| Shell matrix proteins (SMPs) are the main organic components in the bivalve shell ofMolluscs. They regulate the calcium carbonate crystal formation and contributespecial characteristics to the organism. Thus the study of the SMPs has been one ofthe focuses on the molecular level in shell formation.In the present study, two types of genes involved in shell formation were cloned fromthe mantle of Pacific oyster Crassostrea gigas. The first type is nacrein-related genes,which encoding three proteins, namely nacrein-like proteins F1, F2and F3. Sequencealignment analysis revealed that the three proteins possessed typical α-CA domains,experienced post-translation modifications and were most closely related to thenacrein-like protein of California mussel Mytilus californianus via phylogeneticanalysis. However the CA domains were flanked by inserted repeat sequences.RT-PCR analysis showed that the nacrein-like proteins F1and F2were expressed inmultiple tissues and the expression levels remarkably rose after entering the juvenileand spat stage, which was basically consistent with the proportion increment of calcitecrystals in the shell.The other is pif gene, which encodes a protein containing VWFA and CHIT_BIND_IItwo typical conserved domains. The VWFA domain associated with protein-proteininteraction which might be beneficial to mollusks shell formation. The CHIT_BIND_II domain is capable of binding to chitin. Currently, Pif is the only moleculecontaining the above two typical domains, and each pif molecular contains a numberof VWFA or CHIT_BIND_II domains. In addition, phylogenetic analysis showed thatpif molecules produced no obvious differentiation in the Bivalvia and Gastropoda. |
