A novel C1q-domain-containing (C1qDC) protein from Mytilus coruscus with the transcriptional analysis against marine pathogens and heavy metals

• A novel C1qDC (McC1qDC) was identified from Mytilus coruscus.
• The McC1qDC mRNA was predominantly detectable in the hemocytes.
• McC1qDC mRNA was obviously up-regulated under stress of pathogen and heavy metals.
• McC1qDC might be a pattern recognition receptor and a marine pollution indicator.

The C1q-domain-containing (C1qDC) proteins, which are involved in various processes of vertebrates, are important pattern recognition receptors in innate immunity of invertebrates. In present study, a novel C1qDC was identified from Mytilus coruscus (designated as McC1qDC), which was 917 bp in length encoding 236 amino acids with a typical signal peptide of 19 amino acid residues in N-terminus. Based on its conserved C1q domain and molecular architecture of 10 β-strand jelly-roll folding topology structure, McC1qDC might be classified as a member of the C1q family. The mRNA transcript of McC1qDC was predominantly detectable in the hemocytes, and a less degree in gill, gonad and mantle, but trace in foot, adductor and digestive gland. Upon induction by Vibrio harveyi and Vibrio alginolyticus, McC1qDC expression was significantly up-regulated. Time-dependent mRNA expression of McC1qDC was found during copper and cadmium exposure for its heavy metal-binding domain. These results indicated that McC1qDC was a novel member of the C1qDC protein family as a pattern recognition receptor against pathogens, and might be developed as a potential indicator for monitoring heavy metals pollution.