Abstract
As a means to eliminate pathogen-infected cells and prevent diseases, programmed cell death (PCD) appears to be a defense strategy employed by most multicellular organisms. Recent studies have indicated that reactive oxygen species, such as O2.- and H2O2, play a central role in the activation and propagation of pathogen-induced PCD in plants. However, plants contain several mechanisms that detoxify O2.- and H2O2 and may inhibit PCD. We found that during viral-induced PCD in tobacco, the expression of cytosolic ascorbate peroxidase (cAPX), a key H2O2 detoxifying enzyme, is post-transcriptionally suppressed. Thus, although the steady state level of transcripts encoding cAPX was induced during PCD, as expected under conditions of elevated H2O2, the level of the cAPX protein declined. In vivo protein labeling, followed by immunoprecipitation, indicated that the synthesis of the cAPX protein was inhibited. Although transcripts encoding cAPX were found to associate with polysomes during PCD, no cAPX protein was detected after in vitro polysome run-off assays. Our findings suggest that viral-induced PCD in tobacco is accompanied by the suppression of cAPX expression, possibly at the level of translation elongation. This suppression is likely to contribute to a reduction in the capability of cells to scavenge H2O2, which in turn enables the accumulation of H2O2 and the acceleration of PCD.
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Claims 8
Claim · model-written summary
During viral induced PCD in tobacco, cAPX expression was suppressed after transcription.
- Taxon
- tobacco
Nicotiana tabacume0 - Gene
- cytosolic ascorbate peroxidase (cAPX)e0
- Outcome
- expression of cytosolic ascorbate peroxidase (cAPX)e0
- Direction
- suppressede0
- Qualifier
- viral-induced PCDe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“during viral-induced PCD in tobacco, the expression of cytosolic ascorbate peroxidase (cAPX), a key H2O2 detoxifying enzyme, is post-transcriptionally suppressed”
Claim · model-written summary
cAPX transcripts increased during PCD.
- Taxon
- TobaccoNicotiana tabacumt0
- Gene
- cAPXe0
- Outcome
- steady state level of transcripts encoding cAPXe0
- Direction
- inducede0
- Qualifier
- during PCDe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the steady state level of transcripts encoding cAPX was induced during PCD”
t0“Tobacco”
Claim · model-written summary
cAPX protein levels declined during PCD.
- Taxon
- TobaccoNicotiana tabacumt0
- Gene
- cAPXe0
- Outcome
- level of the cAPX proteine0
- Direction
- declinede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the level of the cAPX protein declined”
t0“Tobacco”
Claim · model-written summary
In vivo labeling and immunoprecipitation indicated inhibited cAPX protein synthesis.
- Taxon
- TobaccoNicotiana tabacumt0
- Gene
- cAPXe0
- Outcome
- synthesis of the cAPX proteine0
- Direction
- inhibitede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“In vivo protein labeling, followed by immunoprecipitation, indicated that the synthesis of the cAPX protein was inhibited”
t0“Tobacco”
Claim · model-written summary
cAPX transcripts remained associated with polysomes during PCD.
- Taxon
- TobaccoNicotiana tabacumt0
- Gene
- cAPXe0
- Outcome
- associate with polysomes during PCDe0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“transcripts encoding cAPX were found to associate with polysomes during PCD”
t0“Tobacco”
Claim · model-written summary
No cAPX protein was detected after in vitro polysome run off assays.
- Taxon
- TobaccoNicotiana tabacumt0
- Gene
- cAPXe0
- Outcome
- no cAPX protein was detectede0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“no cAPX protein was detected after in vitro polysome run-off assays”
t0“Tobacco”
Claim · model-written summary
The authors suggest cAPX suppression may occur at translation elongation.
- Taxon
- tobaccoNicotiana tabacume0
- Gene
- cAPXe0
- Outcome
- suppression of cAPX expressione0
- Direction
- suppressione0
- Qualifier
- possibly at the level of translation elongatione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“viral-induced PCD in tobacco is accompanied by the suppression of cAPX expression, possibly at the level of translation elongation”
Claim · model-written summary
The authors infer cAPX suppression reduces H2O2 scavenging and enables H2O2 accumulation and faster PCD.
- Taxon
- TobaccoNicotiana tabacumt0
- Compound
- H2O2e0
- Outcome
- acceleration of PCDe0
- Direction
- acceleratione0
- Qualifier
- reduction in the capability of cells to scavenge H2O2e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“This suppression is likely to contribute to a reduction in the capability of cells to scavenge H2O2, which in turn enables the accumulation of H2O2 and the acceleration of PCD”
t0“Tobacco”