Active oxygen species (AOS) generated in response to stimuli and during development can function as signalling molecules in eukaryotes, leading to specific downstream responses. In plants these include such diverse processes as coping with stress (for example pathogen attack, wounding and oxygen deprivation), abscisic-acid-induced guard-cell closure, and cellular development (for example root hair growth). Despite the importance of signalling via AOS in eukaryotes, little is known about the protein components operating downstream of AOS that mediate any of these processes. Here we show that expression of an Arabidopsis thaliana gene (OXI1) encoding a serine/threonine kinase is induced in response to a wide range of H 2O2-generating stimuli. OXI1 kinase activity is itself also induced by H2O2 in vivo. OXI1 is required for full activation of the mitogen-activated protein kinases (MAPKs) MPK3 and MPK6 after treatment with AOS or elicitor and is necessary for at least two very different AOS-mediated processes: basal resistance to Peronospora parasitica infection, and root hair growth. Thus, OXI1 is an essential part of the signal transduction pathway linking oxidative burst signals to diverse downstream responses.
|Original language||English (US)|
|Number of pages||4|
|State||Published - Feb 26 2004|
Bibliographical noteFunding Information:
Acknowledgements We thank A. Rehmany for the P. parasitica isolates; A. Hailey for statistical analysis; B. Ellis and G. Miles for discussions; and N. Evans, S. Gurr and R. Capper and K. Denby for practical and moral support. This work was funded by the BBSRC, the Gatsby Foundation, the EU TMR program, the Cannon Collins Educational Trust for Southern Africa (CCETSA), the South African National Research Foundation (NRF), and the Austrian Science Foundation.
Acknowledgements We thank P. Rich for helpful discussions, S. Ranasinghe for technical help with the FLIPR, and A. Scott for the illustrations. Financial support was provided by the Wellcome Trust and Medical Research Council.
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