RESUMO
Water deficiency has been recognized as a major abiotic stress that causes losses in maize crops around the world. The maize crop is very important due to the range of products that are derived from this plant. A potential way to reduce the damages caused by water deficiency in maize crops is through the association with plant growth-promoting bacteria (PGPB) and arbuscular mycorrhizal fungi (AMF). To define the mechanisms developed by associative PGPB and AMF in maize that are involved in protection against moderate drought (MD), this study evaluated the biometrical, anatomical, biochemical, and physiological parameters of maize grown under MD and inoculated with different PGPB (Azospirillum brasilense strain Ab-V5 and Bacillus sp. strain ZK) and with AMF. The relative water content did not change in the treatments. The association with ZK increased the shoot:total ratio, total dry weight, maximum quantum yield of photosystem II, vascular cylinder thickness, and vascular cylinder area. The Ab-V5 inoculation led to an increment in root dry weight, the area of metaxylem vessel elements, and nitrate reductase activity. The AMF association did not lead to changes in the measured parameters. The results indicate that the association with PGPB is a relevant alternative to contribute to reducing losses in maize crops under drought. However, AMF is not indicated for this crop under drought.
RESUMO
Deforestation of Atlantic Forest has caused prolonged drought events in the last decades. The need for reforestation is growing, and the development of native seedlings that are more tolerant to drought stress is necessary. A biotechnological tool that improves plant tolerance is the use of plant growth-promoting bacteria (PGPB) as inoculants. Two species of PGPB were inoculated in drought-stressed seedlings of two neotropical tree species that have been used in environmental restoration programs: Cecropia pachystachya and Cariniana estrellensis. Biometrical, physiological, and metabolomic parameters from carbon and nitrogen pathways were evaluated. We found that the PGPB positively influenced photosynthesis and growth parameters in both trees under drought. The enzymes activities, the tricarboxylic acid cycle intermediates, the amino acids, and protein contents were also influenced by the PGPB treatments. The results allowed us to find the specific composition of secondary metabolites of each plant species. This study provides evidence that there is not a single mechanism involved in drought tolerance and that the inoculation with PGPB promotes a broad-spectrum tolerance response in Neotropical trees. The inoculation with PGPB appears as an important strategy to improve drought tolerance in Atlantic Forest native trees and enhance environmental restoration programs' success. MAIN CONCLUSION: The association with plant growth-promoting bacteria improved the tolerance to drought in Neotropical trees through biochemical, physiological, and biometrical parameters. This can enhance the success of forest restoration programs.
Assuntos
Carbono , Secas , Metabolômica , Nitrogênio , Folhas de Planta , Árvores , Carbono/metabolismo , Nitrogênio/metabolismo , Folhas de Planta/metabolismo , Folhas de Planta/microbiologia , Árvores/microbiologia , Árvores/metabolismo , Árvores/fisiologia , Cecropia/metabolismo , Cecropia/fisiologia , Fotossíntese , Estresse Fisiológico , Bactérias/metabolismo , Plântula/microbiologia , Plântula/crescimento & desenvolvimento , Plântula/fisiologia , Plântula/metabolismoRESUMO
Despite the important role played by nitric oxide (NO) in plants subjected to abiotic stress, NO donors application to induce drought tolerance in neotropical tree seedlings has not yet been tested. It is also worth investigating whether NO bioactivity in drought-stressed seedlings could be potentiated by NO donors nanoencapsulation. The aim of the current study is to evaluate the effects of chitosan nanoparticles (NPs) containing S-nitroso-mercaptosuccinic acid (S-nitroso-MSA) on drought-stressed seedlings of neotropical tree species Heliocarpus popayanensis Kunth in comparison to free NO donor and NPs loaded with non-nitrosated MSA. Nanoencapsulation slowed down NO release from S-nitroso-MSA, and nanoencapsulated S-nitroso-MSA yielded 2- and 1.6-fold higher S-nitrosothiol levels in H. popayanensis roots and leaves, respectively, than the free NO donor. S-nitroso-MSA has prevented drought-induced CO2 assimilation inhibition, regardless of nanoencapsulation, but the nanoencapsulated NO donor has induced earlier ameliorative effect. Both NO and MSA have decreased oxidative stress in H. popayanensis roots, but this effect was not associated with antioxidant enzyme induction, with higher seedling biomass, or with proline and glycine betaine accumulation. Nanoencapsulated S-nitroso-MSA was the only formulation capable of increasing leaf relative water content in drought-stressed plants (from 32.3% to 60.5%). In addition, it induced root hair formation (increase by 36.6% in comparison to well-hydrated plants). Overall, results have evidenced that nanoencapsulation was capable of improving the protective effect of S-nitroso-MSA on H. popayanensis seedlings subjected to drought stress, a fact that highlighted the potential application of NO-releasing NPs to obtain drought-tolerant tree seedlings for reforestation programs.
Assuntos
Quitosana , Plântula , Secas , Óxido Nítrico , Doadores de Óxido Nítrico/farmacologia , Fotossíntese , Folhas de PlantaRESUMO
MAIN CONCLUSION: Plant growth-promoting bacteria association improved the enzymatic and non-enzymatic antioxidant pathways in Neotropical trees under drought, which led to lower oxidative damage and enhanced drought tolerance in these trees. Water deficit is associated with oxidative stress in plant cells and may, thus, negatively affect the establishment of tree seedlings in reforestation areas. The association with plant growth-promoting bacteria (PGPB) is known to enhance the antioxidant response of crops, but this strategy has not been tested in seedlings of Neotropical trees. We evaluated the effects of inoculation with two PGPB (Azospirillum brasilense and Bacillus sp.) on the antioxidant metabolism of Cecropia pachystachya and Cariniana estrellensis seedlings submitted to drought. We measured the activity of antioxidant enzymes and the content of non-enzymatic antioxidants in leaves, and biometrical parameters of the seedlings. In both tree species, drought decreased the activity of antioxidant enzymes and the content of non-enzymatic antioxidant compounds. For C. pachystachya, the enzymatic and non-enzymatic pathways were mostly influenced by A. brasilense inoculation, which enhanced ascorbate peroxidase (APX) and superoxide dismutase activities and positively affected the level of non-enzymatic antioxidant compounds. In C. estrellensis, A. brasilense inoculation enhanced APX activity. However, A. brasilense and Bacillus sp. inoculation had more influence on the non-enzymatic pathway, as both bacteria induced a greater accumulation of secondary compounds (such as chlorogenic acid, gallic acid, rutin and synapic acid) compared to that in non-inoculated plants under drought. For both species, PGPB improved biometrical parameters related to drought tolerance, as specific leaf area and leaf-area ratio. Our results demonstrate that PGPB induced antioxidant mechanisms in drought-stressed Neotropical trees, increasing drought tolerance. Thus, PGPB inoculation provides a biotechnological alternative to improve the success of reforestation programmes.
Assuntos
Antioxidantes/metabolismo , Desenvolvimento Vegetal , Estresse Fisiológico , Árvores/metabolismo , Ascorbato Peroxidases/metabolismo , Azospirillum brasilense/metabolismo , Cecropia/metabolismo , Cecropia/microbiologia , Secas , Lecythidaceae/metabolismo , Lecythidaceae/microbiologia , Estresse Oxidativo , Folhas de Planta/metabolismo , Raízes de Plantas/metabolismo , Raízes de Plantas/microbiologia , Plântula/metabolismo , Plântula/microbiologia , Árvores/microbiologiaRESUMO
Polymeric nanoparticles have emerged as carrier systems for molecules that release nitric oxide (NO), a free radical involved in plant stress responses. However, to date, nanoencapsulated NO donors have not been applied to plants under realistic field conditions. Here, we verified the effects of free and nanoencapsulated NO donor, S-nitroso-mercaptosuccinic acid (S-nitroso-MSA), on growth, physiological and biochemical parameters of neotropical tree seedlings kept under full sunlight in the nursery for acclimation. S-nitroso-MSA incorporation into chitosan nanoparticles partially protected the NO donor from thermal and photochemical degradation. The application of nanoencapsulated S-nitroso-MSA in the substrate favoured the growth of seedlings of Heliocarpus popayanensis, a shade-intolerant tree. In contrast, free S-nitroso-MSA or nanoparticles containing non-nitrosated mercaptosuccinic acid reduced photosynthesis and seedling growth. Seedlings of Cariniana estrellensis, a shade-tolerant tree, did not have their photosynthesis and growth affected by any formulations, despite the increase of foliar S-nitrosothiol levels mainly induced by S-nitroso-MSA-loaded nanoparticles. These results suggest that depending on the tree species, nanoencapsulated NO donors can be used to improve seedling acclimation in the nursery.
Assuntos
Aclimatação , Nanopartículas/metabolismo , Doadores de Óxido Nítrico/administração & dosagem , Doadores de Óxido Nítrico/farmacocinética , Óxido Nítrico/farmacocinética , Plântula/metabolismo , Luz Solar , Aclimatação/efeitos dos fármacos , Aclimatação/fisiologia , Aclimatação/efeitos da radiação , Portadores de Fármacos , Composição de Medicamentos , Liberação Controlada de Fármacos , Jardins , Nanopartículas/química , Doadores de Óxido Nítrico/farmacologia , Fotossíntese/fisiologia , Folhas de Planta/efeitos dos fármacos , Folhas de Planta/metabolismo , Folhas de Planta/efeitos da radiação , S-Nitrosotióis/administração & dosagem , S-Nitrosotióis/química , S-Nitrosotióis/farmacocinética , S-Nitrosotióis/farmacologia , Plântula/efeitos dos fármacos , Plântula/crescimento & desenvolvimento , Tiomalatos/administração & dosagem , Tiomalatos/farmacocinética , Tiomalatos/farmacologia , Árvores/efeitos dos fármacos , Árvores/metabolismo , Árvores/efeitos da radiação , Clima TropicalRESUMO
The electrical conductivity test indirectly evaluates cell membrane disorganization by quantifying the electrolytes released into the water after tissue imbibing. The objective of this work was to evaluate methodological variations in the electrical conductivity test, for it to serve as an indicator of low temperature-induced damages and estimate the cold tolerance of bean plants. Cultivar IPR Uirapuru plants were subjected to minimum temperatures of 4°C, 2°C, 0°C, -1°C, -2°C, -3°C, and -4°C for 1 h in a growth chamber under controlled conditions. After the treatment period, the response of plants to cold stress was evaluated by determination of the total protein content, and catalase (CAT) and ascorbate peroxidase (APX) enzymatic activities, and evaluation of photosystem II (Fm/Fv) efficiency and leaf anatomy. These results were compared with those obtained in the electrical conductivity test, which was performed in plants under cold stress as well as under a non-stress environment, with 2, 4, 6, and 8 leaf discs immersed in 30 mL of distilled water for 24 h in BOD, at temperatures of 25°C, 30°C, and 35°C. Analysis of variance was performed using a completely randomized design, and for electrical conductivity, a number of discs × cold stress temperature combinations were used for each soak temperature. The averages were compared using the Turkeys test at 5% and 10% probability. Pearson correlation coefficient (r) between the conductivity averages and other cold stress evaluation data was also performed. The results showed a marked reduction in the ratio (Fv/Fm) only in the treatments at -3°C and -4°C, which indicated tissue death. At temperatures below 0°C, there was a collapse of the leaf blade tissues, and it was not possible to differentiate the palisade parenchyma from the spongy parenchyma in the treatments at -2°C, -3°C, and -4°C. There was an increase in the protein content since the temperature -3°C...(AU)
O teste de condutividade elétrica avalia de forma indireta a desorganização da membrana celular, pela quantificação dos eletrólitos liberados na água após a embebição dos tecidos. Assim, o objetivo do trabalho foi avaliar as variações de metodologias no teste de condutividade elétrica como indicador de danos por temperaturas baixas para estimar a tolerância ao frio de plantas de feijão preto. Dessa forma, as plantas da cultivar IPR Uirapuru foram submetidas às temperaturas mínimas de 4°C, 2°C, 0°C, -1°C, -2°C, -3°C e -4°C, por uma hora, em câmara de crescimento sob condições controladas. Após esse período, a resposta das plantas ao estresse por frio foi avaliada pela determinação do teor de proteínas totais, atividade enzimática da catalase (CAT) e da ascorbato peroxidase (APX), além da avaliação da eficiência do fotossistema II (Fv/Fm) e da anatomia foliar. Esses resultados foram comparados com os obtidos no teste de condutividade elétrica o qual foi realizado nas plantas após o estresse frio e em plantas não estressadas (ambiente) com 2, 4, 6 e 8 discos foliares imersos em 30 ml de água destilada, mantidos por 24 horas em B.O.D nas temperaturas de 25°C, 30°C e 35°C. A análise de variância foi realizada em delineamento inteiramente casualizado, e para condutividade elétrica utilizou-se fatorial número de discos x temperatura de estresse ao frio para cada temperatura de embebição separadamente. As médias foram comparadas pelo teste Tukey a 5 e 10% de probabilidade. Realizou-se a correlação de Pearson (r) entre as médias de condutividade e os demais testes de avaliação do estresse por frio. Nos resultados observou-se acentuada redução da relação (Fv/Fm) apenas nos tratamentos -3°C e -4°C indicando morte dos tecidos. Para temperaturas inferiores a 0°C houve colapso dos tecidos do limbo foliar, não sendo possível diferenciar o parênquima paliçádico do parênquima esponjoso nos tratamentos -2, -3 e -4°C...(AU)
Assuntos
Phaseolus/efeitos adversos , Phaseolus/crescimento & desenvolvimento , Condutividade Elétrica , Resposta ao Choque Frio , Membrana Celular/químicaRESUMO
The electrical conductivity test indirectly evaluates cell membrane disorganization by quantifying the electrolytes released into the water after tissue imbibing. The objective of this work was to evaluate methodological variations in the electrical conductivity test, for it to serve as an indicator of low temperature-induced damages and estimate the cold tolerance of bean plants. Cultivar IPR Uirapuru plants were subjected to minimum temperatures of 4°C, 2°C, 0°C, -1°C, -2°C, -3°C, and -4°C for 1 h in a growth chamber under controlled conditions. After the treatment period, the response of plants to cold stress was evaluated by determination of the total protein content, and catalase (CAT) and ascorbate peroxidase (APX) enzymatic activities, and evaluation of photosystem II (Fm/Fv) efficiency and leaf anatomy. These results were compared with those obtained in the electrical conductivity test, which was performed in plants under cold stress as well as under a non-stress environment, with 2, 4, 6, and 8 leaf discs immersed in 30 mL of distilled water for 24 h in BOD, at temperatures of 25°C, 30°C, and 35°C. Analysis of variance was performed using a completely randomized design, and for electrical conductivity, a number of discs × cold stress temperature combinations were used for each soak temperature. The averages were compared using the Turkeys test at 5% and 10% probability. Pearson correlation coefficient (r) between the conductivity averages and other cold stress evaluation data was also performed. The results showed a marked reduction in the ratio (Fv/Fm) only in the treatments at -3°C and -4°C, which indicated tissue death. At temperatures below 0°C, there was a collapse of the leaf blade tissues, and it was not possible to differentiate the palisade parenchyma from the spongy parenchyma in the treatments at -2°C, -3°C, and -4°C. There was an increase in the protein content since the temperature -3°C...
O teste de condutividade elétrica avalia de forma indireta a desorganização da membrana celular, pela quantificação dos eletrólitos liberados na água após a embebição dos tecidos. Assim, o objetivo do trabalho foi avaliar as variações de metodologias no teste de condutividade elétrica como indicador de danos por temperaturas baixas para estimar a tolerância ao frio de plantas de feijão preto. Dessa forma, as plantas da cultivar IPR Uirapuru foram submetidas às temperaturas mínimas de 4°C, 2°C, 0°C, -1°C, -2°C, -3°C e -4°C, por uma hora, em câmara de crescimento sob condições controladas. Após esse período, a resposta das plantas ao estresse por frio foi avaliada pela determinação do teor de proteínas totais, atividade enzimática da catalase (CAT) e da ascorbato peroxidase (APX), além da avaliação da eficiência do fotossistema II (Fv/Fm) e da anatomia foliar. Esses resultados foram comparados com os obtidos no teste de condutividade elétrica o qual foi realizado nas plantas após o estresse frio e em plantas não estressadas (ambiente) com 2, 4, 6 e 8 discos foliares imersos em 30 ml de água destilada, mantidos por 24 horas em B.O.D nas temperaturas de 25°C, 30°C e 35°C. A análise de variância foi realizada em delineamento inteiramente casualizado, e para condutividade elétrica utilizou-se fatorial número de discos x temperatura de estresse ao frio para cada temperatura de embebição separadamente. As médias foram comparadas pelo teste Tukey a 5 e 10% de probabilidade. Realizou-se a correlação de Pearson (r) entre as médias de condutividade e os demais testes de avaliação do estresse por frio. Nos resultados observou-se acentuada redução da relação (Fv/Fm) apenas nos tratamentos -3°C e -4°C indicando morte dos tecidos. Para temperaturas inferiores a 0°C houve colapso dos tecidos do limbo foliar, não sendo possível diferenciar o parênquima paliçádico do parênquima esponjoso nos tratamentos -2, -3 e -4°C...
Assuntos
Condutividade Elétrica , Membrana Celular/química , Phaseolus/crescimento & desenvolvimento , Phaseolus/efeitos adversos , Resposta ao Choque FrioRESUMO
The inoculation of tree species with plant growth-promoting bacteria (PGPB) has emerged as an important strategy for the acclimation of seedlings by improving plant tolerance to biotic and abiotic stresses. This study aimed to evaluate the effects of inoculation with bacterial species (Azospirillum brasilense - Ab-V5, Bacillus sp., Azomonas sp. and Azorhizophillus sp.) on the growth and physiology of the Neotropical tree species Trema micrantha and Cariniana estrellensis under drought conditions. When associated with Ab-V5 and Azomonas sp., T. micrantha showed increased protein in the leaves, starch in the leaves and roots, photosynthesis, instantaneous carboxylation efficiency and root and shoot dry mass. Moreover, there were reductions in hydrogen peroxide, lipid peroxidation, water potential and proline. In C. estrellensis associated with Ab-V5, higher values of photosynthesis and instantaneous carboxylation efficiency were observed, in addition to higher starch content in the leaves and roots and higher protein content in the leaves; lower hydrogen peroxide and lipid peroxidation contents were also observed. The associations of T. micrantha with Ab-V5 and Azomonas sp. and C. estrellensis with Ab-V5 favored the activation of metabolic processes under drought, leading to greater drought tolerance. This work demonstrates the effects of compatible associations of Neotropical tree and PGPB species and suggests that the identification of compatible PGPB strains can result in tree seedlings with increased tolerance to abiotic stresses, such as drought.
Assuntos
Azospirillum brasilense/metabolismo , Bacillus/metabolismo , Lecythidaceae/fisiologia , Pseudomonadaceae/metabolismo , Plântula/fisiologia , Árvores/fisiologia , Trema/fisiologia , Desidratação , Lecythidaceae/microbiologia , Peroxidação de Lipídeos , Fotossíntese , Folhas de Planta/fisiologia , Proteínas de Plantas/metabolismo , Raízes de Plantas/fisiologia , Prolina/metabolismo , Plântula/microbiologia , Amido/metabolismo , Árvores/microbiologia , Trema/microbiologiaRESUMO
In this study, we prepared, characterized, and performed toxicity analyses of poly(ε-caprolactone) nanocapsules loaded with neem oil. Three formulations were prepared by the emulsion/solvent evaporation method. The nanocapsules showed a mean size distribution around 400 nm, with polydispersity below 0.2 and were stable for 120 days. Cytotoxicity and genotoxicity results showed an increase in toxicity of the oleic acid + neem formulations according to the amount of oleic acid used. The minimum inhibitory concentrations demonstrated that all the formulations containing neem oil were active. The nanocapsules containing neem oil did not affect the soil microbiota during 300 days of exposure compared to the control. Phytotoxicity studies indicated that NC_20 (200 mg of neem oil) did not affect the net photosynthesis and stomatal conductance of maize plants, whereas use of NC_10 (100:100 of neem:oleic acid) and NC_15 (150:50 of neem:oleic acid) led to negative effects on these physiological parameters. Hence, the use of oleic acid as a complement in the nanocapsules was not a good strategy, since the nanocapsules that only contained neem oil showed lower toxicity. These results demonstrate that evaluation of the toxicity of nanopesticides is essential for the development of environmentally friendly formulations intended for applications in agriculture.
Assuntos
Azadirachta/química , Glicerídeos/toxicidade , Nanocápsulas/química , Terpenos/toxicidade , Testes de Toxicidade , Animais , Linhagem Celular , Aberrações Cromossômicas , Ensaio Cometa , Desnitrificação/efeitos dos fármacos , Humanos , Concentração de Íons de Hidrogênio , Concentração Inibidora 50 , Camundongos , Testes de Sensibilidade Microbiana , Mutagênicos/toxicidade , Nanocápsulas/ultraestrutura , Ciclo do Nitrogênio/efeitos dos fármacos , Cebolas/química , Tamanho da Partícula , Fotossíntese/efeitos dos fármacos , Estômatos de Plantas/efeitos dos fármacos , Estômatos de Plantas/fisiologia , Microbiologia do Solo , Eletricidade Estática , Zea mays/efeitos dos fármacos , Zea mays/fisiologiaRESUMO
Few studies have analyzed the strategies of neotropical tree seedlings for absorbing, translocating and assimilating the nitrogen. Here, we compared the nitrogen use strategies of seedlings from six tree species that are native to the Brazilian Atlantic Forest and that belong to different successional groups: Trema micrantha, Heliocarpus popayanensis and Cecropia pachystachya (pioneers), Cariniana estrellensis, Eugenia brasiliensis and Guarea kunthiana (non-pioneers). The effects of cultivating seedlings with nitrate or ammonium on the growth, physiology and nitrogen metabolism were analyzed. Nitrate-grown pioneer species had much higher leaf nitrate reductase activity than non-pioneer ones, but non-pioneer seedlings were also able to use nitrate as a nitrogen source. In addition to this remarkable difference between the groups in the capacity for leaf nitrate assimilation, substantial variations in the nitrogen use strategies were observed within the successional classes. Differently from the other non-pioneers, the canopy species C. estrellensis seemed to assimilate nitrate mainly in the leaves. Morphophysiological analyses showed a gradient of ammonium toxicity response, with E. brasiliensis as the most tolerant species, and T. micrantha and H. popayanensis as the most sensitive ones. Guarea kunthiana showed a relatively low tolerance to ammonium and an unusual high translocation of this cation in the xylem sap. In contrast to the other pioneers, C. pachystachya had a high plasticity in the use of nitrogen sources. Overall, these results suggest that nitrogen use strategies of neotropical tree seedlings were not determined solely by their successional position.
Assuntos
Nitrogênio/metabolismo , Plântula/metabolismo , Árvores/metabolismo , Compostos de Amônio/metabolismo , Transporte Biológico , Brasil , Clima , Ecossistema , Nitrato Redutase/metabolismo , Folhas de Planta/metabolismo , Proteínas de Plantas/metabolismo , Raízes de Plantas/metabolismo , Plântula/fisiologia , Xilema/metabolismoRESUMO
Poly(epsilon-caprolactone) (PCL) nanocapsules have been used as a carrier system for the herbicide atrazine, which is commonly applied to maize. We demonstrated previously that these atrazine containing polymeric nanocapsules were 10-fold more effective in the control of mustard plants (a target species), as compared to a commercial atrazine formulation. Since atrazine can have adverse effects on non-target crops, here we analyzed the effect of encapsulated atrazine on growth, physiological and oxidative stress parameters of soil-grown maize plants (Zea mays L.). One day after the post-emergence treatment with PCL nanocapsules containing atrazine (1 mg mL(-1)), maize plants presented 15 and 21% decreases in maximum quantum yield of photosystem II (PSII) and in net CO2 assimilation rate, respectively, as compared to water-sprayed plants. The same treatment led to a 1.8-fold increase in leaf lipid peroxidation in comparison with control plants. However, all of these parameters were unaffected 4 and 8 days after the application of encapsulated atrazine. These results suggested that the negative effects of atrazine were transient, probably due to the ability of maize plants to detoxify the herbicide. When encapsulated atrazine was applied at a 10-fold lower concentration (0.1 mg mL(-1)), a dosage that is still effective for weed control, no effects were detected even shortly after application. Regardless of the herbicide concentration, neither pre- nor post-emergence treatment with the PCL nanocapsules carrying atrazine resulted in the development of any macroscopic symptoms in maize leaves, and there were no impacts on shoot growth. Additionally, no effects were observed when plants were sprayed with PCL nanocapsules without atrazine. Overall, these results suggested that the use of PCL nanocapsules containing atrazine did not lead to persistent side effects in maize plants, and that the technique could offer a safe tool for weed control without affecting crop growth.
RESUMO
Poly(epsilon-caprolactone) (PCL) nanocapsules have been recently developed as a modified release system for atrazine, an herbicide that can have harmful effects in the environment. Here, the post-emergence herbicidal activity of PCL nanocapsules containing atrazine was evaluated using mustard (Brassica juncea) as target plant species model. Characterization of atrazine-loaded PCL nanocapsules by nanoparticle tracking analysis indicated a concentration of 7.5 x 10(12) particles mL(-1) and an average size distribution of 240.7 nm. The treatment of mustard plants with nanocapsules carrying atrazine at 1 mg mL(-1) resulted in a decrease of net photosynthesis and PSII maximum quantum yield, and an increase of leaf lipid peroxidation, leading to shoot growth inhibition and the development of severe symptoms. Time course analysis until 72 h after treatments showed that nanoencapsulation of atrazine enhanced the herbicidal activity in comparison with a commercial atrazine formulation. In contrast to the commercial formulation, ten-fold dilution of the atrazine-containing nanocapsules did not compromise the herbicidal activity. No effects were observed when plants were treated with nanocapsules without herbicide compared to control leaves sprayed with water. Overall, these results demonstrated that atrazine-containing PCL nanocapsules provide very effective post-emergence herbicidal activity. More importantly, the use of nanoencapsulated atrazine enables the application of lower dosages of the herbicide, without any loss of efficiency, which could provide environmental benefits.
Assuntos
Atrazina/toxicidade , Herbicidas/toxicidade , Mostardeira/efeitos dos fármacos , Nanocápsulas/química , Biomassa , Gases/metabolismo , Estresse Oxidativo/efeitos dos fármacos , Tamanho da Partícula , Complexo de Proteína do Fotossistema II/metabolismo , Folhas de Planta/efeitos dos fármacos , Brotos de Planta/efeitos dos fármacos , Poliésteres/química , Teoria QuânticaRESUMO
JUSTIFICATIVA E OBJETIVOS: A regulação da síntese proteica é essencial para o bom desempenho da função celular; um dos recursos usados no controle desse processo são os microRNAs, pequenos fragmentos de RNA que silenciam o RNA mensageiro. Portanto, mudanças na expressão dessas substâncias estão envolvidas na fisiopatologia de diversas doenças. Dessa forma, estudam-se maneiras de usar os microRNAs como ferramentas diagnósticas e terapêuticas. O objetivo deste estudo foi rever na literatura os microRNAs e suas perspectivas na área médica. CONTEÚDO: A biogênese dos microRNAs e sua aplicação na prática clínica, enfatizando a Oncologia, Psiquiatria e Cardiologia. CONCLUSÃO: Apesar de muitos microRNAs não terem sua função ainda estabelecida, o conhecimento do progresso já feito é fundamental para compreender os avanços terapêuticos e diagnósticos que estão se revelando.
BACKGROUND AND OBJECTIVES: The regulation of protein synthesis is essential for a good cellular function; one way to control this process is through microRNAs, small fragments of RNA which can silence the messenger RNA. Therefore, alterations on the expression of these molecules are involved in the pathophysiology of several diseases. Thus, ways to use microRNAs as diagnostic and therapeutic tools are being studied. The objective of the present study is to review literature on microRNA and its perspectives in medicine. CONTENTS : MicroRNAs biogenesis and its applications in the clinical practice, focusing on Oncology, Psychiatry and Cardiology. CONCLUSION: Even though many microRNAs function is not well established, the knowledge of the progress done is critical to understand the diagnostic and therapeutic advances that are being revealed.
Assuntos
Humanos , Doenças Cardiovasculares , Transtornos Mentais , MicroRNAs/uso terapêutico , NeoplasiasRESUMO
BACKGROUND: Small RNAs (19-24 nt) are key regulators of gene expression that guide both transcriptional and post-transcriptional silencing mechanisms in eukaryotes. Current studies have demonstrated that microRNAs (miRNAs) act in several plant pathways associated with tissue proliferation, differentiation, and development and in response to abiotic and biotic stresses. In order to identify new miRNAs in soybean and to verify those that are possibly water deficit and rust-stress regulated, eight libraries of small RNAs were constructed and submitted to Solexa sequencing. RESULTS: The libraries were developed from drought-sensitive and tolerant seedlings and rust-susceptible and resistant soybeans with or without stressors. Sequencing the library and subsequent analyses detected 256 miRNAs. From this total, we identified 24 families of novel miRNAs that had not been reported before, six families of conserved miRNAs that exist in other plants species, and 22 families previously reported in soybean. We also observed the presence of several isomiRNAs during our analyses. To validate novel miRNAs, we performed RT-qPCR across the eight different libraries. Among the 11 miRNAs analyzed, all showed different expression profiles during biotic and abiotic stresses to soybean. The majority of miRNAs were up-regulated during water deficit stress in the sensitive plants. However, for the tolerant genotype, most of the miRNAs were down regulated. The pattern of miRNAs expression was also different for the distinct genotypes submitted to the pathogen stress. Most miRNAs were down regulated during the fungus infection in the susceptible genotype; however, in the resistant genotype, most miRNAs did not vary during rust attack. A prediction of the putative targets was carried out for conserved and novel miRNAs families. CONCLUSIONS: Validation of our results with quantitative RT-qPCR revealed that Solexa sequencing is a powerful tool for miRNA discovery. The identification of differentially expressed plant miRNAs provides molecular evidence for the possible involvement of miRNAs in the process of water deficit- and rust-stress responses.