Osmophoresis – a possible mechanism for vesicle trafficking in tip-growing cells

Abstract

A mechanism for polarized transport of vesicles by means of osmotic propulsions is proposed and substantiated for tip-growing cells. An analysis is presented which shows that in pollen tubes the gradient of cytosolic water potential can drive vesicle movement either in the anterograde or retrograde direction, depending on the vesicle position, its radius and the phase of growth oscillation. The importance of transcellular water flow for cytoskeletal dynamics and cell motility is highlighted.

Tip‐localized Ca2+‐permeable channels control pollen tube growth via kinase‐dependent R‐ and S‐type anion channel regulation

“…However, quantifications of the cell wall stiffness, an indirect measurement of cell turgor, demonstrated no correlation between growth speed and turgor as well (Zerzour et al ., ). A model for osmophoresis has recently been developed in the context of PT growth (Lipchinsky, ). The apical [anion] cyt gradient was suggested to build up an apical water potential gradient increasing toward the tip (Lipchinsky, ).…”

“…A model for osmophoresis has recently been developed in the context of PT growth (Lipchinsky, ). The apical [anion] cyt gradient was suggested to build up an apical water potential gradient increasing toward the tip (Lipchinsky, ). High water potentials at the extreme apex are predicted to allow vesicle movement toward the tip where exocytosis events promote growth.…”

Signaling with Ions: The Keystone for Apical Cell Growth and Morphogenesis in Pollen Tubes

“…The anion channel AtSLAH3 is partly responsible for this conductance (Gutermuth et al, 2013), but other anion channels expressed in the PT may be involved (Tavares et al, 2011a), like members from the AtALMT family (Meyer et al, 2010). The existence of a gradient and fluxes of anions of such magnitude has been proposed to be physically sufficient to create conditions for an osmotic gradient strong enough to generate thrust for vesicles to move toward a minimum osmotic potential at the apex through the process of osmophoresis (Lipchinsky, 2015). While proposed on theoretical grounds, the existence of biophysical mechanisms for the vectorial movement of vesicles in the clear zone is an exciting new prospect calling for experimental validation.…”