Protective role of exogenous phytohormones on redox status in pea seedlings under copper stress

The present work aims to provide insight on the role of phytohormone application in developing efficient practical defense strategies to improve plants tolerance under heavy metal contamination. For this purpose, pea (Pisum sativum L.) seeds were germinated in an aqueous solution of 200 mu M CuCl2 up to the 3rd day and then continued to germinate in the presence of distilled water (stress cessation) or were subjected to following combinations: Cu + 1 mu M IAA and Cu + 1 mu M GA(3) for 3 additional days. The results showed that copper excess induced oxidative stress in germinating seeds, which resulted in changes of the redox state of glutathione and cysteine, and proteomics revealed Cu-induced modifications of thiols (SH) and carbonyls (CO) (indicators of protein oxidation). However, application of IAA or GA(3) in the germination medium after 3 days of Cu exposure alleviated toxicity on seedlings, despite the persistence of Cu up to 6th day. This improving effect seems to be mediated by a cell Cu accumulation decrease and a protein reduced status recovery, since phytohormones modulate thioredoxin/ferredoxin systems in favor of protecting proteins against oxidation. In addition, an IAA and GA(3) protective effect was evidenced by a cellular homeostasis amelioration resulting from the balance conservation between the regeneration and consumption processes of glutathione and cysteine reduced forms. The exogenous effectors also induced modifications of profiles of SH and CO, suggesting changes in the regulation and expression of proteins that could be involved in defense mechanism against Cu stress

Alleviation of copper toxicity in germinating pea seeds by IAA, GA3, Ca and citric acid

The ameliorating effects of four exogenous effectors were investigated in germinating pea seeds exposed to copper excess. The results showed that the application of IAA, GA3, Ca or citric acid alleviated Cu-induced inhibition of growth and simultaneously reduced the oxidative stress injury, particularly contents of hydrogen peroxide, malondialdehyde and carbonyl groups. The improving effects can probably be mediated by the decreases in lipoperoxidation and protein oxidation as evidenced by changes in antioxidant enzyme activities. In addition, the efficiency of this recovery was compared within two types of treatments. Obtained results demonstrated that the stress abruption by the addition of effectors after three days of Cu application (treatment of type II) seems to be more effective than the simultaneous application of ‘Cu + effectors’ at the beginning of germination (treatment of type I). Data could provide some clues to physiological and biochemical mechanisms of the response of germinating seeds to the addition of chemicals under heavy metal stress

Effects of copper on reserve mobilization in embryo of Phaseolus vulgaris L.

The present research reports a biochemical and micro-submicroscopic analysis of copper effect on reserves mobilization during germination of Phaseolus vulgaris L. var. soisson nain hatif seeds. Dry embryonic cells are rich in protein bodies and little starch grains. In Cu-treated embryos copper inhibited 50% of albumin and globulin mobilization after 72 h imbibition. The severe alterations in treated embryo cells, observed by electron microscope, were probably the cause of the inability to utilize the amino acids freed by protein mobilization and so possibly the cause of the inhibition of P. vulgaris embryonic axes elongation

[Retracted] Effect of cadmium on resumption of respiration in cotyledons of germinating pea seeds

This article has been retracted: please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy). This article has been retracted at the request of the Former Editor-in-Chief and co-authors. The article includes content plagiarised from articles that have already appeared in the following journals. See: https://doi.org/10.1016/j.ecoenv.2010.05.015International audiencePea seeds (Pisum sativum L.) were germinated by soaking in H2O OR 5mM CdCl2 during a 5-day period. Enzyme activities involved in respiratory metabolism were studied in cotyledons. Mitochondrial cytochrome c oxidase and NADH- and succinate-cytochrome c reductase activities wer inhibited by cadmium treatment. The effects of Cd were performed in vivo and in vitro allowing to distinguish between the direct inhibition of the enzyme activities and the influence of the same enzymes into the cell environment. However, Cd exposure stimulated an enzyme activity of fermentation and inhibited the capacity of the enzyme inactivator (alcool dehydogenase inactivator). Moreover, the enzyme activities of NAD(P)H-recycling dehydogenases via secondary pentose phosphate pahtway, glucose-6-phosphate- and 6-phosphogluconate-dehydrogenases, were enhanced in Cd-stressed seeds. The findings will help clarify the overall mechanisms that underlie cadmium-mediated toxicity in germinating seeds

Cadmium Affects the Glutathione/Glutaredoxin System in Germinating Pea Seeds

Publication Inra prise en compte dans l'analyse bibliométrique des publications scientifiques mondiales sur les Fruits, les Légumes et la Pomme de terre. Période 2000-2012. http://prodinra.inra.fr/record/256699International audienceThe aim of this work was to investigate the effects of cadmium (Cd) on thiol and especially glutathione (GSH)-dependent reactions (glutathione content, glutaredoxin (Grx) content and activity, "glutathione" peroxidase (Gpx) activity, and glutathione reductase (GR) activity) in germinating pea seeds. Under Cd stress conditions, the overall activity as well as more specifically the expression of Grx C4 and Grx S12 increased. On the contrary, when incubated with Cd ions in vitro, the disulfide reductase activity of both isoforms was drastically inhibited. In the case of Grx C4, this correlated with the formation of protein dimers of 28 kDa as evidenced by electrophoresis analysis. Oxidative stress also affected the GSH status, since Cd treatment provoked (1) a pronounced stimulation in Gpx (a thioredoxin-dependent enzyme in plants) expression and (2) a drastic decrease in GR activity. These results are discussed in relation with the known contribution of Grx system to the thiol status during the germination of Cd-poisoned pea seeds

[Retracted] Redox regulation of the glutathione reductase/iso-glutaredoxin system in germinating pea seed exposed to cadmium

This article has been retracted: please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy). The editors would like to confirm the retraction of this paper at the request of the co-authors who had no prior knowledge on the actions of the lead author. See: https://doi.org/10.1016/j.plantsci.2010.06.015International audienceThe present work aims at understanding the regulation of the glutathione/glutathione reductase/glutaredoxin system (GSH/GR/GRX) in plant, namely the transition from heterotrophic growth to photoautotrophic metabolism in seedlings. Pea seeds were analyzed between 0 and 5 days. This study compares seedlings grown in the presence or absence of external cadmium. GSH/GR/GRX system was studied separately in cotyledons that mainly serve to reserve breakdown and in embryonic axes that prepare for cell elongation and cell division associated with radicle emergence. We made extracts of the proteins at various stages of the development, quantify their protein content and use them for activity measurements and estimation of specific protein levels. Cadmium caused a reduction of the total glutathione content. The levels of glutaredoxin C4 (GRX C4) and glutaredoxin 512 (GRX S12) showed a Cd-dependent increase, although GRX activity was depressed. Glutathione reductase activity was significantly reduced by cadmium. However, Cd treatment provoked a strong induction in protein level and activity of glutathione peroxidase (GPX). The disturbances in the resumption of redox metabolism may be a contributory cause of deleterious effect of cadmium on pea seed germination. (C) 2010 Elsevier Ireland Ltd. All rights reserved