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1.
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
2.
PLoS One ; 14(3): e0214757, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-30921437

RESUMO

Coelomic fluid of Eisenia andrei contains a number of UV-fluorescent compounds. In the present study we have found that four of these compounds showed identical fluorescence excitation and emission maxima at 310 nm and 364 nm, respectively, suggesting they share the same chromophore. NMR and HR-MS spectroscopy of the most abundant fluorophore reavealed that its molecule is composed of two quinazoline-2,4-dione rings connected by spermine linker. This compound was earlier indentified in Eisenia andrei as SP-8203. Moreover, we have identified the structure of the two other fluorophores, one differing from SP-8203 by the absence of N-acetyl group, the compound not reported in any other organisms before, and the other already found in E. fetida and regarded as species specific. However, our results indicate that this metabolite is also present in E. andrei in significant amounts. The possible origin and function of these new metabolites is discussed.


Assuntos
Líquidos Corporais/metabolismo , Corantes Fluorescentes/metabolismo , Oligoquetos/metabolismo , Animais , Corantes Fluorescentes/química
3.
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
4.
J Plant Physiol ; 229: 32-40, 2018 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-30031159

RESUMO

In this review, we summarize the results of experiments that lead to altered levels of phytohormones in transgenic plants to improve plant productivity. The available data indicate that manipulating the level of phytohormones might also be a promising way to enhance the environmental stress tolerance of crop plants. In the regulation of the level of phytohormones, both biosynthesis and their catabolism pathways can be targeted for engineering purposes. Moreover, the signaling pathways of phytohormones should explored in this respect. In genetic modifications, conditional promoters must be developed to avoid undesired effects on growth. In order to find a practical application, the effects of genetic modifications should be further verified under field conditions and over a longer time scale.


Assuntos
Reguladores de Crescimento de Planta/metabolismo , Plantas Geneticamente Modificadas/metabolismo , Plantas Geneticamente Modificadas/genética , Estresse Fisiológico/genética , Estresse Fisiológico/fisiologia
5.
Plant J ; 2018 Jun 14.
Artigo em Inglês | MEDLINE | ID: mdl-29901834

RESUMO

Prenylquinols (tocochromanols and plastoquinols) serve as efficient physical and chemical quenchers of singlet oxygen (1 O2 ) formed during high light stress in higher plants. Although quenching of 1 O2 by prenylquinols has been previously studied, direct evidence for chemical quenching of 1 O2 by plastoquinols and their oxidation products is limited in vivo. In the present study, the role of plastoquinol-9 (PQH2 -9) in chemical quenching of 1 O2 was studied in Arabidopsis thaliana lines overexpressing the SOLANESYL DIPHOSPHATE SYNTHASE 1 gene (SPS1oex) involved in PQH2 -9 and plastochromanol-8 biosynthesis. In this work, direct evidence for chemical quenching of 1 O2 by plastoquinols and their oxidation products is presented, which is obtained by microscopic techniques in vivo. Chemical quenching of 1 O2 was associated with consumption of PQH2 -9 and formation of its various oxidized forms. Oxidation of PQH2 -9 by 1 O2 leads to plastoquinone-9 (PQ-9), which is subsequently oxidized to hydroxyplastoquinone-9 [PQ(OH)-9]. We provide here evidence that oxidation of PQ(OH)-9 by 1 O2 results in the formation of trihydroxyplastoquinone-9 [PQ(OH)3 -9]. It is concluded here that PQH2 -9 serves as an efficient 1 O2 chemical quencher in Arabidopsis, and PQ(OH)3 -9 can be considered as a natural product of 1 O2 reaction with PQ(OH)-9. The understanding of the mechanisms underlying 1 O2 chemical quenching provides information on the role of plastoquinols and their oxidation products in the response of plants to photooxidative stress.

6.
J Plant Physiol ; 223: 57-64, 2018 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-29499454

RESUMO

As tocopherols are expected to protect PSII against toxic singlet oxygen it is surprising that the null tocopherol mutant vte1 has been reported to show only a weak enhancement of photosystem II photoinhibition under high irradiance. Based on the view that singlet oxygen is formed also in unstressed conditions, such as low light (LL), we hypothesized that some defense strategies are activated in vte1 in these light conditions. In support for that we noted several symptoms of stress at PSII in the mutant under LL, by means of parameters of fast and slow kinetics of chlorophyll fluorescence and of changes in the relative contribution of PSII antenna in comparison to those of PSI. This was associated with a lower extent of phosphorylation of PSII core proteins (D1 and CP43). PSII RCs do not totally recover from stress in vte1 even after the nocturnal phase. As a clear compensation for the impeded performance of PSII in the vte1 we noted an increased quantum efficiency of PSI. A pronounced changes between WT and the vte1 mutant were also related to conformation of LHCII at the beginning of photoperiod, suggesting the absence of LHCII trimers in the mutant. The thylakoids thickness was similar in WT and vte1 under LL, but a pronounced unstacking of thylakoids was evoked by HL only in vte1. In conclusion, we postulate that action of 1O2 on PSII in vte1 leads to some permanent damage at PSII core and at LHCII already under LL.


Assuntos
Arabidopsis/metabolismo , Clorofila/metabolismo , Luz , Complexo de Proteína do Fotossistema II/metabolismo , Tocoferóis/metabolismo , Cinética , Fosforilação
7.
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
8.
Plant Physiol Biochem ; 122: 1-9, 2018 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-29169080

RESUMO

The data presented indicate that there is a variety of unique prenyllipids, often of very limited taxonomic distribution, whose origin, biosynthesis, metabolism and biological function deserves to be elucidated. These compounds include tocoenols, tocochromanol esters, tocochromanol acids, plastoquinones and ubiquinones. Additionally, based on the available data, it can be assumed that there are still unrecognized prenyllipids, like prenylquinols fatty acid esters of the hydroquinone ring, including prenylquinol phosphates, and others, whose biological function might be of great importance. Our knowledge of these compounds is not only important from the scientific point of view, but may also be of practical significance to medicine, pharmacy or cosmetics.


Assuntos
Plantas/química , Plantas/metabolismo , Plastoquinona/química , Plastoquinona/metabolismo , Ubiquinona/química , Ubiquinona/metabolismo
10.
Bioessays ; 39(11)2017 11.
Artigo em Inglês | MEDLINE | ID: mdl-28976010

RESUMO

RubisCO (D-ribulose 1,5-bisphosphate carboxylase/oxygenase) is Earth's main enzyme responsible for CO2 fixation via carboxylation of ribulose-1,5-bisphosphate (RuBP) into organic matter. Besides the carboxylation reaction, RubisCO also catalyzes the oxygenation of RuBP by O2 , which is probably as old as its carboxylation properties. Based on molecular phylogeny, the occurrence of the reactive oxygen species (ROS)-removing system and kinetic properties of different RubisCO forms, we postulated that RubisCO oxygenase activity appeared in local microoxic areas, yet before the appearance of oxygenic photosynthesis. Here, in reviewing the literature, we present a novel hypothesis: the RubisCO early oxygenase activity hypothesis. This hypothesis may be compared with the exaptation hypothesis, according to which latent RubisCO oxygenase properties emerged later during the oxygenation of the Earth's atmosphere. The reconstruction of ancestral RubisCO forms using ancestral sequence reconstruction (ASR) techniques, as a promising way for testing of RubisCO early oxygenase activity hypothesis, is presented.


Assuntos
Evolução Molecular , Ribulose-Bifosfato Carboxilase/metabolismo , Archaea/enzimologia , Archaea/genética , Atmosfera , Bactérias/enzimologia , Bactérias/genética , Eucariotos/enzimologia , Eucariotos/genética , Cinética , Oxigênio/metabolismo , Plantas/enzimologia , Plantas/genética , Ribulose-Bifosfato Carboxilase/genética
11.
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
12.
Oxid Med Cell Longev ; 2017: 5092754, 2017.
Artigo em Inglês | MEDLINE | ID: mdl-28642809

RESUMO

[This corrects the article DOI: 10.1155/2016/1920208.].

13.
Biochem J ; 474(7): 1307-1320, 2017 03 23.
Artigo em Inglês | MEDLINE | ID: mdl-28188256

RESUMO

Light-dependent protochlorophyllide oxidoreductase (POR) is a plant enzyme involved in the chlorophyll biosynthesis pathway. POR reduces one of the double bonds of the protochlorophyllide (Pchlide) using NADPH and light. In the present study, we found out that phosphatidylglycerol and sulfoquinovosyl diacylglycerol are allosteric regulators of the nucleotide binding, which increase the affinity towards NADPH a 100-fold. Moreover, we showed for the first time that NADH can, like NADPH, form active complexes with Pchlide and POR, however, at much higher concentrations. Additionally, monogalactosyldiacylglycerol (MGDG) was shown to be the main factor responsible for the red shift of the fluorescence emission maximum of Pchlide:POR:NADPH complexes. Importantly, the emission maximum at 654 nm was obtained only for the reaction mixtures supplemented with MGDG and at least one of the negatively charged plant lipids. Moreover, the site-directed mutagenesis allowed us to identify amino acid residues that may be responsible for lipid binding and Pchlide coordination. Our experiments allowed us to identify six different Pchlide:POR complexes that differ in the fluorescence emission maxima of the pigment. The results presented here reveal the contribution of thylakoid lipids in the regulation of the chlorophyll biosynthesis pathway; however, the molecular mechanisms of this process are to be clarified.


Assuntos
Proteínas de Arabidopsis/metabolismo , Arabidopsis/metabolismo , Galactolipídeos/metabolismo , Oxirredutases atuantes sobre Doadores de Grupo CH-CH/química , Oxirredutases atuantes sobre Doadores de Grupo CH-CH/metabolismo , Fosfatidilgliceróis/metabolismo , Sequência de Aminoácidos , Arabidopsis/genética , Proteínas de Arabidopsis/química , Proteínas de Arabidopsis/genética , Sítios de Ligação , Clorofila/biossíntese , Clonagem Molecular , Escherichia coli/genética , Escherichia coli/metabolismo , Galactolipídeos/química , Expressão Gênica , Cinética , Luz , Modelos Moleculares , Mutação , NAD/química , NAD/metabolismo , NADP/química , NADP/metabolismo , Oxirredutases atuantes sobre Doadores de Grupo CH-CH/genética , Fosfatidilgliceróis/química , Ligação Proteica , Domínios Proteicos , Estrutura Secundária de Proteína , Protoclorifilida/química , Protoclorifilida/metabolismo , Proteínas Recombinantes/química , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Especificidade por Substrato
14.
Planta ; 245(4): 807-817, 2017 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-28032259

RESUMO

MAIN CONCLUSION: The quinone reductase NQR and the b-type cytochrome AIR12 of the plasma membrane are important for the control of reactive oxygen species in the apoplast. AIR12 and NQR are two proteins attached to the plant plasma membrane which may be important for generating and controlling levels of reactive oxygen species in the apoplast. AIR12 (Auxin Induced in Root culture) is a single gene of Arabidopsis that codes for a mono-heme cytochrome b. The NADPH quinone oxidoreductase NQR is a two-electron-transferring flavoenzyme that contributes to the generation of O 2•- in isolated plasma membranes. A. thaliana double knockout plants of both NQR and AIR12 generated more O 2•- and germinated faster than the single mutant affected in AIR12. To test whether NQR and AIR12 are able to interact functionally, recombinant purified proteins were added to plasma membranes isolated from soybean hypocotyls. In vitro NADH-dependent O 2•- production at the plasma membrane in the presence of NQR was reduced upon addition of AIR12. Electron donation from semi-reduced menadione to AIR12 was shown to take place. Biochemical analysis showed that purified plasma membrane from soybean hypocotyls or roots contained phylloquinone and menaquinone-4 as redox carriers. This is the first report on the occurrence of menaquinone-4 in eukaryotic photosynthetic organisms. We propose that NQR and AIR12 interact via the quinone, allowing an electron transfer from cytosolic NAD(P)H to apoplastic monodehydroascorbate and control thereby the level of reactive oxygen production and the redox state of the apoplast.


Assuntos
Proteínas de Arabidopsis/metabolismo , Membrana Celular/metabolismo , Grupo dos Citocromos b/metabolismo , NAD(P)H Desidrogenase (Quinona)/metabolismo , Superóxidos/metabolismo , Arabidopsis/metabolismo , Arabidopsis/fisiologia , Proteínas de Arabidopsis/fisiologia , Linhagem Celular , Membrana Celular/enzimologia , Grupo dos Citocromos b/fisiologia , Técnicas de Silenciamento de Genes , Germinação/fisiologia , NAD(P)H Desidrogenase (Quinona)/fisiologia , Oxirredução , Espécies Reativas de Oxigênio/metabolismo , Soja/metabolismo , Soja/fisiologia
15.
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
16.
Biochim Biophys Acta ; 1864(12): 1757-1764, 2016 12.
Artigo em Inglês | MEDLINE | ID: mdl-27693048

RESUMO

Light-dependent protochlorophyllide oxidoreductase (POR, E.C. 1.3.1.33) is a plant enzyme that directly needs light to conduct a biochemical reaction. In the present paper we confirmed that POR forms large oligomers in solution before binding of substrates. We carried out the research using different techniques: cross-linking, native gel electrophoresis and FRET measurements. Mass spectrometry analysis of the cross-link products provided the first structural data about the organisation of the oligomer of POR. The results indicated that the catalytic motifs of the adjacent subunits become close to each other upon binding of substrates. Moreover, we identified two mutations of POR that disturbed its oligomerisation properties: Δ85-88 and Δ240-270. Additionally, a complete loss of the catalytic activity was observed for the following mutations: Δ189-194, Δ240-270, Δ318-331 and Δ392-393.


Assuntos
Proteínas de Arabidopsis/química , Oxirredutases atuantes sobre Doadores de Grupo CH-CH/química , Arabidopsis/enzimologia , Arabidopsis/genética , Proteínas de Arabidopsis/genética , Proteínas de Arabidopsis/metabolismo , Domínio Catalítico , Reagentes para Ligações Cruzadas , Transferência Ressonante de Energia de Fluorescência , Espectrometria de Massas , Modelos Moleculares , Mutagênese Sítio-Dirigida , Oxirredutases atuantes sobre Doadores de Grupo CH-CH/genética , Oxirredutases atuantes sobre Doadores de Grupo CH-CH/metabolismo , Multimerização Proteica , Estrutura Quaternária de Proteína , Proteínas Recombinantes de Fusão/química , Proteínas Recombinantes de Fusão/genética , Proteínas Recombinantes de Fusão/metabolismo
17.
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
18.
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
19.
Physiol Plant ; 157(2): 147-60, 2016 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-27174597

RESUMO

In this study, 25 accessions of Arabidopsis thaliana originating from a variety of climate conditions were grown under controlled circumstances of different light intensity and temperature. The accessions were analyzed for prenyllipids content and composition, as well as expression of the genes involved in tocochromanol biosynthesis (vte1-5). It was found that the applied conditions did not strongly affect total tocochromanols content and there was no apparent correlation of the tocochromanol content with the origin of the accessions. However, the presented results indicate that the temperature, more than the light intensity, affects the expression of the vte1-5 genes and the content of some prenyllipids. An interesting observation was that under low growth temperature, the hydroxy-plastochromanol (PC-OH) to plastochromanol (PC) ratio was considerably increased regardless of the light intensity in most of the accessions. PC-OH is known to be formed as a result of singlet oxygen stress, therefore this observation indicates that the singlet oxygen production is enhanced under low temperature. Unexpectedly, the highest increase in the PC-OH/PC ratio was found for accessions originating from cold climate (Shigu, Krazo-1 and Lov-5), even though such plants could be expected to be more resistant to low temperature stress.


Assuntos
Antioxidantes/metabolismo , Arabidopsis/fisiologia , Cromanos/metabolismo , Regulação da Expressão Gênica de Plantas , Antioxidantes/análise , Arabidopsis/genética , Arabidopsis/efeitos da radiação , Proteínas de Arabidopsis , Cromanos/análise , Temperatura Baixa , Geografia , Luz , Lipídeos/biossíntese , Lipídeos/química , Prenilação , Oxigênio Singlete/metabolismo , Temperatura
20.
Environ Pollut ; 213: 957-965, 2016 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-27060280

RESUMO

In the present study we analyze the effect of seed treatment by a range of nano-TiO2 concentrations on the growth of Arabidopsis thaliana plants, on the vitamin E content and the expression of its biosynthetic genes, as well as activity of antioxidant enzymes and lipid peroxidation. To conduct the mechanistic analysis of nano-TiO2 on plants growth and antioxidant status we applied nanoparticles concentrations that are much higher than those reported in the environment. We find that as the concentration of nano-TiO2 increases, the biomass, and chlorophyll content in 5-week-old Arabidopsis thaliana plants decrease in a concentration dependent manner. In opposite, higher nano-TiO2 concentration enhanced root growth. Our results indicate that a high concentration of nano-TiO2 induces symptoms of toxicity and elevates the antioxidant level. We also find that the expression levels of tocopherol biosynthetic genes were either down- or upregulated in response to nano-TiO2. Thermoluminescence analysis shows that higher nano-TiO2 concentrations cause lipid peroxidation. To the best of our knowledge, this is the first report concerning the effect of nano-TiO2 on vitamin E status in plants. We conclude that nano-TiO2 affects the antioxidant response in Arabidopsis thaliana plants. This could be an effect of a changes in vitamin E gene expression that is diminished under lower tested nano-TiO2 concentrations and elevated under 1000 µg/ml.


Assuntos
Antioxidantes/metabolismo , Arabidopsis/efeitos dos fármacos , Poluentes Ambientais/farmacologia , Peroxidação de Lipídeos/efeitos dos fármacos , Nanopartículas , Titânio/farmacologia , Vitamina E/metabolismo , Arabidopsis/crescimento & desenvolvimento , Arabidopsis/metabolismo , Biomassa , Clorofila/metabolismo , Relação Dose-Resposta a Droga , Poluentes Ambientais/análise , Poluentes Ambientais/toxicidade , Genes de Plantas , Nanopartículas/toxicidade , Raízes de Plantas/efeitos dos fármacos , Raízes de Plantas/crescimento & desenvolvimento , Raízes de Plantas/metabolismo , Sementes/efeitos dos fármacos , Sementes/metabolismo , Titânio/análise , Titânio/toxicidade , Vitamina E/biossíntese , Vitamina E/genética
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