RXLR effector PexRD54 couples host cellular transport components to autophagic compartments to stimulate autophagosome biogenesis and haustorial transport
T. BOZKURT (1), P. Pandey (1), Y. Dagdas (2), B. Dagvadorj (3), A. Toufexi (3), C. Duggan (3), M. Segretiin (4), S. Kamoun (2) (1) Imperial College london, Department of Life Sciences, London, UK., United Kingdom; (2) The Sainsbury Laboratory, Norwich Research Park, Norwich, NR4 7UH, UK., United Kingdom; (3) Imperial College london, Department of Life Sciences, London, UK., United Kingdom; (4) INGEBI-CONICET, Obligado 2490, C.A.B.A., C1428ADN, Argentina, United Kingdom

A selective form of autophagy organized by autophagy cargo receptors contributes to immunity in plants and animals. However, we know little about how it is regulated and contributes to immunity at the molecular level. We discovered that Phytophthora infestans effector PexRD54 stimulates autophagosome formation and subverts host defenses mediated by plant autophagy cargo receptor Joka2 by outcompeting it for binding the host autophagy regulator ATG8CL. Here we investigated the mechanisms underlying PexRD54 triggered autophagosome biogenesis, cargo sorting and transport. We discovered that PexRD54 stimulates autophagosome formation by coupling host vesicle transport regulators to ATG8CL-coated autophagosomes. PexRD54 interacted with the GDP bound form of the host Rab GTPase Rab8 through its N terminal WY motifs, whereas it bound ATG8CL via a short C terminal motif. However, ATG8CL colocalized and interacted with Rab8 in the presence of PexRD54. Conversely, Rab8 did not associate with Joka2 indicating that the content of autophagic cargo recruited by PexRD54 and Joka2 are different. Furthermore, genetic interference of Rab8 activity or impairment of its interaction with PexRD54 lead to reduced autophagosome formation. Finally, PexRD54-labeled autophagosomes are diverted towards haustoria, possibly to allocate cellular resources. Our results implicate effector-mediated employment of a Rab GTPase in autophagosome biogenesis and show that effectors can serve as adaptors targeting protein complexes to co-opt host processes.

Abstract Number: C17-5, P9-332
Session Type: Concurrent