The widely recognized color polymorphisms of molluscan shell have been appreciated for hundreds of years by collectors and scientists, while molecular mechanisms underlying shell pigmentation are still poorly understood. Tyrosinase is a key rate–limiting enzyme for the biosynthesis of melanin. Here, we performed an extensive multi-omics data mining and identified two tyrosinase genes, including tyrosinase and tyrosinase-like protein 2 (Tyr and Typ-2 respectively), in the Pacific oyster Crassostrea gigas, and investigated the expression patterns of tyrosinase during adults and embryogenesis in black and white shell color C. gigas. Tissue expression analysis showed that two tyrosinase genes were both specifically expressed in the mantle, and the expression levels of Tyr and Typ-2 in the edge mantle were significantly higher than that in the central mantle. Besides, Tyr and Typ-2 genes were black shell-specific compared with white shell oysters. In situ hybridization showed that strong signals for Tyr were detected in the inner surface of the outer fold, whereas positive signals for Typ-2 were mainly localized in the outer surface of the outer fold. In the embryos and larvae, the high expression of Tyr mRNA was detected in eyed-larvae, while Typ-2 mRNA was mainly expressed at the trochophore and early D-veliger. Furthermore, the tyrosinase activity in the edge mantle was significantly higher than that in the central mantle. These findings indicated that Tyr gene may be involved in shell pigmentation, and Typ-2 is more likely to play critical roles not only in the formation of shell prismatic layer but also in shell pigmentation. In particular, Typ-2 gene was likely to involve in the initial non-calcified shell of trochophores. The work provides valuable information for the molecular mechanism study of shell formation and pigmentation in C. gigas.

数百年来，收藏家和科学家一直对软体动物壳的广泛认可的颜色多态性表示赞赏，而壳色素沉着的分子机制仍然知之甚少。酪氨酸酶是黑色素生物合成的关键限速酶。在这里，我们进行了广泛的多组学数据挖掘，并在太平洋牡蛎长牡蛎中鉴定了两个酪氨酸酶基因，包括酪氨酸酶和酪氨酸酶样蛋白 2（分别为Tyr和Typ-2），并研究了酪氨酸酶在成年期的表达模式。黑色和白色壳色C. gigas 的胚胎发生. 组织表达分析表明，2个酪氨酸酶基因均在地幔中特异性表达，边缘地幔中Tyr和Typ-2的表达水平显着高于中央地幔。此外，与白壳牡蛎相比，Tyr和Typ-2基因具有黑壳特异性。原位杂交表明，在外褶皱的内表面检测到Tyr 的强信号，而Typ-2 的阳性信号主要位于外褶皱的外表面。在胚胎和幼虫中，有眼幼虫中检测到Tyr mRNA的高表达，而Typ-2mRNA 主要在载体和早期 D-veliger 表达。此外，边缘地幔中的酪氨酸酶活性显着高于中央地幔中的酪氨酸酶活性。这些发现表明Tyr基因可能参与壳色素沉着，而Typ-2更有可能不仅在壳棱柱层的形成中而且在壳色素沉着中起关键作用。特别是，Typ-2基因很可能参与了载体的初始非钙化壳。该工作为长尾鲟壳形成和色素沉着的分子机制研究提供了有价值的信息。