Abstract:Chinese shrimp (Fenneropenaeus chinensis) is an ecologically and economically important shrimp species. During the culture, F. chinensis were exposed to a series of stressors that adversely affect biological activities including growth rate. Ammonia, a product of protein degradation and bacterial activity, is a strong stressor in shrimp aquaculture. Glutamate dehydrogenase (GDH) is an abundant and ubiquitous mitochondrial enzyme that catalyzes reversible amination of glutamate. cDNA of GDH from F. chinensis (FcGDH) was cloned by rapid amplification of cDNA ends (RACE). The FcGDH cDNA was 1779 bp in size, and it included a 1659-bp open reading frame (ORF) that encoded a 522 amino-acid polypeptide of which the isoelectric point (pI) was 6.54 and the molecular mass was 61.3 kDa. Homology analysis revealed that the amino acid sequence of FcGDH was highly conserved with its homologs in other arthropod. The similarities between FcGDH and GDHs of Litopenaeus vannamei and Eriocheir sinensis were 98% and 89% respectively. Phylogenetic analysis showed that FcGDH was in the same branch with that of L. vannamei and then in the same branches with those of E. sinensis, Drosophila melanogaster, and Aedes aegypti in order. The tissue expression analysis showed that FcGDH was detected in all tested tissues including muscle, gill, hepatopancreas, stomach, intestine, lymph, and hemocytes. The highest expression of FcGDH was in the muscle that was an amino acid pool and the major tissue for protein deposition. After exposure to ambient ammonia, the expression of FcGDH gene was up-regulated significantly in muscles compared to the control group (P<0.01). The expression level of FcGDH in hepatopancreas was down-regulated significantly at 3 h (P<0.05), and was then stabilized up to 24 h. The expression of FcGDH was increased significantly after 48 h and reached the maximum at 72 h compared to the control group (P<0.01). These results implied that FcGDH might play an important role in the process of ammonia detoxification.
