The phosphoproteome of Arabidopsis plants lacking the oxidative signal‐inducible1 (OXI1) protein kinase

Abstract

Summary• The AGC protein kinase OXI1 is a key protein in plant responses to oxidative signals, and is important for two oxidative burst-mediated processes: basal resistance to microbial pathogens and root hair growth. To identify possible components of the OXI1 signalling pathway, phosphoproteomic techniques were used to detect alterations in the abundance of phosphorylated proteins and peptides in an oxi1 null mutant of Arabidopsis thaliana.• The relative abundance of phosphorylated proteins was assessed either using two-dimensional gel electrophoresis and staining with the phosphoprotein stain Pro-Q Diamond or by the identification and quantification, by mass spectrometry, of stable-isotope labelled phosphopeptides.• A number of proteins show altered phosphorylation in the oxi1 mutant. Five proteins, including a putative F-box and 3-phosphoinositide-dependent kinase 1, show reduced phosphorylation in the oxi1 mutant, and may be direct or indirect targets of OXI1. Four proteins, including ethylene insensitive 2 and phospholipase D-gamma, show increased phosphorylation in the oxi1 mutant.• This study has identified a range of candidate proteins from the OXI1 signalling pathway. The diverse activities of these proteins, including protein degradation and hormone signalling, may suggest crosstalk between OXI1 and other signal transduction cascades.

Genetical Genomics Reveals Large Scale Genotype-By-Environment Interactions in Arabidopsis thaliana

“…Also in expanding cells and growth in response to changing light conditions ROS signaling may be expected (Carol and Dolan, 2006). The ACG kinase OXI1 was found to target not only CSN5A for phosphorylation (Howden et al, 2010), but also 3′phosphoinositide-dependent kinase-1 (PDK1) a conserved lipid-activated master kinase (Anthony et al, 2004; Zalejski and Bögre, 2010). OXI1 in turn is activated by PDK1 that in addition regulates a number of other AGC kinases.…”

“…Mutant phenotypes of this gene have the constitutively photomorphogenic/de-etiolated/fusca ( cop/det/fus ) mutant phenotype (Dohmann et al, 2005) of light-grown seedlings when grown in the dark. In an analysis of targets of OXI1 CSN5A was found to be phosphorylated (Howden et al, 2010). It could very well be that the differential expression and activity of this gene between L er and Cvi could account for the diverse processes differentially affected by the HTR in response to low light.…”

Reactive oxygen species generation and signaling in plants

“…145 Five proteins, including a putative F-box and 3-phosphoinositide-dependent kinase 1 (PDK1), show reduced phosphorylation in the oxi1 mutant, and may be direct or indirect targets of OXI1. Four proteins, including ethylene insensitive 2 and phospholipase Dγ, show increased phosphorylation in the oxi1 mutant.…”

“…The diverse activities of these proteins, including protein degradation and hormone signalling, may suggest crosstalk between OXI1 and other signal transduction cascades. 145 A MAPK cascade involving MAPK3/6 acts downstream of OXI1 and controls the activation of different defense mechanisms in response to ROS stresses. 1,146 MAPKs are also activated by PDK1 through the phospholipase-C/Dphosphatidic-acid pathway.…”

AGC kinases in plant development and defense

“…A recent phosphoproteome analysis of Arabidopsis roots identified differentially phosphorylated proteins in oxi1 seedlings in response to cellulase treatment. 39 Similar approaches could be used to compare potential components of the OXI1 signaling pathway in response to different stimuli. Given that OXI1 shows different expression patterns in roots and aerial tissues, 18 the specificity of OXI1 signaling could also change depending on the plant tissue.…”