Figure 8. TOPP4 controls the stability of DELLA proteins.

(A) The protein levels of GFP-RGA and GAI in wild-type, topp4-1, and TOPP4 overexpressing plants determined by immunoblotting using antibody against GFP or GAI. (B) The protein levels of RGA in wild-type, topp4-1, and three amiR-TOPP4 plants. (C) In vitro degradation of GFP-RGA. Total protein extractions from wild-type and topp4-1 plants were incubated with TOPP4, topp4-1, or 100 µM MG132 for the indicated time. (D) The degradation of GFP-RGA in wild-type and topp4-1 plants induced by 100 µM GA₃ or 100 µM GA₃ together with 50 µM CHX. The time refers to the period that seedlings were treated with GA₃ or GA₃ and CHX before immunoblotting analysis. Numbers under lanes indicate relative band intensities that were quantified and normalized for each panel. The coomassie brilliant blue-stained RbcS protein was used as loading controls.