Abstract
The importance of the mitochondrial electron transport chain in photosynthesis was studied using the tobacco (Nicotiana sylvestris) mutant CMSII, which lacks functional complex I. Rubisco activities and oxygen evolution at saturating CO(2) showed that photosynthetic capacity in the mutant was at least as high as in wild-type (WT) leaves. Despite this, steady-state photosynthesis in the mutant was reduced by 20% to 30% at atmospheric CO(2) levels. The inhibition of photosynthesis was alleviated by high CO(2) or low O(2). The mutant showed a prolonged induction of photosynthesis, which was exacerbated in conditions favoring photorespiration and which was accompanied by increased extractable NADP-malate dehydrogenase activity. Feeding experiments with leaf discs demonstrated that CMSII had a lower capacity than the WT for glycine (Gly) oxidation in the dark. Analysis of the postillumination burst in CO(2) evolution showed that this was not because of insufficient Gly decarboxylase capacity. Despite the lower rate of Gly metabolism in CMSII leaves in the dark, the Gly to Ser ratio in the light displayed a similar dependence on photosynthesis to the WT. It is concluded that: (a) Mitochondrial complex I is required for optimal photosynthetic performance, despite the operation of alternative dehydrogenases in CMSII; and (b) complex I is necessary to avoid redox disruption of photosynthesis in conditions where leaf mitochondria must oxidize both respiratory and photorespiratory substrates simultaneously.
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Claims 11
Claim · model-written summary
CMSII Rubisco activity and oxygen evolution at saturating CO2 were at least as high as wild type.
- Taxon
- Tobacco
Nicotiana tabacumt0 - Material
- CMSIIe1
- Outcome
- photosynthetic capacitye0
- Direction
- at least as highe0
- Comparator
- wild-type (WT) leavese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Rubisco activities and oxygen evolution at saturating CO(2) showed that photosynthetic capacity in the mutant was at least as high as in wild-type (WT) leaves”
t0“Tobacco”
e1“mutant CMSII”
Claim · model-written summary
CMSII steady state photosynthesis was 20% to 30% lower at atmospheric CO2.
- Taxon
- tobaccoNicotiana tabacumt0
- Material
- CMSIIe1
- Outcome
- steady-state photosynthesise0
- Direction
- reducede0
- Value
- 20% to 30%e0
- Qualifier
- atmospheric CO(2) levelse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“steady-state photosynthesis in the mutant was reduced by 20% to 30% at atmospheric CO(2) levels”
t0“tobacco”
e1“mutant CMSII”
Claim · model-written summary
High CO2 alleviated photosynthesis inhibition in CMSII.
- Taxon
- tobaccoNicotiana tabacumt0
- Material
- CMSIIe1
- Treatment
- high CO(2)e0
- Outcome
- inhibition of photosynthesise0
- Direction
- alleviatede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The inhibition of photosynthesis was alleviated by high CO(2) or low O(2)”
t0“tobacco”
e1“mutant CMSII”
Claim · model-written summary
Low O2 alleviated photosynthesis inhibition in CMSII.
- Taxon
- tobaccoNicotiana tabacumt0
- Material
- CMSIIe1
- Treatment
- low O(2)e0
- Outcome
- inhibition of photosynthesise0
- Direction
- alleviatede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The inhibition of photosynthesis was alleviated by high CO(2) or low O(2)”
t0“tobacco”
e1“mutant CMSII”
Claim · model-written summary
CMSII had prolonged photosynthesis induction, especially under photorespiratory conditions.
- Taxon
- tobaccoNicotiana tabacumt0
- Material
- CMSIIe1
- Outcome
- induction of photosynthesise0
- Direction
- prolongede0
- Qualifier
- conditions favoring photorespiratione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The mutant showed a prolonged induction of photosynthesis, which was exacerbated in conditions favoring photorespiration”
t0“tobacco”
e1“mutant CMSII”
Claim · model-written summary
CMSII had increased extractable NADP-malate dehydrogenase activity.
- Taxon
- tobaccoNicotiana tabacumt0
- Material
- CMSIIe1
- Gene
- NADP-malate dehydrogenasee0
- Outcome
- extractable NADP-malate dehydrogenase activitye0
- Direction
- increasede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“accompanied by increased extractable NADP-malate dehydrogenase activity”
t0“tobacco”
e1“mutant CMSII”
Claim · model-written summary
CMSII had less capacity than wild type for dark glycine oxidation.
- Taxon
- tobaccoNicotiana tabacumt0
- Material
- CMSIIe0
- Outcome
- glycine (Gly) oxidatione0
- Direction
- lowere0
- Qualifier
- in the darke0
- Comparator
- WTe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“CMSII had a lower capacity than the WT for glycine (Gly) oxidation in the dark”
t0“tobacco”
Claim · model-written summary
Gly decarboxylase capacity was not insufficient to explain reduced Gly oxidation.
- Taxon
- tobaccoNicotiana tabacumt0
- Gene
- Gly decarboxylasee0
- Outcome
- Gly decarboxylase capacitye0
- Direction
- not because of insufficiente0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“this was not because of insufficient Gly decarboxylase capacity”
t0“tobacco”
Claim · model-written summary
Light Gly to Ser ratio depended on photosynthesis similarly in CMSII and wild type.
- Taxon
- tobaccoNicotiana tabacumt0
- Material
- CMSIIe1
- Outcome
- Gly to Ser ratioe0
- Direction
- similare0
- Comparator
- WTe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the Gly to Ser ratio in the light displayed a similar dependence on photosynthesis to the WT”
t0“tobacco”
e1“mutant CMSII”
Claim · model-written summary
The authors conclude that mitochondrial complex I is needed for optimal photosynthetic performance.
- Taxon
- tobaccoNicotiana tabacumt0
- Gene
- Mitochondrial complex Ie0
- Outcome
- photosynthetic performancee0
- Direction
- optimale0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Mitochondrial complex I is required for optimal photosynthetic performance”
t0“tobacco”
Claim · model-written summary
The authors conclude complex I prevents redox disruption when mitochondria oxidize respiratory and photorespiratory substrates simultaneously.
- Taxon
- tobaccoNicotiana tabacumt0
- Gene
- complex Ie0
- Outcome
- redox disruption of photosynthesise0
- Qualifier
- leaf mitochondria must oxidize both respiratory and photorespiratory substrates simultaneouslye0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“complex I is necessary to avoid redox disruption of photosynthesis in conditions where leaf mitochondria must oxidize both respiratory and photorespiratory substrates simultaneously”
t0“tobacco”
The same questions in other papers
co2 · physiology: photosynthesis · Nicotiana tabacum (tobacco)Positive and negative results
9 papers in the same direction as this paper · 6 in the opposite direction
- no effect
- negative
- negative
12 papers more in this group
See all 16 papers →Claims are grouped by organism, treatment and what was measured or targeted. A paper counts as positive when any of its claims in the group is positive.