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

Abstract

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.

Variation of Gene Expression in the Endemic Dinaric Karst Cave-Dwelling Bivalve Mollusk Congeria kusceri during the Summer Season

“…In invertebrate animals, tyrosinases play important roles in a multitude of biological processes, including immune response (acting as prophenoloxidases) and hexoskeleton production, but they are also involved in bivalve shell biomineralization [71,72], for example by controlling the size of calcium carbonate crystals [73]. Some studies also suggest that the tyrosinases expressed in the mantle edge might contribute to melanin production, determining shell color [74]. However, since the shell of C. kusceri is not pigmented, as one of its many adaptations to the subterranean environment, we might expect such differentially expressed tyrosinase genes not to be involved in shell pigmentation but rather in the biomineralization process.…”