Occurrence, Chemical Structure, and Biosynthesis of Hydrogen Peroxide in Plants

Abstract

Hydrogen peroxide (H₂O₂) is a molecule prevalent in plant cells, recognized for its diverse roles in cellular functions and stress responses. H₂O₂ functions effectively both as a signaling molecule and as a mediator of oxidative stress, making it crucial for various physiological processes in plants. The structure of H₂O₂, a simple molecule with significant reactivity due to its polar nature and bent geometry, facilitates its role in various biological processes. It is generated as a by-product of various metabolic processes across different cellular compartments including chloroplasts, mitochondria, peroxisomes, apoplast, cytoplasm, and nuclei. Biosynthesis of H₂O₂ involves light, organic matter, and enzymes such as flavin-containing oxidases. In peroxisomes, oxidases generate H₂O₂ during photorespiration and fatty acid oxidation. The electron transport chains in chloroplasts and mitochondria also contribute to H₂O₂ production. Nicotinamide adenine dinucleotide phosphate (NADPH) oxidase (NOX) and type III peroxidases in the plasma membrane and apoplast produce H₂O₂ in response to stimuli, playing roles in signaling and defense. Other enzymes like copper amine oxidases and polyamine oxidases also contribute to H₂O₂ production. The endoplasmic reticulum generates H₂O₂ during protein folding via disulfide bond formation. Transport of H₂O₂ across cellular compartments is facilitated by aquaporin-type channel proteins. This complex interplay of production and scavenging mechanisms underscores the vital roles of H₂O₂ in plant growth, defense, and signaling. Understanding the nature of H₂O₂ and its biosynthesis in plants is essential for advancing plant science and has practical applications in agriculture and biotechnology. Enhancing plant resilience to environmental stresses and improving growth and productivity can be achieved by manipulating H₂O₂ signaling pathways. This chapter provides an in-depth exploration of H₂O₂ structure, localization, biosynthesis mechanisms, and functional significance in plant systems.