Proteomic Analysis of PEG-Fractionated UV-C Stress-Response Proteins in Globe Artichoke

Plants respond to UV stress by producing antioxidant molecules and by altering their metabolism through the regulation of specific gene family members. Globe artichoke (Cynara cardunculus var. scolymus L.-Compositae family) is an attractive model species for studying the protein networks involved in UV response, being characterised by high loads of antioxidants, which are boosted by UV-C rays. The effect of UV-C on leaf proteome was investigated 24 h after irradiation by applying a polyethylene glycol (PEG) fractionation method, which we previously developed to cope with the so-called high abundance proteins, followed by two-dimensional electrophoresis analysis. Thirty-eight UV-C modulated proteins were analysed by means of a nano-liquid chromatography-nanospray tandem mass spectrometry, and 27 were successfully identified using a customised Compositae protein database, including a set of 19,055 globe artichoke unigenes. Proteins were categorised according to Gene Ontology (GO) and visualised on their cellular pathway: Most of them were involved not only in primary metabolism (e.g. photosynthesis) and in abiotic stress responses (e.g. reactive oxygen species scavenging) but also in cell wall modification, secondary metabolism, and regulation of transcription. To date, this is the first report on globe artichoke proteomic expression analysis following abiotic stress. Our results confirm the effectiveness of the PEG fractionation method in excluding most of the ribulose bisphosphate carboxylase/oxygenase and highlighting some major occurring phenomena.