Abstract
The increase in net photosynthesis in M(4) progeny of an O(2)-resistant tobacco (Nicotiana tabacum) mutant relative to wild-type plants at 21 and 42% O(2) has been confirmed and further investigated. Self-pollination of an M(3) mutant produced M(4) progeny segregating high catalase phenotypes (average 40% greater than wild type) at a frequency of about 60%. The high catalase phenotype cosegregated precisely with O(2)-resistant photosynthesis. About 25% of the F(1) progeny of reciprocal crosses between the same M(3) mutant and wild type had high catalase activity, whether the mutant was used as the maternal or paternal parent, indicating nuclear inheritance. In high-catalase mutants the activity of NADH-hydroxypyruvate reductase, another peroxisomal enzyme, was the same as wild type. The mutants released 15% less photorespiratory CO(2) as a percent of net photosynthesis in CO(2)-free 21% O(2) and 36% less in CO(2)-free 42% O(2) compared with wild type. The mutant leaf tissue also released less (14)CO(2) per [1-(14)C]glycolate metabolized than wild type in normal air, consistent with less photorespiration in the mutant. The O(2)-resistant photosynthesis appears to be caused by a decrease in photorespiration especially under conditions of high O(2) where the stoichiometry of CO(2) release per glycolate metabolized is expected to be enhanced. The higher catalase activity in the mutant may decrease the nonenzymatic peroxidation of keto-acids such as hydroxypyruvate and glyoxylate by photorespiratory H(2)O(2).
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Claims 10
Claim · model-written summary
Mutant M(4) progeny had greater net photosynthesis than wild type at 21 and 42% O(2).
- Taxon
- tobacco
Nicotiana tabacume0 - Material
- M(4) progenye0
- Outcome
- net photosynthesise0
- Direction
- increasee0
- Qualifier
- at 21 and 42% O(2)e0
- Comparator
- wild-type plantse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The increase in net photosynthesis in M(4) progeny of an O(2)-resistant tobacco (Nicotiana tabacum) mutant relative to wild-type plants at 21 and 42% O(2) has been confirmed”
Claim · model-written summary
About 60% of M(4) progeny segregated high catalase phenotypes averaging 40% greater than wild type.
- Taxon
- tobaccoNicotiana tabacumt0
- Material
- M(4) progenye0
- Outcome
- high catalase phenotypese0
- Value
- 40%e0
- Qualifier
- at a frequency of about 60%e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“M(4) progeny segregating high catalase phenotypes (average 40% greater than wild type) at a frequency of about 60%”
t0“Tobacco”
Claim · model-written summary
High catalase phenotype cosegregated with oxygen resistant photosynthesis.
- Taxon
- tobaccoNicotiana tabacumt0
- Material
- high catalase phenotypee0
- Outcome
- O(2)-resistant photosynthesise0
- Qualifier
- high catalase phenotype cosegregated preciselye0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The high catalase phenotype cosegregated precisely with O(2)-resistant photosynthesis”
t0“Tobacco”
Claim · model-written summary
About 25% of F(1) progeny had high catalase activity regardless of mutant parent sex, indicating nuclear inheritance.
- Taxon
- tobaccoNicotiana tabacumt0
- Material
- F(1) progenye0
- Outcome
- high catalase activitye0
- Value
- 25%e0
- Qualifier
- indicating nuclear inheritancee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“About 25% of the F(1) progeny of reciprocal crosses between the same M(3) mutant and wild type had high catalase activity, whether the mutant was used as the maternal or paternal parent, indicating nuclear inheritance”
t0“Tobacco”
Claim · model-written summary
NADH-hydroxypyruvate reductase activity in high-catalase mutants matched wild type.
- Taxon
- tobaccoNicotiana tabacumt0
- Material
- high-catalase mutantse0
- Gene
- NADH-hydroxypyruvate reductasee0
- Outcome
- activity of NADH-hydroxypyruvate reductasee0
- Direction
- same ase0
- Comparator
- wild typee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“In high-catalase mutants the activity of NADH-hydroxypyruvate reductase, another peroxisomal enzyme, was the same as wild type”
t0“Tobacco”
Claim · model-written summary
Mutants released 15% less photorespiratory CO(2) at 21% O(2).
- Taxon
- tobaccoNicotiana tabacumt0
- Material
- mutantse0
- Outcome
- photorespiratory CO(2)e0
- Direction
- lesse0
- Value
- 15%e0
- Qualifier
- CO(2)-free 21% O(2)e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The mutants released 15% less photorespiratory CO(2) as a percent of net photosynthesis in CO(2)-free 21% O(2)”
t0“Tobacco”
Claim · model-written summary
Mutants released 36% less photorespiratory CO(2) at 42% O(2).
- Taxon
- tobaccoNicotiana tabacumt0
- Material
- mutantse1
- Outcome
- photorespiratory CO(2)e1
- Direction
- lesse0
- Value
- 36%e0
- Comparator
- wild typee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“36% less in CO(2)-free 42% O(2) compared with wild type”
t0“Tobacco”
e1“The mutants released 15% less photorespiratory CO(2) as a percent of net photosynthesis in CO(2)-free 21% O(2) and 36% less in CO(2)-free 42% O(2) compared with wild type”
Claim · model-written summary
Mutant leaf tissue released less labeled CO(2) per glycolate metabolized than wild type.
- Taxon
- tobaccoNicotiana tabacumt0
- Organ / stage
- leaf tissuee0
- Outcome
- (14)CO(2) per [1-(14)C]glycolate metabolizede0
- Direction
- lesse0
- Qualifier
- normal aire0
- Comparator
- wild typee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The mutant leaf tissue also released less (14)CO(2) per [1-(14)C]glycolate metabolized than wild type in normal air”
t0“Tobacco”
Claim · model-written summary
The authors attributed oxygen resistant photosynthesis to decreased photorespiration.
- Taxon
- tobaccoNicotiana tabacumt0
- Outcome
- O(2)-resistant photosynthesise0
- Direction
- decreasee0
- Qualifier
- decrease in photorespiratione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The O(2)-resistant photosynthesis appears to be caused by a decrease in photorespiration especially under conditions of high O(2)”
t0“Tobacco”
Claim · model-written summary
The authors proposed that higher catalase activity may reduce keto acid peroxidation by photorespiratory peroxide.
- Taxon
- tobaccoNicotiana tabacumt0
- Outcome
- nonenzymatic peroxidation of keto-acidse0
- Direction
- decreasee0
- Qualifier
- higher catalase activitye0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The higher catalase activity in the mutant may decrease the nonenzymatic peroxidation of keto-acids such as hydroxypyruvate and glyoxylate by photorespiratory H(2)O(2)”
t0“Tobacco”