The C-terminus of ubiquitin is important for PM internalization. Tobacco mesophyll protoplasts and leaf epidermal cells expressing the plasmids indicated below. A. Box-GFP-UbΔGG is not internalized and localizes to the PM like Box-GFP (B) and does not localize to punctate structures like Box-GFP-Ub (C). D-F: Localization of the reporters given above in planta, confirming the results from (A-C). Vacuolar transport of RFP-TMD23-UbΔGG is not affected by the ΔGG mutation (G), compared to RFP-TMD23-Ub (H). Its phenotype thus differs from that of the PM marker RFP-TMD23 (I). J-L: Confirmation of the localization from G-I in leaf epidermal cells. Scale bars = 5 μm.