Figure 1.

A simplified map of the secretory pathway of higher plants. Cargo synthesized and processed in the endoplasmic reticulum (ER) is transferred directly to the closely apposed and mobile Golgi apparatus (G). However, direct transfer of some storage proteins to the vacuole may occur (route 1). Proteins destined for the protein storage vacuole may leave the Golgi at the cis- and trans-compartments (route 2), whilst exocytotic cargo predominantly leaves at the trans-face (route 3). Product destined for the lytic vacuole is sorted at the trans-Golgi and routed in a clathrin- and receptor-dependent fashion through a prevacuolar compartment (PVC, route 4). Endocytosed material and recycling plasma membrane proteins are internalized into an endosome-like compartment (route 5), which might transfer material to, fuse with or mature into the PVC (route 6). The exact role of vesicles in the transfer between putative endosomes, PVCs and a lytic vacuole is unclear.