Cell wall preparation from M. sativa stems. A – Schematic representation of the purification procedure of cell walls from M. sativa stems, and of the different extracts obtained . B – Number of proteins identified in each extract after 2D-GE separation and LC-MS/MS analysis. Proteins were classified as indicated in legend to Figure 1. Since the M. sativa genome is not fully sequenced, the sequence of the N-terminus of some proteins is not known. They were classified as "not predictable". Twenty-five different proteins predicted to be secreted were identified in this study (see Additional file 2).