Spatiotemporal variations in salicylic acid and hydrogen peroxide in sunflower seeds during transition from dormancy to germination.

Phytohormones and reactive oxygen species mediate processes such as germination and dormancy. The elucidation of the physiological and biochemical events implicated in the transition from dormancy to germination in different plant species such as sunflower becomes a topic of interest. In this study, we investigated the spatiotemporal variation of salicylic acid (SA), hydrogen peroxide (H2 O2 ) and the activity of two antioxidant enzymes (catalase, CAT - EC 1.11.1.6 and ascorbate peroxidase - EC 1.11.1.11) in embryonic axis and cotyledons of dry and imbibed seeds of dormant (B123) and non-dormant (B91) sunflower lines. The results showed that embryonic axis had higher level of SA and H2 O2 than cotyledons in both lines. In dry seeds, B123 embryo (embryonic axis + cotyledons) showed a higher SA content than B91. After dry storage at room temperature, SA decreased in B123 embryos to a value close to that registered in B91 embryos. B123 embryonic axis of dry seeds presented higher H2 O2 levels than B91. Dry storage led to an increase of H2 O2 levels and a decrease of CAT activity in B123 embryonic axis. During imbibition, B123 seeds stored for 33 days displayed an increase in SA level in the embryonic axis (3 h of imbibition) and this lower level correlated with a decrease in H2 O2 (6 h of imbibition). Thus, the embryo-imposed dormancy in B123 dry seeds was associated with high levels of SA and low H2 O2 , whereas the dormancy release was linked with SA decrease and increase of H2 O2 as a consequence of lower CAT activity.

Cadmium induces two waves of reactive oxygen species in Glycine max (L.) roots.

Cadmium (Cd) is a non-essential heavy metal that may be toxic or even lethal to plants as it can be easily taken up by the roots and loaded into the xylem to the leaves. Using soybean roots (Glycine max L.) DM 4800, we have analysed various parameters related to reactive oxygen metabolism and nitric oxide (NO) during a 6 day Cd exposure. A rise in H(2)O(2) and NO, and to a lesser extent O(2)(·-) content was observed after 6 h exposure with a concomitant increase in lipid peroxidation and carbonyl group content. Both oxidative markers were significantly reduced after 24 h. A second, higher wave of O(2)(·-) production was also observed after 72 h of exposure followed by a reduction until the end of the treatment. NOX and glicolate oxidase activity might be involved in the initial Cd-induced reactive oxygen species (ROS) production and it appears that other sources may also participate. The analysis of antioxidative enzymes showed an increase in glutathione-S-transferase activity and in transcript levels and activity of enzymes involved in the ascorbate-glutathione cycle and the NADPH-generating enzymes. These results suggest that soybean is able to respond rapidly to oxidative stress imposed by Cd by improving the availability of NADPH necessary for the ascorbate-glutathione cycle.

Effect of Arbuscular Mycorrhizal Colonization on Cadmium-Mediated Oxidative Stress in Glycine max (L.) Merr.

Cadmium is a heavy metal (HM) that inhibits plant growth and leads to death, causing great losses in yields, especially in Cd hyperaccumulator crops such as Glycine max (L.) Merr. (soybean), a worldwide economically important legume. Furthermore, Cd incorporation into the food chain is a health hazard. Oxidative stress (OS) is a plant response to abiotic and biotic stresses with an intracellular burst of reactive oxygen species (ROS) that causes damage to lipids, proteins, and DNA. The arbuscular mycorrhizal fungal (AMF) association is a plant strategy to cope with HM and to alleviate OS. Our aim was to evaluate the mitigation effects of mycorrhization with AMF Rhizophagus intraradices on soybean growth, nutrients, Cd accumulation, lipid peroxidation, and the activity of different antioxidant agents under Cd (0.7-1.2 mg kg-1 bioavailable Cd) induced OS. Our results suggest that glutathione may act as a signal molecule in a defense response to Cd-induced OS, and mycorrhization may avoid Cd-induced growth inhibition and reduce Cd accumulation in roots. It is discussed that R. intraradices mycorrhization would act as a signal, promoting the generation of a soybean cross tolerance response to Cd pollution, therefore evidencing the potential of this AMF association for bioremediation and encouragement of crop development, particularly because it is an interaction between a worldwide cultivated Cd hyperaccumulator plant and an AMF-HM-accumulator commonly present in soils.

Effect of the herbicide glyphosate on liver lipoperoxidation in pregnant rats and their fetuses.

Glyphosate is a post-emergence herbicide that acts on the synthesis of amino acids and other endogenous metabolites in plants. It is commonly used in agriculture, forestry, and nurseries for the control or destruction of herbaceous plants. Metabolic processes during development and pregnancy could be sensitive to changes induced by glyphosate such as lipid peroxidation. The present study has investigated the effects that 1% glyphosate oral exposure has on lipoperoxidation and antioxidant enzyme systems in the maternal serum and liver of pregnant rats and their term fetuses at 21 days of gestation. The results suggest that excessive lipid peroxidation induced with glyphosate ingestion leads to an overload of maternal and fetal antioxidant defense systems.

Morphological changes and oxidative stress in rat prostate exposed to a non-carcinogenic dose of cadmium.

Cadmium chloride is an environmental toxicant implicated in human prostate carcinogenesis. The mechanism of its toxicity is far from fully understood. This study evaluates the effect of exposure to an oral non-carcinogenic dose of cadmium (15 ppm in drinking water for three months) on different parameters of the ventral prostatic lobe of normal and exposed rats. We analyzed the histology by optic light microscopy, activities of antioxidant enzymes (CAT, SOD, GPx and G-6-PDH), expression of iNOS and COX-2 by Western blot, expression of MT-I, MT-II, IGF-I, IGF-BP5 and rtert by RT-PCR. Histological changes were found: the height of the cells decreased, acinar lumen were enlarged and they lost the typical invaginations. Lipoperoxidation was increased in the Cd group and the antioxidant enzymes changed their activities: SOD increased, CAT and G-6-PDH decreased and GPx did not show variations. iNOS and COX-2 did not change their expressions. MT-I and IGF-BP5 mRNA increased while MT-II, IGF-I and rtert did not show variations. Cd exposure induces important morphological changes in the prostate, which could be a consequence of lipoperoxidation and oxidative stress, which are not related to iNOS and COX-2. The histology suggests an involution state of the gland, confirmed by the expression of IGF-I, IGF-BP5 and rtert.

Alterations in the lipid metabolism of rat aorta: effects of vitamin a deficiency.

Antioxidants are known to reduce cardiovascular disease by reducing the concentration of free radicals in the vessel wall and by preventing the oxidative modification of low-density lipoproteins. The prooxidative effect of a vitamin-A-deficient diet on the aorta has previously been demonstrated by us. In this study, the lipid metabolism in the aorta of rats fed on a vitamin-A-deficient diet was evaluated. Vitamin A deficiency induced a hypolipidemic effect (lower serum triglyceride and cholesterol levels) and a decreased serum paraoxonase 1/arylesterase activity. The concentrations of triglycerides, total cholesterol, free and esterified cholesterol, and phospholipids were increased in the aorta of vitamin-A-deficient rats. The phospholipid compositions showed an increase in phosphatidylcholine (PC), phosphatidylinositol plus phosphatidylserine and phosphatidylethanolamine, a decrease in sphingomyelin, and no change in phosphatidylglycerol. In the aorta, the increase in triglycerides was associated with an increased fatty acid synthesis and mRNA expression of diacylglycerol acyltransferase 1. The increased PC content was attributed to an increased synthesis, as measured by [methyl-(14)C]choline incorporation into PC and high CTP:phosphocholine cytidylyltransferase-alpha mRNA expression. The cholesterol synthesis, evaluated by [1-(14)C]acetate incorporated into cholesterol and mRNA expression of 3-hydroxy-3-methylglutaryl coenzyme A reductase, did not change. The lipoprotein lipase and lectin-like oxidized low-density lipoprotein receptor 1 mRNA expression levels increased in the aorta of vitamin-A-deficient animals. The incorporation of vitamin A into the diet of vitamin-A-deficient rats reverted all the changes observed. These results indicate that a vitamin-A-deficient diet,in addition to having a prooxidative effect, alters the aorta lipid metabolism.

Chronic zinc deficiency induces an antioxidant adaptive response in rat lung.

Few studies are available about the role of dietary zinc (Zn) in respiratory diseases. Adult male rats were divided into 2 groups and fed respectively a moderate Zn-deficient diet and a Zn-adequate control diet. In lung tissue at 2 months, thiobarbituric acid-reactive species (TBARS), total glutathione, glutathione disulfide, protein carbonyls, metallothionein, and the activities of glutathione peroxidase (GPx), catalase, CuZn-superoxide dismutase (CuZnSOD) and glucose-6-phosphate dehydrogenase (G-6-PDH) were increased, but protein thiols decreased. In lung tissue at 4 months, TBARS, metallothionein, and the activities of CuZnSOD, Mn-superoxide dismutase (MnSOD) increased. The activities GPx, catalase, G-6-PDH were lower than control group. The changes were accompanied by histological alterations in Zn-deficient lung. The results provide evidence of the pro-oxidative effects of Zn-deficiency in lung, and suggest that the time of treatment play a key role in determining lung susceptibility to oxidative stress.