iTRAQ-Based Quantitative Proteomic Analysis of Duck Eggshell During Biomineralization.

The avian egg is a valuable model for the calcitic biomineralization process as it is the fastest calcification process occurring in nature and is a clear example of biomineralization. In this study, we used iTRAQ MS/MS to detect and study for the first time: 1) the overall duck eggshell proteome; 2) regional differences in the proteome between the inner and outer portions of the duck eggshell. The new reference protein datasets allowed us to identify 179 more eggshell proteins than solely using the current release of Ensembl duck annotations. In total, 484 proteins were identified in the entire duck eggshell proteome. We also identified 28 novel proteins of unknown function that are involved in eggshell formation. Among the identified eggshell proteins, 54 proteins showed differential abundances between the inner, partially mineralized eggshell (obtained 16h after ovulation) compared to the overall complete eggshell (normally expulsed eggshell). At least 64 of the abundant matrix proteins were common to eggshell of four different domesticated bird species (chicken, duck, quail, turkey) and zebra finch. This study provides a new resource for avian eggshell proteomics, and augments the inventory of eggshell matrix proteins that will lead to a deeper understanding of calcitic biomineralization. This article is protected by copyright. All rights reserved.