Abstract
Angiosperm trees bend their secondary xylem by forming tension wood at one side of their stems. The tension wood consists of a cellulose-rich G (gelatinous)-layer in the most inner surface of the cell wall, and generating strong tensile stress. We reported that the poplar G-layer contained xyloglucans, and could incorporate the exogenously supplied xyloglucan into the G-layer enzymatically. To identify proteins involved in G-layer formation, a comprehensive analysis of G-layer-localized proteins were carried out in this study. Poplar G-layers were isolated from the transverse sections of tension wood by ultrasonic treatment. The proteins of isolated G-layers were extracted with urea/detergent solution. The obtained proteins were digested by trypsin, and then peptide mixtures were subjected to LC-MS/MS analysis. From the database search for obtained mass spectrum patterns, we found two cellulose synthases (CesAs) and three xyloglucan endotransglucosylases (XETs) localized in G-layer.
