Spatial and temporal integration of signalling networks regulating pollen tube growth.

The overall function of a cell is determined by its contingent of active signal transduction cascades interacting on multiple levels with metabolic pathways, cytoskeletal organization, and regulation of gene expression. Much work has been devoted to analysis of individual signalling cascades interacting with unique cellular targets. However, little is known about how cells integrate information across hierarchical signalling networks. Recent work on pollen tube growth indicates that several key signalling cascades respond to changes in cell hydrodynamics and apical volume. Combined with known effects on cytoarchitecture and signalling from other cell systems, hydrodynamics has the potential to integrate and synchronize the function of the broader signalling network in pollen tubes. This review will explore recent work on cell hydrodynamics in a variety of systems including pollen, and discuss hydrodynamic regulation of cell signalling and function including exocytosis and endocytosis, actin cytoskeleton reorganization, cell wall deposition and assembly, phospholipid and inositol polyphosphate signalling, ion flux, small G-proteins, fertilization, and self-incompatibility. The combined data support a newly emerging model of pollen tube growth.