Homeostasis of the antioxidant metabolism: a new role for nickel?

Abstract

Ni micronutrient has its essentiality justified in plants by its urease enzyme activator role and thus enabling the recycling of nitrogen from the degradation of toxic levels of urea. In addition to the metabolic and biochemical roles that Ni can exert through urease, recent studies show that this metal can activate a glyoxalase I isoform important in the degradation of MG, a potent cytotoxic compound. It has been shown that glyoxalases (I and II) are essential not only in plants MG degradation, produced in normal metabolism, but also when there is an increase in its concentration during situations of salt, oxidative and osmotic stress. In addition, these enzymes consume and regenerate reduced glutathione in the MG degradation process, which can be an important feature in the standing up to oxidative stress. The project aims to verify if the essentiality of Ni, through the activation of glyoxalase I, extends to the antioxidative mechanisms of plants. To this end, rice (Oryza sativa) seedlings will be exposed to salt and oxidative stress (by addition of NaCl and H2O2) in the presence or absence of Ni, furthermore, activity and gene expression determinations of enzymes and levels of the compounds of the glioxalases system and antioxidant system will be made. A second part of the study pretends to investigate the role of Ni in reduced glutathione balance, exclusively in the glyoxalases system. To this end, inhibitors of glutathione syntesis and glutathione reductase will be used.