Poster: Oxidative stress

Abs # 92: OXI1 regulates active oxygen species- induced MAPKs in Arabidopsis

Presenter:	Lecourieux, David , david.lecourieux@univie.ac.at
Authors	Lecourieux, David  (A)   Lecourieux-Ouaked, Fatma  (A)   Rentel, Maike  (B)   Usher, Sarah  (C)   Petersen, Lindsay  (D)   Okamoto, Haruko  (B)   Knight, Heather  (B)   Peck, Scott  (E)   Grierson, Claire  (C)   Knight, Marc  (B)   Hirt, Heribert  (A)
Affiliations:	(A): Institute of Microbiology and Genetics, University of Vienna Biocenter-GMI (B): Dept. of Plant Sciences, University of Oxford (C): School of Biological Sciences, University of Bristol (D): Dept. of Molecular and Cell Biology, University of Cape Town (E): Sainsbury Laboratory

Active oxygen species (AOS) generated in response to stimuli and during development are able to function as signalling molecules in eukaryotes, leading to specific downstream responses. In plants, these include such diverse processes as coping with stress (e.g. pathogen attack, wounding and oxygen deprivation), ABA-induced guard cell closure and cellular development, e.g. root hair growth. Despite the importance of AOS signalling in eukaryotes, little is known about the protein components operating downstream of AOS that mediate any of these processes. In many eukaryotes, the transduction of H₂O₂ signals is controlled by protein phosphorylation involving mitogen-activated protein kinases (MAPKs). In plants, H₂O₂ activates several MAPKs but how this activation is achieved remained unclear. In Arabidopsis, H₂O₂ activates the MAPKs, MPK3 and MPK6 via MAPKKK ANP1. In this work, we identified a new Arabidopsis serine/threonine protein kinase, OXI1 (for oxidative stress inducible 1). Our results show that OXI1 is an essential component of the signalling pathways linking oxidative burst signals to diverse downstream responses. Expression of OXI1 is induced by a wide range of H₂O₂-generating stimuli. OXI1 kinase activity is itself also induced by H₂O₂ in vivo. Additionally, we show that OXI1 is required for full activation of both MPK3 and MPK6 upon AOS or elicitor treatment, suggesting the involvement of OXI1 usptream of these two MAPKs. Finally, phenotypic analysis demonstrated that OXI1 is involved at least in two different AOS-mediated processes: basal resistance to Peronospora parasitica infection and root hair growth.