Significant Increase In Peroxidase Activity Research Articles

Increase of the degradation activity of Phanerochaete chrysosporium by hybridization with silica nanoparticles

Silica nanoparticle–hybridized Phanerochaete chrysosporium mycelium pellets were prepared by a simple one-step composite technology–based approach, involving co-culturing of silica nanoparticles with this fungus under mild culture conditions. The hybrid generated displays a significant increase in peroxidase activity, which reaches a maximum on the fifth day of culturing. Hybridization causes a morphology change and significantly increases the rate of crystal violet degradation, the amounts of excreted extracellular manganese peroxidase and hydrogen peroxide, and the rate of glucose consumption. The results show that hybridization with silica nanoparticles significantly increases of the degradation activity of P. chrysosporium cells.

Physiological and Biochemical Changes in Soybean Plants Caused by Iodine-Selenium Chelates and Phytopathogenic Bacteria

The search for effective and environmentally sound measures to fight against plant diseases caused by phytopathogenic microorganisms is of great importance. It is especially important to investigate alternative measures to protect cultivated plants that combine elements beneficial to human health such as iodine and selenium. Purpose. The study of physiological and biochemical changes in soybean leaves after artificial inoculation of plants with different strains of phytopathogenic bacteria on the background of pre-sowing treatment of seeds with a solution of iodine-selenium (I-Se) chelates. Methods. Soybean plants of the Artemis variety were grown in field conditions. Before sowing, the seeds were treated with a 1% I-Se chelated solution (I — 80 mg/L and Se citrate — 0.05 mg/L). The experimental plants were inoculated with phytopathogenic bacteria from the microbiological collection of the Zabolotny Institute of Microbiology and Virology of the National Academy of Sciences, namely Pseudomonas savastanoi pv. glycinea IMВ B-9190, P. agglomerans IMВ B-9185, and P. syringae pv. syringae IMВ B-8531. The contents of chlorophyll-a, b and carotenoids in the leaves were determined by extraction in DMSO followed by spectrophotometry. Catalase activity was determined by the method of titrimetric permanganatometry with a 0.01M solution of KMnO4, the activity to non-specific peroxidases — according to Boyarkin’s method. Evaluation of the photochemical activity of photosynthesis according to the parameters F0, Fv/Fm, and RFd was carried out by the method of induction of chlorophyll fluorescence using a portable device «Floratest». Statistical processing of experimental data was carried out using the built-in functions of the Microsoft Excel program. Results. The increase of peroxidase activity of leaves was revealed after both pre-sowing treatment with 1% I-Se solution of intact plants and inoculation of them with different strains of bacterial pathogens in the following order: I-Se > I-Se+P. syringae pv. syringae 8531 > I-Se+P. agglomerans 9185 > I-Se+P. savastanoi pv. glycinea 9190. The catalase activity of leaves tissues increased only when infected with a specific pathogen P. savastanoi pv. glycinea 9190 (by 20.6%). After artificial inoculation with strains of both specific and facultative bacterial pathogens and the pre-sowing treatment with I-Se, there was observed an increase in the quantum efficiency of PSII (Fv /Fm) and fluorescence in decline index (Rfd). An increase in the content of chlorophyll-a (by 18%), b and carotenoids (by 7%) in the leaves after the pre-sowing treatment with I-Se has been shown. The content of chlorophyll-a in soybean leaves due to pre-sowing treatment with I-Se had the most significant increase after inoculation of P. agglomerans 9185 (20%). Due to the inoculation with a specific pathogen P. savastanoi pv. glycinea 9190 (after the pre-sowing treatment with I-Se), the content of chlorophyll-a tended to decrease, and the content of chlorophyll-b decreased by 7%. The carotenoid content in leaves increased significantly at inoculation of plant with facultative pathogens: P. agglomerans 9185 (by 28.2%) and P. savastanoi pv. syringae 8531 (by 20.7%). The chlorophyll a/b ratio increased in all experimental variants. Conclusions. 1. It was found that pre-sowing seed treatment with 1% I-Se chelated solution results in increasing disease resistance in nonspecific adult soybean plants, including increasing their thermotolerance. This is evidenced by increasing the peroxidase activity of leaves and the content of photosynthetic pigments in natural conditions: chlorophyll-a and carotenoids. 2. Inoculation of soybean plants with a specific pathogen causes an increase in catalase and peroxidase activities in leaves. The significant increase in peroxidase activity after plant inoculation with facultative pathogens was shown. 3. A significant increase in the content of chlorophyll-a in soybean leaves after inoculation with P. agglomerans 9185 and pre-sowing treatment with I-Se was observed. The significant reduction of chlorophyll-b in leaves due to the inoculation of plants with P. savastanoi pv. glycinea 9190 and pre-sowing treatment of the seeds with I-Se was shown. The most significant increase in the content of carotenoids in leaves was detected after inoculation of plants with facultative pathogens — P. agglomerans 9185 and P. syringae pv. syringae 8531. 4. Significant stimulation of both maximum quantum yield of PSII photochemistry (Fv /Fm) and the rate of carbon assimilation (Rfd) due to the pre-sowing seed treatment with I-Se and inoculation of plants with different strains of phytopathogens was observed. It resulted from the activation of antioxidant systems and increased need for assimilates due to changes in plant metabolism.

Морфофізіологічні реакції мохів на дію абіотичних чинників на посттехногенних територіях видобутку сірки

The morphological structure of turfs and the activity of the main enzymes of antioxidant protection: peroxidase, superoxide dismutase (SOD) and catalase of the dominant species of mosses Barbula unguiculata Hedw,, Bryum caespiticium Hedw., Bryum argenteum Hedw. and Brachythecium salebrosum (Hoffm. eх F.Weber & D. Mohr) Schimp. from different transects of the northern exposure of sulfur mining dump No. 1 in the summer and autumn seasons were studied. It is shown that the morphological structure of the turfs of the mosses Bryum argenteum and Brachythecium salebrosum in the post-technological areas of sulfur mining is important for moisture conservation and depends on the microclimatic conditions of local growth and the life form of the species. It was found that the activity of enzymes depends on the species characteristics of mosses. The dependence of the activity of antioxidant enzymes in the investigated mosses on the intensity of light and temperature on the transects of dump No. 1 was defined. In the summer period, the highest indicators of the activity of antioxidant enzymes were noted in moss samples from the northern top of the dump, where the influence of high temperatures and light intensity, as well as lack of moisture, are particularly noticeable. Under the experimental conditions, in Barbula unguiculata and Bryum caespiticium from the northern top of the dump, under the influence of 24-hour exposure to a temperature of 42 °C, the most significant increase in peroxidase activity by 1.2–1.4 and SOD by 1.6–1.9 times was found. Increasing in peroxidase activity and SOD caused by hyperthermia were reversed by pretreatment with the protein biosynthesis inhibitor cyclohexamide, that may indicate about involvement of the protein synthesizing system in this process. It is likely that the increasing of the activity of antioxidant enzymes is caused primarily by the change in gene expression of stress proteins that control the synthesis of specific adaptogens and protectors, indicating that the extreme conditions of an anthropogenically transformed environment contribute to the development of forms of organisms with the highest potential opportunities.

Deficit irrigation effects on five pomegranate cultivars water use efficiency and biochemical parameters

The purpose of this study was to compare the effects of two irrigation levels [100 percent of field capacity (FC) (control)] and 30 percent FC (deficit irrigation) on vegetative growth, biochemical status, and water use efficiency of five pomegranate cultivars (Wonderful, Manfalouty, Acco, Assuity and 116) over two seasons in 2019 and 2020. The results showed that deficit irrigation reduced the dry weight of the shoots and roots, as well as the chlorophyll content of the leaves, in all the pomegranate cultivars. Meanwhile, under stress, proline content, total soluble sugars, total phenols, and peroxidase activity all increased significantly. The Manfalouty cultivar had the highest shoot and root dry weights, as well as the highest water use efficiency, proline content, and total phenols. Furthermore, when compared to other cultivars, the Wonderful cultivar had the highest chlorophyll content during both seasons. In comparison to the other cultivars studied, the Wonderful cultivar showed the limited or no significant increase in peroxidase activity. This could be due to a genotype’s variable peroxidase activity potential in pomegranate cultivars under water stress. The obtained results may indicate that Manfalouty and Wonderful cultivars are more tolerant of deficit irrigation than the other cultivars studied.

Infectious hypodermal and hematopoietic necrosis virus-like particle (IHHNV-VLP) induces peroxiredoxin expression and activity in Fenneropenaeus merguiensis

Virus like particles (VLPs) are non-infectious nanoparticles containing repetitive, high density viral epitopes on the surface and can prevent viral infections in aquatic animals. Here, we evaluated the immuno-stimulation effect of infectious hypodermal and hematopoietic necrosis virus like particle (IHHNV-VLP) using a next generation sequencing in Fenneropenaeus merguiensis to identify the important immune-related genes that may prevent viral infection. The in situ target of IHHNV was predominantly found in gill tissue following IHHNV-VLP administration in juvenile shrimp. Comparative transcriptome analysis in the injected gills showed that there were 326 unigenes expressed differently than the mock-injected samples. One of the most differential genes between the two animal groups was the antioxidative gene, peroxiredoxin (FmPrx), that was up-regulated after 6 h post-VLP injection. Phylogenetic tree analysis showed that this gene could be found among many shrimp species and was closely clustered among Prx families. The expression of FmPrx was also detected in all tissues examined, thus suggesting the multi-functional roles of this gene in many tissues. Administration of IHHNV-VLP in vivo led to a significant increase in peroxidase activity in gill tissue—approximately two-fold versus control animals; the WSSV copy number was significantly reduced. These data suggest that IHHNV-VLP exerts an immune-stimulating effect by enhancing the level of immune-related genes including FmPrx and its corresponding peroxidase activity, which are a well-known part of the shrimp innate immune system.

Oxidative stress in moss Bryum caespiticium (Bryaceae) under the influence of high temperature and light intensity in a technogenically transformed environment

Mosses are pioneer plants in post-technogenic areas. Therefore, the question of adaptive reactions of mosses from these habitats represents a scientific interest. The research is devoted to the study of adaptive changes in the metabolism of the dominant moss species Bryum caespiticium Hedw., collected in the devastated territories of the Novoyavorivsk State Mining and Chemical Enterprise (SMCE) “Sirka (Sulfur)” exposed to hyperthermia and insolation, which cause oxidative stress in plants. The influence of these stressors on the activity and thermal stability of antioxidant enzymes, hydrogen peroxide content, anion radical generation and accumulation of prooxidant components in moss shoots was studied. The activity and thermal stability of peroxidase and superoxide dismutase (SOD) were analysed forB. caespiticium moss from different locations of northern exposure at the sulfur mining dump No 1 in summer and autumn. We established the dependence of the activity of antioxidant enzymes of moss on the intensity of light and temperature on the experimental plots of the dump No 1. In summer, the highest activity and thermal stability rates of peroxidase and SOD were observed. Under the conditions of the experiment in shoots of В. caespiticium from the northern peak of the dump under the influence of 2 hours temperature action (+ 42 ºС) the most significant increase in peroxidase activity was found by 1.78 times and SOD by 1.89 times, as well as increase in its thermal stability by 1.35–1.42 times, respectively. The increase in peroxidase and SOD activity, as well as the increase in their thermal stability caused by hyperthermia were negated by pre-processing with a protein biosynthesis inhibitor cyclohexamide, which may indicate the participation of the protein-synthesizing system in this process. The effect of increasing the thermal stability of enzymes can be considered as a mechanism of adaptation of the protein-synthesizing system to the action of high temperatures. Increase in the activity and thermal stability of antioxidant enzymes is caused primarily by changes in the expression of stress protein genes, which control the synthesis of specific adaptogens and protectors. The obtained results indicate that the extreme conditions of the anthropogenically transformed environment contribute to the development of forms with the highest potential abilities. The mechanism of action of high temperatures is associated with the development of oxidative stress, which is manifested in the intensification of lipid peroxidation and the generation of superoxide anion radical. It was found that temperature stress and high insolation caused an increased generation of superoxide anion radical as the main inducers of protective reactions in the samples of B. caespiticium from the experimental transect of the sulfur mining heap. It is known that the synthesis of Н2О2 occurs under stress and is a signal to start a number of molecular, biochemical and physiological processes of cells, including adaptation of plants to extreme temperatures. It is shown that high temperatures initiate the generation of hydrogen peroxide. Increased reactive oxygen species (ROS) formation, including Н2О2, under the action of extreme temperatures, can cause the activation of signaling systems. Therefore, the increase in the content of Н2О2 as a signaling mediator is a component of the antioxidant protection system. It is determined that adaptive restructuring of the metabolism of the moss В. caespiticium is associated with the accumulation of signaling prooxidant components (diene and triene conjugates and dienketones). The increase in primary lipid peroxidation products, detected by us, under the action of hyperthermia may indicate the intensification of free radical oxidation under adverse climatic conditions in the area of the sulfur production dump, which leads to the intensification of lipid peroxidation processes. The accumulation of radical and molecular lipid peroxidation products are signals for the activation of protective systems, activators of gene expression and processes that lead to increased resistance of plants.

Reaction to Hydrogen-Peroxide Action in Nicotiana tabacum Plants Transformed by the Cholinoxidase Gene (codA)

Genetic engineering of glycine betaine (GB) synthesis offers a new approach to improvements in the productivity and stress resistance of cultivated plants. The possible effect of the bacterial heterologous sequence on the reaction of plants under oxidative stress (OS) induced by 3 mM of hydrogen peroxide (H2O2) was determined. The independent transgenic tobacco lines (Nicotiana tabacum L.) Cod 16 and Cod 45 with the choline oxidase (codA) gene from Arthrobacter gloiformis, which is responsible for GB synthesis, were used. The transgenic lines differed from wild-type plants with lower resistance to H2O2, which led to a more significant decrease in the pool of photosynthetic pigments and a greater intensity of lipid peroxidation and dynamics of superoxide dismutase (SOD) and peroxidase (PO) activity. In terms of OS manifestation, transgenic lines with initially similar values of GB accumulation (0.825–0.910 mmol/g) had significant differences among themselves. In the Cod 16 line, the reaction to OS induction was earlier (1 h after H2O2 treatment), and there was a more significant increase in PO activity and proline content than in the Cod 45 line and the original variety. In the Cod 45 line, there is a significant increase in SOD activity and proline content in response to OS induction 24 h after treatment, and, in contrast to the wild-type plants and the Cod 16 line, it is accompanied by a significantly higher content of carotenoids in the leaves. When genetic-engineering methods are used to increase the productivity and resistance of plants to stress, it is necessary to take into account the functional interaction of antioxidants and osmoprotectors.

Активність та ізоферментний склад пероксидази листя Robinia pseudoacacia L. за дії Parectopa robiniella Clemens, 1963

Іn recent times R. pseudoacacia has been suffering from populations of new pests, which cause serious economic damage to this strategic species. Therefore, studying the features of plant defense responses against harmful insects is of great importance for biodiversity conservation for preserving this species in natural and artificial plantings. The aim of the study was to analyze the peculiarities of the activity and isoenzyme composition of peroxidase in R. pseudoacacia leaves during attacks by the invading insect P. robiniella. In the green plantations of Dnipro city, as the object of research, six groups of Robinia pseudoacacia L. model trees of different ages (5 and 35–40 years of age) with the existing leaf damages by P. robiniella leaf blotch miner were identified. Differences in benzidine-peroxidase activity were found in the leaves of 5- and 40-year-old R. pseudoacacia trees. In 35‒40-year-old trees with the presence of leaf blotch mi­ners, the leaves showed a tendency to increase BPOD activity by 24.6% vs control. While in young plants, a significant increase in peroxidase activity was found by 3.8 times due to mechanical damage of the leaves by the miner compared to the control. The revealed significant increase (by 63.2%) in the activity of guaiacol-peroxidase of black locust indicates its active participation in enhancing the barrier functions of leaf cells against P. robiniella, and it indicates the promising use of the enzyme as a biomarker for pest influence. The composition of benzidine-peroxidase isoenzymes was analyzed by electrofocusing. The main pattern of changes in the expressiveness of benzidine-peroxidase due to damage of leaves by a pest was a quantitative redistribution of activity between different molecular forms of peroxidase. Several enzyme isoforms from the highly acidic pH zone showed a significant activity increase in R. pseudoacacia leaves damaged by P. robiniella; this especially applies to the peroxidase system of young black locust plants. The increase in bensidine- and guajacol-peroxidase activity under the influence of leaf miner may be explained by a change in the gene expression of individual isoforms of peroxidases, which is confirmed by the results of studying the relative share of peroxidase molecular forms with isoelectrofocusing. Calculation of the internal diversity index (KD) of IEF benzidine-peroxidase spectra showed that the studied peroxidase spectra of young and medieval trees of control and experimental samples of R. pseudoacacia leaves differ significantly in the level of complexity. Under the influence of the invader the level of complexity increased. The study of the reaction of black locust and the mechanisms of its protection against mechanical damage by phytophages with the involvement of a larger range of enzymes in further research can serve as a theoretical basis for species selection and management to restore it under biotic stress.

Regulated Deficit Irrigation at Special Development Stages Increases Sugar Beet Yield

Core Ideas Different growth stages of drip‐irrigated sugar beet can bear different water deficit level. The canopy development stage is the most water‐sensitive period of the sugar beet. Regulated deficit irrigation could increase beet yield and reduce the consumption of water resources in arid land. ABSTRACTThe shortage of water resources promotes the development of water saving irrigation in arid land. Regulated deficit irrigation (RDI), as one of the water‐saving irrigation technologies through applying a certain amount of water stress to the crops to promote the distribution of the photosynthate of crops to the needs of the tissues and organs, can save water and may increase yield. Our study evaluated the effect of the RDI on the sugar beet (Beta vulgaris L. cv. Beta356). Seven irrigation treatments were applied based on the growth stages of sugar beet (canopy development, storage root development, and sugar accumulation) and water deficit levels (30, 50, and 70% of field capacity [FC]). The yield, quality, sugar yield, irrigation water use efficiency (IWUE), and agronomic physiological traits of sugar beet were evaluated. Moderate water deficit (50% of FC) during canopy development increased sugar yield by 27% compared with the control (70% of FC during the whole growth stages). Severe (30% of FC) water deficit increased sugar yield by 45% during storage root development, and by 55% during sugar accumulation. The RDI during canopy development and storage root development inhibited leaf growth but did not affect yield. Malondialdehyde content and relative conductivity increased significantly when soil water content dropped to the irrigation threshold levels (i.e., 30% and 50% of FC) before rehydration during canopy development. After rehydration, there were significant increases in peroxidase activity and proline content (indicators of antioxidant defense and osmotic stress). Our results indicated that RDI increased yield at 30% and 50% of FC during three growth stages (canopy development, storage root development, and sugar accumulation) of sugar beet, which reduced irrigation water requirements. RDI could be applied as a strategic action for crop sustainability and water saving in arid land.

Вплив фунгіцидів на активність пероксидаз у Arabidopsis thaliana

Fungicides that effectively protect fruit trees, vegetable and decorative plants are widely used to control fungal diseases of important agricultural crops. All fungicides are divided into two - contact and systemic - groups. Contact fungicides contain compounds of copper or sulfur, which have a prophylactic effect. Systemic or therapeutic fungicides kill the mycelium, preventing its growth in the parenchyma of plants. Widely used systemic fungicides contain benzimidazoles and strobirulins. Although fungicides demonstrate the positive effects against fungal diseases, in some cases the negative effects of these compounds on plant growth and development were found. These effects are primarily due to the fact that fungicides represent a stress factor for plants. Under the action of stress factors, an increased amount of reactive oxygen species (ROS) is generated in plants. The increase of ROS content in the plant cell leads to oxidative stress. To counteract this stress, the mechanisms of harmful ROS detoxification are present in the plant cell. These mechanisms include, first of all, the antioxidant enzymes, like ascorbate and guaiacol peroxidases. Contact fungicides affect the antioxidant system of plants. However, the role of antioxidant enzymes in the action of systemic fungicides has not been clarified. Therefore, the aim of our study was to investigate the role of ascorbate peroxidase (APX) and guaiacol peroxidase (POD) in the response of the model plant Arabidopsis thaliana to the treatment by contact (Median) and systemic (Strobi, Topsin M) fungicides. It was found that after application of systemic fungicides Strobi and Topsin M no significant changes of APX activity occur. In contrast, in the plants treated with contact fungicide Median, APX activity increased by 46.3% compared to the control plants. Evaluation of POD activity revealed that the application of Strobi and Topsin M does not affect the activity of this enzyme. However a significant increase of POD activity by 42.6% was observed after the treatment with Median. Thus, the antioxidant system of the model plant A. thaliana specifically responds to the treatment of plants with different fungicides. It was shown that fungicides of systemic action like Strobi and Topsin M do not cause oxidative stress in plant cell. The contact fungicide Median leads to the activation of antioxidant enzymes, such as APX and POD. Key words: fungicides, reactive oxygen species (ROS), antioxidant system, APX, POD, Arabidopsis thaliana.

Investigating the effects of Citrullus colocynthis pulp on oxidative stress in testes and epididymis in streptozotocin-induced diabetic male rats

Diabetes mellitus is one of the most common metabolic diseases in humans, affecting 100 million people around the world. Investigating the effects of Citrullus colocynthis pulp on oxidant and antioxidant factors of testes and epididymis in streptozotocin-induced diabetic male rats. Thirty two male rats were divided into four groups (n=8) 1) N (normal) group, 2) N+C group, 3) D (diabetic) group and 4) D+C group. Groups N and D received normal saline 2 ml orally for two weeks and groups N+C and D+C received 10 mg/kg.bw Citrullus colocynthis pulp orally for two weeks. Diabetes was induced by single intraperitoneal injection of streptozotocin (STZ) at 65 mg/kg. D group had a significant increase in H2O2 (Hydrogen peroxide) and MDA (malondialdehyde) concentrations, and CAT (catalase) activity, and also a significant decrease in Peroxidase (POD) activity compared to N group. D+C group had a significant decrease in H2O2 and MDA concentrations and, CAT activity and significant increase in POD activity compared to D group. Citrullus colocynthis pulp in two weeks had beneficial effects on oxidants and antioxidants changes in reproductive system in streptozotocin-induced diabetic rats.

Varietal differences in the growth of rice seedlings exposed to perchlorate and their antioxidative defense mechanisms.

A hydroponic experiment was conducted to investigate perchlorate (ClO4 (-) ) phytotoxicity in different rice varieties. Considerable variations were observed when 24 rice varieties were treated with ClO4 (-) . The shoot height, root length, and biomass of most varieties were significantly reduced by ClO4 (-) . The roots were more sensitive than the shoots. Hierarchical clustering analysis demonstrated primarily 4 groups: ClO4 (-) -sensitive, medium ClO4 (-) -sensitive, medium ClO4 (-) tolerant, and ClO4 (-) -tolerant. Gannuoxiang (a ClO4 (-) -tolerant variety) and IR65598-112-2 (a ClO4 (-) -sensitive variety) were chosen to explore their antioxidant response when exposed to 0.2 mmol/L, 2.0 mmol/L, and 4.0 mmol/L ClO4 (-) . The results showed that the activities of superoxide dismutase and catalase increased in the shoots and roots of gannuoxiang with increasing doses of ClO4 (-) , but both of them decreased at higher concentrations of ClO4 (-) in IR65598-112-2. The addition of ClO4 (-) led to a significant increase in peroxidase activities for both of the varieties, whereas the increase was more pronounced in gannuoxiang than in IR65598-112-2. No significant difference was found in malondialdehyde (MDA) contents in gannuoxiang, whereas the addition of ClO4 (-) increased the MDA level significantly in IR65598-112-2. The results indicated that gannuoxiang has higher activities of antioxidant enzymes than IR65598-112-2 to cope with oxidative damage caused by ClO4 (-) stress, which may be the main cause of its high tolerance.

Effect of defoliation on the growth and metabolism of Scots pine

The effect of spring defoliation on different aspects of growth and metabolism of 10-year Scots pine trees (Pinus silvestris L.) in natural stands of the Krasnoyarsk forest-steppe region have been studied. These aspects include the structure of annual xylem and phloem increments, the content of starch and photosynthetic pigments in phloem, and the activity of antioxidative enzymes in xylem and phloem. It is shown that defoliation reduces shoot elongation, as well as the length and mass of needles and width of annual rings in xylem and phloem. It also stimulates late wood formation, an increase in total contents of photosynthetic pigments in the needles of newly formed shoots, and a reduction of starch contents in stem phloem. A significant increase of peroxidase activity in the xylem of defoliated trees can be a sign of oxidative stress. Defoliation has an evident negative effect on the formation of the annual rings of xylem, but does not have that strong an impact on phloem genesis. In general, during defoliation, the reserve function of the trees prevails over the growth function.

Exogenous CaCl2 promoted the indole alkaloid accumulation in seedlings of Catharanthus roseus under NaCl stress

A sandy culture experiment was conducted to investigate the effects of exogenous CaCl2 on the indole alkaloid accumulation in Catharanthus roseus under salt stress. One-month seedlings of C. roseus were treated with the different concentrations of NaCl (0, 50, and 100 mmol l− 1) and 7.5 mmol l− 1 CaCl2. The plant samples were analyzed after 7 days of the treatments. The NaCl-stressed plants showed decrease of fresh and dry weight and increase of malondialdehyde (MDA) content compared to control. Tryptophan decarboxylase (TDC) activity increased significantly under 50 mmol l− 1 NaCl without CaCl2 addition, 50 mmol l− 1 NaCl with 7.5 mmol l− 1 CaCl2, and CaCl2 treatment without NaCl addition. There was a significant increase in peroxidase activity under NaCl stress compared to control. The vindoline, catharanthine, vincristine, and vinblastine contents increased under salt stress (especially with 50 mmol l− 1 NaCl treatment with or without CaCl2). Addition of CaCl2 to NaCl-stressed plants increased biomass, TDC activity, vindoline, and catharanthine contents and lowered MDA and vincirstine contents compared to the plants without CaCl2. The plants treated with CaCl2 alone showed higher TDC activity, vindoline, catharanthine, and vinblastine content when compared to control. The results showed that exogenous CaCl2 could promote the indole alkaloid metabolism under salt stress.

CHEMICAL INDUCTION OF SYSTEMIC AQUARID RESISTANCE AND EFFECT OF THEIR APPLICATION TIME ON RICE BLAST “MAGNAPORTHE GRISEA” INFECTION TO CULTIVARS SAKHA101 AND SAKHA104.

Blast is the most destructive rice diseases in Egypt and could cause significant yield losses. The variable nature and race shifting of the pathogen often leads to resistance breakdown of high yielding varieties such as Sakha 101 and Sakha 104. Chemical control is not always effective and often has an undesirable impact on the environment and human health. Some antioxidants and organic compounds; Bion (BTH, benzo (1,2,3) thiadiazole-7-carbothioic acid S-methyl ester), at concentrations of 0.1, 0.3 and 1 mM; Salicylic acid 8 mM (SA), Benzoic acid 8 mM, Nicotinic acid 8mM, H2O2 30%, and Compost tea 100% were directly applied as foliar spray of 21-days old seedlings prior to challenge inoculation with Magnaporthe grisea to promote blast resistance in rice leaves. Under greenhouse condition, artificial inoculation was applied after four fixed periods (5, 10, 15 and 20 days after treatment (DAT)) from the application date of all antioxidants. All antioxidants and compost tea reduced the infection percentage compared with untreated check especially with the inoculation 5 DAT. Concerning infection % of rice blast, there are a remarkable significant differences among all antioxidants compared with control. All antioxidants were significantly reduced the infection percentage. Salicylic acid was the most effective antioxidant at concentration of 8 mM, it recorded 4.9, 9.7, 28 and 15.5 % with 5, 10, 15 and 20 DAT, respectively. Also, Bion (BTH) at both concentrations 0.3 and 1.0 mM exhibited a significant reduction in infection %. The rest of antioxidants exhibited significant increase in infection % especially under late induced periods from 10-20 DAT.The optimal period of induced resistance, was artificial inoculation 5 DAT which recorded the lowest infection percentage compared with the inoculation after 10 to 20 days. With both Salicylic acid and Bion, artificial inoculation 5 DAT to 15 days led to a significant reduction in disease infection percentage and severity. While the resistance was remarkably sharply decreased after 15 days from induced resistance treatment with all antioxidants. Optimal induced period of Benzoic acid, Nicotinic acid, H2O2, Compost tea and Cinnamic acid was continued from 5 to 10 days only. Treatment with salicylic acid at 8 mM recorded the lowest area under disease progress curve ( AUDPC), 409.48 compared by the control 1304.24, followed by Bion at 0.3 and 1.0. However, BTH and Salicylic acid had neither suppression nor fungicidal effect on linear growth, spore germination, sporulation and appressorium formation of Magnaporthe grisea in vitro. Concerning Peroxidase (PO) activity with both SA 4mM and BTH increased continuously in 0-25 min. intervals and markedly significant increase, although PO activities reach to be maximum at 25 min. in which was higher than that control and other treatments. SA had the highest activities in period intervals followed by BTH. Compost Tea and H2O2 showed no significant increase in PO activity with all time intervals while the other treatments showed PO activities only in 10-20 min. compared to control. Polyphenoloxidase (PPO) activity has gradually decreased during intervals 0 to3 min. Spraying by SA 4mM recorded the highest enzyme activity in all intervals and markedly significant increase in activity. For growth characters, all applications of antioxidants treatments led to a significant increase in leaf area, plant height, chlorophyll content, fresh and dry weight of rice leaves compared to control. In general, Sakha 101 rice cultivar exhibited the highest response to applications of all antioxidant compared with other cultivar Sakha 104 that have a weak response of growth characters to antioxidants application. Abbreviations: BTH, benzo (1,2,3) thiadiazole-7-carbothioic acid S-methyl ester; JA, jasmonic acid; SA, salicylic acid; SAR, systemic acquired resistance.

Changes in Cell/Tissue Organization and Peroxidase Activity as Markers for Early Detection of Graft Incompatibility in Peach/Plum Combinations

Changes in cell and tissue organization and in peroxidase activity have been analyzed to find early markers to predict graft incompatibility occurrence in peach/plum combinations (Prunus persica/Prunus spp.) at 5 months after grafting in the dormancy period. Different compatible and incompatible peach/plum grafts were grown for 5 months in a nursery. The cellular study of the graft interface revealed structural changes associated with graft incompatibility symptoms. The main structural features were cambium cell disorganization, less differentiation of vascular tissues, degeneration of phloem and xylem cells, and accumulation of phenols at the graft interface after 5 months of graft development. The peroxidase study was performed during dormancy and the vegetative growth period, and revealed a significant increase in peroxidase activity in the incompatible unions, with significant differences between compatible and incompatible grafts. Analysis of gel profiles of nonbudded rootstocks and scions revealed an anodal isoperoxidase band [relative front (Rf) = 0.48] present in scions and compatible rootstocks, and another isoperoxidase band (Rf = 0.53) only present in the incompatible rootstocks. Our results show that the analysis of cell organization to detect early structural events and the evaluation of peroxidase activity at graft unions constituted feasible and convenient methods for early diagnosis of graft incompatibility. Also, it was suggested that the presence of band Rf = 0.48 in plum rootstocks and peach cultivars could be used as a marker to predict graft compatibility for peach scions and plum rootstocks.

Partial purification and characterization of a copper-induced anionic peroxidase of sunflower roots

Treatment of 14-day-old sunflower seedlings with a toxic amount of copper (50 microM of CuSO(4)) during 5days caused significant increase in peroxidase activity in roots. Qualitative analysis of soluble proteins using native anionic PAGE followed by detection of peroxidase activity with guaïacol as electron donor in the presence of H(2)O(2) revealed five stimulated peroxidases, named A1, A2, A3, A4, and A5. These peroxidases had differential behavior during the period of treatment. A1, A2, A3 and A4 were stimulated in the first period of stress, but rapidly suppressed at 72h. A5 showed a progressive stimulation which was even increased at 120h. A1 was partially purified, identified using liquid chromatography coupled to mass spectrometry (LC-MS/MS), and characterized. Effects of pH and temperature on its activity were determined with guaïacol as electron donor. Optima were obtained at pH 8 and at 40 degrees C. Analysis of substrate specificity showed that A1 was active on coniferyl alcohol but not on IAA. Enzymatic activity was inhibited by a high concentration of H(2)O(2).

Protection of apple against fire blight induced by an hrpL mutant of Erwinia amylovora

A regulatory hrpL non-virulent mutant of Erwinia amylovora is effective in controlling fire blight disease when inoculated on apple seedlings simultaneously with the pathogenic parental strain. Mechanisms involved in this protective effect were investigated. The use of two marker genes, uidA and lacZ, expressed in the hrpL mutant and the pathogenic strain, respectively, allowed to localize simultaneously the two inoculated strains in plant tissue. An anti-β-glucuronidase antibody was also used to detect the hrpL mutant. Both techniques indicated that the two strains localized mainly in separate areas of the leaf tissue. In addition, leaves infiltrated with the hrpL mutant exhibited a significant increase in peroxidase activity in contrast to a hrp secretion mutant known to be less effective in the protection. It is suggested that protection obtained with the hrpL mutant relies on the physical separation between the mutant and the parental strain after co-inoculation and the rapid and sustained activation of plant defense mechanisms in reactive tissue, i.e. not invaded by the virulent strain.

Xanthomonas oryzae pv. oryzae infection triggers accumulation of phenolics, defense-related enzymes and thaumatin-like proteins in rice leaves

The effect of Xanthomonas oryzae pv. oryzae infection on induction of phenylalanine ammonia-lyase (PAL), peroxidase (PO), phenolics and thaumatin-like proteins (TLPs) in rice was studied. PAL activity increased significantly one day after inoculation with X. o. pv. oryzae and the maximum enzyme activity was observed two days after inoculation. The phenolic content in rice leaves increased significantly one day after inoculation and the maximum accumulation of phenols was observed two days after inoculation. Significant increase in peroxidase activity was observed in rice leaves one day after inoculation with X. o. pv. oryzae. Isozyme analysis indicated that three peroxidase isozymes (PO-1, PO-2 and PO-3) were induced after inoculation with X. o. pv. oryzae. Immunoblot analysis of protein extracts from control and pathogen inoculated rice plants revealed the induced accumulation of 16 and 24 kDa TLPs in rice leaves in response to X. o. pv. oryzae infection. TLP mRNA accumulation was induced strongly in rice leaves in response to infection by X. o. pv. oryzae.

Antioxidant enzyme activity in endemic Baikalean versus Palaearctic amphipods: Tagma- and size-related changes

The activities of key antioxidant enzymes in two endemic Baikalean amphipod species: Pallasea cancelloides (Gerstf), Eulimnogammarus verrucosus (Gerstf) and the widely distributed Palearctic species Gammarus lacustris (Sars) were studied. This work was done to prove or disprove the hypothesis that Baikalean endemics have specifics in antioxidants system different from Palearctic species. The activities of antioxidant enzymes peroxidase, catalase and glutathione- S-transferase were measured in different sections (tagmata) of the amphipods' bodies as well as in different size groups. Well expressed tagma-related differences in peroxidase activity as well as smaller differences in catalase activity were shown in all studied species. There were no measured differences in glutathione- S-transferase activity among body sections. The existence of size-related changes in some antioxidant enzymes and the difference in such changes between Baikalean and Palearctic amphipods were noted. A significant increase in peroxidase activity with the size was found in both Baikalean species while a significant decrease in peroxidase activity was observed in the Palearctic G. lacustris. In Baikalean P. cancelloides, a significant decrease of catalase activity with the increase in age of crustaceans was noted, while in E. verrucosus no such relationship was found. In the Palearctic G. lacustris, a significant increase in catalase activity with the increase in size was noted. All species are shown to have no size-related differences in glutathione- S-transferase activity. The differences between species as well as between both different tagmata and size-classes within a particular species were estimated. It was assumed that the estimated differences in enzymes activity most likely depend on interspecific variation, rather than on conditional specifics in Lake Baikal.