Nanovesicles Are Secreted during Pollen Germination and Pollen Tube Growth: A Possible Role in Fertilization

摘要

During recent decades, a novel mechanism of secretion has been identified in a wide range of mammalian cells. It involves the release of bioactive membrane nanovesicles (30-100nm), termed exosomes, upon the fusion of multivesicular bodies with the plasma membrane (Thery et al., 2009). Exosomes are implicated in diverse functions, such as scavenging of archaic proteins, intercellular messengers delivering cell-specific signals, and vehicles for transmissible pathogens. Exosomes have also been described in other organisms such as bacteria, Drosophila, and fungi. Concerning exosome-like vesicles in plants, only one study has demonstrated their existence in sunflower apoplastic fluid (Regente et al., 2009), although several pieces of evidence have suggested that they could be involved in cell-wall-associated defense response upon pathogen attack (e.g. Meyer et al., 2009). However, no information is available on exosome-like vesicle release during pollen germination and pollen tube growth, despite the importance of the vesicle trafficking network in such an event (see Moscatelli and Idilli, 2009).