Extended Data Fig. 3: Expression patterns of BR biosynthetic enzymes in the root elongation zone.

a, The expression domains of several genes expanding in the root elongation zone. DWF4–GFP expression was very broad and the GFP signal could be observed in all cell types of the elongation zone. The CPD–GFP expression was restricted to the stele of the elongation zone. The DET2–GFP expression was limited to the stele, similarly to the expression of CPD–GFP. The ROT3–GFP expression had maxima in the stele, but a signal also occured in all other cell types. The expression of the ROT3 homolog, CYP90D1, was limited to the stele. The BR6OX1 and BR6OX2 enzymes both had expression maxima in endodermis and pericycle, but the expression pattern of the BR6OX1 enzyme was expanded in all cell types. Roots were stained with propidium iodide. Scale bars, 50 µm. b, Increase in the expression levels of most of the BR biosynthetic enzymes in the transition and elongation zones as visualized by colour-based fluorescence intensity coding. All reporter lines showed an increase in expression higher in the root except for DET2–GFP and GFP–BR6OX2. The signal intensity of the BR receptor, BRI1-mCITRINE in pBRI1:BRI1-mCITRINE/bri1 line did not exhibit signal increase in the elongation zone. Maximum Z projections of the same roots from Fig. 2a are shown for BR biosynthetic enzyme lines. Scale bars, 100 µm. c, Roots expressing pBR6OX2:BR6OX2-GFP (left panel). Increased GFP signal could be observed in the elongation zone as visualized by colour-based fluorescence intensity coding (right panel). Scale bars, 100 µm. All transgenic lines in (a), (b) and (c) were imaged in more than three independent experiments. Representative images are shown. d, Expression levels of BR biosynthetic genes and BRI1 in the Arabidopsis root. All BR biosynthetic genes had an increased expression in the elongation zone, while BRI1-mCITRINE exhibited the highest expression in the meristem. Extracted from Huang and Schiefelbein (2015). MZ, meristematic zone; EZ, elongation zone; DZ, differentiation zone. Symbols depict individual values. Bars represent s.d.