Expression analysis of LBD16, LBD18, EXP14, and EXP17 in lax3 and LAX3 in lbd16, lbd18, and lbd16 lbd18. A, LBD16 and LBD18 expression in lax3 in response to auxin. Seven-day-old seedlings were incubated with auxin (20 μm IAA) for 0, 4, or 8 h and subjected to qRT-PCR. Data are the mean ± se of three independent biological replications. Asterisks denote statistical significance (*, P < 0.05; and ***, P < 0.001). B, EXP14 and EXP17 expression in lax3 in response to auxin. Treatment and analysis of the samples were performed as described in A. C, LAX3 expression in the wild type (WT), lbd16, lbd18, and lbd16 lbd18 in response to auxin. Seven-day-old seedlings were incubated with auxin (20 μm IAA) for 8 h and subjected to qRT-PCR. Data are the mean ± se of three independent biological replications. Asterisks denote statistical significance (***, P < 0.001). D to K, GUS expression of ProLBD18:GUS (D and F), ProLBD18:GUS/lax3 (E and G), ProLBD16:GUS (H and J), and ProLBD16:GUS/lax3 transgenic Arabidopsis during LR development (I and K). Six-day-old light-grown seedlings were incubated without (D, E, H, and I) or with (F, G, J, and K) 20 μm IAA for 4 h and subjected to GUS staining. Bars = 50 μm.