Gene Expression Patterns in the Mantle and Pearl Sac Tissues of the Pearl Oyster Pinctada fucata

Abstract

The shell of pearl oysters consists of two distinct layers, nacre and prismatic. Mantle is the tissue involved in the shell formation, and its ventral part (mantle edge) forms the prismatic layers, whereas the dorsal part (pallium) forms the nacre. In pearl culture, mantle grafts from the pallium of donor are transplanted into the recipient. Then pearl sac is formed by proliferation of epithelial cells from the grafted mantle to form pearls. It has been reported that gene expression patterns are different between mantle edge and pallium in accordance with their distinct functions in the shell formation. However, it is not well addressed whether gene expression is identical or not between two nacre-forming tissues, pallium and pearl sac. Here, we examined expression patterns of known genes related to nacre and prismatic layer formation in mantle edge, pallium, and pearl sac of Pinctada fucata. Although the pallium and pearl sac have the same function in terms of nacre formation, various genes were not expressed identically to the respective tissues, suggesting that shell matrix proteins differently function in the formation of shell nacre and pearls.