Role of antioxidant scavenging enzymes and extracellular polysaccharide in pathogenicity of rice bacterial blight pathogen Xanthomonas oryzae pv. oryzae

The role of antioxidant scavenging enzymes of plant pathogenic bacteria: catalase, ascorbate peroxidase and a virulence factor; extracelluar polysaccharide prodn. in detg. the virulence of Xanthomonas oryzae pv. oryzae (Xoo) isolates and its differential reaction to rice cultivars was studied. A varied level of antioxidant scavenging activity and exopolysaccharide prodn. was obsd. among 34 isolates studied, and most of the Xoo isolates with higher catalase activity also exhibited higher ascorbate peroxidase activity. The max. level of catalase (45 μM H2O2 min-​1 mg-​1 protein)​, ascorbate peroxidase (29 μM ascorbate min-​1 mg-​1 proteins) activity and exopolysaccharide prodn. (70 mg) was found in isolate Xoo32 which induced max. lesion length on cultivar 'Jaya' upon clip inoculation in virulence assay. Among the 44 cultivars screened, cultivar 'Jeerigesanna' recorded least bacterial blight disease incidence, with 0.7 cm lesion length. The activity of catalase, ascorbate peroxidase and exopolysaccharide can be employed as bio-​chem. markers in detg. the virulence of Xoo under lab. conditions

Microarray analysis of spring barley cultivars displaying differing sensitivity to physiological leaf spot (PLS)

peer-reviewedPhysiological leaf spot (PLS) is a disorder of spring barley (Hordeum vulgare L.), which has become more pronounced in recent years. The initial symptoms are small chlorotic/brown spots on the upper four leaves, which may develop into necrotic lesions with an irregular shape. As PLS occurs on leaves that are directly exposed to sunlight, it is thought that high light stress could be a trigger for the condition. This study concentrates on two cultivars, Cooper and Crusader, which display differential sensitivity to PLS. Biochemical measurements and enzyme assays revealed substantial difference in levels of ascorbate, type III peroxidases, and superoxide dismutase between the chosen cultivars during the 2003 growing season. A global gene expression study, using these field samples, was performed by microarray analysis. This supported the biochemical findings and highlighted additional sets of genes differentially expressed between the cultivars. Transcripts of particular interest, which appeared, included calcium signalling genes, cold-responsive genes and those involved in the assembly of Photosystem I. We conclude that susceptibility to PLS is related to levels of expression of genes with a role in countering the effects of oxidative stress.Teagasc Walsh Fellowship Programm

Pharmaceutical and personal care products-induced stress symptoms and detoxification mechanisms in cucumber plants.

Contamination of agricultural soils by pharmaceutical and personal care products (PPCPs) resulting from the application of treated wastewater, biosolids and animal wastes constitutes a potential environmental risk in many countries. To date a handful of studies have considered the phytotoxicity of individual PPCPs in crop plants, however, little is known about the effect of PPCPs as mixtures at environmentally relevant levels. This study investigated the uptake and transport, physiological responses and detoxification of a mixture of 17 PPCPs in cucumber seedlings. All PPCPs were detected at higher concentrations in roots compared to leaves, with root activity inhibited in a dose-dependent manner. At 5-50 μg/L, the mature leaves exhibited burnt edges as well as a reduction in photosynthesis pigments. Reactive oxygen species (ROS) production and lipid peroxidation increased with increasing PPCP concentrations; and their contents were greater in roots than in leaves for all PPCP treatments. Enzymes involved in various functions, including oxidative stress (superoxide dismutase and ascorbate peroxidase) and xenobiotic metabolism (peroxidase and glutathione S-transferase), were elevated to different levels depending on the PPCP concentration. Glutathione content gradually increased in leaves, while a maxima occurred at 0.5 μg L-1 PPCPs in roots, followed by a decrease thereafter. This study illustrated the complexity of phytotoxicity after exposure to PPCP mixtures, and provided insights into the molecular mechanisms likely responsible for the detoxification of PPCPs in higher plants

Oxidative Stress Associated with Chilling Injury in Immature Fruit: Postharvest Technological and Biotechnological Solutions

Immature, vegetable-like fruits are produced by crops of great economic importance, including cucumbers, zucchini, eggplants and bell peppers, among others. Because of their high respiration rates, associated with high rates of dehydration and metabolism, and their susceptibility to chilling injury (CI), vegetable fruits are highly perishable commodities, requiring particular storage conditions to avoid postharvest losses. This review focuses on the oxidative stress that affects the postharvest quality of vegetable fruits under chilling storage. We define the physiological and biochemical factors that are associated with the oxidative stress and the development of CI symptoms in these commodities, and discuss the different physical, chemical and biotechnological approaches that have been proposed to reduce oxidative stress while enhancing the chilling tolerance of vegetable fruits

Effect of arsenic-phosphorus interaction on arsenic-induced oxidative stress in chickpea plants

Arsenic-induced oxidative stress in chickpea was investigated under glasshouse conditions in response to application of arsenic and phosphorus. Three levels of arsenic (0, 30 and 60 mg kg−1) and four levels of P (50, 100, 200, and 400 mg kg−1) were applied to soil-grown plants. Increasing levels of both arsenic and P significantly increased arsenic concentrations in the plants. Shoot growth was reduced with increased arsenic supply regardless of applied P levels. Applied arsenic induced oxidative stress in the plants, and the concentrations of H2O2 and lipid peroxidation were increased. Activity of superoxide dismutase (SOD) and concentrations of non-enzymatic antioxidants decreased in these plants, but activities of catalase (CAT) and ascorbate peroxidase (APX) were significantly increased under arsenic phytotoxicity. Increased supply of P decreased activities of CAT and APX, and decreased concentrations of non-enzymatic antioxidants, but the high-P plants had lowered lipid peroxidation. It can be concluded that P increased uptake of arsenic from the soil, probably by making it more available, but although plant growth was inhibited by arsenic the P may have partially protected the membranes from arsenic-induced oxidative stress

Existing antioxidant levels are more important in acclimation to supplemental UV-B irradiation than inducible ones: Studies with high light pretreated tobacco leaves

Greenhouse grown tobacco plants were exposed to supplemental ultraviolet irradiation (280-400 nm, UV-B centered) for 6 days and changes in their photosynthesis (gas exchange and electron transport) and general and specific antioxidant activities were measured. UV irradiation corresponded to 8.95 kJ m-2 d-1 biologically effective dose and was supplemented to below ambient (200 μmol m-2 s-1 photon flux density) photosynthetic photon flux density (PPFD, 400-700 nm). Two groups of plants, which were different in their leaf antioxidant capacities due to one of them having been acclimated to high irradiance (1000 μmol m-2 s-1 PPFD) before the UV treatment, responded differently. High light pretreated leaves lost approximately 25% of photosynthetic activity during the UV exposure and showed no change either in the amounts of UV-absorbing pigments or antioxidant levels. On the other hand, leaves which were exposed to UV irradiation without the preceding high light acclimation had 60% lower photosynthesis by the end of the treatment, and increased antioxidant activities. Our results emphasize the importance of base antioxidant levels over inducible pools in leaf responses to low doses of UV irradiation and may also contribute to hypotheses on acclimation under field conditions

The mutualistic fungus Piriformospora indica protects barley roots from a loss of antioxidant capacity caused by the necrotrophic pathogen Fusarium culmorum

Fusarium culmorum causes root rot in barley (Hordeum vulgare), resulting in severely reduced plant growth and yield. Pretreatment of roots with chlamydospores of the mutualistic root-colonizing basidiomycete Piriformospora indica (Agaricomycotina) prevented necrotization of root tissues and plant growth retardation commonly associated with Fusarium root rot. Quantification of Fusarium infections with a real-time PCR assay revealed a correlation between root rot symptoms and the relative amount of fungal DNA. Fusarium-infected roots showed reduced levels of ascorbate and glutathione (GSH), along with reduced activities of antioxidant enzymes such as superoxide dismutase (SOD), ascorbate peroxidase (APX), glutathione reductase (GR), dehydroascorbate reductase (DHAR), and monodehydroascorbate reductase (MDHAR). Consistent with this, Fusarium-infected roots showed elevated levels of lipid hydroperoxides and decreased ratios of reduced to oxidized forms of ascorbate and glutathione. In clear contrast, roots treated with P. indica prior to inoculation with F. culmorum showed levels of ascorbate and GSH that were similar to controls. Likewise, lipid peroxidation and the overall reduction in antioxidant enzyme activities were largely attenuated by P. indica in roots challenged by F. culmorum. These results suggest that P. indica protects roots from necrotrophic pathogens at least partly, through activating the plant’s antioxidant capacity

英語授業におけるアクティブ・ラーニングの実質化をめざして

This paper deals with the study of the antioxidant activity of diterpene glycoside of stevioside in the absence of stress factors and under the influence of heavy metals. Results showed different response of stevioside to - it reduced catalase activity by 34% as compared to control, but virtually had no effect on the enzymatic activity of an ascorbate peroxidase. Heavy metals at suboptimal concentrations (10 μM) also did not significantly change the activity of the studied enzymes. Growing of plants at a sublethal concentration of pollutants (1 mM) was accompanied by a sharp increase in the activity of ascorbate peroxidase, and, otherwise, decrease in catalase activity. Plants pretreatment with diterpene glycosides ensured reduction of the negative effects of heavy metals on the activity of these enzymes, i.e., ascorbate peroxidase activity was lower and catalase activity was higher. The influence of stevioside also led to 4-fold increase in the content of non-enzymatic antioxidant - proline that may indicate an increasing stress resistance of plants to negative environmental factors

Trypanosoma cruzi expresses a plant-like ascorbate-dependent hemoperoxidase localized to the endoplasmic reticulum.

In most aerobic organisms hemoperoxidases play a major role in H(2)O(2)-detoxification, but trypanosomatids have been reported to lack this activity. Here we describe the properties of an ascorbate-dependent hemoperoxidase (TcAPX) from the American trypanosome Trypanosoma cruzi. The activity of this plant-like enzyme can be linked to the reduction of the parasite-specific thiol trypanothione by ascorbate in a process that involves nonenzymatic interaction. The role of heme in peroxidase activity was demonstrated by spectral and inhibition studies. Ascorbate could saturate TcAPX activity indicating that the enzyme obeys Michaelis-Menten kinetics. Parasites that overexpressed TcAPX activity were found to have increased resistance to exogenous H(2)O(2). To determine subcellular location an epitope-tagged form of TcAPX was expressed in T. cruzi, which was observed to colocalize with endoplasmic reticulum resident chaperone protein BiP. These findings identify an arm of the oxidative defense system of this medically important parasite. The absence of this redox pathway in the human host may be therapeutically exploitable

Efecto del estrés producido por la mezcla de sales en la concentración de aldehído malónico, proteínas y enzimas antioxidantes de Leymus chinensis de tres colores foliares diferentes

The mixed salt stress is common in nature. Salt stressalways affects plant growth. Different plant species have different adaptive capacity to salty soil. Leymus chinensis is an herbaceous plant with different leaf colors. However, little research was conducted to explore the different tolerance mechanisms to salt stress among the three different leaf colour genotypes of Leymus chinensis (grey green, transitional color, yellow green). Pot experiments for Leymus chinensis in three leaf colors were conducted under mixed salt treatments in 2010. Malondialdehyde (MDA) and protein concentrations, and the activity of various antioxidant enzymes [i.e., superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), glutathione reductase (GR), dehydroascorbate reductase (DHAR) and monodehydroascorbate reductase (MDHAR)] were determined and compared among the three leaf color genotypes of Leymus chinensis. The concentrations of MDA and protein, and the activity of antioxidant enzymes showed an increasing trend with increasing pHs in almost all three leaf colors, and all of them became highest when salt stress and pH values were also highest. Moreover, antioxidant enzymes were the highest in the grey-green leaf color, and the lowest in the yellow green leaf color after exposure to the same pH treatment. The results suggested that all three leaf colors of Leymus chinensis were tolerant to salt stress, and the salt-tolerance declined according to the order of grey green > transitional color > yellow green of Leymus chinensis. This study can give us a better understanding of the intra-species adaptation to mixed salt soils.El estrés causado por mezcla de sales en el suelo es común en la naturaleza. El estrés salino siempre afecta el crecimiento de las plantas. Plantas de especies diferentes difieren en su capacidad de adaptación al estrés por sales en el suelo. Leymus chinensis es una planta herbácea con diferentes colores foliares. Sin embargo, se han conducido pocos estudios tendientes a determinar los diferentes mecanismos de tolerancia al estrés salino entre los tres genotipos de color foliar diferente de L. chinensis (grisáceo verdoso, color intermedio, amarillo verdoso). En 2010, se condujeron experimentos en macetas usando genotipos de L. chinensis de tres colores diferentes de hoja expuestos o no a tratamientos conteniendo una mezcla de sales. Las concentraciones de aldehído malónico (MDA) y proteínas, y la actividad de varias enzimas antioxidantes [es decir, la superóxido dismutasa (SOD), catalasa (CAT), ascórbico peroxidasa (APX), glutatión reductasa (GR), dehidroascórbico reductasa (DHAR) y monodehidroascórbico reductasa (MDHAR)] se determinaron y compararon entre los tres genotipos de color foliar diferente de L. chinensis. Las concentraciones de MDA y proteínas, y la actividad de enzimas antioxidantes mostraron una tendencia a incrementarse a mayores pHs en casi todos los colores foliares, y las tendencias en los tres colores foliares alcanzaron su punto máximo cuando el estrés salino y los valores de pH fueron máximos. Más aún, las concentraciones de las enzimas antioxidantes fueron las más altas en el color grisáceo verdoso, intermedias en el color intermedio, y las más bajas en el color amarillo verdoso después de la exposición al mismo tratamiento de pH. Los resultados sugirieron que los genotipos de los tres colores foliares de L. chinensis fueros tolerantes al estrés salino, y la tolerancia a la sal declinó de acuerdo al orden grisáceo verdoso > color intermedio > amarillo verdoso de L. chinensis. Este estudio puede proveer un mejor entendimiento de la adaptación intraespecífica de L. chinensis a suelos salinos.Fil: Zhou, C.. Chinese Academy of Science; China. Liaoning University; ChinaFil: Busso, Carlos Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Centro de Recursos Naturales Renovables de la Zona Semiárida. Universidad Nacional del Sur. Centro de Recursos Naturales Renovables de la Zona Semiárida; Argentina. Universidad Nacional del Sur. Departamento de Agronomía; ArgentinaFil: Yang, Y. G.. Liaoning University; ChinaFil: Zhang, Z.. Shenyang University; ChinaFil: Wang, Z. W.. Chinese Academy of Science; ChinaFil: Yang, Y. F.. Northeast Normal University; ChinaFil: Han, X. G.. Chinese Academy of Science; Chin