Abstract
Recent advances in the studies with phloem sap have suggested that it might contain molecules involved in signal transduction. On a search for proteins and peptides that might function as signaling molecules, proteome analysis was performed with rice phloem sap of high purity that was obtained by the insect laser methods. Proteins and peptides in the sap were separated into several fractions, using gel electrophoresis, ion-exchange chromatography, and ultrafiltration techniques, and then subjected to the analysis with ion trap mass spectrometer equipped with nano-flow liquid chromatography. We identified more than 70 proteins including putative zinc finger-type transcription factors as well as metabolic enzymes and stress-responsive proteins that had been reported as phloem proteins. Based on our results, we will discuss possible mechanisms underlying signal transduction mediated by long-distance transport system. We also report proteins and peptides in xylem sap.
