Abstract
The vascular system formation in higher plants requires cell-cell communication. Xylogen, an arabinogalactan protein (AGP), was isolated from Zinnia cell culture as a tracheary element differentiation-inducing factor. In the Arabidopsis genome, there are at least 14 xylogen homologs with the signal peptide and the well-conserved nsLTP domain, and occasionally, with AGP-like sequence. Expression analysis using promoter::GUS reporter transgenic plants of these 14 homologues showed that AtXYP2 is expressed preferentially in vascular tissues among these transgenic lines. On the other hand, AtXYP1 and AtXYP2 had xylogen activity. Therefore, AtXYP2 may play a major role as xylogen in Arabidopsis. Since xylogen is predicted to be a GPI-anchored and to be secreted in a directional manner, we analyzed subcellular localization of AtXYP2 in transgenic plants expressing a GFP-translational fusion of AtXYP2. Intracellular localization pattern of AtXYP2-GFP varied through developmental stages. Our data also suggested that AtXYP2 is secreted via the vesicle transport system.
