Fertilization in flowering plants is dependent on a protein that is secreted by the egg cell and activates incoming sperm.
Stefanie Sprunck at the University of Regensburg in Germany and her colleagues show that, in the model plant Arabidopsis thaliana, the arrival of sperm cells near the egg causes the release of a protein they call EGG CELL 1 (EC1). This triggers the redistribution of a second protein — one linked to fusion of the sex cells, or gametes — from inside the sperm to the sperm cell surface.
Sperm cells interacting with mutant Arabidopsis eggs that have faulty ec1 genes failed to fuse, and the plant's pollen tubes continued to deliver sperm into the embryo sac. These results suggest that EC1 controls gamete fusion.
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Plant fertilization protein found. Nature 491, 640 (2012). https://doi.org/10.1038/491640b