Cellular nitro-oxidative burden and survival through regulated cell death in the plants

Throughout the life of a plant, generations of different forms of reactive oxygen (ROS) and nitrogen species (RNS) are derived as a by-product of metabolic events. The quantum of ROS and RNS becomes higher once a plant encounters a perturbed situation either through biotic or abiotic factor. As each of reactive species is harmful to the cells beyond certain optimal level, it requires a mechanism to detoxify RONS induced cellular toxicity. For the purpose cell has instituted highly organized multi-layered defense mechanisms. In the first layer of defense, cell produces different antioxidant enzymes and non-enzyme molecules. Once generated, ROS and RNS become beyond the detoxification capacity of cellular antioxidant pool, another strategy comes into the operation wherein a few targeted cells undergo self-autolysis progression known as programmed cell death (PCD). The process of PCD has been partially dissected in plants emphasizing either under amplified ROS or RNS condition. However, there are evidences for reaction between species of ROS and RNS. It is unequivocally evident that superoxide has tendency to react with nitric oxide giving rise to a very potential oxidant called peroxynitrite that has ability to nitrosylate several biomolecules thus, altering cellular fate. This suggests that cellular damage caused by reactive species of nitrogen and oxygen is not only an outcome of accumulation of individual species of ROS and RNS, but a combinatorial product of ROS and RNS may have a key role to play. In this review, we intend to advocate role of cellular nitro-oxidative condition in PCD in plants.