RESUMEN
Five new brassinosteroid analogues were synthetized from 3ß-acetoxy-23,24-dinorchol-4-en-22-oic acid. All the obtained compound showed significant activity in the Rice Lamina Inclination Test. Interestingly the effects of the methyl ester of 3ß-hydroxy-6-oxo-23,24-dinorcholan-22-oic acid (14) at concentrations of 1â¯×â¯10-7 and 1â¯×â¯10-6 M proved to be higher than those produced by brassinolide. In silico Molecular Docking and Induced fit docking (IFD) simulations for the compounds with the highest biological activity data were carried out to investigate the binding mode interactions into the brassinolide-binding groove which revealed that the compound 14 had high binding energy values and a good affinity.
Asunto(s)
Brasinoesteroides , Ésteres , Brasinoesteroides/farmacología , Simulación del Acoplamiento Molecular , Factores de Crecimiento NerviosoRESUMEN
Nickel (Ni) excess often generates oxidative stress in chloroplasts, causing redox imbalance, membrane damage and negative impacts on biomass. 24-Epibrassinolide (EBR) is a plant growth regulator of great interest to the scientific community because it is a natural molecule extracted from plants, is biodegradable and environmentally friendly. This study aimed to determine whether EBR can improve ionic homeostasis, antioxidant enzymes, PSII efficiency and biomass by evaluating nutritional, physiological, biochemical and morphological responses of soybean plants subjected to Ni excess. The experiment used four randomized treatments, with two Ni concentrations (0 and 200 µm Ni, described as -Ni2+ and +Ni2+ , respectively) and two concentrations of EBR (0 and 100 nm EBR, described as -EBR and +EBR, respectively). In general, Ni had deleterious effects on chlorophyll fluorescence and gas exchange. In contrast, EBR enhanced the effective quantum yield of PSII photochemistry (15%) and electron transport rate (19%) due to upregulation of SOD, CAT, APX and POX. Exogenous EBR application promoted significant increases in biomass, and these results were explained by improved nutrient content and ionic homeostasis, as demonstrated by increased Ca2+ /Ni2+ , Mg2+ /Ni+2 and Mn2+ /Ni2+ ratios.
Asunto(s)
Glycine max , Complejo de Proteína del Fotosistema II , Reguladores del Crecimiento de las Plantas , Antioxidantes/metabolismo , Biomasa , Brasinoesteroides/farmacología , Clorofila/metabolismo , Glycine max/metabolismo , Homeostasis , Níquel/farmacología , Oxidación-Reducción , Fotosíntesis , Complejo de Proteína del Fotosistema II/metabolismoRESUMEN
The synthesis and biological evaluation of brassinosteroids (BRs) analogs with chemical modification in the side alkyl chain is a matter of current interest. Recently, a series of BR analogs with phenyl or benzoate groups in the alkyl chain have been reported. The effect of substitution in the aromatic ring on the biological activities of these new analogs has been evaluated, and the results suggest that the bioactivity is enhanced by substitution with an F atom. In this context, we have synthesized, characterized, and evaluated a series of new analogs of 23,24-bisnorcholenic type in which the benzoate group at the C-22 position is substituted with an F atom at "ortho or para" positions. Plant growth-promoting activities were evaluated by using the rice lamina inclination test and bean second internode biotest. The results obtained with both bioassays indicate that the compound with an F atom in the para position on the aromatic ring is the most active BR analog and in some cases is even more active than brassinolide. The docking study confirmed that compounds with an F atom adopt an orientation similar to that predicted for brassinolide, and the F atom in the "para" position generates an extra hydrogen bond in the predicted binding position.
Asunto(s)
Benzoatos , Brasinoesteroides , Brasinoesteroides/farmacología , Simulación del Acoplamiento Molecular , Axones , BioensayoRESUMEN
Cowpea (Vigna unguiculata (L.) Walp.) is a legume widely cultivated by small, medium and large producers in several Brazilian regions. However, one of the concerns for the production of cowpea in Brazil in recent years is the low rainfall activity in these regions, which generates the accumulation of salts on the surface. The objective of this work was to evaluate the effects of salt stress on growth parameters and enzyme activity in cowpea plants at different concentrations of brassinosteroids. Experiment was developed in a greenhouse using a completely randomized experimental design in a 3 x 3 factorial scheme. The treatments consisted of three levels of brassinosteroids (0, 3 and 6 µM EBL) and three levels of salt stress (0, 50 and 100 mM NaCl). Growth factors (height, diameter and number of leaves) decreased in the saline condition. With the presence of brassinosteroid the height did not increase, but the number of leaves did, mainly in the saline dosage of 100 mM NaCl. In the variable membrane integrity, brassinosteroid was efficient in both salinity dosages, the same not happening with the relative water content, where the saline condition did not affect the amount of water in the vegetable, with the application of brassino it remained high, decreasing only at dosage 100 mM NaCl. The nitrate reductase enzyme was greatly affected in the root system even with the application of increasing doses of brassino. Therefore, brassinosteroids as a promoter of saline tolerance in cowpea seedlings was positive. The concentration of 3µM of EBL provided the most satisfactory effect in tolerating the deleterious effects of the saline condition. The same cannot be concluded for the concentration of 6µM of EBL that did not promote tolerance to some variables.
Asunto(s)
Fabaceae , Vigna , Brasinoesteroides/metabolismo , Brasinoesteroides/farmacología , Estrés Salino , Cloruro de Sodio/metabolismo , Cloruro de Sodio/farmacología , Vigna/metabolismo , Agua/metabolismoRESUMEN
The metabolism of brassinosteroid leads to structural modifications in the ring skeleton or the side alkyl chain. The esterification and glycosylation at C-3 are the most common metabolic pathways, and it has been suggested that conjugate brassinosteroids are less active or inactive. In this way, plants regulate the content of active brassinosteroids. In this work, the synthesis of brassinosteroid 24-norcholane type analogs conjugated at C-3 with benzoate groups, carrying electron donor and electron attractant substituents on the aromatic ring, is described. Additionally, their growth-promoting activities were evaluated using the Rice Lamina Inclination Test (RLIT) and compared with that exhibited by brassinolide (used as positive control) and non-conjugated analogs. The results indicate that at the lowest tested concentrations (10-8-10-7 M), all analogs conjugated at C-3 exhibit similar or higher activities than brassinolide, and the diasteroisomers with S configuration at C-22 are the more active ones. Increasing concentration (10-6 M) reduces the biological activities of analogs as compared to brassinolide.
Asunto(s)
Benzoatos/química , Brasinoesteroides/síntesis química , Oryza/efectos de los fármacos , Reguladores del Crecimiento de las Plantas/síntesis química , Benzoatos/farmacología , Brasinoesteroides/química , Brasinoesteroides/farmacología , Relación Dosis-Respuesta a Droga , Conformación Molecular , Oryza/metabolismo , Reguladores del Crecimiento de las Plantas/química , Reguladores del Crecimiento de las Plantas/farmacología , EstereoisomerismoRESUMEN
Brassinosteroids (BRs) are plant hormones that play an essential role in plant development and have the ability to protect plants against various environmental stresses, such as low and high temperature, drought, heat, salinity, heavy metal toxicity, and pesticides. Mitigation of stress effects are produced through independent mechanisms or by interaction with other important phytohormones. However, there are few studies in which this property has been reported for BRs analogs. Thus, in this work, the enhancement of drought stress tolerance of A. thaliana was assessed for a series of 2-deoxybrassinosteroid analogs. In addition, the growth-promoting activity in the Rice Lamina Inclination Test (RLIT) was also evaluated. The results show that analog 1 exhibits similar growth activity as brassinolide (BL; used as positive control) in the RLIT bioassay. Interestingly, both compounds increase their activities by a factor of 1.2-1.5 when they are incorporated to polymer micelles formed by Pluronic F-127. On the other hand, tolerance to water deficit stress of Arabidopsis thaliana seedlings was evaluated by determining survival rate and dry weight of seedlings after the recovery period. In both cases, the effect of analog 1 is higher than that exhibited by BL. Additionally, the expression of a subset of drought stress marker genes was evaluated in presence and absence of exogenous applied BRs. Results obtained by qRT-PCR analysis, indicate that transcriptional changes of AtDREBD2A and AtNCED3 genes were more significant in A. thaliana treated with analog 1 in homogeneous solution than in that treated with BL. These changes suggest the activation of alternative pathway in response to water stress deficit. Thus, exogenous application of BRs synthetic analogs could be a potential tool for improvement of crop production under stress conditions.
Asunto(s)
Adaptación Fisiológica/efectos de los fármacos , Arabidopsis/efectos de los fármacos , Arabidopsis/fisiología , Brasinoesteroides/farmacología , Sequías , Reguladores del Crecimiento de las Plantas/farmacología , Estrés Fisiológico , Brasinoesteroides/química , Estructura Molecular , Fenotipo , Desarrollo de la Planta , Reguladores del Crecimiento de las Plantas/química , Plantones/efectos de los fármacos , Plantones/crecimiento & desarrollo , Plantones/metabolismoRESUMEN
Iron (Fe) toxicity is one of the most frequent abiotic stresses in rice, as it affects from 15% to 30% of the total production. Brassinosteroids (BRs), including 24-epibrassinolide (EBR), regulate ion homeostasis and improve the antioxidant system. The aim of this research was to determine whether EBR can contribute to the tolerance of rice plants exposed to Fe toxicity and to evaluate the possible effect on anatomical characteristics, nutrient concentrations, the antioxidant system, and gas exchange. The experiment was randomized with four treatments, two with different concentrations of Fe (250 and 6250 µM, control and toxicity, respectively) and these were either supplied with EBR or not (0 and 10 nM EBR, described as -EBR and +EBR, respectively). Treating plants grown under Fe toxic conditions with EBR caused an 70% increase in root aerenchyma area, compared to plants without steroid treatment. Our results revealed that EBR treatment could mitigate the deleterious effects of Fe toxicity in rice plants, by modulating the aerenchyma area, which contributes to the formation of an oxidative barrier and reduce the Fe mobilization at the root surface. Plants that were exposed to Fe toxic concentrations and treated with EBR showed (1) an increase in the enzyme activities of superoxide dismutase, catalase, ascorbate peroxidase and peroxidase, (2) mitigation of oxidative damage and (3) increased scavenging of reactive oxygen species. Finally, EBR alleviated the negative impacts induced by excess Fe on the net photosynthetic rate and the instantaneous carboxylation efficiency. These benefits were directly related to higher electron transport and stomatal density and indirectly linked to the protection mechanism exercised by the antioxidant enzymes on photosynthetic machinery. We conclude that EBR is able to confer tolerance to Fe toxicity in rice plants.
Asunto(s)
Brasinoesteroides , Oryza , Brasinoesteroides/metabolismo , Brasinoesteroides/farmacología , Catalasa/metabolismo , Hierro , Oryza/metabolismo , Estrés OxidativoRESUMEN
Water deficit is the most limiting abiotic stress to plants because it affects several physiological and biochemical processes. Brassinosteroids, including 24-epibrassinolide (EBR), are steroids that regulate growth and positively act on gas exchange. This research aims to determine whether EBR can attenuate the negative effects of water deficit, revealing possible contributions of this steroid on photosynthetic machinery of young Eucalyptus urophylla plants under water deficit. The experiment had a completely randomized factorial design with two water conditions (control and water deficit) and three levels of EBR (0, 50, and 100 nM EBR). Water deficit caused a decrease in the levels of total chlorophyll and carotenoids, but these photosynthetic pigments increased by 135 and 226%, respectively, in plants sprayed with EBR when compared to the water deficit + 0 nM EBR treatment. Regarding the antioxidant system, 100 nM EBR induced significant increments in superoxide dismutase (42%), catalase (52%), ascorbate peroxidase (147%), and peroxidase (204%). Steroid application in E. urophylla plants exposed to water deficit increased the effective quantum yield of the photosystem II (PSII) photochemistry and electron transport rate. However, interestingly, it decreased the nonphotochemical quenching and relative energy excess at the PSII level, indicating improvements related to PSII efficiency. This research revealed that application of 100 nM EBR attenuated the negative effects caused by water deficit, being explained by the positive repercussions on antioxidant enzyme activities, chloroplastic pigments, PSII efficiency, electron flux, and net photosynthetic rate.
Asunto(s)
Brasinoesteroides , Eucalyptus , Brasinoesteroides/metabolismo , Brasinoesteroides/farmacología , Clorofila , Sequías , Eucalyptus/metabolismo , Homeostasis , Oxidación-Reducción , FotosíntesisRESUMEN
Plants exhibit several restrictions under waterlogging conditions, including stomatal limitations, negative impacts on gas exchange, lower nutrient uptake and reduced growth. 24-epibrassinolide (EBR) is a polyhydroxylated steroid, with the advantages to be a natural and biodegradable molecule, presenting beneficial roles in metabolic and physiological processes. The aim of this research is to investigate whether EBR can protect soybean plants against damage caused by waterlogging and evaluate the responses associated with the root and leaf anatomy, photosynthetic machinery and biomass. This study used a completely randomized factorial design with two water conditions (control and waterlogging) and three concentrations of 24-epibrassinolide (0, 5 and 10 nM EBR). This steroid stimulated the activities of enzymes linked to the antioxidant system and resulted in minor damage to the chloroplast membranes. EBR maximized the efficiency of photosystem II and improved the gas exchange, which was explained by the higher density and index of the stomata in addition to the increased chlorophyll content and electron transport rate. In root structures, EBR mitigated the impact of waterlogging on vascular cylinder and metaxilem, suggesting maintenance and functions of these structures in plants stressed.
Asunto(s)
Brasinoesteroides/farmacología , Glycine max/efectos de los fármacos , Glycine max/metabolismo , Hojas de la Planta/efectos de los fármacos , Hojas de la Planta/metabolismo , Raíces de Plantas/metabolismo , Esteroides Heterocíclicos/farmacología , Biomasa , Fotosíntesis/efectos de los fármacos , Raíces de Plantas/efectos de los fármacosRESUMEN
The quest and design of new brassinosteroids analogs is a matter of current interest. Herein, the effect of short alkyl side chains and the configuration at C22 on the growth-promoting activity of a series of new brassinosteroid 24-norcholan-type analogs have been evaluated by the rice leaf inclination test using brassinolide as positive control. The highest activities were found for triol 3 with a C22(S) configuration and monobenzoylated derivatives. A docking study of these compounds into the active site of the Brassinosteroid Insensitive 1(BRI1)-ligand-BRI1-Associated Receptor Kinase 1 (BAK1) complex was performed using AutoDock Vina, and protein-ligand contacts were analyzed using LigPlot+. The results suggest that the hydrophobic interactions of ligands with the receptor BRI1LRR and hydrogen bonding with BAK1 in the complex are important for ligand recognition. For monobenzoylated derivatives, the absence of the hydrophobic end in the alkyl chain seems to be compensated by the benzoyl group. Thus, it would be interesting to determine if this result depends on the nature of the substituent group. Finally, mixtures of S/R triols 3/4 exhibit activities that are comparable or even better than those found for brassinolide. Thus, these compounds are potential candidates for application in agriculture to improve the growth and yield of plants against various types of biotic and abiotic stress.
Asunto(s)
Proteínas de Arabidopsis/metabolismo , Arabidopsis/crecimiento & desarrollo , Brasinoesteroides/química , Brasinoesteroides/farmacología , Ácidos Cólicos/química , Oryza/crecimiento & desarrollo , Raíces de Plantas/crecimiento & desarrollo , Proteínas Serina-Treonina Quinasas/metabolismo , Arabidopsis/efectos de los fármacos , Arabidopsis/metabolismo , Proteínas de Arabidopsis/química , Simulación del Acoplamiento Molecular , Oryza/efectos de los fármacos , Oryza/metabolismo , Reguladores del Crecimiento de las Plantas/química , Reguladores del Crecimiento de las Plantas/farmacología , Raíces de Plantas/efectos de los fármacos , Raíces de Plantas/metabolismo , Proteínas Serina-Treonina Quinasas/químicaRESUMEN
The exogenous application of plant hormones and their analogues has been exploited to improve crop performance in the field. Protodioscin is a saponin whose steroidal moiety has some similarities to plant steroidal hormones, brassinosteroids. To test the possibility that protodioscin acts as an agonist or antagonist of brassinosteroids or other plant growth regulators, we compared responses of the weed species Bidens pilosa L. to treatment with protodioscin, brassinosteroids, auxins (IAA) and abscisic acid (ABA). Seeds were germinated and grown in agar containing protodioscin, dioscin, brassinolides, IAA and ABA. Root apex respiratory activity was measured with an oxygen electrode. Malondialdehyde (MDA) and antioxidant enzymes activities were assessed. Protodioscin at 48-240 µm inhibited growth of B. pilosa seedlings. The steroidal hormone 24-epibrassinolide (0.1-5 µm) also inhibited growth of primary roots, but brassicasterol was inactive. IAA at higher concentrations (0.5-10.0 µm) strongly inhibited primary root length and fresh weight of stems. ABA inhibited all parameters of seedling growth and also seed germination. Respiratory activity of primary roots (KCN-sensitive and KCN-insensitive) was activated by protodioscin. IAA and ABA reduced KCN-insensitive respiration. The content of MDA in primary roots increased only after protodioscin treatment. All assayed compounds increased APx and POD activity, with 24-epibrassinolide being most active. The activity of CAT was stimulated by protodioscin and 24-epibrassinolide. The results revealed that protodioscin was toxic to B. pilosa through a mechanism not related to plant growth regulator signalling. Protodioscin caused a disturbance in mitochondrial respiratory activity, which could be related to overproduction of ROS and consequent cell membrane damage.
Asunto(s)
Ácido Abscísico/farmacología , Bidens/efectos de los fármacos , Brasinoesteroides/farmacología , Diosgenina/análogos & derivados , Ácidos Indolacéticos/farmacología , Reguladores del Crecimiento de las Plantas/farmacología , Saponinas/farmacología , Esteroides Heterocíclicos/farmacología , Antioxidantes/metabolismo , Bidens/crecimiento & desarrollo , Bidens/metabolismo , Diosgenina/farmacología , Relación Dosis-Respuesta a Droga , Flores/efectos de los fármacos , Flores/crecimiento & desarrollo , Germinación/efectos de los fármacos , Malondialdehído/metabolismo , Proteínas de Plantas/metabolismo , Raíces de Plantas/efectos de los fármacos , Raíces de Plantas/crecimiento & desarrollo , Plantones/efectos de los fármacos , Plantones/crecimiento & desarrolloRESUMEN
Brassinosteroids (BRs) are plant hormones that promote growth in different plant organs and tissues. The structural requirements that these compounds should possess to exhibit this biological activity have been studied. In this work, a series of known BR analogs 5-15, were synthesized starting from hyodeoxycholic acid 4, and maintaining the alkyl side chain as cholic acid or its methyl ester. The growth-promoting effects of brassinolide (1) and synthesized analogs were evaluated by using the rice lamina inclination assay at concentrations ranging from 1 × 10-8-1 × 10-6 M. Our results indicate that in this concentration range the induced bending angle of rice seedlings increases with increasing concentration of BRs. Analysis of the activities, determined at the lowest tested concentration, in terms of BR structures shows that the 2α,3α-dihydroxy-7-oxa-6-ketone moiety existing in brassinolide is required for the plant growing activity of these compounds, as it has been proposed by some structure-activity relationship studies. The effect of compound 8 on cell elongation was assessed by microscopy analysis, and the results indicate that the growth-promoting effect of analog 8 is mainly due to cell elongation of the adaxial sides, instead of an increase on cell number.
Asunto(s)
Brasinoesteroides/síntesis química , Brasinoesteroides/farmacología , Ácido Desoxicólico/química , Reguladores del Crecimiento de las Plantas/síntesis química , Reguladores del Crecimiento de las Plantas/farmacología , Brasinoesteroides/química , Espectroscopía de Resonancia Magnética , Estructura Molecular , Oryza/efectos de los fármacos , Oryza/crecimiento & desarrollo , Reguladores del Crecimiento de las Plantas/química , Plantones/efectos de los fármacos , Plantones/crecimiento & desarrolloRESUMEN
Huanglongbing (HLB) constitutes the most destructive disease of citrus worldwide, yet no established efficient management measures exist for it. Brassinosteroids, a family of plant steroidal compounds, are essential for plant growth, development and stress tolerance. As a possible control strategy for HLB, epibrassinolide was applied to as a foliar spray to citrus plants infected with the causal agent of HLB, 'Candidatus Liberibacter asiaticus'. The bacterial titers were reduced after treatment with epibrassinolide under both greenhouse and field conditions but were stronger in the greenhouse. Known defense genes were induced in leaves by epibrassinolide. With the SuperSAGE technology combined with next generation sequencing, induction of genes known to be associated with defense response to bacteria and hormone transduction pathways were identified. The results demonstrate that epibrassinolide may provide a useful tool for the management of HLB.
Asunto(s)
Brasinoesteroides/farmacología , Citrus/microbiología , Enfermedades de las Plantas/microbiología , Rhizobiaceae/efectos de los fármacos , Citrus/efectos de los fármacos , Hojas de la Planta/microbiologíaRESUMEN
Protein phosphatases with Kelch-like domains (PPKL) are members of the phosphoprotein phosphatases family present only in plants and alveolates. PPKL have been described as positive effectors of brassinosteroid (BR) signaling in plants. Most of the evidence supporting this role has been gathered using one of the four homologs in Arabidopsis (Arabidopsis thaliana), brassinosteroid-insensitive1 suppressor (BSU1). We reappraised the roles of the other three members of the family, BSL1, BSL2, and BSL3, through phylogenetic, functional, and genetic analyses. We show that BSL1 and BSL2/BSL3 belong to two ancient evolutionary clades that have been highly conserved in land plants. In contrast, BSU1-type genes are exclusively found in the Brassicaceae and display a remarkable sequence divergence, even among closely related species. Simultaneous loss of function of the close paralogs BSL2 and BSL3 brings about a peculiar array of phenotypic alterations, but with marginal effects on BR signaling; loss of function of BSL1 is, in turn, phenotypically silent. Still, the products of these three genes account for the bulk of PPKL-related activity in Arabidopsis and together have an essential role in the early stages of development that BSU1 is unable to supplement. Our results underline the functional relevance of BSL phosphatases in plants and suggest that BSL2/BSL3 and BSU1 may have contrasting effects on BR signaling. Given that BSU1-type genes have likely undergone a functional shift and are phylogenetically restricted, we caution that inferences based on these genes to the whole family or to other species may be misleading.
Asunto(s)
Evolución Molecular , Fosfoproteínas Fosfatasas/química , Fosfoproteínas Fosfatasas/genética , Plantas/enzimología , Plantas/genética , Arabidopsis/efectos de los fármacos , Arabidopsis/enzimología , Arabidopsis/genética , Brasinoesteroides/farmacología , Flores/anatomía & histología , Flores/efectos de los fármacos , Regulación de la Expresión Génica de las Plantas/efectos de los fármacos , Genes de Plantas/genética , Mutación/genética , Fenotipo , Filogenia , Proteínas de Plantas/metabolismo , Plantas/efectos de los fármacos , Estructura Terciaria de Proteína , Transducción de Señal/efectos de los fármacos , Transducción de Señal/genética , Fracciones Subcelulares/efectos de los fármacos , Fracciones Subcelulares/enzimologíaRESUMEN
The fresh-water green unicellular alga Haematococcus pluvialis is known to accumulate astaxanthin under stress conditions. In the present study, transcriptional expression of eight genes involved in astaxanthin biosynthesis exposed to EBR (25 and 50 mg/L) was analyzed using qRT-PCR. The results demonstrated that both 25 and 50 mg/L EBR could increase astaxanthin productivity and the eight carotenogenic genes were up-regulated by EBR with different expression profiles. Moreover, EBR25 induction had a greater influence on the transcriptional expression of ipi-1, ipi-2, crtR-B, lyc and crtO (> 5- fold up-regulation) than on psy, pds, bkt; EBR50 treatment had a greater effect on the transcriptional expression of ipi-2, pds, lyc, crtR-B, bkt and crtO than on ipi-1 and psy. Furthermore, astaxanthin biosynthesis under EBR was up-regulated mainly by ipi1Ö¾ and psy at the post-transcriptional level, pds, lyc, crtR-B, bkt and crtO at the transcriptional level and ipi-2 at both levels.
Asunto(s)
Brasinoesteroides/farmacología , Carotenoides/biosíntesis , Chlorophyta/genética , Reguladores del Crecimiento de las Plantas/farmacología , ARN Mensajero/metabolismo , Esteroides Heterocíclicos/farmacología , Análisis de Varianza , Carotenoides/genética , Chlorophyta/citología , ARN Mensajero/genética , Reacción en Cadena en Tiempo Real de la Polimerasa , Transcripción Genética , Xantófilas/biosíntesisRESUMEN
Diosgenin, two synthetic analogs of brassinosteroids, testosterone and dl-α-tocopherol were covalently linked to synthetic water-soluble N,O6-partially acetylated chitosan, for their controlled release. Drug linking was confirmed by FTIR spectroscopy and proton NMR. Conjugates were also characterized by differential scanning calorimetry and wide-angle X-ray diffraction. These conjugates formed self-assembled nanoparticles in aqueous solution with particle sizes ranging from 197 to 358 nm and drug contents between 11.8 and 56.4% (w/w). Spherical 30-60 nm nanoparticles were observed by scanning electron microscopy and transmission electron microscopy upon drying. In vitro release studies performed at acid pH indicated a drug release dependence on substitution degree and particle sizes. Almost constant release rates were observed during the first 6-8h. Brassinosteroids-modified nanoparticles showed good agrochemical activity in radish seeds bioassay at 10(-1) to 10(-4) mg mL(-1). Tocopheryl-modified nanoparticles exhibited radical scavenging activity in DPPH test.
Asunto(s)
Brasinoesteroides/química , Quitosano/química , Portadores de Fármacos/química , Interacciones Hidrofóbicas e Hidrofílicas , Nanopartículas/química , Tocoferoles/química , Acetilación , Compuestos de Bifenilo/química , Brasinoesteroides/farmacología , Preparaciones de Acción Retardada , Depuradores de Radicales Libres/química , Depuradores de Radicales Libres/farmacología , Picratos/química , Reguladores del Crecimiento de las Plantas/química , Reguladores del Crecimiento de las Plantas/farmacología , Raphanus/efectos de los fármacos , Raphanus/crecimiento & desarrollo , Tocoferoles/farmacologíaRESUMEN
The fresh-water green unicellular alga Haematococcus pluvialis is known to accumulate astaxanthin under stress conditions. In the present study, transcriptional expression of eight genes involved in astaxanthin biosynthesis exposed to EBR (25 and 50 mg/L) was analyzed using qRT-PCR. The results demonstrated that both 25 and 50 mg/L EBR could increase astaxanthin productivity and the eight carotenogenic genes were up-regulated by EBR with different expression profiles. Moreover, EBR25 induction had a greater influence on the transcriptional expression of ipi-1, ipi-2, crtR-B, lyc and crtO (> 5- fold up-regulation) than on psy, pds, bkt; EBR50 treatment had a greater effect on the transcriptional expression of ipi-2, pds, lyc, crtR-B, bkt and crtO than on ipi-1 and psy. Furthermore, astaxanthin biosynthesis under EBR was up-regulated mainly by ipi1־ and psy at the post-transcriptional level, pds, lyc, crtR-B, bkt and crtO at the transcriptional level and ipi-2 at both levels.
Asunto(s)
Brasinoesteroides/farmacología , Carotenoides/biosíntesis , Chlorophyta/genética , Reguladores del Crecimiento de las Plantas/farmacología , ARN Mensajero/metabolismo , Esteroides Heterocíclicos/farmacología , Análisis de Varianza , Carotenoides/genética , Chlorophyta/citología , Reacción en Cadena en Tiempo Real de la Polimerasa , ARN Mensajero/genética , Transcripción Genética , Xantófilas/biosíntesisRESUMEN
Brassinosteroids (BRs) are plant steroid hormones and, when applied exogenously, they induce physiological responses, including tolerance to heat shock (HS). How endogenous BR content and altered perception of BRs influence thermal tolerance is poorly understood. BR-induced thermotolerance in tomato seedlings with altered BR homeostasis was examined by assessing the survival, ion leakage and lipid peroxidation of seedlings from a BR-deficient mutant (extreme dwarf d(x)), a partially BR-insensitive mutant curl3(-abs) allele (curl3 altered brassinolide sensitivity) and a line overexpressing the Dwarf, BR-biosynthesis gene (35SD). We confirmed that treatment with 1 µM of epi-brassinolide (EBL) induces thermotolerance of wild type seedlings following a HS regime at 45 °C. The curl3(-abs) seedlings had the highest basal tolerance to heat, whereas the EBL-induced thermal tolerance of d(x) seedlings was greatest and responded to lower EBL concentrations. The d(x) and 35SD seedlings had similar thermal tolerance; however, they showed increased signs of oxidative stress. EBL reduced the induction of lipid peroxidation of seedlings after recovery from heat. Highest oxidative stress and peroxidase (POX) activity (EC 1.11.1.7) was in BR-deficient d(x) mutant seedlings. EBL was able of inducing POX activity but not other antioxidant enzymes; however, effects of HS on POX activity of seedlings were absent or less marked. Taking together, results indicate that thermal tolerance is independent of endogenous BR content, but HS-mediated oxidative stress depends on BR levels.