Abstract：Na+/K+-ATPase α1 is a key enzyme in regulating the osmotic pressure of aquatic animals. In this study, the cDNA of Na+/K+-ATPase α1 gene was first cloned from Chinese mitten crab (Eriocheir sinensis) using RT-PCR and RACE. The full length of cDNA was 3 805 bp (GenBank No. KC691291.1). It contained a 306 bp 5' UTR and 388 bp 3' UTR, as well as a 3111 bp open reading frame encoding 1 037 amino acids. The amino acid sequence shared as high as 91.9%~ 98.5% homology with other aquatic crustaceans, indicating its high conservation in crustaceans. Quantitative RT-PCR indicated the highest expression level in the hepatopancreas, followed by the gill, the intestines and stomach, and then the muscle and heart. Na+/K+-ATPase α1 expression was detected at the eight developmental stages of Eriocheir sinensis; but a low, insignificant expression was found in the five zoea stages (zoea Ⅰ to zoea Ⅴ). Surprisingly, expression reached the highest level at the megalopa stage and then significantly decreased at the larva and juvenile stages (P<0.05). Culturing the adult crabs in brackish water (salinity 21) and fresh water for 30 days yielded the following results: Expression in the muscle and hepatopancreas of crabs reared in brackish water was significantly higher (P<0.05) than that of crabs reared in fresh water; expression in the gill in fresh water was significantly higher (P<0.05) than that in brackish water; and finally, expression in the gonad did not significantly differ between brackish and fresh waters (P>0.05). These results showed that the hepatopancreas and gill were the dominant organs of Na+/K+-ATPase α1 gene expression in Eriocheir sinensis, indicating that this gene played an important role in regulating the osmotic pressure of the species. This study provides based data for research on suitable salinity control in reproduction, zoea production, and parental conservation of crab.
