Abstract
Secretory and plasma membrane proteins, and extracellular glycans are transported to plasma membrane and extraellular space during cell growth. Secretory vesicles generated at the trans-Golgi network (TGN) are known to carry these materials. However, how secretory vesicles are transported to plasma membrane in plant cells has been elusive. Here we report a undescribed mobile unit, which we term secretory vesicle cluster (SVC), in post-TGN transport pathway in tobacco BY-2 cells. Electron microscopy of quick-frozen cells, four-dimensional analysis of cells expressing fluorescent-tagged secretory carrier membrane protein 2 and other analyses indicated that SVC is generated from TGN, moves in the cell and fuses with the plasma membrane. Thus, the SVC is a mobile structure involved in mass transport from TGN to plasma membrane and cell exterior.
