Abstract
During sexual reproduction in higher plants, a pollen tube grows through a pistil to deliver sperm cells to a female gametophyte. In the process, controlling direction of the pollen tube growth is essential for successful fertilization. Physiological studies indicated that an ovule emits guidance signals to attract or repel a pollen tube. Recently, we showed LUREs, the polypeptides secreted from synergid cells in the female gametophyte of Trenia fournieri, have an activity that attracts pollen tubes. However, these molecules identified so far are insufficient to understand the mechanism of pollen tube guidance. For example, if the guidance signal were merely diffusible attractants like LUREs, many pollen tubes would rush into unfertilized ovules. But in reality, only single pollen tube accurately targets to an ovule. This suggests a mechanism of polyspermy block by which fertilized ovule prevents arrival of second pollen tube. In order to study the polyspermy block in higher plants, I performed a visual screening to find mutants containing ovules that attract more than one pollen tube in Arabidopsis thaliana.
