Molecular cloning and transcriptional regulation of an allograft inflammatory factor-1 (AIF-1) in Zhikong scallop Chlamys farreri

• CfAIF-1 was the first mollusk one involved in immunity in early development stages.
• CfAIF-1 was inducible by PAMP stimulation and could response to bacterial infection.
• Study on CfAIF-1 might help to understand mechanism of innate immunity in scallop.

The allograft inflammatory factor-1 (AIF-1) is one of the key factors associated with inflammatory response. In the present study, the full-length cDNA of AIF-1 was identified from Zhikong scallop Chlamys farreri (named as CfAIF-1) by EST (expressed sequence tag) analysis and RACE (rapid-amplification of cDNA ends) approaches. The cDNA of CfAIF-1 consisted of a 5-terminal untranslated region (UTR) of 58 bp, a 3-UTR of 607 bp with a poly (A) tail, and an open reading frame (ORF) of 468 bp encoding a polypeptide of 155 amino acids with the putative molecular mass of 17.8 kDa. There was an EF hand Ca2 +-binding motif in the deduced amino acid sequence of CfAIF-1 which was conserved in other AIF-1s. CfAIF-1 shared closer phylogenetic relationship with invertebrate counterparts than vertebrate. The mRNA transcripts of CfAIF-1 were dominantly expressed in hepatopancreas, hemocytes and adductor. During scallop ontogenesis, the CfAIF-1 mRNA was expressed at a low level at early developmental stages from eggs to blastula, and then increased significantly from gastruta to late veliger larvae (P < 0.05). Moreover, the mRNA expression levels of CfAIF-1 in the hemocytes of adult scallop were significantly up-regulated during 12–48 h after LPS, PGN and poly I:C stimulation (P < 0.01), but there was no significant fluctuation detected after glucan stimulation. Furthermore, the challenge of bacteria Vibrio anguillarum remarkably induced the mRNA expression of CfAIF-1 in hemocytes at 6 h (P < 0.05) and 12 h (P < 0.01). All these results collectively indicated that CfAIF-1 might be involved in the immune response during the ontogenesis and contribute to the defense against microbe infection in scallops.