Proteomic analysis of fertilized egg yolk proteins during embryonic development

Egg yolk is an important source of nutrients for embryo development. In this study, the egg yolk protein composition at 0, 10, and 18 D of incubation was analyzed by 2-dimensional gel electrophoresis (2-DE) combined with matrix-assisted laser desorption/ionization time-of-flight tandem mass spectrometry. A significant difference in the abundance of 42 protein spots representing 12 proteins were identified (P < 0.05). The 2-DE gel image analysis exhibited that the molecular weight (MW) of 29 protein spots was lower than their theoretical value, in which 14 vitellogenin (VTG) fragments were lower than the theoretical value. There were 13 protein spots showed a higher MW including 5 ovotransferrins with MW of 87.2 kDa. The gene ontology enrichment analysis suggested that biological process of the differentially expressed proteins were mainly involved in lipid transport and lipid localization at 10 and 18 D of incubation. The molecular function of the differentially expressed proteins was involved in nutrient reservoir activity, lipid transporter activity, and antigen binding at 10 D of incubation. At 18 D of incubation, the differentially expressed proteins mainly participated in nutrient reservoir activity and substrate-specific transporter activity. The high abundance of VTGs at 10 D of incubation might participate in lipid localization and lipid transportation to facilitate the yolk nutrient transport to embryo. The low expression of ovotransferrins at 10 D of incubation indicated the chondrogenesis of embryo.