The Diversity of Shell Matrix Proteins: Genome-Wide Investigation of the Pearl Oyster, Pinctada fucata

In molluscs, shellmatrix proteinsare associated with biomineralization, a biologically controlled process that involves nucleation and growth of calcium carbonate crystals. Identification and characterization of shell matrix proteinsare important for better understanding of the adaptive radiationof a large variety of molluscs. We searched the draft genome sequence of the pearl oyster Pinctada fucataand annotated 30 different kinds of shell matrix proteins. Of these, we could identified Perlucin, ependymin-related proteinand SPARC as common genes shared by bivalves and gastropods; however, most gastropod shellmatrix proteinswere not found in the P. fucata genome. Glycinerich proteinswere conserved in the genus Pinctada. Another important finding with regard to these annotated genes was that numerous shell matrix proteinsare encoded by more than one gene; e.g., three ACCBP-like proteins, three CaLPs, five chitin synthase-like proteins, two N16 proteins(pearlins), 10 N19 proteins, two nacreins, fo...