Comparative Proteomics Analysis Of Cucumber Leaves In Response To Corynespora Cassiicola

Cucumber target leaf spot, a world wide fungicidal disease of cucumber, is caused by Corynespora cassiicola. Both seedlings and mature seedlings can be infected in fields or greenhouses. It has become a serious problem in cucumber protected cultivation of Northern China. Under severe infection, the cucumber yield could be large-scale reduced. Since biological process was ultimately controlled by protein, and most of the mechanisms of plant resistance to pathogens are associated to the differential expression of proteins. Exploring the changes of plant proteome under stress conditions thus acquiring relationships between proteins and disease resistance will help illuminate the molecular mechanisms involved in the host resistance.Cucumber resistant cultivar Jinyou 38 and susceptible cultivar Ludixianfeng were used as materials in this experiment, histochemistry staining was used to study the time variation features of of oxidative burst and lignin deposition in cucumber leaves aftep Corynespora cassiicola inoculation, thus help choose treatment time points for further proteomic analysis. ITRAQ quantitative proteomics technique was used to explore the proteome from cucumber leave total protein of resistant cultivar in response to Corynespora cassiicola infestation. qRT-PCR technique were used to study gene expression of several disease-related proteins. The research provide important informations on the molecular basis of cucumber defense against target leaf spot.1. Time variation features of of oxidative burst and lignin deposition in cucumber leaves were investigated in our study. The results showed two increases in ROS leave:an initial increase at 6 hai and a larger increase at 24 hai. The initial lignin deposition appeared at 12 hai, and it showed large regions at 24 and 48 hai.2. ITRAQ quantitative proteomics technique was used to analysis the changes of cucumber leave proteome under Corynespora cassiicola treatment at 6h and 24h.286 differential proteins were identified. These differentially expressed proteins were broadly classified through GO annotation, KEGG pathway analysis and related literature as:defense, signal or stress response, cell metabolism, antioxidant, biological regulation or transport and other proteins. These differentially expressed proteins probablely play important role in the formation of cucumber disease resistance.3. qRT-PCR technique was used to study the expression of 10 disease-related proteins at mRNA level, including subtilisin-like protease, serine/threonine-protein kinase, pentatricopeptide repeat-containing protein, acc oxidase, non-specific lipid-transfer protein,12-oxophytodienoate reductase 1, dirigent protein, mlo family protein, mlp-like protein and phospholipase D. The results showed that different genes have different expression patterns, and there may be different regulatory mechanisms between protein and mRNA. Significant changes of these genes at mRNA levels in respond to pathogen infection indicat that they may play an important role in cucumber resistence to corynespora cassiicola.