Involved in pectin biosynthesis. Catalyzes the transfer of xylose from UDP-xylose onto oligogalacturonides and endogenous acceptors. Transfers a xylosyl residue from UDP-D-xylose to a D-galactose residue in xylogalacturonan, forming a beta-1,3-D-xylosyl-D-galactose linkage. Highly expressed in adult leaves. Lower levels in young leaves, stems and roots. Up-regulated by biotic and abiotic stresses and senescence. Down-regulated by cytokinin and nematodes or Agrobacterium infection. Decreased cell wall xylose. Belongs to the glycosyltransferase 47 family. Intron retention.