Extracellular signal peptide that regulates cell fate. May act with TDR as a ligand-receptor pair in a signal transduction pathway that represses tracheary element differentiation but promotes the formation of procambial cells adjacent to phloem cells in the veins. Regulates the transition of protophloem cells from proliferation to differentiation, thus impinging on postembryonic growth capacity of the root meristem; this signaling pathway requires CRN and CLV2 (PubMed:28607033). Interacts specifically with the leucine-rich repeat receptor-like protein kinase TDR, especially in the presence of SERK2. Probably secreted from the phloem cells and distributed in the procambial region. Mostly expressed in flowers and leaves. Widely expressed along the vascular strands. In roots and hypocotyls, present in endodermal cells as well as cells in the phloem and the adjacent pericycle. The O-glycosylation (arabinosylation) of the hydroxyproline Pro-107 enhances binding affinity of the CLE44p peptide for its receptor. Belongs to the CLV3/ESR signal peptide family.