Cucumber mosaic virus resistance: Comparative proteomics of contrasting Cucumis sativus cultivars after long-term infection

Plant viruses are a major threat for a wide range of host species, causing substantial losses in agriculture. Particularly, Cucumber mosaic virus (CMV) evokes severe symptoms, thus dramatically limiting yield. Activation of plant immunity is associated with changes in the gene expression and consequently, cellular proteome to ensure virus resistance. Proteomics proved to be an extremely valuable tool for discovering multiple targets for the rational design of plant protection strategies. Herein, we studied two cultivars of cucumber (Cucumis sativus) resistant ´Heliana´ and susceptible ´Vanda´. Plant cotyledons were mechanically inoculated with CMV isolate PK1, and systemic leaves were harvested at 33 days post-inoculation. Upon protein extraction and filter-aided sample preparations, peptides were profiled by ultrahigh-performance liquid chromatography and comprehensively quantified by ion mobility enhanced mass spectrometry. From 1,516 reproducibly quantified proteins using label-free approach, 133 were differentially abundant among genotypes or treatments by strict statistic and effect size criteria. Pigments and hydrogen peroxide measurements corroborated proteomic findings. Advanced bioinformatics revealed a modular network of affected host proteins. Direct comparison of both genotypes in the uninfected state highlighted more abundant photosynthetic and development-related proteins in resistant cucumber cultivar. Long-term CMV infection showed worse preservation of energy processes and less robust translation in susceptible cultivar versus resistant genotype. Contrary, susceptible cultivar had numerous more abundant stress and defense-related proteins. We proposed promising targets for functional validation in transgenic lines a step toward durable virus resistance in cucurbits and other crops.