Molecular cloning and expression of NOS in shrimp, Litopenaeus vannamei

The importance of the nitric oxide synthase (NOS) gene family is demonstrated by many studies in recent years. However, the lack of sequence information and clones of shrimp NOS cDNA limits further study on its characterization and function in this species. In this report, the cDNA of NOS contained full-length ORF was cloned from the Pacific white shrimp, Litopenaeus vannamei. It was of 4680 bp, including a 5'-terminal untranslated region (UTR) of 278 bp, a 3'-terminal UTR of 862 bp, which contained 5 ATTTA repeats, and an open reading frame (ORF) of 3540 bp encoding a polypeptide of 1179 amino acids. It contained a typical NO synthase domain at the N-terminal, next to a flavodoxin 1 domain, a flavin adenine dinucleotide (FAD) binding domain, respectively, and a conservative nicotinamide adenine dinucleotide (NAD) binding domain structure at the C-terminal. Quantitative real-time reverse transcription PCR analysis revealed L. vannamei NOS (LvNOS) to be expressed in most shrimp tissues, with highest expression in the hepatopancreas and weakest expression in skin. The expression of LvNOS after challenge with LPS and poly I:C was tested in hemocytes, hepatopancreas and nerve. The results indicated that the NOS transcript level could be induced in hemocytes by injection with LPS. The highest expression was in the hemocyte, with 8.8 times (at 3 h) as much as that in the control (p < 0.05). However, sharp down-regulation of NOS was found in hepatopancreas and nerve after LPS and poly I:C injection (p < 0.05). These results suggested that NOS might play an important role in shrimp's defense against pathogenic infection.