Stella Castro - Academia.edu (original) (raw)

Papers by Stella Castro

Canadian Journal of Microbiology, 2006

Glutathione (GSH) plays an important role in the defence of microorganisms and plants against dif... more Glutathione (GSH) plays an important role in the defence of microorganisms and plants against different environmental stresses. To determine the role of GSH under different stresses, such as acid pH, saline shock, and oxidative shock, a GSH-deficient mutant (Bradyrhizobium sp. 6144-S7Z) was obtained by disruption of the gshA gene, which encodes the enzyme γ-glutamylcysteine synthetase. Growth of the mutant strain was significantly reduced in liquid minimal saline medium, and the GSH content was very low, about 4% of the wild-type level. The defect, caused by disruption of the gshA gene in the growth of mutant strain, cannot be reversed by the addition of GSH (up to 100 µmol/L) to the liquid minimal saline medium, and the endogenous GSH level was approximately the same as that observed without the addition of GSH. In contrast, the wild-type strain increased the GSH content under these conditions. However, the growth of the mutant strain in a rich medium (yeast extract – mannitol) inc...

In this study, it was investigated the reactive oxygen species (ROS) production in peanut nodules... more In this study, it was investigated the reactive oxygen species (ROS) production in peanut nodules at three peanut growth stages (R): R1 (flowering), R4 (full pod) and R6 (full seed). Analysis of ROS production showed that superoxide anion and hydrogen peroxide contents decreased while lipid peroxidation and protein oxidation remained unchanged throughout nodule development. Furthermore, it was found that the inside of formed nodules was 100% red at (R1), 54% at (R4) and 39% at (R6), respectively. The total soluble protein content decreased while leghemoglobin content remained unaltered at different growth stages. Thus, our findings suggest that ROS production is not involved in the peanut nodule senescence indicating that this process would not be accompanied by an oxidative burst. It is possible to suggest that the antioxidant system would play an important role in the protection of peanut nodules against ROS production

Agriscientia, 2006

La produccion de mani en Argentina se concentra en la region central de la provincia de Cordoba, ... more La produccion de mani en Argentina se concentra en la region central de la provincia de Cordoba, la cual experimento ultimamente una perdida importante de la productividad de los suelos y una declinacion aleatoria del rendimiento de los cultivos. La contribucion relativa de la fijacion biologica (FBN) de nitrogeno al mani en suelos de diferente fertilidad no ha sido suficientemente estudiada.Entonces, se evaluo el efecto de cepas de rizobios (TTOO2R, SEMIA 6144R y TAL 1000R) sobre el rendimiento y el balance de nitrogeno de mani cultivado en suelos con alto y bajo contenido del nutriente. No hubo diferencias significativas en los parametros simbioticos y de rendimiento del cultivo entre las cepas introducidas y las nativas, pero se observo una contribucion relativa mayor de la FBN en el suelo con bajo contenido de nitrogeno (~58% de contribucion) que en el suelo con alto contenido (~27% de contribucion). Esta comprobacion del aporte relativo de la FBN asociada a la fertilidad del su...

Symbiosis, 1998

Soil acidity is a stress factor that negatively affects the persistence of Rhizobium strains and ... more Soil acidity is a stress factor that negatively affects the persistence of Rhizobium strains and the nodulation and nitrogen fixation in legumes. To identify peanut symbiont acid-tolerant strains we tested the ability of Bradyrhizobium sp. USDA 3187 and Bradyrhizobium sp. TT 001 (isolated from nodules of peanut) to grow at pH 5 in unbuffered broth medium. Only Bradyrhizobium sp. TT 001 grew at this pH and tolerance to this condition was not related with the synthesis of polyamines, lipopolysaccharide or with the production of extracellular polysaccharides. Cells of TT 001 were markedly resistant to the effects of crystal violet and was not affected by pH 5. These results suggest that the outer membrane structure could be involved in pH tolerance.

El cultivo de mani es de gran importancia en la provincia de Cordoba. En los ultimos anos, la per... more El cultivo de mani es de gran importancia en la provincia de Cordoba. En los ultimos anos, la perdida de rendimiento del cultivo en la region centro debido a la degradacion de los suelos, la incidencia de enfermedades causadas por hongos y la erosion hidrica y eolica ha desplazado el area de siembra hacia el sur de la provincia. La hipotesis planteada en este proyecto es que la diversidad de bacterias que habitan la rizosfera y/o los tejidos de mani constituye una fuente para la seleccion de aquellos que, por sus propiedades fisiologicas y metabolicas, permitan mejorar el rendimiento del cultivo, actuando como biocontroladores de fitopatogenos o biofertilizantes. Los objetivos propuestos son: 1) Evaluar y caracterizar la actividad antifungica en una poblacion previamente seleccionada de microorganismos del suelo del area manisera de Cordoba para su utilizacion en el desarrollo de practicas sustentables tendientes a optimizar la produccion de dicho cultivo mediante funciones biocontr...

We have previously shown that the fungicide Mancozeb reduced Bradyrhizobiurn sp. growth by 50%, p... more We have previously shown that the fungicide Mancozeb reduced Bradyrhizobiurn sp. growth by 50%, produced biochemical alterations such as changes in membrane composition and polyamine contents, and affected the peanut root-bacteria interaction in greenhouse experiments. In this work we show the variations caused by the fungicide on the molecules related with the peanut-bacteria interaction such as lipopolysaccharides (LPS) and cyclic ~-glucans. Furthermore, the changes on peanut root nodule polyarnines induced by Mancozeb are analyzed.

Chemosphere, 2020

Unraveling the impact of arsenic on the redox response of peanut plants inoculated with two diffe... more Unraveling the impact of arsenic on the redox response of peanut plants inoculated with two different Bradyrhizobium sp. strains

Plant Physiology and Biochemistry, 2020

Proline accumulation and metabolism are associated with mechanisms of abiotic stress avoidance in... more Proline accumulation and metabolism are associated with mechanisms of abiotic stress avoidance in plants. Proline accumulation generally improves osmotic stress tolerance whereas proline metabolism can have varying effects from ATP generation to the formation of reactive oxygen species. To further understand the roles of proline in stress protection, two peanut cultivars with contrasting tolerance to drought were examined by transcriptional and biochemical analyses during water stress. Plants exposed to polyethylene glycol had diminished relative water content and increased proline content; while, only the drought sensitive plants, cultivar Granoleico, showed lipid oxidative damage (measured as thiobarbituric acid reactive substances). The expression of proline biosynthesis genes (P5CS1, P5CS2a, P5CS2b, P5CR) was increased in both cultivars upon exposure to water stress. However, the relative expression of proline catabolism genes (ProDH1, ProDH2) was increased only in the sensitive cultivar during stress. Exogenous addition of proline and the proline analogue thiazolidine-4-carboxylic acid (T4C), both substrates of proline dehydrogenase, was also used to exacerbate and identify plant responses. Pretreatment of plants with T4C induced unique changes in the drought tolerant EC-98 cultivar such as higher mRNA levels of proline biosynthetic and catabolic ProDH genes, even in the absence of water stress. The increased levels of ProDH gene expression, potentially associated with higher T4C conversion to cysteine, may contribute to the tolerant phenotype.

Plant Science, 2017

Genotype-specific metabolic features related to biological nitrogen fixation (BNF) efficiency are... more Genotype-specific metabolic features related to biological nitrogen fixation (BNF) efficiency are evaluated in peanut.  Sustained growth and BNF suggest distinct metabolic regulation in the tolerant cultivar.  Nodules from the tolerant cultivar efficiently accumulate protective metabolites.  Drought stressed nodules of the tolerant cultivar reach the metabolic state of unstressed plants after re-irrigation.  Traits are proposed which enable an effective BNF in a drought-tolerant peanut cultivar.

Chemosphere, Jan 24, 2017

Arsenic (As)-polluted groundwater constitutes a serious problem for peanut plants, as roots can a... more Arsenic (As)-polluted groundwater constitutes a serious problem for peanut plants, as roots can accumulate the metalloid in their edible parts. Characterization of stress responses to As may help to detect potential risks and identify mechanisms of tolerance, being the induction of oxidative stress a key feature. Fifteen-day old peanut plants were treated with arsenate in order to characterize the oxidative stress indexes and antioxidant response of the legume under realistic groundwater doses of the metalloid. Superoxide anion (O2(-)) and hydrogen peroxide (H2O2) histochemical staining along with the activities of NADPH oxidase, superoxide dismutase (SOD), catalase (CAT) and thiol (glutathione and thioredoxins) metabolism were determined in roots. Results showed that at 20 μM H2AsO4(-), peanut growth was reduced and the root architecture was altered. O2(-) and H2O2 accumulated at the root epidermis, while lipid peroxidation, NADPH oxidase, SOD, CAT and glutathione S-transferase (GS...

Drought Stress Tolerance in Plants, Vol 1, 2016

Tolerance of plants to drought stress is a consequence of the activation of multicomponent signal... more Tolerance of plants to drought stress is a consequence of the activation of multicomponent signaling pathways to achieve cellular homeostasis and promote survival. Evidence of regulatory systems that link sensing and signaling of environmental conditions and the intracellular redox status have shed light on reactive oxygen species (ROS) as key components of transduction pathways. Thus, ROS play a dual role in the response of plants to abiotic stresses functioning as toxic by-products of stress metabolism, as well as important signal transduction molecules. The signaling pathway is accomplished by the balance between the intensity, duration, and subcellular localization of ROS generation. In this sense, the subcellular compartmentalization of oxidants and the associated changes in redox state are important aspects to be considered beyond the overall ROS cellular content. Hydrogen peroxide (H2O2), the main signaling molecule studied so far, is the most likely ROS to act as messenger because of its relative stability, and it can cross membranes through aquaporins. Nowadays, signaling mechanisms involve not only toxic molecules but also detoxification systems. Effective ROS signaling may require increased flux through antioxidant components, notably those that are thiol dependent. For signal transduction, ROS can interact with other signaling pathways such as activation of NADPH oxidase dependent on monomeric G protein, lipid-derived signals, induction of MAPK, redox-sensitive transcription factors, regulation of Ca2+, and hormones. In this chapter, aspects of reactive oxygen species as signaling molecules modulating drought stress tolerance are reported.

Physiological and Molecular Plant Pathology, 2011

Selected strains of rhizobacteria induce systemic resistance in plant (ISR), enhancing the capaci... more Selected strains of rhizobacteria induce systemic resistance in plant (ISR), enhancing the capacity to mobilize infection-induced cellular defense responses (priming). Bacillus sp. CHEP5 and Pseudomonas sp BREN6 strains reduced root and stem wilt disease severity caused by Sclerotium rolfsii in Arachis hypogaea L. Strains inoculation increased the activity of phenylalanine ammonia-lyase and peroxidase, after pathogen-challenge, indicating priming. CHEP5 primes plants to produce more ethylene upon stimulation with ACC. A. hypogaea L is an ISR-positive plant and BREN6 and CHEP5 strains enhance the plant's defense capacity by priming for potentiated activity of defense proteins and ACC-converting capacity.

Soil Biology and Biochemistry, 2002

The present work was designed to study the effect of acidity and calcium concentration on the Bra... more The present work was designed to study the effect of acidity and calcium concentration on the Bradyrhizobium sp. strain SEMIA 6144 (peanut symbiont). The bacteria showed a growth and viability diminution at low pH (5.0) and at a calcium concentration of 0.05 mM. Increasing concentrations of calcium signi®cantly improved the rhizobial growth under acid stress conditions. Molecules related to the plantbacteria recognition, such as exopolysaccharides (EPS) and lipopolysaccharides (LPS) showed changes at different pH values and calcium concentrations. Variations in the cellular permeability were also observed under stress conditions. Moreover, the attachment of the bacteria to excised peanut roots was examined. Optimal bacteria root attachment to excised peanut roots was dependent on pH and calcium limitation in the medium.

AoB plants, Jan 24, 2014

Salt stress conditions lead to increased production of reactive oxygen species (ROS) in plant cel... more Salt stress conditions lead to increased production of reactive oxygen species (ROS) in plant cells. Halophytes have the ability to reduce these toxic ROS by means of a powerful antioxidant system that includes enzymatic and non-enzymatic components. In this research, we used the halophytic shrub Prosopis strombulifera to investigate whether the ability of this species to grow under increasing salt concentrations and mixtures was related to the synthesis of polyphenolic compounds and to the maintenance of leaf pigment contents for an adequate photosynthetic activity. Seedlings of P. strombulifera were grown hydroponically in Hoagland's solution, gradually adding Na2SO4 and NaCl separately or in mixtures until reaching final osmotic potentials of -1, -1.9 and -2.6 MPa. Control plants were allowed to develop in Hoagland's solution without salt. Oxidative damage in tissues was determined by H2O2 and malondialdehyde content. Leaf pigment analysis was performed by high-performanc...

Soil Biology and Biochemistry, 2005

The early stages of the symbiosis in legumes, when rhizobia enter the plant root, penetrate into ... more The early stages of the symbiosis in legumes, when rhizobia enter the plant root, penetrate into the root cortex and spread inside nodules, vary among legume species. The most studied infection mechanism involves infection thread formation while the most simple ...

Plant Physiology and Biochemistry, 2005

In this work, the peanut nodulation kinetics by acid-sensitive and tolerant isolates under acid s... more In this work, the peanut nodulation kinetics by acid-sensitive and tolerant isolates under acid stress condition was analyzed. The results demonstrated that the acid pH produced a decrease in the number of nodules formed only when peanut plants were inoculated with acid-sensitive isolates but increased steadily by the addition of 10 mM Ca2+, reaching higher values than those obtained at pH 7.0. On the contrary, the peanut nodulation by acid-tolerant isolates was not affected by this stressing condition. These data suggest that acid-tolerant isolates could be used as a potential source of strains for preparing highly effective inoculants for peanut plants growing in acid soils.

Plant Growth Regulation, 2010

We have investigated the response of two peanut cultivars (TEGUA and UTRE) with different growth ... more We have investigated the response of two peanut cultivars (TEGUA and UTRE) with different growth habits and branching pattern structures to different nitrogen (N) sources, namely, N-fertilizer or N 2 made available by symbiotic fixation, and analysed the pattern of nitrate reductase (NR) activity in these cultivars. Nitrate and amino acid contents were also examined under these growth conditions. In terms of nitrogen source, cv. TEGUA showed a better response to inoculation with Bradyrhizobium sp. SEMIA 6144 at 40 days after planting, while cv. UTRE responded better to N-fertilizer (5 mM KNO 3). Both cultivars showed different patterns of NR activity in the analyzed plant organs (leaves, roots, and nodules), which were dependent on the N source. When nitrogen became available to the plant through symbiotic N 2 fixation, the patterns of NR activity distribution were different in the two cultivars, with cv. TEGUA showing a higher NR activity in the nodules than in the leaves and roots, and cv. UTRE showing no difference in terms of NR activity among organs. The nitrate and amino acid contents showed a similar trend between the two cultivars, with the highest nitrate content in the leaves of fertilized plants and the highest amino acid content in the nodules. The high nitrate content of the leaves of cv. UTRE indicated the better response of this cultivar to N-fertilizer.

Functional Plant Biology, 2014

Drought stress is one of the most important environmental factors that affect plant growth and li... more Drought stress is one of the most important environmental factors that affect plant growth and limit biomass production. Most studies focus on drought stress development but the reversibility of the effects receives less attention. Therefore, the present work aims to explore the biological nitrogen fixation (BNF) of the symbiotic association between peanut (Arachis hypogaea L.) and Bradyrhizobium sp. during a drought–recovery cycle with a focus on the response of enzyme activity and gene expression of the antioxidant system. Peanuts exposed to drought stress had impaired BNF, as indicated by lower nitrogenase activity, and decreased leghaemoglobin content; the latter was reversed to control values upon rehydration. Previous results demonstrated that reactive oxygen species (O2·− and H2O2) were accumulated as a consequence of drought stress, suggesting that nodules experience oxidative stress. In addition, marker transcripts responsive to drought, abscisic acid and H2O2 were upregula...

FEMS Microbiology Ecology, 2012

Sixty-nine fungal strains were isolated countrywide from 10 Vietnamese soils, in areas both with ... more Sixty-nine fungal strains were isolated countrywide from 10 Vietnamese soils, in areas both with and without a history of exposure to Agent Orange, and their degrading activities on the phenoxy acid herbicides 2,4-dichlorophenoxyacetic acid (2,4-D) and 2,4,5-trichlorophenoxyacetic acid (2,4,5-T), as well as related compounds, were examined. Among taxonomically various fungi, 45, 12 and 4% of the isolates degraded phenoxyacetic acid (PA), 2,4-D and 2,4,5-T, respectively. While the PA-degrading fungi were distributed to all sites and among many genera, the 2,4-D-degraders were found only in order Eurotiales in class Eurotiomycetes. All of the 2,4,5-T-degrading fungal strains were phylogenetically close to Eupenicillium spp. and were isolated from southern Vietnam. As a degradation intermediate, the corresponding phenol compounds were detected in some strains. The degradation substrate spectrum for 26 compounds of Eupenicillium spp. strains including 2,4,5-T-degraders and-non-degraders seemed to be related to phylogenetic similarity and soil sampling location of the isolates. These results suggest that the heavily contaminated environments enhanced the adaptation of the phylogenetic group of Eupenicillium spp. toward to obtain the ability to degrade 2,4,5-T.

Enzyme and Microbial Technology, 2013

In this work, we evaluated the effects of cadmium (Cd) on the antioxidant defense system response... more In this work, we evaluated the effects of cadmium (Cd) on the antioxidant defense system responses and the role of nitrate reductase (NR) in the redox balance maintenance in Bradyrhizobium japonicum strains. For that, B. japonicum USDA110 and its NR defective mutant strain (GRPA1) were used. Results showed that the addition of 10 M Cd did not modify the aerobic growth of the wild type strain while the mutant strain was strongly affected. Anaerobic growth revealed that only the parental strain was able to grow under this condition. Cd reduced drastically the NR activity in B. japonicum USDA110 and increased lipid peroxide content in both strains. Cd decreased reduced glutathione (GSH)/oxidized glutathione (GSSG) ratio in B. japonicum USDA110 although, a significant increased was observed in the mutant GRPA1. GSHrelated enzymes were induced by Cd, being more evident the increase in the mutant strain. This different behavior observed between strains suggests that NR enzyme plays an important role in the redox balance maintenance in B. japonicum USDA 110 exposed to Cd.