Identification of plant Components involved in the perception by Arabidopsis of Ralstonia solanacEarum, a bacterial pathogen. – ICARE

A better understanding of the mechanisms involved in the initial steps of perception of a pathogen by an host plant constitutes the major goal of this project. Beyond the direct or indirect interaction between the plant resistance protein and the microbial avirulence protein, several studies indicate the existence of other plant components implied in the formation of a multiproteic perception complex. RRS1-R, an atypical R protein conferring resistance to several strains of the bacterial pathogen, Ralstonia solanacearum, as well as PopP2, the matching avirulence protein that presents similarities with members of a cystein protease family, constitute key tools for the development of this programme. These 2 proteins, isolated in our lab, interact and colocalise in the nuclei. The characterization of proteins interacting with RRS1-R and/or PopP2, their role in the elaboration of the plant responses as well as their potential modifications by PopP2 constitute the first aspect of this project. Yeast double and triple hybrid, reverse genetics and genetic approaches are (and will be) developed towards these goals. The characterization of the physiological effects of microbial effectors within plants constitute a major objective in phytopathology and is of crucial importance in the understanding of pathogenicity. The second aspect of this program concerns therefore the characterization of a protease activity of PopP2 in order to elucidate the mode of action of this effector targeted into the nucleus. The third part of the project will focus on alterations concerning plant genes whose expression is modulated by the Avr protein. Towards this goal, transgenic plants expressing PopP2, or a PopP2 variant mutated in its catalytic triad, both under the control of an inducible promoter, will be generated. A comparative transcriptomic analysis of the effects of PopP2 (or its variant) in plants expressing or not RRS1-R should provide important clues on the role of this protein, on the alterations it induces in host plants as well as on its potential targets.