Round nucleated pearls are produced through a surgical operation, where a round nucleus and a mantle tissue ‘saibo’ from donor oyster are inserted into the gonad of the host oyster. The epithelial cells in the mantle tissue proliferate around the nucleus, and thus, the pearl sac is formed. Pearl sac secrets nacre and forms a pearl. The quality and economic value of pearls are assessed by pearl features such as colour, brightness, lustre and shape. Among all these features, colour has been reported as an important economic indicator and has been widely studied by researchers. Generally, pearl colour is affected by the donor oyster which is determined genetically and biological pigments (melanin and carotenoid). Organic matrices, metal ions and other factors have also been reported to influence the colour of a cultured pearl. Recently, multi‐omics methods have been used to study the colour formation of pearl, and some key genes and signal pathways related to the colour formation of pearls have been identified. Nevertheless, the specific mechanism of pearl formation needs further research. The review combines both fresh and sea water pearls focusing on Hyriopsis cumingii and pearl oysters to provide a general overview and understanding for pearl colour formation.

中文翻译：

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养殖珍珠如何获得颜色

圆形有核珍珠是通过外科手术生产的，其中将圆形核和来自供体牡蛎的地幔组织“ saibo”插入宿主牡蛎的性腺中。外套膜组织中的上皮细胞在核周围增殖，从而形成珍珠囊。珍珠囊会分泌珍珠质并形成珍珠。珍珠的质量和经济价值通过珍珠的颜色，亮度，光泽和形状等特征来评估。在所有这些特征中，颜色已被报告为重要的经济指标，并且已被研究人员广泛研究。通常，珍珠色受供体牡蛎的影响，该供体牡蛎是遗传和生物色素（黑色素和类胡萝卜素）决定的。也已报道有机基质，金属离子和其他因素会影响养殖珍珠的颜色。最近，多组学方法已被用于研究珍珠的颜色形成，并且鉴定了一些与珍珠的颜色形成有关的关键基因和信号途径。尽管如此，珍珠形成的具体机理仍需进一步研究。该评论结合了淡水珍珠和海水珍珠三角帆蚌和珍珠贝牡蛎为珍珠颜色的形成提供了一个总体概述和理解。