Salt Stress Induced Differential Proteome and Metabolome Response in the Shoots of Aeluropus lagopoides (Poaceae), a Halophyte C-4 Plant

A proteomic approach was used to identify proteins affected by salt in the halophyte C-4 plant Aeluropus lagopoides (Poaceae) in an attempt to understand the mechanism of salt tolerance. Plants were treated with 450 mM NaCl for 10 days, and proteins were then extracted from the shoots and separated by two-dimensional polyacrylamide gel electrophoresis. A total of 1805 protein spots were detected, of which 39 were up-regulated and 44 were down-regulated by treatment with NaCl. Metabolism-related proteins were up-regulated, whereas photosynthesis-related proteins were down-regulated. Dose-dependence studies showed that the up-regulation continued at NaCl concentrations above 450 mM for defense-related proteins alone. Western blot analysis confirmed the down-regulation of RuBisCO LSU and RuBisCO SSU and severe down-regulation of RuBisCO activase. The activity of glyoxalase I increased with increasing NaCl concentration. Metabolome studies indicated up-regulation of amino acids and down-regulation of tricarboxylic acid cycle-related metabolites. These studies suggest that up-regulation of energy formation, amino acid biosynthesis, C-4 photosynthesis, and detoxification are the main strategies for salt tolerance in A. lagopoides.