Pollen tip growth: Control of cellular morphogenesis through intracellular trafficking

Abstract

The control of cellular growth in pollen tubes occurs through the finetuning of intracellular transport and secretion processes. This does not only apply to the basic genesis of the cylindrical cell through polar expansion but also to the pollen tube's specialized skills including its capacity to respond to directional guidance cues and its ability to perform invasive growth. The control of these specialized activities by intracellular trafficking occurs through the strategic deposition of cell wall material and cell wall modifying agents that soften or stiffen the wall with the aim to regulate the cell wall's mechanical properties both in time and space. Directional and invasive growth of the pollen tube is crucial for successful sperm delivery and fertilization. The mechanisms underlying the regulation and logistics of the endomembrane trafficking in the pollen tube therefore have a direct impact on pollen tube elongation and male fertility. Here, we relate pollen tube morphogenesis and its biological functionality to the intracellular processes that control cellular growth behavior and allow the cell to respond to environmental cues.