Phtheirospermum japonicum, like most hemiparasitic species in the Orobanchaceae, forms multiple haustoria along its roots when it detects a nearby host. In this PNAS Brief Report, we present the discovery of an endogenous peptide, PjCLE1, which stimulates protohaustorium formation when applied externally. This makes the 12-amino acid-long PjCLE1 peptide the first identified peptidic haustorium-inducing factor […]