
Szilvia Z TothBiological Research Centre Szeged · Institute of Plant Biology
Szilvia Z Toth
PhD
About
77
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Introduction
Additional affiliations
December 2014 - present
September 2012 - September 2014
Max Planck Institute of Molecular Plant Biology
Position
- Fellow
January 2007 - August 2012
Publications
Publications (77)
Ascorbate is a multifunctional metabolite in plants. It is essential for growth control, involving cell division and cell wall synthesis and is also involved in redox signaling, in the modulation of gene expression and regulation of enzymatic activities. Ascorbate also fulfills crucial roles in scavenging reactive oxygen species, both enzymatically...
Previously, we showed that ascorbate (Asc), by donating electrons to photosystem II (PSII), supports a sustained electron transport activity in leaves in which the oxygen-evolving complexes were inactivated with a heat pulse (49°C, 40 s). Here, by using wild-type, Asc-overproducing, and -deficient Arabidopsis (Arabidopsis thaliana) mutants (miox4 a...
Previously, we showed that in barley (Hordeum vulgare) leaves with heat-inactivated oxygen-evolving complexes, photosystem II (PSII) has access to a large pool of alternative electron donors. Based on in vitro data, we proposed that this donor was ascorbate, yet this hypothesis has not been substantiated in vivo. In this paper, with the aid of chlo...
In nature, environmental conditions strongly fluctuate, frequently subjecting plants to periods of immediate photo-oxidative stress. The small molecule ascorbate allows plants to cope with such stress conditions. Ascorbate scavenges reactive oxygen species and enables the rapid and full induction of photoprotective non-photochemical quenching (NPQ)...
Ascorbate (Asc), commonly known as vitamin C, is a vital molecule for plant growth, development, and stress resilience. It is also known to play a crucial role in various physiological processes, including photosynthesis, cell division, and differentiation. This article thoroughly explores the processes governing the metabolism of Asc in plants and...
Ascorbate (Asc) is an important antioxidant that also participates in various biological processes in plants such as hormone metabolism, stress response and signaling pathways. Asc is also a vital vitamin for human health and enriching its content through biofortification is a desirable objective. Therefore, reliable in situ methods for assessing A...
Unlike an equilibrium gas, the distribution of active particles can be very sensitive to what happens at the boundaries of their container. Experiments and simulations have previously highlighted the possibility of exploiting this behavior for the geometric control of active particles, although a general theoretical framework is lacking. Here we pr...
Ascorbate is a major plant metabolite that plays crucial roles in various processes, from reactive oxygen scavenging to epigenetic regulation. However, to what extent and how ascorbate modulates metabolism is largely unknown. We investigated the consequences of chloroplastic and total cellular ascorbate-deficiencies by studying chloroplastic ascorb...
ACCEPTED IN PLANT PHYSIOLOGY.
Ascorbate is a major plant metabolite that plays crucial roles in various processes, from reactive oxygen scavenging to epigenetic regulation. However, to what extent and how ascorbate modulates metabolism is largely unknown. To address this, we investigated the consequences of chloroplastic and total cellular ascorbat...
Biophotovoltaics (BPV) are a potential decentralized and environmentally friendly energy source that harness solar energy through photosynthesis. These BPV devices are self-regenerating, promising long-term usability. A practical strategy for enhancing BPV performance is to systematically screen for highly exoelectrogenic algal strains capable of g...
In eukaryotic cells, phosphorus is assimilated and utilized primarily as phosphate (Pi). Pi homeostasis is mediated by transporters that have not yet been adequately characterized in green algae. This study reports on PHOSPHATE TRANSPORTER 4-7 (CrPHT4-7) from Chlamydomonas reinhardtii, a member of the PHT4 transporter family, which exhibits remarka...
The acclimation of cyanobacteria to iron deficiency is crucial for their survival in natural environments. In response to iron deficiency, many cyanobacterial species induce the production of a pigment-protein complex called IsiA (iron-stress-induced protein A). IsiA proteins associate with photosystem I (PSI) and can function as light-harvesting a...
PUBLISHED IN PLANT PHYSIOLOGY. In eukaryotic cells, phosphorus is assimilated and utilized primarily as phosphate (Pi). Pi homeostasis is mediated by transporters that have not yet been adequately characterized in green algae. This study reports on CrPHT4-7 from Chlamydomonas reinhardtii , a member of the PHT4 transporter family, which exhibits rem...
PSBO is an essential subunit of the oxygen-evolving complex and we recently demonstrated that its lifetime depends on environmental conditions in Chlamydomonas reinhardtii. To assess PSBO lifetime with a high time resolution, we employed (1) a microfluidic platform enabling the trapping of single cells and the parallel measurement of photosynthetic...
The acclimation of cyanobacteria to iron deficiency is crucial for their survival in natural environments. In response to iron deficiency, many cyanobacterial species induce the production of a pigment-protein complex called IsiA. IsiA proteins associate with photosystem I (PSI) and can function as light-harvesting antennas or dissipate excess ener...
Iron deficiency is a common challenge faced by cyanobacteria in oceanic environments and the acclimation to iron deficiency is crucial for their survival. In response to iron deficiency, many cyanobacterial species induce the production of a pigment-protein complex called IsiA. IsiA proteins associate with photosystem I (PSI) and can function as li...
Photosynthetic hydrogen production from microalgae is considered to have potential as a renewable energy source. Yet, the process has two main limitations holding it back from scaling up; (i) electron loss to competing processes, mainly carbon fixation and (ii) sensitivity to O 2 which diminishes the expression and the activity of the hydrogenase e...
Ascorbate (Asc) is a multifunctional metabolite essential for various cellular processes in plants and animals. The best-known property of Asc is to scavenge reactive oxygen species (ROS), in a highly regulated manner. Besides being an effective antioxidant, Asc also acts as a chaperone for 2-oxoglutarate-dependent dioxygenases that are involved in...
PSBO is essential for the assembly of the oxygen‐evolving complex in plants and green algae. Despite its importance, we lack essential information on its lifetime and how it depends on the environmental conditions. We have generated nitrate‐inducible PSBO amiRNA lines in the green alga Chlamydomonas reinhardtii. Transgenic strains grew normally und...
We have previously created and expressed a chimeric polypeptide joining the PsaC subunit of Photosystem I (PSI) to the HydA2 hydrogenase of Chlamydomonas reinhardtii and demonstrated that it assembles into the PSI complex and feeds electrons directly to the hydrogenase domain, allowing for prolonged photobiological hydrogen production. Here we desc...
Symbiodiniaceae is an important dinoflagellate family which lives in endosymbiosis with reef invertebrates, including coral polyps, making them central to the holobiont. With coral reefs currently under extreme threat from climate change, there is a pressing need to improve our understanding on the stress tolerance and stress avoidance mechanisms o...
Chlamydomonas reinhardtii is a model organism of increasing biotechnological importance, yet, the evaluation of its life cycle processes and photosynthesis on a single-cell level is largely unresolved. To facilitate the study of the relationship between morphology and photochemistry, we established microfluidics in combination with chlorophyll a fl...
Photosynthetic green algae face an ever-changing environment of fluctuating light as well as unstable oxygen levels, which via the production of free radicals constantly challenges the integrity of the photosynthetic complexes. To face such challenges, a complex photosynthetic control network monitors and tightly control the membrane redox potentia...
Photobiological hydrogen (H2) production is a promising renewable energy source. HydA hydrogenases of green algae are efficient but O2-sensitive and compete for electrons with CO2-fixation. Recently, we established a photoautotrophic H2 production system based on anaerobic induction, where the Calvin-Benson cycle is inactive and O2 scavenged by an...
Ascorbate (Asc, vitamin C) is an essential metabolite participating in multiple physiological processes of plants, including environmental stress management and development. In this study we acquired knowledge on the role of Asc in dark‐induced leaf senescence using Arabidopsis thaliana as model organism. One of the earliest effects of prolonged da...
An overview is given of several studies on the fast chlorophyll (Chl) a fluorescence (OJIP) transient carried out in the laboratory of Reto Strasser between 2001 and 2009. At the beginning of this period the HandyPEA and PEA-Senior instruments were introduced by Reto Strasser and Hansatech Instruments Ltd. (UK) that gave a lot of experimental flexi...
The composition of the thylakoid proton motive force (pmf) is regulated by thylakoid ion transport. Passive ion channels in the thylakoid membrane dissipate the membrane potential (Δψ) component to allow for a higher fraction of pmf stored as a proton concentration gradient (ΔpH). K+/H+ antiport across the thylakoid membrane via K+ EXCHANGE ANTIPOR...
Plants have to adapt their metabolism to constantly changing environmental conditions, among which the availability of light and water is crucial in determining growth and development. Proline accumulation is one of the sensitive metabolic responses to extreme conditions; it is triggered by salinity or drought and is regulated by light. Here we sho...
Background:
The development of renewable and sustainable biofuels to cover the future energy demand is one of the most challenging issues of our time. Biohydrogen, produced by photosynthetic microorganisms, has the potential to become a green biofuel and energy carrier for the future sustainable world, since it provides energy without CO2 emission...
Ascorbate (Asc, vitamin C) plays essential roles in development, signaling, hormone biosynthesis, regulation of gene expression, stress resistance and photoprotection. In vascular plants, violaxanthin de-epoxidase (VDE) requires Asc as reductant, thereby it is required for the energy-dependent component of non-photochemical quenching (NPQ). To asse...
Ascorbate (vitamin C) plays essential roles in development, signaling, hormone biosynthesis, regulation of gene expression, stress resistance and photoprotection. In vascular plants, violaxanthin de-epoxidase (VDE) requires ascorbate (Asc) as reductant, thereby it is required for the energy-dependent component of non-photochemical quenching (NPQ)....
Hydrogen is a promising energy carrier, but producing it sustainably remains a challenge. Green algae can produce hydrogen photosynthetically using their efficient but oxygen-sensitive hydrogenases. Recent strategies aiming to bypass competing processes provide a promising route for scaling up algal hydrogen production.
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Selenium (Se) is a natural trace element, which shifts its action in a relatively narrow concentration range from nutritional role to toxicity. Although it has been well established that in plants chloroplasts are among the primary targets, the mechanism of toxicity on photosynthesis is not well understood. Here, we compared selenate and red-allotr...
The present invention relates to a method of hydrogen gas generation, wherein algae capable of expressing one or more types of hydrogenases are first cultured under hypoxic or ostensibly anoxic conditions in the dark (induction phase); subsequently under illuminated conditions in a medium devoid of organic or inorganic carbon sources (production ph...
Background
Photobiological H2 production has the potential of becoming a carbon-free renewable energy source, because upon the combustion of H2, only water is produced. The [Fe–Fe]-type hydrogenases of green algae are highly active, although extremely O2-sensitive. Sulphur deprivation is a common way to induce H2 production, which, however, relies...
Sulphur limitation may restrain cell growth and viability. In the green alga, Chlamydomonas reinhardtii, sulphur limitation may induce H2 production lasting for several days, to be exploited as a renewable energy source. Sulphur limitation causes a large number of physiological changes, including the inactivation of photosystem II (PSII), leading t...
Significance:
Ascorbate is an essential compound both in animals and plants, mostly due to its reducing properties, thereby playing a role in scavenging reactive oxygen species and acting as a cofactor in various enzymatic reactions. Recent Advances: Growing number of evidence show that excessive ascorbate accumulation may have negative effects on...
Background: Under low O2 concentration (hypoxia) and low light, Chlamydomonas cells can produce H2 gas in nutrient-replete conditions. This process is hindered by the presence of O2, which inactivates the [FeFe]-hydrogenase enzyme responsible for H2 gas production shifting algal cultures back to normal growth. The main pathways account- ing for H2...
PSI is the most efficient bioenergetic nanomachine in nature and one of the largest membrane protein complexes known. It is composed of 18 protein subunits that bind more than 200 co-factors and prosthetic groups. While the structure and function of PSI have been studied in great detail, very little is known about the PSI assembly process. In this...
Ascorbate (vitamin C) plays essential roles in stress resistance, development, signaling, hormone biosynthesis and regulation of gene expression; however, little is known about its biosynthesis in algae.
In order to provide experimental proof for the operation of the Smirnoff–Wheeler pathway described for higher plants and to gain more information...
Ascorbate (Asc, also called vitamin C) is of vital importance to the cellular functions of both animals and plants. During evolution, Asc has become one of the most abundant metabolites in seed plants; however, Asc contents in cyanobacteria, green algae and bryophytes are very low. Here we describe a sensitive and reliable HPLC method for the quant...
In nature, H2 production in Chlamydomonas reinhardtii serves as a safety valve during the induction of photosynthesis in anoxia and it prevents the over-reduction of the photosynthetic electron transport chain. Sulphur deprivation of C. reinhardtii also triggers a complex metabolic response resulting in the induction of various stress-related genes...
Most of the enzymatic reactions of ascorbate biosynthesis occur in the cytosol, with the exception of the terminal step, catalyzed by L-galactono-1,4-lactone dehydrogenase, which is localized on the inner mitochondrial membrane. Given the location of L-galactono-1,4-lactone dehydrogenase, the rate of ascorbate biosynthesis is intimately associated...
During plant development and in response to fluctuating environmental conditions, large changes in leaf assimilation capacity and in the metabolic consumption of ATP and NADPH produced by the photosynthetic apparatus can occur. To minimize cytotoxic side reactions, such as the production of reactive oxygen species, photosynthetic electron transport...
The biogenesis of the cytochrome b(6)f complex in tobacco (Nicotiana tabacum) seems to be restricted to young leaves, suggesting a high lifetime of the complex. To directly determine its lifetime, we employed an ethanol-inducible RNA interference (RNAi) approach targeted against the essential nuclear-encoded Rieske protein (PetC) and the small M su...
The composition of the photosynthetic apparatus of higher plants is dynamically adjusted to long-term changes in environmental conditions such as growth light intensity and light quality, and to changing metabolic demands for ATP and NADPH imposed by stresses and leaf aging. By changing photosynthetic complex stoichiometry, a long-term imbalance be...
Chlorophyll a fluorescence is a non-invasive tool widely used in photosynthesis research. According to the dominant interpretation, based on the model proposed by Duysens and Sweers (1963, Special Issue of Plant and Cell Physiology, pp 353-372), the fluorescence changes reflect primarily changes in the redox state of QA, the primary quinone electro...
Previously, we showed that ascorbate (Asc), by donating electrons to photosystem II (PSII), supports a sustained electron transport activity in heat-treated leaves. In this study, by using wild-type, Asc-overproducing and -deficient Arabidopsis thaliana mutants (miox4 and vtc2–3, respectively), we investigated the physiological role of Asc as PSII...
The green alga Chlamydomonas reinhardtii is capable of photoproducing molecular hydrogen
following sulphur deprivation, which results in anaerobiosis and a suppression of oxygen
evolution and thus an alleviation of the inhibitory effect of oxygen on the hydrogenase. At
the same time it transiently maintains a limited supply of electrons arising fro...
The effects of changes in the chlorophyll (chl) content on the kinetics of the OJIP fluorescence transient were studied using two different approaches. An extensive chl loss (up to 5-fold decrease) occurs in leaves suffering from either an Mg(2+) or SO(4)(2-) deficiency. The effects of these treatments on the chl a/b ratio, which is related to ante...
Selective inhibition of gene expression by antisense oligodeoxynucleotides (ODNs) is widely applied in gene function analyses; however, experiments with ODNs in plants are scarce. In this work, we extend the use of ODNs in different plant species, optimizing the uptake, stability, and efficiency of ODNs with a combination of molecular biological an...
Cyclic electron flow around photosystem I drives additional proton pumping into the thylakoid lumen, which enhances the protective non-photochemical quenching and increases ATP synthesis. It involves several pathways activated independently. In whole barley leaves, P700 oxidation under far-red illumination and subsequent P700(+) dark reduction kine...
Experiments were carried out to identify a process co-determining with Q(A) the fluorescence rise between F(0) and F(M). With 3-(3',4'-dichlorophenyl)-1,1-dimethylurea (DCMU), the fluorescence rise is sigmoidal, in its absence it is not. Lowering the temperature to -10°C the sigmoidicity is lost. It is shown that the sigmoidicity is due to the kine...
To analyze the role of phosphatidylglycerol (PG) in photosynthetic membranes of cyanobacteria we used two
mutants of Synechocystis sp. PCC6803: the PAL mutant which has no phycobilisomes and shows a high PSII/
PSI ratio, and a mutant derived from it by inactivating its cdsA gene encoding cytidine 5'-diphosphate
diacylglycerol synthase, a key enzyme...
Oxygen-Evolution Can Be Fully Inhibited With A Heat Pulse (E.G. Submerging Barley Leaves In Water Bath Of 4850°C For 40 S) Without Inducing Visible Symptoms And Secondary Effects, Such As Dessication. Under These Conditions, A Limited Linear Electron Transport Is Observed Which Is Due To The Presence Of Alternative Electron Donors That Donate Elect...
The plastoquinone (PQ) pool of the photosynthetic electron transport chain becomes reduced under anaerobic conditions. Here, anaerobiosis was used as a tool to manipulate the PQ-pool redox state in darkness and to study the effects of the PQ-redox state on the Chl-a fluorescence (OJIP) kinetics in pea leaves (Pisum sativum L.). It is shown that the...
Electron transport processes were investigated in barley leaves in which the oxygen-evolution was fully inhibited by a heat pulse (48 °C, 40 s). Under these circumstances, the K peak (∼ F400 μs) appears in the chl a fluorescence (OJIP) transient reflecting partial QA reduction, which is due to a stable charge separation resulting from the donation...
Chlorophyll (Chl) a fluorescence transient and 820-nm transmission kinetic were investigated to explore the development of photosynthetic apparatus
in grapevine leaves from emergence to full expansion. In this study, all leaves at various developing stages exhibited typical
Chl a fluorescence transient. In newly initiating leaves, the maximum quant...
The dark recovery kinetics of the Chl a fluorescence transient (OJIP) after 15 min light adaptation were studied and interpreted with the help of simultaneously measured 820 nm transmission. The kinetics of the changes in the shape of the OJIP transient were related to the kinetics of the qE and qT components of non-photochemical quenching. The dar...
Dans le domaine de la recherche de la photosynthèse, la cinétique de la fluorescence de la chlorophylle (OJIP) est une des méthodes les plus courantes. Cette méthode très sensible permet de mesurer "in vivo" l'activité photosynthétique. Cependant, il subsiste plusieurs questions fondamentales concernant son interprétation. Dans cette thèse, nous av...
The effects of DCMU (3-(3',4'-dichlorophenyl)-1,1-dimethylurea) on the fluorescence induction transient (OJIP) in higher plants were re-investigated. We found that the initial (F(0)) and maximum (F(M)) fluorescence levels of DCMU-treated leaves do not change relative to controls when the treatment is done in complete darkness and DCMU is allowed to...
Leaves of 7-day-old barley seedlings were subjected to heat pulses at 50 degrees C for 20 or 40s to inhibit partially or fully the oxygen evolution without inducing visible symptoms. By means of biophysical techniques, we investigated the time course and mechanism of photosystem II (PSII) recovery. After the heat treatment, the samples were charact...
The effects of dibromothymoquinone (DBMIB) and methylviologen (MV) on the Chl a fluorescence induction transient (OJIP) were studied in vivo. Simultaneously measured 820-nm transmission kinetics were used to monitor electron flow through photosystem I (PSI). DBMIB inhibits the reoxidation of plastoquinol by binding to the cytochrome b(6)/f complex....
Electron donation to Tyrz in heat-inactivated photosystem II (PSII) reaction centers by alternative donors was evaluated. Chl a fluorescence transients indicate that in the 0.1-3 ms range (K-step) only one electron is available, but that in the 0.2-2 s range accumulation of QA- took place that coincided with the re-reduction of plastocyanin PC+ and...