Exocyst SEC3 and phosphoinositides define sites of exocytosis in pollen tube initiation and growth

F-Actin Mediated Focusing of Vesicles at the Cell Tip Is Essential for Polarized Growth

“…Since diffusion-based growth with ideal vesicle fusion kinetics is enough to support cell growth, we sought to estimate the true kinetics of vesicle membrane fusion during exocytosis. Docking and fusion of exocytic vesicles is a multistep process mediated by protein complexes such as Exocyst (Kulich et al, 2010;Bloch et al, 2016) and the SNARE complex (Lipka et al, 2007;El Kasmi et al, 2013), which we simplify by assuming that VAMP72 vesicles interact with one type of receptor on the plasma membrane at the cell tip. We also assume that this type of receptor has one reaction rate and facilitates the integration of vesicles into the plasma membrane.…”

Analysis of Exocyst Subunit EXO70 Family Reveals Distinct Membrane Polar Domains in Tobacco Pollen Tubes

“…We previously discovered the exocyst complex in plants (Eliáš et al, 2003) and have unraveled some of its functions, like pectin deposition in seed coats (Kulich et al, 2010), recycling of auxin transporters , cell plate initiation and maturation during cytokinesis (Fendrych et al, 2010), tip growth (Cole et al, 2005;Bloch et al, 2016), and defense against pathogen infection (Pe cenková et al, 2011). One of the most striking findings was the presence of many paralogs encoding the EXO70 subunit in plant genomes (Eliáš et al, 2003;Cvr cková et al, 2012).…”

ROP GTPases Structure-Function and Signaling Pathways

“…Analysis of the exocyst Sec3a subunit mutant demonstrated that polarized exocytosis is required for both the selection of the pollen tube initiation site and polarized growth (Bloch et al, 2016). It is not known whether ROPs are involved directly in the regulation of polarized exocytosis in pollen.…”

“…Pollen tubes are characterized by highly polarized oscillatory tip growth that depends on differential cell wall composition, tip-focused vesicle transport, specialized actin organization, and Ca 2+ , ROS, and pH gradients (Cárdenas et al, 2008;Cheung and Wu, 2008;Chebli et al, 2012;Bloch et al, 2016;Michard et al, 2017). Actin organizes into multiple forms in different regions of pollen tubes, including thick long actin cables that are axially aligned in the shank, a mesh ring or funnel-like F-actin structure known as the actin fringe in the subapical region, and a group of fine and less abundant F-actin in the pollen tube apex.…”