Eukaryotic fatty acylation drives plasma membrane targeting and enhances function of several type III effector proteins from Pseudomonas syringae

Bacterial pathogens of plants and animals utilize conserved type III delive ry systems to traffic effector proteins into host cells. Plant innate immun e systems evolved disease resistance (R) genes to recognize some type III e ffecters, termed avirulence (Avr) proteins. On disease-susceptible (r) plan ts, Avr proteins can contribute to pathogen virulence. We demonstrate that several type III effecters from Pseudomonas syringae are targeted to the ho st plasma membrane and that efficient membrane association enhances functio n. Efficient localization of three Avr proteins requires consensus myristoy lation sites, and Avr proteins can be myristoylated inside the host cell. T hese prokaryotic type III effecters thus utilize a eukaryote-specific postt ranslational modification to access the subcellular compartment where they function.