MOLECULAR INSIGHTS INTO TWO NOVEL TETRASPANIN HOMOLOGS IDENTIFIED FROM DISK ABALONE (Haliotis discus discus)  

Aquaculture at the global level has now become a rapidly developing area since the current demand for the Mari-cultured products is at an exponentially growing rate. To fulfill this requisite, not only the aquafarmers but also scientists from diversified areas have now been gathered on a platform with the common goal of developing the world aquaculture. One major problem associated with production loses is due to the pathogenic infections of aqua-cultured fish and shellfish species. Under these settings, engagement of marine molecular geneticists and immunologists in aquaculture has become a prerequisite to study the immune system of marine organisms at a molecular level, in order to come up with the possible and novel solutions to reduce the production loses due to pathogens, by developing sophisticated technologies. In current study, we sought to identify two immunologically important molecular components from commercially important shellfish species disk abalone (Haliotis discus discus).

      The cDNA sequences of abalone tetraspanins were identified form transcriptomic database and designated as Tspan30 and Tspan33. Bioinformatics studies were conducted on the cDNA and derived amino acid sequences to predict the molecular and functional properties of the putative proteins. The tissue specific mRNA expressional levels were quantified using SYBR Green quantitative real time PCR (qPCR) techniques. Abalones were injected with Vibrio parahaemolyticus, LPS and poly I: C. Hemocytes were extracted in different post injection time points and mRNA levels were quantified using qPCR methods. The cDNA sequences of Tspan30 (1361 bp) and Tspan33 (1118 bp) coded for amino acid sequences of Tspan30 (234 aa) and Tspan33 (290 aa) that possess the four transmembrane domain architecture which is typical to tetranspanins. In healthy abalones, Tspan30 and Tspan33 found to be ubiquitously expressed in all examined tissues, showing the highest expressions in hemocytes. Upon the pathogenic stimulations mediated by V. parahaemolyticus, LPS and poly I:C in hemocytes, both Tspan30 and Tspan33 exhibited potent inductions in mRNA expressions.  Tspan30 showed significantly upregulated highest expressional levels upon V. parahaemolyticus at 12h, LPS at 12h and, poly I:C at 6h Post-injection (p.i.) while Tspan33 upon V. parahaemolyticus at 12h, LPS at 12h and poly I:C at 24h Post-injection (p.i.).

These findings suggest that AbTspan30 and AbTspan33 may play a role under pathological conditions in disk abalone. Applicability of this knowledge in shellfish abalone protection programs needs to be considered in our future studies.