Identification, phylogenetic relationships, characterization and gene expression patterns of six different annexins of channel catfish (Ictalurus punctatus Rafinesque, 1818)

Annexins are Ca2+-dependent phospholipid-binding proteins. They are ubiquitous in living organisms and are involved in many cellular processes. In the course of studying Edwardsiella ictaluri pathogenesis in channel catfish, we identified that six annexin expressed sequence tags (A1, A2, A4, A5, A6 and A11) were up-regulated at the early stage of infection. In this study, we cloned and characterized these transcripts. The full-length nucleic acid sequences of channel catfish annexins ranges from 1231 (annexin A1) to 2476 (annexin A6). Each transcript has one open reading, which appears to encode peptides ranges from 317 to 662 amino acid residues with the calculated molecular masses from 35.0 (annexin A5) to 74.5 kDa (annexin A6). Phylogenetic and sequence analyses demonstrate that each channel catfish annexin had a diversified amino terminus, and had four structurally conserved 70-amino acid repeats. In addition, several important features for annexin functions were conserved in channel catfish. For expression profile, channel catfish annexin A1, A4 and A6 transcripts were detected in spleen, anterior kidney, liver, intestine, skin and gill of fish examined. However, annexin A2, A5 and A11 cDNAs were variously detected in tissues of fish sampled. This result provides important information for further elucidating channel catfish annexin functions in vivo.