Grain color, metabolite content, and gene expression of HFL1 in comparison with wild-type values (WT) under different temperature treatments during seed development. A, Percentage of dark-brown grains in total mature seeds of HFL1. B, Relative expression of ACX genes in developing seeds at 15 DAF. C to E, Levels of free Lys (C), tryptamine (D), and serotonin (E) in HFL1 mature seeds. F to H, Relative expression of TDC1 (F), TDC3 (G), and T5H (H) genes in developing seeds at 15 DAF. Error bars represent sd of three biological replicates, and different letters indicate statistical significance among transgenic plants at P < 0.05.