Nitrogen fixation of the nodule of soybean is highly sensitive to oxygen deficiency such as provoked by waterlogging of the root system. This study aimed to evaluate the effects of flooding on N ...metabolism in nodules of soybean. Flooding resulted in a marked decrease of asparagine (the most abundant amino acid) and a concomitant accumulation of γ-aminobutyric acid (GABA). Flooding also resulted in a strong reduction of the incorporation of ¹⁵N₂ in amino acids. Nodule amino acids labelled before flooding rapidly lost ¹⁵N during flooding, except for GABA, which initially increased and declined slowly thereafter. Both nitrogenase activity and the expression of nifH and nifD genes were strongly decreased on flooding. Expression of the asparagine synthetase genes SAS1 and SAS2 was reduced, especially the former. Expression of genes encoding the enzyme glutamic acid decarboxylase (GAD1, GAD4, GAD5) was also strongly suppressed except for GAD2 which increased. Almost all changes observed during flooding were reversible after draining. Possible changes in asparagine and GABA metabolism that may explain the marked fluctuations of these amino acids during flooding are discussed. It is suggested that the accumulation of GABA has a storage role during flooding stress.
Photopolymerizable hydrogels based on methacryloyl gelatin (GeIMA) have potential for biomedical applications, due to their high processability, biological activity, and possibility of cell ...encapsulation. However, biomolecule‐based hydrogels have often poor mechanical properties that limit their application. In this work, we prepared hydrogels with enhanced mechanical properties and biological activity by incorporating mats of electrospun polycaprolactone fibers containing GeIMA in GelMA hydrogels. These GelMA hydrogels with electrospun fiber mats were prepared by photopolymerizing either a blend of chopped fiber mats and GelMA or stacking electrospun fiber mats impregnated with GelMA. Cell encapsulation, viability and proliferation were also investigated. Scanning electron microscopy images showed pore walls of lyophilized hydrogels decorated with chopped fiber mats. Mechanical properties of hydrogels containing stacks of electrospun fiber mats were much higher than pure hydrogels. Encapsulated cells within hydrogels were observed to grow faster than in hydrogels with no fiber mats, as an indication that the extracellular matrix‐like texture of the fiber mats within the hydrogels can enhance the biological activity of the materials. The overall results revealed that the tested approaches to prepare hydrogels with electrospun fiber mats can expand the usage of biomolecule‐based hydrogels in biomedical applications.
Arginine (Arg) metabolism is associated with many cellular and developmental processes in plants and proline, nitric oxide (NO) and polyamines (PAs) have a wide range of physiological functions in ...plants, including increased tolerance to environmental stresses. This study aimed to test the hypothesis that Arg spraying would stimulate the synthesis of proline, NO and PAs, reducing the oxidative damage caused by water deficit (WD) and increasing drought tolerance of sugarcane plants. Sugarcane plants were sprayed with water or Arg 1 mM, and subjected to WD by gradual addition of polyethylene glycol (PEG-8000) to the nutrient solution. As references, sugarcane plants were grown in nutrient solution without PEG-8000 and sprayed or not with Arg. Our data indicate that exogenous Arg supply improved leaf gas exchange during water deficit and enhanced the root antioxidative protection of sugarcane plants during the recovery period. Arg supply prevented the proline accumulation induced by water deficit and then the main pathway for proline synthesis is likely through glutamate instead of arginine. Although Arg is a substrate for NO and PAs production, supplying Arg had only slight effects in both NO and PAs levels. The spraying of amino acids capable of reducing the harmful effects of drought, such as Arg, can be an alternative to improve crop growth under field conditions.
•Exogenous Arg supply improved leaf gas exchange during water deficit.•Arg supply enhanced the root antioxidative protection of sugarcane plants during the recovery period.•Proline synthesis was not enhanced by Arg supply.
Due to diverse human activities zinc (Zn) may reach phytotoxic levels in the soil. Here, we evaluated the differential sensibility of three Brazilian tree species from the Fabaceae to increasing soil ...Zn concentrations and its physiological response to cope with excess Zn. A greenhouse experiment was conducted with the species: Mimosa caesalpiniaefolia, Erythrina speciosa and Schizolobium parahyba, and the addition of 0, 200, 400 and 600 mg Zn kg−1 to the soil. Plants were harvested after three months of cultivation, and growth, root symbiosis, biochemical markers and elemental composition were analyzed. Soil Zn addition reduced seedling growth, irrespective of the species, with a strong reduction in M. caesalpiniaefolia. Regarding root symbiosis, in N2-fixing species, nitrogenase activity was reduced by the highest Zn concentrations. Zn addition caused plants nutritional imbalances, mainly in roots. The content of photosynthetic pigments in leaves decreased up to 40%, suggesting that high Zn contents interfered with its biosynthesis, and altered the content of foliar polyamines and free amino acids, depending on the species and the soil Zn concentration. Zn toxicity in M. caesalpiniaefolia plants was observed at available soil Zn concentrations greater than 100 mg kg−1 (DTPA-extractable), being the most sensitive species and E. speciosa was moderately sensitive. S. parahyba was a moderately tolerant species, which seems to be related to polyamines accumulation and to mycorrhizal association. This last species has the potential for revegetation of areas with moderately high soil Zn concentration and for phytostabilization purposes. Future research evaluating the tolerance to multiple metal stress under field conditions should confirm S. parayba suitability in Zn contaminated areas of tropical regions.
•Soil Zn addition reduced growth of seedling of tropical tree species.•Soil Zn caused nutritional imbalances, mainly in roots.•In N2-fixing species high Zn concentrations reduced nitrogenase activity.•Polyamine accumulation may be related to the tolerance to zinc toxicity.•Schizolobium parahyba was a moderately tolerant tree species.
A greenhouse pot experiment was conducted to evaluate the potential of three Brazilian leguminous woody species, Mimosa caesalpiniaefolia, Erythrina speciosa and Schizolobium parahyba, for the ...revegetation of lead- (Pb-) contaminated areas. The response of seedlings to increasing Pb concentrations (0, 250, 500 and 1000 mg kg−1) in the soil was studied. In addition to Pb accumulation and translocation, the following parameters were assessed: chlorophyll, nitrate, ammonia, lipid peroxidation (MDA) and free amino acid content; seedling growth; and nitrogenase activity. No differences were observed in the germination of woody species seeds sown in soils with or without Pb addition. M. caesalpiniaefolia did not show visual symptoms of Pb toxicity, while the other two species demonstrated stress symptoms, including reduced shoot biomass yield, leaf area and height. Biochemical analyses of plant tissues revealed markedly different responses to increasing Pb concentrations, such as changes in foliar soluble amino acid composition in S. parahyba; changes in ammonia and nitrate content in E. speciosa, M. caesalpiniaefolia and S. parahyba; and changes in MDA content in S. parahyba. The levels of chlorophyll a and b and carotenoid were affected in the species studied. For the Nitrogen-fixing (N2-fixing) species E. speciosa, an increase of Pb in the soil affected nodule formation and growth, which led to reduced nitrogenase activity in seedlings. The concentration of Pb in shoots and roots increased with the Pb concentration in soil. However, most of the Pb absorbed accumulated in the roots, and only a small fraction was translocated to aboveground parts. These findings were confirmed by the low bioconcentration factor (BCF) and translocation factor (TF) values for the three species. The tolerance index (TI) values suggested that M. caesalpiniaefolia, a N2-fixing tree, was the species that was most tolerant to high Pb concentrations in soil, while E. speciosa and S. parahyba showed moderate tolerance. Of the three Brazilian native woody species studied, M. caesalpiniaefolia was found to have the highest Pb tolerance and phytostabilisation potential in Pb-contaminated soils.
► Brazilian leguminous woody species were evaluated for the phytoremediation of Pb-contaminated soil. ► We analysed growth, mycorrhisation, biochemical and physiological biomarkers in addition to Pb uptake. ► The tolerance index, translocation factor and bioconcentration factor were determined. ► We found that Pb in the soil had different effects on the tree species studied. ► Mimosa caesalpiniaefolia showed the highest Pb tolerance and phytostabilisation potential.
Phytochemicals are promising therapeutics for various neurodegenerative disorders, including Parkinson’s disease (PD). However, their efficacy, pharmacokinetic properties, and penetration across the ...blood–brain barrier can be improved using delivery systems such as nanoparticles. We reviewed recently published work in which nanoparticles were used to deliver phytochemicals toward PD treatment. The studies show that nanoparticles not only improve the pharmacological effect of the phytochemicals but also enable targeting to the brain and crossing of the blood–brain barrier. Various ligands were added to the nanoparticles to improve blood–brain barrier transportation. The promising findings from the published studies reveal that more research into nanophytomedicine approaches as therapeutic targets for PD is warranted, especially since they have the potential to protect against key features of PD, including α-synuclein aggregation, mitochondrial dysfunction, and dopaminergic neuronal death. Furthermore, future directions should involve smart designs to tailor nanoparticles for improved therapeutic delivery by modifying their features, such as architecture, surface and material properties, targeting ligands, and responsiveness.
Clinical studies indicate that partial agonists of the G-protein-coupled, free fatty acid receptor 1 GPR40 enhance glucose-dependent insulin secretion and represent a potential mechanism for the ...treatment of type 2 diabetes mellitus. Full allosteric agonists (AgoPAMs) of GPR40 bind to a site distinct from partial agonists and can provide additional efficacy. We report the 3.2-Å crystal structure of human GPR40 (hGPR40) in complex with both the partial agonist MK-8666 and an AgoPAM, which exposes a novel lipid-facing AgoPAM-binding pocket outside the transmembrane helical bundle. Comparison with an additional 2.2-Å structure of the hGPR40-MK-8666 binary complex reveals an induced-fit conformational coupling between the partial agonist and AgoPAM binding sites, involving rearrangements of the transmembrane helices 4 and 5 (TM4 and TM5) and transition of the intracellular loop 2 (ICL2) into a short helix. These conformational changes likely prime GPR40 to a more active-like state and explain the binding cooperativity between these ligands.
Urea is a product of arginine catabolism in plants and its Nitrogen is recycled into the plant metabolism as ammonium after hydrolysis by urease. The
eu3-a
soybean mutant is null for the Ni insertion ...protein (UreG) necessary for urease activity. No UreG protein nor any activity of the urease enzymes is detectable in these
eu3-a
mutants. In order to understand the mechanisms of nitrogen cycling in soybean and the possible physiological benefits to N metabolism,
eu3-a
(urease-null) and control soybean near-isogenic
Eu3
plants were studied. They were grown to two different developmental stages (vegetative-V5 and reproductive-R5) with 15 mM nitrate as the sole source of nitrogen. Growth and biochemical parameters (such as amino acid, nitrate, and polyamine pools) were evaluated in leaves. Gene transcript levels were determined for some enzymes related to Arg catabolism, together with those of the DUR3 active urea transporter and the UreG Ni-insertion accessory protein, whose transcript was confirmed to be absent in
eu3-a
. The absence of urease activity in the
eu3-a
null plants did not affect growth or yield although there was a substantial and progressive accumulation of urea in the leaves. Metabolic changes occurred mainly in the pool of amino acids and in the expression of genes related to the pathway of Arg degradation. There are indications that the pathway may be diverted to form polyamines, but to a limited extent. Thus, considering both developmental stages, the degradation of Arg to urea and Orn remains the main path for nitrogen recycling from Arg, despite the progressive accumulation of urea and consequently immobilization of N.
ABSTRACT Manihot includes about 150 species with a Neotropical distribution. Wild species of Manihot constitute a plant genetic heritage that can be used in breeding programs for the cultivable ...species Manihot esculenta Crantz (cassava). However, wild populations, especially endemic ones, are under constant threat due to habitat destruction and climate change. The objective of this manuscript was to elaborate a taxonomic treatment of the endemic species of Manihot recorded in Northeast Brazil; determine the geographical distribution of species, richness, their conservation status, and solve typification problems. The study was based on the analysis of specimens deposited in national and international herbaria, as well as on field observations. Fifteen endemic species of Manihot were found, we propose lectotypes for five of them and one neotype. Most species are distributed in the state of Bahia, growing in Caatinga, Cerrado, and Atlantic Forest environments. Only M. breviloba was found in the states of Sergipe and Alagoas. The richest area was found in the Chapada Diamantina of the Espinhaço Range. In terms of conservation status, 80% of endemic species are in some threatened category, 13% are in the near threatened category and only 7% are in the least concern category.
Abstract Croton is the largest genus of Crotonoideae Burmeist. (ca. 1200 species), with approximately 300 species distributed in all the phytogeographic domains in Brazil. The Chapada of Araripe ...Environmental Protection Area (CA-EPA) is one of the largest protected areas in northeastern Brazil and comprises many different types of vegetation. Considering the expressive representation of Croton in that northeastern region and its morphological complexity, we carried out a taxonomic study of the species occurring in the CA-EPA. The analysis of collections deposited in regional herbaria, together with field observations, revealed 18 Croton species, five of which had never been cited as occurring in the study area; seven of those taxa are endemic to the Brazilian semiarid region. Croton species were recorded in all of the vegetation types in the CA-EPA, especially in the “carrasco” and “caatinga” vegetation. The plants habits, the shapes of their stipules, extrafloral nectaries, indumenta, and staminate and pistillate sepals were important characteristics for their differentiation.
Resumo Croton é o maior gênero de Crotonoideae Burmeist. (ca. 1200 espécies), com aproximadamente 300 espécies distribuídas em todos os domínios fitogeográficos brasileiros. A Área de Proteção Ambiental da Chapada do Araripe (APA-CA) é uma das maiores áreas protegidas do nordeste brasileiro e compreende diversos tipos de vegetação. Considerando a expressiva representatividade de Croton no Nordeste, bem como sua complexidade morfológica, realizamos um estudo taxonômico das espécies ocorrentes na APA-CA. A análise de coleções depositadas em herbários regionais, juntamente com observações de campo, revelou 18 espécies de Croton, cinco das quais nunca haviam sido citadas como ocorrendo na área de estudo; sete desses táxons são endêmicos do semiárido brasileiro. As espécies foram registradas em todas as fitofisionomias da APA-CA, principalmente na vegetação de carrasco e caatinga. Os hábitos das plantas, as formas de suas estípulas, nectários extraflorais, indumentos e sépalas estaminadas e pistiladas foram características importantes à diferenciação.
