Characterization of key BMP signaling molecules in the swimming crab (Portunus trituberculatus) and their expression characteristics during ovarian development.

The bone morphogenetic protein (BMP) signaling pathway is critically involved in regulating ovarian development and reproduction in animals. However, its molecular characteristics and expression patterns in Portunus trituberculatus remain poorly understood. In this study, the coding sequences (CDS) of five key components (BMP2, BMPR1B, BMPR2, Smad4, and Smad5) of the BMP signaling pathway were analyzed, and their tissue distribution across ovarian developmental stages I-VI was investigated. Bioinformatic analysis revealed that these proteins contain conserved functional domains characteristic of the BMP pathway and share high sequence similarity with orthologs from other crustaceans. Although all five genes were ubiquitously expressed, each showed distinct tissue specificity. BMP2 was highly expressed in the gills and ovary, while BMPR1B, BMPR2, Smad4, and Smad5 were predominantly expressed in the ovary, hepatopancreas, hemocytes, and intestine. In ovarian tissue, BMP receptors and Smads exhibited their highest expression levels at stage V of ovarian development. These results suggest that the BMP signaling pathway may be involved in ovarian development in P. trituberculatus, although its precise functional roles require further experimental validation. Our findings establish a molecular foundation for understanding reproductive regulation in crustaceans and offer a theoretical basis for strategies in reproductive manipulation and molecular breeding.