A theoretical study of a relationship between the photosystem II fluorescence and the redox state of the electron transport chain of higher plants

Chlorella vulgaris acclimated to high light (HL) conditions exhibited a pale-green phenotype characterized by reduced chlorophyll and light harvesting polypeptide abundance compared with the dark green phenotype of the control, low-light-grown (LL) cultures. We hypothesized that if chloroplast redox status was the sole regulator of phenotype, exposure to darkness should cause reversion of the HL to LL phenotype. Surprisingly, HL cells transferred to darkness or dim light failed to green. Thus, phenotypic reversion is light-dependent with an optimal photon flux density (PFD) of 110 μmol photons·m−2·s−1. HL cells shifted to this PFD exhibited increased chlorophyll and light harvesting polypeptide abundance, which were inhibited by 2,5-dibromo-3-methyl-6-isopropyl-benzoquinone but not by 3-(3′,4′-dichlorophenyl)-1,1-dimethylurea. We conclude that photoacclimation of HL-grown cells to LL is governed by the redox state of the intersystem photosynthetic electron transport chain (PETC) at this PFD. At lower light levels, cells maintained the HL phenotype, despite an oxidized status of the PETC. Because 110 μmol photons·m−2·s−1 was the optimal PFD for protochlorophyllide oxidoreductase accumulation, we suggest that stabilization of light-harvesting polypeptides by chlorophyll binding may also govern photoacclimation in C. vulgaris. The possible role of the metabolic balance between respiration and photosynthesis is also discussed.

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NMR relaxivity changes in chloroplast suspensions. Effects of NH2OH and of treatments altering the redox state of the photosynthetic electron transport chain

Biochimica et Biophysica Acta (BBA) - Bioenergetics ◽

10.1016/0005-2728(80)90077-8 ◽

1980 ◽

Vol 593 (2) ◽

pp. 414-426 ◽

Cited By ~ 10

Author(s):

H.H. Robinson ◽

R.R. Sharp ◽

C.F. Yocum

Keyword(s):

Electron Transport ◽

Electron Transport Chain ◽

Redox State ◽

Photosynthetic Electron Transport ◽

Photosynthetic Electron Transport Chain ◽

Transport Chain

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Expression of Glutamate Dehydrogenase Genes In Arabidopsis Thaliana Depends on The Redox State of Chloroplast Electron Transport Chain

10.21203/rs.3.rs-176434/v1 ◽

2021 ◽

Author(s):

Elena Yu. Garnik ◽

Vadim I. Belkov ◽

Vladislav I. Tarasenko ◽

Yury M. Konstantinov

Keyword(s):

Arabidopsis Thaliana ◽

Electron Transport ◽

Glutamate Dehydrogenase ◽

Electron Transport Chain ◽

Redox State ◽

Photosynthetic Electron Transport ◽

Glucose Content ◽

Tetrapyrrole Synthesis ◽

Transport Chain ◽

Significant Difference

Abstract Plant glutamate dehydrogenase is an enzyme interconverting L-glutamate and 2-oxoglutarate and providing a link between carbon and nitrogen metabolism. In Arabidopsis thaliana, this enzyme is encoded by three genes. Two of them, GDH1 and GDH2, provide most of the enzyme activity in plant leaves and roots. Expression of GDH1 and GDH2 genes is very low in the light and high in the dark. The molecular signals and mechanisms that provide the light-dependent GDH genes regulation remain unknown. Using photosynthetic electron transport inhibitors 3-(3.4-dichlorophenyl)-1.1-dimethylurea (DCMU) and 2.5-dibromo-3-methyl-6-isopropyl benzoquinone (DBMIB) we demonstrate that transcript levels of the GDH1 and GDH2 genes in Arabidopsis leaves change in accordance with a redox state of chloroplast electron transport chain: they are low when it is highly reduced and high when it is oxidized. Hydrogen peroxide or high light treatment did not result in decreasing of GDH1 or GDH2 expression, so reactive oxygen species cannot be the signals that reduce expression of these genes during dark-to-light shifts. There was no significant difference between the glucose content in the leaves of plants treated with DCMU and the plants treated with DBMIB, so glucose is not the only or the main factor that regulates expression of the studied genes. We presume that expression of Arabidopsis GDH1 and GDH2 genes depends on the chloroplast electron transport chain redox state. This regulatory mechanism could arise because of a need to avoid a competition for substrate between tetrapyrrole synthesis, glutathione synthesis and using of L-glutamate as an energy source during prolonged darkness.

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Site of Action of 2,5-Dimethoxy-3,6-Dichloro-p-Benzoquinone in the Photosynthetic Electron Transport Chain

Zeitschrift für Naturforschung C ◽

10.1515/znc-1981-7-825 ◽

1981 ◽

Vol 36 (7-8) ◽

pp. 656-661 ◽

Cited By ~ 10

Author(s):

G. Sarojini ◽

H. Daniell

Keyword(s):

Electron Transport ◽

Photosystem Ii ◽

Electron Transport Chain ◽

Electron Transport Rate ◽

Electron Flow ◽

Electron Acceptors ◽

Hill Reaction ◽

Transport Chain ◽

Site Of Action ◽

The Hill

Abstract Electron Acceptors, Photosystem II, Quinones and Quinonediamines Dichlorodimethoxy-/?-benzoquinone (DCDMQ) was tested for its site of action in the photo synthetic electron transport chain. Hill reaction mediated by DCDMQ was insensitive to DBMIB (1 nm) but sensitive to DCMU, suggesting its site of action before plastoquinone but after Q -the primary electron acceptor of photosystem II. Extraction of freeze-dried chloroplasts with heptane and analyzing their capacity to photo-oxidize water using various Hill oxidants revealed that silicomolybdate (SiMO) and DCDMQ could effectively restore the activity. Diaminodurene (DAD) in the presence of ferricyanide could restore 40% of the activity. But ferricyanide alone failed to restore the ability to photo-oxidize water in heptane extracted chloroplasts. Similarly, N a2S 0 3 which is known to cause a bottleneck in the electron flow at plastoquinone affected the ferricyanide Hill reaction. Hill reactions mediated by SiMO and DCDMQ were insensitive to the addition of Na2SO3, suggesting that both these oxidants intercept electrons before plastoquinone. But 50% of the activity was lost when sulfite was added to the Hill reaction mediated by DADox. DNP-INT, melittin and picrylhydrazyl were recently introduced as photosystem II inhibitors inhibiting the electron flow between Q and the PQ pool. While DCBQ and DCDMQ Hill reactions were insensitive to DNP-INT, ferricyanide was highly sensitive. The quinonediamines TMPD and DADox showed 50% decrease in the electron transport rate, similar to heptane extracted or sulfite inhibited chloroplasts. Melittin increased the electron transport rate when ferricyanide or TMPD was the Hill oxidant, while DCBQ and DCDMQ reduction remained unaffected. However, DADox Hill reaction showed 50% inhibition in the presence of melittin. Picrylhydrazyl - which inhibits the electron flow between Q and the PQ pool - inhibited the Hill reaction of all the PS II electron acceptors except that of DCDMQ. It is possible that there is another site of intercepting electrons between Q and plastoquinone before the site where most of the quinonediamines accept electrons.

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