Antioxidant Systems are Regulated by Nitric Oxide-Mediated Post-translational Modifications (NO-PTMs)

Abstract

Nitric oxide (NO) is a biological messenger that orchestrates a plethora of plant functions, mainly through post-translational modifications (PTMs) such as S-nitrosylation or tyrosine nitration. In plants, hundreds of proteins have been identified as potential targets of these NO-PTMs under physiological and stress conditions indicating the relevance of NO in plant-signaling mechanisms. Among these NO protein targets, there are different antioxidant enzymes involved in the control of reactive oxygen species (ROS), such as H2O2, which is also a signal molecule. This highlights the close relationship between ROS/NO signaling pathways. The major plant antioxidant enzymes, including catalase, superoxide dismutases (SODs) peroxiredoxins (Prx) and all the enzymatic components of the ascorbate-glutathione (Asa-GSH) cycle, have been shown to be modulated to different degrees by NO-PTMs. This mini-review will update the recent knowledge concerning the interaction of NO with these antioxidant enzymes, with a special focus on the components of the Asa-GSH cycle and their physiological relevance.

Keywords: S-nitrosylation; ascorbate-glutathione cycle; catalase; nitric oxide; peroxiredoxin; superoxide dismutase; tyrosine nitration.

FIGURE 1

Regulation of ascorbate glutathione cycle by NO-PTMs. APX activity is inhibited by tyrosine nitration and enhanced by S-nitrosylation, whereas MDAR is inhibited by both NO-PTMs. DHAR is inhibited by S-nitrosylation and GR is not affected by these PTMs. Color of arrows shows the effect of tyrosine nitration and S-nitrosylation on enzymatic activities; red: inhibition, green: enhancement, and blue: no effect. APX, ascorbate peroxidase; MDAR, monodehydroascrobate reductase; DHAR, dehydroascorbate reductase; GR, glutathione reductase.