During plant pathogen interactions, specific molecules elicit defense response of plant cells. Cryptogein, an elicitin produced by the pathogenic fungus Phytophtora cryptogea, induces a hypersensitive response (HR) in tobacco plants. The mode of action for cryptogein starts with recognition of this elicitor by an unidentified plasma membrane (PM) receptor. This ligand-receptor binding trigger a cascade of events at the PM level including rapid calcium influx, ions effluxes, extracellular medium alcalinization and plasma membrane depolarization both in tobacco plants and suspension cells. These events lead to the activation of plasma membrane-bound NADPH oxidase, NtrbohD, that is responsive for reactive oxygen species (ROS) production (1). In animals cells, when extracellular ligands bind to their receptors at the plasma membrane, the resulting complexes are commonly internalized via receptor-mediated endocytosis (RME; Receptor Mediated Endocytosis). It has a much lower profile in plant systems, where the occurrence of endocytotic processes of receptors has been discovered recently, and where plasma membrane receptor-ligand interactions are incompletely characterized. But, a strong evidence for a specific ligand-stimulated uptake of receptors, component of plant innate immune response, was recently described in Arabidopsis (reviewed in 2). Using FM4-64 and confocal lasr microscopy, we demonstrated that the specific cryptogein-binding to the PM increases the endocytosis rate in tobacco BY-2 cells. By transmission electronic microscopy we have scrutinized PM dynamics during elicitation, and showed that clathrin-coated pit gathering was under the influence of cryptogein. A pharmalogical interference approach, recently used in Arabidopsis (3) confirms that a part of cryptogein-induced endocytosis concerns the clathrin-dependent pathway involved in receptor-mediated endocytosis. Moreover, a BY-2 cell line expressing NtrbohD antisens cDNA, which is enable to produce ROS when submitted to cryptogein (1), does not present cryptogein-stimulated endocytosis. These results suggest that the transitory ROS production triggered by cryptogein elicitation plays a role in the clathrin-endocytosis stimulation. (1) Simon-Plant et al. (2002). Plant Journal 31 (2), 137-147. (2) Robatzek et al. (2007). Cllular Microbiology 9 (1), 1-8. (3) Dhonukshe et al. (2007). Current Biology 17, 520-527.