Role of ascorbate peroxidase and glutathione reductase in ascorbate-glutathione cycle and stress tolerance in plants

Abstract

Ascorbate-glutathione (AsA-GSH) cycle is an important component of the scavenging system for reactive oxygen compounds in plants. The member of this pathway involves the antioxidants: AsA, GSH and the antioxidatnt enzymes such as ascorbate peroxidase (APX), monodehydroascorbate reductase (MDAsAR), dehydroascorbate reductase (DAsAR) and glutathione reductase (GR). APX and GR are the key enzymes of the AsA-GSH cycle. APX utilizes AsA as the electron donor reducing H2O2 to water, and prevents the accumulation of a toxic level of H2O2 in photosynthetic organisms under stress conditions. GR converts oxidized glutathione (GSSG) to GSH using NAD(P)H as an electron donor. And thus a highly ratio of GSH/GSSG and AsA/DAsA is maintained at the intracellular level by this reaction during oxidative stress. In general, APX and GR activity have been shown to increase in various plant species under different stress conditions. Transgenic plants showed that APX and GR play an important role in providing resistance to oxidative stress caused by diferent stressors such as paraquat, methyl viologen, ozone, drought, heavy metals, high light, salinity, and chilling. In this review, recent progress in research on APX, GR and stress tolerance will be discussed.