Identification and characterization of TcCRP1, a pollen tube attractant from Torenia concolor

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.