Persistent directional growth capability in Arabidopsis thaliana pollen tubes after nuclear elimination from the apex

During the double fertilization process, pollen tubes deliver two sperm cells to an ovule containing the female gametes. In the pollen tube, the vegetative nucleus and sperm cells move together to the apical region where the vegetative nucleus is thought to play a crucial role in controlling the direction and growth of the pollen tube. Here, we report the generation of pollen tubes in Arabidopsis thaliana whose vegetative nucleus and sperm cells are isolated and sealed by callose plugs in the basal region due to apical transport defects induced by mutations in the WPP domain-interacting tail-anchored proteins (WITs) and sperm cell-specific expression of a dominant mutant of the CALLOSE SYNTHASE 3 protein. Through pollen-tube guidance assays, we show that the physiologically anuclear mutant pollen tubes maintain the ability to grow and enter ovules. Our findings provide insight into the sperm cell delivery mechanism and illustrate the independence of the tip-localized vegetative nucleus from directional growth control of the pollen tube. Arabidopsis pollen contains a vegetative nucleus and two sperm cells that move to the apical region during pollen tube growth. Here, Motomura et al. make use of transgenic pollen with immobilized nuclei and show that, contrary to previous assumptions, movement of the vegetative nucleus is not needed for pollen tube guidance.