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Science 338 (6110): 1093-1097

Copyright © 2012 by the American Association for the Advancement of Science

Egg Cell–Secreted EC1 Triggers Sperm Cell Activation During Double Fertilization

Stefanie Sprunck,1,* Svenja Rademacher,1,{dagger} Frank Vogler,1 Jacqueline Gheyselinck,2,{ddagger} Ueli Grossniklaus,2 Thomas Dresselhaus1

Abstract: Double fertilization is the defining characteristic of flowering plants. However, the molecular mechanisms regulating the fusion of one sperm with the egg and the second sperm with the central cell are largely unknown. We show that gamete interactions in Arabidopsis depend on small cysteine-rich EC1 (EGG CELL 1) proteins accumulating in storage vesicles of the egg cell. Upon sperm arrival, EC1-containing vesicles are exocytosed. The sperm endomembrane system responds to exogenously applied EC1 peptides by redistributing the potential gamete fusogen HAP2/GCS1 (HAPLESS 2/GENERATIVE CELL SPECIFIC 1) to the cell surface. Furthermore, fertilization studies with ec1 quintuple mutants show that successful male-female gamete interactions are necessary to prevent multiple–sperm cell delivery. Our findings provide evidence that mutual gamete activation, regulated exocytosis, and sperm plasma membrane modifications govern flowering plant gamete interactions.

1 Cell Biology and Plant Biochemistry, Biochemie-Zentrum Regensburg, University of Regensburg, Universitätsstrasse 31, D-93053 Regensburg, Germany.
2 Institute of Plant Biology and Zürich-Basel Plant Science Center, University of Zürich, Zollikerstrasse 107, CH-8008 Zürich, Switzerland.

{dagger} Present address: Plant Breeding Center of Life and Food Sciences Weihenstephan, Technische Universität München, Emil-Ramann-Strasse 4, D-85354 Freising, Germany.

{ddagger} Present address: Département de Biologie Moléculaire Végétale, Université de Lausanne, Biophore 4403, CH-1015 Lausanne, Switzerland.

* To whom correspondence should be addressed. E-mail: stefanie.sprunck{at}biologie.uni-regensburg.de

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Gene expression profiles in rice gametes and zygotes: identification of gamete-enriched genes and up- or down-regulated genes in zygotes after fertilization.
M. Abiko, H. Maeda, K. Tamura, I. Hara-Nishimura, and T. Okamoto (2013)
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