Figure 8.

While Aleu-RFP, GFP-Vam3, and αTIP-YFP Exit the ER in COPII Vesicles, CBL6-RFP Trafficking Is sec12 Independent.

This tobacco leaf infiltration experiment was based on an Agrobacterium strain harboring a new dual expression vector encoding the Golgi marker ST-YFP ([A] to [D]) or ST-RFP (E) as well as a Sec12 overexpression cassette for inhibition of COPII-mediated ER export. This vector was cotransformed with Agrobacterium strains harboring either CBL6-RFP ([A] and [B]), Aleu-RFP (C), GFP-Vam3 (D), and αTIP-YFP (E). Only cells displaying ER-retained Golgi marker ST-YFP were imaged as they contained inhibitory levels of the Sec12 gene product. (A) shows the midsection of a transfected cell in which it is possible to evaluate normal CBL6-RFP staining of the tonoplast. (B) shows the cortex of the same cell in (A) where it can be noted that CBL6-RFP has not redistributed to the ER, in spite of strong ER retention of the Golgi marker ST-YFP, which served as positive control for Sec12 action. On the contrary, Sec12 overexpression caused redistribution of GFP-Vam3 (C), Aleu-RFP (D), as well as αTIP-YFP (E) into the ER. Bars = 10 μm.