Cloning of glutamine synthetase gene from abdominal muscle of kuruma shrimp Marsupenaeus japonicus and its expression profile

Several shrimps can survive in a wide range of salinity by changing the concentration of free amino acids to regulate osmotic pressure. In particular, glutamine and alanine increase and decrease significantly depending on environmental salinity. However, there is little information about the enzymes involved in the metabolism of these amino acids. In this study, we focused on glutamine synthetase (GS), which catalyzes the biosynthesis of glutamine in the kuruma shrimp Marsupenaeus japonicus . Although the amino acid sequence of GS from the hepatopancreas has been reported, that of novel GS was determined from the abdominal muscle in this study. We named GSs from the hepatopancreas and abdominal muscle of kuruma shrimp as GS1 and GS2, respectively, and examined their expression levels in kuruma shrimp acclimated at 17, 34 and 40‰ salinity. While the GS1 and GS2 genes were expressed in both muscle and hepatopancreas, the expression level of the GS2 gene was increased in the muscle of shrimp exposed to higher salinities after rearing for 6 h, suggesting that GS2 is involved in the biosynthesis of glutamine in the abdominal muscle to regulate osmotic pressure at high salinity.