A proteomic approach reveals biomineralization and immune response for mantle to pearl sac in the freshwater pearl mussel (Hyriopsis cumingii)

In the process of production of freshwater pearl, implanted mantle pieces undergo a series of complex physio-logical and biochemical processes to form pearl sac, which produce pearl. This is a very important site of occurrence due to immune-induced biomineralization, while its molecular regulatory mechanism is still unclear. Here, we use proteomics to identify differentially expressed proteins (DEPs) of the mantle and pearl sac and examine the biomineralization and immune response of the pearl sac formation process in Hyriopsis cumingii. Using iTRAQ technology and bioinformatics analysis, we obtained DEP profiles between the mantle and pearl sac. A total of 1871 proteins were identified. Of these, 74 DEPs were found between the pearl sac and outer mantle, 112 DEPs between the pearl sac and inner mantle, and 124 DEPs between the outer and inner mantles. Bioinformatics analysis revealed that the screened biomineralization-related DEPs were mainly enriched in signaling pathways associated with calcium signaling, regulation of the actin cytoskeleton and protein processing in the endoplasmic reticulum, while the immune-related DEPs were mainly enriched in the Notch, Hippo, nuclear factor kappa-B (NF-kappa B), and transforming growth factor-beta (TGF-beta) signaling pathways. In addition, the expression of six biomineralization-related and four immune-related proteins were verified at the transcriptional level using quantitative real-time PCR. Our findings contribute to furthering the understanding of the mechanisms of pearl formation and immune response, and have long-term implications for future studies on the production of high-quality freshwater pearls and development of the freshwater pearl industry.

Automated summary

In this study, the differentially expressed proteins (DEPs) of the mantle and pearl sac in the production of freshwater pearls were identified and the related signaling pathways of biomineralization and immune response were analyzed. The expression levels of selected proteins were verified using quantitative real-time PCR. The findings contribute to the understanding of pearl formation and immune response mechanisms.