Volume 14 Issue 3, June 2004: 234-240
ORIGINAL ARTICLES
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.
2Centre for Research in Plant Science, University of the West of England, Bristol, Coldharbour Lane, Bristol BS16 1QY, UK
Correspondence: Wei Ming CAI(wmcai@iris.sipp.ac.cn )
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 ([Ca
2+]
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 H
2O
2. A small, rapid increase in H
2O
2
content was followed by a much larger oxidative burst, with H
2O
2 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 [Ca
2+]
cyt and [H
2O
2], 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 H
2O
2 are required for OGA-induced gene expression.
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