A powdery mildew core effector protein targets host endosome tethering complexes HOPS and CORVET

bioRxiv (Cold Spring Harbor Laboratory)

Abstract

Abstract Powdery mildew fungi are serious pathogens of many plant species. Their genomes encode extensive repertoires of secreted effector proteins that suppress host immunity. Here, we revised and analyzed the candidate secreted effector protein (CSEP) effectome of the barley powdery mildew fungus, Blumeria hordei ( Bh ) and identified seven CSEPs that are broadly conserved in powdery mildew fungal species, rendering them core effectors of these phytopathogens. We show that one of these, CSEP0214, interacts with the barley VPS18 protein, a core component of the CORVET and HOPS endosomal tethering complexes, mediating fusions of early endosomes and multivesicular bodies with the central vacuole, respectively. Overexpression of CSEP0214 and knockdown of either VPS18 , HOPS-specific VPS41 or CORVET-specific VPS8 caused a block of the vacuolar pathway and the accumulation of the fluorescent vacuolar marker protein (SP)-RFP-AFVY in the endoplasmic reticulum. Co-immunoprecipitation and yeast two-hybrid experiments suggest that CSEP0214 blocks the interaction of VPS18 and VPS16, which are both core components of CORVET as well as HOPS. Additionally, expression of CSEP0214 blocked the hypersensitive cell death response associated with resistance gene-mediated immunity in barley, indicating that endomembrane traffic is required for this process. It also prevented callose deposition in cell wall appositions at attack sites and encasements of fungal infection structures. Our results indicate that this powdery mildew core effector is an essential immunity suppressor. One sentence summary The Blumeria hordei effector protein CSEP0214 interacts with barley VPS18, a core component of the CORVET and HOPS endosomal tethering complexes, thereby interfering with host endomembrane trafficking.

Authors 5

1. Björn Sabelleck Aachen Institute for Biology I Unit of Plant Molecular Cell Biology

   University of Copenhagen · RWTH Aachen University

   Affiliation as printed

   Department of Plant and Environmental Sciences, Section for Plant and Soil Sciences, University of Copenhagen, Thorvaldsensvej 40, 1871 Frederiksberg C, Denmark

   Institute for Biology I, Unit of Plant Molecular Cell Biology, RWTH Aachen University, 52056, Aachen, Germany

2. Sohini Deb

   University of Copenhagen

   Affiliation as printed

   Department of Plant and Environmental Sciences, Section for Plant and Soil Sciences, University of Copenhagen, Thorvaldsensvej 40, 1871 Frederiksberg C, Denmark

3. Pietro D. Spanu

   Imperial College London

   Affiliation as printed

   Department of Life Sciences, Imperial College London, Imperial College Road, London, SW7 2AZ, UK

4. Hans Thordal‐Christensen corresponding

   University of Copenhagen

   Affiliation as printed

   Department of Plant and Environmental Sciences, Section for Plant and Soil Sciences, University of Copenhagen, Thorvaldsensvej 40, 1871 Frederiksberg C, Denmark

5. Ralph Panstruga corresponding Aachen Institute for Biology I Unit of Plant Molecular Cell Biology

   RWTH Aachen University

   Affiliation as printed

   Institute for Biology I, Unit of Plant Molecular Cell Biology, RWTH Aachen University, 52056, Aachen, Germany