The relationship between carotenoid and shellfish shell color has gained increasing attention. β, β-carotene-9′,10′-oxygenase 2 (BCDO2) is a key enzyme in animal carotenoid metabolism, and its accumulation affects the change in body color, as demonstrated in mammals, birds, and fish. However, it is unclear whether BCDO2 is involved in the formation of the red shell color of clam. To explore the molecular structure and biological function of BCDO2 gene in the process of carotenoids accumulation, in this study, the BCDO2 from hard clam Meretrix meretrix (designated as Mm-BCDO2) was cloned and characterized, and the single-nucleotide polymorphisms (SNPs) associated with shell color were detected. The results of qRT-PCR indicated that Mm-BCDO2 gene was expressed in all six tested tissues, and the expression of mantle was significantly higher than other tissues (P < 0.05). The association analysis identified 20 SNPs in the exons of Mm-BCDO2, among which three loci (i.e., c.984A > C, c.1148C > T, and c.1187A > T) were remarkably related (P < 0.05) to the shell color of clam. The western blot analysis revealed that the expression level of Mm-BCDO2 in the mantle of red shell clams was stronger than that of white shell clams (P < 0.05). Further, the immunofluorescence analysis indicated that the single-layer columnar cells at the edge of the mantle were the major sites for the Mm-BCDO2 secretion. This study explored the potential impacts of BCDO2 gene on the shell color of M. meretrix, which provided a theoretical basis for a better understanding of the important role of BCDO2 in carotenoid metabolism.

类胡萝卜素与贝壳颜色之间的关系越来越受到关注。β, β-胡萝卜素-9',10'-加氧酶 2 (BCDO2) 是动物类胡萝卜素代谢的关键酶，其积累会影响体色的变化，如哺乳动物、鸟类和鱼类所示。然而，目前尚不清楚 BCDO2 是否参与了蛤的红壳颜色的形成。探索其分子结构和生物学功能BCDO2 类胡萝卜素积累过程中的基因，在本研究中， BCDO2 来自硬蛤 梅里特里克斯·梅里特里克斯 （指定为 MM-BCDO2) 被克隆和表征，并检测到与壳颜色相关的单核苷酸多态性 (SNP)。qRT-PCR 结果表明，MM-BCDO2 基因在所有6个受试组织中均有表达，且地幔的表达明显高于其他组织（磷< 0.05)。关联分析确定了外显子中的 20 个 SNPMM-BCDO2，其中三个基因座（即c.984A > C、c.1148C > T和c.1187A > T）显着相关（磷< 0.05) 到蛤的壳颜色。蛋白质印迹分析显示，红壳蛤地幔中Mm-BCDO2的表达水平强于白壳蛤。磷< 0.05)。此外，免疫荧光分析表明，地幔边缘的单层柱状细胞是 Mm-BCDO2 分泌的主要部位。本研究探讨了潜在影响BCDO2 外壳颜色的基因 M. meretrix，这为更好地理解其重要作用提供了理论基础。 BCDO2 在类胡萝卜素代谢中。