scholarly journals Association of the Chloroplastic Respiratory and Photosynthetic Electron Transport Chains of Chlamydomonas reinhardii with Photoreduction and the Oxyhydrogen Reaction

1986 ◽  
Vol 80 (2) ◽  
pp. 364-368 ◽  
Author(s):  
Theodore E. Maione ◽  
Martin Gibbs
Keyword(s):  
Electron Transport ◽  
Photosynthetic Electron Transport ◽  
Chlamydomonas Reinhardii ◽  
Electron Transport Chains

Metribuzin-Resistant Mutants of Chlamydomonas reinhardii

1984 ◽  
Vol 39 (5) ◽  
pp. 437-439 ◽  
Author(s):  
N. Pucheu ◽  
W. Oettmeier ◽  
U. Heisterkamp ◽  
K. Masson ◽  
G.F. Wildner
Keyword(s):  
Electron Transport ◽  
Photosynthetic Electron Transport ◽  
Wild Type ◽  
Binding Studies ◽  
Molecular Weight Range ◽  
Chlamydomonas Reinhardii ◽  
Thylakoid Membrane Proteins ◽  
Mutant Strains ◽  
Resistant Mutants

Herbicide resistance in Chlamydomonas reinhardii cells was induced by mutagenesis with 5-fluorodeoxyuridine and ethylmethanesulfonate. Four mutant strains were isolated and analyzed for resistance against DCMU-type or phenolic inhibitors of photosynthetic electron transport. The mutants were different in both the extent and the pattern of their resistance: the R/S value, i.e. the ratio of I50 values of the inhibition of photosynthetic electron transport in isolated resistant and susceptible thylakoids, varied for metribuzin from 10 000 to 36. The mutant MZ-1 was resistant against metribuzin, atrazine and DCMU, whereas the mutant MZ-2 showed resistance mainly against metribuzin and atrazine. The mutant MZ-3 was similar to MZ-1, but showed a lesser extent of resistance against DCMU. The mutant MZ-4 showed resistance against metribuzin, but not against atrazine. These results demonstrate that the resistance against one herbicide of the DCMU-type (metribuzin) must not be accompanied by similar resistance against te other inhibitors. Binding studies with radioactively labeled herbicides, [14C]metribuzin, [14C]atrazine and [3H]DCMU, and isolated thylakoids supported these observations. Phosphorylation of thylakoid membrane proteins was studied with wild-type cells and resistant mutants under in vivo conditions in the light. The 32P-labeled main proteins bands were in the molecular weight range of 10-14 kDa, 26-29 kDa, 32-35 kDa and 46-48 kDa. The pattern and the extent of incorporation of 32P were similar for the mutants and the wild-type cells.

Inhibition of Photosynthetic Electron Transport by the Quinone Antagonist UHDBT

1981 ◽  
Vol 36 (3-4) ◽  
pp. 272-275 ◽  
Author(s):  
Walter Oettmeier ◽  
Klaus Masson ◽  
Doris Godde
Keyword(s):  
Electron Transport ◽  
Green Alga ◽  
Photosynthetic Electron Transport ◽  
Binding Studies ◽  
Chlamydomonas Reinhardii ◽  
Efficient Inhibitor ◽  
Low Concentrations

UHDBT (5-n-undecyl-6-hydroxy-4,7-dioxobenzothiazole) is an efficient inhibitor of photosynthetic electron transport in chloroplasts from spinach (pI50-value = 7.61) and the green alga Chlamydomonas reinhardii. At low concentrations of UHDBT its site of inhibition is located at the reducing side of plastoquinone, identical to that of 3-(3,4-dichlorophenyl)-1, 1-dimethylurea (DCMU). This became evident from functional as well as binding studies. At higher concentrations of UHDBT a secondary inhibition site at the oxidizing side of plastoquinone, identical to that of 2,5-dibromo-3-methyl-6-isopropyl-1,4-benzoquinone (DBMIB) becomes evident

scholarly journals Characterization of Light-Enhanced Respiration in Cyanobacteria

2020 ◽  
Vol 22 (1) ◽  
pp. 342
Author(s):  
Ginga Shimakawa ◽  
Ayaka Kohara ◽  
Chikahiro Miyake
Keyword(s):  
Electron Transport ◽  
Redox Homeostasis ◽  
Photosynthetic Electron Transport ◽  
Co2 Assimilation ◽  
O2 Evolution ◽  
Eukaryotic Algae ◽  
Electron Transport Chains ◽  
Physiological Analysis ◽  
Photosynthetic Co2 Assimilation ◽  
And Function

In eukaryotic algae, respiratory O2 uptake is enhanced after illumination, which is called light-enhanced respiration (LER). It is likely stimulated by an increase in respiratory substrates produced during photosynthetic CO2 assimilation and function in keeping the metabolic and redox homeostasis in the light in eukaryotic cells, based on the interactions among the cytosol, chloroplasts, and mitochondria. Here, we first characterize LER in photosynthetic prokaryote cyanobacteria, in which respiration and photosynthesis share their metabolisms and electron transport chains in one cell. From the physiological analysis, the cyanobacterium Synechocystis sp. PCC 6803 performs LER, similar to eukaryotic algae, which shows a capacity comparable to the net photosynthetic O2 evolution rate. Although the respiratory and photosynthetic electron transports share the interchain, LER was uncoupled from photosynthetic electron transport. Mutant analyses demonstrated that LER is motivated by the substrates directly provided by photosynthetic CO2 assimilation, but not by glycogen. Further, the light-dependent activation of LER was observed even with exogenously added glucose, implying a regulatory mechanism for LER in addition to the substrate amounts. Finally, we discuss the physiological significance of the large capacity of LER in cyanobacteria and eukaryotic algae compared to those in plants that normally show less LER.

Investigation on the Photosynthetic Membranes of Spruce Needles in Relation to the Occurrence of Novel Forest Decline I. The Photosynthetic Electron Transport

1988 ◽  
Vol 43 (7-8) ◽  
pp. 581-588 ◽  
Author(s):  
Bernhard Dietz ◽  
Iris Moors ◽  
Ute Flammersfeld ◽  
Wolfgang Rühle ◽  
Aloysius Wild
Keyword(s):  
Electron Transport ◽  
Electron Transport Rate ◽  
Membrane Damage ◽  
Photosynthetic Apparatus ◽  
Photosynthetic Electron Transport ◽  
Transport Rate ◽  
Electron Microscopic ◽  
Transport Pathway ◽  
Natural Habitats ◽  
Electron Transport Chains

The investigations described here were carried out in the context of our research project on the physiological, biochemical, and cytomorphological characterization of spruce trees growing in natural habitats and showing damage of varying intensity. Here we report on specific aspects of the photosynthetic apparatus. The aim of the measurements was to analyze whether or not the activity of the photosynthetic electron transport pathway is affected in damaged trees. The investigations were carried out on a 20 to 25-year-old spruce plantation in the Hunsrück mountains and on an 80-year-old spruce plantation in the Westerwald mountains. The photosynthetic electron transport rate was determined by photoreduction of 2,6-dichlorophenolindophenol. A decrease of the electron transport rate was shown in the damaged spruce trees in comparison to the apparently healthy trees. The investigation of the water splitting enzyme system - determined in the Hillreaction by feeding in electrons by means of diphenylcarbazide - indicates that the electron transport on the oxidizing side of photosystem II is impaired. The results imply that the photosynthetic electron transport chains in the thylakoid membranes of the spruce chloroplasts are sites of early injurious effects. This is in agreement with the electron microscopic analyses which show consistently that early damage occurs especially at the cellular membranes. This membrane damage is apparent even in the green needles of damaged spruce trees.

Plastoquinones in photosynthesis

1978 ◽  
Vol 284 (1002) ◽  
pp. 591-599 ◽  
Keyword(s):  
Electron Transport ◽  
Photosystem Ii ◽  
Energy Conservation ◽  
Thylakoid Membrane ◽  
Electron Flow ◽  
Proton Translocation ◽  
Photosynthetic Electron Transport ◽  
Atp Formation ◽  
Electron Transport Chains

Several plastoquinones with different or modified side chains have been characterized in plant material: they are localized in the inner thylakoid membrane of the chloroplast. So far only plastoquinone-45 (PQ-45) has been identified as an obligatory functional component of the photosynthetic electron transport chain in chloroplasts between photosystem II and photosystem I. A special form (semiquinone) of PQ-45 acts as primary acceptor Q of photosystem II, a large pool of PQ-45 as electron buffer, interconnecting several electron transport chains. The rôle of PQ, in energy conservation (ATP formation) is of particular current interest. Owing to vectorial electron flow across the thylakoid membrane, plastoquinone is thought to be reduced on the outside and plastohydroquinone to be oxidized on the inside of the membrane. This results in a proton translocation across the membrane and a build-up of a proton motive force which drives ATP formation. Old and new plastoquinone antagonists are described and the relevance of inhibitor studies on the rôle of plastoquinone in electron flow and photophosphorylation is discussed. Open questions and current problems of the mechanism of plastoquinone/plastoquinol transport across the membrane - and of proton translocation connected to it - relevant for the mechanism of energy conservation in photosynthesis, are pointed out.

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