Chemical compositions and gene expression pattern of five colored phenotypes of pearl oyster Pinctada margaritifera

Pearl oyster Pinctada margaritifera is famous for culturing the high -valued round nucleated pearl with prismatic and nacre layer color polymorphism. However, there exists limiting understanding in prismatic and nacre color formation in the species. Herein, we found five colored phenotypes in the Sanya wild population. The five colored phenotypes included black prismatic layer (BP), red prismatic layer (RP), black nacreous layer (BN), red nacreous layer (RN) and golden nacreous layer (GN). The chemical substances and gene expression pattern of five colored phenotypes of P. margaritifera were analyzed. The results showed that the contents of eumelanin, pheomelanin, carotenoids and trace elements (Mn, Mg, Fe) were significantly different between the BP and the RP (P < 0.05). Differently expressed genes were discovered between red and black prismatic layers individuals, such as TYR, CYP450, NOTCH1, SCD, FASN and ACACA, which were involved in melanogenesis, tyrosine metabolism, retinol metabolism, Notch signaling pathway, fatty acid metabolism pathway. WGCNA analysis explored that the candidate genes including NOTCH1, HPGDS, MAPKB, JUN, NFKBIA, FBXL5, FTH1, HERC2 and COX15. The key genes in the networks were closely related to nacre coloration. These findings would help to understand color polymorphism of pearl oyster P. margaritifera.