Response to biotic and oxidative stress in arabidopsis thaliana: analysis of variably phosphorylated proteins

Protein phosphorylation plays a pivotal role in the regulation of many cellular events;increasing evidences indicate that this post-translational modification is involved in plantresponse to various abiotic and biotic stresses. Since phosphorylated proteins may bepresent at low abundance, enrichment methods are generally required for their analysis.We here describe the quantitative changes of phosphoproteins present in Arabidopsisthaliana leaves after challenging with elicitors or treatments mimicking biotic stresses,which stimulate basal resistance responses, or oxidative stress. Phosphoproteins fromelicited and control plants were enriched by means of metal oxide affinity chromatographyand resolved by 2D electrophoresis. A comparison of the resulting proteomic mapshighlighted phosphoproteins showing quantitative variations induced by elicitor treatment;these components were identified by MALDI-TOF peptide mass fingerprinting and/or nanoLCESI-LIT-MS/MS experiments. In total, 97 differential spots, representing 75 unique candidatephosphoproteins, were characterized. They are representative of different protein functionalgroups, such as energy and carbon metabolism, response to oxidative and abiotic stresses,defense, protein synthesis, RNA processing and cell signaling. Ascertained proteinphosphorylation found a positive confirmation in available Arabidopsis phosphoproteomedatabase. The role of each identified phosphoprotein is here discussed in relation to plantdefense mechanisms. Our results suggest a partial overlapping of the responses to differenttreatments, as well as a communication with key cellular functions by imposed stresses.