Figure 13.

Anterograde and retrograde traffic between the ER and the Golgi in higher plants is accomplished by a short-range secretory and recycling unit. (A) Cartoon showing the close proximity of ERES and ERIS in a domain of the ER which in size approximates the diameter of the Golgi stack. (B) This cartoon represents a new model for ER-Golgi transport in higher plants. Golgi stacks move intermittently over the surface of the ER. They are in tight association with the ER through a joint scaffolding matrix of tethering factors (dotted blue line). As Golgi stacks move they capture individual COPII vesicles released from ERES at the surface of the ER (“mobile phase”) and release COPI vesicles. Both types of vesicles accumulate in the ER-Golgi interface. When the Golgi stacks temporarily stop moving (“docking phase”) fusion of COPI and COPII vesicles to their respective target membranes occurs. Golgi stacks stop at ERIS as marked by the presence of “SYP72 nodules” on the ER.