Sequence Analysis of Sweetfish (Plecoglossus altivelis) Interleukin-12B Gene and Its Expression Changes upon Listonella anguillarum Infection

Abstract: Interleukin-12B (IL-12B)， a subunit of IL-12， plays an important role in the inflammatory response in mammals against intracellular pathogenic bacteria. In this study， the cDNA sequence encoding IL-12B gene of sweetfish， 1 152 bp in length excluding 3′-poly A tail， was obtained from de-novo transcriptome sequencing of sweetfish macrophages. The sequence contained a complete open reading frame (ORF)， which encoded a propeptide of 303 amino acids (aa). A 22 aa signal peptide was predicted to be existed at its N-terminus. Sequence analysis showed that sweetfish IL-12B shared the highest homology with that of Atlantic salmon with 50% protein sequence identity or 50% amino acid sequence identity. IL-12B mRNA was mainly expressed in the head kidney and peripheral blood leukocytes (PBL)， weakly expressed in the spleen， gills and intestine of healthy sweetfish. Upon Listonella anguillarum infection， IL-12B mRNA expression dramatically increased in the head kidney and PBL， and reached peak value at 12 hpi (hours post infection). Western blot analysis indicated that serum IL-12B significantly ncreased in sweetfish infected by L.anguillarum. In conclusion， IL-12B might be involved in the progress of immune response in sweetfish against microbial infections.

CSTR: 32200.14.cjcb.2013.09.0009