Molecular characterization of the BMP7 gene and its potential role in shell formation in Pinctada martensii.

Fang Yan,Qingheng Wang,Xiaodong Du,Shaojie Luo,Yuewen Deng,Yu Jiao,Weiyao Chen,Ronglian Huang

doi:10.3390/ijms151121215

Fang Yan, Qingheng Wang + Show 6 more

Open Access

https://doi.org/10.3390/ijms151121215

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Abstract

Bone morphogenetic protein 7 (BMP7), also called osteogenetic protein-1, can induce bone formation. In this study, the obtained full-length cDNA of BMP7 from Pinctada martensii (Pm-BMP7) was 2972 bp, including a 5'-untranslated region (UTR) of 294 bp, an open reading fragment of 1290 bp encoding a 429 amino acid polypeptide and a 3'-UTR of 1388 bp. The deduced protein sequence of Pm-BMP7 contained a signal peptide, a pro-domain and a mature peptide. The mature peptide consisted of 135 amino acids and included a transforming growth factor β family domain with six shared cysteine residues. The protein sequence of Pm-BMP7 showed 66% identity with that from Crassostrea gigas. Two unigenes encoding Pm-BMPRI (Pm-BMP receptor I) and Pm-BMPRII were obtained from the transcriptome database of P. martensii. Tissue expression analysis demonstrated Pm-BMP7 and Pm-BMPRI were highly expressed in the mantle (shell formation related-tissue), while Pm-BMPRII was highly expressed in the foot. After inhibiting Pm-BMP7 expression using RNA interference (RNAi) technology, Pm-BMP7 mRNA was significantly down-regulated (p < 0.05) in the mantle pallium (nacre formation related-tissue) and the mantle edge (prismatic layer formation related-tissue). The microstructure, observed using a scanning electron microscope, indicated a disordered growth status in the nacre and obvious holes in the prismatic layer in the dsRNA-Pm-BMP7 injected-group. These results suggest that Pm-BMP7 plays a crucial role in the nacre and prismatic layer formation process of the shell.

Highlights

Biomineralization is a widespread process existing in all kingdoms of living organisms
The complete Pm-Bone morphogenetic protein 7 (BMP7) cDNA sequence contained a 5'-untranslated region (UTR) of 294 bp, an open reading fragment (ORF) of 1287 bp predicted to encode a 429 amino acid polypeptide, a 3'-UTR of 1391 bp with 28 bp poly (A) tail and a typical polyadenylation signal
This cDNA sequence has been submitted to GenBank with the Accession No AGS32053.1

Summary

Introduction

Biomineralization is a widespread process existing in all kingdoms of living organisms. The shell of mollusks is a stable organo-mineral product composed of calcium carbonate and organic matrix, including proteins and polysaccharides [1]. Especially proteins, account for less than 5% (w/w) of the biomineralized shell, they are primarily responsible for controlling the. CaCO3 polymorph (calcite, aragonite), the size, the shapes of the crystallites, and the texture of the shell [2]. In terms of the shell structure of the bivalve pearl oyster, it includes two mineralized layers: The inner aragonite nacre and the outer calcite prismatic layer, which are mainly regulated by the matrix proteins secreted from the mantle pallium and the mantle edge, respectively. Shell formation is a very complex, precisive process, and the expression of each related protein is subject to strict regulation. The signal molecules and transcription factors involved in shell formation should be investigated

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