Secreted proteins from Ralstonia solanacearum: a hundred tricks to kill a plant.

Sequence analysis of bacterial genomes has revealed a tremendous potential for protein secretion. This is certainly true for the plant pathogen Ralstonia solanacearum which is estimated to export hundreds of proteins through several specialized protein secretion systems. Central to pathogenicity are the Type II and Type III secretion systems both of which serve to export large repertoires of pathogenicity effectors. The distribution and the conservation of Type III effectors into bacterial populations are starting to be unravelled and provide insights into the evolution of virulence functions. Recent advances on the characterization of the GALA and PopP2 proteins illustrate how R. solanacearum Type III effectors subvert host cellular pathways, either by mimicking action of key host proteins or by inducing their subcellular relocalization.