Probable lipid transfer protein (By similarity). Proteoglycan-like factor that exhibits xylogen activity consisting in mediating local and inductive cell-cell interactions required for xylem differentiation (PubMed:15215864, PubMed:21558309). Expressed in a vascular-specific manner, mainly in roots, and, to a lower extent, in hypocotyls, seedlings stems and flowers. Preferentially expressed in vascular tissues such as the central cylinder, cotyledons of mature embryos and steles in seedlings roots (PubMed:21558309). Accumulates also in emerging root primordia (PubMed:21558309). In aerial parts, a weak expression is observed where new xylem tissues are formed, including the vasculature of young leaves, stem nodes and flower tori (PubMed:21558309). No obvious defects in morphology (PubMed:15215864). Plants lacking both XYP1 and XYP2 have morphological defects in vascular development; e.g. discontinuous and thicker veins with the improper interconnection of tracheary elements (TEs) (PubMed:15215864). Has no GPI-anchor. Belongs to the plant LTP family.