GABA and Oxidative Stress and the Regulation of Antioxidants

This chapter offers an overview of reactive oxygen species (ROS) and the antioxidant defense system in plants. It commences by introducing ROS and their dual role as necessary byproducts of oxygen metabolism and potentially harmful entities. Different types of ROS, such as superoxide anion, hydrogen peroxide, hydroxyl radical, and singlet oxygen, are detailed. The text then delves into the generation of ROS in plants under normal circumstances and diverse stressors, emphasizing the compartmentalization of ROS within various cellular organelles as crucial for plant stress adaptation. The temporal and spatial control of ROS production and scavenging activities are central to plant responses to stress. Subsequently, the antioxidant defense system in plants is scrutinized, encompassing both nonenzymatic and enzymatic antioxidants. Nonenzymatic antioxidants include ascorbic acid (ASH) (vitamin C), glutathione (GHS), proline, tocopherols (vitamin E), carotenoids, and flavonoids. Enzymatic antioxidants consist of superoxide dismutase, catalase, peroxidases, GHS reductase, monodehydroascorbate reductase (MDHAR), dehydroascorbate reductase (DHAR), GHS peroxidase, and GHS S-transferases (GST). In addition, the text explores the impact of gamma-aminobutyric acid (GABA) on regulating the antioxidant system and oxidative stress in plants. GABA influences the synthesis of phenolic compounds, carotenoids, tocopherols, and ASH, thereby affecting the overall antioxidant capacity of plants. At last, the text elucidates the mechanisms through which GABA controls ROS, including scavenging ROS molecules, enhancing antioxidant enzyme activity, modulating gene expression related to ROS metabolism, and interacting with other signaling molecules involved in ROS regulation.