Screening for Auxin response genes induced in grape cultured cells and in the pericarp of low and high seed containing berries. (A) Induction of auxin response genes in cultured grape cells with auxin treatment (20 μM indole-3-acetic acid). The expression level is relative to the control. (B) Expression of auxin response genes in the pericarp of berries with low and high seed weight-to-berry weight (SB) from one-week prevéraison clusters. Expression level of high-SB is shown relative to that of low-SB. (C) Expression of ARF4 gene in the pericarp of low and high-SB berry groups at two- and one-week prevéraison (PV), and at mid-véraison (MV). Expression levels of ARF4 are relative to those of low-SB berries at 2-wk PV. Gene expression was analyzed by qRT-PCR and all data represent means of five replicates and error bars indicate ± SEM. Significant differences between low- and high-SB berries at each cluster stage are indicated by asterisks (Student’s t-test, p < 0.05). Significant differences of each SB group between the ripening stages are denoted by different letters (lower and upper case letters are used for low- and high-SB berries, respectively (Tukey’s HSD, p < 0.05)).