cfMSP-1, an extremely acidic matrix protein involved in shell formation of the scallop Chlamys farreri

Matrix proteins play an important role in biomineralization by mollusks. In this study, we cloned and characterized an acidic protein (pI = 3.36) homolog of cfMSP-1 that is highly expressed in the mantle transcriptome of the scallop Chlamys farreri. RT-PCR and in situ hybridization showed that cfMSP-1 is specifically expressed in the outer fold of the mantle edge and pallial part. The expression level of cfMSP-1 remarkably increased and then reduced gradually to a value that is ~ 2-fold higher than basal levels after shell notching. Knock-down expression of cfMSP-1 in adults via dsRNA injection gave a disordered folia surface. Both shell notching and RNAi experiments indicated that cfMSP-1 plays an essential role in the formation of the folia of C. farreri.