Abstract
Reactive oxygen species serve an important role in the plant defense system. Plants have a biphasic response to pathogens and wounding. The first response involves expression of the early genes involved in the signaling pathway (such as, polygalacturonase, prosystemin, lipoxygenase, and allene oxide synthase); the second "late" response involves the up-regulation of the defense genes [such as, proteinase inhibitors I and II (InhI and InhII), cathepsin D inhibitor, carboxypeptidase inhibitor, and polyphenol oxidase]. Orozco-Cárdenas et al. show that inhibition of the reduced form of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase, which produces the reactive oxygen species burst, blocks the expression of the late genes and the accumulation of InhI and InhII. InhI and InhII accumulated in leaves, and the expression of defense genes was increased in leaves treated with glucose and glucose oxidase to artificially increase peroxide levels. Cytochemical localization of peroxide indicated that peroxide is initially produced by cells in the vascular system and then may diffuse to the mesophyll cells to regulate the expression of the late genes. M. L. Orozco-Cárdenas, J. Narváez-Vásquez, C. A. Ryan, Hydrogen peroxide acts as a second messenger for the induction of defense genes in tomato plants in response to wounding, systemin, and methyl jasmonate. Plant Cell 13 : 179-191 (2001). [Abstract] [Full Text]
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