Fig. 4

Allelic variation of BSK3 determines plant sensitivity to BR. a–c Brassinosteroid sensitivity of wild-type (Col-0), bsk3,4,7,8, and independent transgenic lines expressing sequences coding for either the BSK3-P or BSK3-L variant under the control of the BSK3_Col-0 promoter. Appearance (a), primary root length (b), and hypocotyl length (c) of 6-day-old plants. Numbers in red indicate relative root or hypocotyl length (+BL/−BL). Different letters indicate significant differences for relative root or hypocotyl length at P < 0.05 according to one-way ANOVA and post-hoc Tukey’s test. d, e Primary root (d) and hypocotyl (e) growth responses of natural accessions carrying BSK3-P or BSK3-L to the exogenous supply of 1 µM 24-epibrassinolide (n = 29 and 27 accessions for P and L haplotypes, respectively). f–h Root growth of wild-type (Col-0), bsk3,4,7,8, and independent transgenic lines expressing sequences coding for either the BSK3-P or BSK3-L variant under the control of the CaMV 35 S promoter. Appearance (f), primary root length (g), and root growth rate (h) of 6-day-old plants. Horizontal lines show medians; box limits indicate the 25th and 75th percentiles; whiskers extend to 5th and 95th percentiles. Asterisks indicate statistically significant differences to wild-type (in red) or to bsk3,4,7,8 (in black), or between two BSK3 protein haplotypes (in black) according to Welch’s t-test (**P < 0.01; ***P < 0.001; ****P < 0.0001). Scale bars, 1 cm