I e

el rd a 5, Fr urie, Received 16 September 2011 relies on a type III secretion system (T3SS) to induce disease on host plants. DspA/E belongs to the AvrE family of type III effector. Effectors of the AvrE family are injected via the T3SS in plant cell and are important to promote bacterial growth following infection and to sup-press plant defense responses. Their mode of action in the plant cells is unknown. Here we study the family of T3Es and functional cross-complementation has been demonstrated between DspA/E of E. amylovora and AvrE of Pseudo-monas syringae [6]. T3Es of the AvrE family are widespread in plant-pathogenic bacteria. They are found in the genera Pseudomo-which strengthens the plant cell wall, and also interfere with other plant defense reactions [14–16]. Furthermore, their ectopic expres-sion in plant and yeast cells is toxic [15,17,18]. This indicates that they likely target a cellular process that is conserved between yeast and plant. Probably due to this toxicity, attempts to localize these effectors once ectopically expressed in plant cells have been unsuc-cessful [15,19]. Furthermore, yeast toxicity has precluded the use of the yeast two-hybrid technology to identify eukaryotic interac-tors of the full length proteins. Finally, effectors of the AvrE family are very large proteins which lack overall sequence homology wit