Genomic structure and molecular characterization of NLRC3-like from Siberian sturgeon (Acipenser baerii) and expression response to Streptococcus iniae and pathogen-associated molecular patterns

NLRs are important intracellular pattern recognition receptors and play an essential role in innate immunity for vertebrates. However, research on sturgeon NLRs is still scarce. In this study, the NLRC3-like gene from Siberian sturgeon (Acipenser baerii) (AbNLRC3-like) was cloned and characterized. The AbNLRC3-like full-length cDNA was composed of 3310 bp with a 166 bp of 5′-UTR, 2838 bp open reading frame (ORF) and 306 bp 3′-UTR, encoding 945 amino acids. Structural analysis of AbNLRC3-like showed the typical NLRs structure, including a central NACHT domain and a C-terminal 12 LRR motifs. Quantitative real-time PCR (qRT-PCR) analysis revealed that AbNLRC3-like was widely distributed in all tested tissues with a relatively high expression level in the mid-kidney, head-kidney and spleen. After Streptococcus iniae infection, the mRNA expression of AbNLRC3-like was significantly up-regulated at the pre-mortality period and the recovering period in valvula intestine, but it was significantly down-regulated around the mortality period in the duodenum and spleen. In splenic leukocyte, the mRNA expression of AbNLRC3-like was significantly induced by LPS, PGN and Poly(I:C). These results suggested that AbNLRC3-like may play a critical role in the immune response of Siberian sturgeon during pathogen challenge. To our best knowledge, this is the first report of the NLRC3 gene in sturgeon.