NaTrxh uses the ER/Golgi secretion elements to reach the apoplast. (A) Transient expression in onion cells of different proteins with the ER retention signal (KDEL) toward the C-termini. (A-1) (A-4) (A-7) GFP fluorescence. (A-2) (A-5) (A-8) Nucleus staining with propidium iodide. (A-3) (A-6) (A-9) Merged images. Scale bars = 20 μm. (B) Transient expression of p11:GFP, NaTrxh:GFP and Nβ: GFP in onion cells treated with BFA (50 μg/ml). (B-1) (B-3) (B-5) GFP fluorescence. (B-2) (B-4) (B-6) Bright fields merged with fluorescence images. The observations were made after plasmolysis with 1 M NaCl. CW: cell wall; M. plasma membrane. Scale bars = 50 μm.