Comparative proteomic analysis of the Arabidopsis cbl1 mutant in response to salt stress

Many environmental stimuli, including light, biotic and abiotic stress factors, induce changes in cellular Ca(2+) concentrations in plants. Such Ca(2+) signatures are perceived by sensor molecules such as calcineurin B-like (CBL) proteins. AtCBL1, a member of the CBL family which is highly inducible by multiple stress signals, is known to function in the salt stress signal transduction pathway and to positively regulate the plant tolerance to salt. To shed light into the molecular mechanisms of the salt stress response mediated by AtCBL1, a two-dimensional DIGE proteomic approach was applied to identify the differentially expressed proteins in Arabidopsis wild-type and cbl1 null mutant plants in response to salt stress. Seventy-three spots were found altered in expression by least 1.2-fold and 50 proteins were identified by MALDI-TOF/TOF-MS, including some well-known and novel salt-responsive proteins. These proteins function in various processes, such as signal transduction, ROS scavenging, energy production, carbon fixation, metabolism, mRNA processing, protein processing and structural stability. Receptor for activated C kinase 1C (RACK1C, spot 715), a WD40 repeat protein, was up-regulated in the cbl1 null mutant, and two rack1c mutant lines showed decreased tolerance to salt stress, suggesting that RACK1C plays a role in salt stress resistance. In conclusion, our work demonstrated the advantages of the proteomic approach in studies of plant biology and identified candidate proteins in CBL1-mediated salt stress signaling network.