Comparative analysis of the 72 h and −72 h PG samples revealed that 863 proteins were significantly expressed with 396 up-regulated proteins and 467 down-regulated proteins (Fig. 1, and Table S1). Further GO classification analysis of these proteins was performed. For biological processes, 26%, 20% and 10% of the differentially expressed proteins were correlated with metabolic processes, cellular processes and developmental processes, respectively. For molecular functions, 46% and 41% of the differentially expressed proteins were associated with catalytic and binding activities, respectively. For cellular components, 43% and 26% of the differentially expressed proteins were related to cells and organelles, respectively (Fig. 2).