Abstract
The precise gametophytic interactions between the pollen tube and the embryo sac are necessary for successful fertilization. However, the physiological and molecular mechanism of the interactions remains largely unknown due to thick layers of surrounding sporophytic cells. We established an in vitro system in Torenia and showed that some diffusible signal was derived from the embryo sac (Higashiyama et al. 1998, Plant Cell). By laser cell ablation, we showed that the attractant was emitted from two synergid cells adjacent to the egg cell (Higashiyama et al. 2001, Science). The attractant was neither the calcium ion nor malic acid but showed species specificities in closely relating Vandellia species (Higashiyama et al. 2003 Curr. Opin. Plant Biol.). Characterization of chemical properties of the attractant using a micropipette is now on progress. We will also talk about our recent trial visualizing two sperm cells during fertilization processes.
