Cloning, Characterization, and Expression Prolife Analysis of Tyrosinase Genes: Insights into Black Shell Formation in Cyclina sinensis

Shell colors that exhibit a positive relationship with excellent traits can be employed as marker colors for breeding new varieties of bivalves. The clam Cyclina sinensis is an economically important marine bivalve that has three main colors: black, white, and purple. In the present study, we cloned and analyzed the full-length cDNA of the tyrosinase gene (TYR), which is the key gene for melanin synthesis, to explore the formation mechanism of black shells. The full-length cDNA of TYR was cloned by RACE-PCR, and the results showed that the full-length cDNA of TYR was 2993 bp, including a 2262 bp open reading frame encoding 753 amino acids. The results of functional domain prediction showed that deduced TYR protein contains a typical functional domain of tyrosinase, the common central domain. Phylogenetic analysis was conducted using neighbor-joining and maximum likelihood methods, and the results indicated that the evolutionary positions of C. sinensis and Meretrix meretrix were closest. The qRT-PCR results showed that TYR mRNA was highly expressed in the outer edge of the mantle, which suggested that TYR was involved in the synthesis of melanin in the mantle of C. sinensis and might play an important regulatory role in the formation of melanin in black clam shells.