title: Egg cell-secreted EC1 triggers sperm cell activation during double fertilization.
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.
authors.affiliation: Cell Biology and Plant Biochemistry, Biochemie-Zentrum Regensburg, University of Regensburg, Universitätsstrasse 31, D-93053 Regensburg, Germany. stefanie.sprunck@biologie.uni-regensburg.de
authors.forename: Stefanie
authors.initials: S
authors.lastname: Sprunck
authors.forename: Svenja
authors.initials: S
authors.lastname: Rademacher
authors.forename: Frank
authors.initials: F
authors.lastname: Vogler
authors.forename: Jacqueline
authors.initials: J
authors.lastname: Gheyselinck
authors.forename: Ueli
authors.initials: U
authors.lastname: Grossniklaus
authors.forename: Thomas
authors.initials: T
authors.lastname: Dresselhaus
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D002352:Carrier Proteins / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D005089:Exocytosis; D005306:Fertilization; D035264:Flowers / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D008969:Molecular Sequence Data; D005810:Multigene Family; D056771:Ovule / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D011058:Pollen / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D021382:Protein Sorting Signals; D014158:Transcription, Genetic
chemical_list: D029681:Arabidopsis Proteins; D002352:Carrier Proteins; C548817:HAP2 protein, Arabidopsis; D021382:Protein Sorting Signals