Female control of male gamete delivery during fertilization in Arabidopsis thaliana.

Fertilization in both animals and plants relies on the correct targeting of the male gametes to the female gametes. In flowering plants, the pollen tube carries two male gametes through the maternal reproductive tissues to the embryo sac, which contains two female gametes. The pollen tube then releases its two male gametes into a specialized receptor cell of the embryo sac, the synergid cell. The mechanisms controlling this critical step of gamete delivery are unknown. Here, data based on the new sirène (srn) mutant of Arabidopsis thaliana provide the first evidence for female control over male gamete delivery. Live imaging of fertilization shows that wild-type pollen tubes do not stop their growth and do not deliver their contents in srn embryo sacs.