Contribution of the TGF β signaling pathway to growth of Pacific oyster ( Crassostrea gigas )

Growth mediated by the transforming growth factor beta (TGF beta) signaling pathway is a key trait in understanding environmental adaptability and species stability. The aim of the present study was to identify the TGF beta signaling pathway members and their expression patterns in different sized Pacific oysters ( Crassostrea gigas ) . Nine oysters were selected for each of two groups: group L (shell height 77.57 +/- 7.55 mm, shell length 49.96 +/- 4.79 mm) and group B (shell height 43.58 +/- 2.74 mm, shell length 33.25 +/- 2.78 mm). Using a bioinformatics approach, 37 protein sequences of TGF beta signaling pathway members were classified in C. gigas , including 19 species for this species, nine ligands, five receptors, and five Smads. The mRNA expression levels of TGF beta pathway members in oysters of different sizes showed that both the TGF beta/activin/Nodal and BMP/GDF/MIS subfamilies are involved in the growth regulation of C. gigas . In the first subfamily, there was one possible signaling pathway: INHBATGFBR1/BMPR1B/ACVR1 - BMPR2 - Smad3/Smad1, 5, 8. In the second subfamily, there were three possible signaling pathways: BMP2 - BMPR1B - BMPR2 - Smad1, 5, 8; BMP4 - BMPR1B - BMPR2 - Smad1, 5, 8; and BMP7 - ACVR1/BMPR1B - BMPR2 - Smad1, 5, 8. Principle components analysis identified Bmp3, I-Smad, Bmp4, INHBA, and Smad3 as biomarkers of growth in the TGF beta signaling pathway of C. gigas , implicating the TGF beta pathway in the growth of C. gigas .