Background and aims: During sexual reproduction in higher angiosperms, the pollen tubes are directed to the ovules in the pistil to deliver sperm cells. This pollen tube attraction is highly species specific, and a group of small secreted proteins, TfCRPs, are necessary for this process in Torenia fournieri.
Methods: A candidate pollen tube attractant protein in Torenia concolor, a related species of T. fournieri, was isolated and the attractant abilities between them were compared.
Key results: TcCRP1, an orthologous gene of TfCRP1 from T. concolor, is expressed predominantly in the synergid cell. The gene product attracted pollen tubes in a concentration-dependent manner, but attracted fewer pollen tubes from the other species.
Conclusions: The results indicated that this class of CRP proteins is a common pollen tube attractant in Torenia species. The sequence diversity of these proteins is important for species-specific pollen tube attraction.