Abstract
PSI cyclic electron transport is essential for photosynthesis and photoprotection. In higher plants, the antimycin A-sensitive pathway is the main route of electrons in PSI cyclic electron transport. Although a small thylakoid protein, PGR5 (PROTON GRADIENT REGULATION 5), is essential for this pathway, its function is still unclear, and there are numerous debates on the rate of electron transport in vivo and its regulation. To assess how PGR5-dependent PSI cyclic electron transport is regulated in vivo, we characterized its activity in ruptured chloroplasts isolated from Arabidopsis thaliana. The activity of ferredoxin (Fd)-dependent plastoquinone (PQ) reduction in the dark is impaired in the pgr5 mutant. Alkalinization of the reaction medium enhanced the activity of Fd-dependent PQ reduction in the wild type. Even weak actinic light (AL) illumination also markedly activated PGR5-dependent PSI cyclic electron transport in ruptured chloroplasts. Even in the presence of linear electron transport [11 mumol O2 (mg Chl)(-1) h(-1)], PGR5-dependent PSI electron transport was detected as a difference in Chl fluorescence levels in ruptured chloroplasts. In the wild type, PGR5-dependent PSI cyclic electron transport competed with NADP+ photoreduction. These results suggest that the rate of PGR5-dependent PSI cyclic electron transport is high enough to balance the production ratio of ATP and NADPH during steady-state photosynthesis, consistently with the pgr5 mutant phenotype. Our results also suggest that the activity of PGR5-dependent PSI cyclic electron transport is regulated by the redox state of the NADPH pool.
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Claims 7
Claim · model-written summary
Ferredoxin-dependent plastoquinone reduction in the dark is impaired in the pgr5 mutant.
- Taxon
- Arabidopsis thaliana
Arabidopsis thalianae0 - Material
- pgr5 mutante1
- Outcome
- activity of ferredoxin (Fd)-dependent plastoquinone (PQ) reduction in the darke1
- Direction
- impairede1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“ruptured chloroplasts isolated from Arabidopsis thaliana”
e1“The activity of ferredoxin (Fd)-dependent plastoquinone (PQ) reduction in the dark is impaired in the pgr5 mutant”
Claim · model-written summary
Alkalinization of the reaction medium enhanced Fd-dependent PQ reduction in the wild type.
- Taxon
- Arabidopsis thalianaArabidopsis thalianae0
- Material
- wild typee2
- Treatment
- Alkalinization of the reaction mediume2
- Outcome
- activity of Fd-dependent PQ reductione2
- Direction
- enhancede2
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“ruptured chloroplasts isolated from Arabidopsis thaliana”
e2“Alkalinization of the reaction medium enhanced the activity of Fd-dependent PQ reduction in the wild type”
Claim · model-written summary
Weak actinic light illumination markedly activated PGR5-dependent PSI cyclic electron transport in ruptured chloroplasts.
- Taxon
- Arabidopsis thalianaArabidopsis thalianae0
- Organ / stage
- ruptured chloroplastse3
- Treatment
- weak actinic light (AL) illuminatione3
- Outcome
- PGR5-dependent PSI cyclic electron transporte3
- Direction
- activatede3
- Qualifier
- markedlye3
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“ruptured chloroplasts isolated from Arabidopsis thaliana”
e3“Even weak actinic light (AL) illumination also markedly activated PGR5-dependent PSI cyclic electron transport in ruptured chloroplasts”
Claim · model-written summary
PGR5-dependent PSI electron transport was detected as a difference in Chl fluorescence even in the presence of linear electron transport.
- Taxon
- Arabidopsis thalianaArabidopsis thalianae0
- Organ / stage
- ruptured chloroplastse4
- Outcome
- PGR5-dependent PSI electron transporte4
- Qualifier
- as a difference in Chl fluorescence levelse4
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“ruptured chloroplasts isolated from Arabidopsis thaliana”
e4“Even in the presence of linear electron transport [11 mumol O2 (mg Chl)(-1) h(-1)], PGR5-dependent PSI electron transport was detected as a difference in Chl fluorescence levels in ruptured chloroplasts”
Claim · model-written summary
In the wild type, PGR5-dependent PSI cyclic electron transport competed with NADP+ photoreduction.
- Taxon
- Arabidopsis thalianaArabidopsis thalianae0
- Material
- wild typee5
- Outcome
- PGR5-dependent PSI cyclic electron transporte5
- Qualifier
- competed with NADP+ photoreductione5
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“ruptured chloroplasts isolated from Arabidopsis thaliana”
e5“In the wild type, PGR5-dependent PSI cyclic electron transport competed with NADP+ photoreduction”
Claim · model-written summary
PGR5-dependent PSI cyclic electron transport is high enough to balance the production ratio of ATP and NADPH during steady-state photosynthesis.
- Taxon
- Arabidopsis thalianaArabidopsis thalianae0
- Outcome
- production ratio of ATP and NADPHe6
- Qualifier
- the rate of PGR5-dependent PSI cyclic electron transport is high enough to balancee6
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“ruptured chloroplasts isolated from Arabidopsis thaliana”
e6“These results suggest that the rate of PGR5-dependent PSI cyclic electron transport is high enough to balance the production ratio of ATP and NADPH during steady-state photosynthesis”
Claim · model-written summary
The activity of PGR5-dependent PSI cyclic electron transport is regulated by the redox state of the NADPH pool.
- Taxon
- Arabidopsis thalianaArabidopsis thalianae0
- Compound
- NADPHe7
- Outcome
- activity of PGR5-dependent PSI cyclic electron transporte7
- Qualifier
- regulated by the redox state of the NADPH poole7
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“ruptured chloroplasts isolated from Arabidopsis thaliana”
e7“Our results also suggest that the activity of PGR5-dependent PSI cyclic electron transport is regulated by the redox state of the NADPH pool”
The same questions in other papers
light · physiology: photosynthesis · Arabidopsis thaliana (thale cress)Positive and negative results
10 papers in the same direction as this paper · 18 in the opposite direction · 1 reporting no difference from an alternative
- negative
- negative
- negative
26 papers more in this group
See all 30 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.