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The Fungal Interactome Fungal interactions, specifically those that occur between fungal pathogens and plants Consider from three perspectives: What does it take to be a pathogen? How do pathogens differ from non pathogens? What does it take to be a pathogen of a particular host?
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The Fungal Interactome • Fungal interactions, specifically those that occur between fungal pathogens and plants • Consider from three perspectives: • What does it take to be a pathogen? • How do pathogens differ from non pathogens? • What does it take to be a pathogen of a particular host? • Fungal plant pathogenicity is rare. • Most are Ascomycetes • Phylogenetic relationships: plant vs animal pathogens. • Closely related species can differ in key lifestyle characteristics, e.g., pathogenicity. • Specific vs general pathogenicity determinants. • The fungal cell. • Eukaryotic organism • Single or multicellular • Genome size 35-40 Mb, 10-15000 genes • Complex growth and development • Fungal plant pathogen/plant interactions. • Signaling • Attachment • Germination • Appressorium development • Penetration • Colonization • Two models systems: • Magnaporthe grisea hemibiotroph • Cochliobolusheterostrophus necrotroph
Fungal Plant Pathogenesis Recognition Penetration Colonization
Magnaporthe grisea/oryzae Cochliobolus heterostrophus cereal pathogen rice, barley, and grasses corn pathogen necrotroph hemibiotroph no gene for gene? gene for gene 2 races many races
convergence of plant pathogens Cochliobolus on corn Magnaporthe on rice
Magnaporthe Appressoria Pigmented Non-pigmented (R. Howard)
Cochliobolus Appressoria Pigmented Non-pigmented
wild type Ga deletions; no appressoria H2O * Sandrock, Horwitz et al
Magnaporthe oryzae on rice Conidia are the primary means by which the fungus disperses in the field Can have many cycles of infection and sporulation from lesions in a single growing season Rice-infecting populations have a clonal structure
Appears to have invaded rice once (Couch et al. 2005) Multilocus study 497 isolates Independent methods of phylogenetic analysis *