The RxLR Motif of the Host Targeting Effector AVR3a of Phytophthora infestans Is Cleaved Before Secretion

Stephan Wawra, Franziska Trusch, Anja Matena, Kostis Apostolakis, Uwe Linne, Igor Zhukov, Jan Stanek, Wiktor Koźmiński , Ian Davidson, Chris J Secombes, Peter Bayer, Pieter Van West* (Corresponding Author)

*Corresponding author for this work

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Abstract

When plant-pathogenic oomycetes infect their hosts they employ a large arsenal of effector proteins to establish a successful infection. Some effector proteins are secreted and are destined to be translocated and function inside host cells. The largest group of translocated proteins from oomycetes are the RxLR effectors, defined by their conserved N-terminal Arg-Xaa-Leu-Arg (RxLR) motif. However, the precise role of this motif in the host cell translocation process is unclear. Here detailed biochemical studies of the RxLR effector AVR3a from the potato pathogen Phytophthora infestans are presented. Mass spectrometric analysis revealed that the RxLR sequence of native AVR3a is cleaved off prior to secretion by the pathogen and the N-terminus of the mature effector was found likely to be acetylated. High-resolution NMR structure analysis of AVR3a indicates that the RxLR motif is well accessible for potential processing enzymes. Processing and modification of AVR3a is to some extend similar to events occurring with the export element (PEXEL) found in malaria effector proteins from Plasmodium falciparum. These findings imply a role for the RxLR motif in the secretion of AVR3a by the pathogen, rather than a direct role in the host cell entry process itself.
Original languageEnglish
Pages (from-to)1184-1195
Number of pages12
JournalThe Plant Cell
Volume29
Issue number6
Early online date18 May 2017
DOIs
Publication statusPublished - 1 Jun 2017

Bibliographical note

Our work is supported by the BBSRC (SW, CJS, PvW), NERC (PvW) and the University of Aberdeen (CJS, PvW, ID). This work was supported by EU East-NMR FP7 Project (Contract 228461) and Polish National Centre for Research and Development under research grant number 178479 (contract number PBS1/A9/ 13/2012) (for IZ). We would like to acknowledge Kevin MacKenzie of the core microscopy facility of the University of Aberdeen for helpful suggestions and Prof. Regine Kahmann for critical reading of the manuscript.

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