Identification of defence-related cell wall proteins in Phytophthora sojae-infected soybean roots by ESI-MS/MS

Root cell wall proteins involved in the incompatible interaction between soybean (Glycine max L.) and the phytopathogenic oomycete Phytophthora sojae were investigated by a proteomic approach using ESI-MS/MS analysis. Success of infection and subsequently induced defence reactions was proven by staining the cell wall localized defence-related 1,3-β-glucan, callose, in semi-thin sections of the roots. Cell wall proteins of roots were extracted three weeks post-infection, separated by SDS-PAGE and eight selected protein bands were digested with trypsin. The resulting peptides were subjected to mass spectrometry-based sequencing. For four proteins, amino acid sequence information was obtained and used to identify the corresponding proteins by a homology search in databases. All four proteins (cationic peroxidase, peroxidase precursor, amine oxidase and lipoxygenase) were defence-related and their involvement in the oxidative burst is discussed. Three of these proteins have not been described for soybean before