A proposed interplay between peroxidase, amine oxidase and lipoxygenase in the wounding-induced oxidative burst in Pisum sativum seedlings

Plant surfaces form the barrier between a plant and its environment. Upon damage, the wound healing process begins immediately and is accompanied by a rapid production of extracellular reactive oxygen species (ROS), essential in deterring pathogens, signalling responses and cell wall restructuring. Although many enzymes produce extracellular ROS, it is unclear if ROS-producing enzymes act synergistically. We characterised the oxidative burst of superoxide (O-2(center dot-)) and hydrogen peroxide (H2O2) that follows wounding in pea (Pisum sativum L.) seedlings. Rates of ROS production were manipulated by exogenous application of enzyme substrates and inhibitors. The results indicate significant roles for di-amine oxidases (DAO) and peroxidases (Prx) rather than NADPH oxidase. The burst of O-2(center dot-) was strongly dependent on the presence of H2O2 produced by DAO. Potential substrates released from wounded seedlings included linoleic acid that, upon exogenous application, strongly stimulated catalase-sensitive O-2(center dot-) production. Moreover, a 65 kD plasma membrane (PM) guaiacol Prx was found in the secretome of wounded seedlings and showed dependence on linoleic acid for O-2(center dot-) production. Lipoxygenases are suggested to modulate O-2(center dot-) production by consuming polyunsaturated fatty acids in the apoplast. Overall, a O-2(center dot-)-producing mechanism involving H2O2-derived from DAO, linoleic acid and a PM-associated Prx is proposed. (C) 2014 Elsevier Ltd. All rights reserved.