title: Hydrogen Peroxide, Signaling in Disguise during Metal Phytotoxicity.
abstract: Plants exposed to excess metals are challenged by an increased generation of reactive oxygen species (ROS) such as superoxide ([Formula: see text]), hydrogen peroxide (H2O2) and the hydroxyl radical ((•)OH). The mechanisms underlying this oxidative challenge are often dependent on metal-specific properties and might play a role in stress perception, signaling and acclimation. Although ROS were initially considered as toxic compounds causing damage to various cellular structures, their role as signaling molecules became a topic of intense research over the last decade. Hydrogen peroxide in particular is important in signaling because of its relatively low toxicity, long lifespan and its ability to cross cellular membranes. The delicate balance between its production and scavenging by a plethora of enzymatic and metabolic antioxidants is crucial in the onset of diverse signaling cascades that finally lead to plant acclimation to metal stress. In this review, our current knowledge on the dual role of ROS in metal-exposed plants is presented. Evidence for a relationship between H2O2 and plant metal tolerance is provided. Furthermore, emphasis is put on recent advances in understanding cellular damage and downstream signaling responses as a result of metal-induced H2O2 production. Finally, special attention is paid to the interaction between H2O2 and other signaling components such as transcription factors, mitogen-activated protein kinases, phytohormones and regulating systems (e.g. microRNAs). These responses potentially underlie metal-induced senescence in plants. Elucidating the signaling network activated during metal stress is a pivotal step to make progress in applied technologies like phytoremediation of polluted soils.
authors.affiliation: Environmental Biology, Centre for Environmental Sciences, Hasselt University Diepenbeek, Belgium.
authors.forename: Ann
authors.initials: A
authors.lastname: Cuypers
authors.affiliation: Environmental Biology, Centre for Environmental Sciences, Hasselt University Diepenbeek, Belgium.
authors.forename: Sophie
authors.initials: S
authors.lastname: Hendrix
authors.affiliation: Environmental Biology, Centre for Environmental Sciences, Hasselt University Diepenbeek, Belgium.
authors.forename: Rafaela
authors.initials: R
authors.lastname: Amaral Dos Reis
authors.affiliation: Environmental Biology, Centre for Environmental Sciences, Hasselt University Diepenbeek, Belgium.
authors.forename: Stefanie
authors.initials: S
authors.lastname: De Smet
authors.affiliation: Environmental Biology, Centre for Environmental Sciences, Hasselt University Diepenbeek, Belgium.
authors.forename: Jana
authors.initials: J
authors.lastname: Deckers
authors.affiliation: Environmental Biology, Centre for Environmental Sciences, Hasselt University Diepenbeek, Belgium.
authors.forename: Heidi
authors.initials: H
authors.lastname: Gielen
authors.affiliation: Environmental Biology, Centre for Environmental Sciences, Hasselt University Diepenbeek, Belgium.
authors.forename: Marijke
authors.initials: M
authors.lastname: Jozefczak
authors.affiliation: Environmental Biology, Centre for Environmental Sciences, Hasselt University Diepenbeek, Belgium.
authors.forename: Christophe
authors.initials: C
authors.lastname: Loix
authors.affiliation: Environmental Biology, Centre for Environmental Sciences, Hasselt University Diepenbeek, Belgium.
authors.forename: Hanne
authors.initials: H
authors.lastname: Vercampt
authors.affiliation: Environmental Biology, Centre for Environmental Sciences, Hasselt University Diepenbeek, Belgium.
authors.forename: Jaco
authors.initials: J
authors.lastname: Vangronsveld
authors.affiliation: Environmental Biology, Centre for Environmental Sciences, Hasselt University Diepenbeek, Belgium.
authors.forename: Els
authors.initials: E
authors.lastname: Keunen
keywords: crosstalk; damage; hydrogen peroxide; metals; oxidative stress; signaling