Abstract: The full-length cDNA of red tilapia(Oreochromis sp.)Na ⁺-K ⁺-ATPase α was cloned using homological cloning and rapid amplification of cDNA ends(RACE)methods. Results showed that the full-length cDNA was 3 379 bp, containing a 5'untranslated region(5'-UTR)of 143 bp, a 3'-UTR of 164 bp and open reading frame of 3 072 bp bp encoding 1 023 amino acids with an estimated molecular weight of 112.5 kD and an estimated isoelectric point of 5.26. BLAST analysis revealed that the Na ⁺-K ⁺-ATPase α of red tilapia shared a high homology of 97%-99% with the corresponding proteins of other know species, respectively. Phylogenetic analysis showed that Na ⁺-K ⁺-ATPase α of red tilapia shared closest relationship with the corresponding proteins of Oreochromis mossambicus and Sarotherodon melanotheron, respectively. The expression pattern of Na ⁺-K ⁺-ATPase α at different water salinity was analyzed by fluorescent quantitative real-time PCR technology, and results showed that the expression of Na ⁺-K ⁺-ATPase α reached the highest level at 25, and fell to a relatively lower level at 32. In the same salinities, the expression of Na ⁺-K ⁺-ATPase α mRNA increased significantly(P<0.05)during the adaptation phase(12 h), and in regulatory phase(after 24 h)the amounts of Na ⁺-K ⁺-ATPase α mRNA fell to a relatively lower level, while the expression levels were still higher than that of fish in control group(P<0.05).

Key words: Red tilapia(Oreochromis sp .), Na⁺-K⁺-ATPase, α Rapid amplification of cDNA ends(RACE), Fluorescent quantitative real-time, PCR