Molecular characterization and salinity-responsive expression of isocitrate dehydrogenase in cichlid Etroplus...

Euryhaline cichlid Etroplus suratensis (Pearl spot), was found to exhibit strong acclimatization efficiency in brackish water (BW, 18 ppt), fresh water (FW, 0 ppt) as well as in sea water (SW, 36 ppt) condition throughout their life cycle. This capability makes it to be considered as a suitable euryhaline teleost model for investigating and understanding the effect of salinity challenges in fishes. Here, we investigated the effect of salinity on the gills of E. suratensis acclimated to different salinity conditions using Suppression Subtractive Hybridization (SSH) and Real Time PCR (qPCR). The Rapid amplification of cDNA ends (RACE) technique was used to obtain complete coding sequences (CDSs) from the selected EST's obtained through SSH. The findings revealed the increased expression of isocitrate dehydrogenase (IDH) when E. suratensis were exposed to higher salinities. Thus the study highlights the role of IDH in salinity adaptation by contributing to cellular energy homeostasis and enhancing antioxidant defence through ROS scavenging during oxidative stress. The derived complete CDS was used to deduce its amino acid sequences, which were used to construct a phylogenetic tree and protein model to obtain secondary and tertiary structure information of IDH. The present study is the first of its kind in characterising and studying the expression analysis of IDH derived from E. suratensis at varying salinities.