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Biochem. J. (1997) 322, 681–692 (Printed in Great Britain)

REVIEW ARTICLE

Oxidative burst : an early plant response to pathogen infection
Przemys0aw WOJTASZEK
Institute of Bioorganic Chemistry, Polish Academy of Sciences, Noskowskiego 12/14, 61-704 Poznan! , Poland

As plants are confined to the place where they grow, they have
to develop a broad range of defence responses tocope with
pathogenic infections. The oxidative burst, a rapid, transient,
production of huge amounts of reactive oxygen species (ROS), is
one of the earliest observable aspects of a plant ’s defence strategy.
First this Review describes the chemistry of ROS (superoxide
radical, hydrogen peroxide and hydroxyl radical). Secondly, the
role of ROS in defence responses is demonstrated, and someimportant issues are considered, such as : (1) which of the ROS
is a major building element of the oxidative burst ; (2) the spatial
and temporal regulation of the oxidative burst ; and (3) differences
in the plant’s responses to biotic and abiotic elicitation. Thirdly,
the relationships between the oxidative burst and other plant
defence responses are indicated. These include : (1) an oxygenconsumption, (2) the production of phytoalexins, (3) systemic

acquired resistance, (4) immobilization of plant cell wall proteins,
(5) changes in membrane permeability and ion fluxes and (6) a
putative role in hypersensitive cell death. Wherever possible, the
comparisons with models applicable to animal systems are
presented. Finally, the question of the origin of ROS in the
oxidative burstis considered, and two major hypotheses, (1) the
action of NADPH oxidase system analogous to that of animal
phagocytes, and (2) the pH-dependent generation of hydrogen
peroxide by a cell wall peroxidase, are presented. On the basis of
this material, a third ‘ unifying ’ hypothesis is presented, where
transient changes in the pH of the cell wall compartment are
indicated as a core phenomenonin evoking ROS production.
Additionally, a germin\oxalate oxidase system which generates
H O in response to pathogenic infection is also described.
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INTRODUCTION

These include rapid and transient responses that occur mainly at
the plant cell surface and are based on the activation of preexisting components rather than involving the biosynthetic
machinery of the cell. Among thereactions identified were :
release of reactive oxygen species (ROS) termed the ‘ oxidative
burst ’ [11–14], changes in exocellular pH and in membrane
potentials [15,16], ion fluxes [17–19], changes in protein phosphorylation patterns [15,20,21], and the oxidative immobilization
of plant cell wall proteins [22,23].
Most cells possess the ability to produce and detoxify ROS. In
normal conditions ROSappear in cells as inevitable by-products
formed as a result of successive one-electron reductions of
molecular oxygen (O ). Most cells have also acquired the relevant
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protective mechanisms to maintain the lowest possible levels of
ROS inside the cell. In some cases, however, especially under
stress conditions, these protective mechanisms are overridden by
the rapid, transient, productionof huge amounts of ROS, namely
the oxidative burst. This reaction has been known for more
than 30 years in mammals from studies on the ‘ respiratory burst ’
in phagocytes (reviewed in [24,25]). However, in plants the
phenomenon was first demonstrated much later [26], and recently
published data have indicated that the ROS produced in the
oxidative burst could serve not only as protectantsagainst
invading pathogen, but could also be the signals activating
further plant defence reactions, including the HR of infected
cells [27].
This Review first describes the chemistry of the ROS, their role
in the oxidative burst and in induction of other defence reactions.
As the origin of ROS building the oxidative burst is now
probably the major controversy in this research area, hypotheses...