Organelle motility in the pollen tube: a tale of 20 years.

Organelle movement is an evident feature of pollen tubes and is essential for the process of tube growth because it enables the proper distribution of organelles and the accumulation of secretory vesicles in the tube apex. Organelles move along the actin filaments through dynamic interactions with myosin but other proteins are probably responsible for control of this activity. The role of microtubules and microtubule-based motors is less clear and somewhat enigmatic. Nevertheless, the pollen tube is an excellent cell model in which to study and analyse the molecular mechanisms that drive and control organelle motility in relation to plant cell expansion. Current knowledge and the main scientific discoveries in this field of research over the last 20 years are summarized here. Future prospects in the study of the molecular mechanisms that mediate organelle transport and vesicle accumulation during pollen tube elongation are also discussed.