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Laboratory of Plant-Microbe Interactions - LIPM

Laboratory of Plant-Microbe Interactions

Ralstonia pathogenesis and adaptation to the plant environment

Our research aims at understanding the molecular mechanisms enabling the root pathogen Ralstonia solanacearum to promote disease on a wide array of host plants. R. solanacearum is probably one of the most destructive plant pathogenic bacterium worldwide, infecting more than 200 plant species in over 50 families, including major crops such as tomato, potato but also peanut and banana. Owing to the fact that several model plants are also hosts (Arabidopsis, Tomato, Medicago) the mechanisms involved in this plant-pathogen interaction are getting better understood.

We developed genetic and genomic approaches on the model R. solanacearum strain GMI1000 to identify essential pathogenicity determinants such as the Type 3 protein secretion system. This secretion system, present in many pathogenic bacteria, is a sophisticated tool allowing the pathogen to manipulate eukaryotic host cells with the direct transport of bacterial virulence proteins (effectors) into the host cells. We have identified more than seventy effectors in R. solanacearum. The molecular activities of most of these effectors are still unknown and represent an exciting prospect for our team in order to better understand the underlying mechanisms of this disease. For this, we are looking for plant targets of these effectors, direct or indirect targets related to resistance or susceptibility in Arabidopsis and Tomato plants.

We are also interested in the mechanisms of adaptation of the bacterium to its environment, and in particular its exceptional ability to colonize a wide range of hosts. We have developed an experimental evolution approach in which, by serial inoculations on a given plant species, variants with fitness gains have been identified. The characterization of genetic or epigenetic alterations of these variants has already shown the key role of a virulence regulatory network in these adaptation processes. This work has recently been supplemented by a system’s biology approach aimed at reconstructing both the metabolic and virulence regulatory networks in order to study more finely the close interconnection between metabolism and virulence and to initiate a modeling of the infectious dynamics of the pathogen.