The NOD1 and NOD2 in mandarinfish ( Siniperca chuatsi ): molecular characterization, tissue distribution, and expression analysis

Background NOD-like receptors (NLRs) are a family of cytoplasmic pattern recognition receptors (PRRs), of which NOD1 and NOD2 , are the main representative members. Many investigations have focused on the role of NOD1 and NOD2 in the innate immune response in Cypriniformes and Siluriformes. As an important economic fish in Perciformes, little is known about the function of NOD1 and NOD2 in mandarinfish ( Siniperca chuatsi ). Results The full-length NOD1 and NOD2 cDNA sequence was obtained using reverse transcription polymerase chain reaction (RT-PCR) and rapid amplification of cDNA ends (RACE). The mandarinfish NOD1 and NOD2 cDNA sequences contain 3247 bp and 3257 bp, and encode 918 amino acids and 988 amino acids, respectively. Multiple sequence alignments showed that mNOD1 and mNOD2 share high similarity with that from other vertebrates. RT-PCR analysis revealed that relatively high levels of m NOD1 and m NOD2 mRNA were detected in gill and head kidney tissues, compared with the heart, spleen, liver, muscle, and intestine. In addition, the relative levels of m NOD1 and m NOD2 transcripts were significantly upregulated in three tissues when the fishes were challenged with LPS and Poly I:C, interestingly, the NOD1 mRNA got peaked earlier than NOD 2 after LPS induction in the spleen, gill, and head kidney, and during Poly I:C treatment, the NOD2 mRNA got peaked at 8 h in spleen and gill, while NOD1 showed significant higher expression at 24 h post infection, besides, in head kidney, the NOD2 mRNA showed a great increasing trend and NOD1 got peaked at 16 h. Therefore the m NOD1 and m NOD2 may act differently within different tissues in different time during antiviral and antibacterial defense. Conclusions These results revealed the dynamic m NOD1 and m NOD2 expression during viral and bacterial infections, which suggested the NOD1 and NOD2 play important roles in innate immune of mandarinfish.