Hydrogen Peroxide Stimulates Salicylic Acid Biosynthesis in Tobacco

Abstract

Hydrogen peroxide induced the accumulation of free benzoic acid (BA) and salicylic acid (SA) in tobacco (Nicotiana fabacum L.cv Xanthi-nc) leaves. Six hours after infiltration with 300 mM H202, the levels of BA and SA in leaves increased 5-fold over the levels detected in control leaves. The accumulation of BA and SA was preceded by the rapid activation of benzoic acid 2-hydroxylase (BAZH) in the H,O,-infiltrated tissues. This enzyme catalyzes the formation of SA from BA. Enzyme activation could be reproduced in vitro by addition of H,O, or cumene hydroperoxide to the assay mixture. H202 was most effective in vitro when applied at 6 mM. In vitro activation of BAZH by peroxides was inhibited by the catalase inhibitor 3-amino-l,2,4-triazole. We suggest that H,O, activates SA biosynthesis via two mechanisms. First, H,02 stimulates BAZH activity directly or via the formation of its substrate, molecular oxygen, in a catalase-mediated reaction. Second, higher BA levels induce the accumulation of BAZH protein in the cells and provide more substrate for this enzyme.

Microbial Siderophores Exert a Subtle Role in Arabidopsis during Infection by Manipulating the Immune Response and the Iron Status

“…8). This oxidative stress could activate the SA pathway and AtFER1 gene expression, as these two responses are known to be inducible by reactive oxygen species (Leon et al 1995;Gaymard et al, 1996;Petit et al, 2001). Two observations are in agreement with this hypothesis.…”

The hypersensitive response and the induction of cell death in plants

“…This amplification may reflect a runaway cycle where SA and ROIs are involved. Indeed H 2 O 2 can induce SA synthesis (Leo  n et al, 1995;Neuenschwander et al, 1995) which, at very high concentrations, can inhibit catalase and other scavenging enzymes (Chen et al, 1993), potentiating further accumulation of H 2 O 2 (Shirasu et al, 1997).…”

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“…Another model proposes that it is the generation of molecular oxygen from catalase dismutation of H,O, produced during the initial oxidative burst of pathogen response that fuels the production of SA from benzoic acid, triggering SAR (Leon et al, 1995). Disease resistance can be conferred by elevated levels of H202 and this resistance is counteracted by exogenous catalase activity (Wu et al, 1995).…”