Abstract
To evaluate the physiological importance of thylakoid membrane-bound ascorbate peroxidase (tAPX) in the active oxygen species-scavenging system of chloroplasts, the level of tAPX in tobacco plants was altered by expression of the tAPX cDNA in both sense and antisense orientation. The tobacco plants transformed with constructs of antisense tAPXs from spinach and tobacco could not be obtained, suggesting that the suppression of tAPX in higher plants had a severe effect on the growth even under normal conditions. In contrast, the transgenic tobacco plants (TpTAP-12) overexpressing tAPX, which had approximately 37-fold higher activity than that of the wild-type plants, were generated. The TpTAP-12 plants showed increased tolerance to oxidative stress caused by application of methylviologen (MV, 50 microm) under light intensity (300 and 1600 microE m(-2) sec(-1)) and by chilling stress with high light intensity (4 degrees C, 1000 microE m(-2) sec(-1)). At 24 h after the MV treatment under illumination at 300 microE m-2 sec-1, destruction of chlorophyll was observed in the wild-type plants, but not in the TpTAP-12 plants. The activities of thiol-modulated enzymes in the Calvin cycle, the level and redox status of ascorbate (AsA), and the activity of tAPX in the wild-type plants significantly decreased, while those in the TpTAP-12 plants were hardly changed. These observations suggest that tAPX is a limiting factor of antioxidative systems under photo-oxidative stress in chloroplasts, and that the enhanced activity of tAPX functions to maintain the AsA content and the redox status of AsA under stress conditions.
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Claims 10
Claim · model-written summary
Suppression of tAPX by antisense constructs appeared to severely affect tobacco growth, as antisense plants could not be obtained.
- Taxon
- tobacco
Nicotiana tabacume1 - Treatment
- antisense tAPXse1
- Gene
- tAPXe1
- Outcome
- growthe1
- Direction
- decreaseinferrede1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“The tobacco plants transformed with constructs of antisense tAPXs from spinach and tobacco could not be obtained, suggesting that the suppression of tAPX in higher plants had a severe effect on the growth even under normal conditions”
Claim · model-written summary
TpTAP-12 plants showed increased tolerance to methylviologen-induced oxidative stress under light.
- Taxon
- tobaccoNicotiana tabacume0
- Material
- TpTAP-12e2
- Treatment
- methylviologen (MV, 50 microm)e2
- Gene
- tAPXe0
- Outcome
- tolerance to oxidative stresse2
- Direction
- increasede2
- Qualifier
- under light intensity (300 and 1600 microE m(-2) sec(-1))e2
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the level of tAPX in tobacco plants was altered by expression of the tAPX cDNA in both sense and antisense orientation”
e2“The TpTAP-12 plants showed increased tolerance to oxidative stress caused by application of methylviologen (MV, 50 microm) under light intensity (300 and 1600 microE m(-2) sec(-1)) and by chilling stress with high light intensity (4 degrees C, 1000 microE m(-2) sec(-1))”
Claim · model-written summary
TpTAP-12 plants showed increased tolerance to chilling stress with high light.
- Taxon
- tobaccoNicotiana tabacume0
- Material
- TpTAP-12e2
- Treatment
- chilling stress with high light intensity (4 degrees C, 1000 microE m(-2) sec(-1))e2
- Gene
- tAPXe0
- Outcome
- tolerance to oxidative stresse2
- Direction
- increasede2
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the level of tAPX in tobacco plants was altered by expression of the tAPX cDNA in both sense and antisense orientation”
e2“The TpTAP-12 plants showed increased tolerance to oxidative stress caused by application of methylviologen (MV, 50 microm) under light intensity (300 and 1600 microE m(-2) sec(-1)) and by chilling stress with high light intensity (4 degrees C, 1000 microE m(-2) sec(-1))”
Claim · model-written summary
After methylviologen treatment, chlorophyll was destroyed in wild-type plants but not in TpTAP-12 plants.
- Taxon
- tobaccoNicotiana tabacume0
- Material
- TpTAP-12e3
- Treatment
- MV treatmente3
- Outcome
- destruction of chlorophylle3
- Comparator
- wild-type plantse3
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the level of tAPX in tobacco plants was altered by expression of the tAPX cDNA in both sense and antisense orientation”
e3“At 24 h after the MV treatment under illumination at 300 microE m-2 sec-1, destruction of chlorophyll was observed in the wild-type plants, but not in the TpTAP-12 plants”
Claim · model-written summary
Activities of thiol-modulated Calvin cycle enzymes decreased significantly in wild-type plants under MV stress but hardly changed in TpTAP-12 plants.
- Taxon
- tobaccoNicotiana tabacume0
- Material
- wild-typee4
- Treatment
- MV treatmente3
- Outcome
- activities of thiol-modulated enzymes in the Calvin cyclee4
- Direction
- decreasede4
- Comparator
- TpTAP-12 plantse4
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the level of tAPX in tobacco plants was altered by expression of the tAPX cDNA in both sense and antisense orientation”
e3“At 24 h after the MV treatment under illumination at 300 microE m-2 sec-1, destruction of chlorophyll was observed in the wild-type plants, but not in the TpTAP-12 plants”
e4“The activities of thiol-modulated enzymes in the Calvin cycle, the level and redox status of ascorbate (AsA), and the activity of tAPX in the wild-type plants significantly decreased, while those in the TpTAP-12 plants were hardly changed”
Claim · model-written summary
The level and redox status of ascorbate decreased significantly in wild-type plants under MV stress, but hardly changed in TpTAP-12 plants.
- Taxon
- tobaccoNicotiana tabacume0
- Material
- wild-typee4
- Treatment
- MV treatmente3
- Outcome
- level and redox status of ascorbate (AsA)e4
- Direction
- decreasede4
- Comparator
- TpTAP-12 plantse4
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the level of tAPX in tobacco plants was altered by expression of the tAPX cDNA in both sense and antisense orientation”
e3“At 24 h after the MV treatment under illumination at 300 microE m-2 sec-1, destruction of chlorophyll was observed in the wild-type plants, but not in the TpTAP-12 plants”
e4“The activities of thiol-modulated enzymes in the Calvin cycle, the level and redox status of ascorbate (AsA), and the activity of tAPX in the wild-type plants significantly decreased, while those in the TpTAP-12 plants were hardly changed”
Claim · model-written summary
tAPX activity decreased significantly in wild-type plants under MV stress, but hardly changed in TpTAP-12 plants.
- Taxon
- tobaccoNicotiana tabacume0
- Material
- wild-typee4
- Treatment
- MV treatmente3
- Gene
- tAPXe4
- Outcome
- activity of tAPXe4
- Direction
- decreasede4
- Comparator
- TpTAP-12 plantse4
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the level of tAPX in tobacco plants was altered by expression of the tAPX cDNA in both sense and antisense orientation”
e3“At 24 h after the MV treatment under illumination at 300 microE m-2 sec-1, destruction of chlorophyll was observed in the wild-type plants, but not in the TpTAP-12 plants”
e4“The activities of thiol-modulated enzymes in the Calvin cycle, the level and redox status of ascorbate (AsA), and the activity of tAPX in the wild-type plants significantly decreased, while those in the TpTAP-12 plants were hardly changed”
Claim · model-written summary
Transgenic TpTAP-12 plants had approximately 37-fold higher tAPX activity than wild-type plants.
- Taxon
- tobaccoNicotiana tabacume5
- Material
- TpTAP-12e5
- Treatment
- overexpressing tAPXe5
- Gene
- tAPXe5
- Outcome
- activitye5
- Direction
- highere5
- Value
- approximately 37-folde5
- Comparator
- wild-type plantse5
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e5“the transgenic tobacco plants (TpTAP-12) overexpressing tAPX, which had approximately 37-fold higher activity than that of the wild-type plants”
Claim · model-written summary
tAPX is a limiting factor of antioxidative systems under photo-oxidative stress in chloroplasts.
- Taxon
- tobaccoNicotiana tabacume0
- Gene
- tAPXe6
- Outcome
- antioxidative systems under photo-oxidative stresse6
- Qualifier
- limiting factore6
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the level of tAPX in tobacco plants was altered by expression of the tAPX cDNA in both sense and antisense orientation”
e6“These observations suggest that tAPX is a limiting factor of antioxidative systems under photo-oxidative stress in chloroplasts”
Claim · model-written summary
Enhanced tAPX activity maintains the AsA content and redox status of AsA under stress.
- Taxon
- tobaccoNicotiana tabacume0
- Gene
- tAPXe7
- Outcome
- AsA content and the redox status of AsAe7
- Qualifier
- under stress conditionse7
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the level of tAPX in tobacco plants was altered by expression of the tAPX cDNA in both sense and antisense orientation”
e7“the enhanced activity of tAPX functions to maintain the AsA content and the redox status of AsA under stress conditions”
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