Comprehensive proteomic analysis of canola leaf inoculated with a plant growth-promoting bacterium, Pseudomonas fluorescens, under salt stress.

Plant growth-promoting bacteria can improve the tolerance of canola to salt stress. To better understand the effects of plant growth-promoting bacterium on the protein profiles of canola under salt stress condition, proteomics was performed. Salt-sensitive (Sarigol) and -tolerant (Hyola308) canola cultivars were inoculated with Pseudomonas fluorescens FY32, and the protein profiles of canola leaves were compared using a PEG-fractionation method. Cluster analysis of canola cultivars based on a stress tolerance index of several morphological parameters was used to confirm that Sarigol and Hyola308 were salt-sensitive and -tolerant cultivars, respectively. Using a gel-free proteomic technique, 154 and 94 proteins in Hyola308 and 100 and 144 proteins in Sarigol were uniquely identified in non-inoculated and bacterial-inoculated cultivars, respectively. By PEG fractionation, a total of 132 and 207 proteins were identified in non-inoculated and inoculated Hyola308, respectively. Notably, the abundance of copper/zinc superoxide dismutase 1 was significantly increased in inoculated Hyola308 under severe salt stress and decreased under moderate salt stress. In addition, the enzyme activity of delta-1-pyrroline-5-carboxylate synthase was significantly increased non-inoculated Hyola308 and the activity of succinate dehydrogenase was increased in inoculated Hyola308 leaves exposed to salt stress. Taken together, these results suggest that the bacterial inoculation of canola increases salt tolerance by inducing an increase in the abundance of proteins related to glycolysis, tricarboxylic acid cycle, and amino acid metabolism.