ISOLATION AND CHARACTERIZATION OF AQUAPORIN 1 (AQP1), SODIUM/POTASSIUM-TRANSPORTING ATPASE SUBUNIT ALPHA-1 (NA/K-ATPASE ?1), HEAT SHOCK PROTEIN 90 (HSP90), HEAT SHOCK COGNATE 71 (HSC71), OSMOTIC STRESS TRANSCRIPTION FACTOR 1 (OSTF1) AND TRANSCRIPTION FACTOR II B (TFIIB) GENES FROM A EURYHALINE FISH Etroplus suratensis

The present study reports the complete sequences of Aquaporin 1 (AQP1) gene and partial sequences of genes, Sodium/potassium-transporting ATPase subunit alpha-1 (Na/K-ATPase α1 subunit), Osmotic Stress Transcription Factor 1 (OSTF1), Transcription Factor II B (TFIIB), Heat Shock Cognate 71 (HSC71) and Heat Shock Protein 90 (HSP90) obtained from mRNA and genomic DNA of Etroplus suratensis. They are candidate genes involved in stress responses of fishes. AQP1 gene was 2163 bp long. Its mRNA sequence has 55 bp 5'UTR, 783 bp open reading frame (ORF), 119 bp 3'UTR, three intronic regions and 90% identity with AQP1 of Oreochromis niloticus. The partial Na/K-ATPase α1subunit gene had a length of 5998 bp with an ORF of 2213 bp and 12 intronic regions. The partial OSTF1, TF IIB, HSC71 and HSP90 mRNA sequences obtained were 1473 bp, 587 bp, 1708 bp and 151 bp in length respectively.

All the genes showed a high sequence similarity with respective genes reported from fishes. Comparison of AQP1 and Na/K-ATPase α1 genomic DNA sequence of E. suratensis collected from different water system showed two types of AQP1 with one synonymous mutation in exon-1and higher sequence difference in intronic regions (including addition, deletion, transition and transversion mutations) with few synonymous and non-synonymous mutations in the exons of Na/K-ATPase α1. The sequence information of these major candidate genes involved in stress responses will help in further studies on population genetics, adaptive variations and genetic improvement programs of this cichlid species having aquaculture, ornamental and evolutionary importance.