Donor and recipient contribution to phenotypic traits and the expression of biomineralisation genes in the pearl oyster model Pinctada margaritifera

Carole Blay,Chin-Long Ky,Serge Planes

doi:10.1038/s41598-017-02457-x

Abstract

Grafting associates two distinct genotypes, each of which maintains its own genetic identity throughout the life of the grafted organism. Grafting technology is well documented in the plant kingdom, but much less so in animals. The pearl oyster, Pinctada margaritifera, produces valuable pearls as a result of the biomineralisation process of a mantle graft from a donor inserted together with a nucleus into the gonad of a recipient oyster. To explore the respective roles of donor and recipient in pearl formation, a uniform experimental graft was designed using donor and recipient oysters monitored for their growth traits. At the same time, phenotypic parameters corresponding to pearl size and quality traits were recorded. Phenotypic interaction analysis demonstrated: 1) a positive correlation between recipient shell biometric parameters and pearl size, 2) an individual donor effect on cultured pearl quality traits. Furthermore, the expressions of biomineralisation biomarkers encoding proteins in the aragonite or prismatic layer showed: 1) higher gene expression levels of aragonite-related genes in the large donor phenotype in the graft tissue, and 2) correlation of gene expression in the pearl sac tissue with pearl quality traits and recipient biometric parameters. These results emphasize that pearl size is mainly driven by the recipient and that pearl quality traits are mainly driven by the donor.

Highlights

From a genetic point of view, grafting creates a chimera of a single individual made up of genetic material issued from two distinct genomes, with each genome maintaining its own distinct genetic identity throughout the life of the grafted organism
The results show that it is mainly the recipients that influence the size of the pearl, while the individual donors influence pearl quality traits
We showed that pearl size phenotype was highly correlated with the biometric parameters of the recipient oyster, while those of the donor oyster (QL/TL groupings) had no impact

Summary

Introduction

From a genetic point of view, grafting creates a chimera of a single individual made up of genetic material issued from two (or more) distinct genomes, with each genome maintaining its own distinct genetic identity throughout the life of the grafted organism. Another study examined the phenotypic correlation between recipient shell weight and size of pearls in P. fucata, revealing a limited positive relationship whereby recipient oysters with heavier shells produced bigger pearls[11] These results indicate potential underlying genetic correlations between the recipient or donor growth and pearl size, whereby selection for faster growing oysters might further improve pearl size. In P. margaritifera, one such study demonstrated the influence of grow-out sites on cultured pearl quality traits over a broad geographic scale between archipelagos in the South Pacific[16] Another analyzed environmental influence on pearl size parameters in relation to the recipient oyster biometric parameters[17]. (4), we followed the kinetics of the recipient–donor influence on pearl formation by monitoring pearl size and quality parameters over 12 months This information provides basic knowledge to help us to understand the donor-recipient correlations and their relative contributions in pearl oyster grafts

Methods

Results

Conclusion