Heterologous expression of AtBBX21 in potato promotes gene expression and metabolites accumulation related with the phenylpropanoid pathway in leaves. A, Diagram of phenylpropanoid pathway and key enzymes. B, PAL, CHS, CHI, and F3H transcript levels (n = 4). C, Chlorogenic acid 1, chlorogenic acid 2, and quercetin glycoside metabolites measured by HPLC (n = 5). n = number of biological replicates. Mean values are shown with error bars indicating se. Data were analyzed by Student’s t tests, and asterisks indicate significant difference between nontransformed and transgenic lines (*P < 0.05; NS, not significant).