scholarly journals Mitochondrial AOX Supports Redox Balance of Photosynthetic Electron Transport, Primary Metabolite Balance, and Growth in Arabidopsis thaliana under High Light

2019 ◽  
Vol 20 (12) ◽  
pp. 3067 ◽  
Author(s):  
Zhenxiang Jiang ◽  
Chihiro K. A. Watanabe ◽  
Atsuko Miyagi ◽  
Maki Kawai-Yamada ◽  
Ichiro Terashima ◽  
...  
Keyword(s):  
Arabidopsis Thaliana ◽  
Electron Transport ◽  
Calvin Cycle ◽  
Photosynthetic Electron Transport ◽  
Tca Cycle ◽  
Mitochondrial Respiratory Chain ◽  
Redox Balance ◽  
High Light ◽  
Primary Metabolite ◽  
Physiological Importance

When leaves receive excess light energy, excess reductants accumulate in chloroplasts. It is suggested that some of the reductants are oxidized by the mitochondrial respiratory chain. Alternative oxidase (AOX), a non-energy conserving terminal oxidase, was upregulated in the photosynthetic mutant of Arabidopsis thaliana, pgr5, which accumulated reductants in chloroplast stroma. AOX is suggested to have an important role in dissipating reductants under high light (HL) conditions, but its physiological importance and underlying mechanisms are not yet known. Here, we compared wild-type (WT), pgr5, and a double mutant of AOX1a-knockout plant (aox1a) and pgr5 (aox1a/pgr5) grown under high- and low-light conditions, and conducted physiological analyses. The net assimilation rate (NAR) was lower in aox1a/pgr5 than that in the other genotypes at the early growth stage, while the leaf area ratio was higher in aox1a/pgr5. We assessed detailed mechanisms in relation to NAR. In aox1a/pgr5, photosystem II parameters decreased under HL, whereas respiratory O2 uptake rates increased. Some intermediates in the tricarboxylic acid (TCA) cycle and Calvin cycle decreased in aox1a/pgr5, whereas γ-aminobutyric acid (GABA) and N-rich amino acids increased in aox1a/pgr5. Under HL, AOX may have an important role in dissipating excess reductants to prevent the reduction of photosynthetic electron transport and imbalance in primary metabolite levels.

scholarly journals The Mitochondrial Respiratory Chain Maintains the Photosynthetic Electron Flow in Arabidopsis thaliana Leaves under High-Light Stress

2019 ◽  
Vol 61 (2) ◽  
pp. 283-295 ◽  
Author(s):  
Shoya Yamada ◽  
Hiroshi Ozaki ◽  
Ko Noguchi
Keyword(s):  
Arabidopsis Thaliana ◽  
Electron Transport ◽  
Respiratory Chain ◽  
Rate Constants ◽  
Electron Flow ◽  
Light Stress ◽  
Photosynthetic Electron Transport ◽  
Mitochondrial Respiratory Chain ◽  
High Light ◽  
Complex Iii

Abstract The plant respiratory chain includes the ATP-coupling cytochrome pathway (CP) and ATP-uncoupling alternative oxidase (AOX). Under high-light (HL) conditions, plants experience photoinhibition, leading to a damaged photosystem II (PSII). The respiratory chain is considered to affect PSII maintenance and photosynthetic electron transport under HL conditions. However, the underlying details remain unclear. In this study, we investigated the respiratory chain functions related to PSII maintenance and photosynthetic electron transport in plants exposed to HL stress. We measured the HL-induced decrease in the maximum quantum yield of PSII in the leaves of wild-type and AOX1a-knockout (aox1a) Arabidopsis thaliana plants in which CP was partially inhibited by a complex-III inhibitor. We also calculated PSII photodamage and repair rate constants. Both rate constants changed when CP was partially inhibited in aox1a plants, suggesting that the respiratory chain is related to both processes. Before HL stress, photosynthetic linear electron flow (LEF) decreased when CP was partially inhibited. After HL stress, aox1a in the presence of the CP inhibitor showed significantly decreased rates of LEF. The electron flow downstream from PSII and on the donor side of photosystem I may have been suppressed. The function of respiratory chain is required to maintain the optimal LEF as well as PSII maintenance especially under the HL stress.

Influence of Sublethal Concentrations of Herbicides and Growth Regulators on Mouseearcress (Arabidopsis thaliana) Progeny

Weed Science ◽  
1985 ◽  
Vol 33 (4) ◽  
pp. 430-434 ◽  
Author(s):  
Ron Henzell ◽  
John Phillips ◽  
Peter Diggle
Keyword(s):  
Arabidopsis Thaliana ◽  
Electron Transport ◽  
Plant Growth ◽  
Growth Regulators ◽  
Growth And Development ◽  
Auxin Transport ◽  
Photosynthetic Electron Transport ◽  
Persistent Effect ◽  
Transport Inhibitors ◽  
Sublethal Concentrations

The influence of sublethal levels of a number of herbicides and plant growth regulators on the germinability of the seeds and the growth and development of seedlings of mouseearcress [Arabidopsis thaliana(L.) Heynh. ♯ ARBTH] was determined. Only 7 of the 22 chemicals tested had a persistent effect on progeny. Amitrole (3-amino-s-triazole) was one of the most effective compounds. It caused a characteristic bleaching only in shoot tips and pods in parent plants and appeared to act directly on the progeny by accumulation in the seed. Two auxin transport inhibitors, TIBA (2,3,5-triiodobenzoic acid) and CPII (5-O-carboxyphenyl-3-phenylisoxazole), and four of the six photosynthetic electron transport inhibitors included in the study also affected progeny. They appeared to act indirectly by interfering with seed development.

scholarly journals Distinct Redox Behaviors of Chloroplast Thiol Enzymes and their Relationships with Photosynthetic Electron Transport in Arabidopsis thaliana

2014 ◽  
Vol 55 (8) ◽  
pp. 1415-1425 ◽  
Author(s):  
Keisuke Yoshida ◽  
Yuta Matsuoka ◽  
Satoshi Hara ◽  
Hiroki Konno ◽  
Toru Hisabori
Keyword(s):  
Arabidopsis Thaliana ◽  
Electron Transport ◽  
Photosynthetic Electron Transport

scholarly journals Effects of red and blue light on leaf anatomy, CO2 assimilation, and the photosynthetic electron transport capacity of sweet pepper (Capsicum annuum L.) seedlings

2020 ◽  
Author(s):  
Yan Li ◽  
Guofeng Xin ◽  
Chang Liu ◽  
Qinghua Shi ◽  
Fengjuan Yang ◽  
...  
Keyword(s):  
Electron Transport ◽  
Capsicum Annuum ◽  
Leaf Anatomy ◽  
Calvin Cycle ◽  
Biomass Accumulation ◽  
Photosynthetic Electron Transport ◽  
Sweet Pepper ◽  
Transport Capacity ◽  
Ribulose 1 ◽  
Electron Transportation

Abstract Background: The red (R) and blue (B) light wavelengths are known to influence many plant physiological processes during growth and development, particularly photosynthesis. To understand how R and B light influences plant photomorphogenesis and photosynthesis, we investigated changes in leaf anatomy and stomatal traits, chlorophyll fluorescence and photosynthetic parameters, and ribulose-1, 5-bisphosphate carboxylase/oxygenase (Rubisco) and Calvin cycle-related enzymes expression and their activities in sweet pepper (Capsicum annuum L.) seedlings exposed to four light qualities: monochromatic white (W, control), R, B, and mixed R and B (RB) light with the same photosynthetic photon flux density (PPFD) of 300 μmol/m2·s. Results: The results revealed that seedlings grown under R light had lower biomass accumulation, CO2 assimilation, and photosystem II (PSII) electron transportation compared to plants grown under the other treatments. These changes are probably due to inactivation of the photosystem (PS). Biomass accumulation and CO2 assimilation were significantly enriched in B- and RB-grown plants, especially the latter treatment. Their leaves were also thicker, and stomatal conductance, photosynthetic electron transport capacity, and the photosynthetic rate were enhanced. The up-regulation of the expression and activities of Rubisco, fructose-1, 6-bisphosphatase (FBPase), and fructose-1, 6-bisphosphate aldolase (FBA), which are involved in the Calvin cycle and are probably the main enzymatic factors contributing to RuBP (ribulose-1, 5-bisphosphate) synthesis, also increased. Conclusions: Mixed R and B light altered plant photomorphogenesis and photosynthesis, mainly through its effects on leaf anatomy, photosynthetic electron transportation, and the expression and activities of key Calvin cycle enzymes.

The drug ornidazole inhibits photosynthesis in a different mechanism described for protozoa and anaerobic bacteria

2016 ◽  
Vol 473 (23) ◽  
pp. 4413-4426 ◽  
Author(s):  
Yehouda Marcus ◽  
Noam Tal ◽  
Mordechai Ronen ◽  
Raanan Carmieli ◽  
Michael Gurevitz
Keyword(s):  
Electron Transport ◽  
Nitro Group ◽  
Bacterial Infections ◽  
Electron Tunneling ◽  
Anaerobic Bacteria ◽  
Calvin Cycle ◽  
Photosynthetic Electron Transport ◽  
Iron Sulfur Cluster ◽  
Efficient Inhibitor ◽  
Oxygen Photoreduction

Ornidazole of the 5-nitroimidazole drug family is used to treat protozoan and anaerobic bacterial infections via a mechanism that involves preactivation by reduction of the nitro group, and production of toxic derivatives and radicals. Metronidazole, another drug family member, has been suggested to affect photosynthesis by draining electrons from the electron carrier ferredoxin, thus inhibiting NADP+ reduction and stimulating radical and peroxide production. Here we show, however, that ornidazole inhibits photosynthesis via a different mechanism. While having a minute effect on the photosynthetic electron transport and oxygen photoreduction, ornidazole hinders the activity of two Calvin cycle enzymes, triose-phosphate isomerase (TPI) and glyceraldehyde-3-phosphate dehydrogenase (GAPDH). Modeling of ornidazole's interaction with ferredoxin of the protozoan Trichomonas suggests efficient electron tunneling from the iron–sulfur cluster to the nitro group of the drug. A similar docking site of ornidazole at the plant-type ferredoxin does not exist, and the best simulated alternative does not support such efficient tunneling. Notably, TPI was inhibited by ornidazole in the dark or when electron transport was blocked by dichloromethyl diphenylurea, indicating that this inhibition was unrelated to the electron transport machinery. Although TPI and GAPDH isoenzymes are involved in glycolysis and gluconeogenesis, ornidazole's effect on respiration of photoautotrophs is moderate, thus raising its value as an efficient inhibitor of photosynthesis. The scarcity of Calvin cycle inhibitors capable of penetrating cell membranes emphasizes on the value of ornidazole for studying the regulation of this cycle.

scholarly journals Photosynthetic signalling during high light stress and recovery: targets and dynamics

2020 ◽  
Vol 375 (1801) ◽  
pp. 20190406 ◽  
Author(s):  
Peter J. Gollan ◽  
Eva-Mari Aro
Keyword(s):  
Gene Expression ◽  
Electron Transport ◽  
Redox Homeostasis ◽  
Light Stress ◽  
Photosynthetic Apparatus ◽  
Photosynthetic Electron Transport ◽  
High Light ◽  
Abiotic Stress Response ◽  
High Light Stress ◽  
Retrograde Signalling

The photosynthetic apparatus is one of the major primary sensors of the plant's external environment. Changes in environmental conditions affect the balance between harvested light energy and the capacity to deal with excited electrons in the stroma, which alters the redox homeostasis of the photosynthetic electron transport chain. Disturbances to redox balance activate photosynthetic regulation mechanisms and trigger signalling cascades that can modify the transcription of nuclear genes. H 2 O 2 and oxylipins have been identified as especially prominent regulators of gene expression in response to excess light stress. This paper explores the hypothesis that photosynthetic imbalance triggers specific signals that target discrete gene profiles and biological processes. Analysis of the major retrograde signalling pathways engaged during high light stress and recovery demonstrates both specificity and overlap in gene targets. This work reveals distinct, time-resolved profiles of gene expression that suggest a regulatory interaction between rapidly activated abiotic stress response and induction of secondary metabolism and detoxification processes during recovery. The findings of this study show that photosynthetic electron transport provides a finely tuned sensor for detecting and responding to the environment through chloroplast retrograde signalling. This article is part of the theme issue ‘Retrograde signalling from endosymbiotic organelles’

Exposure of high-light-grown cultures of Chlorella vulgaris to darkness inhibits the relaxation of excitation pressure: uncoupling of the redox state of the photosynthetic electron transport chain and phenotypic plasticity

Botany ◽  
2017 ◽  
Vol 95 (12) ◽  
pp. 1125-1140 ◽  
Author(s):  
Lauren Hollis ◽  
Norman P.A. Hüner
Keyword(s):  
Electron Transport ◽  
Chlorella Vulgaris ◽  
Electron Transport Chain ◽  
Redox State ◽  
Light Harvesting ◽  
Photosynthetic Electron Transport ◽  
High Light ◽  
Photon Flux ◽  
Photosynthetic Electron Transport Chain ◽  
Transport Chain

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.

The PedR transcriptional regulator interacts with thioredoxin to connect photosynthesis with gene expression in cyanobacteria

2010 ◽  
Vol 431 (1) ◽  
pp. 135-140 ◽  
Author(s):  
Mayumi Horiuchi ◽  
Kinu Nakamura ◽  
Kouji Kojima ◽  
Yoshitaka Nishiyama ◽  
Wakako Hatakeyama ◽  
...  
Keyword(s):  
Electron Transport ◽  
Conformational Change ◽  
Photosynthetic Electron Transport ◽  
Transcript Level ◽  
High Light ◽  
Light Conditions ◽  
Transport Chain ◽  
Acclimation Response ◽  
Vitro Analysis

The redox state of the photosynthetic electron transport chain acts as a critical sensing mechanism by regulating the transcription of key genes involved in the acclimation response to a change in the environment. In the present study we show that the small LuxR-type regulator PedR interacts with Trx (thioredoxin) to achieve photosynthetic electron-transport-dependent transcriptional regulation in the cyanobacterium Synechocystis sp. PCC 6803. TrxM, an isoform of Trx, was isolated as an interacting factor of PedR by pull-down assays. In vitro analysis revealed that the intermolecular disulfide bond formed between Cys80 residues of the PedR homodimer was reduced by both TrxM and TrxX. It has been shown previously that, although PedR is active under low-light conditions, it becomes transiently inactivated following a shift to high-light conditions, with a concomitant conformational change [Nakamura and Hihara (2006) J. Biol. Chem. 281, 36758–36766]. In the present study, we found that the conformational change of PedR and the change in the transcript level of its target gene were minimal when mutants of Synechocystis that lack ferredoxin–Trx reductase or NADPH–Trx reductase were exposed to high levels of light. These results indicate that the reduction of PedR by Trx causes transient inactivation of PedR upon the shift of cyanobacterial cells to high-light conditions.

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