Abstract: Prolactin receptor can regulate osmotic pressure of fish by binding prolactin. In order to understand the expression of prolactin receptor PRLR1 in cobia（Rachycentron canadum）in high saline and low saline,the full-length cDNA sequence of codfish PRLR1 was obtained by RACE-PCR（rapid amplification of cDNA ends）. The full-length cDNA of this gene was 2 629 bp,including an open reading frame of 1 953 bp,and encoding 650 amino acids. The amino acid sequence comprised of two fibronectin type 3 domains（FN3）,a conserved WS region,and box1. The expression of PRLR1 mRNA in gill,intestine and body kidney was detected by real-time quantitative PCR under different water salinities（10‰,30‰,and 35‰）. The results showed that gene PRLR1 was expressed in various tissues of cobia,among which the highest expression of gill,followed by muscle,body kidney and intestine,but slightly expressed in stomach,spleen,brain and heart. In the low-salt group,the normal group and the high-salt group,the expression level of gene PRLR1 in gill was the highest,followed by that in the intestine and the lowest in the kidney. With the increase of salinity,the expression of PRLR1 in gill,intestine and body kidney showed a gradual decline. The above results reflect the functional difference of PRLR1 in osmotic organs of R. canadum,indicating that PRLR1 plays an important role in osmotic pressure regulation.

Key words: Rachycentron canadum, prolactin receptor, cDNA clone, quantitative real-time PCR, salinity adaptation