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1.
Plant Physiol Biochem ; 152: 125-137, 2020 May 07.
Artigo em Inglês | MEDLINE | ID: mdl-32416342

RESUMO

Chosen aspects of the functioning of diadinoxanthin cycle in a model diatom Phaeodactylum tricornutum grown under low light conditions (LL) and under high light conditions (HL), which cause activation of violaxanthin cycle, were examined. Heterogeneity of the kinetics of diadinoxanthin ↔ diatoxanthin conversions regulated by de-epoxidase/epoxidase enzymes was detected. Three different rates of diadinoxanthin de-epoxidation (τ > 20 min, 5 min > τ > 1.5 min and τ ≤ 1 min) were observed. Appearance and contribution of these phases depended on the light conditions and xanthophylls subpopulations in membranes. Moreover, diadinoxanthin de-epoxidation was postulated to occur in darkness and its rate was estimated to be almost two times faster (τ ≈ 14 min) than diatoxanthin-epoxidation in LL- and HL-grown diatoms collected after the dark phase of the photoperiod and exposed to very high light and subsequent darkness. The level of lipid hydroperoxides and the expression of genes encoding xanthophyll cycle enzymes was measured. Our observations suggest that isoforms of these enzymes may participate in carotenoid synthesis or be exclusively involved in xanthophyll conversions. Violaxanthin cycle pigments present in HL-acclimated diatoms change thermodynamic properties of thylakoid membranes. Zeaxanthin is known to localize preferentially in the inner part of the lipid bilayer and diatoxanthin in its outer part. The different localization of these pigments probably decide about their complementary action in protection of the membranes against reactive oxygen species.

2.
Ecotoxicol Environ Saf ; 191: 110241, 2020 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-32007925

RESUMO

One of the major mechanisms of heavy metal toxicity is the induction of oxidative stress. Redox-active heavy metals, like chromium, can induce it directly, whereas redox-inactive metals, like cadmium, play an indirect role in the generation of reactive oxygen species (ROS). Living organisms defend themselves against oxidative stress taking advantage of low-molecular-weight antioxidants and ROS-detoxifying enzymes. Tocopherols and plastoquinol are important plastid prenyllipid antioxidants, playing a role during acclimation of Chlamydomonas reinhardtii to heavy metal-induced stress. However, partial inhibition of synthesis of these prenyllipids by pyrazolate did not decrease the tolerance of C. reinhardtii to Cr- and Cd-induced stress, suggesting redundancy between antioxidant mechanisms. To verify this hypothesis we have performed comparative analyses of growth, photosynthetic pigments, low-molecular-weight antioxidants (tocopherols, plastoquinol, plastochromanol, ascorbate, soluble thiols, proline), activities of the ascorbate peroxidase (APX), catalase and superoxide dismutase (SOD) and cumulative superoxide production in C. reinhardtii exposed to Cd2+ and Cr2O72- ions in the presence or absence of pyrazolate. The decreased α-tocopherol and plastoquinol content resulted in the increase in superoxide generation and APX activity in pyrazolate-treated algae. The application of heavy metal ions and pyrazolate had a pronounced impact on Asc and total thiol content, as well as SOD and APX activities (the latter only in Cd-exposed cultures), when compared with algae grown in the presence of heavy metal ions or pyrazolate alone. The superoxide production in cultures exposed to heavy metal ions and pyrazolate decreased when compared to the cultures exposed to either heavy metal ions or an inhibitor alone.


Assuntos
Antioxidantes/metabolismo , Cloreto de Cádmio/toxicidade , Cromatos/toxicidade , Plastoquinona/análogos & derivados , Compostos de Potássio/toxicidade , Tocoferóis/metabolismo , Chlamydomonas reinhardtii/metabolismo , Relação Dose-Resposta a Droga , Íons , Estresse Oxidativo/efeitos dos fármacos , Fotossíntese/efeitos dos fármacos , Plastoquinona/metabolismo , Espécies Reativas de Oxigênio/metabolismo
3.
Physiol Plant ; 168(3): 617-629, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31264713

RESUMO

Methods of chlorophyll fluorescence measurements are widely used in the research on photosynthesis and ecophysiology of plants and algae. Among them, a very popular technique is pulse-amplitude-modulation (PAM) flourometry, which is simple to carry out, fast and non-invasive. However, this method is also prone to generate artifacts if the experiments were not planned and executed properly. Application of this technique to algae brings additional complications, which need to be taken into consideration. Some of them are connected with sample preparation and setting of the protocols used, while another origin from the differences in the photosynthetic apparatus and regulation of photosynthesis in various algal groups when compared to vascular plants. In the present paper, some important practical aspects concerning PAM fluorometry measurements in the green microalga Chlamydomonas reinhardtii have been described, including the equipment settings and sample preparation. The impact of growth conditions, such as light, temperature and medium type on the induction of non-photochemical quenching of chlorophyll fluorescence have been also tackled, as well as the question of state transitions occurring in darkness.


Assuntos
Chlamydomonas reinhardtii/química , Clorofila/química , Fluorescência , Fotossíntese , Luz , Microalgas/química
4.
J Biotechnol ; 298: 21-34, 2019 Jun 10.
Artigo em Inglês | MEDLINE | ID: mdl-30978366

RESUMO

The use of chemical fertilizers and pesticides, as well as the development of high-yielding varieties enabled substantial increase in crop productivity during the 20th century. However, the increase in yield over the last two decades has been slower. It is thought that further improvement in productivity of the major crop species using traditional cultivation methods is limited. Therefore, the use of genetic engineering seems to be a promising approach. There is ongoing research concerning genes that have an impact on plant growth, development and yield. The proteins and miRNAs encoded by these genes participate in a variety of processes, such as growth regulation, assimilate transport and partitioning as well as macronutrient uptake and metabolism. This paper presents the major directions in research concerning genes that may be targets of genetic engineering aimed to improve plant productivity.


Assuntos
Produção Agrícola , Produtos Agrícolas/genética , Engenharia Genética , Plantas Geneticamente Modificadas/genética , Produtos Agrícolas/crescimento & desenvolvimento , Regulação da Expressão Gênica de Plantas/genética , Desenvolvimento Vegetal/genética , Plantas Geneticamente Modificadas/crescimento & desenvolvimento
5.
J Plant Physiol ; 231: 415-433, 2018 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-30412849

RESUMO

With unfavourable climate changes and an increasing global population, there is a great need for more productive and stress-tolerant crops. As traditional methods of crop improvement have probably reached their limits, a further increase in the productivity of crops is expected to be possible using genetic engineering. The number of potential genes and metabolic pathways, which when genetically modified could result in improved photosynthesis and biomass production, is multiple. Photosynthesis, as the only source of carbon required for the growth and development of plants, attracts much attention is this respect, especially the question concerning how to improve CO2 fixation and limit photorespiration. The most promising direction for increasing CO2 assimilation is implementating carbon concentrating mechanisms found in cyanobacteria and algae into crop plants, while hitherto performed experiments on improving the CO2 fixation versus oxygenation reaction catalyzed by Rubisco are less encouraging. On the other hand, introducing the C4 pathway into C3 plants is a very difficult challenge. Among other points of interest for increased biomass production is engineering of metabolic regulation, certain proteins, nucleic acids or phytohormones. In this respect, enhanced sucrose synthesis, assimilate translocation to sink organs and starch synthesis is crucial, as is genetic engineering of the phytohormone metabolism. As abiotic stress tolerance is one of the key factors determining crop productivity, extensive studies are being undertaken to develop transgenic plants characterized by elevated stress resistance. This can be accomplished due to elevated synthesis of antioxidants, osmoprotectants and protective proteins. Among other promising targets for the genetic engineering of plants with elevated stress resistance are transcription factors that play a key role in abiotic stress responses of plants. In this review, most of the approaches to improving the productivity of plants that are potentially promising and have already been undertaken are described. In addition to this, the limitations faced, potential challenges and possibilities regarding future research are discussed.


Assuntos
Produção Agrícola/métodos , Fotossíntese , Desenvolvimento Vegetal , Engenharia Genética , Fotossíntese/genética , Desenvolvimento Vegetal/genética , Fenômenos Fisiológicos Vegetais/genética , Plantas/genética , Plantas Geneticamente Modificadas , Estresse Fisiológico/genética
6.
Postepy Biochem ; 64(1): 13-20, 2018 Jun 30.
Artigo em Polonês | MEDLINE | ID: mdl-30652833

RESUMO

The significant increase in crop productivity occurred in the second half o the 20th century. However, it is thought that nowadays yield of main crop species reached its maximum. As we expect that the demand for plant products is going to increase during next century, it is necessary to develop new methods for yield improvement, other than traditional breeding. The redesign of photosynthesis using genetic engineering is one of the approaches postulated. The present article covers the main directions of research aimed to increase photosynthetic efficiency. The research covered by this review are: improvement of light capture, improvement of Rubisco and the regeneration phase of Calvin cycle, introducing carbon concentrating mechanisms to main crop species and reducing loss caused by photorespiration.


Assuntos
Engenharia Genética , Fotossíntese/genética , Carbono/metabolismo
7.
Phytochemistry ; 144: 171-179, 2017 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-28942064

RESUMO

Allelopathy is a phenomenon, where one species releases compounds able to inhibit the growth of other species. Juglone, 5-hydroxy-1,4-naphtoquinone, is an allelochemical produced by walnut trees. The main mode of juglone toxicity is the formation of semiquinone radicals, able to reduce O2 to superoxide. Prenyllipid antioxidants such as tocopherol and plastoquinone are important for antioxidant defense in photosynthetic organisms. Here we assess their participation in the response to juglone. The impact of 20 µM juglone on the content of photosynthetic pigments and prenyllipid antioxidants in green microalga Chlamydomonas reinhardtii was measured over an incubation period of 7.5 h in low light and over 40 min under high light or in darkness. The decrease in pigment and prenyllipid content, accompanied by an increase in lipid hydroperoxides was observed over a longer incubation period with juglone. Simultaneous exposure to high light and juglone led to a pronounced decrease in carotenoids and prenyllipids, while there was no decrease in high light alone and no decrease or only a slight decrease in the series with juglone alone. The fact that semiquinone radicals are generated in juglone-exposed cells was confirmed using EPR spectroscopy. This article also shows that C. reinhardtii may be a suitable model for studies on some modes of phytotoxic action of allelochemicals.


Assuntos
Alelopatia , Antioxidantes/metabolismo , Chlamydomonas reinhardtii/metabolismo , Naftoquinonas/metabolismo , Estresse Oxidativo , Plastoquinona/metabolismo , Tocoferóis/metabolismo , Antioxidantes/química , Carotenoides/química , Carotenoides/metabolismo , Clorofila/química , Clorofila/metabolismo , Espectroscopia de Ressonância de Spin Eletrônica , Peroxidação de Lipídeos , Naftoquinonas/química , Plastoquinona/química , Tocoferóis/química
8.
Mini Rev Med Chem ; 17(12): 1039-1052, 2017.
Artigo em Inglês | MEDLINE | ID: mdl-27457214

RESUMO

OBJECTIVE: This review examines various aspects of vitamin E, both in plant metabolism and with regard to its importance for human health. Vitamin E is the collective name of a group of lipidsoluble compounds, chromanols, which are widely distributed in the plant kingdom. Their biosynthetic pathway, intracellular distribution and antioxidant function in plants are well recognized, although their other functions are also considered. CONCLUSION: Analytical methods for the determination of vitamin E are discussed in detail. Furthermore, the vitamin E metabolism and its antioxidant action in humans are described. Other nonantioxidant functions of vitamin E are also presented, such as its anti-inflammatory effects, role in the prevention of cardiovascular diseases and cancer, as well as its protective functions against neurodegenerative and other diseases.


Assuntos
Plantas/química , Vitamina E/biossíntese , Animais , Antioxidantes/análise , Antioxidantes/metabolismo , Antioxidantes/farmacocinética , Cromatografia Líquida de Alta Pressão , Humanos , Sistema Imunitário/metabolismo , Doenças Neurodegenerativas/tratamento farmacológico , Plantas/metabolismo , Tocoferóis/análise , Tocoferóis/química , Tocoferóis/metabolismo , Tocoferóis/farmacocinética , Tocotrienóis/análise , Tocotrienóis/química , Tocotrienóis/metabolismo , Tocotrienóis/farmacocinética , Vitamina E/análise , Vitamina E/farmacocinética , Vitamina E/uso terapêutico
9.
PLoS One ; 11(7): e0159629, 2016.
Artigo em Inglês | MEDLINE | ID: mdl-27462710

RESUMO

In the present studies, we focused on substrate specificity of tocopherol cyclase, the key enzyme in the biosynthesis of the tocopherols and plastochromanol-8, the main plant lipid antioxidants, with special emphasis on the preference for tocopherols and plastochromanol-8 precursors, taking advantage of the recombinant enzyme originating from Arabidopsis thaliana and isolated plastoglobules, thylakoids and various model systems like micelles and thylakoids. Plastoglobules and triacylglycerol micelles were the most efficient reaction environment for the cyclase. In various investigated systems, synthesis of γ-tocopherol proceeded considerably faster than that of plastochromanol-8, probably mainly due to different localization of the corresponding substrates in the analyzed lipid structures. Moreover, our study was complemented by bioinformatics analysis of the phylogenetic relations of the cyclases and sequence motifs, crucial for the enzyme activity, were proposed. The analysis revealed also a group of tocopherol cyclase-like proteins in a number of heterotrophic bacterial species, with a conserved region common with photosynthetic organisms, that might be engaged in the catalytic activity of both groups of organisms.


Assuntos
Proteínas de Arabidopsis/metabolismo , Arabidopsis/enzimologia , Transferases Intramoleculares/metabolismo , Arabidopsis/genética , Proteínas de Arabidopsis/química , Proteínas de Arabidopsis/genética , Cromanos/metabolismo , Transferases Intramoleculares/química , Transferases Intramoleculares/genética , Filogenia , Especificidade por Substrato , Tilacoides/metabolismo , Tocoferóis/metabolismo , Vitamina E/análogos & derivados , Vitamina E/metabolismo
10.
Microbiol Res ; 186-187: 99-118, 2016.
Artigo em Inglês | MEDLINE | ID: mdl-27242148

RESUMO

Photosynthesis is a complex metabolic process enabling photosynthetic organisms to use solar energy for the reduction of carbon dioxide into biomass. This ancient pathway has revolutionized life on Earth. The most important event was the development of oxygenic photosynthesis. It had a tremendous impact on the Earth's geochemistry and the evolution of living beings, as the rise of atmospheric molecular oxygen enabled the development of a highly efficient aerobic metabolism, which later led to the evolution of complex multicellular organisms. The mechanism of photosynthesis has been the subject of intensive research and a great body of data has been accumulated. However, the evolution of this process is not fully understood, and the development of photosynthesis in prokaryota in particular remains an unresolved question. This review is devoted to the occurrence and main features of phototrophy and photosynthesis in prokaryotes. Hypotheses concerning the origin and spread of photosynthetic traits in bacteria are also discussed.


Assuntos
Bactérias/metabolismo , Evolução Biológica , Luz , Fotossíntese , Processos Fototróficos , Bactérias/genética , Dióxido de Carbono/metabolismo , Oxigênio/metabolismo
11.
Ecotoxicol Environ Saf ; 130: 133-45, 2016 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-27104807

RESUMO

Acclimation to heavy metal-induced stress is a complex phenomenon. Among the mechanisms of heavy metal toxicity, an important one is the ability to induce oxidative stress, so that the antioxidant response is crucial for providing tolerance to heavy metal ions. The effect of chronic stress induced by ions of five heavy metals, Ag, Cu, Cr (redox-active metals) Cd, Hg (nonredox-active metals) on the green microalga Chlamydomonas reinhardtii was examined at two levels - the biochemical (content of photosynthetic pigments and prenyllipid antioxidants, lipid peroxidation) and the physiological (growth rate, photosynthesis and respiration rates, induction of nonphotochemical quenching of chlorophyll fluorescence). The expression of the genes which encode the enzymes participating in the detoxification of reactive oxygen species (APX1, CAT1, FSD1, MSD1) was measured. The other gene measured was one required for plastoquinone and α-tocopherol biosynthesis (VTE3). The application of heavy metal ions partly inhibited growth and biosynthesis of chlorophyll. The growth inhibition was accompanied by enhanced lipid peroxidation. An increase in the content of prenyllipid antioxidants was observed in cultures exposed to Cr2O7(2-), Cd(2+) (α- and γ-tocopherol and plastoquinone) and Cu(2+) (only tocopherols). The induction of nonphotochemical quenching was enhanced in cultures exposed to Cu(2+), Cr2O7(2-) and Cd(2+), as compared to the control. Chronic heavy metal-induced stress led to changes in gene expression dependent on the type and concentration of heavy metal ions. The up-regulation of antioxidant enzymes was usually accompanied by the up-regulation of the VTE3 gene.


Assuntos
Chlamydomonas reinhardtii/efeitos dos fármacos , Poluentes Ambientais/toxicidade , Intoxicação por Metais Pesados , Metais Pesados/toxicidade , Estresse Oxidativo/efeitos dos fármacos , Adaptação Fisiológica , Antioxidantes/metabolismo , Chlamydomonas reinhardtii/crescimento & desenvolvimento , Chlamydomonas reinhardtii/metabolismo , Clorofila/metabolismo , Regulação da Expressão Gênica/efeitos dos fármacos , Íons/metabolismo , Peroxidação de Lipídeos/efeitos dos fármacos , Peróxidos Lipídicos/metabolismo , Metais Pesados/análise , Metais Pesados/metabolismo , Fotossíntese/efeitos dos fármacos , Envenenamento , Espécies Reativas de Oxigênio/metabolismo , Reação em Cadeia da Polimerase em Tempo Real , Respiração/efeitos dos fármacos , Regulação para Cima
12.
N Biotechnol ; 33(5 Pt B): 636-643, 2016 Sep 25.
Artigo em Inglês | MEDLINE | ID: mdl-26970272

RESUMO

Isoprenoid quinones and chromanols in plants fulfill both signaling and antioxidant functions under oxidative stress. The redox state of the plastoquinol pool (PQ-pool), which is modulated by interaction with reactive oxygen species (ROS) during oxidative stress, has a major regulatory function in both short- and long-term acclimatory responses. By contrast, the scavenging of ROS by prenyllipids affects signaling pathways where ROS play a role as signaling molecules. As the primary antioxidants, isoprenoid quinones and chromanols are synthesized under high-light stress in response to any increased production of ROS. During photo-oxidative stress, these prenyllipids are continuously synthesized and oxidized to other compounds. In turn, their oxidation products (hydroxy-plastochromanol, plastoquinol-C, plastoquinone-B) can still have an antioxidant function. The oxidation products of isoprenoid quinones and chromanols formed specifically in the face of singlet oxygen, can be indicators of singlet oxygen stress.


Assuntos
Cromanos/metabolismo , Plantas/metabolismo , Terpenos/metabolismo , Antioxidantes/metabolismo , Biotecnologia , Oxirredução , Estresse Oxidativo , Plastoquinona/metabolismo , Quinonas/metabolismo , Espécies Reativas de Oxigênio/metabolismo , Transdução de Sinais , Tocoferóis/metabolismo
13.
Plant Cell Environ ; 38(12): 2698-706, 2015 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-26013323

RESUMO

In the present study, we have identified new prenyllipid metabolites formed during high light stress in Arabidopsis thaliana, whose origin and function remained unknown so far. It was found that plastoquinone-C accumulates mainly in the reduced form under high light conditions, as well as during short-term excess light illumination both in the wild-type and tocopherol biosynthetic vte1 mutant, suggesting that plastoquinone-C, a singlet oxygen-derived prenyllipid, is reduced in chloroplasts by photosystem II or enzymatically, outside thylakoids. Plastoquinone-B, a fatty acid ester of plastoquinone-C, was identified for the first time in Arabidopsis in high light grown wild-type plants and during short-time, excess light illumination of the wild-type plants and the vte1 mutant. The gene expression analysis showed that vte2 gene is most pronouncedly up-regulated among the prenyllipid biosynthetic genes under high light and induction of its expression is mainly caused by an increased level of singlet oxygen, as was demonstrated in experiments with D2 O-treated plants under excess light conditions.


Assuntos
Alquil e Aril Transferases/genética , Proteínas de Arabidopsis/genética , Arabidopsis/metabolismo , Regulação Enzimológica da Expressão Gênica/efeitos da radiação , Transferases Intramoleculares/genética , Plastoquinona/metabolismo , Oxigênio Singlete/metabolismo , Alquil e Aril Transferases/metabolismo , Arabidopsis/química , Arabidopsis/genética , Arabidopsis/efeitos da radiação , Proteínas de Arabidopsis/metabolismo , Cloroplastos/metabolismo , Regulação da Expressão Gênica de Plantas/efeitos da radiação , Transferases Intramoleculares/metabolismo , Luz , Mutação , Estresse Oxidativo , Complexo de Proteína do Fotossistema II/metabolismo , Plastoquinona/análise , Tilacoides/metabolismo , Tocoferóis/metabolismo
14.
Physiol Plant ; 154(2): 194-209, 2015 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-25214438

RESUMO

During their lifetime, plants need to adapt to a changing environment, including light and temperature. To understand how these factors influence plant growth, we investigated the physiological and antioxidant responses of two Arabidopsis accessions, Shahdara (Sha) from the Shahdara valley (Tajikistan, Central Asia) in a mountainous area and Lovvik-5 (Lov-5) from northern Sweden to different light and temperature conditions. These accessions originate from different latitudes and have different life strategies, both of which are known to be influenced by light and temperature. We showed that both accessions grew better in high-light and at a lower temperature (16°C) than in low light and at 23°C. Interestingly, Sha had a lower chlorophyll content but more efficient non-photochemical quenching than Lov-5. Sha, also showed a higher expression of vitamin E biosynthetic genes. We did not observe any difference in the antioxidant prenyllipid level under these conditions. Our results suggest that the mechanisms that keep the plastoquinone (PQ)-pool in more oxidized state could play a role in the adaptation of these accessions to their local climatic conditions.


Assuntos
Antioxidantes/metabolismo , Arabidopsis/fisiologia , Aclimatação , Arabidopsis/genética , Arabidopsis/efeitos da radiação , Arabidopsis/ultraestrutura , Clorofila/metabolismo , Luz , Oxirredução , Folhas de Planta/genética , Folhas de Planta/fisiologia , Folhas de Planta/efeitos da radiação , Folhas de Planta/ultraestrutura , Plastoquinona/metabolismo , Suécia , Temperatura
15.
Plant Cell Environ ; 37(6): 1464-73, 2014 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-24329808

RESUMO

In the present study, we have shown that hydroxy-plastochromanol and plastoquinone-C, the hydroxy derivatives of plastochromanol and plastoquinone-9, respectively, are specifically formed from the parent compounds upon action of singlet oxygen and can be regarded as stable, specific, natural products of singlet oxygen action during photo-oxidative stress in vivo. The presented data indicate that plastoquinone-C formation dominates mainly during relatively short periods of high light stress where efficient production of singlet oxygen takes place, whereas hydroxy-plastochromanol is rather formed under conditions of long-term, less pronounced generation of singlet oxygen. An interesting observation was that hydroxy-plastochromanol is formed even at very low light conditions (5-10 µmol photons m(-2) s(-1)), indicating that singlet oxygen is generated not only during high light stress but also its formation by photosystem II is inseparably connected with the functioning of this photosystem even at the lowest light intensities.


Assuntos
Arabidopsis/efeitos da radiação , Cromanos/metabolismo , Estresse Oxidativo , Plastoquinona/metabolismo , Antioxidantes/metabolismo , Arabidopsis/metabolismo , Cromanos/química , Cromatografia Líquida de Alta Pressão , Lipídeos/química , Plastoquinona/análogos & derivados , Plastoquinona/química
16.
Biochim Biophys Acta ; 1828(2): 233-40, 2013 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-22959712

RESUMO

Lipid peroxidation is an oxidation reaction leading to the generation of lipid hydroperoxides. Here we present comparative data on the inhibition of lipid peroxidation by a variety of biological prenyllipids in liposomes prepared from natural lipid membranes. Lipid peroxidation was initiated by hydrophilic and hydrophobic azo initiators, as well as by singlet oxygen generated via photosensitized reaction of hydrophobic zinc tetraphenylporphine. When lipid peroxidation was initiated in the water phase, tocopherols and plastochromanol-8 were more effective than prenylquinols, such as plastoquinol-9, ubiquinol-10 or α-tocopherolquinol. However, if the peroxidation was initiated within the hydrophobic interior of liposome membranes, long-chain prenyllipids, such as plastoquinol-9 and plastochromanol-8, were considerably more active than tocopherols in the inhibition of the reaction. In the latter system, tocopherols showed even prooxidant activity. The prooxidant activity of α-tocopherol was prevented by plastoquinol, suggesting the reduction of α-tocopheroxyl radical by the quinol. All the investigated prenyllipids were able to inhibit singlet oxygen-mediated lipid peroxidation but the most active were prenylquinols in this respect. Among all the prenyllipids investigated, plastochromanol-8 was the most versatile antioxidant in the inhibition of lipid peroxidation initiated by the three different methods.


Assuntos
Cromanos/química , Peroxidação de Lipídeos , Lipídeos/química , Vitamina E/análogos & derivados , Antioxidantes/química , Cromatografia Líquida de Alta Pressão , Radicais Livres/química , Luz , Modelos Químicos , Oxigênio/química , Plastoquinona/química , Fatores de Tempo , Vitamina E/química , Zinco/química , alfa-Tocoferol/química
17.
Biochim Biophys Acta ; 1817(3): 389-94, 2012 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-22192719

RESUMO

In the present study, we have performed comparative analysis of different prenyllipids in Chlamydomonas reinhardtii cultures during high light stress under variety of conditions (presence of inhibitors, an uncoupler, heavy water). The obtained results indicate that plastoquinol is more active than α-tocopherol in scavenging of singlet oxygen generated in photosystem II. Besides plastoquinol, also its oxidized form, plastoquinone shows antioxidant action during the stress conditions, resulting in formation of plastoquinone-C, whose level can be regarded as an indicator of singlet oxygen oxidative stress in vivo. The pronounced stimulation of α-tocopherol consumption and α-tocopherolquinone formation by an uncoupler, FCCP, together with the results of additional model system studies, led to the suggestion that α-tocopherol can be recycled in thylakoid membranes under high light conditions from 8a-hydroperoxy-α-tocopherone, the primary oxidation product of α-tocopherol by singlet oxygen.


Assuntos
Chlamydomonas reinhardtii/metabolismo , Plastoquinona/análogos & derivados , Oxigênio Singlete/metabolismo , alfa-Tocoferol/metabolismo , Luz , Oxirredução , Estresse Oxidativo , Plastoquinona/metabolismo , Estresse Fisiológico
18.
Biochim Biophys Acta ; 1797(9): 1587-605, 2010 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-20599680

RESUMO

Isoprenoid quinones are one of the most important groups of compounds occurring in membranes of living organisms. These compounds are composed of a hydrophilic head group and an apolar isoprenoid side chain, giving the molecules a lipid-soluble character. Isoprenoid quinones function mainly as electron and proton carriers in photosynthetic and respiratory electron transport chains and these compounds show also additional functions, such as antioxidant function. Most of naturally occurring isoprenoid quinones belong to naphthoquinones or evolutionary younger benzoquinones. Among benzoquinones, the most widespread and important are ubiquinones and plastoquinones. Menaquinones, belonging to naphthoquinones, function in respiratory and photosynthetic electron transport chains of bacteria. Phylloquinone K(1), a phytyl naphthoquinone, functions in the photosynthetic electron transport in photosystem I. Ubiquinones participate in respiratory chains of eukaryotic mitochondria and some bacteria. Plastoquinones are components of photosynthetic electron transport chains of cyanobacteria and plant chloroplasts. Biosynthetic pathway of isoprenoid quinones has been described, as well as their additional, recently recognized, diverse functions in bacterial, plant and animal metabolism.


Assuntos
Benzoquinonas/metabolismo , Transporte de Elétrons , Naftoquinonas/metabolismo , Plastoquinona/metabolismo , Ubiquinona/metabolismo , Vitamina E/análogos & derivados , Vitamina E/metabolismo , Vitamina K 1/metabolismo , Vitamina K 2/metabolismo
19.
Postepy Biochem ; 55(3): 307-14, 2009.
Artigo em Polonês | MEDLINE | ID: mdl-19928587

RESUMO

Prenylquinones are a group of compounds occurring in all living cells. In their structure a polar head group undergoing redox reactions and a long, hydrophobic side-chain can be found. Due to their amphiphilic character, these compounds are mainly located in biological membranes where they function as electron and proton carriers in the photosynthetic and respiratory electron transport chains. Prenylquinones play also additional roles such as antioxidants, and other more specific functions such as enzyme cofactors. Based on the ring structure, different groups of prenylquinones are distinguished: menaquinones, phylloquinone, ubiquinones and plastoquinones, although also other representatives of this group are known, e.g. tocopherolquinones. Frequently, biosynthesis ability of a given kind of prenylquinones is limited to a certain group of organisms. This review describes the structure, function and biosynthesis of most common prenylquinones.


Assuntos
Benzoquinonas/química , Benzoquinonas/metabolismo , Animais , Antioxidantes/metabolismo , Benzoquinonas/classificação , Humanos , Peroxidação de Lipídeos/fisiologia , Oxirredução , Plantas/metabolismo , Plastoquinona/química , Plastoquinona/metabolismo , Ubiquinona/biossíntese , Ubiquinona/química
20.
J Plant Physiol ; 166(10): 1045-56, 2009 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-19278749

RESUMO

Zeaxanthin epoxidase (ZE, E.C. 1.14.13.90), an enzyme belonging to the lipocalin superfamily, catalyses the conversion of zeaxanthin to antheraxanthin and violaxanthin. These reactions are part of the xanthophyll biosynthetic pathway and the xanthophyll cycle. The role of carotenoids in the dissipation of excessive light energy has been widely studied using mutants with a disabled carotenoid biosynthetic pathway. In this paper, the transgenic line MaZEP7 with partially disabled ZE activity is described and compared with wild-type plants and npq2 mutant lacking active ZE. We examined the presence and the abundance of aba1 transcripts, measured pigment composition, xanthophyll cycle functioning and chlorophyll fluorescence in all three lines. The MaZEP7 line contains additional copies of the aba1 gene introduced by agroinfiltration, but no enhanced aba1 transcript level was observed. In addition, ZE activity in MaZEP7 was impaired, resulting in an altered xanthophyll profile. In dark-adapted plants, violaxanthin and neoxanthin levels were lower than in wild-type plants, whereas antheraxanthin and zeaxanthin levels were considerably higher. The presence of lutein epoxide was also observed. Violaxanthin levels changed only minimally during light exposition, whereas antheraxanthin was converted to zeaxanthin and there was no epoxidation during the course of the experiment indicating disturbed xanthophyll cycle functioning. The amounts of carotenoids and chlorophylls on a dry weight basis and chl a/chl b ratio were similar in all lines. The presence of epoxidated pigments in MaZEP7 plants indicates that epoxidation occurs, but it is likely very slow. Chlorophyll fluorescence measurements showed that the dependence of electron transport rates on light intensity for the MaZEP7 line resembled the npq2 mutant. Kinetic measurements showed that the MaZEP7 line exhibited very rapid induction and a high steady-state value of non-photochemical quenching.


Assuntos
Arabidopsis/enzimologia , Arabidopsis/metabolismo , Carotenoides/metabolismo , Oxirredutases/metabolismo , Plantas Geneticamente Modificadas/enzimologia , Plantas Geneticamente Modificadas/metabolismo , Xantofilas/metabolismo , Arabidopsis/genética , Arabidopsis/efeitos da radiação , Clorofila/metabolismo , Regulação da Expressão Gênica de Plantas/efeitos da radiação , Cinética , Luz , Oxirredutases/genética , Fotoquímica , Plantas Geneticamente Modificadas/genética , Zeaxantinas
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