Proteomic analysis of Cucumis sativus cotyledons after glucohexaose treatment as a part of ROS accumulation related resistance mechanism

Background: Glucohexaose is a safe farm chemical used for pathogen prevention, which can induce systemic acquired resistance in cucumber. Results: We found that glucohexaose treatment of cucumber plant induced an accumulation of the reactive oxidative species (ROS). Histochemistry showed sharp increases in O2- and H2O2 5 h after glucohexaose treatment. After 5 h, the O2- content decreased to a normal level, but the H2O2 content remained at a high level 10 h after glucohexaose treatment. And antioxidant enzymes were also changed after glucohexaose treatment. We also investigated the relationship between ROS accumulation and glucohexaose-induced proteome alteration using 2D electrophoresis coupled with MS/MS. 54 protein spots, which enhanced expression under glucohexaose treatment but suppressed the expression by application of DPI and DMTU, have been identified. Conclusion: Our study showed the accumulation of ROS is a part of mechanism of glucohexaose induced resistance in cucumber cotyledons. The up-regulated proteins identified by MS such as PP2C and antioxidation proteins are important in ROS signaling. It will be interesting to find out the regulatory mechanism underlying the induction of these proteins via ROS, and provide some clues to the mechanism of glucohexaose-induced resistance.