Received June 27, 2008
Returned for revision October 1, 2008
Accepted November 4, 2008
Maternal Control of Male-Gamete Delivery in Arabidopsis Involves a Putative GPI-Anchored Protein Encoded by the LORELEI Gene
Arnaud Capron 1, Mathieu Gourgues 2, Lissiene S. Neiva 2, Jean-Emmanuel Faure 2, Frederic Berger 2, Gabriela Pagnussat 1, Anjali Krishnan 1, Cesar Alvarez-Mejia 3, Jean-Philippe Vielle-Calzada 3, Yuh-Ru Lee 1, Bo Liu 1, and Venkatesan Sundaresan 1*
1 Department of Plant Biology, University of California, Davis, California 95616
2 Ecole Normale Supérieure de Lyon, Unité Mixte de Recherche 5667, Reproduction et Développement des Plantes, Lyon cedex 07, France
3 National Laboratory of Genomics for Biodiversity, Cinvestav, Guanajuato, Mexico
* To whom correspondence should be addressed. E-mail: sundar{at}ucdavis.edu.
In Angiosperms, the male gametes are delivered to the female gametes through the maternal reproductive tissue by the pollen tube. Upon arrival, the pollen tube releases the two sperm cells, permitting double fertilization to take place. Although the critical role of the female gametophyte in pollen tube reception has been demonstrated, the underlying mechanisms remain poorly understood. Here, we describe lorelei, an Arabidopsis thaliana mutant impaired in sperm cell release, reminiscent of the feronia/sirène mutant. Pollen tubes reaching lorelei embryo sacs frequently do not rupture but continue to grow in the embryo sac. Furthermore, lorelei embryo sacs continue to attract additional pollen tubes after arrival of the initial pollen tube. The LORELEI gene is expressed in the synergid cells prior to fertilization and encodes a small plant-specific putative glucosylphosphatidylinositol-anchored protein (GAP). These results provide support for the concept of signaling mechanisms at the synergid cell membrane by which the female gametophyte recognizes the arrival of a compatible pollen tube and promotes sperm release. Although GAPs have previously been shown to play critical roles in initiation of fertilization in mammals, flowering plants appear to have independently evolved reproductive mechanisms that use the unique features of these proteins within a similar biological context.
