Glutathione and ascorbic acid protect Arabidopsis plants against detrimental effects of iron deficiency

Iron is an essential micronutrient required for a wide variety of cellular functions in plant growth and development. Chlorosis is the first visible symptom in iron-deficient plants. Glutathione (GSH) and ascorbic acid (ASC) are multifunctional metabolites playing important roles in redox balancing. In this work, it was shown that GSH and ASC treatment prevented chlorosis and the accumulation of reactive oxygen species induced by iron deficiency in Arabidopsis leaves. In iron deficiency, GSH and ASC increased the activity of the heme protein ascorbate peroxidase at a similar level to that found in iron-sufficient seedlings. GSH was also able to preserve the levels of the iron-sulfur protein ferredoxin 2. GSH content decreased 25% in iron-deficient Arabidopsis seedlings, whereas the ASC levels were not affected. Taken together, these results showed that GSH and ASC supplementation protects Arabidopsis seedlings from iron deficiency, preserving cell redox homeostasis and improving internal iron availability.Instituto de Fisiología Vegeta

Chloroplasts as a nitric oxide cellular source : Effect of reactive nitrogen species on chloroplastic lipids and proteins

Nitric oxide (NO) generation by soybean (Glycine max var. ADM 4800) chloroplasts was studied as an endogenous product assessed by the electron paramagnetic resonance spin-trapping technique. Nitrite and L-arginine (Arg) are substrates for enzymatic activities considered to be the possible sources of NO in plants. Soybean chloroplasts showed a NO production of 3.2 ± 0.2 nmol min-1 mg-1 protein in the presence of 1 mM NaNO 2. Inhibition of photosynthetic electron flow by 3-(3,4- dichlorophenyl)-1,1-dimethyl urea resulted in a lower rate (1.21 ± 0.04 nmol min-1 mg-1 protein) of NO generation. Chloroplasts incubated with 1 mM Arg showed NO production of 0.76 ± 0.04 nmol min -1 mg-1 protein that was not affected either by omission of Ca2+ or by supplementation with Ca2+ and calmodulin to the incubation medium. This production was inhibited when chloroplasts were incubated in the presence of NO synthase inhibitors Nω,-nitro- L-Arg methyl ester hydrochloride and Nω-nitro-L-Arg. In vitro exposure of chloroplasts to an NO donor (250 μM S-nitrosoglutathione) decreased lipid radical content in membranes by 29%; however, incubation in the presence of 25 μM peroxynitrite (ONOO-) led to an increase in lipid-derived radicals (34%). The effect of ONOO- on protein oxidation was determined by western blotting, showing an increase in carbonyl content either in stroma or thylakoid proteins as compared to controls. Moreover, ONOO- treatment significantly affected both O2 evolution and chlorophyll fluorescence in thylakoids. Data reported here suggest that NO is an endogenous metabolite in soybean chloroplasts and that reactive nitrogen species could exert either antioxidant or prooxidant effects on chloroplast macromolecules.Instituto de Fisiología Vegeta

Control of ascorbic acid synthesis and accumulation and glutathione by the incident light red/far red ratio in Phaseolus vulgaris leaves

The effects of red/far red (R/FR) ratios on leaf ascorbate (AA) and glutathione (GSH) accumulation were examined in common bean (Phaseolus vulgaris L.). Growth under low R/FR ratios resulted in a "shade" phenotype and much lower leaf AA and GSH contents than high (R/FR) ratios. Photosynthesis rates were unaffected by changes in the R/FR ratio but leaf respiration rates, pyridine nucleotide pools and antioxidant enzyme activities were decreased under the low R/FR regime. The GSH pool changed slowly in response to altered R/FR ratios but leaf ascorbate acclimated over a single photoperiod. We conclude that light quality signals, particularly R/FR ratios, are important regulators of antioxidant synthesis and accumulation. These acclimatory changes are an early response to changing light environment.Instituto de Fisiología Vegeta

Mitochondria are the main target for oxidative damage in leaves of wheat (Triticum aestivum L.)

Photosynthesis, respiration, and other processes produce reactive oxygen species (ROS) that can cause oxidative modifications to proteins, lipids, and DNA. The production of ROS increases under stress conditions, causing oxidative damage and impairment of normal metabolism. In this work, oxidative damage to various subcellular compartments (i.e. chloroplasts, mitochondria, and peroxisomes) was studied in two cultivars of wheat differing in ascorbic acid content, and growing under good irrigation or drought. In well-watered plants, mitochondria contained 9-28-fold higher concentrations of oxidatively modified proteins than chloroplasts or peroxisomes. In general, oxidative damage to proteins was more intense in the cultivar with the lower content of ascorbic acid, particularly in the chloroplast stroma. Water stress caused a marked increase in oxidative damage to proteins, particularly in mitochondria and peroxisomes. These results indicate that mitochondria are the main target for oxidative damage to proteins under well-irrigated and drought conditions.Instituto de Fisiología VegetalFacultad de Ciencias Naturales y MuseoFacultad de Ciencias Agrarias y Forestale

Up-regulation of the mitochondrial alternative oxidase pathway enhances photosynthetic electron transport under drought conditions

The aim of this study was to explore the role of the mitochondrial alternative oxidase (AOX) in the protection of photosynthesis during drought in wheat leaves. The relative water contents of water-replete and drought-exposed wheat plants were 97.2±0.3 and 75±2, respectively. Drought increased the amount of leaf AOX protein and also enhanced the rate of AOX-dependent O 2 uptake by the respiratory electron transport chain. The amount of the reduced, active form of the AOX protein was specifically increased by drought. The AOX inhibitor salicylhydroxamic acid (1 mM; SHAM) inhibited 70% of AOX activity in vivo in both water-replete and drought-exposed plants. Plants treated with SHAM were then exposed to low (100), high (350), or excess light (800 μmol photons m -2 s -1 ) for 90 min. SHAM did not modify chlorophyll a fluorescence quenching parameters in water-replete controls after any of these treatments. However, while the maximal quantum yield of photosystem II (PSII) electron transport (F v /F m ) was not affected by SHAM, the immediate quantum yield of PSII electron transport (Φ PSII ) and photochemical quenching (qP) were gradually reduced by increasing irradiance in SHAM-treated drought-exposed plants, the decrease being most pronounced at the highest irradiance. Non-photochemical quenching (NPO) reached near maximum levels in plants subjected to drought at high irradiance. However, a combination of drought and low light caused an intermediate increase in NPO, which attained higher values when AOX was inhibited. Taken together, these results show that up-regulation of the respiratory AOX pathway protects the photosynthetic electron transport chain from the harmful effects of excess light.Instituto de Fisiología Vegeta

Up-regulation of the mitochondrial alternative oxidase pathway enhances photosynthetic electron transport under drought conditions

The aim of this study was to explore the role of the mitochondrial alternative oxidase (AOX) in the protection of photosynthesis during drought in wheat leaves. The relative water contents of water-replete and drought-exposed wheat plants were 97.2±0.3 and 75±2, respectively. Drought increased the amount of leaf AOX protein and also enhanced the rate of AOX-dependent O 2 uptake by the respiratory electron transport chain. The amount of the reduced, active form of the AOX protein was specifically increased by drought. The AOX inhibitor salicylhydroxamic acid (1 mM; SHAM) inhibited 70% of AOX activity in vivo in both water-replete and drought-exposed plants. Plants treated with SHAM were then exposed to low (100), high (350), or excess light (800 μmol photons m -2 s -1 ) for 90 min. SHAM did not modify chlorophyll a fluorescence quenching parameters in water-replete controls after any of these treatments. However, while the maximal quantum yield of photosystem II (PSII) electron transport (F v /F m ) was not affected by SHAM, the immediate quantum yield of PSII electron transport (Φ PSII ) and photochemical quenching (qP) were gradually reduced by increasing irradiance in SHAM-treated drought-exposed plants, the decrease being most pronounced at the highest irradiance. Non-photochemical quenching (NPO) reached near maximum levels in plants subjected to drought at high irradiance. However, a combination of drought and low light caused an intermediate increase in NPO, which attained higher values when AOX was inhibited. Taken together, these results show that up-regulation of the respiratory AOX pathway protects the photosynthetic electron transport chain from the harmful effects of excess light.Instituto de Fisiología Vegeta

Proyecto: sistemas inteligentes aplicados a la enseñanza de la programacion en Ingenieria

El proyecto objeto de esta presentación, se desarrolla actualmente en la Facultad de Ciencias Exactas, Físicas y Naturales de la Universidad Nacional de Córdoba. Ha sido presentado para su acreditación ante la Secretaría de Investigación y en Ciencia y Tecnología de esta Universidad en la convocatoria bianual 2012-2013 de proyectos I+D. Es el primer antecedente formal en esta línea de investigación aplicada a la enseñanza en Ingeniería en esta Casa de Estudios. Su mayor relevancia consiste en el impacto que se espera de él para las carreras de Ingeniería, especialmente la de Computación, tanto para el rendimiento académico de los estudiantes como para el fortalecimiento de los recursos humanos – investigadores, docentes y estudiantes- en investigación. El eje central consiste en la utilización de sistemas tutores inteligentes y aplicaciones con robots para la enseñanza de Programación en Ingeniería. Es importante destacar que tanto los integrantes de este equipo de investigación como otros docentes e investigadores de la Casa, han realizado acciones de investigación, transferencia y evaluación en la aplicación de Tecnologías de Información y Comunicación como herramientas soporte para la enseñanza presencial de grado. Estas acciones se han visto favorecidas desde 2006 en el marco del Programa para el Mejoramiento de la Enseñanza en Ingeniería que contempló la adquisición de un importante volumen de recursos informáticos. Por otra parte, los integrantes de este equipo cuentan además con antecedentes en el sentido específico de esta línea de investigación. Éstas son las fortalezas que alentaron a la propuesta que aquí se presenta.Eje: Tecnología informática aplicada en educaciónRed de Universidades con Carreras en Informática (RedUNCI

Glutathione and ascorbic acid protect Arabidopsis plants against detrimental effects of iron deficiency

Iron is an essential micronutrient required for a wide variety of cellular functions in plant growth and development. Chlorosis is the first visible symptom in iron-deficient plants. Glutathione (GSH) and ascorbic acid (ASC) are multifunctional metabolites playing important roles in redox balancing. In this work, it was shown that GSH and ASC treatment prevented chlorosis and the accumulation of reactive oxygen species induced by iron deficiency in Arabidopsis leaves. In iron deficiency, GSH and ASC increased the activity of the heme protein ascorbate peroxidase at a similar level to that found in iron-sufficient seedlings. GSH was also able to preserve the levels of the iron-sulfur protein ferredoxin 2. GSH content decreased 25% in iron-deficient Arabidopsis seedlings, whereas the ASC levels were not affected. Taken together, these results showed that GSH and ASC supplementation protects Arabidopsis seedlings from iron deficiency, preserving cell redox homeostasis and improving internal iron availability.Instituto de Fisiología Vegeta