Shell matrix protein genes derived from donor expressed in pearl sac of Akoya pearl oysters (Pinctada fucata) under pearl culture

In the pearl culture it is still unclear whether cells in mantle grafts from donors remain in the pearl sac and whether they contribute to nacre formation in Akoya pearl oyster (Pinctada fucata). In this study, we compared the nucleotide sequences of the polymorphic genes coding for two important matrix proteins N16 and N19 among the donor and host mantles and pearl sac of Akoya pearl oysters to shed light on our hypothesis that cells in mantle grafts from donors remain in the pearl sac and to determine whether they contribute to nacre formation. Since these genes showed high expression levels in the mantle and pearl sac and polymorphism in nucleotide sequences among individuals, both genes were focused on their estimated decisive role in Akoya pearl formation. We compared the types of nucleotide sequences of cDNA reverse-transcribed from RNA, which are the expression products of the genes from the donor and host mantles, and pearl sac. N16 and N19 genes with the same type of nucleotide sequence as those of the genes obtained from the donor mantle were observed in each pearl sac 12 or 18 months after the implantation. This result indicates that cells in the donor mantle grafts continue to survive in the pearl sac and contribute to nacre formation under Akoya pearl culture. Thus, the present study provided molecular evidence of the role of the donor genotype in the expression of the matrix-protein-related genes N16 and N19. Its results will assist in paving new avenues for producing high-quality Akoya pearls, by developing a molecular approach to breeding donors.

► We examined whether the donor contributes to pearl formation in Akoya pearl oysters.
► We compared the N16 and N19 genes among the donor and host mantles, and pearl sac.
► The pearl sac contained a donor-mantle-specific type of sequence of both genes.
► The results of the PCR-RFLP analysis supported those of the sequencing.
► The donor has a major role in the production of cultured pearls.