encoded I kappa B alpha proteins with typical features including, highly conserved I kappa B degradation motif, six ankyrin repeats and a PEST sequence. However, their amino acid identity and similarity were only 55.6 and 69.7%, respectively suggesting that these two genes could be the two different isoforms of I kappa B alpha. The number and size of the exons of Ofl kappa B alpha-A and Ofl kappa B alpha-B were conserved well with all the compared vertebrate species, although they have significantly different genomic sizes. Phylogenetic analysis revealed that Ofl kappa B alpha-A and Ofl kappa B alpha-B proteins cluster with I kappa B alpha family members; however, they were grouped with different subclades in I kappa B alpha family. Tissue specific expression of Ofl kappa B alpha mRNA was constitutively detected in all the tested tissues, and they showed the higher transcription level in heart, liver, gill and peripheral blood cells, respectively. The injection of fiagellin stimulated the mRNA expression of Ofl kappa B alpha paralogs in head kidney and intestine. Moreover, the Ofl kappa B alpha mRNA expression in gill and liver was significantly up-regulated by LPS, poly I:C and Edwardsiella tarda challenges. The transcription of Of kappa B alpha was up-regulated in early-phase of injection and then rapidly restored. These results suggest that the Of kappa B alpha paralogs might be involved in rapid immune responsive reactions in rock bream against bacterial and viral pathogens. (C) 2014 Elsevier Ltd. All rights reserved.