scholarly journals Influence of elevated temperature on electron flows in chloroplasts of barley

2020 ◽  
Vol 65 (2) ◽  
pp. 153-162
Author(s):  
N. L. Pshybytko ◽  
T. S. Bachyshcha ◽  
L. F. Kabashnikova
Keyword(s):  
Electron Transport Chain ◽  
Elevated Temperatures ◽  
Electron Flux ◽  
Heat Exposure ◽  
Photosynthetic Apparatus ◽  
Thylakoid Membranes ◽  
Cyclic Electron Transport ◽  
Transport Chain ◽  
Pam Fluorescence ◽  
Electron Carriers

The efficiency of electron carriers in thylakoid membranes untreated and exposed to heat 7-day-old barley seedlings was evaluated with PAM fluorescence. Darkness–light transitional states in chloroplasts after heat exposure are studied. Thermoinduced changes in linear and cyclic electron transport chain of chloroplasts are revealed. The activation of NADPH-dependent electron flux after exposure to elevated temperatures is shown. We assumed that ΔрН of thylakoid membranes employed the regulatory role in the distribution of electron flows and the adaptation of the photosynthetic apparatus to stressful effects.

Mechanism of action of anions on the electron transport chain in thylakoid membranes of higher plants

2011 ◽  
Vol 43 (2) ◽  
pp. 195-202 ◽  
Author(s):  
Pooja Singh-Rawal ◽  
Ottó Zsiros ◽  
Sudhakar Bharti ◽  
Győző Garab ◽  
Anjana Jajoo
Keyword(s):  
Electron Transport ◽  
Mechanism Of Action ◽  
Electron Transport Chain ◽  
Higher Plants ◽  
Thylakoid Membranes ◽  
Transport Chain

scholarly journals Oxygen and ROS in Photosynthesis

Plants ◽  
2020 ◽  
Vol 9 (1) ◽  
pp. 91 ◽  
Author(s):  
Sergey Khorobrykh ◽  
Vesa Havurinne ◽  
Heta Mattila ◽  
Esa Tyystjärvi
Keyword(s):  
Electron Transport Chain ◽  
Photosynthetic Apparatus ◽  
Photosynthetic Electron Transport ◽  
Oxygen Species ◽  
Ros Scavenging ◽  
Respiratory Pathway ◽  
Photosynthetic Organisms ◽  
Photosynthetic Electron Transport Chain ◽  
Transport Chain ◽  
Regulatory Functions

Oxygen is a natural acceptor of electrons in the respiratory pathway of aerobic organisms and in many other biochemical reactions. Aerobic metabolism is always associated with the formation of reactive oxygen species (ROS). ROS may damage biomolecules but are also involved in regulatory functions of photosynthetic organisms. This review presents the main properties of ROS, the formation of ROS in the photosynthetic electron transport chain and in the stroma of chloroplasts, and ROS scavenging systems of thylakoid membrane and stroma. Effects of ROS on the photosynthetic apparatus and their roles in redox signaling are discussed.

Inhibition and Uncoupling of Photosynthetic Electron Transport by Diterpene Lactone Amide Derivatives

2008 ◽  
Vol 63 (3-4) ◽  
pp. 251-259 ◽  
Author(s):  
Pedro A. Castelo-Branco ◽  
Flávio J. L. dos Santos ◽  
Mayura M. M. Rubinger ◽  
Dalton L. Ferreira-Alves ◽  
Dorila Piló -Veloso ◽  
...  
Keyword(s):  
Electron Transport ◽  
Electron Transport Chain ◽  
Electron Flow ◽  
Photosynthetic Electron Transport ◽  
Acceptor Site ◽  
Enzyme Complex ◽  
Cyclic Electron Transport ◽  
Fluorescence Kinetics ◽  
Transport Chain ◽  
Amide Derivatives

Nine diterpene lactone amide derivatives 1-9 were synthesized from 6-oxovouacapan- 7β,17β-lactone, which was obtained from 6α,7β-dihydroxyvouacapan-17β-oic acid isolated from Pterodon polygalaeflorus Benth., and tested for their activity on photosynthetic electron transport. Amide derivatives 3-5 behaved as electron transport chain inhibitors; they inhibited the photophosphorylation and uncoupled non-cyclic electron transport from water to methylviologen (MV). Furthermore, 4 and 5 enhanced the basal electron rate acting as uncouplers. Compound 6 behaved as an uncoupler; it enhanced the light-activated Mg2+-ATPase and basal electron flow, without affecting the uncoupled non-cyclic electron transport. Compounds 1-2 and 7-9 were less active or inactive. Compounds 3-5 did not affect photosystem I (PSI); they inhibited photosystem II (PSII) from water to 2,6-dichlorophenol indophenol (DCPIP). Compound 4 inhibited PSII from water to silicomolybdate (SiMo), but it had no effect on the reaction from diphenylcarbazide (DPC) to DCPIP indicating that its inhibition site was at the water splitting enzyme complex (OEC). Compounds 3 and 5 inhibited PSII from water to DCPIP without any effect from water to SiMo, therefore they inhibited the acceptor site of PSII. Chlorophyll a fluorescence kinetics confirmed the behaviour of 3-5

scholarly journals Alternative splicing of coq-2 controls the levels of rhodoquinone in animals

eLife ◽  
2020 ◽  
Vol 9 ◽  
Author(s):  
June H Tan ◽  
Margot Lautens ◽  
Laura Romanelli-Cedrez ◽  
Jianbin Wang ◽  
Michael R Schertzberg ◽  
...  
Keyword(s):  
Alternative Splicing ◽  
Caenorhabditis Elegans ◽  
Electron Transport ◽  
Electron Transport Chain ◽  
Substrate Selection ◽  
Anaerobic Conditions ◽  
Parasitic Helminths ◽  
Transport Chain ◽  
Splice Forms ◽  
Electron Carriers

Parasitic helminths use two benzoquinones as electron carriers in the electron transport chain. In normoxia, they use ubiquinone (UQ), but in anaerobic conditions inside the host, they require rhodoquinone (RQ) and greatly increase RQ levels. We previously showed the switch from UQ to RQ synthesis is driven by a change of substrates by the polyprenyltransferase COQ-2 (Del Borrello et al., 2019; Roberts Buceta et al., 2019); however, the mechanism of substrate selection is not known. Here, we show helminths synthesize two coq-2 splice forms, coq-2a and coq-2e, and the coq-2e-specific exon is only found in species that synthesize RQ. We show that in Caenorhabditis elegans COQ-2e is required for efficient RQ synthesis and survival in cyanide. Importantly, parasites switch from COQ-2a to COQ-2e as they transit into anaerobic environments. We conclude helminths switch from UQ to RQ synthesis principally via changes in the alternative splicing of coq-2.

scholarly journals Improved photosynthetic capacity and photosystem I oxidation via heterologous metabolism engineering in cyanobacteria

2021 ◽  
Vol 118 (11) ◽  
pp. e2021523118
Author(s):  
María Santos-Merino ◽  
Alejandro Torrado ◽  
Geoffry A. Davis ◽  
Annika Röttig ◽  
Thomas S. Bibby ◽  
...  
Keyword(s):  
Cytochrome P450 ◽  
Electron Transport ◽  
Photosystem I ◽  
Metabolic Pathways ◽  
Electron Transport Chain ◽  
Photosynthetic Apparatus ◽  
Photosynthetic Performance ◽  
Cytochrome P450 Activity ◽  
Transport Chain ◽  
Source Sink

Cyanobacteria must prevent imbalances between absorbed light energy (source) and the metabolic capacity (sink) to utilize it to protect their photosynthetic apparatus against damage. A number of photoprotective mechanisms assist in dissipating excess absorbed energy, including respiratory terminal oxidases and flavodiiron proteins, but inherently reduce photosynthetic efficiency. Recently, it has been hypothesized that some engineered metabolic pathways may improve photosynthetic performance by correcting source/sink imbalances. In the context of this subject, we explored the interconnectivity between endogenous electron valves, and the activation of one or more heterologous metabolic sinks. We coexpressed two heterologous metabolic pathways that have been previously shown to positively impact photosynthetic activity in cyanobacteria, a sucrose production pathway (consuming ATP and reductant) and a reductant-only consuming cytochrome P450. Sucrose export was associated with improved quantum yield of phtotosystem II (PSII) and enhanced electron transport chain flux, especially at lower illumination levels, while cytochrome P450 activity led to photosynthetic enhancements primarily observed under high light. Moreover, coexpression of these two heterologous sinks showed additive impacts on photosynthesis, indicating that neither sink alone was capable of utilizing the full “overcapacity” of the electron transport chain. We find that heterologous sinks may partially compensate for the loss of photosystem I (PSI) oxidizing mechanisms even under rapid illumination changes, although this compensation is incomplete. Our results provide support for the theory that heterologous metabolism can act as a photosynthetic sink and exhibit some overlapping functionality with photoprotective mechanisms, while potentially conserving energy within useful metabolic products that might otherwise be “lost.”

scholarly journals Clustering as a Means To Control Nitrate Respiration Efficiency and Toxicity in Escherichia coli

mBio ◽  
2019 ◽  
Vol 10 (5) ◽  
Author(s):  
Suzy Bulot ◽  
Stéphane Audebert ◽  
Laetitia Pieulle ◽  
Farida Seduk ◽  
Emilie Baudelet ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Electron Transport ◽  
Nitrate Reductase ◽  
Electron Transport Chain ◽  
Electron Flux ◽  
Redox Activity ◽  
Nitrate Respiration ◽  
Multiprotein Complex ◽  
Gut Colonization ◽  
Transport Chain

ABSTRACT Respiration is a fundamental process that has to optimally respond to metabolic demand and environmental changes. We previously showed that nitrate respiration, crucial for gut colonization by enterobacteria, is controlled by polar clustering of the nitrate reductase increasing the electron flux through the complex. Here, we show that the formate dehydrogenase electron-donating complex, FdnGHI, also clusters at the cell poles under nitrate-respiring conditions. Its proximity to the nitrate reductase complex was confirmed by its identification in the interactome of the latter, which appears to be specific to the nitrate-respiring condition. Interestingly, we have identified a multiprotein complex dedicated to handle nitric oxide resulting from the enhanced activity of the electron transport chain terminated by nitrate reductase. We demonstrated that the cytoplasmic NADH-dependent nitrite reductase NirBD and the hybrid cluster protein Hcp are key contributors to regulation of the nitric oxide level during nitrate respiration. Thus, gathering of actors involved in respiration and NO homeostasis seems to be critical to balancing maximization of electron flux and the resulting toxicity. IMPORTANCE Most bacteria rely on the redox activity of respiratory complexes embedded in the cytoplasmic membrane to gain energy in the form of ATP and of an electrochemical gradient established across the membrane. Nevertheless, production of harmful and toxic nitric oxide by actively growing bacteria as either an intermediate or side-product of nitrate respiration challenges how homeostasis control is exerted. Here, we show that components of the nitrate electron transport chain are clustered, likely influencing the kinetics of the process. Nitric oxide production from this respiratory chain is controlled and handled through a multiprotein complex, including detoxifying systems. These findings point to an essential role of compartmentalization of respiratory components in bacterial cell growth.

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