A GASTROPOD STAT MEMBER FROM DISK ABALONE, Haliotis discus discus: MOLECULAR CHARACTERISTICS AND TRANSCRIPTIONAL MODULATION    

S.D.N.K Bathige*, Navaneethaiyer Umasuthan, G.I.Godahewa, N.C.N.Perera J.D.H.E. Jayasinghe, Jehee Lee
Department of Marine Life Sciences  
School of Marine Biomedical Sciences  
Jeju National University  
Jeju Self-Governing Province 690-756  
Republic of Korea  
sl_sanjaya@yahoo.com  

Signal transducer and activator of transcription (STAT) family members are key signaling molecules that transduce the cellular responses from cell membrane to nucleus upon janus kinase (JAK) activation. Even though the seven STAT members have been reported in mammals, very limited information is available for the STAT genes in molluscans. In this study, we have identified and characterized a STAT paralog which is homologous to the STAT5 from disk abalone, Haliotis discus discus and designated as AbSTAT5.

A complete cDNA sequence was identified from disk abalone transcriptome database constructed by Roche 454 Genome Sequencer FLX system (GS-FLX™). The CDS (2370 bp) of AbSTAT5 coded for amino acid sequence with 790 aa. The poly peptide sequence of AbSAT5 was compared with other counterparts, and revealed the conserved residues important for functions and, typical domain regions including N-terminal domain, coiled coil domain, DNA binding domain, linker domain and Src homology 2 (SH2) domains as mammalian counterparts. To analyze STAT evolution, a phylogenetic tree was constructed based on the ClustalW alignment, and revealed that AbSTAT5 was clustered with molluscan subgroup in STAT5 clade with distinct evolution. Genomic sequence of AbSTAT5 was obtained from bacterial artificial chromosome library (BAC). According to the genomic structure of AbSTAT5, the coding sequence was distributed into twenty exons with nineteen introns. The immunologically essential transcription factor binding sites such as GATA-1, HNF, SP1, C/EBP, Oct-1, AP1, c-Jun and Sox-2 were predicted at the 5′-proximal region of the AbSTAT5 gene.

The expression of AbSTAT5 mRNA was examined by SYBR Green qPCR technique. The transcription of AbSTAT5 mRNA in different stages of embryonic development was investigated and observed the considerably higher level at morula and late veliger stages. The tissue specific expressional studies revealed that the highest level of AbSTAT5 transcripts was detected in hemocytes followed by gill tissues. The temporal expressions of AbSTAT5 were analyzed upon live bacterial (Vibrio parahemolyticus and Listeria monocytogenes), viral (viral hemorrhagic septicemia virus; VHSV) and PAMPs (LPS and Poly I:C) stimulations in hemocytes and, revealed the significant (P < 0.05) elevations indicating its potential immune modulation. These results suggested that the AbSTAT5 might be involved in maintaining the innate immune responses from developmental to adult stages of disk abalone. Further, this study provides a basis for structural and functional exploration of the STAT members in invertebrate JAK/STAT signaling pathway.