A Mobile Secretory Vesicle Cluster Involved in Mass Transport from the Golgi to thePlant Cell Exterior
Kiminori Toyooka,a Yumi Goto,a Satoru Asatsuma,a,b Masato Koizumi,a Toshiaki Mitsui,c and Ken Matsuokaa,b,1
Plant Science Center, Tsurumi-ku, Yokohama 230-0045,Japan of Plant Nutrition, Faculty of Agriculture, Kyushu University, Higashi-ku, Fukuoka 812-8581, Japan c Laboratories of Plant and Microbial Genome Control, Graduate School of Science andTechnology, Niigata University, Ikarashi, Nishi-ku, Niigata 950-2181, Japan
Secretory proteins and extracellular glycans are transported to the extracellular space during cell growth. Thesematerials are carried in secretory vesicles generated at the trans-Golgi network (TGN). Analysis of the mammalian post-Golgi secretory pathway demonstrated the movement of separated secretory vesicles inthe cell. Using secretory carrier membrane protein 2 (SCAMP2) as a marker for secretory vesicles and tobacco (Nicotiana tabacum) BY-2 cell as a model cell, we characterized the transport machinery inplant cells. A combination of analyses, including electron microscopy of quick-frozen cells and four-dimensional analysis of cells expressing ﬂuorescent-tagged SCAMP2, enabled the identiﬁcation of aclustered structure of secretory vesicles generated from TGN that moves in the cell and eventually fuses with plasma membrane. This structure was termed the secretory vesicle cluster (SVC). The SVCwas also found in Arabidopsis thaliana and rice (Oryza sativa) cells and moved to the cell plate in dividing tobacco cells. Thus, the SVC is a motile structure involved in mass transport from the Golgito the plasma membrane and cell plate in plant cells.
INTRODUCTION The division and expansion of cells requires trafﬁcking of lipids, proteins, and polysaccharides to the plasma membrane (PM) and...