title: Plant phenolic acids induce programmed cell death of a fungal pathogen: MAPK signaling and survival of Cochliobolus heterostrophus.
abstract: Plant aromatic compounds provide signals and a nutrient source to pathogens, and also act as stressors. Structure-activity relationships suggest two pathways sensing these compounds in the maize pathogen Cochliobolus heterostrophus, one triggering a stress response, and one inducing enzymes for their degradation. Focusing on the stress pathway, we found that ferulic acid causes rapid appearance of TUNEL-positive nuclei, dispersion of histone H1:GFP, hyphal shrinkage, and eventually membrane damage. These hallmarks of programmed cell death (PCD) were not seen upon exposure to caffeic acid, a very similar compound. Exposure to ferulic acid dephosphorylated two MAP kinases: Hog1 (stress activated) and Chk1 (pathogenicity related), while increasing phosphorylation of Mps1 (cell integrity related). Mutants lacking Hog1 or Chk1 are hypersensitive to ferulic acid while Mps1 mutants are not. These results implicate three MAPK pathways in the stress response. Ferulic acid and the antifungal fludioxonil have opposite additive effects on survival and on dephosphorylation of Hog1, which is thus implicated in survival. The results may explain why some fungal pathogens of plants undergo cell death early in host invasion, when phenolics are released from plant tissue.
authors.affiliation: Faculty of Biology, Technion - Israel Institute of Technology, Haifa, 3200000, Israel.
authors.forename: Samer
authors.initials: S
authors.lastname: Shalaby
authors.affiliation: Faculty of Biology, Technion - Israel Institute of Technology, Haifa, 3200000, Israel.
authors.forename: Olga
authors.initials: O
authors.lastname: Larkov
authors.affiliation: Faculty of Biology, Technion - Israel Institute of Technology, Haifa, 3200000, Israel.
authors.forename: Netta-Li
authors.initials: NL
authors.lastname: Lamdan
authors.affiliation: Faculty of Biology, Technion - Israel Institute of Technology, Haifa, 3200000, Israel.
authors.forename: Orit
authors.initials: O
authors.lastname: Goldshmidt-Tran
authors.affiliation: Faculty of Biology, Technion - Israel Institute of Technology, Haifa, 3200000, Israel.
authors.forename: Benjamin A
authors.initials: BA
authors.lastname: Horwitz
mesh_terms: D017209:Apoptosis; D001203:Ascomycota / Q000166:cytology* / Q000235:genetics / Q000378:metabolism; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism*; D015966:Gene Expression Regulation, Fungal; D054884:Host-Pathogen Interactions; D062385:Hydroxybenzoates / Q000378:metabolism*; D020928:Mitogen-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D010935:Plant Diseases / Q000382:microbiology*; D015398:Signal Transduction; D003313:Zea mays / Q000378:metabolism* / Q000382:microbiology
chemical_list: D005656:Fungal Proteins; D062385:Hydroxybenzoates; D020928:Mitogen-Activated Protein Kinases; C017616:phenolic acid