Tomato is one of the most important vegetables grown today and its production is threatened by increasing drought stress in many parts of the world. The application of biological such as Arbuscular Mycorrhizal fungi (AMF) has been proposed as a solution because the fungus can provide nutrients and water to the plant in a sustainable way and protect the plant against biotic and abiotic stresses. From the plant pathology field, we know that the pathogen can enter the plant by the secretion of small effector proteins, the genes of which also exist in AMF. However, little is known about their role during the establishment of the mutualistic interaction. In our research proposal, we will use state-of-the-art riboproteogenomics and the innovative proteomics technique BioID to get insight into the effectorome of Rhizophagus irregularis and the tomato root proteome by which it interacts. We will further study the role of three main tomato root proteins in reprogramming plant growth using a multidisciplinary approach combining phenotyping with molecular, physiological and biochemical assays. Our findings will benefit the current international interest in AM fungal effector biology as well as the tomato agriculture by providing novel insights in tomato AMF mutualism.