Abstract
The concept of the pollen-tube attractant was proposed in the late 19th century. Since then, many plant biologists tried to identify the attractant. We identified two cysteine-rich peptides (polypeptides) specifically expressed in the synergid cell as pollen-tube attractants, by using a unique plant Torenia fournieri, which possesses a protruding embryo sac (Okuda et al. 2009). There were at least two attractant peptides, and they were named as LURE1 and LURE2. LUREs were defensin-like peptides and were secreted to the micropylar end of the synergid cell. Refolded recombinant peptides showed a strong activity to attract pollen tubes. The property of the attraction activity of LUREs were similar to those of synergid cells of Torenia, as LUREs did not attract pollen tubes germinated on the medium and pollen tubes of other plant species. Moreover, pollen tube attraction was impaired when morpholino anti-sense oligos were injected into the embryo sac by using a newly developed laser-assisted microinjector. These results indicate that LUREs are true attractant derived from the synergid cell. In this review article, I will summarize identification of LUREs and will discuss future perspectives.
