Regulation of electron-transport pathways in cells of Chlamydomonas reinhardtii under stress conditions

AbstractCyclic electron flow (CEF), one of the major alternative electron transport pathways to the primary linear electron flow (LEF) in chloroplasts has been discovered in the middle of the last century. It is defined as a return of the reductants from the acceptor side of the Photosystem I (PSI) to the pool of its donors via the cytochrome b6f, and has proven essential for photosynthesis. However, despite many efforts aimed at its characterisation, the pathway and regulation of CEF remain equivocal, and its physiological significance remains to be properly defined. Here we use novel spectroscopic approaches to measure CEF in transitory conditions in the green alga Chlamydomonas reinhardtii. We show that CEF operates at the same maximal rate regardless of the oxygen concentration, and that the latter influences LEF, rather than CEF in vivo, which questions the recent hypotheses about the CEF supercomplex formation. We further reveal that the pathways proposed for CEF in the literature are inconsistent with the kinetic information provided by our measurements. We finally provide cues on the regulation of CEF by light.

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FORMATION OF ATYPICAL TUBULIN STRUCTURES IN CELLS OF PLANTS FROM SOLANA-CEAE FAMILY IN RESPONSE TO ABIOTIC STRESS CONDITIONS

Izvestiâ Timirâzevskoj selʹskohozâjstvennoj akademii ◽

10.26897/0021-342x-2017-1-17-29 ◽

2017 ◽

pp. 17-29 ◽

Cited By ~ 1

Author(s):

E.N. BARANOVA ◽

◽

I.A. CHABAN ◽

L.R. BOGOUTDINOVA ◽

L.V. KURENINA ◽

...

Keyword(s):

Abiotic Stress ◽

Stress Conditions ◽

In Cells

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Structures of nitroaromatic compounds induce Shewanella oneidensis MR-1 to adopt different electron transport pathways to reduce the contaminants

Journal of Hazardous Materials ◽

10.1016/j.jhazmat.2019.121495 ◽

2020 ◽

Vol 384 ◽

pp. 121495 ◽

Cited By ~ 2

Author(s):

Hefei Wang ◽

He-Ping Zhao ◽

Lizhong Zhu

Keyword(s):

Electron Transport ◽

Shewanella Oneidensis ◽

Nitroaromatic Compounds ◽

Transport Pathways

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Endogenous Fluctuations of DNA Topology in the Chloroplast of Chlamydomonas reinhardtii

Molecular and Cellular Biology ◽

10.1128/mcb.18.12.7235 ◽

1998 ◽

Vol 18 (12) ◽

pp. 7235-7242 ◽

Cited By ~ 42

Author(s):

Maria L. Salvador ◽

Uwe Klein ◽

Lawrence Bogorad

Keyword(s):

Chlamydomonas Reinhardtii ◽

Chloroplast Genome ◽

Continuous Light ◽

Dna Supercoiling ◽

Dna Topology ◽

Chloroplast Gene ◽

Chloroplast Gene Expression ◽

Endogenous Fluctuations ◽

Unicellular Green Alga ◽

In Cells

ABSTRACT DNA supercoiling in the chloroplast of the unicellular green algaChlamydomonas reinhardtii was found to change with a diurnal rhythm in cells growing in alternating 12-h dark–12-h light periods. Highest and lowest DNA superhelicities occurred at the beginning and towards the end of the 12-h light periods, respectively. The fluctuations in DNA supercoiling occurred concurrently and in the same direction in two separate parts of the chloroplast genome, one containing the genes psaB, rbcL, andatpA and the other containing the atpB gene. Fluctuations were not confined to transcribed DNA regions, indicating simultaneous changes in DNA conformation all over the chloroplast genome. Because the diurnal fluctuations persisted in cells kept in continuous light, DNA supercoiling is judged to be under endogenous control. The endogenous fluctuations in chloroplast DNA topology correlated tightly with the endogenous fluctuations of overall chloroplast gene transcription and with those of the pool sizes of most chloroplast transcripts analyzed. This result suggests that DNA superhelical changes have a role in the regulation of chloroplast gene expression in Chlamydomonas.

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Electron transport pathways for the oxidation of endogenous substrate(s) in Acidithiobacillus ferrooxidans

Canadian Journal of Microbiology ◽

10.1139/w05-128 ◽

2006 ◽

Vol 52 (4) ◽

pp. 317-327 ◽

Cited By ~ 4

Author(s):

Yongqiang Chen ◽

Isamu Suzuki

Keyword(s):

Electron Transport ◽

Electron Acceptor ◽

Acidithiobacillus Ferrooxidans ◽

Complex I ◽

Iron Chelators ◽

Endogenous Respiration ◽

Sugar Alcohols ◽

Transport Pathways ◽

Endogenous Substrate ◽

Transport Inhibitors

Oxidation of endogenous substrate(s) of Acidithiobacillus ferrooxidans with O2 or Fe3+ as electron acceptor was studied in the presence of uncouplers and electron transport inhibitors. Endogenous substrate was oxidized with a respiratory quotient (CO2 produced/O2 consumed) of 1.0, indicating its carbohydrate nature. The oxidation was inhibited by complex I inhibitors (rotenone, amytal, and piericidin A) only partially, but piericidin A inhibited the oxidation with Fe3+ nearly completely. The oxidation was stimulated by uncouplers, and the stimulated activity was more sensitive to inhibition by complex I inhibitors. HQNO (2-heptyl-4-hydroxyquinoline N-oxide) also stimulated the oxidation, and the stimulated respiration was more sensitive to KCN inhibition than uncoupler stimulated respiration. Fructose, among 20 sugars and sugar alcohols including glucose and mannose, was oxidized with a CO2/O2 ratio of 1.0 by the organism. Iron chelators in general stimulated endogenous respiration, but some of them reduced Fe3+ chemically, introducing complications. The results are discussed in view of a branched electron transport system of the organism and its possible control.Key words: Acidithiobacillus ferrooxidans, endogenous respiration, uncouplers, electron transport.

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