Amino acids and proteins
During embryo development, the level of total free amino acids (FAAs) gradually decreased at 5-25 DAF and increased thereafter (Figures S7d, S8d). In contrast, FAAs in endosperm decreased as grain filling progressed. In addition, FAAs was higher in embryo than endosperm. Storage proteins were higher in embryo than endosperm (Figures 4e, S6e). However, gene expression pattern of storage protein synthesis showed an opposite correlation with storage proteins content, suggesting that their encoding genes are specifically expressed in the endosperm, as in wheat (Xiang et al., 2019).