PROTON GRADIENT REGULATION 5 supports linear electron flow to oxidize photosystem I

2018 ◽  
Vol 164 (3) ◽  
pp. 337-348 ◽  
Author(s):  
Daisuke Takagi ◽  
Chikahiro Miyake
Keyword(s):  
Photosystem I ◽  
Electron Flow ◽  
Proton Gradient ◽  
Linear Electron

The Effect of Deoxycholate-Treatment to the Photoreactions of the Active Pigments in Photosynthesis

1976 ◽  
Vol 31 (1-2) ◽  
pp. 64-67 ◽  
Author(s):  
Günter Döring
Keyword(s):  
Photosystem Ii ◽  
Chlorophyll A ◽  
Photosystem I ◽  
Electron Flow ◽  
Heavy Fraction ◽  
Sodium Ascorbate ◽  
Linear Electron ◽  
System P ◽  
Heat Treated ◽  
Donor System

Abstract In the heavy fraction of deoxycholate-treated spinach chloroplasts the chlorophyll an activity is high and the chlorophyll aI activity is low when no artificial electron donor is added. The addition of the photosystem I donor system N-methyl-phenazonium sulphate plus sodium ascorbate (PMS + Asc) leads to a complete reactivation of the chlorophyll aI reaction. The addition of the photo­system II donor system p-benzohydroquinone plus sodium ascorbate (HQ + Asc) leads to an inhibition of the chlorophyll aII activity. From these results we conclude: 1. Besides an interruption of the linear electron flow between the two photosystems deoxycholate-treatment leads to a block of the electron flow from water to photosystem II. 2. In deoxycholate-treated chloroplasts the linear electron flow in photosystem II just like in Triswashed, heat-treated or aged chloroplasts, is replaced by a cyclic one.

scholarly journals Intrinsic Fluctuations in Transpiration Induce Photorespiration to Oxidize P700 in Photosystem I

Plants ◽  
2020 ◽  
Vol 9 (12) ◽  
pp. 1761
Author(s):  
Riu Furutani ◽  
Amane Makino ◽  
Yuij Suzuki ◽  
Shinya Wada ◽  
Ginga Shimakawa ◽  
...  
Keyword(s):  
Photosystem I ◽  
Electron Flow ◽  
Co2 Assimilation ◽  
Proton Gradient ◽  
Assimilation Rate ◽  
Oxidation Level ◽  
Co2 Assimilation Rate ◽  
Net Co2 Assimilation Rate ◽  
Net Co2 Assimilation ◽  
Intrinsic Fluctuations

Upon exposure to environmental stress, the primary electron donor in photosystem I (PSI), P700, is oxidized to suppress the production of reactive oxygen species that could oxidatively inactivate the function of PSI. The illumination of rice leaves with actinic light induces intrinsic fluctuations in the opening and closing of stomata, causing the net CO2 assimilation rate to fluctuate. We examined the effects of these intrinsic fluctuations on electron transport reactions. Under atmospheric O2 conditions (21 kPa), the effective quantum yield of photosystem II (PSII) (Y(II)) remained relatively high while the net CO2 assimilation rate fluctuated, which indicates the function of alternative electron flow. By contrast, under low O2 conditions (2 kPa), Y(II) fluctuated. These results suggest that photorespiration primarily drove the alternative electron flow. Photorespiration maintained the oxidation level of ferredoxin (Fd) throughout the fluctuation of the net CO2 assimilation rate. Moreover, the relative activity of photorespiration was correlated with both the oxidation level of P700 and the magnitude of the proton gradient across the thylakoid membrane in 21 kPa O2 conditions. These results show that photorespiration oxidized P700 by stimulating the proton gradient formation when CO2 assimilation was suppressed by stomatal closure.

Cyclic electron flow around photosystem I is enhanced at low pH

2014 ◽  
Vol 83 ◽  
pp. 194-199 ◽  
Author(s):  
Teena Tongra ◽  
Sudhakar Bharti ◽  
Anjana Jajoo
Keyword(s):  
Photosystem I ◽  
Electron Flow ◽  
Low Ph ◽  
Cyclic Electron Flow

scholarly journals ATP compartmentation in plastids and cytosol ofArabidopsis thalianarevealed by fluorescent protein sensing

2018 ◽  
Vol 115 (45) ◽  
pp. E10778-E10787 ◽  
Author(s):  
Chia Pao Voon ◽  
Xiaoqian Guan ◽  
Yuzhe Sun ◽  
Abira Sahu ◽  
May Ngor Chan ◽  
...  
Keyword(s):  
Arabidopsis Thaliana ◽  
Fluorescent Protein ◽  
Higher Plants ◽  
Electron Flow ◽  
Cyclic Electron Flow ◽  
Linear Electron ◽  
Protein Sensing ◽  
Atp Production ◽  
Respiratory Inhibitors ◽  
Sensor Protein

Matching ATP:NADPH provision and consumption in the chloroplast is a prerequisite for efficient photosynthesis. In terms of ATP:NADPH ratio, the amount of ATP generated from the linear electron flow does not meet the demand of the Calvin–Benson–Bassham (CBB) cycle. Several different mechanisms to increase ATP availability have evolved, including cyclic electron flow in higher plants and the direct import of mitochondrial-derived ATP in diatoms. By imaging a fluorescent ATP sensor protein expressed in livingArabidopsis thalianaseedlings, we found that MgATP2−concentrations were lower in the stroma of mature chloroplasts than in the cytosol, and exogenous ATP was able to enter chloroplasts isolated from 4- and 5-day-old seedlings, but not chloroplasts isolated from 10- or 20-day-old photosynthetic tissues. This observation is in line with the previous finding that the expression of chloroplast nucleotide transporters (NTTs) inArabidopsismesophyll is limited to very young seedlings. Employing a combination of photosynthetic and respiratory inhibitors with compartment-specific imaging of ATP, we corroborate the dependency of stromal ATP production on mitochondrial dissipation of photosynthetic reductant. Our data suggest that, during illumination, the provision and consumption of ATP:NADPH in chloroplasts can be balanced by exporting excess reductants rather than importing ATP from the cytosol.

scholarly journals PsaE Is Required for in Vivo Cyclic Electron Flow around Photosystem I in the Cyanobacterium Synechococcus sp. PCC 7002

1993 ◽  
Vol 103 (1) ◽  
pp. 171-180 ◽  
Author(s):  
L. Yu ◽  
J. Zhao ◽  
U. Muhlenhoff ◽  
D. A. Bryant ◽  
J. H. Golbeck
Keyword(s):  
Photosystem I ◽  
Electron Flow ◽  
Cyclic Electron Flow ◽  
Synechococcus Sp
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