Structural basis of host ATG8 binding by the Irish potato famine pathogen effector protein PexRD54
A. MAQBOOL (1), R. Hughes (1), Y. Dagdas (2), E. Zess (1), N. Tregidgo (1), K. Belhaj (2), A. Round (3), T. Bozkurt (4), S. Kamoun (2), M. Banfield (1) (1) John Innes Centre, United Kingdom; (2) The Sainsbury Laboratory, United Kingdom; (3) EMBL, France; (4) Imperial College London, United Kingdom

Phytophthora infestans, the causative agent of late blight, is a devastating pathogen of potatoes and tomatoes. To colonise its hosts, P. infestans delivers an arsenal of effector proteins into plant cells to suppress immunity. We have recently reported that PexRD54, an RXLR-type effector protein, interacts with potato protein ATG8CL via its ATG8 interacting motif (AIM) to perturb host autophagy and defences. We also found that PexRD54 binds ATG8CL with sub-micromolar affinity in vitro. Building on this study, we have been investigating the structural basis of the PexRD54/ATG8CL interaction. We determined the crystal structure of PexRD54, which comprises a modular architecture including five tandem repeat “WY” domains, with the AIM sequence presented at the disordered C-terminus. To determine the molecular interface between PexRD54 and ATG8, we derived the crystal structure of potato ATG8CL in complex with a peptide comprising the effector’s AIM sequence, and established a model of full-length PexRD54/ATG8CL interaction using small angle X-ray scattering. In addition, we described the role of individual residues in the AIM region of PexRD54 for ATG8CL binding. Finally, structure-informed deletion of tandem PexRD54 WY domains reveals retention of ATG8CL binding in vitro and in plant cells, suggesting additional roles for the tandem domains. This study offers new insights into how RXLR effector proteins engage with host cell targets to promote disease. 

Abstract Number: P9-288
Session Type: Poster