RESUMO
The applications of nanoparticles continue to expand into areas as diverse as medicine, bioremediation, cosmetics, pharmacology and various industries, including agri-food production. The widespread use of nanoparticles has generated concerns given the impact these nanoparticles - mostly metal-based such as CuO, Ag, Au, CeO2, TiO2, ZnO, Co, and Pt - could be having on plants. Some of the most studied variables are plant growth, development, production of biomass, and ultimately oxidative stress and photosynthesis. A systematic appraisal of information about the impact of nanoparticles on these processes is needed to enhance our understanding of the effects of metallic nanoparticles and oxides on the structure and function on the plant photosynthetic apparatus. Most nanoparticles studied, especially CuO and Ag, had a detrimental impact on the structure and function of the photosynthetic apparatus. Nanoparticles led to a decrease in concentration of photosynthetic pigments, especially chlorophyll, and disruption of grana and other malformations in chloroplasts. Regarding the functions of the photosynthetic apparatus, nanoparticles were associated with a decrease in the photosynthetic efficiency of photosystem II and decreased net photosynthesis. However, CeO2 and TiO2 nanoparticles may have a positive effect on photosynthetic efficiency, mainly due to an increase in electron flow between the photosystems II and I in the Hill reaction, as well as an increase in Rubisco activity in the Calvin and Benson cycle. Nevertheless, the underlying mechanisms are poorly understood. The future mechanistic work needs to be aimed at characterizing the enhancing effect of nanoparticles on the active generation of ATP and NADPH, carbon fixation and its incorporation into primary molecules such as photo-assimilates.
Assuntos
Nanopartículas Metálicas/efeitos adversos , Fotossíntese/efeitos dos fármacos , Clorofila/metabolismo , Cloroplastos/efeitos dos fármacos , Transporte de Elétrons/efeitos dos fármacos , Estresse Oxidativo/efeitos dos fármacos , Complexo de Proteína do Fotossistema II/efeitos dos fármacos , Transpiração Vegetal/efeitos dos fármacos , Titânio/efeitos adversosRESUMO
BACKGROUND: The photosynthetic apparatus is targeted by various herbicides, including several amides such as diuron and linuron. Considering the need for the discovery of new active ingredients to cope with weed resistance, the synthesis of a series of trifluoromethyl aryl amides is herein described whose inhibitory properties were assessed in vitro on the photosynthetic electron transport chain, and in vivo on the growth of a model cyanobacterial strain. Theoretical studies were also carried out. RESULTS: Starting with 1-fluoro-2-nitro-4-(trifluoromethyl) benzene, the preparation of the amides was achieved via a three-step sequence, namely nucleophilic aromatic substitution, reduction with SnCl2 /HCl, and acylation reactions. The measurement of ferricyanide reduction by functionally intact spinach chloroplasts showed that several derivatives are capable of inhibiting the photosynthetic apparatus. The most active amides presented IC50 values close to 1 µmol L-1 , and showed the presence of a 4-bromophenyl group as a common structural feature. The addition of these brominated amides to the culture medium of a model cyanobacterial strain, Synechococcus elongatus PCC 6301, caused various degrees of growth inhibition. Theoretical studies (molecular modeling and quantitative structure-activity relationship) of all amides and their comparison with some known herbicides confirmed these experimental findings and provided more in-depth information about the possible molecular target of these compounds. CONCLUSION: Trifluoromethyl amides herein described, which were shown to act at the PSII level, may represent a novel scaffold to be exploited aiming at the development of new active ingredients for weed control. © 2017 Society of Chemical Industry.
Assuntos
Herbicidas/farmacologia , Fotossíntese/efeitos dos fármacos , Cloroplastos/efeitos dos fármacos , Transporte de Elétrons , Herbicidas/síntese química , Herbicidas/toxicidade , Modelos Moleculares , Relação Quantitativa Estrutura-Atividade , Spinacia oleracea/efeitos dos fármacos , Synechococcus/efeitos dos fármacos , Controle de Plantas DaninhasRESUMO
Mangrove sites are constantly under tidal regimes, where there is variation of dissolved oxygen and saline content in water. This study evaluated the effects of varying salinity in Avicennia schaueriana, an abundant species in the sea-mangrove-river interface. Seedlings of A. schaueriana were harvested at the riverbank and placed in different saline and nutrient solutions in a greenhouse in order to simulate a saline flow. After 7 acclimatization days, plants were exposed to the following saline concentrations: 0, 50, 170 and 250mM NaCl, for a period of 30 days. After this, leaf gas exchange, chlorophyll a fluorescence, Falker chlorophyll index, leaf ultrastructure and micromorphology were evaluated. The highest saline concentration affected mainly the CO2 assimilation, internal CO2 concentration and the intrinsic efficiency of water use. The chlorophyll a fluorescence and Falker index were not significantly affected by any of the saline conditions, however chloroplast was damaged. Concomitantly, leaf salt glands clearly evidenced a higher salt secretion, when plants were submitted to the greatest saline concentration. The results indicated that A. schaueriana tolerates different salt concentration in the mangrove and excretes salt excess by salt gland, and this can attenuate the saline stress. However, when exposed to longer periods of higher salt fluxes the plant growth can be affected.
Assuntos
Aclimatação/efeitos dos fármacos , Avicennia/efeitos dos fármacos , Fotossíntese/efeitos dos fármacos , Folhas de Planta/efeitos dos fármacos , Cloreto de Sódio/farmacologia , Áreas Alagadas , Animais , Avicennia/crescimento & desenvolvimento , Avicennia/fisiologia , Clorofila/metabolismo , Clorofila A , Cloroplastos/efeitos dos fármacos , Cloroplastos/metabolismo , Relação Dose-Resposta a Droga , Folhas de Planta/crescimento & desenvolvimento , Folhas de Planta/fisiologia , Rios/química , Salinidade , Plântula/efeitos dos fármacos , Plântula/crescimento & desenvolvimento , Plântula/fisiologiaRESUMO
There is a very effective cross-talk between signals triggered by reactive oxygen species and hormonal responses in plants, activating proteins/enzymes likely to be involved in stress tolerance. Abscisic acid (ABA) is known as a stress hormone that takes part in the integration of signals. This work aimed to characterize the biochemical response and ultrastructural changes induced by cadmium (Cd) in the Micro-Tom (MT) sitiens ABA-deficient mutant (sit) and its wild-type (MT) counterpart. MT and sit plants were grown over a 96-h period in the presence of Cd (0, 10, and 100 µM CdCl2). The overall results indicated increases in lipid peroxidation, hydrogen peroxide content and in the activities of the key antioxidant enzymes such as catalase, glutathione reductase, and ascorbate peroxidase in both genotypes. On the other hand, no alteration was observed in chlorophyll content, while the activity of another antioxidant enzyme, superoxide dismutase, remained constant or even decreased in the presence of Cd. Roots and shoots of the sit mutant and MT were analyzed by light and transmission electron microscopy in order to characterize the structural changes caused by the exposure to this metal. Cd caused a decrease in intercellular spaces in shoots and a decrease in cell size in roots of both genotypes. In leaves, Cd affected organelle shape and internal organization of the thylakoid membranes, whereas noticeable increase in the number of mitochondria and vacuoles in MT and sit roots were observed. These results add new information that should help unravel the relative importance of ABA in regulating the cell responses to stressful conditions induced by Cd apart from providing the first characterization of this mutant to oxidative stress.
Assuntos
Ácido Abscísico/metabolismo , Cádmio/toxicidade , Genes de Plantas , Mutação/genética , Solanum lycopersicum/genética , Solanum lycopersicum/fisiologia , Estresse Fisiológico/efeitos dos fármacos , Biomassa , Catalase/metabolismo , Clorofila/metabolismo , Cloroplastos/efeitos dos fármacos , Cloroplastos/metabolismo , Cloroplastos/ultraestrutura , Peroxidação de Lipídeos/efeitos dos fármacos , Solanum lycopersicum/efeitos dos fármacos , Malondialdeído/metabolismo , Meristema/citologia , Meristema/efeitos dos fármacos , Meristema/metabolismo , Folhas de Planta/efeitos dos fármacos , Folhas de Planta/metabolismo , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Brotos de Planta/efeitos dos fármacos , Brotos de Planta/metabolismo , Superóxido Dismutase/metabolismoRESUMO
Potassium is one of the three main mineral nutrients, and is vital for leaf growth and the quality of tobacco (Nicotiana tabacum) plants. In recent years, the isobaric tags for relative and absolute quantitation (iTRAQ) method has been one of the most popular techniques for quantitative proteomic analysis. In this study, we used iTRAQ to compare protein abundances in the roots of control and low potassium-treated tobacco seedlings, and found that 108 proteins were differentially expressed between the two treatments. Of these, 34 were upregulated and 74 were downregulated, and 39 (36%) were in the chloroplasts. Kyoto Encyclopedia of Genes and Genomes pathway enrichment results suggested that metabolic pathways were the dominant pathways (10 upregulated and 14 downregulated proteins). Ten proteins involved in the pyruvate metabolism pathway increased their expression levels, and 17 upregulated proteins were enriched in the ribosomes category. To evaluate correlations between protein and gene transcript abundances, the expression patterns of 12 randomly chosen genes were examined. A quantitative real-time polymerase chain reaction revealed that the 12 genes were induced after low potassium treatment for 3, 6, 12, and 24 h. Our results demonstrate that low potassium levels affect protein profiles in tobacco roots.
Assuntos
Regulação da Expressão Gênica de Plantas , Proteínas de Choque Térmico/genética , Nicotiana/efeitos dos fármacos , Proteínas de Plantas/genética , Raízes de Plantas/efeitos dos fármacos , Potássio/farmacologia , Cloroplastos/efeitos dos fármacos , Cloroplastos/genética , Cloroplastos/metabolismo , Perfilação da Expressão Gênica , Ontologia Genética , Proteínas de Choque Térmico/metabolismo , Redes e Vias Metabólicas/efeitos dos fármacos , Redes e Vias Metabólicas/genética , Anotação de Sequência Molecular , Folhas de Planta/efeitos dos fármacos , Folhas de Planta/genética , Folhas de Planta/metabolismo , Proteínas de Plantas/metabolismo , Raízes de Plantas/genética , Raízes de Plantas/metabolismo , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Reação em Cadeia da Polimerase em Tempo Real , Plântula/efeitos dos fármacos , Plântula/genética , Plântula/metabolismo , Nicotiana/genética , Nicotiana/metabolismoRESUMO
In the present study we evaluated the pre-treatment (priming) of Arabidopsis thaliana plants with sodium nitroprusside (SNP), a NO-donor, as an interesting approach for improving plant tolerance to cadmium stress. We focused on the cell redox balance and on the methionine sulfoxide reductases (MSR) family as a key component of such response. MSR catalyse the reversible oxidation of MetSO residues back to Met. Five MSRA genes and nine MSRB genes have been identified in A. thaliana, coding for proteins with different subcellular locations. After treating 20 days-old A. thaliana (Col 0) plants with 100 µM CdCl2, increased protein carbonylation in leaf tissue, lower chlorophyll content and higher levels of reactive oxygen species (ROS) in chloroplasts were detected, together with increased accumulation of all MSR transcripts evaluated. Further analysis showed reduction in guaiacol peroxidase activity (GPX) and increased catalase (CAT) activity, with no effect on ascorbate peroxidase (APX) activity. Pre-exposition of plants to 100 µM SNP before cadmium treatment restored redox balance; this seems to be linked to a better performance of antioxidant defenses. Our results indicate that NO priming may be acting as a modulator of plant antioxidant system by interfering in oxidative responses and by preventing up-regulation of MSR genes caused by metal exposure.
Assuntos
Proteínas de Arabidopsis/metabolismo , Arabidopsis/efeitos dos fármacos , Cádmio/toxicidade , Metionina Sulfóxido Redutases/metabolismo , Nitroprussiato/farmacologia , Regulação para Cima/efeitos dos fármacos , Arabidopsis/genética , Arabidopsis/metabolismo , Proteínas de Arabidopsis/genética , Clorofila/metabolismo , Cloroplastos/efeitos dos fármacos , Cloroplastos/metabolismo , Eletroforese em Gel de Poliacrilamida , Regulação da Expressão Gênica de Plantas/efeitos dos fármacos , Metionina Sulfóxido Redutases/genética , Microscopia de Fluorescência , Família Multigênica , Óxido Nítrico/metabolismo , Doadores de Óxido Nítrico/metabolismo , Doadores de Óxido Nítrico/farmacologia , Nitroprussiato/metabolismo , Oxirredução/efeitos dos fármacos , Peroxidase/metabolismo , Folhas de Planta/efeitos dos fármacos , Folhas de Planta/genética , Folhas de Planta/metabolismo , Carbonilação Proteica/efeitos dos fármacos , Espécies Reativas de Oxigênio/metabolismo , Reação em Cadeia da Polimerase Via Transcriptase ReversaRESUMO
Crop yield reduction due to salinity is a growing agronomical concern in many regions. Increased production of reactive oxygen species (ROS) in plant cells accompanies many abiotic stresses including salinity, acting as toxic and signaling molecules during plant stress responses. While ROS are generated in various cellular compartments, chloroplasts represent a main source in the light, and plastid ROS synthesis and/or elimination have been manipulated to improve stress tolerance. Transgenic tobacco plants expressing a plastid-targeted cyanobacterial flavodoxin, a flavoprotein that prevents ROS accumulation specifically in chloroplasts, displayed increased tolerance to many environmental stresses, including drought, excess irradiation, extreme temperatures and iron starvation. Surprisingly, flavodoxin expression failed to protect transgenic plants against NaCl toxicity. However, when high salt was directly applied to leaf discs, flavodoxin did increase tolerance, as reflected by preservation of chlorophylls, carotenoids and photosynthetic activities. Flavodoxin decreased salt-dependent ROS accumulation in leaf tissue from discs and whole plants, but this decline did not improve tolerance at the whole plant level. NaCl accumulation in roots, as well as increased osmotic pressure and salt-induced root damage, were not prevented by flavodoxin expression. The results indicate that ROS formed in chloroplasts have a marginal effect on plant responses during salt stress, and that sensitive targets are present in roots which are not protected by flavodoxin.
Assuntos
Cloroplastos/metabolismo , Nicotiana/crescimento & desenvolvimento , Folhas de Planta/metabolismo , Espécies Reativas de Oxigênio/metabolismo , Cloreto de Sódio/toxicidade , Estresse Fisiológico/efeitos dos fármacos , Adaptação Fisiológica/efeitos dos fármacos , Cloroplastos/efeitos dos fármacos , Flavodoxina/metabolismo , Íons , Peróxidos Lipídicos/metabolismo , Osmose/efeitos dos fármacos , Folhas de Planta/efeitos dos fármacos , Raízes de Plantas/efeitos dos fármacos , Raízes de Plantas/metabolismo , Plantas Geneticamente Modificadas , Plastídeos/efeitos dos fármacos , Plastídeos/metabolismo , Salinidade , Nicotiana/efeitos dos fármacosRESUMO
Rare earth elements such as lanthanum (La) have been used as agricultural inputs in some countries in order to enhance yield and improve crop quality. However, little is known about the effect of La on the growth and structure of soybean, which is an important food and feed crop worldwide. In this study, bioaccumulation of La and its effects on the growth and mitotic index of soybean was evaluated. Soybean plants were exposed to increasing concentrations of La (0, 5, 10, 20, 40, 80, and 160 µM) in nutrient solution for 28 days. Plant response to La was evaluated in terms of plant growth, nutritional characteristics, photosynthetic rate, chlorophyll content, mitotic index, modifications in the ultrastructure of roots and leaves, and La mapping in root and shoot tissues. The results showed that the roots of soybean plants can accumulate sixty-fold more La than shoots. La deposition occurred mainly in cell walls and in crystals dispersed in the root cortex and in the mesophyll. When La was applied, it resulted in increased contents of some essential nutrients (i.e., Ca, P, K, and Mn), while Cu and Fe levels decreased. Moreover, low La concentrations stimulated the photosynthetic rate and total chlorophyll content and lead to a higher incidence of binucleate cells, resulting in a slight increase in roots and shoot biomass. At higher La levels, soybean growth was reduced. This was caused by ultrastructural modifications in the cell wall, thylakoids and chloroplasts, and the appearance of c-metaphases.
Assuntos
Glycine max/efeitos dos fármacos , Lantânio/farmacologia , Parede Celular/efeitos dos fármacos , Parede Celular/metabolismo , Parede Celular/ultraestrutura , Clorofila/metabolismo , Cloroplastos/efeitos dos fármacos , Cloroplastos/ultraestrutura , Índice Mitótico , Fotossíntese/efeitos dos fármacos , Folhas de Planta/efeitos dos fármacos , Folhas de Planta/metabolismo , Folhas de Planta/ultraestrutura , Raízes de Plantas/efeitos dos fármacos , Raízes de Plantas/crescimento & desenvolvimento , Raízes de Plantas/metabolismo , Raízes de Plantas/ultraestrutura , Brotos de Planta/efeitos dos fármacos , Brotos de Planta/crescimento & desenvolvimento , Brotos de Planta/metabolismo , Glycine max/crescimento & desenvolvimento , Glycine max/metabolismo , Glycine max/ultraestruturaRESUMO
Pb is a metal which is highly toxic to plants and animals, including humans. High concentrations of Pb have been observed in beans of T. cacao, as well as in its products. In this work, we evaluated the molecular, biochemical, and ultrastructural alterations in mature leaves and primary roots of seedlings of two progenies of T. cacao, obtained from seed germination in different concentrations of Pb (0, 0.05, 0.1, 0.2, 0.4, 0.8 g L(-1)), in the form of Pb(NO3)2. The progenies resulted from self-fertilization of Catongo and a cross of CCN-10 x SCA-6. The Pb, supplied via seminal, caused alterations in the ultrastructures of the mesophyll cells and in the amount of starch grains in the chloroplasts. The dosage of substances reactive to thiobarbituric acid showed that Pb induced lipid peroxidation. The activity of guaiacol peroxidases and the expression of genes associated to synthetase of phytochelatin, SODcyt and PER increased in response to Pb. In addition, there was alteration in the expression of stress-related proteins. The progeny of CCN-10 x SCA-6 was more tolerant to Pb stress when compared to Catongo, since: (i) it accumulated more Pb in the roots, preventing its translocation to the shoot; (ii) it presented higher activity of peroxidases in the roots, which are enzymes involved in the elimination of excess of reactive oxygen species; and (iii) increased expression of the gene in the phytochelatin biosynthesis route. The results of the proteomic analysis were of paramount importance to differentiate the defense mechanisms used by both progenies of T. cacao.
Assuntos
Cacau/efeitos dos fármacos , Cacau/ultraestrutura , Chumbo/toxicidade , Plântula/efeitos dos fármacos , Plântula/ultraestrutura , Cacau/genética , Cloroplastos/efeitos dos fármacos , Cloroplastos/genética , Cloroplastos/ultraestrutura , Regulação da Expressão Gênica de Plantas/efeitos dos fármacos , Regulação da Expressão Gênica de Plantas/genética , Peroxidação de Lipídeos/efeitos dos fármacos , Peroxidação de Lipídeos/genética , Estresse Oxidativo/efeitos dos fármacos , Estresse Oxidativo/genética , Peroxidase/genética , Fitoquelatinas/efeitos dos fármacos , Folhas de Planta/efeitos dos fármacos , Folhas de Planta/genética , Folhas de Planta/ultraestrutura , Raízes de Plantas/efeitos dos fármacos , Raízes de Plantas/genética , Raízes de Plantas/ultraestrutura , Plântula/genética , Autofertilização/efeitos dos fármacos , Autofertilização/genética , Poluentes do Solo/toxicidadeRESUMO
The effect of ultraviolet (UV) radiation and copper (Cu) on apical segments of Pterocladiella capillacea was examined under two different conditions of radiation, PAR (control) and PAR+UVA+UVB (PAR+UVAB), and three copper concentrations, ranging from 0 (control) to 0.62, 1.25 and 2.50 µm. Algae were exposed in vitro to photosynthetically active radiation (PAR) at 70 µmol photons m(-2) s(-1) , PAR + UVB at 0.35 W m(-2) and PAR +UVA at 0.70 W m(-2) during a 12-h photocycle for 3 h each day for 7 days. The effects of radiation and copper on growth rates, content of photosynthetic pigments and photosynthetic performance were analyzed. In addition, samples were processed for light and transmission electron microscopy. The content of photosynthetic pigments decreased after exposure to radiation and Cu. Compared with PAR radiation and copper treatments modified the kinetics patterns of the photosynthesis/irradiance curve. The treatments also caused changes in the ultrastructure of cortical and subcortical cells, including increased cell wall thickness and accumulation of plastoglobuli, as well as changes in the organization of chloroplasts. The results indicate that the synergistic interaction between UV radiation and Cu in P. capillacea, led to the failure of protective mechanisms and causing more drastic changes and cellular imbalances.