repaired shells of Pinctada fucata LC-MSMS

Shells of pearl oyster are natural biominerals with remarkable properties and can be repaired after damage, which are regulated by biomacromolcules especially shell matrix proteins (SMPs). Identifying SMPs is critical for further understanding the process. Although proteomic methods have been used to reveal the complex protein mixture in mature shells, the proteomics of repaired shells after shell damage have not been reported before. Here, we studied the SMPs of the repaired shells (prismatic layers) 5-10 days after shell damage in Pinctada fucata by integrating transcriptomics and proteomics and compared the microstructure difference between repaired and mature shells. Although the repaired shells are calcite, similar to mature shells, the microstructure of repaired shells has holes in the center of prisms with irregular and curved edges. In total, we found 49 SMPs from the repaired shells including some proteins only existing in mature nacreous layers. Peroxidase-like protein and beta-N-acetylhexosaminidase may be important players in repaired shells. In addition, they have the capability to affect CaCO3 crystallization process in vitro, altering the packing and reducing the crystallinity of crystals. This study could improve our understanding of shell repair process and lay the foundation for studying SMPs-controlled biomineralization.