Abstract
Superoxide dismutases (SODs) are key components of the plant antioxidant defense system. While plastidic and cytosolic isoforms have been extensively studied, the importance of mitochondrial SOD at a cellular and whole-plant level has not been established. To address this, transgenic Arabidopsis (Arabidopsis thaliana) plants were generated in which expression of AtMSD1, encoding the mitochondrial manganese (Mn)SOD, was suppressed by antisense. The strongest antisense line showed retarded root growth even under control growth conditions. There was evidence for a specific disturbance of mitochondrial redox homeostasis in seedlings grown in liquid culture: a mitochondrially targeted redox-sensitive green fluorescent protein was significantly more oxidized in the MnSOD-antisense background. In contrast, there was no substantial change in oxidation of cytosolically targeted redox-sensitive green fluorescent protein, nor changes in antioxidant defense components. The consequences of altered mitochondrial redox status of seedlings were subtle with no widespread increase of mitochondrial protein carbonyls or inhibition of mitochondrial respiratory complexes. However, there were specific inhibitions of tricarboxylic acid (TCA) cycle enzymes (aconitase and isocitrate dehydrogenase) and an inhibition of TCA cycle flux in isolated mitochondria. Nevertheless, total respiratory CO2 output of seedlings was not decreased, suggesting that the inhibited TCA cycle enzymes can be bypassed. In older, soil-grown plants, redox perturbation was more pronounced with changes in the amount and/or redox poise of ascorbate and glutathione. Overall, the results demonstrate that reduced MnSOD affects mitochondrial redox balance and plant growth. The data also highlight the flexibility of plant metabolism with TCA cycle inhibition having little effect on overall respiratory rates.
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Claims 10
Claim · model-written summary
The strongest MnSOD antisense line had retarded root growth under control conditions.
- Taxon
- Arabidopsis thaliana
Arabidopsis thalianae1 - Material
- strongest antisense linee0
- Treatment
- suppressed by antisensee1
- Gene
- AtMSD1e1
- Outcome
- root growthe0
- Direction
- retardede0
- Comparator
- control growth conditionse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The strongest antisense line showed retarded root growth even under control growth conditions.”
e1“transgenic Arabidopsis (Arabidopsis thaliana) plants were generated in which expression of AtMSD1, encoding the mitochondrial manganese (Mn)SOD, was suppressed by antisense”
Claim · model-written summary
Mitochondrial redox reporter oxidation was significantly higher in MnSOD antisense seedlings.
- Taxon
- Arabidopsis thalianaArabidopsis thalianae1
- Organ / stage
- seedlingse2
- Treatment
- MnSOD-antisense backgrounde0
- Outcome
- mitochondrially targeted redox-sensitive green fluorescent proteine0
- Direction
- more oxidizede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“a mitochondrially targeted redox-sensitive green fluorescent protein was significantly more oxidized in the MnSOD-antisense background.”
e1“transgenic Arabidopsis (Arabidopsis thaliana) plants were generated in which expression of AtMSD1, encoding the mitochondrial manganese (Mn)SOD, was suppressed by antisense”
e2“seedlings grown in liquid culture”
Claim · model-written summary
Cytosolic redox reporter oxidation showed no substantial change.
- Taxon
- Arabidopsis thalianaArabidopsis thalianae1
- Treatment
- suppressed by antisensee1
- Outcome
- oxidation of cytosolically targeted redox-sensitive green fluorescent proteine0
- Direction
- no substantial changee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“there was no substantial change in oxidation of cytosolically targeted redox-sensitive green fluorescent protein”
e1“transgenic Arabidopsis (Arabidopsis thaliana) plants were generated in which expression of AtMSD1, encoding the mitochondrial manganese (Mn)SOD, was suppressed by antisense”
Claim · model-written summary
Antioxidant defense components did not change.
- Taxon
- Arabidopsis thalianaArabidopsis thalianae1
- Treatment
- suppressed by antisensee1
- Outcome
- antioxidant defense componentse0
- Direction
- no_changeinferrede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“nor changes in antioxidant defense components”
e1“transgenic Arabidopsis (Arabidopsis thaliana) plants were generated in which expression of AtMSD1, encoding the mitochondrial manganese (Mn)SOD, was suppressed by antisense”
Claim · model-written summary
Mitochondrial protein carbonyls showed no widespread increase.
- Taxon
- Arabidopsis thalianaArabidopsis thalianae1
- Treatment
- suppressed by antisensee1
- Outcome
- mitochondrial protein carbonylse0
- Direction
- no widespread increasee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“no widespread increase of mitochondrial protein carbonyls”
e1“transgenic Arabidopsis (Arabidopsis thaliana) plants were generated in which expression of AtMSD1, encoding the mitochondrial manganese (Mn)SOD, was suppressed by antisense”
Claim · model-written summary
Mitochondrial respiratory complexes were not inhibited.
- Taxon
- Arabidopsis thalianaArabidopsis thalianae1
- Treatment
- suppressed by antisensee1
- Outcome
- mitochondrial respiratory complexese0
- Direction
- no_changeinferrede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“no widespread increase of mitochondrial protein carbonyls or inhibition of mitochondrial respiratory complexes”
e1“transgenic Arabidopsis (Arabidopsis thaliana) plants were generated in which expression of AtMSD1, encoding the mitochondrial manganese (Mn)SOD, was suppressed by antisense”
Claim · model-written summary
Aconitase and isocitrate dehydrogenase activities were inhibited.
- Taxon
- Arabidopsis thalianaArabidopsis thalianae1
- Treatment
- suppressed by antisensee1
- Gene
- aconitase and isocitrate dehydrogenasee0
- Outcome
- tricarboxylic acid (TCA) cycle enzymese0
- Direction
- inhibitionse0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“specific inhibitions of tricarboxylic acid (TCA) cycle enzymes (aconitase and isocitrate dehydrogenase)”
e1“transgenic Arabidopsis (Arabidopsis thaliana) plants were generated in which expression of AtMSD1, encoding the mitochondrial manganese (Mn)SOD, was suppressed by antisense”
Claim · model-written summary
TCA cycle flux in isolated mitochondria was inhibited.
- Taxon
- Arabidopsis thalianaArabidopsis thalianae1
- Treatment
- suppressed by antisensee1
- Outcome
- TCA cycle fluxe0
- Direction
- inhibitione0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“an inhibition of TCA cycle flux in isolated mitochondria”
e1“transgenic Arabidopsis (Arabidopsis thaliana) plants were generated in which expression of AtMSD1, encoding the mitochondrial manganese (Mn)SOD, was suppressed by antisense”
Claim · model-written summary
Total respiratory CO2 output of seedlings did not decrease.
- Taxon
- Arabidopsis thalianaArabidopsis thalianae1
- Organ / stage
- seedlingse0
- Treatment
- suppressed by antisensee1
- Outcome
- total respiratory CO2 outpute0
- Direction
- not decreasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“total respiratory CO2 output of seedlings was not decreased”
e1“transgenic Arabidopsis (Arabidopsis thaliana) plants were generated in which expression of AtMSD1, encoding the mitochondrial manganese (Mn)SOD, was suppressed by antisense”
Claim · model-written summary
Older soil grown plants showed more pronounced redox perturbation and changes in ascorbate and glutathione state.
- Taxon
- Arabidopsis thalianaArabidopsis thalianae1
- Organ / stage
- older, soil-grown plantse0
- Outcome
- redox perturbatione0
- Direction
- more pronouncede0
- Qualifier
- changes in the amount and/or redox poise of ascorbate and glutathionee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“In older, soil-grown plants, redox perturbation was more pronounced with changes in the amount and/or redox poise of ascorbate and glutathione.”
e1“transgenic Arabidopsis (Arabidopsis thaliana) plants were generated in which expression of AtMSD1, encoding the mitochondrial manganese (Mn)SOD, was suppressed by antisense”
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