Growing evidence suggests that plants have adapted endocytosis for signal transduction and use mechanisms similar to those of animals to regulate receptor internalization. Despite progress in the description of some endocytic routes of plant plasma membrane proteins, we are far from a complete understanding of the endocytic trafficking of receptor complexes and to which extent their signalling activity requires and is modulated by these routes. The project aims at filling this gap by gaining basic knowledge of the relationship between the endocytic transport and signalling activity of brassinosteroid hormones. In addition, the discovery of novel components of plant endocytic machinery will provide evolutionary insight into why certain gene families expanded in plants, while others range from being absent to having been maintained at an ancestral minimum.