Identification of Susceptibility Genes for in Cucumber via Comparative Proteomic Analysis.

wilt () in cucumber ( L.), caused by f. sp. cucumerinum (Foc), poses a major threat to cucumber growth and productivity. However, lack of available natural resistance resources for restricts the breeding of resistant cultivars via conventional approaches. Susceptibility (S) genes in susceptible host plants facilitate infection by the pathogen and contribute to susceptibility. Loss of function of these S genes might provide broad-spectrum and durable disease resistance. Here, we screened S genes via comparative proteomic analysis between cucumber cultivars Rijiecheng and Superina, which exhibited resistance and high -susceptibility to , respectively. We identified 210 and 243 differentially regulated proteins (DRPs) in the Rijiecheng and Superina, respectively, and further found that 32 DRPs were predominantly expressed in Superina and significantly up-regulated after Foc inoculation. Expression verification found that (), encoding a transmembrane protein, (), encoding function as a tetraspanin, () encoding a terpene synthase, and (), encoding a glycosyltransferase, were significantly induced in both cultivars after Foc infection but were induced to a higher expression level in Superina. These candidate genes might act as negative regulators of resistance in cucumber and provide effective -susceptibility gene resources for improving cucumber resistance through breeding programs.