Proteomic and physiological responses of Arabidopsis thaliana exposed to salinity stress and N-acyl-homoserine lactone.

To evaluate the alleviating action of exogenous N-acyl-homoserine lactones (AHLs) on NaCl toxicity, morphological, physiological and proteomic changes were investigated in Arabidopsis thaliana seedlings. Salinity stress decreased growth parameters, increased malondialdehyde (MDA) contents and antioxidant enzymes such as superoxide dismutase (SOD), guaiacol peroxidase (POD) and catalase activities. Application of lower concentration of AHL had a relieving effect on Arabidopsis seedlings under salinity stress which dramatically decreased MDA content, and increased growth parameters as well as SOD and POD activities. Total proteins were extracted from the control, NaCl-, AHL- and NaCl + AHL-treated seedlings and were separated using two-dimensional gel electrophoresis. A total of 127 protein spots showed different expression compared with the control. Mass spectrometry analysis allowed the identification of 97 proteins involved in multiple pathways, i.e. defense/stress/detoxification, photosynthesis, protein metabolism, signal transduction, transcription, cell wall biogenesis, metabolisms of carbon, lipid, energy, sulfur, nucleotide and sugar. These results suggest that defense/stress response, metabolism and energy, signal transduction and regulation, protein metabolism and transcription-related proteins may be particularly subjected to regulation in salt stressed Arabidopsis seedlings, when treated with AHL and that this regulation lead to improved salt tolerance and plant growth. Overall, this study provides insight to the effect of AHL on salinity stress for the first time, and also sheds light on overview of the molecular mechanism of AHL-regulated plant growth promotion and salt resistance.