Deep imaging revealed dynamics and signaling in one-to-one pollen tube guidance

ABSTRACT In angiosperms, pollen tube guidance allows sperm cell delivery to the female gametes within the ovule, which are deeply embedded in a flower. However, when an ovary includes multiple pollen tubes and ovules, it is unclear how each ovule is fertilized one-to-one by a pollen tube. Here, our two-photon imaging revealed the pollen tube dynamics in living ovaries. The number of pollen tubes and ovule maturity affected the target selection among multiple ovules. On the inner surface of the septum epidermis within the transmitting tract, pollen tube behavior and emergence were regulated by the ovular sporophytic signals. In funicular guidance, the second pollen tube was strictly repelled by the FERONIA and LORELEI-dependent gametophytic signal, especially more than 45 minutes after the first pollen tube had passed. Such highly spatiotemporal regulation mechanisms in the one-to-one pollen tube guidance may allow angiosperms to produce more offspring in nature.