title: Relocalization of late blight resistance protein R3a to endosomal compartments is associated with effector recognition and required for the immune response.
abstract: An important objective of plant-pathogen interactions research is to determine where resistance proteins detect pathogen effectors to mount an immune response. Many nucleotide binding-Leucine-rich repeat (NB-LRR) resistance proteins accumulate in the plant nucleus following effector recognition, where they initiate the hypersensitive response (HR). Here, we show that potato (Solanum tuberosum) resistance protein R3a relocates from the cytoplasm to endosomal compartments only when coexpressed with recognized Phytophthora infestans effector form AVR3a(KI) and not unrecognized form AVR3a(EM). Moreover, AVR3a(KI), but not AVR3a(EM), is also relocalized to endosomes in the presence of R3a. Both R3a and AVR3a(KI) colocalized in close physical proximity at endosomes in planta. Treatment with brefeldin A (BFA) or wortmannin, inhibitors of the endocytic cycle, attenuated both the relocalization of R3a to endosomes and the R3a-mediated HR. No such effect of these inhibitors was observed on HRs triggered by the gene-for-gene pairs Rx1/PVX-CP and Sto1/IpiO1. An R3a(D501V) autoactive MHD mutant, which triggered HR in the absence of AVR3a(KI), failed to localize to endosomes. Moreover, BFA and wortmannin did not alter cell death triggered by this mutant. We conclude that effector recognition and consequent HR signaling by NB-LRR resistance protein R3a require its relocalization to vesicles in the endocytic pathway.
authors.affiliation: Division of Plant Sciences, University of Dundee, Dundee DD2 5DA, United Kingdom.
authors.forename: Stefan
authors.initials: S
authors.lastname: Engelhardt
authors.forename: Petra C
authors.initials: PC
authors.lastname: Boevink
authors.forename: Miles R
authors.initials: MR
authors.lastname: Armstrong
authors.forename: Maria Brisa
authors.initials: MB
authors.lastname: Ramos
authors.forename: Ingo
authors.initials: I
authors.lastname: Hein
authors.forename: Paul R J
authors.initials: PR
authors.lastname: Birch
mesh_terms: D000730:Androstadienes / Q000494:pharmacology; D020126:Brefeldin A / Q000494:pharmacology; D011992:Endosomes / Q000187:drug effects / Q000378:metabolism*; D055750:Phytophthora infestans / Q000472:pathogenicity; D057865:Plant Immunity / Q000187:drug effects / Q000502:physiology; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics; D011198:Solanum tuberosum / Q000276:immunology* / Q000378:metabolism*; D000077191:Wortmannin
chemical_list: D000730:Androstadienes; D010940:Plant Proteins; D020126:Brefeldin A; D000077191:Wortmannin