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GrainGenes Reference Report: PLA-212-16

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Reference	PLA-212-16
Title	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
Journal	Planta
Year	2000
Volume	212
Pages	16-24
Author	Huckelhoven R Fodor J Trujillo M Kogel KH
Abstract	Summary: The pathogenesis-related accumulation of superoxide radical anions 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-straining 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 superoxide radical anions 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
Keyword	[ Hide all but 1 of 49 ] active oxygen barley blumeria graminis blumeria graminis f.sp hordei cell cell death death detection disease disease resistance elements epidermal cells erysiphe fungal fungus gene gene product generation graminis h2o2 hordei hordeum hordeum vulgare hydrogen peroxide in situ invasion localization mesophyll mesophyll cells mildew mutant oxalate oxidase oxidase oxidative burst oxygen papilla formation powdery mildew powdery mildew fungus powdery mildew resistance products programmed cell death race-specific resistance resistance resistance gene salicylic-acid accumulation site superoxide wild wild-type

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