Update on Oxidative Stress and Photosynthesis Understanding Oxidative Stress and Antioxidant Functions to Enhance Photosynthesis

Photosynthesis is a well-established source of reactive oxygen species (ROS) in plants. The photosynthetic electron transport chain (PET) operates in an aerobic environment; thus, regulatory systems are required to minimize ROS production. Moreover, an efficient antioxidant network is also essential in order to process ROS effectively and to maintain intracellular ROS pools at low levels. The importance of the antioxidant network in maintaining high rates of photosynthesis has been demonstrated in many studies using molecular genetics approaches to either disable antioxidant enzymes or boost their activities or alter the abundance of low-Mr molecular antioxidants such as ascorbate (AsA) and reduced glutathione (GSH). However, such studies have often failed to take into account the photosynthetic production of reductants and oxidants within the context of cellular redox homeostasis and redox signaling. Our understanding of the interactions of redox signaling pathways with photosynthesis has greatly increased in recent years, and this provides new opportunities for enhancing photosynthesis particularly under conditions that favor cellular oxidation. Here, we consider current concepts of oxidative stress and oxidative signaling in relation to photosynthesis, andwe discuss whether ROSscavenging systems have evolved to be “leaky” in order that ROS can function as a useful signaling system.