Combined effects of the plant growth-promoting bacterium Pseudomonas putida UW4 and salinity stress on the Brassica napus proteome

The influences of two strains of Pseudomonas putida UW4, a plant growth-promoting bacterium (PGPB) on the shoot and root proteomic profiles of Brassica napus (canola) were examined under salinity stress using two-dimensional difference gel electrophoresis. The two strains (wild-type UW4 and an AcdS minus mutant strain) differ in the availability of a functional 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase, a bacterial protein known to play a role in host plant's stress responses. In total, ninety protein spots (representing 76 different proteins) with significantly altered expression levels in the presence of salt and/or bacteria were identified by mass spectrometry. Many of the identified proteins are involved in photosynthesis, anti-oxidative processes, transportation across membranes, and pathogenesis-related responses. The effects of salt and bacteria on the canola proteome were shown to be quite diverse, with salinity stress causing more dramatic plant protein expression changes than bacteria. In addition, bacteria were demonstrated to moderate some of the salt effects on plant protein differential expression. This work contributes to the understanding of how plant protein expression is affected by various environmental signals.