Extraction of proteins from A. thaliana hypocotyls cell walls with boiling SDS and DTT. A – The CW6 pellet described in Figure 5 was used for further extraction of proteins using boiling 4% SDS and 50 mM DTT in 62.5 mM Tris-HCl buffer, pH 6.8. The SDS-DTT extract contained 10 μg of proteins. B – Number of proteins identified in each extract after 1D-GE separation, and analysis by MALDI-TOF MS or LC-MS/MS. Proteins were classified as indicated in legend to Figure 1 (see Additional file 5).