scholarly journals Real-time monitoring of subcellular H2O2 distribution in Chlamydomonas reinhardtii

2020 ◽  
Author(s):  
Justus Niemeyer ◽  
David Scheuring ◽  
Julian Oestreicher ◽  
Bruce Morgan ◽  
Michael Schroda
Keyword(s):  
Electron Transport ◽  
Chlamydomonas Reinhardtii ◽  
Plant Cells ◽  
Mitochondrial Matrix ◽  
Linear Electron ◽  
Physiological Conditions ◽  
Modular Cloning ◽  
Stressed Cells ◽  
Chloroplast Stroma ◽  
Scavenging Enzymes

AbstractH2O2 has been recognized as an important signaling molecule in plants. We sought to establish a genetically encoded, fluorescent H2O2 sensor that allows H2O2 monitoring in all major subcompartments of a Chlamydomonas cell. To this end we engineered the hypersensitive H2O2 sensor, roGFP2-Tsa2ΔCR, as a genetic part for the Chlamydomonas Modular Cloning toolbox. Using previously generated parts, together with new ones, we constructed modules and devices that target the sensor to the cytosol, nucleus, mitochondrial matrix, chloroplast stroma, thylakoid lumen, and ER. The sensor was functional in all compartments, except for the ER where it was fully oxidized. Employing our novel sensors, we show that H2O2 produced by photosynthetic linear electron transport (PET) in the stroma leaks into the cytosol but only reaches other subcellular compartments if produced under non-physiological conditions. Our results thus imply the establishment of steep intracellular H2O2 gradients under normal physiological conditions and suggest that the cytosolic complement of H2O2 scavenging enzymes effectively limits H2O2 diffusion. Furthermore, in heat stressed cells, we show that cytosolic H2O2 levels closely mirror temperature up- and downshifts and are independent from PET. We anticipate that these sensors will greatly facilitate future investigations into H2O2 biology in algal and plant cells.

scholarly journals Cyclic electron flow in Chlamydomonas reinhardtii

2017 ◽  
Author(s):  
W. J. Nawrocki ◽  
B. Bailleul ◽  
P. Cardol ◽  
F. Rappaport ◽  
F.-A. Wollman ◽  
...  
Keyword(s):  
Electron Transport ◽  
Chlamydomonas Reinhardtii ◽  
Electron Flow ◽  
Cyclic Electron Flow ◽  
Maximal Rate ◽  
Linear Electron ◽  
Transport Pathways ◽  
Acceptor Side ◽  
Kinetic Information

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.

scholarly journals The Regulation of Photosynthetic Electron Transport during Nutrient Deprivation in Chlamydomonas reinhardtii

1998 ◽  
Vol 117 (1) ◽  
pp. 129-139 ◽  
Author(s):  
Dennis D. Wykoff ◽  
John P. Davies ◽  
Anastasios Melis ◽  
Arthur R. Grossman
Keyword(s):  
Electron Transport ◽  
Chlamydomonas Reinhardtii ◽  
Photosynthetic Electron Transport ◽  
Nutrient Deprivation

The Effect of an Antiserum to Plastocyanin on Various Chloroplast Preparations

1975 ◽  
Vol 30 (3-4) ◽  
pp. 201-212 ◽  
Author(s):  
Georg Schmid ◽  
Alfons Radunz ◽  
Wilhelm Menke
Keyword(s):  
Electron Transport ◽  
Thylakoid Membrane ◽  
Electron Flow ◽  
Linear Electron ◽  
Wild Type ◽  
Lamellar System ◽  
Spinach Chloroplasts ◽  
Monospecific Antiserum ◽  
Cyclic Photophosphorylation ◽  
Aurea Mutant

Abstract A monospecific antiserum to tobacco plastocyanin agglutinates strom a-free sw ellable chloroplasts from wild type tobacco, (Nicotia na tabacum var. John William’s Broadleaf) from the tobacco aurea mutant Su/su2, (Nicotiana tabacum var. Su/su2) from Antirrhinum majus and spinach (Spi-nacia oleracea). In this condition the antiserum inhibits linear photosynthetic electron flow in tobacco and spinach chloroplasts. This inhibition of electron transport as well as the agglutination are not observed if the chloroplasts have been sonicated prior to antiserum addition. This is due to the fact that plastocyanin is removed by ultrasonication. The antiserum stimulates a number of photophosphorylation reactions in tobacco chloroplasts. This stimulation is always larger in the aurea mutant chloroplasts and in chloroplasts from yellow leaf patches of a variegated tobacco mutant (N . tabacum , var. NC95) than in the green type chloroplasts. The stimulation appears to be a consequence of the inhibition of linear electron transport. The antiserum does not affect PMS-mediated cyclic photophosphorylation in tobacco chloroplasts from the wild type whereas the reaction appears stimulated in the tobacco mutant chloroplasts. However, menadione-mediated cyclic photo­ phosphorylation is inhibited upon addition of the antiserum. The same is true for noncyclic photo­ phosphorylation coupled to electron transport in the aerobic system diaminodurene/ascorbate → methylviologen in the presence of N-tetraphenyl-p-phenylenediamine in spinach chloroplasts. If the lamellar system of Antirrhinum and spinach has lost its swellability neither agglutination nor inhibition of electron transport is observed. However, also in this state antibodies to plasto­ cyanin are specifically adsorbed onto the surface of the thylakoid membrane. This state which is characterized by a morphologically well preserved lamellar system is realized in chloroplast prepa­ rations from Antirrhinum and spinach and is termed stroma-freed, chloroplasts. In both states of the molecular structure of the thylakoid membrane, plastocyanin is located in the outer surface of the thylakoid. However, it cannot be excluded that functioning plastocyanin is also located in the interior of the thylakoid membrane.

scholarly journals Precipitation of Inorganic Salts in Mitochondrial Matrix

Membranes ◽  
2020 ◽  
Vol 10 (5) ◽  
pp. 81
Author(s):  
Jerzy J. Jasielec ◽  
Robert Filipek ◽  
Krzysztof Dołowy ◽  
Andrzej Lewenstam
Keyword(s):  
Calcium Concentration ◽  
Mitochondrial Matrix ◽  
Irreversible Damage ◽  
Atp Production ◽  
Physiological Conditions ◽  
Carbonated Apatite ◽  
Constant Ph ◽  
The Matrix ◽  
Magnesium Salts ◽  
Ph Buffer

In the mitochondrial matrix, there are insoluble, osmotically inactive complexes that maintain a constant pH and calcium concentration. In the present paper, we examine the properties of insoluble calcium and magnesium salts, such as phosphates, carbonates and polyphosphates, which might play this role. We find that non-stoichiometric, magnesium-rich carbonated apatite, with very low crystallinity, precipitates in the matrix under physiological conditions. Precipitated salt acts as pH buffer, and, hence, can contribute in maintaining ATP production in ischemic conditions, which delays irreversible damage to heart and brain cells after stroke.

Photoautotrophic Cultured Plant Cells: A Novel System to Survey New Photosynthetic Electron Transport Inhibitors

1991 ◽  
Vol 46 (7-8) ◽  
pp. 563-568 ◽  
Author(s):  
Fumihiko Sato ◽  
Yasuyuki Yamada ◽  
Sang Soo Kwak ◽  
Katsunori Ichinose ◽  
Mitsuhiro Kishida ◽  
...  
Keyword(s):  
Electron Transport ◽  
Cultured Cells ◽  
Plant Cells ◽  
Photosynthetic Electron Transport ◽  
Herbicidal Activity ◽  
Marchantia Polymorpha ◽  
Hill Reaction ◽  
Transport Inhibitors ◽  
Comparison Of The Results ◽  
The Hill

Abstract The responses of photoautotrophic (PA) cultured cells of tobacco (Nicotiana tabacum cv. Samsun NN) and liverwort (Marchantia polymorpha L.) to thirty-eight cyclohexanedione derivatives were surveyed. Each derivative was also tested for inhibitory activity on photosynthetic electron transport (PET), using isolated thylakoids, and herbicidal activity, using seed­ lings and mature plants. Comparison of the results from the different assays showed that the responses of PA cells to each com pound correlated more closely with the responses of seed­ lings and mature plants than did the results of the Hill reaction assays. Our findings suggest that PA cultured cells would be a suitable screening material for identifying potential herbicides with PET-inhibiting activity.

Photoinhibitory Damage to Chloroplasts under Phosphate Deficiency and Alleviation of Deficiency and Damage by Photorespiratory Reactions

1989 ◽  
Vol 44 (5-6) ◽  
pp. 524-536 ◽  
Author(s):  
U. Heber ◽  
J. Viil ◽  
S. Neimanis ◽  
T. Mimura ◽  
K.-J. Dietz
Keyword(s):  
Electron Transport ◽  
Light Intensity ◽  
Oxygen Evolution ◽  
High Light Intensity ◽  
High Light ◽  
Phosphate Deficiency ◽  
Loss Of Function ◽  
Low Light ◽  
Chloroplast Stroma ◽  
Pi Deficiency

Abstract Effects of Pi deficiency on photosynthesis ot isolated spinach chloroplasts were examined. The following observations were made: (1) Chloroplasts isolated in Pi-free media evolved oxygen in the light in the absence of added Pi until acid-extractable Pi in the chloroplasts had decreased to 1 to 2.5 m M . This Pi was unavailable for photophosphorylation as shown by the inability of the chloroplasts to respond by oxygen evolution to the addition of PGA. In the state of Pi-deficiency, stromal ATP to A DP ratios were in the light close to or below ratios observed in the dark. In the presence of 2 mᴍ PGA, addition of 20 μm Pi was insufficient to increase ATP to ADP ratios, but sufficient for appreciable oxygen evolution. (2) More Pi was available for oxygen evolution of phosphate-deficient chloroplasts at low levels of C02 than at high levels. This was due mainly to the suppression of oxygenation of RuBP by high C02 levels which prevented formation of phosphoglycolate and the subsequent release of Pi into the chloroplast stroma. (3) More oxygen was produced by phosphate-deficient chloroplasts at a low light intensity than at a high light intensity. This was due to increased availability of endogenous Pi under low light and to photoinhibition of the chloroplasts by high light. The main product of photosynthesis of phosphate-deficient chloroplasts in the presence of a high bicarbonate concentration was starch, and the main soluble product was PGA. (4) After phosphate-deficient chloroplasts had ceased to evolve oxygen in the light, they be­ came photosensitive. Part of the loss of the capacity for oxygen evolution is attributed to leakage of PGA, but the main reason for loss of function is photoinactivation of electron transport. Both photosystems of the electron transport chain were damaged by light. (5) Protection against photoinactivation was provided by coupled electron transport. Photo­ inactivation of phosphate-deficient chloroplasts was less extensive in the presence of low C02 concentrations which permitted oxygenation of RuBP than at high CO2 concentrations. Electron transport to C02 and other physiological electron acceptors and to the herbicide methylviologen was also protective. However, electron transport to oxygen in the Mehler reaction failed to provide appreciable protection against high light intensities, because oxygen reduction is slow and reactive oxygen species produced in the light contribute to photoinactivation.

The carbonic anhydrase gene families of Chlamydomonas reinhardtii

2005 ◽  
Vol 83 (7) ◽  
pp. 780-795 ◽  
Author(s):  
Mautusi Mitra ◽  
Catherine B Mason ◽  
Ying Xiao ◽  
Ruby A Ynalvez ◽  
Scott M Lato ◽  
...  
Keyword(s):  
Carbonic Anhydrase ◽  
Chlamydomonas Reinhardtii ◽  
Gene Families ◽  
Carbonic Anhydrases ◽  
Photosynthetic Organisms ◽  
Surrounding Environment ◽  
Concentrating Mechanism ◽  
Chloroplast Stroma ◽  
Carbonic Anhydrase Gene

Carbonic anhydrases (CAs) are zinc-containing metalloenzymes that catalyze the reversible interconversion of CO2 and HCO3–. Aquatic photosynthetic organisms have evolved different forms of CO2-concentrating mechanisms to aid Rubisco in capturing CO2 from the surrounding environment. One aspect of all CO2-concentrating mechanisms is the critical roles played by various specially localized extracellular and intracellular CAs. There are three evolutionarily unrelated CA families designated α-, β-, and γ-CA. In the green alga, Chlamydomonas reinhardtii Dangeard, eight CAs have now been identified, including three α-CAs and five β-CAs. In addition, C. reinhardtii has another CA-like gene, Glp1 that is similar to known γ-CAs. To characterize these different CA isoforms, some of the CA genes have been overexpressed to determine whether the proteins have CA activity and to generate antibodies for in vivo immunolocalization. The CA proteins Cah3, Cah6, and Cah8, and the γ-CA-like protein, Glp1, have been overexpressed. Cah3, Cah6, and Cah8 have CA activity, but Glp1 does not. At least two of these proteins, Cah3 and Cah6, are localized to the chloroplast. Using immunolocalization and sequence analyses, we have determined that Cah6 is located to the chloroplast stroma and confirmed that Cah3 is localized to the chloroplast thylakoid lumen. Activity assays show that Cah3 is 100 times more sensitive to sulfonamides than Cah6. We present a model on how these two chloroplast CAs might participate in the CO2-concentrating mechanism of C. reinhardtii. Key words: carbonic anhydrase, CO2-concentrating mechanism, Chlamydomonas, immunolocalization.

scholarly journals The Physiological Functionality of PGR5/PGRL1-Dependent Cyclic Electron Transport in Sustaining Photosynthesis

2021 ◽  
Vol 12 ◽  
Author(s):  
Mingzhu Ma ◽  
Yifei Liu ◽  
Chunming Bai ◽  
Yunhong Yang ◽  
Zhiyu Sun ◽  
...  
Keyword(s):  
Electron Transport ◽  
Photosystem Ii ◽  
Nadh Dehydrogenase ◽  
Extreme Weather Events ◽  
Cyclic Electron Transport ◽  
Linear Electron ◽  
Transport Pathway ◽  
Biochemical Processes ◽  
Weather Events ◽  
Electron Transport Pathway

The cyclic electron transport (CET), after the linear electron transport (LET), is another important electron transport pathway during the light reactions of photosynthesis. The proton gradient regulation 5 (PGR5)/PRG5-like photosynthetic phenotype 1 (PGRL1) and the NADH dehydrogenase-like complex pathways are linked to the CET. Recently, the regulation of CET around photosystem I (PSI) has been recognized as crucial for photosynthesis and plant growth. Here, we summarized the main biochemical processes of the PGR5/PGRL1-dependent CET pathway and its physiological significance in protecting the photosystem II and PSI, ATP/NADPH ratio maintenance, and regulating the transitions between LET and CET in order to optimize photosynthesis when encountering unfavorable conditions. A better understanding of the PGR5/PGRL1-mediated CET during photosynthesis might provide novel strategies for improving crop yield in a world facing more extreme weather events with multiple stresses affecting the plants.

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