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Background:The freshwater pearl mussel Lamellidens marginalis is found throughout India and is culturing to produce freshwater pearls. Understanding the process of pearl biomineralization provides insight into the genes responsible for the secretion of the complex nacre. However, information on the transcriptome of L. marginalis pearl sac, mantle tissue and gonads are lacking. Methods and Results: The present study generated the transcriptome resources for L. marginalis and identified genes involved in the biomineralization process in the species. The Illumina paired-end sequencing generated 11.13 million raw reads, and the reads were assembled into 133,246 contigs and 26,373 unigenes. 21,033 out of 26,373 unigenes showed homology with previously reported molluscan proteins. Genes of several proteins associated with biomineralization, namely, pif, perlucin, calreticulin, calmodulin, chitin synthase, chitin dehydrogenase, carbonic anhydrase, tyrosinase, shell matrix protein, chitinase 3, chitinase domain-containing protein 1, chitinase-like protein PB1E7.04c, and putative chitinase-1 were identified in the study. Conclusion: This study's findings will help identify differentially expressed genes that govern the characteristics of the pearl and identify the type-I markers in the genes.

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Cultured pearls have an important place in international trade. The Vedas, the Bible, and the Koran all mentioned pearls, and they are regarded as one of the highest honours. Pearls are generated in nature when an irritant, such as a sand grain or a parasite, is swept into the pearl molluscs and lodged within it, where it is coated with micro-layers of nacre, a lustrous substance made up of 80–90 per cent aragonite crystals of CaCO3. The ICAR-Central Institute of Freshwater Aquaculture (CIFA), Kausalyaganga, Bhubaneswar, India, has created a base technology for cultivating pearls in freshwater habitats, recognising the scope and value of freshwater pearl production. Indian pond mussel, Lamellidens marginalis is the major species used in freshwater pearl aquaculture. In addition, ICAR-CIFA has pioneered a novel feature of freshwater pearl farming. The Institute has also taken the lead in disseminating freshwater pearl culture technology to the country’s fish farming communities, entrepreneurs, researchers, and students to build a sustainable model for the country’s socio-economic development. In this chapter, we will briefly cover pearls and their types, their historical significance, the spread of pearl mussels of freshwater origin in various countries, pearl biomineralisation, pearl farming techniques, and factors affecting pearl quality, among other things.