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Differential expression of a senescence-enhanced metallothionein gene inArabidopsisin response to isolates ofPeronospora parasiticaandPseudomonas syringae
Summary
The metallothionein gene,LSC54, shows increased expression during leaf senescence inBrassica napusandArabidopsis thaliana. A number of abiotic and biotic stresses have been shown to induce senescence-like symptoms in plants and, to investigate this further, the promoter of theLSC54gene was cloned and fused to the GUS gene and transformed intoArabidopsis. The promoter was highly induced during leaf senescence and also in response to wounding; histochemical analysis indicated that this induction was localised to a few cells close to the wound site. The transgenicArabidopsistissue was infected with compatible and incompatible isolates of both the fungal biotroph,Peronospora parasiticaand the bacterial necrotroph,Pseudomonas syringae.Incompatible isolates induced rapid cell death (the hypersensitive response) at the site of infection and, with both pathogens, early, localised expression of the GUS gene was observed. In contrast, relatively slow induction of the GUS gene was seen in the compatible interaction and this was correlated with the appearance of senescence-like symptoms in the biotrophic interaction and cell death by necrosis that occurred in response to the necrotrophic pathogen. These results suggest that there are common steps in the signalling pathways that lead to cell death in the hypersensitive response, pathogen induced necrosis and senescence.
The metallothionein gene,LSC54, shows increased expression during leaf senescence inBrassica napusandArabidopsis thaliana. A number of abiotic and biotic stresses have been shown to induce senescence-like symptoms in plants and, to investigate this further, the promoter of theLSC54gene was cloned and fused to the GUS gene and transformed intoArabidopsis. The promoter was highly induced during leaf senescence and also in response to wounding; histochemical analysis indicated that this induction was localised to a few cells close to the wound site. The transgenicArabidopsistissue was infected with compatible and incompatible isolates of both the fungal biotroph,Peronospora parasiticaand the bacterial necrotroph,Pseudomonas syringae.Incompatible isolates induced rapid cell death (the hypersensitive response) at the site of infection and, with both pathogens, early, localised expression of the GUS gene was observed. In contrast, relatively slow induction of the GUS gene was seen in the compatible interaction and this was correlated with the appearance of senescence-like symptoms in the biotrophic interaction and cell death by necrosis that occurred in response to the necrotrophic pathogen. These results suggest that there are common steps in the signalling pathways that lead to cell death in the hypersensitive response, pathogen induced necrosis and senescence.
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Document Type: Original Article
Affiliations: 1: Plant Molecular Biology Laboratory, Wye College, University of London, Wye TN25 5AH, UK, 2: Horticulture Research International, Wellesbourne 3: University of Chicago, MGCB Department of
Publication date: October 1, 1998
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