Abstract
The effects of exposure to increasing manganese concentrations (50-1500 µM) from the start of the experiment on the functional performance of photosystem II (PSII) and photosystem I (PSI) and photosynthetic apparatus composition of Arabidopsis thaliana were compared. In agreement with earlier studies, excess Mn caused minimal changes in the PSII photochemical efficiency measured as F(v)/F(m), although the characteristic peak temperature of the S(2/3)Q(B) (-) charge recombinations was shifted to lower temperatures at the highest Mn concentration. SDS-PAGE and immunoblot analyses also did not exhibit any significant change in the relative abundance of PSII-associated polypeptides: PSII reaction centre protein D1, Lhcb1 (major light-harvesting protein of LHCII complex), and PsbO (OEC33, a 33 kDa protein of the oxygen-evolving complex). In addition, the abundance of Rubisco also did not change with Mn treatments. However, plants grown under excess Mn exhibited increased susceptibility to PSII photoinhibition. In contrast, in vivo measurements of the redox transients of PSI reaction centre (P700) showed a considerable gradual decrease in the extent of P700 photooxidation (P700(+)) under increased Mn concentrations compared to control. This was accompanied by a slower rate of P700(+) re-reduction indicating a downregulation of the PSI-dependent cyclic electron flow. The abundance of PSI reaction centre polypeptides (PsaA and PsaB) in plants under the highest Mn concentration was also significantly lower compared to the control. The results demonstrate for the first time that PSI is the major target of Mn toxicity within the photosynthetic apparatus of Arabidopsis plants. The possible involvement mechanisms of Mn toxicity targeting specifically PSI are discussed.
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Claims 10
Claim · model-written summary
Excess Mn caused minimal changes in PSII photochemical efficiency.
- Taxon
- Arabidopsis thaliana
Arabidopsis thalianae1 - Treatment
- excess Mne2
- Outcome
- PSII photochemical efficiencye2
- Direction
- minimal changese2
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“photosynthetic apparatus composition of Arabidopsis thaliana were compared”
e2“excess Mn caused minimal changes in the PSII photochemical efficiency measured as F(v)/F(m)”
Claim · model-written summary
Excess Mn shifted the peak temperature of S(2/3)Q(B) charge recombinations to lower temperatures at the highest Mn concentration.
- Taxon
- Arabidopsis thalianaArabidopsis thalianae1
- Treatment
- excess Mne2
- Outcome
- peak temperature of the S(2/3)Q(B) (-) charge recombinationse3
- Direction
- shifted to lower temperaturese3
- Qualifier
- at the highest Mn concentratione3
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“photosynthetic apparatus composition of Arabidopsis thaliana were compared”
e2“excess Mn caused minimal changes in the PSII photochemical efficiency measured as F(v)/F(m)”
e3“the characteristic peak temperature of the S(2/3)Q(B) (-) charge recombinations was shifted to lower temperatures at the highest Mn concentration”
Claim · model-written summary
Plants grown under excess Mn showed increased susceptibility to PSII photoinhibition.
- Taxon
- Arabidopsis thalianaArabidopsis thalianae1
- Treatment
- excess Mne5
- Outcome
- susceptibility to PSII photoinhibitione5
- Direction
- increasede5
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“photosynthetic apparatus composition of Arabidopsis thaliana were compared”
e5“plants grown under excess Mn exhibited increased susceptibility to PSII photoinhibition”
Claim · model-written summary
Excess Mn did not change the relative abundance of PSII-associated polypeptides.
- Taxon
- Arabidopsis thalianaArabidopsis thalianae1
- Treatment
- excess Mne2
- Outcome
- relative abundance of PSII-associated polypeptidese3
- Direction
- did not exhibit any significant changee3
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“photosynthetic apparatus composition of Arabidopsis thaliana were compared”
e2“excess Mn caused minimal changes in the PSII photochemical efficiency measured as F(v)/F(m)”
e3“SDS-PAGE and immunoblot analyses also did not exhibit any significant change in the relative abundance of PSII-associated polypeptides”
Claim · model-written summary
Mn treatments did not change the abundance of Rubisco.
- Taxon
- Arabidopsis thalianaArabidopsis thalianae1
- Treatment
- Mn treatmentse4
- Outcome
- abundance of Rubiscoe4
- Direction
- did not changee4
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“photosynthetic apparatus composition of Arabidopsis thaliana were compared”
e4“the abundance of Rubisco also did not change with Mn treatments”
Claim · model-written summary
Increased Mn concentrations decreased the extent of P700 photooxidation compared with control.
- Taxon
- Arabidopsis thalianaArabidopsis thalianae1
- Treatment
- increased Mn concentrationse6
- Outcome
- extent of P700 photooxidatione6
- Direction
- decreasee6
- Comparator
- controle6
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“photosynthetic apparatus composition of Arabidopsis thaliana were compared”
e6“showed a considerable gradual decrease in the extent of P700 photooxidation (P700(+)) under increased Mn concentrations compared to control”
Claim · model-written summary
Increased Mn concentrations slowed the rate of P700(+) re-reduction compared with control.
- Taxon
- Arabidopsis thalianaArabidopsis thalianae1
- Treatment
- increased Mn concentrationse6
- Outcome
- rate of P700(+) re-reductione7
- Direction
- slowere7
- Comparator
- controle6
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“photosynthetic apparatus composition of Arabidopsis thaliana were compared”
e6“showed a considerable gradual decrease in the extent of P700 photooxidation (P700(+)) under increased Mn concentrations compared to control”
e7“This was accompanied by a slower rate of P700(+) re-reduction indicating a downregulation of the PSI-dependent cyclic electron flow”
Claim · model-written summary
Excess Mn indicates a downregulation of PSI-dependent cyclic electron flow.
- Taxon
- Arabidopsis thalianaArabidopsis thalianae1
- Outcome
- PSI-dependent cyclic electron flowe7
- Qualifier
- slower rate of P700(+) re-reductione7
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“photosynthetic apparatus composition of Arabidopsis thaliana were compared”
e7“This was accompanied by a slower rate of P700(+) re-reduction indicating a downregulation of the PSI-dependent cyclic electron flow”
Claim · model-written summary
Abundance of PSI reaction centre polypeptides PsaA and PsaB was significantly lower under the highest Mn concentration than in the control.
- Taxon
- Arabidopsis thalianaArabidopsis thalianae1
- Treatment
- highest Mn concentratione2
- Outcome
- abundance of PSI reaction centre polypeptides (PsaA and PsaB)e2
- Direction
- significantly lowere2
- Comparator
- controle2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“photosynthetic apparatus composition of Arabidopsis thaliana were compared”
e2“The abundance of PSI reaction centre polypeptides (PsaA and PsaB) in plants under the highest Mn concentration was also significantly lower compared to the control”
Claim · model-written summary
PSI is the major target of Mn toxicity within the photosynthetic apparatus of Arabidopsis.
Verbatim
e2“The results demonstrate for the first time that PSI is the major target of Mn toxicity within the photosynthetic apparatus of Arabidopsis plants”
The same questions in other papers
manganese atom · pest · Arabidopsis thaliana (thale cress)Positive and negative results
1 in the opposite direction
- positive
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.