Proteomics approaches to identify molecular networks of the plant immune system

Aim of this study was the biochemical investigation of protein targets and protein complexes that are involved in plant defense mechanisms after the recognition of avirulence proteins (secreted by pathogens) by the plant resistance proteins. Previous studies led to the identification of 2 E3 ligases, the F-box protein ACF1 and the U-box protein CMPG1, that are required to activate the plant defense mechanism triggered by a variety of effectors or elicitors that are produced by different pathogens (Avr9, Avr4, AvrPto, Inf1, P50 helicase of Tobacco Mosaic Virus). E3 ligases are involved in the degradation of proteins in eukaryotic cells via the 26S proteolytic machinery that constitutes the major multi-component complex required for the degradation of proteins in cell. The role of E3 ligases in this complex is the recognition and destruction of target proteins that act as activators or repressors of signalling pathways in cells. Therefore, the discovery of the target proteins of ACF1 and CMPG1 in plants can lead to further clarification of the major pathways followed after the recognition in plant cells of microbial molecules produced by pathogenic plants. The ultimate goal is the discovery of new molecules that could contribute to new and more effective methods to control plant diseases. Modern biochemical and proteomics technologies (epitope tagging, affinity purification, co-immunoprecipation, LTQ-Mass Spectrometry and HMS-IPC: High-throughput mass spectrometric identification of protein complexes) were applied for the detection of proteins that might interact with the E3 ligases ACF1 and CMPG1.