on ligandiks prokambiumi rakkude membraanis paiknevale proteiinikinaasse aktiivsusega retseptorile TDR/PXY (TDIF receptor/phloem intercalated with xylem) harilikus müürloogas, A ligand for the TDR/PXY protein kinase receptors in the procambium cell membranes in Arabidopsis. A signalling pathway originating from the ligand-receptor complex causes the overexpression of WOX4 gene, division of procambium cells and suppresses the division of formed daughter cells into xylemal cells.