Biology Reference
In-Depth Information
Chapter 5
Reactive Oxygen Species and Cognate Redox
Signaling System in Plant Innate Immunity
Abstract
PAMP elicitor signals trigger a rapid and transient production of reactive
oxygen species (ROS) including hydrogen peroxide (H
2
O
2
), superoxide (O
2
−
),
singlet oxygen (
1
O
2
), and hydroxyl radical (OH˚). The oxidative burst is often a very
rapid response induced by elicitor, occurring within seconds to few minutes, sug-
gesting that the process may not require
de novo
protein synthesis but involves the
activation of pre-existing enzymes. Several enzymes including NADPH oxidases,
peroxidases, xanthine oxidase, amine oxidases, oxalate oxidase, glycollate oxidase,
urate oxidase and lipoxygenase have been implicated in the PAMP-induced ROS
production. H
2
O
2
is generated in apoplasts but accumulates to a greater extent in the
cytoplasm than in the apoplast. It has been suggested that the apoplastic H
2
O
2
is
translocated to cytoplasm for participation in the pathogen defense. ROS plays a
central role in launching the defense response against invading pathogens. ROS
induces Ca
2+
signaling system, reversible phosphorylation, ubiquitin-proteasome
signaling pathway, NO signaling system, salicylic acid signaling system,
ethylene- mediated signaling system, jasmonic acid signaling system, and abscisic
acid-mediated signaling system. The ROS signal functions are manifested as a con-
sequence of their ability to act as mobile carriers of an unpaired electron and are
involved in redox signaling system. Redox signaling occurs when at least one step
in a signaling event involves one of its components being specifi cally modifi ed by a
reactive oxygen species. Signaling through the redox active molecule H
2
O
2
has been
shown to be important in inducing plant defense responses. Expression of several
transcription factors has been shown to be regulated by H
2
O
2
and these transcription
factors may be direct targets for redox modifi cation by H
2
O
2
. ROS signaling system
and cognate redox signaling have been shown to be involved in activation of several
defense genes. Some pathogens could cause disease mostly by interfering with the
H
2
O
2
signaling pathway.
Keywords
Reactive oxygen species (ROS) PAMP-induced ROS production
ROS-induced signaling systems Redox signaling H
2
O
2
-regulated transcription
factors
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