Label-Free Quantitative Proteomics Analysis of Cotton Leaf Response to Nitric Oxide

To better understand nitric oxide (NO) responsive proteins, we investigated the proteomic differences between untreated (control), sodium nitroprusside (SNP) treated, and carboxy-PTIO potassium salt (cPTIO, NO scavenger) followed by SNP treated cotton plants. This is the first study to examine the effect of different concentrations of NO on the leaf proteome in cotton using a label-free approach based on nanoscale ultraperformance liquid chromatography-electrospray ionization (ESI)-low/high-collision energy MS analysis (MS(E)). One-hundred and sixty-six differentially expressed proteins were identified. Forty-seven of these proteins were upregulated, 82 were downregulated, and 37 were expressed specifically under different conditions. The 166 proteins were functionally divided into 17 groups and localized to chloroplast, Golgi apparatus, cytoplasm, and so forth. The pathway analysis demonstrated that NO is involved in various physiological activities and has a distinct influence on carbon fixation in photosynthetic organisms and photosynthesis. In addition, this is the first time proteins involved in ethylene synthesis were identified to be regulated by NO. The characterization of these protein networks provides a better understanding of the possible regulation mechanisms of cellular activities occurring in the NO-treated cotton leaves and offers new insights into NO responses in plants.