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The hypersensitive reaction, membrane damage and accumulation of autofluorescent phenolics in lettuce cells challenged by Bremia lactucae
Author(s) -
Bennett Mark,
Gallagher Matthew,
Fagg Jean,
Bestwick Charles,
Paul Teresa,
Beale Michael,
Mansfield John
Publication year - 1996
Publication title -
the plant journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.058
H-Index - 269
eISSN - 1365-313X
pISSN - 0960-7412
DOI - 10.1046/j.1365-313x.1996.9060851.x
Subject(s) - vacuole , phytophthora infestans , plant cell , intracellular , chlorogenic acid , caffeic acid , hypha , microbiology and biotechnology , haustorium , biology , plasmopara viticola , membrane , chemistry , biophysics , biochemistry , botany , cytoplasm , fungicide , antioxidant , gene , ecology , host (biology)
Summary The expression of resistance to Bremia lactucae determined by the resistance genes Dm5/8 and Dm7 in lettuce was examined; incompatibility involved the hypersensitive reaction (HR) which occurred only within penetrated cells at early and late stages of fungal development, respectively. Autofluorescence observed under UV and blue light excitation in cells undergoing the HR was associated with the accumulation of ester‐linked syringaldehyde and caffeic acid on plant cell walls. Two phases of phenolic deposition were identified. The first was highly localized around penetration points and occurred during incompatible and compatible interactions. The second and major phase was only activated after the occurrence of irreversible membrane damage in the penetrated cell and was reduced by inhibitors of mRNA synthesis. Fungal structures, primary and secondary vesicles, intercellular hyphae and haustoria also became autofluorescent during incompatible interactions. Changes in the fluorescence due to preformed phenolics located in the plant cell vacuole were found just before plasma membrane damage became irreversible during the HR. In addition to localized deposition of phenolics, increases in the concentrations of the major free phenolic esters identified as dicaffeoyl tartaric and chlorogenic acids also occurred during incompatible interactions. The results suggest that membrane damage in penetrated cells occurs at different rates in resistance controlled by Dm5/8 and Dm7 and indicate an important role for irreversible membrane damage in lettuce as a key signalling event leading to widespread activation of defence responses in surrounding cells.