Ascorbate-glutathione cycle: Enzymatic and non-enzymatic integrated mechanisms and its biomolecular regulation

Abstract

In plant physiology, low level of oxidative stress produces a favourable effect on the metabolism of a plant. However, when antioxydant defenses are over-passed by the action of oxidative compounds it will produce metabolic alteration that would end in cell death. The increase of oxidative stress is conditioned by different types of abiotic (salinity, drought, heavy metal) and biotic (fungus and insects) stresses. The main objective of this chapter will be to evaluate the role of ascorbate-glutathione cycle in the defense mechanisms and antioxidant capacity in plants under different stress conditions, integrating non enzymatic (ascorbate and glutathione) and enzymatic pathways and its biomolecular regulation. This chapter will describe the integration of both non-enzymatic and enzymatic mechanisms specially those concerning with the regeneration of active compounds. Enzymatic pathway preserves the active form of ascorbate and glutathione. Furthemore, we will also describe the regulation of ascorbate-glutation cycle developed by alterated redox status, which can be produced produced by abiotic and biotic stress. In addition, in the discussion we will emphasize the agronomic and genomic approaches on how to improve the plant tolerance against the biotic and abiotic stresses, so that a higher antioxidant level can be obtained, which will benefit the healthy quality of vegetable foods.