Identification and expression characterization of three Wnt signaling genes in pearl oyster (Pinctada fucata)

The Wnt signaling pathway plays an important role in animal development and in the biomineralization process. At present, although the biomineralization mechanism in pearl oyster (Pinctada fucata) has been extensively studied, there is little research on the Wnt signaling pathway in pearl oyster. To understand the potential role of the Wnt signaling pathway in pearl oyster, we cloned and sequenced three genes from the Wnt signaling pathway in pearl oyster that encode the following proteins: β-catenin, Dishevelled (Dvl) and T-cell factor (TCF). Genomic structure analysis revealed that Pf-β-catenin genomic DNA contained 15 exons, Pf-Dvl genomic DNA contained 16 exons, and Pf-TCF genomic DNA contained 7 exons. Their deduced amino acid sequences all showed the highest identity with homologs in Crassostrea gigas. Yeast two-hybrid analysis verified that Pf-β-catenin interacted with Pf-TCF. These three genes were ubiquitously expressed in seven pearl oyster tissues analyzed with the highest expression in the gill and a certain amount of expression in the mantle, a tissue related to shell formation. After shell notching, the dynamic changes in expression of these three genes showed that they reached a maximum at 4 days, indicating their response to shell regeneration. All three genes were constitutively expressed during five developmental stages of the pearl oyster, with high levels at the early embryonic development stage. Taken together, these results suggested that Pf-β-catenin, Pf-Dvl and Pf-TCF might participate in shell formation and early embryonic and larval development in the pearl oyster.