RXLR effector PexRD54 links a plastid-localized protein to autophagy    
M. SEGRETIN (1), Y. Dagdas (2), N. Sanguankiattichai (3), S. Kamoun (2) (1) INGEBI-CONICET, Argentina; (2) The Sainsbury Laboratory, United Kingdom; (3) Imperial College London, Department of Life Sciences, United Kingdom

Autophagy requires the formation of double-membrane vesicles named autophagosomes, which enclose the material to be degraded or reallocated. In mammalian cells different compartments contribute to autophagosome formation including endoplasmic reticulum (ER), mitochondria and Golgi. However, the origin, biogenesis and transport of autophagosomes in plants remain largely unknown. To better understand these aspects of autophagy, we exploited Phytophthora infestans effector PexRD54 that perturbs autophagy. We showed that PexRD54 stimulates autophagosome formation through binding the autophagy protein ATG8CL. Interestingly, live cell imaging analyses revealed that a sub-population of PexRD54 labelled compartments associated to the plastids, indicating that plastids might contribute to PexRD54 triggered autophagy. Among the candidate PexRD54 interactors we identified a UBX domain containing protein (UBX1) that localized to the chloroplast outer envelope, the ER, and vesicles of unknown nature. We validated PexRD54-UBX1 interaction and determined that PexRD54 promotes the interaction of UBX1 with ATG8CL. We show that PexRD54 recruits UBX-1 to ATG8CL protein complexes possibly to stimulate autophagosome biogenesis at the ER and the plastid outer membrane. Consistently, knock-down of UBX-1 impaired PexRD54 triggered autophagosome formation. Finally, PexRD54 protein complexes were recruited to compartments implicated in autophagy-dependent recycling of plastid proteins. Our work reveals that PexRD54 forms protein complexes with plastid localized proteins possibly to integrate plastid-recycling pathways to autophagy.

Abstract Number: P9-303
Session Type: Poster