Activities Of Oxygen Scavenging Enzymes Research Articles

Genome wide identification of the trihelix transcription factors and overexpression of Gh_A05G2067 (GT-2), a novel gene contributing to increased drought and salt stresses tolerance in cotton.

We identified 102, 51 and 51 proteins encoded by the trihelix genes in Gossypium hirsutum, Gossypium arboreum and Gossypium raimondii, respectively. RNA sequence data and real‐time quantitative polymerase chain reaction analysis showed that Gh_A05G2067 (GT‐2) was highly upregulated under drought and salt stress conditions. Transient expression of GT‐2‐green fluorescent protein fusion protein in protoplast showed that GT‐2 was localized in the nucleus. The overexpression of GT‐2 conferred an enhanced drought tolerance to cotton, with lower malondialdehyde, hydrogen peroxide contents and higher reactive oxygen scavenging enzyme activities. Moreover, chlorophyll content, relative leaf water content (RLWC), excised leaf water loss (ELWL) and cell membrane stability (CMS) were relatively stable in the GT‐2‐overexpressed lines compared to wild‐type (WT). Similarly, stress‐responsive genes RD29A, SOS1, ABF4 and CBL1 were highly upregulated in the GT‐2‐overexpressed lines but were significantly downregulated in WT. In addition, the GT‐2‐silenced cotton plants exhibited a high level of oxidation injury, due to high levels of oxidant enzymes, in addition to negative effects on CMS, ELWL, RLWC and chlorophyll content. These results mark the foundation for future exploration of the trihelix genes in cotton, with an aim of developing more resilient, versatile and highly tolerant cotton genotypes.

Differential Frost Tolerance and Enzymatic Activities in the Leaves and Immature Fruits of Loquat (Eriobotrya japonica Lindl.)

In this experiment, five commercial cultivars and one wild species of loquat were used to investigate frost tolerance and enzymatic activities in leaves and young fruits under cold stress at -3℃. The frost injury, malondialdehyde (MDA) content, and oxygen-scavenging enzyme activities of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT) and ascorbate peroxidase (APX) were studied. This results showed that the wild species ‘Wild Oak-leaf’ loquat was the most frost tolerant among accessions tested, followed by the cultivar ‘Golden Block’. Other cultivars, ‘Wu Gong Bai’, ‘Taicheng 4’, ‘Xiangzhong 11’ and ‘Zaozhong 6’, were relatively weak in frost tolerance. The enzymatic activities of SOD, POD and CAT increased initially and then decreased as the exposure time increased. However, the enzymatic peak occurred later in the frost-tolerant accession than in the frost-sensitive accession. The correlation coefficients of MDA contents between leaves and immature fruits were from 0.93 to 0.99 in the five commercial loquat cultivars. For the ‘Wild Oak-leaf’ loquat, the correlation coefficients of MDA and POD were 0.98 and 0.95, respectively, but the coefficients for SOD, CAT and APX were relatively low. In general, there were good correlations between loquat leaves and immature fruits in MDA content and enzyme activities. These results indicate that analysis of these physiological and biochemical activities in loquat leaves could potentially be used to predict the cold tolerance in loquat at immature fruit stage and to accelerate breeding programs for cold tolerance in loquat.

ROS and salicylic acid (SA) play roles on the resistance establishment of the potato cultivar Zihuabai to Phytophthora infestans

Due to its high resistant to potato late blight, Zihuabai has become the most popular potato variety in the Inner Mongolia region of China. In this study, experiments were carried out to investigate the resistance mechanism of potato cultivar Zihuabai to late blight. Accumulation of reactive oxygen species (ROS), activities of oxygen scavenging enzymes, and transcription level of some resistance genes were determined in both resistant and susceptible potato cultivars inoculated with Phytophthora infestans, which causes potato late blight. Our results show that both ROS accumulation and oxygen scavenging enzymes activities were quicker and higher in the resistant cultivar Zihuabai compared to those of the susceptible cultivar Shepody. In addition, transcript levels of genes which are involved in resistant signaling pathways (salicylic acid and jasmonic acid pathways) were detected through RT-PCR. Our data indicated that together ROS and SA are the main signaling molecules regulating the resistance of potato cultivar Zihuabai to P. infestans.

Antioxidant Metabolism during Fruit Development of Different Acerola (Malpighia emarginata D.C) Clones

The present research work describes the major changes in the antioxidant properties during development of acerola from five different clones. Ripening improved fruit physicochemical quality parameters; however, total vitamin C and total soluble phenols (TSP) contents declined during development, which resulted in a lower total antioxidant activity (TAA). Despite the decline in TSP, at ripening, the anthocyanin and yellow flavonoid content increased and was mainly constituted of cyanidin 3-rhamnoside and quercetin 3-rhamnoside, respectively. The activities of oxygen-scavenging enzymes also decreased with ripening; furthermore, the reduction in vitamin C was inversely correlated to membrane lipid peroxidation, indicating that acerola ripening is characterized by a progressive oxidative stress. Among the studied clones, II47/1, BRS 237, and BRS 236 presented outstanding results for vitamin C, phenols, and antioxidant enzyme activity. If antioxidants were to be used in the food supplement industry, immature green would be the most suitable harvest stage; for the consumer's market, fruit should be eaten ripe.

Effects of Pb2+ on the active oxygen-scavenging enzyme activities and ultrastructure in Potamogeton crispus leaves

The effects of various concentrations of Pb2+ on the antioxidant enzyme activities and the ultrastructure in Potamogeton crispus leaves were studied. Peroxidase (POD) activity and malondialdehyde (MDA) content peaks were observed with an increase in Pb2+ concentration, whereas superoxide dismutase (SOD) and catalase (CAT) activities decreased firstly and then rose. Meantime, the chlorophyll content declined with increasing Pb2+ concentration. Simultaneously, high concentrations of Pb2+ aggravated ultrastructural damage to the leaf cells including swelling of chloroplasts, disruption and disappearance of chloroplast envelopes; swelling of mitochondrial cristae, deformation and vacuolation of mitochondria; condensation of chromatin, dispersion of nucleoli, and disruption of nuclear membrane. Changes in antioxidant enzyme activities and damage to fine structure are the results of lead-induced ROS accumulation. The estimated lethal concentration to P. crispus ranged from 10 to 15 mg/l lead.

Antioxidant activity and oxygen-scavenging system in orange pulp during fruit ripening and maturation

The antioxidant activity (ferric reducing/antioxidant power, FRAP) and oxygen-scavenging system of pulps during the fruit ripening and maturation were investigated in three cultivars of sweet orange ( Citrus sinensis (L.) Osbeck). The highest FRAP values and activities of antioxidant enzymes and contents of nonenzymes were detected in ‘Red Flesh’ navel orange. The activities of oxygen-scavenging enzymes, superoxide dismutase (SOD), catalase (CAT), guaiacol peroxidase (G-POD), decreased with ripening and maturation of fruit. Ascorbate peroxidase (AsA-POD) and dehydroascorbate reductase (DHAR) activities were also stably declined, whereas glutathione reductase (GR) activity and nonenzymes in the ascorbate–glutathione cycle displayed a single-peak pattern which paralleled the significant changes in FRAP values. In addition, the ratios of ascorbate/dehydroascorbate (AsA/DHAsA), reduced glutathione/oxidized glutathione (GSH/GSSG) were also decreased. Changes in the activities of antioxidant enzymes and the contents of nonenzymes during ripening indicated that the antioxidant system plays a fundamental role in the ripening of orange fruits.

Effects of La3+ on the Active Oxygen-Scavenging Enzyme Activities in Cucumber Seedling Leaves

The effects of La3+ on the antioxidant enzyme activities and the relative indices of cellular damage in cucumber seedling leaves were studied. When cucumber seedlings were treated with low concentrations of LaCl3 (0.002 and 0.02 mM), peroxidase (PO) activity increased, and catalase (CAT) activity was similar to that of control leaves at 0.002 mM La3+ and increased at 0.02 mM La3+, whereas superoxide dismutase (SOD) activity did not change significantly. The increase in the contents of chlorophyll (including chlorophylls a and b), carotenoids in parallel with the decrease in the level of malondialdehyde (MDA) suggested that low concentration of La3+ promoted plant growth. However, except the increase in SOD activity at 2 mM La3+, CAT and PO activities and the contents of pigments decreased at high concentrations of La3+ (0.2 and 2 mM), leading to the increase of MDA content and the inhibition of plant growth. It is suggested that lanthanum ion is involved in the regulation of active oxygen-scavenging enzyme activities during plant growth.

Active Oxygen Scavenging Enzyme Activities and Glutathione, Ascorbic Acid and Lipid Peroxidation Levels in Developing Vitis Vinifera L. Leaves and Berries

ABSTRACTVariations and activities of active oxygen radical scavenging enzymes and the level of glutathione (GSH), lipid peroxide and ascorbic acid levels were measured during the developmental cycle and their relationship were examined in two grape cultivars, Kalecik Karasi and Sultani Çekirdeksiz (Vitis vinifera L.). The catalase activity was very low and did not change during growth, the activity of superoxide dismutase significantly decreased through the maturity. There was no significant difference between two cultivars for glutathione peroxidase activity at maturity. The maximum glutathione level was observed in berries of two Vitis vinifera L. cultivars. Ascorbic acid levels were significantly increased in young and old leaves. Changes in the activities of antioxidant enzymes and levels of glutathione, ascorbic acid and thiobarbituric acid reactive substances were related to the development of berries and leaves.

Ｃ３，Ｃ４とＣＡＭ植物における過酸化水素含量と抗酸化酵素活性の差異

通常の生育条件下のC3植物9種, C4植物7種とCAM植物9種について, 晴天日の午前中に葉をサンプリングし, H2O2含量および抗酸化酵素のSOD, APXとCAT活性を調べた.その結果, C3とC4植物の葉中のH2O2含量は同レベルで, CAM植物より少なかった.C3植物ではSOD, APXおよびCATともに高い活性を示したのに対し, CAM植物ではいずれの酵素ともに低い活性を示した.C4植物はC3植物より高いAPX活性と低いCAT活性を示した.これらのことから, 植物は光合成型によってH2O2などの活性酸素の酵素的な消去機能を異にすることが明らかになった.

Methyl Jasmonate Reduces Water Stress in Strawberry.

The effect of methyl jasmonate (MJ) on changes of oxygen-scavenging enzyme activities and membrane lipid composition was studied in strawberry leaves under water stress. Under water stress, MJ treatment reduced the increase of peroxidase (EC 1.11.1.7; POD) activity, maintained higher catalase (EC 1.11.1.6; CAT) and superoxide dismutase (EC 1.15.1.1; SOD) activities, and ascorbic acid content. In addition, MJ treatment reduced transpiration and membrane-lipid peroxidation as expressed by malondialdehyde (MDA) content, lessened the reduction of membrane lipids, glycolipids [monogalactosyl diglyceride (MGDG), digalactosyl diglyceride (DGDG)], and phospholipids [phosphatidylcholine (PC), phosphatidylethanolamine (PE), phosphatidylglycerol (PG), and phosphatidylinositol (PI)]. In water-deficit conditions, MJ treatment also alleviated the decline in the degree of fatty acid unsaturation and the ratio of linolenic (18:3) to linoleic acid (18:2). These results indicate that MJ treatment appears to alter the metabolism of strawberry plants rendering the tissue better able to withstand water stress.

Effects of Abscisic Acid and Water Stress on the Senescence of Detached Rice Leaves

The effects of abscisic acid (ABA) and water stress on senescence and enzyme activities of oxygen scavenging enzymes of detached rice leaves were compared. Exogenously applied ABA exhibited water stress-like effects by promoting senescence, by decreasing the activities of catalase, peroxidase, ascorbate peroxidase and superoxide dismutase. It seems that the effects of water stress on senescence and enzyme activities are possibly mediated through increased content of endogenous ABA.

Evaluation of N2 fixation by stem and root nodules in sesbania rostrata during rainy and dry months

Sesbania rostrata is the most popular green manure legumes in Tamilnadu, India.S. rostrata produces both stem and root nodules. Until this time, no experiments had been performed to assess the superiority of one kind of nodule over the other. The levels of nitrogenous compounds, like nitrite, nitrate, total nitrogen, free amino acids, total soluble proteins, total allantoin, total allantoic acid, and total ureides, were determined in both the stem and root nodules during rainy and dry seasons. During the rainy season, the stem nodules possessed heavy deposition of these N-containing compounds than the root nodules. On the other hand, during the dry season, the root nodules accumulated substantial levels of these nitrogenous compounds. In a similar way, the activities of nitrogenase and nitrate reductase were higher in stem nodules during the rainy season, and the trend was reversed during the dry season, the root nodules having more nitrogenase and nitrate reductase. In consonance with the higher activities of enzymes and gorging of nitrogenous compounds, calorific values were more in the stem nodules during the rainy season. The activities of oxygen scavenging enzymes were higher in stem nodules during the dry season, possibly indicating their role in alleviation of H2O2 and O 2 - city to the nodules. As regards rhizobial population, the root nodules always contained moreRhizobia than that of the stem nodules. The efficiency of the stem and root nodules to fix more nitrogen and synthesize nitrogenous compounds is seasonal. In the dry season, the entire role of N2-fixation seemed to be borne by root noduleRhizobia only, since stem nodules during this period are hardly formed and sparsely distributed.