Cloning and tissue expression of a novel hcSRCR1 gene in differential inner-shell color pearl mussel Hyriopsis cumingii

As a superfamily of glycoproteins, scavenger receptors play a crucial role in the identification and assembly of chemically modified lipoproteins. In this study, cDNA of Hyriopsis cumingii scavenger receptor cysteine-rich gene (hcSRCR1) was cloned by using rapid amplification of cDNA ends (RACE) approaches, then the bioinformatics and expression profiles were analyzed. The complete hcSRCR1 cDNA consists of 1 000 nucleotides with a 819 bp open reading frame encoding 272 amino acid residues. The molecular weight of hcSRCR1 was 28.16 ku and pI was 5.55. It was also predicted that protein hcSRCR1 had two scavenger receptor cysteine rich domains and six conserved cysteine residues. qRT-PCR and Western blot showed that hcSRCR1 was constitutively expressed in a wide range of tissues with the highest expression level in the mantle. Moreover, differential expression analysis revealed that hcSRCR1 was more highly expressed in the mantle of purple line mussels compared to white line mussels. In situ hybridization investigations of the precise expression site of hcSRCR1 mRNA in the mantle showed that hcSRCR1 mRNA is specifically expressed in the inner epithelial cells of the outer fold mantle, as well as throughout the outer epithelium of the outer fold and ventral mantle. Our results suggest that hcSRCR1 play a role in the formation of shell and pearl color formation, and may provide useful information for further studies on regulation mechanism in the color formation of pearls.