REGULAR ARTICLES Cell Research (2004); 14(3): 234-240 Induction of defence gene expression by oligogalacturonic acid requires increases in both cytosolic calcium and hydrogen peroxide in Arabidopsis thaliana Xiang Yang HU 1, Steven J NEILL2, Wei Ming CAI1, Zhang Cheng TANG1 1Institute of Plant
Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese
Academy of Sciences, Shanghai 200032, China. Received, Jun 25, 2003 Revised, Apr 14, 2004 Accepted, Apr 16, 2004
Responses to oligogalacturonic acid (OGA) were determined in transgenic Arabidopsis thaliana seedlings expressing the calcium reporter protein aequorin. OGA stimulated a rapid, substantial and transient increase in the concentration of cytosolic calcium ([Ca2+]cyt) that peaked after ca. 15 s. This increase was dose-dependent, saturating at ca. 50 µg Gal equiv/ml of OGA. OGA also stimulated a rapid generation of H2O2. A small, rapid increase in H2O2 content was followed by a much larger oxidative burst, with H2O2 content peaking after ca. 60 min and declining thereafter. Induction of the oxidative burst by OGA was also dose-dependent, with a maximum response again being achieved at ca. 50 µg Gal equiv/mL. Inhibitors of calcium fluxes inhibited both increases in [Ca2+]cyt and [H2O2], whereas inhibitors of NADPH oxidase blocked only the oxidative burst. OGA increased strongly the expression of the defence-related genes CHS, GST, PAL and PR-1. This induction was suppressed by inhibitors of calcium flux or NADPH oxidase, indicating that increases in both cytosolic calcium and H2O2 are required for OGA-induced gene expression. Keywords: Arabidopsis thaliana, cytosolic calcium, defence gene expression, hydrogen peroxide, OGA.
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