ROS Signaling: Relevance with Site of Production and Metabolism of ROS

Abstract

One of the inevitable consequences of aerobic metabolism is the production of ROS in biological organisms including plants. Accordingly, plants have evolved antioxidant system (antioxidant enzymes and antioxidant molecules) to protect the cell components from oxidative threat. Usually cells accumulate ROS to a fatal level due to imbalance between generation and scavenging under stress or pathogenic attack. Recent observations led to an idea of involvement of ROS in signaling for plant growth and development. Although common sites of ROS generation are chloroplasts, mitochondria, and other organelles, ROS produced by plasma membrane localized NADPH oxidase (Rboh) in extracellular space has been implicated to participate in signaling process. Calcium, being most important signal molecule, has a cross talk with Rboh through a positive feedback loop that forms the basis of ROS-driven signaling network. Such signaling most often works behind plant growth and developmental processes like seed germination, root growth, stomatal regulation, and stress tolerance. Recent researches establish a ROS wave with an integration of Ca²⁺ signal that may operate for long distance signaling in plants. This may help to explain the event of systemic signaling in case of systemic acquired resistance (SAR) during pathogen attack and systemic acquired acclimation (SAA), which is achieved by gradual exposure to stress. Establishment of the possibilities of intracellular ROS signaling through vesicular trafficking and involvement in regulation of nuclear activities are on the way.