Transcriptome analysis of mantle and pearl sac of freshwater pearl mussel Lamellidens marginalis to identify biomineralisation-associated genes

The freshwater pearl mussel, Lamellidens marginalis, is widely distributed in India and is cultured for freshwater pearl production. Understanding the biomineralisation process sheds light on the genes responsible for nacre secretion. However, information on the transcriptome of L. marginalis mantle tissue and pearl sac is lacking. This study generated transcriptome resources for L. marginalis, identifying genes involved in biomineralisation. Illumina paired-end sequencing yielded 11.13 million raw reads, assembled into 133,246 contigs and 26,373 unigenes. Of these, 21,033 unigenes exhibited homology with previously reported molluscan proteins. Genes related to biomineralisation, such as pif, perlucin, calreticulin, calmodulin, chitin synthase, chitin dehydrogenase, carbonic anhydrase, tyrosinase, shell matrix protein, dermatopontin isoform X1, chitinase 3, chitinase domain-containing protein 1, and putative chitinase-1were identified. This baseline information will help to compare the expression levels between the phenotypes of high-quality and low-quality pearls. Further investigations, incorporating large sample sizes and phenotype information, could assist in identifying type I genetic markers linked to pearl quality.