Abstract
Secretory proteins and extracellular glycans are transported to the extracellular space by secretory vesicles, which are generated at the trans-Golgi network. Secretory vesicles are well characterized in several mamalian cells, but this compartment has not yet been elucidated in plants. Secretory carrier membrane protein 2 (SCAMP2) is one of the components of the vesicles. We analyzed the subcellular localization of this protein in tobacco BY-2 cells and reported that it existed in a clustered structure of secretory vesicles, which we termed secretory vesicle cluster (SVC). SVC is involved in post-Golgi secretion as SVC contained pectin and secretory protein, and fused with plasma membrane or cell plate. SVC-like structures were also found in tobacco root tip cells, rice suspension cells and epidermal cells of Arabidopsis cotyledon. These results indicated that SVC plays a role in the secretory pathways in wide variety of plants.
To investigate the formation mechanism of SVC, we set up a condition to prepare SVC-rich fraction from BY-2 cells combining several density gradient centrifugation using SCAMP2-YFP as a marker. Now, we are on the way to identify proteins in the SVC.
