Proteomic analysis of glucohexaose induced resistance to downy mildew in Cucumis sativus

Glucohexaose, as one of synthetic oligosaccharides, induces the resistance response to protect plants from pathogen infection by inducing the systemic acquired resistance-like (SAR-like) response. To study the molecular mechanism of glucohexaose induced resistance, we investigate the physiological, biochemical and proteomic changes after glucohexaose treatment. The results shows cucumber plants had the highest protection level of 66.79% 48 h after the third times of 10 μg mL^-1glucohexaose treatment. Significant increases in chlorophyll, photo synthetic rate, soluble sugar, leave dry weight and H₂O₂ were observed after glucohexaose treatment. Eighteen up-regulated proteins were identified by MALDI-TOF/TOF in glucohexaose-treated plants, predicted to be involved in photosynthesis, photorespiration, oxidative burst, transcriptional regulation, signal transduction and pathogen defense processes. The identification of up-regulated proteins involved in photo synthetic processes is a significant finding which suggests that a boost in metabolites is required for repartition of resources towards defense mechanisms. The proteins which responded to glucohexaose also included those associated with oxidative burst response, such as APX and isocitrate dehydrogenase. More comprehensive studies about the link between the molecular mechanisms regulated by ROS mediated photosynthesis and cucumber induced resistance by glucohexaose, are necessary in the future to broaden our understanding of induced resistance in plants.