The Arabidopsis Exocyst Complex Is Involved in Cytokinesis and Cell Plate Maturation

Abstract

Cell reproduction is a complex process involving whole cell structures and machineries in space and time, resulting in regulated distribution of endomembranes, organelles, and genomes between daughter cells. Secretory pathways supported by the activity of the Golgi apparatus play a crucial role in cytokinesis in plants. From the onset of phragmoplast initiation to the maturation of the cell plate, delivery of secretory vesicles is necessary to sustain successful daughter cell separation. Tethering of secretory vesicles at the plasma membrane is mediated by the evolutionarily conserved octameric exocyst complex. Using proteomic and cytologic approaches, we show that EXO84b is a subunit of the plant exocyst. Arabidopsis thaliana mutants for EXO84b are severely dwarfed and have compromised leaf epidermal cell and guard cell division. During cytokinesis, green fluorescent protein-tagged exocyst subunits SEC6, SEC8, SEC15b, EXO70A1, and EXO84b exhibit distinctive localization maxima at cell plate initiation and cell plate maturation, stages with a high demand for vesicle fusion. Finally, we present data indicating a defect in cell plate assembly in the exo70A1 mutant. We conclude that the exocyst complex is involved in secretory processes during cytokinesis in Arabidopsis cells, notably in cell plate initiation, cell plate maturation, and formation of new primary cell wall.

Vesicle Dynamics during Plant Cell Cytokinesis Reveals Distinct Developmental Phases

“…It is intriguing that the exocyst complexes move back and forth between the plasma membrane and the cytoplasm (Fendrych et al, 2010(Fendrych et al, , 2013. In addition, FM4-64 is observed at the cell plate as early as the IPA stage, and phosphatidylinositol-4-phosphate (originating from both the Golgi and the plasma membrane) is integrated into the growing cell plate (Vermeer et al, 2009), with the accumulation of YFP-2x-FYVE-positive endosomes at the periphery of the growing cell plate (Vermeer et al, 2006(Vermeer et al, , 2009.…”

“…The initiation of the formation of the cell plate corresponds to the fusion of vesicles in the CPAM enriched in exocyst-tethering complexes (including EXO70A1 and EXO84b; Fendrych et al, 2010;Rybak et al, 2014). It is intriguing that the exocyst complexes move back and forth between the plasma membrane and the cytoplasm (Fendrych et al, 2010(Fendrych et al, , 2013.…”

The Exocyst at a Glance

“…At telophase, the exocyst directs the trafficking of vesicles to the cell-cell junction for abscission (Martin-Cuadrado et al, 2005;Wang et al, 2002 and. In Arabidopsis, the exocyst subunits are localized to the separation sites during initiation of the cell plate and maturation, when vesicle fusion is in high demand (Fendrych et al, 2010). In mammalian cells, the exocyst is involved in the trafficking of secretory vesicles to the cleavage furrow and midbody under the control of Rab11 and RalA (Chen et al, 2006;Fielding et al, 2005;Neto et al, 2013).…”

Endosidin2 targets conserved exocyst complex subunit EXO70 to inhibit exocytosis

“…As an important component of the exocyst complex that mediates exocytosis, EXO70 regulates, for example, neurite outgrowth, epithelial cell polarity establishment, cell motility, and cell morphogenesis in animal cells (2)(3)(4)(5)(6). In plants, EXO70 proteins participate in polarized pollen tube growth, root hair growth, deposition of cell wall material, cell plate initiation and maturation, defense, and autophagy (7)(8)(9)(10)(11)(12). In humans, EXO70 mediates the trafficking of the glucose transporter Glut4 to the plasma membrane that is stimulated by insulin and involved in the development of diabetes (13).…”