Host-interactor screens of Phytophthora infestans RXLR proteins

Pathogens modulate host cell structure and function by secreting effectors into host tissues. Effectors generally function by associating with host molecules and co-opting or perturbing their activities. This study aimed at identifying the plant proteins associated with the RXLR class of host-translocated effectors of the potato blight pathogen Phytophthora infestans in order to identify the host processes targeted by these effectors. We carried out an in planta screen by transiently expressing P. infestans RXLR effectors in Nicotiana benthamiana leaves followed by co-immunoprecipitation (co-IP) and liquid chromatography tandem mass spectrometry (LC-MS/MS). This generated an effector-host protein interactome matrix of 59 P. infestans RXLR effectors x 586 N. benthamiana proteins. Classification of the host interactors into putative functional categories revealed over 35 biological processes that are candidate effector-targeted pathways. We further characterized the PexRD12/31 family of RXLR-WY effectors, which associate and co-localize with components of vesicle trafficking machinery. One member of this family, PexRD31, increased the number of GFP-2xFYVE labeled vesicles in N. benthamiana cells. We also noted an accumulation of FYVE vesicles in areas of N. benthamiana leaves colonized by P. infestans indicating that this pathogen may enhance endosomal trafficking. We hope that the interactome dataset we generated will serve as a useful community resource for functional studies of P. infestans effectors.