Figure 2.

oBIR3-iBRI1 Chimeras Constitutively Activate Brassinosteroid Signaling.

(A) Hypocotyl growth assay of dark-grown seedlings in the presence and absence of the BR biosynthesis inhibitor BRZ. Representative seedlings are shown in the top panel, with the quantification of the data (relative inhibition of hypocotyl growth in the presence of BRZ plotted together with lower and upper confidence intervals) below. For each sample n = 50 hypocotyls from five different half-strength MS plates were measured. The # numbers indicate independent lines. Steady state protein levels were quantified by immunoblot with an anti-GFP antibody (detecting the mCitrine tag present in each chimera); the Ponceau-stained membrane is shown as loading control. Homozygous bri1-null plants could be obtained only upon expression of oBIR3-iBRI1, but not of the control chimeras. Bar = 0.5 cm.

(B) and (C) Anti-BES1 immunoblot on oBIR3-iBRI chimeras in the bri1-null (B) and det2 (C) backgrounds, with the corresponding Ponceau-stained membranes.

(D) co-IP experiment of oBIR3-iBRI1 chimera and SERK3. Shown alongside are the input immunoblots and the Ponceau-stained membrane. WT, wild type.