Extracellular signal peptide that regulates cell fate. Represses tracheary element differentiation but promotes the formation of procambial cells adjacent to phloem cells in the veins. Interacts specifically with the leucine-rich repeat receptor-like protein kinase TDR. The TDIFp peptide contains two hydroxprolines, but hydroxylation had no direct effect on TDIFp activity. The O-glycosylation (arabinosylation) of the hydroxyproline Pro-126 enhances binding affinity of the TDIFp peptide for its receptor. Belongs to the CLV3/ESR signal peptide family.