Pm‐miR ‐29b is involved in nacre formation by regulating tyrosinase‐like protein in Pinctada martensii

The miR-29 family includes miR-29a, miR-29b and miR-29c. Our previous research showed that miR-29a of Pinctada martensii (Pm-miR-29a) is involved in nacre formation via targeting neuropeptide Y receptor type 2 (Y2R). In this report, we validated and corrected the precise sequence of mature Pm-miR-29b and elucidated its function and mechanism difference with Pm-miR-29a in nacre formation. Our results showed that the precursor of Pm-miR-29b has 87 bp with a characteristic hairpin structure, which is the same with that of Pm-miR-29a. Stem-loop quantitative real-time PCR analysis indicated that Pm-miR-29b was constitutively expressed in all of the tissues, with high expression in gonads. After overexpression of Pm-miR-29b via mimic injection into P. martensii, the nacre microstructure showed a disordered growth status with a little difference with Pm-miR-29a. Target prediction analysis indicated that tyrosinase-like protein (Pfty), nacre protein (N19), fibroblast growth factor 18, protein serine kinase and neuropeptide Y2R were the potential target gene of Pm-miR-29b. Dual-luciferase analysis showed that the luciferase activity of the reporter containing 3′ UTR of Pfty and Y2R gene was significantly inhibited by Pm-miR-29b mimics. However, only the expression of Pfty was downregulated after overexpression of Pm-miR-29b in vivo. Therefore, Pm-miR-29b participated in nacre formation via targeting Pfty in P. martensii.