Plasma membrane calcium ATPaso (PMCA) plays a critical role in transporting Ca2 out of the cy- tosol across the plasma membrane which is essential both in keeping intracellular Ca2+ homeostasis and in biomineralization.In this paper we cloned and localized a gene encoding PMCA from the pearl oyster Pinctada fucata.This PMCA shares similarity with other published PMCAs within the functional domains.Reverse transcdption-polymerase chain reaction analysis shows that it is expressed ubiquitously.Furthermore,in situ hybridization reveals that it is expressed in the inner epithelial calls of the outer fold and in the outer epithelial calls of the middle fold,as well as the edge near the shell,which suggests that PMCA may be involved in calcified layer formation.The identification and characterization of oyster PMCA can help to further under-stand the structural and functional properties of molluscan PMCA,as well as the mechanism of maintaining Ca2+ homeostasis and the mechanism of mineralization in pead oyster.