Cloning of mannose receptor MRC2 gene and its tissue expression characteristics after being infected by Aeromonas hydrophila in Pelodiscus sinensis

【Objective】The main purpose of this paper was to investigate the immune function of mannose receptor C type 2 gene in Pelodiscus sinensis(PsMRC2) against Aeromonas hydrophila infection, and to provide theoretical basis for the immune mechanism of P. sinensis against bacterial infection. 【Method】The ORF sequence of PsMRC2 gene was cloned by PCR, and the bioinformatics and phylogenetic analysis of the sequence was performed. Real-time fluorescence quantitative PCR was used to detect the tissue expression profile of PsMRC2 gene in the various tissues and the temporal expression of PsMRC2 gene infected by A. hydrophila. 【Result】The ORF sequence of PsMRC2 gene was 4086 bp, encoding a total of 1361 amino acid residues. The domain of PsMRC2 protein contained one fibronectin type Ⅱ (FNⅡ) domain(amino acids at 61-109 position), eight serial C-type lectin(CLECT) domains(amino acids at 116-1276 position) and one transmembrane domain(amino acids at 1295-1317 position). The secondary structure of PsMRC2 protein predicted by SOMPA included 706 randomcoils(51.87%), 302 extension chains(22.19%), 289 α-helixes(21.23%) and 64 β-turns(4.70%). The matching template for the tertiary structure of PsMRC2 protein predicted by SWISS-MODEL had 90% consistency with the amino acid sequence of PsMRC2 amino acid sequence, so the prediction results were reliable. A phylogenetic tree constructed based on the similarity of the amino acid sequence of PsMRC2 showed that P. sinensis had the closest relationship with turtles and distant relationship with fish. The expression of PsMRC2 gene was detected in the heart, liver, spleen, kidney, intestine, muscle, brain and lung tissues of P. sinensis, and the highest expression was observed in the spleen tissue. Meanwhile, after being infected by A. hydrophila, the relative expression levels of PsMRC2gene in the liver, spleen, kidney and intestinal immune tissues of P. sinensis were up-regulated. 【Conclusion】PsMRC2gene is conserved in terms of evolution. PsMRC2 gene is widely expressed in various tissues of P. sinensis,and it is involved in the immune response of P. sinensis against bacterial infection.