MOLECULAR CHARACTERIZATION AND TRANSCRIPTIONAL ASPECTS WITH IMMUNE RESPONSIVE mRNA EXPRESSION PROFILES OF AN INTERFERON INDUCED GENE IDENTIFIED FROM DISK ABALONE (Haliotis discus discus)  

N. C. N. Perera1,2*, G. I. Godahewa and Jehee Lee
E-mail: chathunp@gmail.com
 
1Department of Marine Life Sciences, School of Marine Biomedical Sciences, Jeju National University, Jeju Self-Governing Province 690-756, Republic of Korea
2Fish Vaccine Research Center, Jeju National University, Jeju Self-Governing Province 690-756, Republic of Korea

Abalones are marine shellfish species considered as highly valued gastropods specially in Eastern Asia. Increasing pressure with the invasive pathogens, environmental stress conditions and contaminant pollutants may considerably affect for the occurrence of the diseases and the production losses of the abalone in marine culture. Since invertebrate shellfish like abalones are mainly depend on the innate arm of the immunity, recently molecular immunologists are concerning to carry out their studies on innate immune components in shellfish species. Interferons (IFNs) are cytokines which released by the host as the response for the presence of pathogen, that mainly characterized by antiviral and immunomodulatory activities. Though, IFN has not been publicized in lower order invertebrate species few studies have conducted on interferon induced proteins in abalone. To date previous studies has proven that IFNs exert antiviral and immune-regulatory activities in different species and it can be assumed that the interferon induced protein activities are mediators of these pleiotropic effects. As an attempt to explore the immune related genes in abalone species this study was conducted to examine the characteristic features at molecular and transcriptional level of the interferon induced 44 like counterpart of disc abalone (Haliotis discus discus; AbIFI44). Putative AbIFI44 coding sequence (CDS; including stop codon) encoded 711 bp which could be coded 236 amino acids polypeptide with a 26 kDa molecular mass and 8.3 pI. Its 5' untranslated region (UTR) and 3' UTR consisted of 56 and 783 nucleotides, respectively. Polyadenylation signals (1440AATAAA1445, 1457AATAAA1462) and poly-A tail were identified at the end of 3' UTR. Based on AbIFI44 amino acid sequence, in silico characterization was conducted with comparison of other IFI44 homolog sequences. Molecular domain architecture of AbIFI44 showed that presence of GTP/Mg2+ binding sites which might be collectively involved in transcription and signal transduction in abalone. Since, this is the first study of molluscan IFI44 molecule; pairwise IFI44 sequence comparison revealed that AbIFI44 shared quit low highest identity (23.5%) and similarity (40.3%) with teleostean IFI44 counterpart (Takifugu rubripes). Phylogenetic analysis also depicted AbIFI44 belongs to the invertebrate IFI44 clade and revealed its distinct evolutionary relationship among vertebrate IFI44 members. Transcriptional analysis exhibited that AbIFI44 mRNA markedly expressed in hepatopancreas, digestive tract and gill. Hence gill is the most susceptible tissue for the pathogenic infection in aquatic organism, kinetic expression of AbIFI44 transcripts in gill tissue was examined upon viral hemorrhagic septicemia virus (VHSV) challenge and significant mRNA upregulation was noted at 12 h and 72 h post infection. Considering of all the findings of present study, abalone interferon induced 44 like (AbIFI44) molecule could be a novel outcome to the molluscan immune studies.