Molecular characterization and expression ananlysis of a QM protein gene from Chinese shrimp Fenneropenaeus chinensis

Based on lots of results, the QM protein was proposed to be a tumor suppressor, and facilitate in the innate immune responses, especially the prophenoloxidase (proPO) activation system. In the present study, a cDNA of 761 bp for the QM of Chinese shrimp, Fenneropenaeus chinensis (designated as FcQM) was cloned via rapid amplification of cDNA ends (RACE) technique. The complete cDNA sequence of FcQM contained an open reading frame (ORF) of 663 bp, 5' untranslated regions (UTR) of 42 bp and 3' UTR of 56 bp, which encoded a polypeptide of 155 amino acid residues. The analysis of the peptide sequence of FcQM revealed that FcQM sequence contained a Ribosomal_L16 domain, an SH3-binding motif, an N-acylation site, two putative antibiotic binding sites, two putative protein kinase C phosphorylation sites and two acylamidation sites, which shared over 80 % similarity with previously identified QM protein genes. Quantitative real-time PCR (qRT-PCR) results showed that the transcript of FcQM was extensively distributed in all the tested tissues and most highly expressed in hemocytes and hepatopancreas. After challenged with Vibrio anguillarum or white spot syndrome virus (WSSV), the FcQM transcripts were significantly increased (p < 0.05) both in hepatopancreas and hemocytes. Hence, the analysis of sequence and transcription suggested that FcQM might play crucial roles responses to bacterial and viral invasion in innate immunity of arthropods. This study is the first report of the QM protein gene from F. chinensis, which would enrich the understanding of the innate immune defense mechanism in shrimp.