The activities of antioxidant enzymes in response to oxidative stresses and hormones in paraquat-tolerant Rehmannia glutinosa plants

The bZIP transcription factor GmbZIP15 facilitates resistance against Sclerotinia sclerotiorum and Phytophthora sojae infection in soybean

Soybean, one of the most valuable oilseed crops, is under constant pressure from pathogens. bZIP transcription factors (TFs) composing one of the largest TF families in plants have diverse functions. Biochemical and physiological analyses were performed to characterize the regulatory roles of soybean bZIP TF GmbZIP15 in response to pathogens. We found that transgenic soybean plants overexpressing GmbZIP15 has increased resistance against Sclerotinia sclerotiorum and Phytophthora sojae. Besides, GmbZIP15 regulates pathogen response by modulating the antioxidant defense system and phytohormone signaling. In addition, we performed chromatin immunoprecipitation sequencing to identify the downstream genes of GmbZIP15 in response to S. sclerotiorum and found that GmbZIP15 can activate or repress the expression of defense-related genes through direct promoter binding. Taken together, these results indicate that GmbZIP15 plays a positive role in pathogen resistance in soybean, and this activity may be dependent on phytohormone signaling.

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GmbZIP15 improves resistance against pathogen

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GmbZIP15 modulates the antioxidant defense system

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GmbZIP15 regulates phytohormone signaling

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GmbZIP15 can direct bind to G-box

Willow seedlings from photooxidized seeds accelerate cotyledon death and anticipate first leaf emergence: a histological and biochemical study following germination

In willow seeds, photooxidative damage is mainly restricted to the outer cotyledonary tissues, significantly reducing normal germination. Here we analyzed the damage generated in cotyledonary tissues and investigated whether the increase in reactive oxygen species (ROS) generation in seedlings from photooxidized seeds can affect the morphogenetic capacity of the shoot apical meristem. Seeds were photooxidized under different light intensities and the evolution of the damage during seedling growth was studied by light and transmission electron microscopies. The level of lipid peroxidation and changes in antioxidant capacity were measured following the time course of superoxide dismutase, catalase, ascorbate peroxidase and guaiacol peroxidase enzyme activities, and the effect of photooxidative stress on the genesis of new leaf primordia and lateral roots was examined. Early and active endocytosis and autophagy, changes in chloroplast morphology, as well as the accumulation and diffusion of ROS all play important roles in the early cell death observed in cotyledonary tissues. Following germination, seedlings from photooxidized seeds anticipated the emergence of first leaves, which complemented the altered functionality of the damaged cotyledons.

The potential of synthetic thiourea compound to reduce the cytotoxic and genotoxic effects of paraquat in Hordeum vulgare and cultured human lymphocytes

This work evaluated the ability of one synthetic compound 1-(4-fluorophenylthiocarbamoyl)-4-methyl-piperazine (FTMP), thiourea derivative to reduce cytotoxic and genotoxic effects of free radical inducer paraquat (PQ) in two different test systems Hordeum vulgare and human lymphocytes in vitro. The mitotic index was used as a marker for cytotoxicity. To indicate genotoxicity, chromosome aberrations test and micronucleus induction test were used. FTMP manifested a weak genotoxic effect in both test systems. Clear evidence was obtained that conditioning treatment with FTMP (10(-6) , 5 × 10(-6) , and 10(-5) mol/l) could decrease chromosome aberrations and micronuclei induced by PQ in both test systems. "Aberration hot spots" in heterochromatin containing segments were reduced. The present data show that the thiourea synthetic compound FTMP provides genome protection against the harmful action of oxidative stress inductor PQ. Human lymphocytes were found to be more sensitive to the cytotoxic and clastogenic effects of FTMP conditioning treatment than Hordeum vulgare. Revealing the protective action of newly synthesized compounds could contribute to the improvement of our present knowledge of the mechanisms of mutagenesis and antimutagenesis.

Role of chloroplastidial proteases in leaf senescence

In this report the effect of hydrogen peroxide (H2O2) on peroxidase (POD) activity during leaf senescence was studied with and without phenylmethylsulfonyl fluoride (PMSF) pre-treatment in detached neem (Azadirachta indica A. juss) leaf chloroplasts. Increased POD activity was detected in natural and H2O2-promoted senescent leaf chloroplasts compared to untreated control mature green leaf chloroplasts. However, under H2O2 POD activity markedly increased at 1 day, and then significantly decreased until 4 days. In the presence of H2O2, PMSF, the induction of POD activity was alleviated at 1 day, whereas reduced after 4 days. In contrast, in the presence of H2O2, cycloheximide (CX), the induction of POD activity was reduced at 1 day, whereas alleviated after 4 days. The was a partial reduction in H2O2-induced POD activity with PMSF and CX, indicating the presence of pre-existing inactive PODs in chloroplasts. We also propose a new role for chloroplastidial proteases as activators of pre-existing inactive PODs during leaf senescence.

Attenuation of senescence-induced oxidative exacerbations in aged rat brain by (-)-epigallocatechin-3-gallate

Aging is a complex biological phenomenon which involves free radicals and oxidative stress. Brain is more susceptible and vulnerable to oxidative damage due to its high-polyunsaturated fatty acid content and high rate of aerobic metabolism. Since the antioxidant defense system is diminished during aging, antioxidant supplementation might be a protective strategy against age-associated oxidative damage. The present study evaluates the antioxidant potential of (-)-epigallocatechin-3-gallate (EGCG), a major polyphenol present in green tea against age-associated oxidative damage in rat brain. Male albino rats of Wistar strain were used in the study. Group I (young) and Group II (aged) rats received saline alone orally for 30 days. Group III (young) and Group IV (aged) rats received EGCG (2mg/kg body weight/day) orally for 30 days. Antioxidant status and oxidative damage were assessed. EGCG brought about an augmentation in the activities of enzymic antioxidants like superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase, glucose-6-phosphate dehydrogenase and improved the non-enzymic antioxidants like tocopherol, ascorbic acid and glutathione. EGCG ameliorated the malondialdehyde and protein carbonyl levels. Thus, EGCG has emerged out as a good antioxidant neutraceutical and a neuroprotective agent in alleviating the age-associated oxidative damage in aged rat brain.

Enhanced Antioxidant Enzymes Are Associated with Reduced Hydrogen Peroxide in Barley Roots under Saline Stress

Antioxidant enzymes are related to the resistance to various abiotic stresses including salinity. Barley is relatively tolerant to saline stress among crop plants, but little information is available on barley antioxidant enzymes under salinity stress. We investigated temporal and spatial responses of activities and isoform profiles of superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), non-specific peroxidase (POX), and glutathione reductase (GR) to saline stress in barley seedlings treated with 200 mM NaCl for 0, 1, 2, 5 days, respectively. In the control plant, hydrogen peroxide content was about 2-fold higher in the root than in the shoot. Under saline stress, hydrogen peroxide content was decreased drastically by 70% at 2 d after NaCl treatment (DAT) in the root. In the leaf, however, the content was remained unchanged by 2 DAT and increased about 14 % at 5 DAT. In general, the activities of antioxidant enzymes were increased in the root and shoot under saline stress. But the increase was more significant and consistent in the root. The activities of SOD, CAT, APX, POX, and GR were increased significantly in the root within 1 DAT, and various elevated levels were maintained by 5 DAT. Among the antioxidant enzymes, CAT activity was increased the most drastically. The significant increase in the activities of SOD, CAT, APX, POX, and GR in the NaCl-stressed barley root was highly correlated with the increased expression of the constitutive isoforms as well as the induced ones. The hydrogen peroxide content in the root.