"Plant roots interact with a huge diversity of soil residing microbes that improve or hamper plant development. In a changing agriculture, where chemical inputs have to be reduced to protect the environment, the use of beneficial microbes residing in soil to improve plant nutrition and to prevent diseases is a promising alternative. However, symbiotic and pathogenic microbes follow similar steps to colonize their hosts and little is known about the extent of commonalities in plant responses guiding outcome of these associations. A cornerstone in regulation of these processes is the perception of microbial derived signals. Several genes required for sensing of mycorrhizal symbionts and subsequent colonization have been shown to affect interaction with root pathogens. We recently demonstrated in Dr. Schornack’s lab that a mutant of SymRK receptor which is unable to develop mycorrhization show extensive colonization by the root pathogenic oomycete Phytophthora palmivora. As this gene is the most upstream element in the signalling cascade required for mycorrhiza, we can now hypothesize an unsuspected convergence of early signalling events relayed and integrated by this protein to promote microbial accommodation or rejection. I will decipher how SymRK exerts roles in both interactions using a combination of approaches consisting of phenotyping of SymRK knock-out and overexpressing plants challenged with P. palmivora, mycorrhizal fungi and their isolated molecular signatures. The SymRK dependent transcriptomes in response to symbiotic or pathogenic signals and to the invasion will be elucidated to get clues about the gene network downstream of SymRK controlling synergistically or antagonistically these interactions. Finally I will take advantage of my environment in the Sainsbury Laboratory of Cambridge University to perform cutting edge microscopy on the cellular dynamics of receptors required for symbiosis including SymRK."