RXLR effector PexRD54 links a plastid-localized protein to autophagy

NATTAPONG SANGUANKIATTICHAI; MARÍA EUGENIA SEGRETIN; TOLGA BOZKURT; SOPHIEN KAMOUN

Portland

Congreso; XVII International Congress on Molecular Plant-Microbe Interactions - IS-MPMI 2016; 2016

IS-MPMI International Society for Molecular Plant Microbe Interactions

Autophagy requires the formation of doublemembranevesicles named autophagosomes, which enclose the material tobe degraded or reallocated. In mammalian cells different compartments contribute to autophagosome formationincluding endoplasmic reticulum (ER), mitochondria and Golgi. However, the origin, biogenesis and transport ofautophagosomes in plants remain largely unknown. To better understand these aspects of autophagy, we exploitedPhytophthora infestans effector PexRD54 that perturbs autophagy. We showed that PexRD54 stimulates autophagosomeformation through binding the autophagy protein ATG8CL. Interestingly, live cell imaging analyses revealed that a subpopulationof PexRD54 labelled compartments associated to the plastids, indicating that plastids might contribute toPexRD54 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 PexRD54UBX1interaction and determined that PexRD54 promotes the interaction of UBX1 with ATG8CL. We show that PexRD54recruits UBX1to ATG8CL protein complexes possibly to stimulate autophagosome biogenesis at the ER and the plastidouter membrane. Consistently, knockdownof UBX1impaired PexRD54 triggered autophagosome formation. Finally,PexRD54 protein complexes were recruited to compartments implicated in autophagydependentrecycling of plastidproteins. Our work reveals that PexRD54 forms protein complexes with plastid localized proteins possibly to integrateplastidrecyclingpathways to autophagy.