Chapter 13 - Reactive Oxygen Species and Antioxidants in Response to Pathogens and Wounding

Abstract

Their sessile nature and the lack of specialized immune cells make plants vulnerable to stress, damage and injury. Unlike animals, which can migrate for food and avoid harsh weather conditions, the immobility of plants makes them unable to evade stressful conditions. Plants have thus evolved certain mechanisms for their survival which help them in surviving biotic and abiotic stresses including drought, high salinity, frost, dehydration, microbes and injury. However, in case of an injury, wound-healing cascades activate that help secure the wound and keep the pathogens at bay, thus, speeding up the healing process. Cellular metabolism in plants results in the production of oxygen species that are extremely reactive. During stress or injury, their production accelerates and the accumulation of ROS (or sometimes called ROI) is highest around the wounds. Due to high toxicity of ROS, pathogens are killed that try to access the wounds. Apart from their beneficial role, ROS in excessive quantities are equally harmful to plants as well due to the damage these can cause to biomolecules such as lipids, proteins and DNA. To keep the levels of ROS balanced, plants produce several enzymatic and nonenzymatic antioxidants or ROS scavengers that balance ROS, as the complete eradication of ROS means the loss of an important second messenger in intracellular signaling cascades. This whole intertwined web of mechanisms is quite intricate. In the following chapter, we aim to discuss in detail the role of different types of ROS in evading stress and injury, the independent roles of each antioxidant in wound healing, the genes involved in their synthesis and the pathways of wound healing.