Key Laboratory of Mariculture, Ministry of Education, Ocean University of China, Qingdao, 266003, China.
Laboratory for Marine Fisheries Science and Food Production Processes, Qingdao National Laboratory for Marine Science and Technology, Qingdao, 266237, China.
Mar Biotechnol (NY). 2021 Oct;23(5):777-789. doi: 10.1007/s10126-021-10063-2. Epub 2021 Sep 6.
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.
贝类壳的广泛认可的颜色多态性已经被收藏家和科学家们欣赏了数百年，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，在太平洋牡蛎(Crassostrea gigas)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），并研究了在黑壳和白壳颜色 C 中成年和胚胎发生期间酪氨酸酶的表达模式。组织表达分析表明，两个酪氨酸酶基因均特异性表达于套膜中，边缘套膜中 Tyr 和 Typ-2 的表达水平显著高于中央套膜。此外，与白壳牡蛎相比，Tyr 和 Typ-2 基因在黑壳牡蛎中特异性表达。原位杂交显示，Tyr 在外套膜内表面有强烈的信号，而 Typ-2 的阳性信号主要定位于外套膜外表面。在胚胎和幼虫中，在眼幼虫中检测到 Tyr mRNA 的高表达，而 Typ-2 mRNA 主要在担轮幼虫和早期 D 幼体中表达。此外，边缘套膜中的酪氨酸酶活性显著高于中央套膜。这些发现表明，Tyr 基因可能参与壳色素沉着，而 Typ-2 不仅更可能在壳棱柱层的形成中发挥关键作用，而且可能在壳色素沉着中发挥关键作用。特别是，Typ-2 基因可能参与担轮幼虫的初始非钙化壳。这项工作为 C. gigas 壳形成和色素沉着的分子机制研究提供了有价值的信息。
