Arbuscular mycorrhizal (AM) symbiosis has great potential in agriculture for the development of food and energy crops better equipped to cope with extreme environmental conditions and with less fertilizers requirement. PlantMYCcellWall intends, through an interdisciplinary research project using a combination of genetics, molecular, cell biology and biochemical approaches, a better understanding of the plant molecular basis regulating the AM symbiosis development. Despite significant advances in understanding the mechanism controlling the mycorrhizal symbiosis, we still do not really understand how plants influence the fungal growth through the plant cell wall, and how the AM fungus is able to cross the plant cell wall. Accordingly, the principles aims of PlantMYCcellWall, are to address a previously unexplored but timely area on plant cell wall modifications during AM symbiosis and on the plant genetic determinants and hormonal signaling that regulate the AM fungus growth through the plant cell wall. The recently described Brachypodium mycorrhizal plant interaction, presents an exclusively intracellular growth being crucial to aboard this research. In our endangered plant productivity environment, deciphering these mechanisms in Brachypodium plants will allow us to know if important European cereals crops as wheat and barley will benefit from the AM symbiosis in a more sustainable agriculture. Results obtained in PlantMYCcellWall will enhance the actual knowledge in AM symbiosis allowing a better use of soil resources with a better crop performance and will also provide valuable knowledge for the pathogenic community. By combining the different approaches proposed, PlantMYCcellWall will generate new knowledge that will open new avenues for the understanding of mechanisms controlling plants symbiosis and opening up new interesting fields of study of plant-microbe interactions.