Integrated physiology and proteome analysis of embryo and endosperm highlights complex metabolic networks involved in seed germination in wheat (Triticum aestivum L.)

The aim of this study was to investigate the physiological and proteomic changes in the embryo and endosperm during seed germination in the elite Chinese bread wheat cultivar Zhengmai 366. Upon imbibition, seed size and water content increased rapidly, followed by a series of metabolic changes including increases in soluble sugar content and α-amylase activity, a decrease in starch content, and a rapid increase in plant hormones. In total, 57 and 45 differentially accumulated proteins (DAPs) from the embryo and endosperm, respectively, were identified at five germination stages (0, 6, 12, 18, and 24 h). Principal component analysis revealed a significant proteome difference between embryo and endosperm as well as the different germination stages. The largest proteome changes occurred 24 h after seed imbibition. Embryo DAP spots were mainly involved in energy metabolism, amino acid metabolism, stress/defense, and protein metabolism; those from the endosperm were primarily related to storage protein and carbohydrate metabolism. Protein-protein interaction analysis revealed a complicated interaction network between energy-related proteins and other proteins. Metabolic pathway analysis highlighted complex regulatory networks in the embryo and endosperm that regulate wheat seed germination. These results provide new insights into the molecular mechanisms of seed germination.