Arbuscular mycorrhizal fungi (AMF) are mutualistic symbionts of a wide range of plants, including tomato. AMF supply their hosts with nutrients and receive sugars and lipids in return. They can offer a sustainable solution for nutrient deficiencies and drought in tomato cultivation during ongoing climate change. Plant-derived sugars are also essential for tomato fruit development and quality. Hence, a fine-tuned nutrient exchange at the sites of plant-AMF interactions, i.e. arbusculated root cells, is essential to obtain benefits for both AMF and tomato. This project aims to engineer the sugar flux specifically at these sites to optimize mycorrhization without affecting tomato fruit development and quality and to enhance AMF spore production. We will first select tomato sugar transporters and sensors specifically expressed in arbusculated root cells using LCM-qRT-PCR. To elucidate their role during mycorrhization, arbusculated cell-specific transgenic composite tomato plants will be generated for each of the candidates using state-of-the-art CRISPR-TSKO technology. Next, we will study the molecular mode-of-action of five candidates that affect mycorrhization using a multidisciplinary approach. In the last stage of the project, we will collaborate with INRAE-Bordeaux to unravel how an altered sugar flux in arbusculated cells regulates tomato growth and fruit development using stable transgenic tomato lines. This project will lead to more sustainable agricultural practices.