Since 1985 when I started my PhD in Mike Daniel’s group at the John Innes Institute (UK), I have been studying how plants and bacteria interact together. Firstly, I worked in plant pathology with two phytopathogenic bacteria, Xanthomonas campestris and Ralstonia solanacearum, and their host plants. I studied the molecular mechanisms both by which these bacteria infect and cause disease symptoms on plants, and those that enable plants to resist such infection. During my analysis of the hrp genes of R. solanacearum as a post-doc in Christian Boucher’s group at the LIPM, I contributed to the discovery that the type III secretion system is conserved with bacterial mammalian pathogens, and is involved in secreting elicitors for disease and the hypersensitive reaction in plants. I was recruited by the CNRS in 1998 in Jean Dénarié’s group at the LIPM. Since then I have been studying the molecular and genetic mechanisms of early symbiotic signalling between Medicago truncatula and the two endosymbiotic microorganisms of this plant, Sinorhizobium meliloti and arbuscular mycorrhizal fungi. I was involved in the identification of a Nod factor signalling pathway in M. truncatula, and the demonstration that this is common between the two symbioses. I am particularly interested in the roles of LysM receptor proteins in plant-microbe interactions, as well as the interconnections between biotic and abiotic signalling mechanisms, including the role of redox signalling.