Signaling peptide involved in the regulation of root colonization by arbuscular mycorrhizal (AM) fungi (PubMed:31477892). Moves from root to shoot to function with the receptor kinase SUNN, in a signaling pathway that repress strigolactone biosynthetic genes and strigolactone content in the roots, and consequently reduces the promotion of further colonization by AM fungi (PubMed:31477892). Expressed in root vasculature. Induced in vasculature of roots colonized with the arbuscular mycorrhizal (AM) fungi Rhizophagus irregularis and Glomus versiforme. The O-glycosylation (arabinosylation) of the hydroxyproline Pro-77 enhances binding affinity of the CLE53p peptide for its receptor. Roots of plants overexpressing CLE53 exhibit normal growth, but reduced levels of colonization by arbuscular mycorrhizal (AM) fungi (PubMed:31477892). Roots of plants silencing CLE53 exhibit normal growth, but reduced levels of colonization by arbuscular mycorrhizal (AM) fungi (PubMed:31477892). Belongs to the CLV3/ESR signal peptide family.