Oxidative Stress in Plants

Environmental stresses negatively affect plant growth, development and crop productivity [...].

In young leaves, photochemical and glutathione-S-transferase activities increased. However, while the ageing process advanced, the non-enzymatic antioxidant systems reduced and reached the lowest levels in senescent leaves, while poly (ADP-ribose) polymerase activity increased. In the same way, Hasanuzzaman et al. [5] discussed in an extensive review, the available and up-to-date knowledge on the Ascorbate-Glutathione pathway concerning the oxidative stress tolerance, as well as plant defence mechanisms. Furthermore, the review by Laxa et al. [6] provided up-to-date information about the response and function of ROS and RNS, mainly with regard to superoxide radicals, hydrogen peroxide and nitric oxide under drought stress conditions, and their scavenging by the antioxidant defence enzymes in several plant species. To better understand the interaction between chitosan and Vitis vinifera L. plants, the original article by Singh et al. [7] analysed the antioxidant potential, the total phenolic content and the expression of ROS detoxification genes in two red grapevine varieties treated by chitosan. They concluded that chitosan induced the phenolic compounds, as well as acted as the organiser for the transfer of polyphenols from the Vitis vinifera leaves to the berries.
Another interesting feature of this special issue focuses on investigating the other H 2 O 2 targets involved in programmed cell death. Dr. Mano's group [8] studied the mechanism that increased the reactive carbonyl species in the H 2 O 2 -produced programmed cell death in tobacco Bright Yellow-2 cells. They suggested that H 2 O 2 initially inactivates a carbonyl reductase(s), which increases the reactive carbonyl species content, leading to the activation of the caspase-3-like protease of the 20S proteasome. The authors proposed that carbonyl reductase acted as a ROS sensor for inducing programmed cell death.
In plant cells, the ROS metabolism has been widely studied in different compartments, including mitochondria, cytosol, chloroplast, cell wall, plasma membrane, apoplast, glyoxysomes and peroxisomes [9]. The review by Dr. Petřivalský's group [10] provided the present knowledge about the compartment-specific pathways of reactive oxygen species generation and decomposition in plant cells, and the mechanisms that controlling their homeostasis in cell compartments. Likewise, with a particular example at the chloroplastic level, in an in-depth review Miyake [11] summarised the current research concerning the molecular mechanisms of ROS formation and suppression in photosystem I. He established a novel molecular mechanism for the oxidation of the P700 oxidation system in photosystem I and the elimination of ROS formation from the strong relationship between the light and dark reactions of photosynthesis. Furthermore, in an original article, Lewandowska et al. [12] investigated the effect of H 2 O 2 on the structure and function of Arabidopsis chloroplastic DJ-1B. They found that AtDJ-1B has double functions, namely holdase and glyoxalase activity, which responded differently to H 2 O 2 . Glyoxalase activity was reduced by H 2 O 2 , however the holdase chaperone function did not change. They also analysed the phenotype of T-DNA lines that lacked the protein, and showed that AtDJ-1B was not necessary for plant growth under stress stimuli.
In summary, to better understand the nitro-oxidative stress networks in higher plants (Figure 1), the subjects addressed in this special issue provide an update and new knowledge about ROS and RNS metabolisms in plant responses to adverse environmental stimuli and the modulation of antioxidant systems to control ROS production and accumulation.

Conflicts of Interest:
The authors declare no conflict of interest.