title: Synergistic interactions of the plant cell death pathways induced by Phytophthora infestans Nepl-like protein PiNPP1.1 and INF1 elicitin.
abstract: Cell death plays a ubiquitous role in plant-microbe interactions, given that it is associated with both susceptible and resistance interactions. A class of cell death-inducing proteins, termed Nepl-like proteins (NLPs), has been reported in bacteria, fungi, and oomycetes. These proteins induce nonspecific necrosis in a variety of dicotyledonous plants. Here, we describe three members of the NLP family from the oomycete Phytophthora infestans (PiNPP1.1, PiNPP1.2, and PiNPP1.3). Using agroinfection with a binary Potato virus X vector, we showed that PiNPP1.1 induces cell death in Nicotiana benthamiana and the host plant tomato. Expression analyses indicated that PiNPP1.1 is up-regulated during late stages of infection of tomato by P. infestans. We compared PiNPP1.1 necrosis-inducing activity to INF1 elicitin, a well-studied protein that triggers the hypersensitive response in Nicotiana spp. Using virus-induced gene silencing, we showed that the cell death induced by PiNPP1.1 is dependent on the ubiquitin ligase-associated protein SGT1 and the heat-shock protein HSP90. In addition, cell death triggered by PiNPP1.1 but not that by INF1 was dependent on the defense-signaling proteins COI1, MEK2, NPR1, and TGA2.2, suggesting distinct signaling requirements. Combined expression of PiNPP1.1 and INF1 in N. benthamiana resulted in enhanced cell death, suggesting synergistic interplay between the two cell-death responses. Altogether, these results point to potentially distinct but interacting cell-death pathways induced by PiNPP1.1 and INF1 in plants.
authors.affiliation: Department of Plant Pathology, The Ohio State University, Ohio Agricultural Research and Development Center, 1680 Madison Ave., Wooster, OH 44691, USA.
authors.forename: Thirumala-Devi
authors.initials: TD
authors.lastname: Kanneganti
authors.forename: Edgar
authors.initials: E
authors.lastname: Huitema
authors.forename: Cahid
authors.initials: C
authors.lastname: Cakir
authors.forename: Sophien
authors.initials: S
authors.lastname: Kamoun
mesh_terms: D020418:Algal Proteins / Q000145:classification / Q000235:genetics / Q000502:physiology*; D005786:Gene Expression Regulation; D020868:Gene Silencing; D018841:HSP90 Heat-Shock Proteins / Q000235:genetics / Q000502:physiology; D018551:Solanum lycopersicum / Q000166:cytology / Q000469:parasitology* / Q000502:physiology; D008969:Molecular Sequence Data; D009336:Necrosis; D010838:Phytophthora / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D010935:Plant Diseases; D018515:Plant Leaves / Q000033:anatomy & histology / Q000502:physiology; D010940:Plant Proteins / Q000235:genetics / Q000502:physiology; D011506:Proteins; D014026:Nicotiana / Q000033:anatomy & histology / Q000469:parasitology* / Q000502:physiology
chemical_list: D020418:Algal Proteins; D018841:HSP90 Heat-Shock Proteins; D010940:Plant Proteins; D011506:Proteins; C085101:elicitin, Phytophthora