Proteomics reveals the overlapping roles of hydrogen peroxide and nitric oxide in the acclimation of citrus plants to salinity

P>Hydrogen peroxide (H2O2) and nitric oxide (center dot NO) are key reactive species in signal transduction pathways leading to activation of plant defense against biotic or abiotic stress. Here, we investigated the effect of pre-treating citrus plants (Citrus aurantium L.) with either of these two molecules on plant acclimation to salinity and show that both pre-treatments strongly reduced the detrimental phenotypical and physiological effects accompanying this stress. A proteomic analysis disclosed 85 leaf proteins that underwent significant quantitative variations in plants directly exposed to salt stress. A large part of these changes was not observed with salt-stressed plants pre-treated with either H2O2 or sodium nitroprusside (SNP; a center dot NO-releasing chemical). We also identified several proteins undergoing changes either in their oxidation (carbonylation; 40 proteins) and/or S-nitrosylation (49 proteins) status in response to salinity stress. Both H2O2 and SNP pre-treatments before salinity stress alleviated salinity-induced protein carbonylation and shifted the accumulation levels of leaf S-nitrosylated proteins to those of unstressed control plants. Altogether, the results indicate an overlap between H2O2- and center dot NO-signaling pathways in acclimation to salinity and suggest that the oxidation and S-nitrosylation patterns of leaf proteins are specific molecular signatures of citrus plant vigour under stressful conditions.