The wer-4 mutant allele enhances the cpc-1 phenotype and possesses a missense mutation in the WER gene. A, Seedling roots of the wild type (WT), cpc-1, cpc-1 wer-4, and wer-4 displaying their root-hair phenotypes. The arrows point to significantly shorter root hairs in the wer-4 root. Bar = 200 μm. B, Quantifications of root epidermis specification in seedling roots of various genetic backgrounds. WWGFP represents the WER::WER-GFP reporter. Error bars represent sd from three replicates. Statistical significance was determined by two-way ANOVA: ***, P < 0.001; ns, not significant. C, GL2::GUS reporter expression in seedling root tips of the wild type, cpc-1, and cpc-1 wer-4. Stars indicate H-position cell files. For each genotype, the left and right images show the same root under different magnifications. Bars = 50 μm. D, Alignment of the R2R3 domains of multiple Arabidopsis MYB proteins. The red arrow marks the position of the D105N residue substitution in the wer-4 mutant. The underlined residues indicate the three α-helices in each repeat. Stars indicate conserved Trp residues. Diamonds indicate conserved residues that directly associate with DNA bases in mammalian c-Myb. The green dotted frame indicates the conserved bHLH interaction domain.