OXI1 kinase is necessary for oxidative burst-mediated signalling in Arabidopsis

Abstract

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 H2O2-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.

Involvement of sphingoid bases in mediating reactive oxygen intermediate production and programmed cell death in Arabidopsis

“…These observations suggest that the sphingolipid-mediated cell death is coupled with the generation of ROIs, which, in turn, may activate a downstream PCD pathway. Among the currently known components involved in the ROI-mediated signaling, the structurally related zinc-finger proteins LSD1 and LOL1 presumably act to monitor the cellular ROI levels [32,55,56], whereas the serine/threonine protein kinase OXI1 appears to link an oxidative burst signal with diverse downstream responses [57]. Moreover, overexpression of the Arabidopsis Bax Inhibitor-1 renders the transgenic plants insensitive to ROIs induced by a number of stimuli [58].…”

Mitogen-Activated Protein Kinases and Reactive Oxygen Species Signaling in Plants

“…The effect of NDPK2 might be mediated by MPK3 and MPK6, because NDPK2 can interact and activate these two MAPKs (Moon et al, 2003). Another upstream mediator of MPK3 and MPK6 is the OXI1 protein kinase (Rentel et al, 2004). Oxi1 null mutants are hypersensitive to infection by virulent fungal pathogens and are compromised in ROS-and elicitor-induced MAPK activation.…”

“…ROS were localized in the growing tips of root hairs of wild-type plants but not in the rhd2 mutant. Possibly, the NADPH oxidase is controlled via small GTPases of the Rop family (BaxterBurrell et al, 2002;Gu et al, 2003) (Rentel et al, 2004), two factors known to be regulating root hair growth. Oxi1 null mutants are impaired in the activation of the MAPKs MPK3 and MPK6 upon oxidative stress (Rentel et al, 2004), suggesting that OXI1 functions downstream of ROS but upstream of the MAPK module.…”

“…Possibly, the NADPH oxidase is controlled via small GTPases of the Rop family (BaxterBurrell et al, 2002;Gu et al, 2003) (Rentel et al, 2004), two factors known to be regulating root hair growth. Oxi1 null mutants are impaired in the activation of the MAPKs MPK3 and MPK6 upon oxidative stress (Rentel et al, 2004), suggesting that OXI1 functions downstream of ROS but upstream of the MAPK module. An earlier study had already linked the stress-induced alfalfa (Medicago sativa) MAPK SIMK, the putative ortholog of Arabidopsis MPK6, to root hair growth (Samaj et al, 2002).…”

Hydrogen Peroxide-induced Cell Death in Arabidopsis: Transcriptional and Mutant Analysis Reveals a Role of an Oxoglutarate-dependent Dioxygenase Gene in the Cell Death Process

“…The expression pattern of selected genes was verified by northern blot analysis (data not shown). The list of upregulated genes included many glutathione-S-transferases (GSTs) and heat shock proteins, two regulons that are markers for H 2 O 2 inducibility (13), many members of the proteasome pathway and the recently identified H 2 O 2 -relaying serine-threonine kinase oxi1 (14).…”