Proteomic Response of Alfalfa Subjected to Aluminum (Al) Stress at Low pH Soil

Abstract

In order to reveal the aluminum (Al) stress tolerance mechanisms in alfalfa plant at low pH soil, a proteomic approach hasbeen conducted. Alfalfa plants were exposed to Al stress for 5 days. The plant growth and total chlorophyll content are greatlyaffected by Al stress. The malondialdehyde (MDA) and H2O2 contents were increased in a low amount but free proline andsoluble sugar contents, and the DPPH-radical scavenging activity were highly increased. These results indicate that antioxidantactivity (DPPH activity) and osmoprotectants (proline and sugar) may involve in ROS (H2O2) homeostasis under Al stress. Inproteomic analysis, over 500 protein spots were detected by 2-dimentional gel electrophoresis analysis. Total 17 Al stress-inducedproteins were identified, of which 8 protein spots were up-regulated and 9 were down-regulated. The differential expressionpatterns of protein spots were selected and analyzed by the peptide mass fingerprinting (PMF) using MALDI-TOF MS analysis. Three protein spots corresponding to Rubisco were significantly down-regulated whereas peroxiredoxin and glutamine synthetasewere up-regulated in response to Al stress. The different regulation patterns of identified proteins were involved in energymetabolism and antioxidant / ROS detoxification during Al stress in alfalfa. Taken together, these results provide new insight tounderstand the molecular mechanisms of alfalfa plant in terms of Al stress tolerance.