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Suppression of the oxidative burst is crucial for successfull infection of the necrotroph Botrytis cinerea.
Herausgeber: Free Radical Research
Urheber: 5th Congress of Oxygen, Free Radicals and Oxidative Stress in Plants
Bandangabe: Abstract Book
Ort: Nizza, Frankreich
Jahr: 2001
Einordung:
Institut: Professur Phytomedizin
Abstract:
SUPPRESSION OF THE OXIDATIVE BURST IS CRUCIAL FOR SUCCESSFULL INFECTION OF THE NECROTROPH BOTRYTIS CINEREA.
Christoph Unger, Sylvia Kleta, and Andreas von Tiedemann
Dept. of Phytomedicine, Faculty of Agriculture, University of Rostock, Satower Strasse 48, 18051 Rostock, Germany
The oxidative burst is initiated by a fast and strong increase of superoxide radicals. Superoxide radicals are thought to trigger the hypersensitive response as prerequisite of plant defense. So far, these mechanisms are described for an interaction of plants with avirulent phytopathogenic bacteria and biotrophic fungi. Virulent phytopathogens have to suppress the plant oxidative burst as prerequisite for a successful infection.
On bean leaf discs with intact surface inoculation with different isolates of the necrotroph B. cinerea leads to 5 different symptoms, indicating different pathotypes. Two pathotypes (type IV and type V) are aggressive indicated by growing lesions, whereas type I, II & III isolates initiate dark brown spots, which are restricted in growth, indicating a hypersensitive-like response.
In bean suspension cells generation of superoxide was found to be only slightly increased or below the control level after inoculation with aggressive isolates (type IV & V). Inoculation with the non-aggressive types I, II, and III however, initiates a 62-fold, 325-fold, and 200-fold increase of superoxide radicals 32 hpi, respectively. In type V isolates the burst suppression was associated with a decrease in peroxidase activity. The strong HR inducing type II isolate initiates a remarkably earlier production of H2O2 during infection than all other isolates.
On non-inoculated bean leaf discs small amounts of superoxide radicals were produced and visualized by NBT-staining. After inoculation with type IV and V isolates the production of superoxide was suppressed in a 2 - 3 mm zone around the growing lesions. A transfer of intercellular fluid from this zone also led to an inhibition of the superoxide production without killing the tissue. The same phenomenon was observed after transfer of suspension cell culture filtrate inoculated with type IV and V isolates about 30 hpi.
First steps to characterize the suppressor showed that the compound is of low molecular wait, heat stabile, and insoluble in organic solvents. Further, no oxalic acid was found in the active fraction.
Our data strongly indicate that secretion of an oxidative burst suppressor is essential for a successful infection of B. cinerea.
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Letzte Änderung des Eintrages:
13.02.2007
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