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Planta

, Volume 212, Issue 1, pp 16–24 | Cite as

Barley Mla and Rar mutants compromised in the hypersensitive cell death response against Blumeria graminis f.sp. hordei are modified in their ability to accumulate reactive oxygen intermediates at sites of fungal invasion

  • Ralph Hückelhoven
  • József Fodor
  • Marco Trujillo
  • Karl-Heinz Kogel

Abstract.

 The pathogenesis-related accumulation of superoxide radical anions (O·−2) and hydrogen peroxide (H2O2) was comparatively analyzed in a barley line (Hordeum vulgare L. cv Sultan-5) carrying the powdery mildew (Blumeria graminis f.sp. hordei, Speer, Bgh) resistance gene Mla12, and in susceptible mutants defective in Mla12 or in genes “required for Mla12-specified disease resistance” (Rar1 and Rar2). In-situ localization of reactive oxygen intermediates was performed both by microscopic detection of azide-insensitive nitroblue tetrazolium (NBT) reduction or diaminobenzidine (DAB) polymerization, and by an NBT-DAB double-staining procedure. The Mla12-mediated hypersensitive cell death occurred either in attacked epidermal cells or adjacent mesophyll cells of wild-type plants. Whole-cell H2O2 accumulation was detected in dying cells, while O·−2 emerged in adjacent cells. Importantly, all susceptible mutants lacked these reactions. An oxalate oxidase, which is known to generate H2O2 and has been implicated in barley resistance against the powdery mildew fungus, was not differentially expressed between the wild type and all mutants. The results demonstrate that the Rar1 and Rar2 gene products, which are control elements of R-gene-mediated programmed cell death, also control accumulation of reactive oxygen intermediates but not the pathogenesis-related expression of oxalate oxidase.

Key words: Erysiphe Hordeum (cell death) Oxidative burst Programmed cell death 

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Copyright information

© Springer-Verlag Berlin Heidelberg 2000

Authors and Affiliations

  • Ralph Hückelhoven
    • 1
  • József Fodor
    • 2
  • Marco Trujillo
    • 1
  • Karl-Heinz Kogel
    • 1
  1. 1.Institute for Phytopathology and Applied Zoology, Heinrich-Buff-Ring 26-32, Justus-Liebig-Universität Gießen, 35392 Gießen, GermanyDE
  2. 2.Plant Protection Institute, Hungarian Academy of Sciences, P.O. Box 102, 1525 Budapest, HungaryHU

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