Figure 8. A proposed model to illustrate how BR signaling regulates root epidermal cell fate.
Without BR early signaling, WER expression is reduced, and the activated GSK3-like kinases phosphorylate EGL3 and TTG1 in both H and N cells, leading to reduced formation and/or activity of the WER-EGL3/GL3-TTG1 complex, which inhibits GL2 expression in some N cells. With enhanced BR early signaling, WER expression is enhanced in both H and N cells, and the GSK3-like kinases activity is inhibited, leading to reduced phosphorylation of EGL3 and TTG1 in both cell types. Thus, WER-EGL3-TTG1 and WER-GL3-TTG1 complexes with transcriptional activity are formed in H and N cells, respectively, to promote GL2 expression and non-root hair cell fate. BR: brassinosteroid.
Figure 8—figure supplement 1. WER expression pattern in the root early meristem and its expression level in the bin2-3 bil1 bil2 and wild type Col-0.
(A) Transverse section from the root meristem of the PWER::GUS transgenic plant. Scale bar, 25 μm. (B) The WER expression level was enhanced in the bin2-3 bil1 bil2 mutant. CPD (CONSTITUTIVE PHOTOMORPHOGENIC DWARF), a BR biosynthetic gene feedback inhibited by BR signaling, was used as a control. The expression level of CPD and WER in WS-2 was normalized to ‘1’, and a U-BOX gene (At5g15400) was used as an internal control. Error bars indicate SD. **p<0.01 with a two-tailed Student's t test. BR: brassinosteroid.