Effects of salt-alkali stress on TauT2 gene expression in Oreochromis mossambicus

【Objective】To study osmotic pressure regulation function of the newly-discovered TauT2 gene of taurine transporter in Oreochromis mossambicus under salt-alkali stress, so as to provide reliable data for expounding function of taurine transporter of fish.【Method】 The coding sequence(CDS) of TauT2 gene was analyzed through PCR and sequencing. The amino acid sequence and tertiary structure of the encoded protein were predicted through bioinformatics analysis. Expression characteristics of the gene in 13 tissues including liver, intestine and muscle, mRNA expression of TauT2 gene in gill, kidney, intestine and liver tissues under salt-alkali stress(salt of 25 g/L and alkali of 4 g/L) in different times within 96 h were detected through fluorescence quantitative real-time PCR.【Result】CDS of TauT2 gene was 1881 bp, which encoded 626 amino acids. The amino acid sequence of TauT2 in O. mossambicus had the highest homology of 98.72% with that of taurine transporter in Maylandia zebra, and it was 88.52% homologous with tTauT1 gene in O. mossambicus, respectively. This protein had typical transmembrane domain of taurine transporter. Fluorescence quantitative realtime PCR results showed that the gene TauT2 was detected in 13 tissues suchas liver, intestine and muscle with the highest expression in blood and the lowest in intestine. Under salt-alkali stress, mRNA expression of TauT2 gene in gill, kidney, intestine and liver showed a tendency of first increasing and then decreasing. TauT2 expression of gill and liver peaked at 48 h, and those of kidney and intestine peaked at 24 and 72 h. The time to arrive peak value of TauT2 was significantly different from that of tTauT1 gene in O. mossambicus.【Conclusion】 Under salt-alkali stress, TauT2 gene in O. mossambicus is up-regulated to regulate osmotic pressure to maintain homeostasis of osmotic pressure. There are at least 2 kinds of taurine transporters in O. mossambicus and amino acid sequence, tertiary structure and osmoregulation function between the two taurine transporters are different.