Quantitative RT-PCR gene expression analyses of EXPANSIN A5 (AtEXPA5, At3 g29030). (A) HisAtRALF1-treated 10-d-old wild-type plants. Total RNA was extracted from roots after 30 min of treatment with 0, 0.1, 0.5 and 1 μM of the peptide. (B) Dark-grown 4-d-old wild-type plants treated with HisAtRALF1. Total RNA was extracted from hypocotyls after 30 min of treatment with 0, 0.1, 0.5 and 1 μM of the peptide. (C) Arabidopsis plants (10-d-old) treated with 100 nM of brassinolide (BL) for 6 h or pre-treated with 100 nM of BL for 5.5 h and treated with 1 μM of HisAtRALF1 for 30 min. Control plants were treated with H2O. Total RNA was extracted from the roots after each treatment. (D) AtRALF1-overexpressing (35S:AtRALF1), AtRALF1-silencing (irAtRALF1) and wild-type (WT) plants. Total RNA was extracted from roots of 10-d-old plants. Error bars indicate SD (* = p value < 0.05,** = p value < 0.01, t-test). Glyceraldehyde-3-phosphate dehydrogenase (GAPDH, At1 g13440) expression was used as a control. All experiments were repeated at least 3 times (independent biological replicates).