Molecular Plant Pathology - Pathogen Profiles
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Claviceps purpurea: molecular aspects of a unique pathogenic lifestyle
Paul Tudzynski and Jan Scheffer
Institut für Botanik, Westf. Wilhelms Universität Münster,
Schlossgarten 3. D 48149 Münster, Germany
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| Summary: |
Claviceps purpurea is a
ubiquitous pathogen of cereals and grasses, causing Ergot disease, which
results in substitution of grains by sclerotia. These overwintering
structures contain ergot-alkaloids, which can cause severe intoxication in
mammals. C. purpurea is an interesting model system for the
study of host-pathogen interaction. It displays strict organ specificity,
attacking exclusively young grass ovaries. It is optimally adapted to this
special niche of infection, probably by mimicry of pollen tubes: there are
no resistance genes known, and no effective resistance reactions can be
detected in the early steps of infection. In this early phase of host
tissue colonization the fungus shows directed, almost unbranched growth
towards the base of the ovary. Thus, C. purpurea represents
one of the few systems in which directed growth in filamentous fungi can
be studied. Finally, the fungus behaves as a true biotroph in planta,
although it can be easily grown in axenic culture. We describe here the
tools available to study this interesting pathogen, report on recent
molecular investigations concerning the role of cell-wall-degrading
enzymes and of reactive oxygen species in this specialized interaction,
and present an update of the signalling cascades involved in early events
of pathogenesis. |
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Pathogenic lifestyle of C. purpurea.
(A,B) Colonization of rye ovary. (A) Cross-section, 4 dpi, stained
with aniline blue; (B) schematic view, yellow and red arrows indicate
fungal infection route. (C-H) Selected stages of life cylce. (C)
Germinating sclerotium with stromata containing asci; (D) rye ovary; (E)
germinating conidiospore with subcuticular hyphal growth toward the
cellular junction; (F) sphacelium; (G) rye ear with honeydew; (H) mature
rye ear with sclerotia. Images E and F are courtesy of K.B. Tenberge.
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