Proteomic analysis of Chelidonium majus milky sap using two-dimensional gel electrophoresis and tandem mass spectrometry.

Milky sap, a milky-like orange fluid, isolated from the Greater Celandine (Chelidonium majus L.), family Papaveraceae, serves as a rich source of various biologically active substances such as alkaloids, several flavonoids, phenolic acids and proteins. The objective of this study was to separate Ch. majus milky sap extract proteins using two-dimensional gel electrophoresis (2-DE) to demonstrate for the first time the protein composition in the sap and to identify them using liquid chromatography-tandem mass spectrometry analysis (LC-ESI-MS/MS). It was possible to identify 21 proteins, which comprise disease/defence-related, signalling, Krebs cycle, nucleic acid binding and other proteins. The majority of the identified proteins can be linked to direct and indirect stress and defence reactions, e.g. against different pathogens. The specific protein composition of the milky sap suggests an important role of these proteins for the whole plant physiology and development.